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1
Nicholson, Heather Halcrow. "The New Zealand Greywackes: A study of geological concepts in New Zealand." Thesis, University of Auckland, 2003. http://hdl.handle.net/2292/90.
Full textAbstract:
This thesis traces changes in geological concepts associated with the New Zealand greywackes. Since mineralogists adopted the German mining term 'grauwacke' in the 1780s to refer to a type of old, hard, grey, muddy sandstone, both the name and the rock have caused confusion and controversy. English geologists in the 1830s used the term 'grauwacke' as a rock name and a formation name for their most ancient rocks. The English abandoned the name, but 'greywacke' remained useful in Scotland and began to be used in New Zealand in the 1890s. New Zealanders still refer to the association of semi-metamorphosed greywacke sandstones, argillites, minor lavas, cherts and limestone constituting the North Island ranges and the Southern Alps as 'the greywackes'. With the South Island schists, the greywackes make up 27% of the surface of the New Zealand landmass. They supply much of our road metal, but otherwise have little economic importance. Work on these basement rocks has rarely exceeded 10% of geological research in New Zealand.Leading geologists of the nineteenth and early twentieth centuries competed to construct stratigraphical models for New Zealand where the greywackes were usually classified as of Paleozoic age. Controversy was generated by insufficient data, field mistakes, wrong fossil identifications, attachment to ruling theories and the inability of European-based conventional stratigraphical methodologies to deal with these Carboniferous to Jurassic rocks formed in a very different and unsuspected geological environment. After 1945, growth of the universities, increased Geological Survey activity, and the acquisition of more reliable data led to fresh explanatory ideas about geosynclines, turbidity currents, depositional facies, low-grade metamorphism, and structural geology. New interest in the greywackes resulted in the accumulation of additional knowledge about their paleontology, petrography, sedimentology and structure. Much of this geological data is stored in visual materials including maps, photographs, and diagrams and these are essential today for the interpretation and transfer of information.The development of plate tectonic theory and the accompanying terrane concept in the seventies and eighties permitted real progress in understanding the oceanic origin of greywackes within submarine accretionary prisms and their transport to the New Zealand region. In the last half century comparatively little geological controversy about the greywackes has taken place because of the acquisition of quantities of data, technological improvements, and the use of a dependable theory of the Earth's crust. Scientific controversy takes place when data and/or background theory is inadequate.
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Wadman, Heidi M. "Controls on continental shelf stratigraphy: Waiapu River, New Zealand." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539616896.
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A quantitative understanding of the processes controlling sediment transport and deposition across the land/sea interface is crucial to linking terrestrial and marine environments and understanding the formation of marine stratigraphy. The nature and distribution of terrestrial-derived sediment preserved in shelf stratigraphy in turn provides insight into the complex linkages inherent in source-to-sink sediment dynamics. Located inboard of an actively subducting plate boundary and characterized by one of the highest sediment yields in the world, the open-shelf setting off of the Waiapu River in New Zealand presents an excellent location to improve our understanding of the factors controlling the formation of continental shelf stratigraphy and associated sediment transport. Over 850km of high-resolution seismic and swath bathymetry data ground-truthed by cores show significant stratigraphic spatial variation preserved on the Waiapu continental shelf. This spatial variation is likely controlled by regionally-specific sediment deposition and resuspension processes as well as antecedent geology. Chronostratigraphic control obtained from black carbon analysis reveals that deforestation of the Waiapu catchment is preserved as a distinct event in the adjacent inner shelf stratigraphy, and further indicates that the inner shelf is currently capturing a significant ∼16-34% of the total Waiapu sediment budget. Shelf-wide stratigraphy shows that the thickest deposits of Holocene stratigraphy are found in tectonically-created accommodation spaces, highlighting the role of neotectonics in strata formation. The primary control on strata formation on the Waiapu continental shelf is presumed to be tectonically-steered, local sediment supply, which likely still influences modern-day sediment transport via the effects of small-scale bathymetric lows steering gravity-dependent sediment flows at the river mouth.
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Menzies, Catriona Dorothy. "Fluid flow associated with the Alpine Fault, South Island, New Zealand." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/351800/.
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Rose, Robert Vaughan. "Quaternary geology and stratigraphy of North Westland, South Island, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2011. http://hdl.handle.net/10092/6474.
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Infrared stimulated luminescence ages are presented from the North Westland
region, West Coast, South Island, New Zealand. These ages span much of the
last interglacial-glacial cycle from 123.3 ± 12.7 ka to 33.6 ± 3.6 ka. Coverage
is extended to c. 14 ka via cosmogenic isotope dating.
A new Quaternary stratigraphy and Marine Isotope Stage correlation is
proposed for the on-shore glacial-interglacial fluvioglacial, fluvial and marine
terrace sequence. The new model incorporates previously published
luminescence and radiocarbon ages. It necessitates reinterpretation of the
evolution of the climate in North Westland for the period from 123 ka to 14
ka. Reinterpretation of fossil pollen and plant macrofossil records implies a
period of probable near-interglacial climate in North Westland during the
early to middle portion of Marine Isotope Stage 3. It also implies the
presence in North Westland of raised marine terraces dating from this Isotope
Stage.
In addition it is concluded that during the period from c.60 ka to c.50 ka
podocarp dominated forest was widespread in the lowland portion of
Westland. Between Okarito and Westport Dacrydium cupressinum and
Nestegis were ubiquitous components of this forest. This finding aligns the
Marine Isotope Stage 3 climate of North Westland nicely with that of other
parts of New Zealand where good records exist for this period.
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Dorsey, C. J. "The geology and geochemistry of Akaroa volcano, Banks Peninsula, New Zealand." Thesis, University of Canterbury. Geological Sciences, 1988. http://hdl.handle.net/10092/7524.
Full textAbstract:
This thesis presents a detailed geological, petrological and geochemical study of Akaroa Volcano, Banks Peninsula, New Zealand.
The Akaroa Volcanic Group is defined as comprising all the volcanic products of central, flank and parasitic vent eruptions in the south-eastern two-thirds of Banks Peninsula, which collectively form Akaroa Volcano. Field mapping has shown that the lavas and pyroclastics of which Akaroa Volcano is constructed can be grouped into an Early Phase and a Main Phase.
Early Phase rocks (?11-9 Ma) are restricted in outcrop to the inner shoreline of Akaroa Harbour. The oldest exposed basaltic lava flows of Akaroa Volcano are assigned to Early Phase I. Early Phase II comprises extensive trachyte tuffs, breccias, agglomerates, flows, sills, and a large dome, with minor basaltic tuffs, and appears to represent a major episode of eruption of trachytic lava marking the end of the construction of a proto-Akaroa Volcano. Weathered basaltic flows, tuffs, lahars, scoria cones and pyroclastic breccia of Early Phase III unconformably overlie rocks of Early Phase II. The contact between Early Phases II and III shows considerable relief indicating a period of erosion prior to eruption of Early Phase III flows and pyroclastics. A diverse stratigraphy and a significant portion of the early history of Akaroa Volcano remains buried beneath sea level. A period of prolonged weathering and erosion occurred prior to the eruption of Main Phase lava flows and pyroclastics.
The main cone of Akaroa Volcano is constructed predominantly of hawaiite lava flows and pyroclastics and rare mugearite, benmoreite and trachyte lava flows of the Main Phase, erupted 9-8 Ma. Activity was hawaiian to mildly strombolian in character. Throughout its eruptive history, Akaroa Volcano was intruded by predominantly trachytic dikes of the Akaroa radial dike swarm, and five large trachyte domes. Dikes radiate from a broadly defined central zone south to south-east of Onawe Peninsula which coincides with the inferred location of the main conduit, and with the maxima of local bouguer and isostatic gravity anomalies. Analysis of the gravity anomaly surfaces indicates a substantial sub-surface intrusive complex containing> 615 km³ of intrusive material. Panama Rock trachyte dome can be seen to have been fed by a large dike of the radial dike swarm and a similar origin is inferred for the other intrusive trachyte domes.
Akaroa Volcanic Group lavas have a mineralogy typical of alkaline volcanic associations, dominated by olivine, Ti-rich calcic clinopyroxene, titanomagnetite, plagioclase and apatite. Rare kaersutite megacrysts occur in evolved lavas, and per alkaline differentiates contain arfvedsonite and aenigmatite. Minor biotite and amphibole occur in coarse-grain basic lavas.
Akaroa Volcanic Group lavas comprise a mildly to moderately (sodic) alkaline association, with a trend of moderate iron enrichment. Two end-member lineages are recognised: a dominant basalt-hawaiite-mugearite-benmoreite-trachyte lineage with ne-, hy- and qz-normative variants, and a basanite-nepheline hawaiitenepheline mugearite-nepheline benmoreite-phonolite lineage. Peralkaline differentiates are also recognised. The dominant lava type is hawaiite, rather than basalt, and most lavas have Mg numbers (100 X Mg²⁺ /Mg²⁺ +Fe²⁺) in the range 35-48, indicating that Akaroa Volcanic Group lavas do not represent primary magmas but have undergone significant high pressure fractionation.
Geochemically, Akaroa Volcanic Group lavas form a comagmatic suite characterised by (i) A logarithmic decrease in MgO, TiO₂, Cr, Ni and V; (ii) A linear decrease in CaO and FeO; (iii) A linear increase in Na₂O, K₂O, Y, Nb, Rb, La, Ce, Nd, Ga, Pb, Th, and Ba; (iv) A complex variation in Al₂O₃; (v) A rapid increase in P₂O₅ and Sr followed by a rapid decrease; and (vi) An increase in REE abundances with increasing differentiation. These variations are consistent with evolution by fractional crystallization of olivine, clinopyroxene, titanomagnetite, plagioclase, apatite and possibly kaersutite. Lavas have linear, parallel, LREE-enriched REE patterns (CeN/YbN ≈ 7-9.5) indicative of magma generation by small degrees of partial melting of a garnet peridotite mantle source.
Covariance of ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd isotope ratios is consistent with derivation of Akaroa Volcanic Group magmas from a time-integrated, LREE-depleted mantle source, whereas Sm/Nd and Rb/Sr trace element ratios indicate a LREE-enriched source. Mantle enrichment processes prior to, or associated with, the melting event and/or very small degrees of partial melting (< 1%) are postulated to account for this dichotomy. Qz-normative felsic lavas have high ⁸⁷Sr /⁸⁶Sr isotope ratios, and high-level crustal contamination appears to be an important process in the evolution of these lavas.
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O'Connor, Barry M. "Studies in New Zealand Late Paleogene–Early Neogene Radiolaria." Thesis, University of Auckland, 1996. http://hdl.handle.net/2292/2092.
Full textAbstract:
Radiolaria from Late Eocene to Early Miocene localities in New Zealand are detailed in a series of studies in an attempt to broaden our knowledge of New Zealand Late Paleogene-Early Neogene Radiolaria, and a new technique for investigating Radiolaria is described. Chapter One introduces the studies and the rationale behind each, details the history of radiolarian work in New Zealand, and provides discussion of several points that surfaced during the studies. The points discussed are: radiolarian literature; plate production; scanning electron micrographs versus transmitted light photomicrographs; skeletal terminology; systematic paleontology and the description of new species; radiolarian classification; usefulness of strewn slides. Each study constitutes a published in press, or in review paper and is presented as a chapter. As each chapter is able to stand alone, their abstracts are given below. The reference lists for each paper/chapter have been amalgamated into a master list at the end of the thesis and so do not appear at the end of each chapter: Chapter Two - Seven New Radiolarian Species from the Oligocene of New Zealand Abstract: Seven new radiolarian species from the Oligocene Mahurangi limestone of Northland, New Zealand, are formally described. They are: Dorcadospyris mahurangi (Trissocyclidae), Dictyoprora gibsoni, Siphocampe missilis, Spirocyrtis proboscis (Artostrobiidae), Anthocyrtidium odontatum, Lamprocyclas matakohe (Pterocorythidae), Phormocyrtis vasculum (Theoperidae). Chapter Three – New Radiolaria from the Oligocene and Early Miocene of Northland, New Zealand Abstract: Thirteen new radiolarian species, two new genera and one new combination from the Oligocene and early Miocene of Northland, New Zealand, are formally described - The species are – Heliodiscus tunicatus (Phacodiscidae), Rhopalastrum tritelum (spongodiscidae), Lithomelissa gelasinus, L. maureenae, Lophophaena tekopua (Plagiacanthidae), Valkyria pukapuka (Sethoconidae), Cyrtocapsa osculum, Lophocyrtis (Paralampterium)? inaequalis, Lychnocanium neptunei, Stichocorys negripontensis, Theocorys bianulus, T. perforalvus, T. puriri (Theoperidae); the genera are – Plannapus (Artostrobiidae) and Valkyria (Sethoconidae); the combination is Plannapus microcephalus (Artostrobiidae). Standardised terminology is proposed for internal skeletal elements and external appendages. Emendations are proposed for the family Artostrobiidae and the genera Heliodiscus, Lithomelissa and Cyrtocapsa. Heliodiscus, Cyrtocapsa and Lychnocanium are established as senior synonyms of Astrophacus, Cyrtocapsella and Lychnocanoma respectively. Chapter Four – Early Miocene Radiolaria from Te Kopua Point, Kaipara Harbour, New Zealand Abstract: Radiolaria from the Early Miocene Puriri Formation at Te Kopua Point in the Kaipara area, Northland, New Zealand are documented. Six new species are described - Spongotrochus antoniae (Spongodiscidae), Botryostrobus hollisi, Siphocampe grantmackiei, (Artostrobiidae), Carpocanium rubyae (Carpocaniidae), Anthocyrtidium marieae (Pterocorythidae) and Phormocyrtis alexandrae (Theoperidae). Carpocanium is established as the senior synonym of Carpocanistrum. Chapter Five – Radiolaria from the Oamaru Diatomite, South Island, New Zealand Abstract: Radiolaria from the world-famous Oamaru Diatomite are documented with 24 new species described and three new genera erected The new species are Tricorporisphaera bibula, Zealithapium oamaru (Actionommidae), Plectodiscus runanganus (Porodiscidae), Plannapus hornibrooki, P. mauricei, Spirocyrtis greeni (Artostrobiidae), Botryocella pauciperforata (Cannobotryidae), Carpocanopsis ballisticum (Carpocaniidae), Verutotholus doigi, V. edwardsi, V. mackayi (Neosciadiocapsidae), Lithomelissa lautouri, Velicucullus fragilis (Plagoniidae), Lamprocyclas particollis (Pterocorythidae), Artophormis fluminafauces, Eucyrtidium ventriosum, Eurystomoskevos cauleti, Lophocyrtis (L.) haywardi, Lychnocanium alma, L. waiareka, L. waitaki, Pterosyringium hamata, Sethochytris cavipodis and Thyrsocyrtis (T.?) pingusicoides (Theoperidae). The new genera are Tricorporisphaera, Zealithapium (Actinommidae), and Verutotholus (Neosciadiocapsidae). Emendations are proposed to the family Neosciadiocapsidae and the genus Eurystomoskevos, and Pterosyringium is raised from subgeneric to generic level. Radiolarian faunal composition confirms a Late Eocene age for the Oamaru Diatomite. Chapter Six – Confocal Laser Scanning Microscopy: A New Technique for Investigating and Illustrating Fossil Radiolaria Abstract: Confocal laser scanning microscopy (CLSM), a technique newly applied to the study of fossil Radiolaria, offers the radiolarist clear views of single optical planes of specimens, unhindered by many of the optical effects of conventional light microscopy, while obviating the need to section or break specimens. Resulting images are of a clarity unsurpassed by conventional light microscopy and, as they are saved on computer, are easily viewed, manipulated, enhanced, measured and converted to hard copy. Used in conjunction with common radiolarian study methods CLSM is a powerful tool for gaining additional information with relatively little extra effort. Chapter Seven conveniently summarises taxonomic, stratigraphic and geographic data of all new taxa described, incorporating information gained from the studies and relevant literature. Appendices present the following: data pertaining to all illustrated specimens in this thesis from the University of Auckland Catalogue of Type and Figured Specimens; distribution of Radiolaria at Te Kopua Point; distribution of species and a species list for the Mahurangi Limestone.Chapter 1 is included in 01front, along with pages 38,93, 130 for additional information. Chapter 2 + of the thesis is now published and subject to copyright restrictions.
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Rowan, Christopher James. "Neogene paleomagnetism and geodynamics of the Hikurangi margin, East Coast, New Zealand." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/41330/.
Full textAbstract:
Vertical-axis rotations are an important component of Neogene deformation in the New Zealand plate boundary region, and potentially offer fundamental insights into the rheology of continental crust. Extensive paleomagnetic sampling along the Hikurangi margin, on the East Coast of the North Island, has provided new insights into the patterns, rates and timings of tectonic rotation, and also an improved understanding of the magnetic signature of New Zealand Cenozoic mudstones. Rigorous field tests reveal numerous late remagnetizations, which haveoften formed several million years after deposition and can be irregularly distributed within an outcrop. Scanning electron microscopy and rock magnetic analyses indicate that the remanence carrier is predominantly the ferrimagnetic iron sulphide, greigite, which is present as a mixed population of single domain and superparamagnetic grains that are characteristic of arrested authigenic growth. Strong viscous overprints are the result of later, usually recent, oxidation of these sulphides. The recognition of late-forming magnetizations leads to a completely new view of the Neogene tectonic evolution of the Hikurangi margin, with no tectonic rotations being evident prior to 8–10 Ma; coherent rotation of most of the Hikurangi margin since that time refutes the existence of the independently rotating ‘domains’ that were inferred from earlier paleomagnetic data. This pattern is more consistent with the short-term velocity field, and allows all Neogene rotation to be more simply explained as a large-scale response to realignment of the subducting Pacific plate. Tectonic rotations have been accommodated by a variety of structures since 10 Ma; in the Late Miocene and Pliocene, rates of tectonic rotation were 3–4 times faster than presently observed and possibly involved a much larger region, before initiation of the North Island Dextral Fault Belt and the Taupo Volcanic Zone at 1-2 Ma instigated the current tectonic regime. Collision of the Hikurangi Plateau in the Late Miocene is interpreted to have caused both the initiation of tectonic rotation, and the widespread remagnetization of sediments, making it a key event in the Neogene evolution of the plate boundary region.
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Kniskern, Tara A. "Shelf sediment dispersal mechanisms and deposition on the Waiapu River shelf, New Zealand." W&M ScholarWorks, 2007. https://scholarworks.wm.edu/etd/1539616720.
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The Waiapu River, located on the North Island of New Zealand, drains a small catchment and has one of the highest sediment yields in the world. The river delivers most of its annual sediment load during floods into energetic coastal waters. These conditions are favorable for producing multiple sediment transport mechanisms, including transport in positively and negatively buoyant freshwater plumes, gravitydriven flows, and resuspension. Analyses of Waiapu River shelf seabed data showed that multiple transport mechanisms influence strata formation. Fluvial sediments are initially deposited at water depths shallower than 80 m before being remobilized and deposited at greater water depths. Over the last 100 years fine sediments were retained mainly at water depths between 60 and 190 m, and accounted for 24% of the fluvial load. High shelf accumulation rates (0.2--3.3 cm/yr) were sufficient to preserve pulsed event layers, which were identified by low excess 210Pb and terrestrial delta 13C. Additionally, high subsidence rates on the tectonically active shelf likely influences modern depositional patterns. A three-dimensional numerical model was used to address the mechanisms by which sediment escaped the shelf and to assess the relative importance of the various transport mechanisms. The simulation was able to reproduce time-averaged currents, near-bed sediment concentrations, and bed shear stresses at a tripod deployed off the river mouth at 60 m water depth. Gravity-driven transport was most important on the inner and mid-shelf, whereas dilute transport became more important beyond 65 m depth. Sediments escaped the shelf via dilute suspension to the north of the Waiapu River mouth. Sensitivity experiments showed that transport pathways and depositional patterns were sensitive to floc fraction, waves and currents, and sediment load. Increasing the floc fraction resulted in increased wave-supported gravity-driven transport relative to dilute transport and increased shelf deposition. Coherence between energetic waves and floods increased the importance of wave-supported gravity-flows and shifted initial deposition offshore. Wave-induced bed shear stress increased gravity-driven transport, whereas current-induced bed shear stress increased dilute transport. Deforestation over the last 150 years, which has resulted in an increase annual suspended load, may have resulted in increased shelf sediment retention.
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Bach, Petra. "Garnet-bearing andesites: a case study from Northland, New Zealand." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B29765948.
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Ritchie, Alistair B. H. "Volcanic geology and geochemistry of Waiotapu Ignimbrite, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geological Sciences, 1996. http://hdl.handle.net/10092/6588.
Full textAbstract:
Waiotapu Ignimbrite (0.710 ± 0.06 Ma) is a predominantly densely welded, purple-grey coloured, pumice rich lenticulite, which is exposed on both eastern and western flanks of Taupo Volcanic Zone. The unit is uniform in terms of lithology and mineralogy over its entire extent and has been deposited as a single flow unit. The unit contains abundant pumice clasts which are often highly attenuated (aspect ratios of c.1 :30) and are evenly distributed throughout the deposit. Lithic fragments are rare, never exceeding 1% of total rock volume at an outcrop and no proximal facies, such as lithic lag breccias, have been identified.
The deposit is densely welded to the base and only in more distal exposure does the ignimbrite become partially welded at the top of the deposit. Post-depositional devitrification is pervasive throughout the deposit, often destroying original vitroclastic texture in the matrix. Vapour phase alteration is extensive in welded and partially welded facies of the deposit.
Pumices within Waiotapu Ignimbrite appear to have been derived from two distinct magma batches, with differing Rb concentrations, that originated along different fractionation trends. Type-A pumices have significantly lower Rb than the subordinate type-B pumices. The presence of the pumices may represent the simultaneous evisceration of two spatially discrete magma chambers or the type-B chamber may have been intruded into type-A body, the magmas subsequently mingling prior to, or during, the eruption.
The source of Waiotapu Ignimbrite is poorly constrained, largely owing to the lack of meaningful maximum lithic data, and poor exposure of the unit. The distribution of the ignimbrite suggests that it was erupted from within Kapenga volcanic centre. If so the most proximal exposures of Waiotapu Ignimbrite are approximately 10km from the vent. Intensive and voluminous silicic volcanism, beginning with the eruption of the 0.33 Ma Whakamaru Group Ignimbrite eruptions, and extensive faulting within Kapenga volcanic centre will have obscured any intra-caldera Waiotapu Ignimbrite. The mechanism of eruption suggests that the source may not have been a caldera in the strictest sense, but instead a series of near linear fissures aligned with the trend of regional faulting.
Waiotapu Ignimbrite was generated in one sustained eruption and produced an energetic and high temperature pyroclastic flow. The lack of any recognised preceding plinian deposit, coupled with the energetic nature and paucity of lithics suggests eruption by an unusual mechanism. The eruption most likely resulted from the large scale collapse of a caldera block into the underlying chamber resulting in high discharge rates, which were no conducive to the development of a convecting column, and minimal vent erosion, resulting in negligible entrainment of lithics.
The density of welding and recrystallisation textures suggest that the flow retained heat to considerable distances which allowed the ignimbrite to weld densely to the base. The deposit was most likely progressively aggraded from the base, with material being supplied from an overriding particulate flow.
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Bever, Aaron J. "Integrating space-and time-scales of sediment-transport for Poverty Bay, New Zealand." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539616566.
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Poverty Bay is a small embayment located in the middle of the Waipaoa River Sedimentary Dispersal System (WSS) on the eastern coast of the north island of New Zealand. Within this dispersal system, a large multidisciplinary study was focused on determining the sediment routing from the source within the headwaters to the locations of sediment accumulation on the continental shelf and slope. Poverty Bay acts as the land to sea transition area in the WSS, and as such significantly modifies the fluvial sedimentary signal before it is exported to the continental shelf. Until this study, little hydrodynamic or sediment-transport work had been conducted in Poverty Bay, however. This dissertation analyzed observation and numerical model results to characterize the hydrodynamics and sediment-transport within Poverty Bay. Three S4 current meters with pressure and temperature/salinity sensors, one upward looking ADCP, and one downward looking ADV were deployed in Poverty Bay for April--September, 2006. Hydrodynamics, sediment-transport, and waves were modeled using the Regional Ocean Modeling System (ROMS) fully coupled to the Simulated WAves Nearshore (SWAN) model. The 2006 winter wet season was modeled to overlap with the field observations, along with a ∼40 yr recurrence interval storm that occurred from 21--23 October, 2005. For these two meteorological conditions, four different model grid and sediment load configurations were modeled; (1) the modern Poverty Bay with the modern sediment load, (2) the modern Poverty Bay with the pre-anthropogenic (PA) sediment load, (3) the 2 kya Poverty Bay with the PA sediment load, and (4) the 7 kya Poverty Bay with the PA sediment load. Both the observation and modeling results showed significant quantities of fine sediment were ephemerally deposited within the shallow Poverty Bay during times of elevated river discharge and energetic waves and currents. The deposition of sediment within Poverty Bay during floods followed by the resuspension and export to the continental shelf during subsequent wave events created multiple pulses of sediment out of Poverty Bay. as the sediment underwent multiple resuspension episodes, the sedimentary signal initially supplied by the river, such as the timing of supply to the shelf and the grain size distribution, would be altered. Shoreward nearshore currents and a divergence in the currents seaward of the Waipaoa River mouth provided mechanisms for the segregation of the sand from the muddy sediment, with the coarse sediment preferentially moved shoreward and the fine sediment exported from Poverty Bay to deeper water. Model results also showed significant differences between the sedimentary signals supplied to the continental shelf based on the dispersal basin geometry and river mouth orientation. The model estimates showed that marine dispersal can influence the long-term trends of a slowing shoreline progradation rate and coarsening upward sequences on the continental shelf, without invoking climate change or changes to the sediment supply. This implies that the processes controlling marine and nearshore sediment dispersal must be considered when developing hypothesis based on sedimentological observations.
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Miller, andrea J. "A Modern Sediment Budget for the Continental Shelf off the Waipaoa River, New Zealand." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539617880.
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Daczko, Nathan Robert. "The Structural and Metamorphic evolution of cretaceous high-P granulites, Fiordland, New Zealand." University of Sydney. Geosciences, 2002. http://hdl.handle.net/2123/822.
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Fiordland is located southwest of South Island of New Zealand. The field area of this thesis is in northern Fiordland, at the boundary of pristine arc rocks (Median Tectonic Zone) and a belt of Paleozoic paragneisses and orthogneisses of variable age that represent the metamorphosed paleo-Pacific Gondwana margin.
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Blatchford, Hannah Jane. "The Structural Evolution Of A Portion Of The Median Batholith And Its Host Rock In Central Fiordland, New Zealand: Examples Of Partitioned Transpression And Structural Reactivation." ScholarWorks @ UVM, 2016. https://scholarworks.uvm.edu/graddis/635.
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This thesis presents the results of structural analyses and detailed field mapping from a region near Adams Burn in central Fiordland, New Zealand. The region preserves assemblages of metasedimentary and metaigneous rocks deposited, intruded, and ultimately metamorphosed and deformed during the growth of a Gondwana-margin continental arc from Cambrian-Early Cretaceous. Evidence of arc growth is preserved in the Late Devonian-Early Cretaceous Median Batholith, a belt of intrusive rock whose growth culminated with the emplacement of the Western Fiordland Orthogneiss (WFO) into the middle-lower crust of the margin. Following this magmatic flare-up, the margin experienced Late Cretaceous extensional orogenic collapse and rifting. During the Late Tertiary, the margin records oblique convergence that preceded the Alpine fault. The history of arc growth and record of changing tectonic and deformational regimes makes the area ideal for study of structural reactivation during multiple cycles of magmatism, metamorphism and deformation, including during a mid-lower crust magma flare-up.
Structural and lithologic mapping, structural analyses, and cross-cutting relationships between superposed structures and three intrusions were used to bracket the relative timing of four tectonic events (D1-D4), spanning the Paleozoic to the Tertiary. The oldest event (D1) created a composite fabric in the metasedimentary and metaigneous rocks of the Irene Complex and Jaquiery granitoid gneiss prior to emplacement of the Carboniferous Cozette pluton. S1 foliation development, set the stage for structural reactivation during the second phase of deformation (D2), where S1 was folded and reactivated via intra-arc shearing. These second-phase structures were coeval with the emplacement of the Misty pluton, (part of WFO in central Fiordland), and record crustal thickening and deformation involving a kinematically partitioned style of transpression. Arc-normal displacements were localized into the rocks of the Irene Complex. Oblique displacements were localized along the Misty-Cozette plutonic contact, forming a ≥1 km-wide, upper amphibolite-facies gneissic shear zone that records sinistral-reverse offset. Second-phase structures are cross-cut by widespread leucocratic pegmatite dikes. S2 in the Cozette and Misty plutons is reactivated by localized, ≤10 m-thick, greenschist-facies (ultra)mylonitic shear zones that record sinistral-normal offsets. S3/L3 shear zones and lithologic contacts were then reactivated by two episodes of Tertiary, fourth-phase faulting compatible with Alpine faulting, everywhere truncating the pegmatite dikes. Early faults accommodated shortening normal to the Alpine fault, and were obliquely reactivated by a younger population of faults during dextral transpression.
My results show that structural reactivation occurred repeatedly after D1, and that structural inheritance played a key role in the geometry, distribution, and kinematics of younger deformation events throughout the arc's history. The sheeted emplacement of the Misty pluton was accompanied, and possibly facilitated, by a system of partitioned transpression during Early Cretaceous crustal thickening and arc magmatism. These results show that transpression helped accommodate and move magma through the middle and lower crust during the flare-up. This conclusion is important for the study of continental arcs globally, as evidence of deformation during high-flux magmatism at lower crustal depths (~40 km) is rarely preserved and exhumed to the surface.
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Whattam, Scott A. "Evolution of the Northland ophiolite, New Zealand: geochemical, geochronological and palaeomagneticconstraints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244890.
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Luke, Jason Allen. "Three-Dimensional Seismic Study of Pluton Emplacement, Offshore Northwestern New Zealand." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/2949.
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Detailed 3D seismic images of a volcano-plutonic complex offshore northwestern New Zealand indicate the intrusive complex lies in a relay zone between NE-trending en echelon normal faults. A series of high angle normal faults fan out from the margin of the Southern Intrusive Complex and cut the folded strata along the margin. These faults terminate against the margins of the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with regional faults that are part of the Northern Taranaki Graben. Offset along these faults is on the order of 10s to over 100 meters. Strata on top of the complex are thinned and deformed into a faulted dome with an amplitude of about 0.7 km. Steep dip-slip faults form a semi-radial pattern in the roof rocks, but are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the Northern Taranaki Graben. The longest roof faults are about the same length as the diameter of the pluton and cut through approximately 0.7 km of overlying strata. Fault offset gradually diminishes vertically away from the top of the intrusion. The Southern Intrusive Complex is a composite intrusion and formed from multiple steep-sided intrusions as evidenced by the complex margins and multiple apophyses. Small sills are apparent along the margins and near the roof of the Southern complex. Multiple episodes of deformation are also indicated by a series of unconformities in the sedimentary strata around the complex. Two large igneous bodies make up the composite intrusion as evidenced by the GeoAnomaly body detection tool. The Southern Intrusive Complex has a resolvable volume of 277 km3. Room for the complex was made by multiple space-making mechanisms. Roof uplift created ~3% of the space needed. Compaction/porosity loss is estimated to have contributed 20-40% of the space needed. Assimilation may have created ~0-30% space. Extension played a major role in creating the space needed and is estimated to have created a minimum of 33% of the space. Floor subsidence and stoping may have occurred, but are not resolvable in the seismic survey.
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Rother, Henrik. "Late Pleistocene Glacial Geology of the Hope-Waiau Valley System in North Canterbury, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2006. http://hdl.handle.net/10092/1298.
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This thesis presents stratigraphic, sedimentological and geochronological results from valley fill and glacial moraines of the Hope-Waiau Valleys in North Canterbury, New Zealand. The findings demonstrate that a substantial portion of the modern valley fill comprises in-situ sedimentary sequences that were deposited during the penultimate glaciation (OIS 6), the last interglacial (OIS 5) and during the mid-late last glacial cycle (OIS 3/2). The sediments survived at low elevations in the valley floor despite overriding by later glacial advances. Sedimentologically, the fill indicates deposition in an ice marginal zone and consists of paraglacial/distal-proglacial aggradation gravels and ice-proximal/marginal-subglacial sediments. Deposition during glacial advance phases was characterized by the sedimentation of outwash gravels and small push moraines while glacial retreat phases are dominated by glaciolacustrine deposits which are frequently interbedded with debris flow diamictons. The overall depositional arrangement indicates that glacial retreat from the lower valley portion occurred via large scale ice stagnation. Results from infra-red stimulated luminescence (IRSL) dating gives evidence for five large aggradation and degradation phases in the Hope-Waiau Valleys over the last 200 ka. Combined with surface exposure dating (SED) of moraines the geochronological results indicate that glacial advances during OIS 6 were substantially larger in both ice extent and ice volume than during OIS 4-2. The last glacial maximum (LGM) ice advance occurred prior to 20.5 ka and glacial retreat from extended ice positions began by ~18 ka BP. A late glacial re-advance (Lewis Pass advance) occurred at ~13 ka BP and is probably associated with a regional cooling event correlated to the Antarctic Cold Reversal (ACR). The findings from the Hope-Waiau Valleys were integrated into a model for glaciations in the Southern Alps which uses data from a snow mass balance model to analyse the sensitivity of glacial accumulation to temperature forcing. Model results indicate that in the central hyperhumid sector of the Southern Alps ice would expand rapidly with minor cooling (2-4℃) suggesting that full glaciation could be generated with little thermal forcing. Some Quaternary glacial advances in the Southern Alps may have been triggered by regional climate phenomena (e.g. changes in ENSO mode) rather than requiring a thermal trigger from the Northern Hemisphere.
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Waight, Tod Earle. "The geology and geochemistry of the Hohonu Batholith and adjacent rocks, North Westland, New Zealand." Thesis, University of Canterbury. Geology, 1995. http://hdl.handle.net/10092/5615.
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The Hohonu Batholith lies within the Buller terrane, immediately adjacent to the Alpine Fault and inland from Hokitika and Greymouth on the West Coast of the South Island of New Zealand. Detailed mapping has identified ten distinct granitoids intruded into Greenland Group metasediments. Four geochemical suites are recognized within the Hohonu Batholith.
Palaeozoic magmatism in the batholith is represented by the Summit Granite, which yields a Palaeozoic (381.2 Ma) age and displays affinites with granitoids of the Karamea Suite of Tulloch (1988a). The informal name Summit Granite suite is used to describe this pluton. The Summit Granite has acted as country rock and is intruded by two Cretaceous plutons. The poorly constrained Mount Graham Granite may also belong within the Summit Granite suite.
The Hohonu Batholith is dominated by the mid-Cretaceous (114-109 Ma) I-type Hohonu Super-suite, which is considered to encompass the previously defined Rahu Suite of Tulloch (1988a). The Hohonu Super-suite is characterized by relatively restricted radiogenic isotopic compositions with Sr(110) = 0.7062 to 0.7085 and εNd(110) = -4.4 to -6.1, and represents melting of a complex source combining depleted mantle-derived material, similar in composition to the source of the Early Cretaceous Separation Point Suite, and a complex, heterogeneous and largely unconstrained lower continental crustal component. A model is proposed whereby the Hohonu Super-suite was generated following the collapse and thinning of Western Province crust previously over thickened by the generation of the Median Tectonic Zone volcanic arc and its subsequent collision with the Western Province. Collapse of the over thickened crust is believed to be a consequence of the cessation of subduction along the Pacific Margin of the New Zealand portion of Gondwana and the subsequent removal of compressional forces maintaining crustal thickening. Rapid isothermal uplift of the thickened crustal root resulted in partial melting of the lower crust. Ambient temperatures in the lower crust were also raised by mafic underplating associated with isothermal uplift and adiabatic melting of the underlying mantle. Emplacement of the Hohonu Super-suite in an extensional environment is indicated by the intimate relationship between the Rahu Suite Buckland Granite and the Paparoa Metamorphic Core Complex, and the development of the extensional sedimentary basins of the Pororari Group. This extensional event is considered to predate and be unrelated to the separation of Australia and New Zealand and opening of the Tasman Sea.
Two suites are recognized within the Hohonu Super-suite in the Hohonu Batholith; the Te Kinga Suite and the Deutgam Suite. Geochemical contrasts between these two suites are attributed to melting at differing crustal depths, at varying water activities, and in equilibrium with different residual assemblages. The relatively mafic, meta1uminous, I-type compositions of the Deutgam Suite are ascribed to dehydration melting in equilibrium with an amphibolitic (plagioclase + amphibole) residue. Residual plagioclase retains Sr, Al2O3, Na2O and Eu and results in the low concentrations of these elements which characterize this suite. In contrast, the peraluminous high silica compositions of the Te Kinga Suite are attributed to water-saturated to under saturated melting in equilibrium with an eclogitic (garnet + amphibole residue) at greater depths in the crust. Residual garnet produces the HREE-depleted nature of the suite, and a lack of residual plagioclase contributes to the characteristically higher Sr, Al2O3, Na2O and Eu contents of the Te Kinga Suite.
Late Cretaceous magmatism in the Hohonu Batholith is represented by the French Creek Suite. This suite comprises the composite French Creek Granite, which displays geochemical and petrographic features typical of A-type granitoids, and associated hypabyssal rhyolite dikes. The alkaline magmatism of the French Creek Suite and the closely associated Hohonu Dike Swarm are intimately linked to extension during the opening of the Tasman Sea. The Hohonu Dike Swarm consists of predominately doleritic dikes, with subordinate camptonites and rare phonolites, concentrated on the Hohonu Ranges and Mount Te Kinga. Field evidence indicates that the Hohonu Dike Swarm and French Creek Granite are, at least partially, contemporaneous. The age of this activity is constrained by an 81.7 Ma SHRIMP age for French Creek Granite and is contemporaneous with the generation of the first oceanic crust in the Tasman Sea. A strong WNW-ESE trend within the Hohonu Dike Swarm parallels the line of Australia New Zealand break-up, and the alkaline compositions of both the dikes and the French Creek Granite are characteristic of emplacement into an anorogenic extensional environment. Consequently strong links are indicated between the opening of the Tasman Sea and genesis of the Hohonu Dike Swarm and French Creek Granite. Geochemical data are consistent with generation of French Creek Granite by prolonged fractionation of plagioclase and mafic phases from saturated and oversaturated members of the Hohonu Dike Swarm. Approximately 20% crustal contamination is also required to produce the isotopic compositions of French Creek Granite from the relatively depleted compositions of the Hohonu Dike Swarm.
Amphibolite-facies paragneisses, orthogneisses and metabasites of the Granite Hill Complex can be confidently correlated with similar rocks of the Fraser Complex. The dominance of metabasaltic rocks, distinct isotopic compositions and preliminary zircon inheritance studies indicate these gneisses are unlikely to represent metamorphic equivalents of the Greenland Group and intrusive granitoids as proposed for the Charleston Metamorphic Complex. Possible correlatives of the Fraser and Granite Hill Complexes may occur in Fiordland.
Poorly exposed Tertiary rocks along the north-west margin of the Hohonu Ranges are briefly described. These rocks are considered to represent material incorporated in a major fault zone along which the batholith has been uplifted and exposed during recent compression across the Alpine Fault.
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Payne, Danielle Sarah. "Shelf-to-slope sedimentation on the north Kaipara continental margin, northwestern North Island, New Zealand." The University of Waikato, 2008. http://hdl.handle.net/10289/2413.
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Temperate mixed carbonate-siliciclastic sediments and authigenic minerals are the current surficial deposits at shelf and slope depths (30-1015 m water depth) on the north Kaipara continental margin (NKCM) in northern New Zealand. This is the first detailed study of these NKCM deposits which are described and mapped from the analysis of 54 surficial sediment samples collected along seven shorenormal transects and from three short piston cores. Five surficial sediment facies are defined from the textural and compositional characteristics of this sediment involving relict, modern or mixed relict-modern components. Facies 1 (siliciclastic sand) forms a modern sand prism that extends out to outer shelf depths and contains three subfacies. Subfacies 1a (quartzofeldspathic sand) is an extensive North Island volcanic and basement rock derived sand deposit that occurs at less than 100-200 m water depth across the entire NKCM. Subfacies 1b (heavy mineral sand) occurs at less than 50 m water depth along only two transects and consists of predominantly local basaltic to basaltic andesite derived heavy mineral rich (gt30%) deposits. Subfacies 1c (mica rich sand) occurs at one sample site at 300 m water depth and contains 20-30% mica grains, probably sourced from South Island schists and granites. Facies 2 (glauconitic sand) comprises medium to fine sand with over 30% and up to 95% authigenic glauconite grains occurring in areas of low sedimentation on the outer shelf and upper slope (150-400 m water depth) in central NKCM. Facies 3 (mixed bryozoan-siliciclastic sand) consists of greater than 40% bryozoan skeletal material and occurs only in the northern half of the NKCM. Facies 4 (pelletal mud) occurs on the mid shelf (100-150 m water depth) in northern NKCM and comprises muddy sediment dominated by greater than c. 30% mixed carbonatesiliciclastic pellets. Facies 5 (foraminiferal mud and sand) contains at least 30% foraminifera tests and comprises two subfacies. Subfacies 5a consists of at least 50% mud sized sediment and occurs at gt400 m water depth in southern NKCM while subfacies 5b comprises gt70% sand sized sediment and occurs at mid to outer shelf and slope depths in the northern NKCM. vi A number of environmental controls affect the composition and distribution of NKCM sediments and these include: (1) variable sediment inputs to the NKCM dominated by inshore bedload sources from the south; (2) northerly directed nearshore littoral and combined storm-current sediment transport on the beach and shelf, respectively; (3) offshore suspended sediment bypassing allowing deposition of authigenic minerals and skeletal grains; (4) exchange between the beach and shelf producing similar compositions and grain sizes at less than 150 m water depth; and (5) the episodic rise of sea level since the Last Glaciation maximum approximately 20 000 years ago which has resulted in much sediment being left stranded at greater depths than would otherwise be anticipated. Sedimentation models developed from other wave-dominated shelves generally do not appear to apply to the NKCM sediments due to their overall relative coarseness and their mosaic textural characteristics. In particular, the NKCM sediments do not show the expected fining offshore trends of most wavedominated shelf models. Consequently, sandy sediments (both siliciclastic and authigenic) are most typical with mud becoming a dominant component in southern NKCM sediments only at greater than 400 m water depth, over 350 m deeper than most models suggest, a situation accentuated by the very low mud sediment supply to the NKCM from the bordering Northland landmass.
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Hollis, C. J. "Latest Cretaceous to late Paleocene Radiolaria from Marlborough (New Zealand) and DSDP site 208." Thesis, University of Auckland, 1991. http://hdl.handle.net/2292/2031.
Full textAbstract:
This is the first study of cretaceous or Paleogene Radiolaria from on-land New Zealand. It is based on five Late Cretaceous to Paleocene sections within the Amuri Limestone Group of eastern Marlborough (NE South Island): Woodside Creek, Wharanui Point, Chancet Rocks, Flaxbourne River and Mead Stream. Faunas from coeval sediments at DSDP Site 208 (Lord Howe Rise, north Tasman Sea) are also reexamined. Because diverse and well-preserved radiolarian faunas are common, the location of the Cretaceous/Tertiary (K/T) boundary well-documented, and the earliest Paleocene relatively complete, these sections provide the most complete known record of radiolarian evolution from latest Cretaceous to mid Late Paleocene (c.70-60 Ma). Systematic treatment of K-T transitional faunas was hampered by a dichotomy between Cenozoic and Mesozoic methodologies and nomenclature. To resolve this schism, broad taxonomic definitions are adopted, numerous synonymies are identified, and several revised definitions are proposed for established taxa. Of the 94 taxa recorded, 65 are species or species groups, and 29 are undifferentiated genera or higher level categories. Three new species are described: Amphisphaera aotea n.sp., A. kina n.sp. and Stichomitra wero n.sp. A new latest Cretaceous to mid Late Paleocene zonation is proposed. Six new interval zones are defined by the first appearances of the nominated species. In ascending order these are: Lithomelissa? hoplites (RK9, Cretaceous), Amphisphaera aotea (RP1, Paleocene), A. kina (RP2), Stichomitra granulata (RP3), Buryella foremanae (RP4) and B. tetradica (RP5) Interval Zones. The Late Paleocene Bekoma campechensis Zone of Nishimura (1987) succeeds RP5 at Mead Stream. The K/T boundary does not mark an extinction event for radiolarians, but does coincide with a sudden change from nassellarian to spumellarian dominance. It also coincides with a sudden influx of diatoms in Marlborough, where a fall in sea level appears to have promoted upwelling. Thus, rather than marking a catastrophe, the K/T boundary heralded a period (from RP1 to lower RP3) of great productivity for siliceous plankton. With a return to conditions similar to those of the Cretaceous, later in the Paleocene (upper RP3-RP6), Cretaceous survivors were rapidly replaced by new Tertiary taxa in deep-water settings. However, in shallower settings, many Cretaceous taxa remained abundant throughout the Early Paleocene. Faunal changes at site 208 are similar to those of the deep-water Marlborough sections, but without clear evidence for increased fertilty in the earliest Paleocene.
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Scott, John G., and n/a. "Structural controls on gold - quartz vein mineralisation in the Otago schist, New Zealand." University of Otago. Department of Geology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070412.160816.
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Hydrothermal fluid flow is spatially and genetically associated with deformation in the earth�s crust. In the Otago Schist, New Zealand, the circulation of hydrothermal fluids in the Cretaceous formed numerous mesothermal gold-quartz vein deposits. Otago schist rocks are largely L-S tectonites in which the penetrative fabric is the product of more than one deformation phase/transposition cycle. Regional correlation of deformation events allowed mineralised deposits to be related to the structural evolution of the Otago Schist. Compilation of a detailed tectonostratigraphy of New Zealand basement rocks reveals that extensional mineralisation correlates with the onset of localised terrestrial fanglomerate deposition, thermal perturbation and granitic intrusion that mark the beginning of New Zealand rifting from the Antarctic portion of Gondwana.
Laminated and breccia textures in mineralised veins suggest that host structures have experienced repeated episodes of incremental slip and hydrothermal fluid flow. However, analysis of vein orientation data in terms of fault reactivation theory (Amontons Law) shows that most deposits contain veins that are unfavourably oriented for frictional reactivation. Repeated movement on unfavourably oriented structures may involve dynamic processes of strain refraction due to competency contrasts, the effect of anisotropy in the schist, or localised stress field rotation.
Deposits have been classified on the basis of host structure kinematics at the time of mineralisation into low angle thrust faults, and high angle extensional fault - fracture arrays. Low angle deposits have a mapped internal geometry that is very different from conventional imbricate thrust systems. This study applied ⁴⁰Ar/�⁹Ar geochronology to selected deposits and has identified at least three distinct mineralisation events have occurred within the central axial belt during the Cretaceous. Relationships between radiometric apparent age and inferred crustal depth reveal that after metamorphism, the onset of cooling and rapid exhumation of the schist belt coincides temporally and spatially with the age of mineralisation and structural position of a regional scale low angle shear zone in Otago.
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Powell, Nicholas Garth, and n/a. "The geology of central southern Fiordland : with emphasis on the cause of polybaric Cretaceous metamorphism in western New Zealand." University of Otago. Department of Geology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070424.121136.
Full textAbstract:
Central southern Fiordland, New Zealand, is underlain extensively by metasediments and associated metavolcanics. These are mapped in three lithostratigraphic units, from west to east Edgecumbe Group, Cameron Group and Cumbrae Supergroup. Lower Cameron Group units lithocorrelate with Central Fiordland Belt lithological associations and with those of Fraser Complex, Westland.
Eastern Fiordland Belt metavolcanics and lacustrine metasediments are tectonostratigraphically unrelated to Cameron Group, from which they are separated by the Grebe Fault. They instead have affiliations with the Loch Burn Formation, Largs Volcanics, Drumduan Group and Paterson Group. These units (collectively, "Cumbrae Supergroup") represent remnants of a Triassic-Jurassic calc-alkaline arc.
Six deformational episodes are identified in central southern Fiordland. The earliest, D₁, is obliterated by D₂ and M₂ metamorphism. D₃ is restricted to the Southwest Fiordland Block. D₄ occupied a brief interval of M₃ time. D₄ of the Central and Western Fiordland Belts corresponds to earliest deformation in Eastern Fiordland Belt metavolcanics. The Grebe Fault is a left-lateral reverse D₄ fault; now vertical, it previously dipped eastward. The Dusky Fault, a reactivated D₅ left-lateral transfer structure, accommodated the dip-slip component of displacement at low-angle normal faults during mid-Cretaceous extension. Open folds represent D₆. Post-glacial scarps mark the post-D₆ Kilcoy and Vincent Faults. Their merged northward continuation is intersected by the tailrace tunnel of the Manapouri Hydroelectric Power Station.
Southwest Fiordland Block pelites were metamorphosed at 665 �C, c. 3 kbar during M₂. Early M₃ is of contact metamorphic aspect. Late M₃ is distinctively polybaric: Central Fiordland Belt kyanite-garnet pelites recrystallised at c. 8.5 kbar after metamorphism in the sillimanite field at c. 3.5 kbar. Western Fiordland Orthogneiss 12 kbar granulite assemblages formed during late M₃. South of the Dusky Fault, late M₃ is almost asymptomatic. The M₃ field gradient is continuous across the Grebe Fault: in the Eastern Fiordland Belt, late M₃ staurolite and garnet supersede chloritoid in lacustrine (meta-)sapropel-silts.
The Grebe Fault is an important tectonostratigraphic break; it may separate New Zealand�s Western and Eastern Provinces. Its relationship to any "Median Tectonic Zone" is unclear, as no such zone has been found in southeastern Fiordland. Cumbrae Supergroup rocks within the "Median Tectonic Zone" represent the arc that nourished the Eastern Province�s Barretts Formation, Murihiku Supergroup and Stephens Subgroup. The Cumbrae arc was �obducted� westwards during Early Cretaceous continent-arc collision. This event simultaneously halted Eastern Province volcanogenic sedimentation and tectonically buried Fiordland, imposing late M₃ pressure increments. Drumduan Group lawsonite is coeval.
Cretaceous collision induced glaciation. Late Cretaceous climatic deterioration and extensional tectonism caused icecap development. The Otago "Peneplain" is a Late Cretaceous subglacial floor. Accumulation of voluminous perennial Cretaceous ice on Earth has hitherto not been inferred.
Facultative psychrophily in New Zealand�s ancient endemics and their preference for dark conditions reflect passage through a hitherto-unsuspected evolutionary bottleneck: prolonged winter darkness and harsh climate of near-polar Late Cretaceous New Zealand exerted extraordinary evolutive pressures on ancestral forms after biotic links with Gondwana were severed. New Zealand�s ancient endemics are the evolutionary derivatives of a Late Cretaceous near-polar fauna.
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Claridge, Jonathan William Roy. "Patterns of Crustal Deformation Resulting from the 2010 Earthquake Sequence in Christchurch, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2012. http://hdl.handle.net/10092/7910.
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The Mw 7.1 Darfield earthquake generated a ~30 km long surface rupture on the Greendale Fault and significant surface deformation related to related blind faults on a previously unrecognized fault system beneath the Canterbury Plains. This earthquake provided the opportunity for research into the patterns and mechanisms of co-seismic and post-seismic crustal deformation. In this thesis I use multiple across-fault EDM surveys, logic trees, surface investigations and deformation feature mapping, seismic reflection surveying, and survey mark (cadastral) re-occupation using GPS to quantify surface displacements at a variety of temporal and spatial scales. My field mapping investigations identified shaking and crustal displacement-induced surface deformation features south and southwest of Christchurch and in the vicinity of the projected surface traces of the Hororata Blind and Charing Cross Faults. The data are consistent with the high peak ground accelerations and broad surface warping due to underlying reverse faulting on the Hororata Blind Fault and Charing Cross Fault. I measured varying amounts of post-seismic displacement at four of five locations that crossed the Greendale Fault. None of the data showed evidence for localized dextral creep on the Greendale Fault surface trace, consistent with other studies showing only minimal regional post-seismic deformation. Instead, the post-seismic deformation field suggests an apparent westward translation of northern parts of the across-fault surveys relative to the southern parts of the surveys that I attribute to post-mainshock creep on blind thrusts and/or other unidentified structures. The seismic surveys identified a deformation zone in the gravels that we attribute to the Hororata Blind Fault but the Charing Cross fault was not able to be identified on the survey. Cadastral re-surveys indicate a deformation field consistent with previously published geodetic data. We use this deformation with regional strain rates to estimate earthquake recurrence intervals of ~7000 to > 14,000 yrs on the Hororata Blind and Charing Cross Faults.
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Bujard, Jade P. "Geophysical Analysis of the Miocene-Pliocene Mangaa Formation for Better Exploration within the Parihaka 3D Survey; Taranaki Basin, New Zealand." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10244630.
Full textAbstract:
The Taranaki Basin is the only known producing basin within New Zealand. Since the drilling of the first well in 1865, the Taranaki basin has remained relatively underexplored. The Arawa-1 well was drilled in 1992 using 2D seismic lines as a control. New Zealand has started an exploration initiative by publicly releasing all geological and geophysical information gathered on and offshore New Zealand. The gathered information includes the Parihaka 3D survey, which directly overlaps with the Arawa-1 well and original 2D lines. This study focused on the Miocene-Pliocene Mangaa Formation, which exhibited reservoir quality within the Arawa-1 well. Seismic attributes have been used to locate an area of interest within the Mangaa Formation. A Coherence attribute was useful for identifying geomorphological features as well as faults. An average energy volume was used to emphasize brighter amplitudes from background signatures and to define lateral boundaries of the reservoir. Upon mapping an area of interest within the Mangaa Formation, the amplitude anomalies were conformable to structural highs. Results were compared to an analog well, Karewa-1, where amplitude anomalies were relatively identical. Amplitude versus offset analysis was conducted for the amplitude anomaly within the Mangaa Formation and found a class 4 anomaly. The interpreter performed fluid replacement modeling with the assumption of 100% gas, derived from the analog, Karewa-1. The interpreter compared the resulting model to the observed trends inside and outside of the amplitude anomaly. The gas model signature resembled that of the amplitudes inside of the amplitude anomaly, and the amplitude signature of the original water saturation resembled that of the amplitudes outside of the anomaly. The results allow the interpreter to use the correlation of amplitude signatures and fluids in place to assist in de-risking prospect potential.
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Bainbridge, Rupert. "Lost landslides : rock-avalanche occurrence and fluvial censoring processes on South Island, New Zealand." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/32621/.
Full textAbstract:
Rock-avalanches (RAs) are a large (typically > 106 m3) and extremely rapid (30 - >100 m/s) type of landslide. RAs pose a significant hazard as they can runout over long distances and generate secondary hazards such as tsunami and unstable, cross-valley dams. Previous research on the distribution of rock-avalanche deposits (RADs) on the South Island, New Zealand has suggested that there are fewer deposits than would be expected for a seismically active, high-mountain region. This is due to their removal from the sedimentary record (censoring) by fluvial erosion, glacial entrainment, vegetation cover, sub-aqueous occlusion and deposit misidentification. Censoring of deposits skews magnitude-frequency relationships of RA occurrence and hinders hazard planning. This research examines processes acting to fluvially censor RADs on the South Island. 268 known, and 47 possible RADs were identified to provide the first RAD inventory for the entire South Island. The temporal distribution of RADs indicates censoring of the record over the Holocene. >500 year intervals exist between RA events from 12,000 to 2,000 years ago; a more complete record is shown for the last 1,000 to 100 years with intervals of > 50 - < 150 years. The last 100 years shows phases of co-seismic RAD generation, a period of RAD quiescence and a recent increase in aseismic RAD occurrence. The spatial distribution of RADs suggests that the West Coast, Fiordland and Nelson could have experienced fluvial censoring of deposits. The sediment routing characteristics of catchments in these regions, where the majority of rivers have direct pathways from RADs to the ocean, suggest that fluvially reworked RAD material could be stored within alluvial flats and braidplains. Agglomerate grains (microscopic grains which are diagnostic of RAs) were used to identify fluvially reworked RAD material. Grains were detected in dam-breach flood terraces up to 1km downstream of known RADs. Contemporary river sediment samples showed no agglomerate presence, this suggests that 1) agglomerates break down under extended fluvial transport, 2) they are not supplied to river systems outside of flood events, 3) agglomerates become diluted by other river sediment or 4) they become buried in discrete sedimentary layers. In order to investigate the redistribution of coarse RAD material within South Island rivers, a micro-scale flume model was developed. Using ultra-violet sand as a novel analogue for a RAD, the redistribution of material through an idealised South Island catchment could be examined. The model showed that RAD material is deposited in discrete aggradational layers in dam proximal locations. Downstream, the sedimentary signal is rapidly diluted by ordinary river sediment flux. The research shows that the RAD record for the South Island is incomplete and that fluvial censoring is prevalent within the West Coast, Nelson and Fiordland. The agglomerate tracing method can be used to identify the presence of RADs in fluvial systems proximal to RADs but the signal is undetectable after ~1km from the deposit. Both field sampling and flume modelling show that localised flood derived aggradational layers, close to deposit locations, will archive reworked RAD material. These results have important implications for understanding the magnitude and frequency of RADs within New Zealand and other similar high-mountain, tectonically active regions of the globe.
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Altaye, Elias. "The geology and geochemistry of the north-eastern sector of Lyttelton volcano, Banks Peninsula, New Zealand." Thesis, University of Canterbury. Department of Geology, 1989. http://hdl.handle.net/10092/3865.
Full textAbstract:
Miocene volcanic activity constructed the Lyttelton composite cone 11 -10 Ma ago. The Lyttelton volcano which forms the north western half of Banks
Peninsula represents a significant volume of mafic volcanic rocks together with some of felsic and minor intermediate composition. In addition to these, the volcano is characterized by pyroclastic deposits (lahars and
lithic-crystal tuffs). Lyttelton lavas are intruded by numerous radial dikes
and also by a variety of lava domes, sills and plugs. The volcanism was
mainly Hawaiian in style, with some Vulcanian and occasional Strombolian
styles of activity.
Within this composite volcano, two major phase of volcanic activity are
recognized. These are the main phase (the older) and late phase (younger)
Lyttelton volcanics defined on the basis of field relationships, petrography
and geochemistry. The late phase volcanics are designated formally as the
Mt Pleasant Formation. The main and late phase Lyttelton volcanics range
from mafic to felsic rocks compositions. The dikes range from basalt to
trachyte and intruded the volcano during the main and late phase of
volcanic activity. Sills and intrusions have felsic compositions. The major
valleys and the lahar deposits represent periods of degradation of the active
cone.
Both the main and late phase (Mt Pleasant Formation) Lyttelton volcanics are
alkaline tending transitional in geochemical affinity. The alkaline, sodic
series Lyttelton rocks are members of the alkali olivine basalt association and
this designation is consistent with mineralogy. Some intermediate and felsic
Lyttelton rocks are subalkaline and potassic in composition, but they are
classified as alkaline olivine basalt associations on the basis of their
mineralogy.
There are geochemical distinctions in major oxides, trace -elements and
normative mineralogy between the main and late (Mt Pleasant Formation)
Lyttelton rocks. The petrogenesis of the main and late Lyttelton volcanics
mafic lavas is best explained by low pressure crystal fractionation of the
observed phenocryst phases. The intermediate and felsic rocks are derived
by similar processes with minor crustal contamination. Tectonically, Lyttelton
volcanics represent “within plate” alkaline mafic volcanism.
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Schulte, Daniel. "Kinematics of the Paparoa Metamorphic Core Complex, West Coast, South Island, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2011. http://hdl.handle.net/10092/5459.
Full textAbstract:
The Paparoa Metamorphic Core Complex developed in the Mid-Cretaceous due to continental extension conditioning the crust for the eventual breakup of the Gondwana Pacific Margin, which separated Australia and New Zealand. It has two detachment systems: the top-NE-displacing Ohika Detachment at the northern end of the complex and the top-SW-displacing Pike Detachment at the southern end of the complex. The structure is rather unusual for core complexes worldwide, which are commonly characterised by a single detachment system. Few suggestions for the kinematics of the core complex development have been made so far. In this study structural-, micrographic- and fission track analyses were applied to investigate the bivergent character and to constrain the kinematics of the core complex. The new results combined with reinterpretations of previous workers’ observations reveal a detailed sequence of the core complex exhumation and the subsequent development.
Knowledge about the influence and the timing of the two respective detachments is critical for understanding the structural evolution of the core complex. The syntectonic Buckland Granite plays a key role in the determination of the importance of the two detachment systems. Structural evidence shows that the Pike Detachment is responsible for most of the exhumation, while the Ohika Detachment is a mere complexity. In contrast to earlier opinions the southwestern normal fault system predates the northeastern one. The Buckland Pluton records the ceasing pervasive influence of the Pike Detachment, while activity on the Ohika Detachment had effect on the surface about ~8 Ma later.
Most fission track ages are not related to the core complex stage, but reflect the younger late Cretaceous history. They show post core complex burial and renewed exhumation in two phases, which are regionally linked to the development of the adjacent Paparoa Basin and the Paparoa Coal Measures to the southwest and to the inception of seafloor spreading in the Tasman Sea in a larger context.
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Newman, Alice. "Strain localization and exhumation of the lower crust: A study of the three-dimensional structure and flow kinematics of central Fiordland, New Zealand." ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/312.
Full textAbstract:
In this thesis, I present structural and kinematic data on rock fabrics, shear zones and fault zones from the Cretaceous Malaspina orthogneiss and some of its satellite plutons in central Fiordland, New Zealand. Central Fiordland exposes a large tract of granulite- to eclogite-facies lower crust that was exhumed between late Mesozoic to Cenozoic times. The deformational structures of interest were formed and preserved during the lifecycle of a Cretaceous continental arc that involved thickening to over 60 km followed by collapse and rifting. As such, they provide an excellent opportunity to study strain localization in the deep crust and the process of exhumation.
Detailed structural mapping, analysis, and the construction of a 45-kilometer cross section through the Malaspina orthogneiss and adjacent plutons reveal the spatial distribution, sequence, and kinematics of crosscutting deformational structures. The earliest structures record Cretaceous magmatism, high-grade metamorphism at the granulite and eclogite facies, and ductile flow that resulted in widespread (over 1200 km2), disorganized magmatic foliations. These events were followed by regional extension that resulted in the formation of multiple, ≤0.5 km-thick ductile, upper amphibolite facies shear zones that record cooling, hydration, and horizontal flow during the Late Cretaceous. Extension continued but changed obliquity in the early to middle Tertiary and resulted in sets of strike-slip and normal brittle to semi-brittle faults forming a sinistral transtensional system. These faults are distributed across central Fiordland and crosscut and transpose the ductile shear zones and magmatic foliations. Lastly, a change in relative plate motions resulted in the inception of the Alpine fault and the development of a late Tertiary transpressional fault system that crosscuts all previous structures.
The dominant factors controlling strain localization in central Fiordland changed from magma, heat, and melting, to fluid activity, plate boundary reorganization, and reactivation of inherited structures. The succession of contrasting strain localization styles in response to changing tectonic and local conditions led to the development of multiple phases of deformation. These multiple phases of deformation allowed the deep crust to be exhumed in a heterogeneous and fragmented, or 'piecemeal', way. In particular, the inability of late Cretaceous ductile shear zones to fully exhume the lower crust was compensated by the ability of early Tertiary transtensional faults to simultaneously thin and further exhume the lower crust. Investigations of strain localization patterns in central Fiordland shed light on the causes and mechanisms of crustal exhumation, a phenomenon that is integral to the lifecycle of virtually all orogenic belts.
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Mitchell, Peter Ashley. "Geology, hydrothermal alteration and geochemistry of the Iamalele (D'Entrecasteaux Islands, Papua New Guinea) and Wairakei (North Island, New Zealand) geothermal areas." Thesis, University of Canterbury. Geology, 1989. http://hdl.handle.net/10092/5561.
Full textAbstract:
The geothermal system at Iamalele is hosted by a series of late Quaternary high-silica dacite to rhyolite ignimbrite, air-fall tuff and related volcaniclastic rocks. The ignimbrite flows are intercalated with calc-alkalic andesite and low-silica dacite lavas, some of which are high-Mg varieties. The Iamalele Volcanics may be related to caldera collapse and post-caldera volcanism. Geothermal activity occurs over 30 km2 of the Iamalele area. Chemical analyses of water from hot springs indicate that the near-surface reservoir is dominated by an acid-sulphate fluid, and that the deeper reservoir fluid probably has a significant seawater component. Analyses of rock and soil samples within the limits of geothermal activity identified several areas of above background values in Au, Hg, As and Sb. A diamond drill hole was completed to a depth of ~200m in one of these areas. Hydrothermal alteration identified in the drill core indicates that the upper 200 m of the geothermal reservoir is well-zoned and contains a trace element signature characteristic of high-level, epithermal precious metal deposits. With increasing depth mineral assemblages indicative of advanced argillic, intermediate argillic and potassic alteration were observed in the recovered core.
The Wairakei geothermal system is hosted by a voluminous sequence of late Quaternary rhyolitic ignimbrite, air fall tuff and related volcaniclastic rocks intercalated with andesite to rhyolite lavas. The volcanic sequence was deposited during formation of the Maroa and Taupo caldera volcanoes, and geothermal activity is localized within a diffuse border zone between these two volcanic centres. The high-temperature reservoir at Wairakei is primarily restricted to porous pyroclastic rocks of the Waiora Formation. Geothermal activity is exposed over ~25 km2 of the Wairakei area. Chemical analyses of well discharge indicate that the fluid is a low salinity, low total sulphur, near-neutral pH chloride water with a local meteoric source. Temperature profiles for ~60% of the Wairakei wells were used to construct a c. 1950 view of the thermal zoning of the reservoir. When compared to the estimated preproduction isotherms, reconnaissance fluid inclusion homogenization temperatures indicated that the deeper portion of the reservoir had cooled by ~45ºC prior to production discharge. Hydrothermal rock alteration within the reservoir is systematically zoned and may be separated into four principal assemblages: propylitic, potassic, intermediate argillic and advanced argillic. Calcium zeolites, mainly wairakite, mordenite and laumontite, occur throughout the reservoir and, with the exception of laumontite, form an integral part of either the propylitic or potassic assemblage. Intermediate argillic alteration is widespread but is not strongly developed. The distribution of advanced argillic alteration is sporadic and restricted to depths less than 65 m. Below a depth of ~500 m potassic alteration commonly overprints propylitic alteration. The location of the "average" Wairakei fluid on several activity diagrams drawn for 100°, 200°, 250° and 300°C indicates that propylitic and potassic alteration probably formed in equilibrium with a hydrothermal fluid chemically equivalent to the modern reservoir fluid at temperatures between ~275° and ~210°C. Assays of drill samples indicate that trace amounts of gold (<0.04 g/t) and other metals permeate the reservoir. Samples of siliceous sinter collected from wellhead production equipment contain significant quantities of precious metals and also platinum group and base metals. Metal-rich scale from a back pressure plate (well 66) was analysed by optical microscopy and by electron microprobe analysis. The scale is composed of several discrete mineral phases which show a distinct paragenesis.
Hydrothermal alteration and metallization identified within the reservoirs at Iamalele and Wairakei are similar to hydrothermal alteration and metallization identified within the epithermal precious metal deposits of Rawhide and Round Mountain (Nevada, U.S.A.). The major difference between these systems is the much greater abundance of gold and silver at Rawhide and Round Mountain. Conclusions drawn from these comparisons include: (1) within high-temperature active systems gold remains in solution or is dispersed at low grades; (2) boiling does not appear to be a viable means
of producing a gold ore deposit within deep (>500 m) hydrothermal reservoirs and (3) the formation of a major precious metal ore deposit may require the superposition of a structural event on a waning geothermal system to initiate an extended period of fluid mixing.
High-Mg lavas similar to ones identified at Iamalele occur elsewhere in the late Cenozoic arc-type volcanic associations of south-eastern Papua New Guinea. Detailed geochemical studies of these rocks have revealed the presence of relatively aphyric lavas which are high in MgO, Cr, and Ni and form an integral part of the arc-type association. The high concentrations of these elements relative to typical arc-related rocks are thought to reflect the chemical composition of the initial melt. High-Mg lavas occur in other volcanic arcs of Papua New Guinea as well as in several other circum-Pacific volcanic arcs, and it is likely that high-Mg lavas form a fundamental component of most, if not all, volcanic arcs.
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Hocking, Michael W. A. "The Calypso hydrothermal vent field: The seafloor expression of an active submarine low-sulphidation epithermal system, Bay of Plenty, New Zealand." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27852.
Full textAbstract:
The Taupo Volcanic Zone (TVZ) is an area of extensive volcanism and geothermal activity in the North Island of New Zealand. The Calypso Hydrothermal Vent Field (CHVF) is located in an offshore extension of the TVZ on continental shelf, approximately 10 km southwest of the White Island subaerial volcano, at 180-200 m water depth in the Bay of Plenty, New Zealand. Active, moderate temperature (up to 201°C) hydrothermal venting is contained within the Whakatane Graben, a northeast trending depression that has been partially filled by tephra from regional, subaerial volcanic eruptions.
Venting of hydrothermal fluid through the volcaniclastic material has led to a varied and geographically distinct assemblage of alteration mineral phases in 4 vent fields in an area of approximately 50 km2. Carbon dioxide is the primary gas phase measured at active vent sites; sulfur is present as reduced H2S gas.
The North Vent Field (NVF) is the original site of hydrothermal venting reported at Calypso. Weakly lithified volcaniclastic material recovered from this site has been altered primarily to montmorillonite, a dioctahedral smectite clay; minor mixed-layer clays were also detected. Native sulfur is spatially associated with the pervasively clay-altered samples, and is observed cementing volcaniclastic particles and filling primary pore spaces. Anhydrite mounds were also observed in the NVF.
The principal hydrothermal alteration phase at the Southeast Vent Field (SEVF) and the Southwest Vent Field (SWVF) is amorphous silica which has filled the pore spaces between volcaniclastic particles and has overprinted early barite, minor clay, and native sulfur mineral phases. Cinnabar, stibnite, and amorphous arsenic sulfides form crusts on the outer surfaces of the samples as well as filling fractures, and forming inclusions within pyrite-silica veins. Textural relationships indicate volatile metal As, Sb, and Hg deposition is contemporaneous with silica precipitation. Clay-altered, sulfur-rich samples were also recovered from the Southeast and Southwest Vent Fields (SEVF, SWVF) but are volumetrically subordinate to the silica alteration facies. Several volcaniclastic samples from this site contained liquid hydrocarbon and charcoal fragments.
A similar juxtaposition of alteration phases is observed in active geothermal environments in the subaerial portion of the TVZ (e.g., Waiotapu, Broadlands-Ohaaki). Where fluid conduits intersect the surface, near-neutral pH, chloride water will precipitate silica sinter with elevated volatile metal concentration +/- precious metals. Sinter deposits are characterized by a terraced morphology of opal precipitates and define the paleosurface in fossil epithermal systems. Such deposits have not been reported in the submarine environment. However, locations with high silica concentration, "sinter-like" material, and anomalous Hg-Sb-As concentrations have been described. At the Calypso field volcaniclastic material is cemented by amorphous silica similar to the silicified stratigraphy observed below silica sinter in some fossil epithermal deposits.
The CO2 and H2S gas present in the hydrothermal fluid rise to areas of elevated topography peripheral to the sinter. Mixing of CO2 with water creates carbonic acid, and oxidation of H 2S may produce native sulfur and sulfuric acid; the extent of these reactions is limited by the availability of oxygen. In subaerial epithermal systems, the formation of sulfuric acid, and in turn advanced argillic steam-heated alteration, is limited to the vadose zone, where there is sufficient oxygen to produce sulfuric acid. In the absence of atmospheric oxygen, the production of sulfuric acid in submarine environments is similarly limited, and this explains the absence of aluminous clay minerals and alunite in the Calypso samples. Disproportionation of SO2(g) to H2SO4 (aq) does, however, create advanced argillic alteration in some higher-temperature submarine volcanic-hydrothermal systems (e.g., Brothers Volcano, de Ronde et al., 2005).
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Alekhue, Jude E. "Investigation of the Miocene Moki Formation within the Parahaki 3D Survey; Taranaki Basin, Offshore New Zealand Using Some Geophysical Tools." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10826643.
Full textAbstract:
Abstract A geophysical analysis was carried out to delineate and characterize the Mid-Miocene Moki sandstone reservoir in the Taranaki basin, offshore New Zealand. The study is an effort to use the new 3D seismic from the Parahaki survey to answer some concerns of an earlier 2D seismic line that drilled a dry hole. Well log curves were used to identify two sands within the Moki package (Moki-1 and Moki-2). Amplitude Variation with Offset (AVO) forward modeling was done to evaluate the seismic response of the Moki-1 and Moki-2 sands. The modeling results indicate that the Moki-1 sand exhibits a Class III AVO response, while the result of the Moki-2 show a class 2/2P AVO response. The Far times Far minus Near (Far*(Far- Near) AVO attribute was employed to discriminate hydrocarbon from the background geology. This attribute was applied because gathers were available only over a subset of the survey and not the entire survey area. Intercept/gradient crossplot of gathers close to the well location falls in quadrant IV and shows a wet sandstone background trend, which is consistent with the modeled response. The results from the analysis underscore the application of fluid substitution and AVO synthetic modeling in reservoir seismic studies.
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Brown, Stuart J. A. "Geology and geochemistry of the Whakamaru Group ignimbrites, and associated rhyolite domes, Taupo Volcanic Zone, New Zealand." Thesis, University of Canterbury. Geology, 1994. http://hdl.handle.net/10092/6895.
Full textAbstract:
The Whakamaru group ignimbrites are a Widespread and voluminous group of welded crystal-rich ignimbrites which outcrop along the eastern and western margins of the Taupo Volcanic Zone (TVZ), New Zealand. They have previously been mapped as Whakamaru (s.s), Manunui, Rangitaiki, Te Whaiti, and Paeroa ignimbrites, and have a combined volume of more than 1000km³ (DRE). The ignimbrites were erupted from a large vent area within central TVZ at 340ka, following a c.350ka hiatus in caldera forming activity in TVZ. This study investigates field and volcanological aspects of the ignimbrites, the geochemistry of pumice clasts and plutonic lithics, and the geochemistry of rhyolite lavas of the Western Dome Belt (WDB).
The postulated vent area for the ignimbrites lies to the north of Lake Taupo and overlaps with the younger Taupo and Maroa volcanoes. Maximum lithic data indicate that the western margin of the vent area was located at or within a few kilometres east of the WDB, and probably overlapped with the northern part of Lake Taupo, providing clear support for a North Taupo/ Maroa caldera source. Isopleths close around an area previously modelled as a deep basement collapse structure, suggesting this area may have been an important focus of eruption and collapse within a broad 'Whakamaru Centre' comprising several nested collapse structures.
On the basis of field evidence, mineral chemistry, and new Ar-Ar dates, Whakamaru, Manunui, Rangitaiki, Te Whaiti, Wairakei, and Paeroa Range Group (PRG) ignimbrites are considered to be correlatives. Manunui ignimbrite represents the stratigraphically lowest unit(s) of Whakamaru that is locally more highly welded and is less crystal rich in distal areas. Manunui ignimbrite therefore correlates with unit A of Briggs (1976) at Maraetai. East of TVZ, Te Whaiti ignimbrite also corresponds to the lowermost part of Lower Rangitaiki ignimbrite, with a gradational boundary between the two. There is no clear evidence for a significant time break between either Manunui and Whakamaru, or Te Whaiti and Rangitaiki ignimbrites. High precision Ar-Ar dating indicates eruptions occurred over a period of less than c.5ka, and lack of field evidence for a significant time break suggests a duration of no more than hundreds of years.
Electron microprobe analysis of whole-rock samples throughout the ignimbrite sequence identify multiple populations of hornblende and biotite, whereas orthopyroxene has a relatively narrow compositional range. There is apparently no systematic variation in the chemistry of ferromagnesian silicate minerals with stratigraphic height. In contrast, Fe-Ti oxide minerals show considerable variability with stratigraphic height, becoming more Mg-rich toward the base of the ignimbrite. There is a corresponding trend in calculated Fe-Ti oxide temperatures, with generally high equilibrium temperatures (800-820°C) at the base, and generally lower, but widely variable (730-900+°C) temperatures in middle and upper parts.
Study of juvenile pumices has identified five distinct magma types (rhyolites A-D, and high alumina basalt) and significant gradients in temperature, water content, and Sr isotopic composition in the preeruptive magma system. Rhyolite pumice clasts range from 70 to 77 wt% SiO₂, and mixed basalt/rhyolite clasts range from 51.7 to 68.0% SiO₂. There is a marked variation in mineral assemblage with composition. The low silica type A rhyolite pumices contain plagioclase, quartz, orthopyroxene, hornblende, biotite, and magnetite with distinctive large rounded quartz phenocrysts. High silica type B and C pumices contain quartz (smaller, subhedral phenocrysts), plagioclase, sanidine, biotite, and magnetite/ilmenite. Biotite therefore becomes the dominant mafic phase at high silica compositions as orthopyroxene and hornblende disappear in response to increasing P(H20) and decreasing temperature conditions. Calculated Fe-Ti oxide equilibrium temperatures range from 730°C in high silica pumices to 820°C in low silica type A pumices. Rare earth elements show a general enrichment in the more evolved pumices, and progressively increasing Eu* from type A to C. More evolved rhyolite types B and C are related to type A magma by a two-stage crystal fractionation process, probably by side wall crystallisation and convective fractionation within a large, zoned magma chamber. The first step involved 30-40% fractionation of a plagioclase-dominated (but sanidine-free) assemblage to produce a type B magma, which in turn underwent fractionation of a plagioclase/quartzlsanidine assemblage to produce the highly evolved, but relatively Ba-depleted type C magmas. Petrographic and temperature trends in ignimbrite wholerock suggest that eruptions commenced with the hottest, least evolved magmas, and more evolved magmas became important at a later stage in the eruption. This sequence precludes simple sequential tapping of a large zoned magma chamber, and indicates a complex magma chamber configuration and/or withdrawal dynamics during eruption.
Two types of plutonic lithics have been recovered from Whakamaru group ignimbrite; leucocratic biotite monzogranite, and medium- to fine-grained dolerites. Whakamaru granites are chemicallymore evolved, and are strongly depleted in HREE compared to granitoid lithics from Atiamuri and Tarawera. They are chemically unlike pumices from Whakamaru group ignimbrite, and are not comagmatic.
Rhyolite lavas of the WDB were extruded along a N-S trending curvilinear structure that marks the western boundary of the TVZ, and also coincides with the western margin of the Whakamaru caldera. Analyses fall into two compositional groups; the Western Dome Complex, south of the Waikato River are chemically variable (73.4-76.4% SiO₂), whereas the Northwestern Dome Complex are predominantly high-silica rhyolites (>77% SiO₂). The lavas have similar trace element and REE characteristics to Whakamaru pumices, but have lower ⁸⁷Sr/⁸⁶Sr ratios, indicating they are not simply degassed remnants of the Whakamaru magma system, but represent new crustal melts.
The Whakamaru magma system provides clear evidence that (less evolved) low silica rhyolites undergo significant fractionation at shallow crustal levels in TVZ, to produce the generally more evolved rhyolites most commonly erupted at the surface. Type A magma with its relatively high Sr, low Rb and SiO₂, and lack of a significant Eu anomaly may be close to a 'primary' crustal melt composition. Trace element and REE characteristics for selected rhyolite domes and ignimbrites suggest the crustal source for TVZ rhyolites is not homogenous, but may be variable, at least with respect to mineral composition and melting behaviour in space and time.
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Schoenenberger, Katherine R. "LITTLE ICE AGE CHRONOLOGY FOR CLASSEN AND GODLEY GLACIERS, MOUNT COOK NATIONAL PARK, NEW ZEALAND." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990634749.
Full text
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Cammans, Phillip C. "Mechanisms and Timing of Pluton Emplacement in Taranaki Basin, New Zealand Using Three-Dimensional Seismic Analysis." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5649.
Full textAbstract:
Several off-shore volcano-plutonic complexes are imaged in detail in the Parihaka 3D seismic survey in the Taranaki Basin of New Zealand. Three intrusions were analyzed for this study. Part of the Mohakatino Volcanic Centre (15 to 1.6 Ma), these intrusions have steep sides, no resolvable base reflectors, no internal stratification or structure, and they exhibit doming and faulting in the sedimentary strata above the intrusions. Deformation along the sides is dominated by highly attenuated, dipping strata with dips of 45° or higher that decrease rapidly away from the intrusions. Doming extends several hundred meters from the margins and produced many high-angle normal faults and thinned strata. The intrusions lie near normal faults with the Northern Intrusion lying directly adjacent to a segment of the Parihaka Fault. The Central Intrusion has localized normal faults cutting a graben in the area directly above the intrusion and extending in a NE-SW direction away from it. The Western Intrusion is near the western edge of the Parihaka 3D dataset and is not situated directly adjacent to extensional faults.Two distinct zones of intrusion-related faults developed around both the Northern and Central Intrusions representing two different stress regimes present during emplacement, a local stress field created by the intrusions during emplacement and the regional stress field. The deeper zones contain short radial faults that extend away from the intrusion in all directions, representing a local stress field. The shallower faults have a radial pattern above the apex of each intrusion, but farther from it, they follow the regional stress field and trend NE. Using our techniques to interpret radial faulting above both intrusions and the principal of cross-cutting relations, timing of emplacement for these intrusions are 3.5 Ma for the Northern Intrusion and between 5 and 4 Ma for the Central and Western Intrusions.Observed space-making mechanisms for the Northern and Central Intrusions include doming (~16% and 11%, respectively), thinning and extension of roof strata (~4% for both), and extension within the basin itself (29% and 12%). Stoping and floor subsidence may have occurred, but are not visible in the seismic images. Magmatic extension may have played a significant role in emplacement.Several gas-rich zones are also imaged within the seismic data near the sea-floor. They appear as areas of acoustic impedance reversal compared to surrounding sedimentary strata and have a reversal of amplitude when compared to the sea floor. The gas in these zones is either biogenic or sourced from deeper reservoirs cut by normal faults.
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Dianiska, Kathryn Elise. "The interplay between deformation and metamorphism during strain localization in the lower crust: Insights from Fiordland, New Zealand." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/387.
Full textAbstract:
In this thesis, I present field, microstructural, and Electron Backscatter Diffraction (EBSD) analyses of rock fabrics from high strain zones in exposures of lower crustal Cretaceous plutons at Breaksea Entrance, Fiordland, New Zealand. The interplay between deformation and metamorphism occurs across multiple scales at the root of a continental arc. I show a series of steps in which retrogressive metamorphism is linked to the accommodation of deformation.
I define three main phases of deformation and metamorphism at Breaksea Entrance. The first phase (D1) involved emplacement of dioritic to gabbroic plutons at depths up to 60 km. The second phase (D2) is characterized by deformation and metamorphism at the granulite and eclogite facies that produced high strain zones with linear fabrics, isoclinal folding of igneous layering, and asymmetric pressure shadows around mafic aggregates. New structural analyses from Hāwea Island in Breaksea Entrance reveal the development of doubly plunging folds that define subdomes within larger, kilometer-scale gneiss domes. The development and intensification of S2 foliations within the domes was facilitated by the recrystallization of plagioclase and clinopyroxene at the micro-scale (subgrain rotation and grain boundary migration recrystallization), consistent with metamorphism at the granulite and eclogite facies and climb-accommodated dislocation creep. EBSD data show a strong crystallographic preferred orientation in plagioclase during D2 deformation. The third phase (D3) is characterized by deformation and metamorphism at the upper amphibolite facies that produced sets of discrete, narrow shear zones that wrap and encase lozenges of older fabrics. Structural analyses reveal a truncation and/or transposition relationship between the older S2 and the younger S3 foliations developed during D3. Progressive localization of deformation during cooling, hydration, and retrogression, resulted in the breakdown of garnet and pyroxene to form hornblende, biotite, fine plagioclase and quartz. EBSD data show a strong crystallographic preferred orientation in hornblende. During D3, hornblende and biotite accommodated most of the strain through fluid-assisted diffusion creep.
The last two events (D2 and D3) reflect a transition in deformation and metamorphism during exhumation, as well as a focusing of strain and evolving strain localization mechanisms at the root of a continental arc. An examination of structures at multiple scales of observation reveals that fabrics seen in the field are a composite of multiple generations of deformation and metamorphism.
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Toy, Virginia Gail, and n/a. "Rheology of the Alpine Fault Mylonite Zone : deformation processes at and below the base of the seismogenic zone in a major plate boundary structure." University of Otago. Department of Geology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080305.110949.
Full textAbstract:
The Alpine Fault is the major structure of the Pacific-Australian plate boundary through New Zealand�s South Island. During dextral reverse fault slip, a <5 million year old, ~1 km thick mylonite zone has been exhumed in the hanging-wall, providing unique exposure of material deformed to very high strains at deep crustal levels under boundary conditions constrained by present-day plate motions. The purpose of this study was to investigate the fault zone rheology and mechanisms of strain localisation, to obtain further information about how the structural development of this shear zone relates to the kinematic and thermal boundary constraints, and to investigate the mechanisms by which the viscously deforming mylonite zone is linked to the brittle structure, that fails episodically causing large earthquakes.
This study has focussed on the central section of the fault from Harihari to Fox Glacier. In this area, mylonites derived from a quartzofeldspathic Alpine Schist protolith are most common, but slivers of Western Province-derived footwall material, which can be differentiated using mineralogy and bulk rock geochemistry, were also incorporated into the fault zone. These footwall-derived mylonites are increasingly common towards the north.
At amphibolite-facies conditions mylonitic deformation was localised to the mylonite and ultramylonite subzones of the schist-derived mylonites. Most deformation was accommodated by dislocation creep of quartz, which developed strong Y-maximum crystallographic preferred orientation (CPO) patterns by prism (a) dominant slip. Formation of this highly-oriented fabric would have led to significant geometric softening and enhanced strain localisation. During this high strain deformation, pre-existing Alpine Schist fabrics in polyphase rocks were reconstituted to relatively well-mixed, finer-grained aggregates. As a result of this fabric homogenisation, strong syn-mylonitic object lineations were not formed. Strain models show that weak lineations trending towards ~090� and kinematic directions indicated by asymmetric fabrics and CPO pattern symmetry could have formed during pure shear stretches up-dip of the fault of ~3.5, coupled with simple shear strains [greater than or equal to]30. The preferred estimate of simple:pure shear strain gives a kinematc vorticity number, W[k] [greater than or equal to]̲ 0.9997.
Rapid exhumation due to fault slip resulted in advection of crustal isotherms. New thermobarometric and fluid inclusion analyses from fault zone materials allow the thermal gradient along an uplift path in the fault rocks to be more precisely defined than previously. Fluid inclusion data indicate temperatures of 325+̲15�C were experienced at depths of ~45 km, so that a high thermal gradient of ~75�C km⁻� is indicated in the near-surface. This gradient must fall off to [ less than approximately]l0�C km⁻� below the brittle-viscous transition since feldspar thermobarometry, Ti-inbiotite thermometry and the absence of prism(c)-slip quartz CPO fabrics indicate deformation temperatures did not exceed ~ 650�C at [greater than or equal to] 7.0-8.5�1.5 kbar, ie. 26-33 km depth.
During exhumation, the strongly oriented quartzite fabrics were not favourably oriented for activation of the lower temperature basal(a) slip system, which should have dominated at depths [less than approximately]20 km. Quartz continued to deform by crystal-plastic mechanisms to shallow levels. However, pure dislocation creep of quartz was replaced by a frictional-viscous deformation mechanism of sliding on weak mica basal planes coupled with dislocation creep of quartz. Such frictional-viscous flow is particularly favoured during high-strain rate events as might be expected during rupture of the overlying brittle fault zone. Maximum flow stresses supported by this mechanism are ~65 Mpa, similar to those indicated by recrystallised grain size paleopiezometry of quartz (D>25[mu]m, indicating [Delta][sigma][max] ~55 MPa for most mylonites). It is likely that the preferentially oriented prism (a) slip system was activated during these events, so the Y-maximum CPO fabrics were preserved. Simple numerical models show that activation of this slip system is favoured over the basal (a) system, which has a lower critical resolved shear stress (CRSS) at low temperatures, for aggregates with strong Y-maximum orientations. Absence of pervasive crystal-plastic deformation of micas and feldspars during activation of this mechanism also resulted in preservation of mineral chemistries from the highest grades of mylonitic deformation (ie. amphibolite-facies).
Retrograde, epidote-amphibolite to greenschist-facies mineral assemblages were pervasively developed in ultramylonites and cataclasites immediately adjacent to the fault core and in footwall-derived mylonites, perhaps during episodic transfer of this material into and subsequently out of the cooler footwall block. In the more distal protomylonites, retrograde assemblages were locally developed along shear bands that also accommodated most of the mylonitic deformation in these rocks. Ti-in-biotite thermometry suggests biotite in these shear bands equilibrated down to ~500+̲50�C, suggesting crystal-plastic deformation of this mineral continued to these temperatures. Crossed-girdle quartz CPO fabrics were formed in these protomylonites by basal (a) dominant slip, indicating a strongly oriented fabric had not previously formed at depth due to the relatively small strains, and that dislocation creep of quartz continued at depths [less than or equal to]20 km. Lineation orientations, CPO fabric symmetry and shear-band fabrics in these protomylonites are consistent with a smaller simple:pure shear strain ratio than that observed closer to the fault core (W[k] [greater than approximately] 0.98), but require a similar total pure shear component. Furthermore, they indicate an increase in the simple shear component with time, consistent with incorporation of new hanging-wall material into the fault zone. Pre-existing lineations were only slowly rotated into coincidence with the mylonitic simple shear direction in the shear bands since they lay close to the simple shear plane, and inherited orientations were not destroyed until large finite strains (<100) were achieved.
As the fault rocks were exhumed through the brittle-viscous transition, they experienced localised brittle shear failures. These small-scale seismic events formed friction melts (ie. pseudotachylytes). The volume of pseudotachylyte produced is related to host rock mineralogy (more melt in host rocks containing hydrated minerals), and fabric (more melt in isotropic host rocks). Frictional melting also occurred within cataclastic hosts, indicating the cataclasites around the principal slip surface of the Alpine Fault were produced by multiple episodes of discrete shear rather than distributed cataclastic flow. Pseudotachylytes were also formed in the presence of fluids, suggesting relatively high fault gouge permeabilities were transiently attained, probably during large earthquakes. Frictional melting contributed to formation of phyllosilicate-rich fault gouges, weakening the brittle structure and promoting slip localisation. The location of faulting and pseudotachylyte formation, and the strength of the fault in the brittle regime were strongly influenced by cyclic hydrothermal cementation processes.
A thermomechanical model of the central Alpine Fault zone has been defined using the results of this study. The mylonites represent a localised zone of high simple shear strain, embedded in a crustal block that underwent bulk pure shear. The boundaries of the simple shear zone moved into the surrounding material with time. This means that the exhumed sequence does not represent a simple 'time slice' illustrating progressive fault rock development during increasing simple shear strains. The deformation history of the mylonites at deep crustal P-T conditions had a profound influence on subsequent deformation mechanisms and fabric development during exhumation.
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Walsh, Andrew Timothy. "Engineering Geomorphological Assessment and Slope Hazard Identification of the Haast Pass Highway Corridor, State Highway Six, Haast Pass New Zealand." Thesis, University of Canterbury. Geological Sciences, 2015. http://hdl.handle.net/10092/10575.
Full textAbstract:
The Haast Pass highway has had a long history of instability since it was constructed in 1960. Steep slopes and deeply incised river create an actively changing geomorphic environment making maintaining the highway corridor hazardous and difficult. This thesis study provides the first comprehensive investigation of the highway corridor between the Summit and Thunder Creek Falls using LiDAR and detailed air-photo analysis to provide the basis for geomorphic mapping. Management of slope hazards to date has been based on a reactive approach treating the immediate unstable areas around landslides after they occur. This study presents the first large-scale geomorphological assessment of the highway corridor identifying surface unit type, slope processes and slope hazards in order to facilitate the development of a long-term highway management strategy.
Because dense vegetation covers nearly all the slopes above the highway in the study area as as such, it has not been possible to adequately investigate slope geomorphology until the availability of LiDAR. This study is the first to use Light direction and ranging[LiDAR] for corridor hazard mapping beneath dense vegetation in New Zealand. The LiDAR survey was flown by New Zealand Aerial Mapping in January 2014 for the New Zealand Transport Agency and was provided for use in this study. The LiDAR surface model created serves as the basis for mapping surface units and landslide features, enabling the identification of slope processes and landslide hazards. Aerial photos were also used to identify surface unit type and slope processes where vegetation was absent and enabled the activity of slopes to be evaluated. Interpretations made using LiDAR were validated using aerial photography and targeted ground truthing with all ground truthing sites confirming the interpretations made.
Large scale geomorphology mapping was undertaken on slopes above the highway on the western side of the valley and showed that there were distinct differences between the southern and northern parts of the highway corridor. Between The Haast Pass Summit and Pipson Creek the slopes are dominated by schist bedrock with regolith confined to small deposits next to the highway and larger deposits in tributary valleys. The slope hazards affecting the highway in this zone are confined to debris sliding and rockfall from regolith deposits and bedrock cliffs next to the highway between Robinson and Pipson Creeks. The slopes between Pipson Creek and the Gates of Haast, in contrast, consist of deep regolith deposits and regolith veneered slopes. Evidence of active and recently active slope processes on the slopes facing the highway confirm the instability is associated with slope hazards including debris flows, debris slides, rock fall and highway collapse.
Small-scale detailed evaluations were undertaken at Diana Falls, Ford Creek, The Hinge and the Gates of Haast with the sites selected based on their history of instability and/or their particu- larly hazardous appearance during the large-scale geomorphology and hazard identification. Using the LiDAR surface model surface units and landslide features were identified and mapped with small-scale engineering geomorphology maps. This information was then used to interpret the subsurface geometry and the failure mode/slope processes acting on the slope enabling an assessment of the current stability and future slope development to be made. Diana Falls was found to have scarps and tension cracks running across the regolith covered slope indicating that future landslides
from this site will be an ongoing problem. At Ford Creek the landslide was identified as a rock compound slide, but assessments of its current stability and future development were unable to be made. Detailed investigations at The Hinge revealed evidence of a large creeping debris slide and the existence smaller debris slides below the highway through the entire investigation area; the debris slides identified show signs of activity and continued debris sliding will continue to affect the highway in the future. The investigation of the Gates of Haast revealed that the slope instability is not as extensive as it has been in the past, however, recent rock slides and debris flows have continued affect the highway and will continue to pose a hazard in the future.
This thesis provides fundamental information required to develop a comprehensive management plan for the Haast Pass highway corridor between the Haast Pass summit and the Gates of Haast. A new landslide management plan has been developed outlining immediate, short-term and long- term options and programmes that should be implemented. Immediate options are steps that can be taken to quickly increase the safety of road users and include moving of highway closure gates and installation of warning signage. Short-term options aim to mitigate landslide hazards where feasible including the installation of rockfall barriers and debris flow attenuators, and lay the groundwork for future avoidance of hazards by undertaking investigations of highway realignment and developing highway closure rainfall thresholds. Long-term options are recommended where landslides will continue to impact the same section of the highway repeatedly and focus on hazard avoidance by building landslide shelters or major highway realignments. The adoption of a management plan ensures security of the highway, protects against loss of life and provides the most cost effective long-term solution to manage the landsliding hazards.
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Ingram, Michael. "4d Strain Path Recorded In The Lower Crust During The Transition From Convergence To Continental Rifting, Doubtful Sound, Fiordland, New Zealand." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/683.
Full textAbstract:
ABSTRACT
Doubtful Sound, in SW New Zealand, exposes an exhumed section of lower crust that represents the root of an Early Cretaceous magmatic arc. Here, the lower crust underwent a change from contraction to extension and these tectonic cycles are fundamental to the growth of continental crust. Mafic-intermediate granulite gneisses occur below the extensional Doubtful Sound shear zone (DSSZ) which records the retrogression and transposition of granulite fabrics at the upper amphibolite facies. I compared 3D rock fabrics, microstructures and textures within and below the DSSZ to determine the processes involved in the shift from contraction to extension and to infer the sequential processes of transforming L>S granulites to L=S amphibolites.
Below the DSSZ, dehydration zones around felsic veins and leucosome in migmatitic orthogneiss record granulite facies metamorphism. Aggregates of clinopyroxene (cpx) and orthopyroxene (opx) that are rimmed by garnet (grt) and interstitial melt are set in a plagioclase (pl) matrix. Peritectic grt, pl-grt symplectites, beads of pl along grain boundaries, and elongate, inclusion-free pl reflect the anatexis. Pl exhibits a crystal preferred orientation (CPO) and evidence of subgrain rotational recrystallization and grain boundary migration, indicating subsolidus deformation outlasted melting. Mafic aggregates are boudinaged and opx developed subgrains. During peak metamorphism high strain was partitioned to locations enriched in melt, producing L>S fabrics and an upward trajectory in the strain path. A comparison of mineral grain shapes indicates that pl accommodated most of the strain. Granulite-amphibolite transitional rocks inside the DSSZ record a heterogeneous retrogression of the granulites to a polyphase metamorphic assemblage of hornblende (hbl), biotite (bt), and fine pl. Also preserved is the resetting of high strain L>S granulite to low strain, L=S amphibolite. Folia of porphyroblastic hbl + bt progressively penetrate the pl matrix via solution mass transfer. Porphyroblastic pl in the rock matrix becomes increasingly transposed to gneissic layering. A path of decreasing gradient from high strain L>S granulite to low strain L=S amphibolite reflects the development of the DSSZ fabric, growth of new minerals and onset to deformation at the amphibolite facies. Inside the DSSZ, amphibolites show an increasing strain gradient from low strain L=S amphibolite to high strain L=S amphibolite. Pl aggregates lack a CPO and are mostly annealed but preserve grain boundary migration microstructures. Hbl is recrystallized and forms asymmetric fish. Evidence of high fluid activity and reaction softening within the DSSZ include increased hbl + bt and bt beards on pl relative to rocks outside the DSSZ.
My observations suggest that magma, heat, and melting initially weakened the lower crust, facilitating the development of high strain zones with L>S fabrics. Partially molten regions deformed by suprasolidus flow and solid portions deformed mostly by dislocation creep in pl and boudinage of cpx + opx. Later, the lower crust was weakened and high strain fabrics were reset from overprinting and transposition as retrogression progressed and low strain L=S fabrics formed. During extension there was an upward trajectory in the strain path to high strain L=S fabrics within the DSSZ, where hbl and bt accommodated more strain. My results illustrate the importance of 1) melting, cooling, and hydration in controlling strain partitioning and the rheological evolution of lower crustal shear zones, and 2) the importance of integrating microstructural and fabric analysis to determine strain paths.
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Duffy, Brendan Gilbert. "The Structural and Geomorphic Development of Active Collisional Orogens, from Single Earthquake to Million Year Timescales, Timor Leste and New Zealand." Thesis, University of Canterbury. Department of Geological Sciences, 2012. http://hdl.handle.net/10092/7527.
Full textAbstract:
The structure and geomorphology of active orogens evolves on time scales ranging from a single earthquake to millions of years of tectonic deformation. Analysis of crustal deformation using new and established remote sensing techniques, and integration of these data with field mapping, geochronology and the sedimentary record, create new opportunities to understand orogenic evolution over these timescales. Timor Leste (East Timor) lies on the northern collisional boundary between continental crust from the Australian Plate and the Banda volcanic arc. GPS studies have indicated that the island of Timor is actively shortening. Field mapping and fault kinematic analysis of an emergent Pliocene marine sequence identifies gentle folding, overprinted by a predominance of NW-SE oriented dextral-normal faults and NE-SW oriented sinistral-normal faults that collectively bound large (5-20km2) bedrock massifs throughout the island. These fault systems intersect at non-Andersonian conjugate angles of approximately 120° and accommodate an estimated 20 km of orogen-parallel extension. Folding of Pliocene rocks in Timor may represent an early episode of contraction but the overall pattern of deformation is one of lateral crustal extrusion sub-parallel to the Banda Arc. Stratigraphic relationships suggest that extrusion began prior to 5.5 Ma, during and after initial uplift of the orogen. Sedimentological, geochemical and Nd isotope data indicate that the island of Timor was emergent and shedding terrigenous sediment into carbonate basins prior to 4.5 Ma. Synorogenic tectonic and sedimentary phases initiated almost synchronously across much of Timor Leste and <2 Myr before similar events in West Timor. An increase in plate coupling along this obliquely converging boundary, due to subduction of an outlying continental plateau at the Banda Trench, is proposed as a mechanism for uplift that accounts for orogen-parallel extension and early uplift of Timor Leste. Rapid bathymetric changes around Timor are likely to have played an important role in evolution of the Indonesian Seaway.
The 2010 Mw 7.1 Darfield (Canterbury) earthquake in New Zealand was complex, involving multiple faults with strike-slip, reverse and normal displacements. Multi-temporal cadastral surveying and airborne light detection and ranging (LiDAR) surveys allowed surface deformation at the junction of three faults to be analyzed in this study in unprecedented detail. A nested, localized restraining stepover with contractional bulging was identified in an area with the overall fault structure of a releasing bend, highlighting the surface complexities that may develop in fault interaction zones during a single earthquake sequence. The earthquake also caused river avulsion and flooding in this area. Geomorphic investigations of these rivers prior to the earthquake identify plausible precursory patterns, including channel migration and narrowing. Comparison of the pre and post-earthquake geomorphology of the fault rupture also suggests that a subtle scarp or groove was present along much of the trace prior to the Darfield earthquake. Hydrogeology and well logs support a hypothesis of extended slip history and suggests that that the Selwyn River fan may be infilling a graben that has accumulated late Quaternary vertical slip of <30 m. Investigating fault behavior, geomorphic and sedimentary responses over a multitude of time-scales and at different study sites provides insights into fault interactions and orogenesis during single earthquakes and over millions of years of plate boundary deformation.
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Moyer, Griffin Amoss. "Strain Accommodation, Metamorphic Evolution, And 3d Kinematics Of Transpressional Flow Within The Lower Crust Of A Cretaceous Magmatic Arc In Fiordland, New Zealand." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1110.
Full textAbstract:
The George Sound Shear Zone (GSSZ) exposed in Bligh Sound within Fiordland, New Zealand allowed us to reconstruct the kinematics of transpressive flow in >100 km2 of exhumed Cretaceous lower crust. We compare the three-dimensional characteristics of the deformation to theoretical models of transpression that assume steady-state flow in a homogeneous medium. This assumption is rarely the case for shear zones that experience metamorphism during deformation. We determined the three-dimensional kinematics of the GSSZ and evaluated the effects of metamorphism on strain accommodation and structural fabric evolution in the GSSZ to determine if metamorphism is an important parameter that transpressional models should account for. We found that metamorphism aided strain localization within the GSSZ and resulted in a style of structural fabric development that deviates from predictions made by theoretical models.
We used foliation and lineation orientation data and field observations to determine GSSZ kinematics. Asymmetric pyroxene σ-porphyroclasts and hornblende fish show top-down-to-the-SW apparent normal shear sense with a sinistral component. The Z-axes of oblate SPO ellipsoids define the vorticity normal section and the moderately WNW-plunging vorticity vector. Foliation deflections relative to the shear zone boundaries yielded a vorticity magnitude (Wk) of ≥0.8. Our kinematic results suggest that the GSSZ records inclined, triclinic transpression with sinistral, top-down-to-the-SW simple shear-dominated flow.
We used finite strain analysis and petrographic analysis to determine that metamorphism influences strain accommodation. Finite strain analyses were performed in 3D on 16 samples using the Rf/ɸ, Fry, and Intercept methods to determine the SPO fabric ellipsoids at different stages of deformation. Petrographic analysis was performed to identify metamorphic reactions using syn-kinematic minerals and constrain deformational temperatures using deformation mechanisms of plagioclase. Early deformation formed a ~13 km wide prolate fabric at granulite facies. Deformation later localized into a ~2-4.6 km wide oblate, mylonitic fabric at upper amphibolite facies. This fabric cross-cuts the prolate fabric and is characterized by metamorphic hornblende and biotite produced from retrogressive hydration reactions. Samples with syn-kinematic biotite contain more shear bands and display more grain size reduction of plagioclase than samples without this phase, suggesting these samples may have accommodated more strain. Changes in syn-kinematic metamorphic minerals were accompanied by steepening of stretching lineations and by changes in foliation orientation.
Our analyses show that retrogressive hydration metamorphism aided strain localization within a cross-cutting oblate fabric, and the uneven distribution of biotite within this domain potentially influenced along strike variation in strain magnitude and fabric ellipsoid symmetry. Our results highlight the influence of fluid-induced metamorphism on shear zone evolution and call for new transpressional models to incorporate changes in rheology due to syn-kinematic metamorphism.
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Hudson, Neville. "The middle Jurassic of New Zealand : a study of the lithostratigraphy and biostratigraphy of the Ururoan, Temaikan and Lower Heterian Stages (?Pliensbachian to ?Kimmeridgian)." Thesis, University of Auckland, 2000. http://hdl.handle.net/2292/2135.
Full textAbstract:
The lithologic and biostratigraphic successions of Ururoan, Temaikan and Lower - Middle Heterian (?Sinemurian, Pliensbachian - ?Kimmeridgian) strata from southwest Auckland, south Otago and Southland, New Zealand, are described and discussed. A more logical correlation of the lithologic sequence at Port Waikato with that at Te Akau is proposed. Two new formations are introduced for the sequences on the western limb of the Kawhia Regional Syncline, the Whakapatiki Mudstone for the fine grained lower Kirikiri Group strata in the Awakino Valley and the Gribbon Formation for the Rengarenga Group strata between Marokopa and Mahoenui. In Southland a new formation (Ben Bolt Formation) is proposed for the c.1340m sequence overlying the Flag Hill Sandstone, in turn overlain by a 485m thick, mudstone-dominated formation for which a long disused name is resurrected (Lora Formation). The Lora Formation is in turn overlain by a coarse-grained unit, for which the name West Peak Formation is proposed. In the absence of suitable alternatives, a subdivision of the Ururoan Stage into a Lower Ururoan, the range-zone of pseudaucella marshalli, and an Upper Ururoan, the interval-zone between the last appearance of Pseudaucella marshalli and the first appearance of a Temaikan fauna is proposed. The existing three-fold subdivision of the Temaikan Stage is emended. Belemnopsis mackayi and B. deborahae are retained as the indices of the Temaikan and its lowest subdivision, as they are present in most sections at a consistent stratigraphic position. Retroceramus (Fractoceramus) inconditus is proposed as the basal Middle Temaikan index species. Retroceramus(R.) brownei, which first appears consistently higher than R. inconditus, but below R. marwicki is proposed as the index for the upper Middle Temaikan. Retroceramus (R.) marwicki is proposed as a replacement upper Temaikan index for "Macrocephalites cf. beta-gamma" which is unsuitable. Meleagrinella n. sp. is inconsistent in its first appearance and therefore unsuitable as a Middle Temaikan index and, although confined to this stage, it ranges from Early to early Upper Temaikan. Basal Temaikan Belemnopsis spp. are absent from sections in the Catlins district whereas the earliest Temaikan taxon appearing above typical Ururoan faunas is Meleagrinella n. sp. In the absence of a better alternative Meleagrinella n. sp. is used to mark the base of the stage in the Catlins sections. However, the base of the Temaikan is here likely to be slightly younger than in other sections. Within the redefined Upper Temaikan four subdivisions based on the sequence of Retroceramus species are recognised. The lowest of these is characterised by the first appearance of R. (R.) marwicki, the second by the first appearance of R. (R.) n. sp. A., the third characterised by the first appearance of R. (R.) stehni, and the highest marked by the first appearance of either R. (R ) sp. C. (a wide triangular form) or sp. D. (an ovate flat form). The presence of these two morphologic forms indicate finer zonation of the Upper Temaikan may be possible, with further field work. The Ururoan to Middle Heterian succession of New Zealand is correlated with the international chronostratigraphic scheme based mainly on comparison of New Zealand's Retroceramus succession with that of South America and Indonesia and on relatively rare ammonites. The Ururoan is equivalent to the ?Sinemurian to Late Toarcian, Temaikan to the ?latest Toarcian to Early Callovian and the Early Heterian to the Middle Callovian to latest Middle to Late Oxfordian. Early Ururoan is correlated with the ?Sinemurian to Pliensbachian based on the presence of the ammonite Juraphyllites. Presence of the Early Toarican ammonites Harpoceras cf. falcifer and Dactylioceras spp. in the Late Ururoan indicates a potential international correlation of ?Late Pliensbachian to Late Toarcian. A ?late Toarcian to Aalenian correlation for the Early Temaikan is suggested by the presence of the European belemnite Brevibelus zieteni. Retroceramus (Fractoceramus) inconditus is similar to the Northern hemisphere Mytiloceramus lucifer and the northern hemisphere Retroceramus gr. popovi and thus suggests a latest Aalenian to Early Bajocian correlation of the Middle Temaikan. The earliest Late Middle Temaikan Retroceramus (Retroceramus) marwicki is also present in the Late Bajocian (Rotundum Zone) of Argentina. ?Teloceras gr. banksi, ?stephanoceras (S.) gr. humphriesianum, Chondroceras (C.) gr. evolvescens, C. (C.) cf. recticostatum, and C. (Defonticeras) cf. oblatum are present in the Middle Temaikan reinforcing an earliest to late Early Bajocian correlation for this substage. Toxamblyites aff. densicostatus Sturani, Chondroceras (C.) gr. Evolvescens (Waagen), C. (Schmidtoceras) orbignyanum (Wright), C. (Defonticeras?) sp. indet. occur with Retroceramus marwicki indicating an Early to Late Bajocian correlation for this zone, slightly broader than in Argentina. However, somewhat anomalously the first of these ammonites suggests a Mid Aalenian to Early Bajocian correlation. The succeeding zone (Retroceramus (R.) n. sp A. zone) has yielded the Latest Bathonian Xenocephalites grantmackiei and Lilloettia aff. boesei. Retroceramus(R.)stehni is the index for the third Upper Temaikan Retroceramus zone and is also known from the latest Bathonian to Early Callovian of Argentina. In New Zealand R. stehni is associated with Lilloettia cf. Lilloetensis and Xenocephalites cf. stipanicici which also indicate a latest Bathonian to Early Callovian correlation. The fourth and highest zone of the Upper Temaikan has yielded the ammonites Araucanites marwicki, Eurycephalites gr. extremus, Iniskinites gr. cepoides and Choffatia (Homoeoplanulites) sp. suggesting an Early to Middle Callovian correlation. The overseas relationships of the associated Retroceramus (R.) spp. C. and D. are unknown. The Heterian index Retroceramus (Retroceramus) galoi is of Oxfordian age in Indonesia where it is associated with Malayomaorica malayomaorica. In New Zealand Araucanites marwicki and Sulaites heteriense are present in the Early Heterian, below the incoming of Malayomaorica malayomaorica, low in the range of Retroceramus galoi. The presence of Sulaites high in the Early Heterian suggests a ?Middle to Late Oxfordian correlation while Araucanites indicates the lowest part of the range of Retroceramus galoi could be slightly older, perhaps Upper Callovian. The biostratigraphic scheme presented here is a significant advance on those proposed previously.
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Wyshnytzky, Cianna E. "Constraining Ice Advance and Linkages to Paleoclimate of Two Glacial Systems in the Olympic Mountains, Washington and the Southern Alps, New Zealand." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/6749.
Full textAbstract:
This thesis investigated marine isotope stage {MIS) 3-2 glacial sequences in the South Fork Hoh River Valley, Washington and the Lake Hawea Valley, New Zealand. Research objectives were to reconstruct the style and timing of ice advance in both areas and to assess the viability of luminescence dating of glacial sediments in various depositional facies and distances from the ice front. This thesis focused on the sedimentology and stratigraphy of surficial and older glacial sequences in the South Fork Hoh and Lake Hawea areas and used OSL and radiocarbon dating techniques to establish age control for the deposits. Specifically, this research identified, described, and dated the stratigraphy of glacial sequences in order to reconstruct ice dynamics. This work also presents updated geomorphic maps for both study areas as an additional way to show ice advance and retreat events recorded in deposited sediment and geomorphic surfaces. The glacial sequence expressed in the Lake Hawea moraine exposure shows four distinct depositional events that represent retreat from an ice position down -valley, re-advance to the Hawea moraine position, and subsequent retreat and deglaciation broadly spanning -32-18 ka. These results document the terminal glacial advance and subsequent retreat in the Lake Hawea Valley and contribute to the wider swath of research studying the last phase of glacial retreat and its connections to climate on the South Island of New Zealand. The Hawea chronology corresponds to other glacial records and paleoclimate reconstructions from the South Island that collectively suggest the commencement of deglaciation at -13 ka. Three late Pleistocene ice positions are preserved in the South Fork Hoh River Valley, here referred to as South Fork 1-3 (SF 1-3). One of these positions has not previously been recognized in this valley or in the mainstem Hoh River Valley. Optically stimulated luminescence (OSL) and radiocarbon (14C) ages are generally consistent throughout the valley. These finding s advocate for a detailed sedimentologic and stratigraphic approach to glacial depos its and questions whether a similar advance or still -stand occurred in other valleys in the region. If so, this may reveal information regarding climate influences on MIS 2 glaciers in the Olympic Mountains. This research also assesses the applicability of OSL dating to glacial deposits in both field areas. Quartz OSL dating was used in the South Fork Hoh study area; however, quartz produced unreliable results in the Hawea study area, so samples were therefore assessed using feldspar methods. The results advocate for a facies-based sampling approach in glacial settings, where better sorted sandy facies and more distal deposits produce better bleached and more reliable age results than other deposits.
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Pedley, Katherine Louise. "Modelling Submarine Landscape Evolution in Response to Subduction Processes, Northern Hikurangi Margin, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2010. http://hdl.handle.net/10092/4648.
Full textAbstract:
The steep forearc slope along the northern sector of the obliquely convergent Hikurangi subduction zone is characteristic of non-accretionary and tectonically eroding continental margins, with reduced sediment supply in the trench relative to further south, and the presence of seamount relief on the Hikurangi Plateau. These seamounts influence the subduction process and the structurally-driven geomorphic development of the over-riding margin of the Australian Plate frontal wedge.
The Poverty Indentation represents an unusual, especially challenging and therefore exciting location to investigate the tectonic and eustatic effects on this sedimentary system because of: (i) the geometry and obliquity of the subducting seamounts; (ii) the influence of multiple repeated seamount impacts; (iii) the effects of structurally-driven over-steeping and associated widespread occurrence of gravitational collapse and mass movements; and (iv) the development of a large canyon system down the axis of the indentation. High quality bathymetric and backscatter images of the Poverty Indentation submarine re-entrant across the northern part of the Hikurangi margin were obtained by scientists from the National Institute of Water and Atmospheric Research (NIWA) (Lewis, 2001) using a SIMRAD EM300 multibeam swath-mapping system, hull-mounted on NIWA’s research vessel Tangaroa. The entire accretionary slope of the re-entrant was mapped, at depths ranging from 100 to 3500 metres. The level of seafloor morphologic resolution is comparable with some of the most detailed Digital Elevation Maps (DEM) onshore. The detailed digital swath images are complemented by the availability of excellent high-quality processed multi-channel seismic reflection data, single channel high-resolution 3.5 kHz seismic reflection data, as well as core samples. Combined, these data support this study of the complex interactions of tectonic deformation with slope sedimentary processes and slope submarine geomorphic evolution at a convergent margin.
The origin of the Poverty Indentation, on the inboard trench-slope at the transition from the northern to central sectors of the Hikurangi margin, is attributed to multiple seamount impacts over the last c. 2 Myr period. This has been accompanied by canyon incision, thrust fault propagation into the trench fill, and numerous large-scale gravitational collapse structures with multiple debris flow and avalanche deposits ranging in down-slope length from a few hundred metres to more than 40 km. The indentation is directly offshore of the Waipaoa River which is currently estimated to have a high sediment yield into the marine system. The indentation is recognised as the “Sink” for sediments derived from the Waipaoa River catchment, one of two target river systems chosen for the US National Science Foundation (NSF)-funded MARGINS “Source-to-Sink” initiative. The Poverty Canyon stretches 70 km from the continental shelf edge directly offshore from the Waipaoa to the trench floor, incising into the axis of the indentation. The sediment delivered to the margin from the Waipaoa catchment and elsewhere during sea-level high-stands, including the Holocene, has remained largely trapped in a large depocentre on the Poverty shelf, while during low-stand cycles, sediment bypassed the shelf to develop a prograding clinoform sequence out onto the upper slope. The formation of the indentation and the development of the upper branches of the Poverty Canyon system have led to the progressive removal of a substantial part of this prograding wedge by mass movements and gully incision. Sediment has also accumulated in the head of the Poverty Canyon and episodic mass flows contribute significantly to continued modification of the indentation by driving canyon incision and triggering instability in the adjacent slopes.
Prograding clinoforms lying seaward of active faults beneath the shelf, and overlying a buried inactive thrust system beneath the upper slope, reveal a history of deformation accompanied by the creation of accommodation space. There is some more recent activity on shelf faults (i.e. Lachlan Fault) and at the transition into the lower margin, but reduced (~2 %) or no evidence of recent deformation for the majority of the upper to mid-slope. This is in contrast to current activity (approximately 24 to 47% shortening) across the lower slope and frontal wedge regions of the indentation. The middle to lower Poverty Canyon represents a structural transition zone within the indentation coincident with the indentation axis. The lower to mid-slope south of the canyon conforms more closely to a classic accretionary slope deformation style with a series of east-facing thrust-propagated asymmetric anticlines separated by early-stage slope basins. North of the canyon system, sediment starvation and seamount impact has resulted in frontal tectonic erosion associated with the development of an over-steepened lower to mid-slope margin, fault reactivation and structural inversion and over-printing.
Evidence points to at least three main seamount subduction events within the Poverty Indentation, each with different margin responses:
i) older substantial seamount impact that drove the first-order perturbation in the margin, since approximately ~1-2 Ma
ii) subducted seamount(s) now beneath Pantin and Paritu Ridge complexes, initially impacting on the margin approximately ~0.5 Ma, and
iii) incipient seamount subduction of the Puke Seamount at the current deformation front.
The overall geometry and geomorphology of the wider indentation appears to conform to the geometry accompanying the structure observed in sandbox models after the seamount has passed completely through the deformation front. The main morphological features correlating with sandbox models include: i) the axial re-entrant down which the Poverty Canyon now incises; ii) the re-establishment of an accretionary wedge to the south of the indentation axis, accompanied by out-stepping, deformation front propagation into the trench fill sequence, particularly towards the mouth of the canyon; iii) the linear north margin of the indentation with respect to the more arcuate shape of the southern accretionary wedge; and, iv) the set of faults cutting obliquely across the deformation front near the mouth of the canyon. Many of the observed structural and geomorphic features of the Poverty Indentation also correlate well both with other sediment-rich convergent margins where seamount subduction is prevalent particularly the Nankai and Sumatra margins, and the sediment-starved Costa Rican margin. While submarine canyon systems are certainly present on other convergent margins undergoing seamount subduction there appears to be no other documented shelf to trench extending canyon system developing in the axis of such a re-entrant, as is dominating the Poverty Indentation.
Ongoing modification of the Indentation appears to be driven by: i) continued smaller seamount impacts at the deformation front, and currently subducting beneath the mid-lower slope, ii) low and high sea-level stands accompanied by variations on sediment flux from the continental shelf, iii) over-steepening of the deformation front and mass movement, particularly from the shelf edge and upper slope.
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Hill, Matthew P. "Evolution of quartz and calcite microstructures exhumed from deep brittle-ductile shear zones in the Southern Alps of New Zealand : a thesis submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Geology /." ResearchArchive@Victoria e-Thesis, 2005. http://hdl.handle.net/10063/33.
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Klahn, Andrew Paul. "Site characterisation of the Whataroa Valley for the Deep Alpine Fault Drilling Project stage 2 (DFDP-2), West Coast, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2011. http://hdl.handle.net/10092/6233.
Full textAbstract:
The Alpine Fault in western South Island ruptures every 300±100 years in large magnitude (7.8 ± 3) earthquakes and presents a major seismic hazard to New Zealand. The Deep Alpine Fault Drilling Project (DFDP) aims to drill, sample, and monitor the Alpine Fault in order to investigate the processes of earthquake genesis, rock deformation, and fault gouge formation for a tectonically active fault late in the seismic cycle. Rapid dextral reverse movements and exhumation rates on the central section of the Alpine Fault at Whataroa Valley make this a geologically favourable setting to drill and sample fault rocks at depth that can be correlated with surface exposures. The suitability of a site for stationing a major drilling operation depends upon practical issues such as the engineering geological characteristics of the proposed site, possible geohazards, and drilling logistics. This thesis presents new engineering geological, geophysical, and geomorphic investigations of the Whataroa Valley for the DFDP-2 drill site in order to provide a framework for proposed future operations.
MASW, GPR and basic geotechnical methods such as test pits and face logs were conducted at various locations at the site to gain geotechnical properties and attempt to find depth to bedrock. Results showed bedrock is at least 25m deep as it was not seen in any of the GPR surveys. Correlation of the MASW and GPR profiles with freshly eroded and face logged outcrops permitted assignment of s-wave velocities to each of the gravels present and confirmation of features seen in the geophysical surveys. Vs30 values gained from the MASW classed the gravels as a soft soil in Site Class D in NZS 1170.5. Expected peak ground accelerations at the study site during an Alpine Fault earthquake are estimated at ≥0.8g.
The Whataroa River is actively eroding the southern edge of the investigation area. Comparison of historic aerial photos and newly obtained LiDAR showed the river bank has moved a total of 165 m since 1948, a majority of that occurring in the past decade, 35 m of erosion occurring over a few days during early January 2011. Little correlation between heavy rainfall periods and increased erosion rates suggest changing channel dynamics play a major part in the channel migration. Modelling of the threshold discharges required to overtop the Whataroa terraces results in return periods several orders of magnitude larger than Alpine Fault earthquake recurrence intervals that result in major sediment pulses,
implying that inundation from river flooding under current channel conditions is highly unlikely.
Debris flows originating from the west valley wall have been identified as a possible hazard to drilling operations. Recent debris flows were easily mapped due to the changes in vegetation, whereas the remnants of historic debris flows were able to be mapped using the LiDAR. Studies of these show that they have a minimal run out distance (<100 m), and can be easily avoided by ensuring the drill site is located outside the proposed debris flow risk zone plus a 50 m buffer that has been added for caution.
Current uncertainty of the fault dip and target depth of the hole causes large variation in proposed drill rig locations at the surface. All of the investigations are summarised on a hazard map used to suggest a range of favoured drill sites based on varied angle dips and drilling depths, minimizing flood, erosion and sediment inundation hazards, and specifying access routes.
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Franklin, Kristel. "A Landslide Risk Management Approach for the Stillwater to Ngakawau Rail Corridor (SNL96 to 126km) in the Lower Buller Gorge, New Zealand." Thesis, University of Canterbury. Geologocial Sciences, 2012. http://hdl.handle.net/10092/6573.
Full textAbstract:
This thesis has examined the 30km long rail corridor through the Lower Buller Gorge, on the Stillwater Ngakawau Line, between SNL96 and 126km, using a landslide risk management approach. The project area is characterised by high annual rainfall (>2,000mm per year), and steep topography (slopes typically ≥20°) adjacent to the rail corridor. The track formation generally follows the natural contour near the base of the hillslope through the Lower Buller Gorge, and consequently involves many curves but relatively limited cut slopes into adjacent rock outcrops. The distance between the base of adjacent hillslopes and rail is frequently <2m horizontally.
A variety of basement and Tertiary lithologies are present, including granite, breccias, indurated sandstone/mudstone, and limestone. The primary focus of this thesis has been on upslope-sourced landsliding onto the rail corridor, and on two short lengths (20m and 450m) that currently have a 25km/hour speed restriction imposed at Whitecliffs and Te Kuha respectively. Rainfall-induced and earthquake-generated landslide triggering mechanisms were examined in detail.
A landslide inventory has been compiled to determine the characteristics and distribution of identified slope failures over time, and to establish any correlation with topography and geology. Sixty individual landslide events were identified since the line became fully operational in the 1940s, based on desktop reviews, and field inspections for more recent events. To reflect the presence of small magnitude landslide events, a project-specific logarithmic classification of landslides was adopted from <10m³ (very small volume) to ≥10,000m³ (very large volume). An absence of a higher proportion of ‘very small’ to ‘small’ landslide volumes (<100m³) in the inventory reflects incomplete reporting of these comparatively lower magnitude, but higher frequency, events. The establishment of a robust landslide inventory to document future events, in a consistent and readily accessible format, is required for continued monitoring and review of landslide risk management practices in the Lower Buller Gorge.
Combining landslide inventory data and physical characteristics of the project area enabled the development of a qualitative landslide zonation map that assigned ‘high’, ‘high-moderate’, ‘moderate’ and ‘low’ landslide susceptibility classes. The principal area of slope instability above the rail corridor is 22.5km in length between SNL103.5 and 126.0km, associated predominantly with basement lithologies (Tuhua Granite; Hawks Crag Breccia; Greenland Group). The most frequently occurring landslides are shallow, typically less than 3m deep, translational failures triggered in regolith or colluvium materials. Rainfall-induced debris slides and flows are dominant, given the high annual rainfall and associated high frequency of high intensity or long duration rainfall events. Very small to medium landslides (<1,000m³) have the potential to impact the rail corridor with an average frequency of around one every two years, causing damage to infrastructure or affecting rail operations. Very large landslides (≥10,000m³) can be expected every 10 to 20 years based on a limited historical record. The narrow rail corridor and absence of sufficient catch areas above or adjacent to the rail causes continual operational challenges due to upslope-sourced landslide debris, and high susceptibility to slope failures, particularly west of SNL103.50km. Development of a rainfall-threshold for proactive inspection of the rail corridor is recommended, including the establishment of a rain gauge network through the Lower Buller Gorge.
Earthquake-generated landslides significantly impacted the rail during the magnitude 7.1 Inangahua earthquake in 1968 and to a much lesser extent during the magnitude 6.1 Westport earthquake in 1991. The rail was not fully constructed through the Lower Buller Gorge at the time of the magnitude 7.8 Buller (Murchison) Earthquake in 1929, which generated widespread landsliding in the Buller and Nelson regions. Earthquake-generated landsliding can be expected through the Lower Buller Gorge from earthquakes of magnitude ≥6, and track inspection is recommended in the event of magnitude 5 or greater earthquakes.
Detailed geological characterisation and mapping at Whitecliffs and Te Kuha was conducted, including a LiDAR survey at Whitecliffs that enabled visualisation of the ground surface without the interference of vegetation. The limestone outcrop at Whitecliffs comprises 60-70m high near-vertical cliffs with a well-established talus apron at the base, extending to the rail corridor. Three widely spaced open fractures sets are present at the top of Whitecliffs that propagate into the cliff-face. There has been no detectable movement on selected key fracture sets since monitoring commenced in 1993 and there is no confirmed evidence of large-scale cliff collapse during the 1968 Inangahua earthquake. Whitecliffs is not as susceptible to failure as other slopes inspected in the project area due to structural controls, primarily being the dipping of strata back into the cliff-face and widely space joint sets. Establishment of inspection protocols for earthquake events impacting the area, including real-time monitoring of selected fractures at Whitecliffs is recommended.
A 2km-length corridor site model produced for Te Kuha demonstrated ‘high’ landslide susceptibility is not confined to slopes above the existing 450m speed restriction zone. Removal of the speed restrictions at Whitecliffs and Te Kuha can be considered, as the increased exposure time is not considered sufficient justification given the extent of other susceptible areas to landsliding affecting the Lower Buller Gorge rail corridor.
The principal conclusion from this thesis project is that there is on-going risk to rail operations predominantly from shallow translational landsliding in regolith-colluvium materials. The majority of these will be generated by long-duration or intense rainfall events. Development of threshold-based methods for effective track management is recommended, including the establishment of a rain gauge network through the Lower Buller Gorge, and landslide inventory database. Site-specific engineering measures could be adopted, such as catch benches or avalanche-type shelters, where justified on a cost-benefit basis.
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Irvine, Janelle Rose Mae. "Sedimentology, stratigraphy and palaeogeography of Oligocene to Miocene rocks of North Canterbury-Marlborough." Thesis, University of Canterbury. Geological Sciences, 2012. http://hdl.handle.net/10092/6826.
Full textAbstract:
The Cenozoic was a time of climatic, tectonic and eustatic change in the Southern Hemisphere. Cooling at the pole, glaciation and substantial sea ice formation occurred as latitudinal temperature gradients increased and tectonics altered Southern Hemisphere circulation patterns. During this same time frame, the tectonic regime of the New Zealand continental block transitioned from a passive margin to an active plate boundary, resulting in the reversal of a long-standing transgression and an influx of terrigenous sediment to marine basins. In this transition, depositional basins in the South Island became more localized; however, the influence of oceanographic and tectonic drivers is poorly understood on a local scale. Here we apply sedimentological, biostratigraphic and geochemical analyses to revise understanding of the effects of the changing climatic regime and active tectonics on the development of Oligocene and Miocene rocks in the Northern Canterbury Basin.
The Late Oligocene to Middle Miocene sedimentary rocks of the northern Canterbury Basin record oceanographic and tectonic influences on basin formation, sediment supply and deposition. The Palaeocene to Late Eocene Amuri Formation in the basin are micrites and biogenic cherts recording deepwater, terrigenous-starved environments, and do not show any influence of active tectonics. The Early Oligocene development of ice on the Antarctic continent and the associated global sea level response is reflected in this basin as the Marshall Paraconformity, an eroded, glauconitized and phosphatised firm ground and hardground atop the Amuri. Sedimentation above this unconformity resumed in the Late Oligocene-Early Miocene with cleaner, deep-water, bathyal planktic foraminifera packstones and wackestones in eastern areas and Late Oligocene inner shelf volcaniclastic packstones in parts of the western basin. Post-unconformity sedimentation resumed earlier in western areas, as the currents responsible for scouring the sea floor moved progressively to the east. The development of tectonic uplift in terrestrial settings is first seen in the northwestern basin in Lower Miocene fine quartz-rich sandstones, and by the Middle Miocene, bathyal sandstones and quartz-rich wackestones appear in the basin, replacing earlier, more pure carbonates. The uplift caused shallowing to the west, in the form of shelf progradation due to sediment influx. This shallowing is not observed to the east; instead, the palaeoenvironments show a deepening as a result of sea level rise.
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Paquet, Fabien. "Evolution morphostructurale des bassins de marge active en subduction : l'exemple du bassin avant arc de Hawke Bay en Nouvelle-Zélande = Morphostructural evolution of active subduction margin basins : the example of the Hawke Bay forearc basin, New Zealand /." Rennes : CNRS, Université de Rennes, 2008. http://library.canterbury.ac.nz/etd/adt-NZCU20080225.224857.
Full textAbstract:
Thesis (Ph. D.) -- l'Université de Rennes, 2007."Thése de Doctorat de l'Université de Rennes 1 réalisée en co-tutelle avec l'Université de Canterbury (Christchurch, Nouvelle-Zélande)." "Soutenue le 9 novembre 2007." Includes bibliographical references. Also available via WWW.
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Adamson, Thomas Keeley. "Structural development of the Dun Mountain Ophiolite Belt in the Permian, Bryneira Range, western Otago, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Geological Science at the University of Canterbury /." Thesis, University of Canterbury. Geological Sciences, 2008. http://hdl.handle.net/10092/1587.
Full textAbstract:
The deformed Permian Dun Mountain Ophiolite Belt (DMOB) forms the basement of the Dun Mountain-Maitai terrane and is traceable through the entire length of New Zealand. The DMOB contains a variably serpentinised mantle portion and a crustal portion containing gabbros, dolerites, cross cutting dikes and extrusives, together they are similar to oceanic crust. The initial crustal portion, however, is atypical when compared to other ophiolites, being thin and lacking a sheeted dike complex, but has well spaced inclined intrusive sheets and sills. At least four post-Permian deformation periods affect the DMOB; collision and rotation during emplacement of the DMOB on the Gondwana margin, compression during Mesozoic orogenies, extensional deformation during the Gondwana break-up and transpressive deformation related to the modern plate boundary through New Zealand. Structural work in the Northern Bryneira Range focused on well preserved outcrops to investigate crustal growth and contemporaneous deformation during the Permian. Structural evidence of Permian deformation was determined by examination of pseudostratigraphy, structures constrainable to the Permian, and the geometric relationships with the overlying Maitai sedimentary sequence. Crosscutting by intrusive phases was used to determine a chronological order of crustal growth and deformation episodes. It was concluded that all deformation was extensional and that two major phases of magmatism were separated by a period of deformation and were followed by ongoing syn-sedimentary deformation during the deposition of the Maitai Group. After removal of Mesozoic rotation, the resulting orientations of paleo-horizontal markers and diverse orientations of intrusive sheets were analysed. Two hypothesises were tested to assess the origin of inclined intrusive sheets: a) that the diverse orientations were the result of tectonic rotation coeval with the intrusion of dikes. b) that primary orientations of the sheets had been diverse. Results show that the sheets were intruded with diverse orientations, probably related to variation in the principle horizontal stress over time. Further rotation of the assemblage of sheets occurred during the last stages of magmatism and during the subsequent period of sedimentation. The last stage probably relates to large scale normal faulting during the development of the sedimentary basin. iii
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Saunders, Katharine Emma. "Micro-analytical studies of the petrogenesis of silicic arc magmas in the Taupo Volcanic Zone and southern Kermadec Arc, New Zealand : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Geology /." ResearchArchive@Victoria e-Thesis, 2009. http://hdl.handle.net/10063/943.
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