Dissertations / Theses: 'Geology, Structural New Zealand'

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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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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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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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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.

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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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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.

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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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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.

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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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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.

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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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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.

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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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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.

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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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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.

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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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11

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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12

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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13

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.

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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.

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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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16

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/.

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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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17

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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18

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.

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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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20

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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22

Pomeroy, A. "A sociological analysis of structural change in pastoral farming in New Zealand." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374723.

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23

Down, Taylor Nicholson. "Structural-stratigraphic reconstruction of the lower Whakataki formation, north island, New Zealand." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/94176/1/Taylor_Down_Thesis.pdf.

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This thesis details a Miocene aged sedimentary rock formation located in north island New Zealand. Mapping, stratigraphic logging and petrographic analysis of the rock formation ascertained that it was deposited in a deep-marine, tectonically active region. The work details the make-up of the sedimentary rocks using geochemistry and microscopy to define their origin. This definition was used to interpret the depositional model of the sediments detailing how they were transported and how they were emplaced.

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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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25

Mason, Russell A. "Structural evolution of the Western Papuan Fold Belt, Papua New Guinea." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/37523.

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New Guinea forms the northern margin of the Australian Plate which is now characterised by a zone crustal deformation and accreted terranes. The present day configuration is the result of global tectonics in the southwestern Pacific since the Triassic. The Papuan Fold Belt is located within Papua New Guinea, the eastern half of New Guinea, and comprises deformed basement, platformal and basinal Mesozoic and Tertiary sediments. Deformation within the fold belt commenced possibly as early as Middle to Late Miocene and is currently continuing. The structure of the western part of the Papuan Fold Belt is characterised by thin skinned thrusting and basement involved structures, the latter attributed to inversion of extensional faults active in the Tertiary and the Mesozoic. Inversion is thought to have post-dated the initiation of thin skinned thrusting by approximately 5 Ma. Continued basement shortening may be due to the current high convergence rate between the Australian and Pacific Plates. The Alice Anticline formed due to inversion of a Tertiary extensional fault system. Three-dimensional restoration of the Alice Anticline makes use of a series of balanced cross-sections and is based on a line length method. Paradoxically, this restoration reveals non-plane strain in the balanced cross-sections upon which it relies. However, the restoration also reveals and quantifies a component of rotation about vertical axes which would not be obvious by application of conventional methods of structural analysis. Two transfer zones associated with the original extensional geometry acted as obstructions to deformation and have effectively pinned contractional structures during their formation causing the rotations about vertical axes. A general fracture system is developed in rocks in the Alice Anticline area. This typically comprises two sets of conjugate shear fractures and a third set, interpreted as extensional, which is sub-nonnal to the acute bisector of the two conjugate sets. Unfolding of bedding using the three-dimensional restoration results in a symmetrical geometric relationship between the general fracture system and folds. The mechanical interpretation of fractures, their geometric relationships and the timing constraints on their formation are consistent with folding. The structure of the Ok Tedi mine area is complicated by the presence of approximately syn-tectonic intrusive bodies. The development of the Parrots Beak and Taranaki Thrusts as floor and roof thrusts respectively constitutes shortening estimates in the mine area which are consistent with those determined regionally. Striation analysis of rnesoscale faults from country rocks in the mine area reveals a reduced stress tensor compatible with the regional shortening direction. Reduced stress tensors determined for the Fubilan Monzonite Porphyry are related to emplacement processes and would be consistent with development of radial and concentric fracture sets.

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26

Nushart, Nathan. "Modeling Intrusive Geometries of a Shallow Crustal Intrusion: New Evidence From Mount Ellsworth, Utah." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5753.

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Surface displacements resulting from upper-crustal intrusion of melt are a paramount concern for communities and facilities located in or near active volcanic areas (e.g. Campi Flegrei, Yucca Mtn.). Study of active intrusions such as Campi Flegrei, Italy west of Mt. Vesuvius, is limited to remote observations through geophysical/geodetic procedures. While the surface displacement due to melt emplacement at depth can easily be determined, the geometries and depth of intrusions are often based on simplified assumptions (e.g. spheres and prolate or oblate ellipsoids). These models benefit from data constraining both the geometries of the individual intrusions, and the kinematics and mechanics of deformation within the superstructure overlying the intrusions. Mount Ellsworth, a partially exposed sub-volcanic system, is an ideal natural laboratory for the study of near surface intrusions. The intrusions of the Henry Mountains are ideal because they were emplaced into relatively flat-lying stratigraphy of the Colorado Plateau, at a time when the stress field was largely isotropic. Previous geologic work done in the Henry Mountains, conducted by C.B. Hunt (1953) and Marie Jackson and Dave Pollard (1988), presents competing emplacement models (i.e. large batch intrusion or incremental sill growth), as well as, differing geologic map data and interpretations. Through a combination of 1:5000 scale field mapping and profile-oriented gravity study, we have produced detailed geologic maps and cross sections of Mt. Ellsworth assess the previous work done on Mt. Ellsworth with new datasets, as well as, evaluate criteria refining various emplacement models. Mapping results demonstrate that several of the assumptions made in models theorized by Hunt (1953) and Jackson and Pollard (1988), were inappropriately applied on Mt. Ellsworth. These assumptions include the thickness and separation of stratigraphic units, the size and distribution of sills and smaller intrusions, structural attitudes of beds and sills, and the presence of exposure of the main body of the intrusion. Gravity data collected on similar intrusions presented in Corry (1988) demonstrates the difficulty of obtaining a gravity anomaly on the wavelength of the assumed size of the intrusion. Forward gravity modeling of various potential geometries beneath Mount Ellsworth suggests that the anomalies are similar in shape with a magnitude between 16 and 20 mGal. Results from the gravity profiles collected for this study fail to predict an anomaly on the wavelength of the Mount Ellsworth intrusion and record a much more complicated anomaly than is presented by the forward models. By combining the stratigraphic data, structural data, and cross sections, it can be determined that the Mount Ellsworth intrusion is a laccolith with a floor 1.5 kilometers beneath the topographic surface, is 1 kilometer thick at its maximum, and has dimensions of 4 kilometers wide by 6 kilometers long.

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27

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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28

Cullen, Andrew Blinn. "The North New Guinea Basin, Papua New Guinea : a case study of basin evolution at a modern accretionary plate boundary /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1990.

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29

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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30

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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31

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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32

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.

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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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33

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.

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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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34

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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35

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.

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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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36

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/.

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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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37

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.

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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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38

Scott, Justin Robert. "Fractal and multifractal fault simulation : application using soft data and analogues at Wyong, New South Wales, Australia /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19562.pdf.

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39

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.

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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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40

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.

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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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41

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.

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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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42

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.

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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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43

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.

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44

Wilson, Paul. "Structural geology, tectonic history and fault zone microstructures of the Upper palaeozoic Maritimes Basin, southern New Brunswick." Restricted access (UM), 2006. http://libraries.maine.edu/gateway/oroauth.asp?file=orono/etheses/37803141.pdf.

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Thesis (Ph.D.) -- University of New Brunswick, Dept. of Geology, 2006.
Title from PDF title page (viewed on May 25, 2010) Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 299-321). Also issued in print.

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45

Harbort, Terrence Anthony. "Structure and tectonic synthesis of the Marlborough block, Northern New England fold belt, Australia /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19092.pdf.

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46

Jones, Emily S. "Strain analysis of lineated gneiss in the Hope Valley shear zone of southeast New England /." Connect to online version, 2005. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2005/104.pdf.

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47

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.

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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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48

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.

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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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MacKenzie, Douglas James, and n/a. "Structural controls on orogenic gold mineralisation in the Otago Schist, New Zealand and the Klondike Schist, Canada." University of Otago. Department of Geology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080704.085108.

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Orogenic gold mineralisation in schist terranes with few or no contemporaneous igneous intrusions is poorly understood. It is proposed in this thesis that the structural evolution of such terranes controls the generation of hydrothermal fluid pathways and thus the location of orogenic mineral deposits. Gold mineralisation in the Otago Schist, New Zealand and the Klondike Schist, Canada occurred in the latter phases of greenschist facies metamorphism as well as after metamorphism during Paleozoic-Mesozoic exhumation. In Otago, gold mineralisation occurred at a number of different times and structural levels as the schist belt was exhumed and rocks were brought up through the brittle-ductile transition. In Klondike Schist, gold mineralisation occurred in relatively brittle rocks after a period of regional compression and crustal shortening caused by the stacking of thrust sheets. Gold mineralisation in both schist belts is not associated with any coeval igneous activity. The earliest stage of gold mineralisation in the Otago Schist occurred in the Jurassic when mineralising fluids were progressively focussed into late metamorphic ductile shear zones such as the Hyde-Macraes Shear Zone (HMSZ), east Otago and Rise and Shine Shear Zone (RSSZ), central Otago. Both of these gold-bearing mineralised zones occur along mappable structural discontinuities or boundaries that separate structurally, metamorphically and lithologically distinct blocks. The HMSZ occurs in the hangingwall of an underlying low angle normal fault that juxtaposes mineralised lower greenschist facies rocks on to unmineralised upper greenschist facies rock. The RSSZ occurs in the footwall of an overlying low angle normal fault that juxtaposes unmineralised lower greenschist facies rocks on to mineralised upper greenschist facies rock. The two shear zones did not form as part of a single homogeneous structure. There are several other prospective late metamorphic boundaries that are different from later brittle faults that disrupt the schist. Late metamorphic gold mineralisation is characterised by both ductile and brittle structures, foliation-parallel shears, disseminated gold with sulphides in deformed schist and minor steeply dipping extensional veins. This style of mineralisation is the most prospective but can be subtle in areas without quartz veins. Hydrothermally altered rocks are enriched in gold, arsenic, tungsten and sulphur with minor enrichment of bismuth, antimony, mercury and molybdenum. Disseminated mineralisation in the HMSZ is associated with hydrothermal graphite however there is no hydrothermal graphite in the RSSZ. The next stage of gold mineralisation occurred in the Cretaceous during post-metamorphic exhumation of the schist belt and is characterised by steeply dipping, fault-controlled quartz veins, silicified breccias and negligible wall rock alteration. Most post-metamorphic veins strike northwest such as the ~25 km long Taieri river gold vein swarm, but there are other stibnite and gold mineralised structures that strike northeast (e.g., Manuherikia Fault system) and east-west (e.g., Old Man Range vein systems). The latest recognised stage of gold mineralisation is controlled by structures related to the initiation of the Alpine Fault in the Miocene and is characterised by steeply dipping quartz veins with abundant ankeritic carbonate in veins and ankeritic carbonate with gold in altered rocks. Hydrothermally altered rocks are enriched in arsenic, carbon dioxide and sulphur with minor enrichment of antimony. Gold-bearing veins at Bullendale, central Otago are of this type and are associated with a broad alteration zone. Gold-silver and gold-silver-mercury alloys occur in both Caples and Torlesse Terranes of the Otago Schist. Almost all mercury-bearing gold occurs in east Otago vein systems and mercury-free gold occurs in central and northwest Otago veins, irrespective of host terrane. There is no relationship between depth of vein emplacement and mercury content of gold. The Klondike Schist was emplaced as a series of stacked thrust slices in the Jurassic and thrust-related fabrics are preserved in all thrust slices. Strongly deformed carbonaceous schist horizons are spatially associated with thrust faults and graphite within these units is concentrated along spaced cleavage surfaces. Kink folding is best developed in the uppermost slices of Klondike Schist and overprints thrust-related fabrics. Gold-bearing veins formed in extension fractures controlled principally by pre-existing weaknesses such as kink fold axial surfaces. Normal faults correlated with a period of Late Cretaceous regional extension crosscut kink folds and offset gold mineralised veins. The main stage of mineralisation occurred after major regional compression and thrust stacking and before Cretaceous normal faulting. Gold-bearing veins are widely dispersed throughout the uppermost slices of Klondike Schist and are considered to be a sufficient source for Klondike gold placer deposits. Disseminated gold with pyrite is associated with gold-bearing veins in some Klondike Schist and this disseminated mineralisation expands the exploration target for these veins. Disseminated gold with pyrite, without quartz veins, occurs in some schist lithologies and is associated with chlorite alteration and weak silicification. The arsenic content of gold-mineralised Klondike Schist is much lower than mineralised Otago Schist and background concentrations of arsenic are much lower in Klondike Schist as well. No shear-related mineralisation has been discovered in Klondike Schist but due to its relatively poor exposure, this belt remains prospective for this style of mineralisation.

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50

Barnes, Philip M. "Structural styles and sedimentation at the southern termination of the Hikurangi subduction zone, offshore North Canterbury, New Zealand." Thesis, University of Canterbury. Geology, 1993. http://hdl.handle.net/10092/4702.

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Abstract:

In the northern region of South Island, New Zealand, a major tectonic transition occurs in the obliquely convergent Australia-Pacific plate boundary. The southern end of the Hikurangi subduction zone terminates against the Chatham Rise, a submerged continental plateau on the Pacific Plate, which is too buoyant to be subducted. Relative plate motion that is accommodated along the Hikurangi margin is transferred by a complex arrangement of faults, to a zone of transpressive, continental collision across the Southern Alps. A detailed study of offshore seismic-reflection profiles, sediment cores and bathymetry from the north Canterbury continental margin and north-western Chatham Rise reveals the complex interactions between late Cenozoic sedimentation and tectonics at the southern termination of the Hikurangi subduction zone. The north Canterbury shelf and the NW Chatham Rise slope are separated by major submarine canyons that link the shelf with the 3000 m-deep Hikurangi Trough. The sedimentary succession beneath the shelf and slope attains a maximum thickness of about 2 km and is inferred to be underlain by Torlesse terrane basement of Mesozoic age. The late Cenozoic stratigraphy of both regions has been established by correlating unconformity-bounded sedimentary units between seismic-reflection profiles, sampling the units in cores from exposures at the seabed, and dating the sediments by foraminifera and nannoflora biostratigraphy. Tectonic structures have been mapped from seismic profiles and the stratigraphy has been used to constrain the structural and sedimentary evolution of each area. The north Canterbury shelf and the NW Chatham slope exhibit contrasting tectonic and sedimentation styles, which reflect differences in proximity to sediment sources, bathymetry, physical oceanography, sedimentation response to global climate cycles and relative sea-level changes, and different stresses imposed on the basement rocks within the plate-boundary zone. Late Quaternary sedimentation patterns on the NW Chatham slope and in the southern Hikurangi Trough have been studied using 3.5 kHz echo-character mapping. The slope is dominated by current-controlled sedimentary processes, whereas turbidite processes characterise the adjacent part of the southern Hikurangi Trough. On the slope north of Mernoo Saddle (a 580 m-deep depression between the South Island shelf and the Chatham Rise) a 160 x 30 km zone of current erosion occurs between 700 m and 2300 m water depths. Within this region are several northeast trending channels, 5-20 km wide and up to 105 km long, scoured obliquely down-slope. These scours are inferred to have been formed by a northward flowing current of Antarctic Intermediate Water passing through the Mernoo Saddle, then braiding as it cascaded down and across the mid-slope before merging again further east into a contour current on the unstable lower slope of the northern Chatham Rise. The lower slope between and below the scours comprises a complex of coalescing sediment drifts. The adjacent Hikurangi Trough is characterised by a canyon and levee-channel system that guide turbidites from the eastern South Island margin and Cook Strait. On the trough floor is a meandering axial channel up to 10 km wide, with a left-bank dominated levee off Cook Strait where the trough widens. Within the down-slope thickening, late Cenozoic succession on the NW Chatham slope there is a stratigraphic change in acoustic impedance that is inferred to mark a change from predominantly carbonate to terrigenous sedimentation in the Late Miocene (c. 9-10 Ma). This change might reflect an increase in uplift and erosion of the Southern Alps at this time. Analysis of 13 unconformity-bounded seismic units of Pliocene-Recent age indicates an episodic history of mid-bathyal (c. 700-2300 m) current erosion and deposition on the NW Chatham slope. Erosion began in the mid-Pliocene and was most widespread in the Late Pleistocene, when several regional scale erosion surfaces developed. The regional extent of the older surfaces differ from the pattern of oblique-to-slope, en echelon, scour channels and associated sediment drifts which are related only to the five youngest depositional units(< 0.25 Ma). All erosional or non-depositional unconformities between the 13 Plio-Pleistocene seismic units resulted from major velocity changes in the northward, mid-bathyal flow over the Mernoo Saddle. Therefore, the sedimentary units and their intervening unconformities have a different origin to sea-level-controlled sequences in the Vail/Exxon stratigraphic model. The eight youngest seismic units are Late Pleistocene and have a cyclicity of about 57-75 ka, which is similar to high-order (40 and 100 ka) glacio-eustatic sea-level cycles. The older units, deposited between Early Pliocene and Late Pleistocene, have a longer frequency of about 750 ka. The similarity of the Late Pleistocene sequence cyclicity to that of high-order glacio-eustatic cycles, together with consideration of the physical oceanography, a recent phase of reduced erosion during the Holocene, and the inferred subsidence history of the region collectively suggest that the paleoceanographic fluctuations causing the sequences are related to high-amplitude Plio-Pleistocene glacial-interglacial climatic oscillations superimposed on the late Cenozoic subsidence of Mernoo Saddle. The north Canterbury inner-middle shelf is underlain by twelve unconformity bounded seismic units of Late Pliocene-Early Pleistocene to Recent age. The units consist predominantly of terrigenous silty mud and thin layers of gravel, which are inferred to have been deposited in c. < 70-80 m water depth predominantly during transgressions and relative highstands of high amplitude, glacio-eustatic sea-level cycles. Erosional unconformities of middle Pleistocene to Recent age have been progressively tilted seaward as a result of contemporaneous coastal uplift and outer shelf subsidence. The north-western corner of the Chatham Rise has been extending by normal faulting since the Late Miocene (c. 8-6 Ma). The North Mernoo Fault Zone (NMFZ) is a 100 x 300 km extensional province that evolved contemporaneously with offshore sedimentation and with the plate-boundary zone in northern South Island. Growth faults are characteristic, but the distribution of faulting has varied temporally; The fault zone is seismically active and consists of a domino-style array of overlapping, southward dipping normal faults which are typically 2-5 km apart and trend roughly east-west at a high angle to the plate-boundary zone. Late Quaternary surface traces are widely distributed on the mid-upper continental slope but many surface scarps are poorly preserved due to extensive erosion of the seafloor. Despite the wide distribution of faulting, late Cenozoic extensional strain is < 2%. The geometry of the NMFZ is partially inherited from older basement structures. Many of the late Cenozoic faults are reactivated Late Cretaceous and Eocene normal faults which developed during periods of widespread extension of the New Zealand region, in tectonic settings different from now. Two possible models for extension of the edge of continental Pacific Plate are considered: (1) lateral buckling of the upper continental crust across the southern termination of the Hikurangi subduction zone; and (2) flexure of the NW Chatham Rise as the region is bent downward into the southern end of the Hikurangi subduction zone. The extensional NMFZ is one of three offshore fault systems that almost merge together over the southern end of the Hikurangi subduction zone. The western end of the NMFZ crosses submarine canyons at the southern end of the Hikurangi Trough and extends to within 20 km of two opposite-verging, NE-trending fold and thrust fault systems on the north-eastern South Island continental margin. One fold and thrust system verges eastward and represents the southern part of the Hikurangi margin imbricated frontal wedge that is deforming the Marlborough continental slope above the southern part of the Hikurangi subduction zone. The other fold and thrust fault system verges north-westward and is deforming the north Canterbury shelf to the west of the NMFZ. In addition to tilting of the north Canterbury shelf, the inner edges of the Plio-Pleistocene units have been progressively deformed since the middle Pleistocene. Gentle, asymmetric folds up to 35 km long are inferred to be developing above the propagating tips of SE-dipping thrust faults. Some structural elements of the fold and thrust system may be reactivated Late Cretaceous extensional faults. The fold and thrust region extends 20 km offshore between central Pegasus Bay and Kaikoura. The north-eastern end of the zone extends to within 20 km of the extensional NMFZ, but these two fault systems are not linked kinematically, Two possible tectonic models for the north Canterbury coastal region are considered. The preferred model involves NW-SE oriented, upper-crustal shortening of much of the north Canterbury region, which is required to accommodate a component of the relative plate motion in northern South Island. A comparison with other obliquely convergent plate boundaries and with other tectonic settings where continental extensional faulting is occurring today, suggests that the style of tectonic interactions at the southern termination of the Hikurangi subduction zone is rare in the world.

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