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1
Belrose, Ashliegh Theresa. "The Champlain Sea/Lake Champlain Transition Recorded In The Northeast Arm Of Lake Champlain, USA-Canada." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/349.
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Sediment accumulated on a lakebed archives information about past climate and changes in the regional environment. Previous studies (Burgess, 2007; Koff, 2011; Palmer, 2012) in the Northeast Arm of Lake Champlain, specifically Missisquoi Bay and Saint Albans Bay, showed a period (~9,400 - 8,600 yBP) of elevated organic matter deposition in both bays, indicating a productive event that pre-dated any possible anthropogenic influence. However, the record was abruptly cut off and any documentation representing the span of time leading up to this event was not found. The elevated organic matter levels were explained as being the result of a warm, dry environment that reduced lake level and promoted productivity within the bay.
A new goal was formulated to lengthen the Holocene record for Missisquoi Bay (MSB) and Saint Albans Bay (SAB) in order to compare paleorecords and capture the span of time leading up to this highly productive event, possibly related to the Champlain Sea/Lake Champlain Transition (~10,000 yBP). One sediment core was taken from each bay as close to the original coordinates as the sediment cores obtained in previous studies (Koff, 2011; Palmer, 2012). The sediment cores were processed in the lab and sediment samples were tested for water content (WC), %C, %N, C:N, and diatom content.
Each bay's sediment record consisted of a distinct marker representing lowest water level, separating a Champlain Sea unit at the bottom and an overlying Lake Champlain unit. A warming climate coupled with low lake level during this time may be the cause of the increase of productivity (%C) associated with the markers in both bays. Between ~8,600 - 9,400 yBP, a distinct marker represented evidence of a wetland in Saint Albans Bay before the onset of Lake Champlain. Diatom content in the wetland sediments indicated a generally shallow oligotrophic and alkaline body of water that shifted back and forth from brackish to freshwater. The record shows the wetland was eventually drowned as water level continued to rise, slowly transitioning into the Lake Champlain unit. Proxy results showed that internal processes within the lake continued to change in response to climatic and environmental drivers until present day conditions were reached.
At ~9,400 yBP in Missisquoi Bay, there is an erosional unconformity between the Champlain Sea and Lake Champlain units, which corresponds to the low water levels also inferred from the SAB record during that time. After this unconformity, %C results show production within MSB fluctuated, similar to SAB, in response to changing climate and water levels until the present-day conditions of Lake Champlain were established.
In sum, MSB and SAB each contain evidence of an ancient shoreline marker in different forms. Both markers indicate that lowest water levels occurred ~9,400 yBP and that lake level has risen ~7 - 8.5 meters since that time. The rise in lake level is associated with the transition into Lake Champlain. This Champlain Sea/Lake Champlain Transition lasted from ~9,400 yBP until ~8,600 yBP. Therefore, the oldest Lake sediment in the Northeast Arm of Lake Champlain is only 8,600 yBP.
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Wolf, David Eny. "The Burntside Lake and Shagawa/Knife Lake shear zones : deformation kinematics, geochemistry and geochronology; Wawa Subprovince, Ontario, Canada." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/d_wolf_010807.pdf.
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Bullock, Michelle. "Holocene sediments and geological history, Woolley Lake, near Beachport, South Australia /." Adelaide : Thesis (B. Sc.(Hons)) -- University of Adelaide, Dept. of Geology and Geophysics, 1994. http://web4.library.adelaide.edu.au/theses/09SB/09sbb938.pdf.
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Green, George Meredith 1964 Carleton University Dissertation Geology. "Detailed sedimentology of the Bowser Lake group, northern Bowser basin, north-central British Columbia." Ottawa.:, 1992.
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Muehlberg, Jessica M. "Geology of the Tahoe City sub-basin, Lake Tahoe, California-Nevada." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442871.
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Burbidge, Susan M. (Susan Margot) Carleton University Dissertation Earth Sciences. "Holocene environmental history of lake Winnipeg; thecamoebians and stable lead isotopes." Ottawa, 1997.
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Goodacre, Ian Robert. "Microbial carbonates in lacustrine settings : an investigation into the Carboniferous East Kirkton Limestone." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=130768.
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The East Kirkton Limestone outcrops in the Bathgate Hills area of central Scotland. The deposit is Visean (Lower Carboniferous) in age and is the site of a tropical freshwater lake set within a richly vegetated volcanic terrain. The succession consists of an unusual sequence of laminated, spherulitic and massive limestone beds, interbedded with thin mudstones, siltstones and abundant volcaniclastic horizons. This study investigates the palaeoenvironment of the East Kirkton lake, and for the first time presents convincing evidence for the presence of hot springs at East Kirkton. Two distinct mounds of massive limestone are located at the north end of the East Kirkton quarry and are interpreted as hot spring vent deposits. Calcite samples from the Lower Mound have light δ18OPDB values consistent with precipitation at elevated temperatures ranging from 45°C to 80°C, whereas samples from the laminated lake sediments have heavier δ18OPDB values, consistent with precipitation at lower temperatures. The East Kirkton Limestone is unique because it contains a variety of unusual radial fibrous calcite (RFC) precipitates, including mm-sized spherules, oncoids, and laminated botryoidal accretions. These are found within the laminated limestone and also within the Lower Mound of massive limestone, and many of them contained filamentous and cellular microbial remains and are within the definition of microbial carbonates. This study provides good evidence for a microbial involvement in the formation of the East Kirkton laminated accretions. A study of modern stromatolites from Lake Tasek Dayang Bunting, Malaysia highlights close similarities with the East Kirkton accretions in terms of morphology and microstructure. Both have a nodular growth morphology and laminated interior consisting of layers of radial fibrous carbonate botryoids interspersed with organic-rich micritic laminae. The modern stromatolites are covered by a microbial community comprising filamentous bacteria and cyanophytes, plus diatoms and associated mucilage, and microbes are thought to have played an essential role in the morphogenesis of both the modern and ancient examples.
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Kahmann-Robinson, Julia A. Atchley Stacy C. "The sequence stratigraphic evolution of the Sturgeon Lake bank, central Alberta, Canada and its regional implications." Waco, Tex. : Baylor University, 2005. http://hdl.handle.net/2104/3016.
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Lee, Ting Jennifer. "Holocene evolution of a hypersaline lake Lagkor Tso, western Tibet /." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39634140.
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Hartley, Kelley A. "Stratigraphic anaylsis [sic] of areal discontinuities of late Wisconsinan till sheets near Conneaut Lake, northwestern Pennsylvania." Akron, OH : University of Akron, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1248371875.
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Thesis (M.S.)--University of Akron, Dept. of Geology, 2009."August, 2009." Title from electronic thesis title page (viewed 10/21/2009) Advisor, John P. Szabo; Faculty readers, Linda Barrett, LaVerne Friberg; Department Chair, John P. Szabo; Dean of the College, Chand Midha; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Kraft, Matthew. "From Sea To Lake: The Depositional History Of Saint Albans Bay, Vt, Usa." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/857.
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Sediment accumulated in lakes stores valuable information about past environments and paleoclimatological conditions. Cores previously obtained from Saint Albans Bay, located in the Northeast Arm of Lake Champlain, VT record the transition from the Champlain Sea to Lake Champlain. Belrose (2015) documented the presence of a peat horizon separating the sediments of the Champlain Sea from those of Lake Champlain. Initially, this layer was thought to comprise the transition from the marine environment of the Champlain Sea to a freshwater wetland. However, based on the results from this study, the transition between marine and freshwater conditions is thought to be represented by an erosional unconformity, indicative of a lowstand at the end of the Champlain Sea period.
For this study, five additional cores were collected from Saint Albans Bay along a transect following the long axis of the bay moving into progressively deeper water. These cores better constrain the spatial extent, thickness and age variability of the peat layer within the bay and allow us to better understand the environmental conditions that preceded the period of peat deposition. In each of the cores there is evidence of sediment reworking in the uppermost Champlain Sea sediments, indicated by the presence of coarse-grained sediment, which is suggestive of a lowstand at the end of the Champlain Sea period before the inception of Lake Champlain. This coarse-grained layer is immediately overlain by a thick peat horizon. The widespread occurrence of the peat layer points to a large wetland that occupied the entire inner portion of Saint Albans Bay, and lake level ~ 9 m lower than at present during the Early Holocene.
Based on radiocarbon dating, this paleo-wetland existed in Saint Albans Bay from ~ 9,600-8,400 yr BP. The development of this wetland complex is time transgressive, reflecting rapidly increasing lake level during the Early Holocene. This hypothesis is supported by the basal peat radiocarbon dates, as well as by the composition of plant macrofossils recovered from the peat horizons. The shift from peat deposition to fine-grained, low organic content lacustrine sedimentation is believed to have occurred at ~8.6-8.4 ka and is likely the result of continued isostatically driven lake level rise coupled with a changing climate.
Although it was not its primary focus, this study also seeks to address the variations in sediment composition in the Lake Champlain sections of the cores. Evidence from the Lake Champlain record in Saint Albans Bay indicates that there were notable fluctuations in sedimentation, which were likely linked to both climatic variations and a change in the morphology of the bay. The rebound in productivity from ~8-5 ka is likely the result of warmer conditions during the Hypsithermal period. An increase in terrigenous sedimentation during this same time suggests a change in the morphology of the bay in which the Mill River delta migrated towards the inner bay. Initially, the cooler conditions of the Neoglacial are reflected in Saint Albans Bay by a decrease in organic matter content from ~5-3 ka. During the latter part of the Neoglacial (~3-1 ka), increases in organic matter content and detrital input point to enhanced productivity in response to increased precipitation and runoff from the watershed. The most recently deposited sediments in Saint Albans Bay bear out the legacy of anthropogenic nutrient enrichment of the bay in the form of increased algal productivity.
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Arthur, Andrew John. "Mesozoic stratigraphy and paleontology of the west side of Harrison Lake, southwestern British Columbia." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27794.
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A well preserved, fossiliferous Middle Triassic to Early Cretaceous section lies on the west side of Harrison Lake in the southern Coast Mountains. The study of this area involves a re-evaluation of the stratigraphic nomenclature first described by Crickmay (1925, 1930a) together with a lithologic description of the units and age determinations based on collected, identified and described fossils by the writer. Discussions on the biostratigraphy, paleogeography, regional correlations and structure of the thesis area and an overview of the regional tectonics of southwestern British Columbia and northwestern Washington, help to better understand the relation of this Mesozoic section to other rock assemblages in this geologically complex region.
The oldest unit, the Middle Triassic Camp Cove Formation, comprises conglomeratic sandstone, siltstone and minor volcanic rock. Unconformable7 overlying this unit is the Toarcian to Early(?) Bajocian Harrison Lake Formation, divided into four distinct members by the writer, Celia Cove Member (basal conglomerate), West Road Member (siltstone, shale), Weaver Lake Member (flows, pyroclastic rocks, minor sediments) and Echo Island Member (interbedded tuff, siltstone, sandstone). Thickness of this formation is estimated at 3000 m. A hiatus probably is present between this unit and overlying shale, siltstone and sandstone of the Early Callovian Mysterious Creek Formation which is 700 m thick. Conformably above this are 230 m of sandstone and volcaniclastic rock of the Early Oxfordian Billhook Creek Formation. Late Jurassic fluvial conglomerate, sandstone and siltstone of the Kent Formation, perhaps 1000 m thick south of Harrison River, unconformably(?) overlies the last two units mentioned. Berriasian to Valanginian conglomerate and sandstone, 218 m thick, of the Peninsula Formation overlies the Billhook Creek Formation with slight angular unconformity. The Peninsula Formation is conformably overlain by tuffaceous sandstone, volcanic conglomerate, crystal tuff and flows of the Valanginian to Middle Albian Brokenback Hill Formation which is several km thick. Nine Jurassic ammonite genera are identified and described in this report. Triassic radiolaria and conpdonts and Cretaceous ammonites and bivalves are also present in the section.
The most significant structure in the thesis area is the post-Albian to pre-Late Eocene Harrison Fault which strikes north-northwest through Harrison Lake, separating the Mesozoic section along the west side from the northern extension of the Cascade Metamorphic Core on the east side of the lake. A strong sub-horizontal stretching lineation within the fault zone may indicate right-lateral strike-slip movement.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Hughson, Robert Carl. "Upper silurian carbonates of Lake Memphremagog and lime ridge areas, Quebec." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63996.
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Friedman, Richard M. "Geology and geochronometry of the eocene Tatla Lake metamorphic core complex, western edge of the intermontane belt, British Columbia." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28780.
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The Tatla Lake Metamorphic Complex (TLMC) underlies 1000 km² on the western side of the Intermontane Belt (1MB) northeast of the Yalakom fault Three fault-bounded lithotectonic assemblages are recognized in the area studied: an amphibolite grade gneissic and migmatitic core, structurally overlain by a 1 to 2.5 + km-thick zone of amphibolite and greenschist grade mylonite and ductilely sheared metamorphic rocks, the ductilely sheared assemblage (DSA), which is in turn structurally overlain by weakly deformed to unstrained subgreenschist grade rocks of the upper plate which flank the TLMC on three sides.
Structures in the gneissic core include a gneissic foliation and schistosity (Sic), which has been deformed by west to northwest-trending tight to isoclinal folds (F2c). Tectonic fabrics observed throughout the DSA which formed during Ds deformation include a gently dipping mylonitic foliation (Ss), containing a mineral elongation (stretching) lineation (Ls) which trends towards 280° ± 20°. Minor folds of variable trend (Fs), almost exclusively confined to DSA metasedimentary rocks, are interpreted as coeval with ductile shear. Vergence of these folds defines movement sense and direction of top towards 290° ± 20°. Kinematic indicators from DSA rocks which have not been deformed by syn-ductile shear folds indicate a top-to-the-west sense of shear while those deformed by Fs folds yield conflicting results, with a top-to-the-west sense predominating. The entire lower plate comprising the TLMC has been deformed by broad, upright, west to west-northwest trending, shallowly plunging map-scale folds (F3) during D3, which deform Sic and Ss surfaces. The steeply dipping, northwest-trending Yalakom fault truncates all units and structures of the TLMC. Gently to moderately dipping normal faults of Ds and post-D3 relative age are the southern and eastern boundaries between DSA upper plate rocks and 1MB lower plate rocks.
U-Pb zircon dates from igneous arid meta- igneous rocks from the lower plate range from Late Jurassic (157 Ma) through Eocene (47 Ma). These dates bracket the timing of Cretaceous (107 Ma to 79 Ma, in the core) and Eocene (55 Ma to 47 Ma, in the DSA) deformation and metamorphism in the lower plate. Biotite and hornblende K-Ai dates of 53.4 Ma to 45.6 Ma for lower plate rocks are in sharp contrast to Jurassic dates from nearby upper plate rocks; they record the uplift and cooling of the TLMC.
Whole rock initial ⁸⁷Sr/⁸⁶Sr ratios (and for most samples present-day values) of less ≤0.704 have been determined for igneous and meta-igneous rocks of the TLMC; such values are typical of magmatic arc rocks of the 1MB and Coast Plutonic Complex of B.C.
Whole rock major and trace element chemistry of lower plate igneous and meta-igneous rocks indicate sub-alkaline, calcalkaline, volcanic arc affinities.
Garnet-biotite temperatures (interpreted as Eocene in age), from pelitic schist in the southern part of the DSA increase from about 400 ± 50 to 650 ± 50 C with increasing structural depth. A GT-BI-QZ-Al₂SiO₅ pressure of 8 ± 3 kb has been calculated for one of these samples. A T-P of 650 ± 50 C and 5.3 ± 3 kb, calculated from inclusions and garnet cores in a small pelitic pendant in the northwest part of the DSA, reflects conditions during intrusion of the surrounding 71 ± 3 Ma igneous body. A pressure of 7.2 ± 1.4 kb, based on the total Al in hornblende, has been calculated for this body.
Cretaceous ductile deformation in the gneissic core may be related to folding and thrusting which occured in high level rocks to the west and east of the field area. During Early Eocene time (55-47 Ma) the TLMC acquired the characteristics of a Cordilleran metamorphic core complex. Mylonites of the DSA were emplaced by faulting beneath weakly deformed, low metamorphic grade rocks of the upper plate. Synchronously, metamorphic rocks of the gneissic and migmatitic core of the TLMC were moved to higher crustal levels along the footwall of the DSA normal ductile shear zone. The formation of F3 folds and final uplift of the TLMC (47-35 Ma) is postulated to be the consequence of transpression related to later Eocene dextral motion along the Yalakom fault
The TLMC has structural style and timing of deformation similar to metamorphic core complexes in southeastern B.C. Local and regional evidence is consistent with the formation of the TLMC in a regional extensional setting within a vigorous magmatic arc.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Cunderla, Brent Joseph. "Stratigraphic and petrologic analysis of trends within the Spencer Formation sandstones : from Corvallis, Benton County, to Henry Hagg Lake, Yamhill and Washington counties, Oregon." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/3588.
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Within the thesis study area Spencer Formation arkosic/arkosic lithic sandstone lithofacies of Narizian age crop out in a sinuous north-northwesterly band from the Corvallis area into the Henry Hagg Lake vicinity ten kilometers southwest of Forest Grove, Oregon.
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Hartley, Kelley A. "Stratigraphic Analysis of Areal Discontinuities of Late Wisonsinan Till Sheets Near Conneaut Lake, Northwestern Pennsylvania." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1248371875.
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Metcalfe, Elisabet Joan. "Late-glacial through Holocene Stratigraphy and Lake-level Record of Rangely Lake, Western Maine." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/MetcalfeEJ2007.pdf.
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Drakos, Peter S. "Tertiary stratigraphy and structure of the southern Lake Range northwest Nevada assessment of kinematic links between strike-slip and normal faults in the northern Walker Lane /." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442868.
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Lee, Ting Jennifer, and 李婷. "Holocene evolution of a hypersaline lake: Lagkor Tso, western Tibet." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39634140.
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Rey, Kevin A. "Insights into the Early Transgressive History of Lake Bonneville from Stratigraphic Investigation of Pilot Valley Playa, UT/NV, USA." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3803.
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Multiple shallow sediment cores were obtained from Pilot Valley playa, a sub-basin located in the northwestern Bonneville basin. Analysis of stratigraphy, ostracodes, mineralogy, chemistry, total inorganic carbon (TIC), total organic carbon (TOC), and stable isotopes were performed to better place these sediments into proper context with respect to the Lake Bonneville cycle. Results showed Pilot Valley playa contains a nearly full sequence of Lake Bonneville deep-water marl in addition to sediments deposited before and after the Lake Bonneville cycle. Within the marl is a sequence of organic rich algal laminated marl correlated with the Stansbury oscillation. Four 14C ages ranging from ~22.4 k 14C years to ~15.8 k 14C years from preserved algae filaments in this sequence place it well within the time frame of the Stansbury oscillation. Oolitic sand found below this sequence indicates the existence of a shallow (<~5 m), saline lake in Pilot Valley prior to the transgression of Lake Bonneville. Analysis of sediments deposited during the late regressive phase of Lake Bonneville indicates the lake may have fallen to levels below that of Pilot Valley prior to transgressing to the Gilbert level.
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Muiruri, Veronica Mwihaki. "Late Quaternary diatom and palynomorph stratigraphies and palaeoenvironments of the Koora Graben and Lake Magadi Basin, Kenya Rift Valley." HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/461.
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Two sets of cores were recovered from the southern Kenya Rift (Koora and Magadi basins) through the Hominid Sites and Paleolakes Drilling Project and the Olorgesailie Drilling Project. These contain a detailed environmental Quaternary history with records of up to ~1 million years. This period correlates with much of the Olorgesailie Formation record of 1.2 Ma in the Olorgesailie Basin. The Magadi cores reached trachyte at ~ 194 and 133 m with this project focussed on the longer core, MAG14-2A, which includes limestone, zeolitic, laminated and massive clay and silt, massive mud, chert, trona, gravel and sand. The Koora Core (OLO12-1A) extended to depths of 166.14 m and contains laminated and massive diatomites, fine to coarse sands; lime and siliciclastic muds with pumice-rich gravels. The two cores are particularly important because they provide environmental records that help to fill erosional gaps in the history of the Olorgesailie Basin, which includes important evidence for changing hominin cultures and evolution. The high-resolution lacustrine-terrestrial stratigraphies of the two basins have shown how landscapes were transformed because of complex interactions between tectonic and climatic processes. Volcanism also had a significant impact, partially damming lakes at Olorgesailie. Diatoms are present in much of the Koora Basin sequence and large parts of the Magadi sediments. These are dominated by a variety of planktonic Aulacoseira, Cyclotella and Thalassiosira taxa in both basins. Species comprising these genera and other planktonic, benthonic and epiphytic taxa preserve a detailed record of lakes that fluctuated in depth, extent and chemistry. The data document the presence of freshwater and saline lakes as well as wetlands. Diatom transfer functions from the Koora and Magadi basins indicate that these water bodies fluctuated widely in conductivity between ~200 to >20,000 µs cm−1, with pH changing between about 7.5 and 11.5. The palaeolakes also periodically exceeded diatom tolerance limits and intermittently dried out. Pollen are generally lacking in the Koora basin sediments, but deposits in the Magadi core contain common pollen that document a wide range of habitats, including forests, woodlands and grasslands that could have supported the presence of hominins and their activities in the region. Fungal spore data support pollen inferences and indicate periods when large mammals might have been common. The microfossil record shows that there was a broad trend towards more arid conditions in the southern Kenya Rift after about 510 Ka, interrupted by periodic wetter conditions. A major episode of desiccation developed between about 450 Ka to 400 Ka that partially correlates with a period of mammal extinctions and a change from Acheulean to Middle Stone Age toolkits in the Olorgesailie Basin, suggesting that these changes might have been related to environmental conditions at that time.
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De, Deckker P. "Australian Quaternary studies : a compilation of papers and documents submitted for the degree of Doctor of Science in the Faculty of Science, University of Adelaide /." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdd299.pdf.
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Cavas, Matthew P. "THE QUATERNARY GEOLOGY AND SEQUENCE STRATIGRAPHY OF THE LAKE BONNEVILLE DEPOSITS IN THE MATLIN QUADRANGLE, BOX ELDER COUNTY, NORTHWESTERN UTAH." Ohio University / OhioLINK, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1080586528.
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Bloodgood, Mary Anne. "Deformational history, stratigraphic correlations and geochemistry of eastern Quesnel terrane rocks in the Crooked Lake area, east central British Columbia, Canada." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26170.
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The Eureka Peak are lies within the Quesnel terrane of the Intermontane Belt, adjacent to the Omineca Belt - Intermontane Belt tectonic boundary. It represents a convergent zone between the arc related Quesnel terrane and parautochthonous Barkerville terrane. The terrane boundary is defined by the Eureka thrust
Underlying the area are middle Triassic to early Jurassic sedimentary and volcanic rocks, represented by the Quesnel River Group and Takla Group, respectively. Petrologic and geochemical studies of the Takla Group volcanics suggest protoliths of island arc and marginal basin affinities. The Quesnel terrane structurally overlies Hadrynian to early Paleozoic metasediments of the Snowshoe Group (Barkerville terrane). The base of the Quesnel terrane is marked by mylonitized mafic and ultramafic rocks of the Crooked Amphibolite.
Correlation of features across the plate boundary has established the structural continuity in the region, and recognition of structural phases common to both terranes which developed in response to plate convergence. The deformational history involves two phases of coaxial folding of a mechanically heterogeneous lithologic sequence, accompanied by extensive pressure solution, and later overprinting by NW trending extensional fractures. Synchronous to F₁, detachment surfaces developed along major stratigraphic contacts due to contrasting Theologies of adjacent lithologies. Second phase deformation established the regional map pattern, folding the detachment surfaces and the tectonic boundary.
Synchronous to deformation, regional metamorphism is evidenced by the growth of minerals characteristic of amphibolite fades in the Barkerville terrane, and greenschist fades in the Quesnel terrane. Dissipation of heat from the underlying sequences is suggested by the rapid transition in metamorphic grade observed across the boundary. Cleavage surfaces have acted as a locus along which pressure solution has occurred, providing a pathway for the escape of fluids generated during metamorphism. Deposition of material within extensional fractures occurred throughout the deformational history. Fracturing is prominent adjacent to the Quesnel River Group and Takla Group contact, where the viscosity contrast between the two lithologies provided an effective barrier to extensive fluid flow. Concentration of fluids along the contact may have had a buoying effect on the volcanics, allowing furter eastward translation during deformation.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Pickett, Clarence. "A sedimentary facies analysis of the >2.8 Ga Beniah and Bell Lake formations, Slave Province, Northwest Territories." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2002. http://theses.uqac.ca.
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Arzuman, Sadun. "3-D structural and seismic stratigraphic interpretation of the Guasare-Misoa Interval, VLE 196 Area, Block V, Lamar Field, Lake Maracaibo, Venezuela." Texas A&M University, 2002. http://hdl.handle.net/1969/557.
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Loope, Henry Munro. "Deglacial chronology and glacial stratigraphy of the western Thunder Bay lowland, northwest Ontario, Canada." Connect to Online Resource-OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1172777038.
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Chandler, Matthew R. "The Provenance of Eocene Tuff Beds in the Fossil Butte Member of the Green River Formation of Wyoming: Relation to the Absaroka and Challis Volcanic Fields." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1517.pdf.
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Carbaugh, Joyce E. "Cretaceous and Paleogene sedimentary units on the northern Fish Lake Plateau, central Utah /." 2009. http://hdl.handle.net/10288/1231.
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Wartes, Marwan A. "Sedimentary evolution of Permian lacustrine and associated deposits southern Junggar and Turpan-Hami basins, northwestern China /." 1999. http://catalog.hathitrust.org/api/volumes/oclc/44731762.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1999.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 60-77).
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Mackenzie, Leonard M. "Geology, geochemistry and metallogeny of the Burnt Lake area, central mineral belt, Labrador, Canada /." 1991. http://collections.mun.ca/u?/theses,95852.
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North, Jon W. "The stratigraphy, structure, geochemistry, and metallogeny of the Moran Lake Group, Central Mineral Belt, Labrador /." 1988. http://collections.mun.ca/u?/theses,144638.
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Brace, Terry D. "Geology, geochemistry and metallogeny of the Archean Florence Lake Group and associated ultramafic and trondhjemitic rocks, Nain Province, Labrador /." 1990. http://collections.mun.ca/u?/theses,71595.
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Chen, Xiang-Yang. "Lake Amadeus, Central Australia : modern processes and evolution." Phd thesis, 1989. http://hdl.handle.net/1885/109327.
Full textAbstract:
Lake Amadeus, a large saline piaya 120 km long and up
to 12 km wide, forms a major feature of arid Central
Australia. Surrounded by stabilized dunefields, it has
been selected here as the site for a range of historic and
process oriented studies.
The Amadeus piaya is today a groundwater controlled
system of a type largely unrepresented by detailed studies
elsewhere in Australia. Moreover, it lies in an area from
which Late Cenozoic environmental data remain sparse.
With its associated variety of stabilized gypsum and
quartz dunes associated with saline sedimentary facies, it
provides sensitive indicators of past arid depositional
events.
Analyses of the stratigraphic and chronologic record
are supplemented by detailed studies of modern hydrologic,
chemical and sedimentary processes. These provide the
framework controls within which interpretations of the
past record are reconstructed.
Field work was carried out during winter and spring
seasons in 1984, 1985 and 1986. Four 15m cores and more
than 20 short cores up to 1.7m long were taken. Across
the piaya and its marginal land, groundwater, shallow
stratigraphy and sediments were studied by piezometers,
trenches and auger holes. Evaporation was measured with a
method of sediment blocks. Palaeomagnetism and
thermoluminescence dating methods were used to establish
the piaya chronology. Thin section, chemical, mineral and texture analyses help in evaluation of the sedimentary
facies assemblage.
The Cenozoic sediments are divided into two major
units: Uluru Clay in lower part and the overlying Winmatti
Beds. The Uluru Clay sequence, at least 60m thick,
overlies Proterozoic dolomitic limestone. Of uniform
lithology, it consists of clay horizons with minor
intercalated gypsum. The Clay was deposited in a shallow
lacustrine and fluvial enviroument with periodical saline
and frequently dry conditions. The basal Uluru Clay is
estimated to be over 5 Ma old. The transition from
Tertiary to Quaternary, coincident with the Gauss/Matuyama
palaeomagnetic boundary, occrred within the uniform Uluru
Clay sequence.
The Winmatti Beds comprise the top several metres of
basin sediments. The beginning of Winmatti Beds coincides
probably with Jaramillo subchrone (0.91 Ma). The
appearance of gypsum-clay laminae, thick gypsum sands and
aeolian quartz, characteristic of the Winmatti Beds, marks
the onset of a new sedimentary and climatic environment.
In this the dominance of saline groundwater marks the
first development of a groundwater discharge playa system.
The association with aeolian deposits signals the
dominance for the first time of major aridity.
On the landward margin, two rings of gypseous dunes
and associated quartz dunes represent facies equivalent of
arid units in the playa. The older gypseous dune possibly
formed soon after the Uluru Clay. The younger gypseous
dune is correlated with a gypseous clayey sand layer within the Winmatti Beds. The gypseous dunes were
deposited by deflation of near-shore gypsum accumulating
in the groundwater seepage zone during a period of high
watertable.
The hydrologic and climatic history since the younger
gypseous dune formation is correlated broadly with events
identified in Southern Australia. The younger gypseous
dune formed around 45 to 60 Ka B.P. (TL dates), when a
high regional watertable was associated with a wetter
climate. A period of regional dune activation followed
the younger gypseous dune formation resulting in an
aeolian sand deposit in the playa and the thick quartz
sand mantle on the gypseous dunes. This represents a
drier and windier period which may correlate with the low
water level period of 25 to 16 Ka in Southern Australia.
The deposition of shallow water gypsum layer, which
comprise marginal terraces and low terrace islands,
represents a relatively high water level period. This may
correlate with the relatively high water levels of
Holocence time in Southern Australia.
The chronology and stratigraphy predating the younger
gypseous dune remain unclear. They are complicated by
major breaks in the depositional record. Groundwater
bevelling, deflation and soil formation help explain the
hiatuses and low rates of deposition.
A new surface feature is identified which has both
morphologic and stratigraphic expression. Termed GYPSUM
GROUND it comprises a large area of the playa surface. A
brown undulating salt encrusted surface developed over a nearly pure layer of sand-sized gypsum lies some 40 cm
above the local watertable and above the level of periodic
annual flooding. Thin section and detailed sedimentologic
studies establish this as a degradational remnant of a
previously more extensive gypsum sand associated with a
high watertable environment equivelant to the deposition
of gypsum marginal terraces and low terrace islands.
The gypsum ground, now largely independent of
groundwater evaporative processes, is one of three
morphologic and sedimentary units recognized as
characterising the modern playa surface. The other two at
lower surface altitude, salt flat and sulphide lowland,
are controlled by a combination of groundwater and surface
interactive processes.
Evaporation pattern for the playa surface are divided
into two types. One represents a very low rate from the
encrusted surface (El phase); the other is a much higher
evaporation phase after the crust is dissolved by rain (E2
phase). Evaporation of the El phase is estimated to be of
the order 70mm/y. Since all rain water is not totally
evaporated during the E2 phase, this value (El) can only
be used as an upper limit for net evaporation, the
difference between the total evaporation and the rain
water on the surface. The quantity of rainfall not
evaporated during E2 phase (therefore a recharge
component) seems to be significant compared to the annual
El evaporation. Therefore, the net evaporation and
discharge rate may be very low, consistent with a very low
salt concentration rate in the system. This evaporative regime provides new insights into the
question of evaporite formation in a context where the
absence of salts seems anomalous when considered in the
light of present processes.
The playa lacks any substantial salt deposits (other
than gypsum and glauberite), either on the surface or in
the sediment column, eventhough it has been experienced
saline conditions. The surficial salt crusts are commonly
1 cm thick and never exceed 5 cm although the watertable
remains in the capillary fringe and the groundwater is
highly saline (250g/l). The total quantity of dissolved
salts in the groundwater pool are less than expected from
present processes considering the long existence of the
saline phase.
The thin salt crusts on the surface today are
ephemeral being subject to periodic dissolution and
reformation. Crusts cannot develop to a significant
thickness because of combined low net evaporation,
leaching by.rainfall, possible downward ionic diffusion
associated with groundwater body unsaturated with respect
to sodium chloride.
Groundwater salinity has probably never exceeded
chloride saturation due to a combination of processes
including slow chemical concentration rates, processes of
groundwater body expansion, past salt loss through
deflation and salt leakage by deep groundwater outflow
during early Quaternary or even Tertiary time.
The priciple of simplistic uniformitarian
interpretations is once more called into question by these studies. In its Quaternary hydrologic history, the
groundwater discharge playa, today delicately balanced
between discharge and recharge regime, has sometimes
existed as a prolonged groundwater recharge zone as
evidenced by fossil soils with vegetative biotubule
remnants. Thus the present hydrologic processes are not
representative of past regimes emphasizing the dangers of
using modern processes as analogues for past regimes.
The data confirm that Lake Amadeus has rarely operated
as a true surface water lake since Tertiary time. The
groundwater processes and history demonstrated here
provide a new basis for understanding playa systems both
here and in comparable arid to semi-arid regions of low
relief elsewhere in the world.
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Jackson, Valerie A. "Metamorphic and structural evolution of Archean rocks in the Keskarrah Bay Area, Point Lake, District of Mackenzie, N.W.T. /." 1989. http://collections.mun.ca/u?/theses,128344.
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English, Pauline M. "Cainozoic evolution and hydrogeology of Lake Lewis Basin, Central Australia." Phd thesis, 2001. http://hdl.handle.net/1885/109603.
Full textAbstract:
Research in Lake Lewis basin in central Australia has investigated the geology,
geomorphology and hydro geology of this intermontane Cainozoic basin that overlies
the Proterozoic Arunta Craton. The evolution of the area from before Tertiary basin
inception to the present-day has been examined.
Observations of the structural architecture of the basin have been integrated with models
for intracratonic basin evolution, involving reactivation of ancient basement faults. Prior
to basin inception, the Palaeozoic and Mesozoic landscape was a highly irregular
topography of steep bedrock ranges, valleys and inselbergs. Analysis of geophysical and
sedimentological data has enabled reconstruction of the patterns of Tertiary infill within
the 200 m deep basin. Lacustrine sedimentation dominated the Palaeogene, infilling a
deep structural trough north of the MacDonnell Ranges. Subsequent sedimentation
during the Neogene involved accumulation of thick alluvial fan deposits over the basal
clay, with the lacustrine depocentre moved northward to the present site of Lake Lewis.
A drying phase occurred towards the end of the Tertiary, when fluvial and lacustrine
sediments were calcretised, then silicified.
At least 80 m of lacustrine clay, the Anmatyerre Clay, accumulated in Lake Lewis in the
Neogene-Pleistocene. This uniform clay was deposited in perennial lakewaters, infilling
depressions in the heterogeneous basement topography. The Anmatyerre palaeolake was
probably an overflow lake during most of its history, with westward outflow at 570 m
AHD (Australian Height Datum). The catchment was evidently highly efficient in
delivery of runoff from the mountains to the lake and no depositional breaks are
apparent. This lake, at its maximum capacity, was up to 19 m deep and covered an area
in excess of 3,000 km²
, over 12 times the size of the present playa. The BrunhesMatuyama
palaeomagnetic polarity reversal (780 ka) is identified in the Anmatyerre
Clay at 8 m depth beneath the playa surface.
A major switch in sedimentation style followed the Anmatyerre lacustral phase, with
hydrologic closure of the basin during more arid conditions. The Early Tilmouth beds
were deposited in a <9 m deep lake, the Tilmouth palaeolake, that extended to the 560
m AHD level and covered an area of >l375 km²
, 5.5 times the size of the present playa. Hydro logic closure of the basin and high evaporation rates resulted in accumulation of
solutes in the system. Saturation with respect to CaC03 and CaS04.2H20 was reached
and large volumes of calcium carbonate (calcrete) and gypsum consequently
precipitated in the depocentre. The Early Tilmouth beds progressively interacted with
saline groundwaters during variable climatic and hydrologic conditions. The timing of
the pivotal switch from the perennial Anmatyerre lacustral phase to the more variable
Tilmouth lacustral phase is poorly constrained. Extrapolation from records from
analogous monsoon dominated lake basins suggests that deposition of the Anmatyerre
Clay may have ceased in the Middle Pleistocene, possibly during the severe Marine
Isotope Stage (MIS) 10 glacial period. Much of the overlying Early Tilmouth beds may
have been deposited during the MIS 7 interglacial period. Attenuation of the main
Tilmouth lacustral phase was followed by a deflationary episode. Resumed lacustrine
sedimentation involved more intense interaction with saline groundwaters in a greatly
contracted, shallow lake setting, and deposition of the highly gypseous Late Tilmouth
beds. This lacustral phase may have occurred during early MIS 5, the last interglacial
period. An optically stimulated luminescence (OSL) date from a regional linear
dunefield in the basin indicates an episode of dune mobility before 95 ka.
Arid periods and the continued dominance of highly saline groundwaters followed the
Tilmouth lacustral period at Lake Lewis, heralding playa conditions during the Late
Pleistocene. Large volumes of gypsum in the form of thick aeolian sand deposits in
playa islands and playa-fringing dunes are a legacy of high groundwater tables,
moderate or high recharge, evaporative pumping at the playa and possible episodes of
enhanced windiness. Interspersed stable periods and the influence of meteoric waters on
playa processes are indicated by gypcretisation of respective gypsum sand units in the
playa islands. Widespread quartz dunes across the basin landscape represent a period of
maximum aridity, at around 23-21 ka. Subsequent ameliorated climatic conditions are
represented by strandlines surrounding Lake Lewis that attest to inundation by
floodwaters, and substantial fluvial sedimentation along the creeks. OSL dates indicate
that the latter sediments span the period 19 - 0 ka. This latest period in the evolution of
the basin is additionally represented by reduction of aeolian activity, major disruption of
dunefields by floodwaters, and karstic degradation of calcrete ground.
Groundwater evolution since hydrologic closure of the basin has followed a CaC0₃ -
CaS0₄.2H₂0 path. Precipitation of large volumes of calcium carbonate and gypsum during various phases in the Quaternary has led to near-depletion of dissolved Ca stores
in the system. The present-day brine is enriched in Na-Cl-S0₄ and has a salinity of
210,000 mgL⁻¹ (Total Dissolved Solids). High concentrations of dissolved silica,
combined with the availability of a favourable host in the form of karstified calcrete,
and continued high evaporation rates have promoted precipitation of large amounts of
opaline and chalcedonic silica around the playa. Groundwaters flowing lakeward from
the silicified calcrete aureole have consequently become silica-depleted. This has
greatly impinged upon the brine composition and on diagenetic processes beneath the
playa. The zeolite mineral, analcime, Na(A1Si2)06.H20, is precipitating authigenically
in the Anmatyerre Clay in the face of silica-deficient, sodium-enriched brine. These
findings have resulted in the first detailed investigation of the formation of zeolites in an
Australian salt lake setting. Analysis of diagenetic minerals at Lake Lewis has
underscored the importance of the antithetic relationship between active silica
precipitation, shoreward, in the playa margins, and active analcime crystallisation
lakeward, beneath the playa.
Despite being the furthest from the coast of Australia's salt lakes, lying at the southern
edge of influence of the Australian monsoon, the research reveals that Lake Lewis has,
through long periods of its evolution, been a well-watered and efficient lake basin.
Available rainfall continues to be efficiently delivered to the lake in today's semi-arid
climatic regime. This is attributed to the orographic influence of the adjacent ranges, the
high catchment area to lake area ratio and the centripetal drainage system that feeds the
lake directly from the encompassing mountains. Notwithstanding the effective delivery
of available rainfall, the lake system evolved to a groundwater dominated regime during
the Late Pleistocene and has continued to be substantially governed by groundwater
processes. The distinctive diagenetic processes currently operating at the depocentre are
driven by both the chemical composition of groundwaters and the intensity of
evaporation in the current climatic regime.
37
Higgs, Caldin Grant. "Geochemical insights into the influence of Holocene sea level change on the evolution of the Mkhuze River Delta, Lake St Lucia, northen KwaZulu- Natal." Thesis, 2017. https://hdl.handle.net/10539/23745.
Full textAbstract:
Thesis submitted in fulfilment of the academic requirements for the degree of Master of
Science.
Department of Chemistry
University of Witwatersrand, Johannesburg April 2017.The Mkhuze River discharges into the most northern part of Lake St Lucia, via a contemporary bayhead delta. The delta formed in response to sea level rise during the last deglaciation and today exerts great influence on the functioning of Lake St Lucia, one of the largest estuarine systems in Africa and a globally important conservation area. A sediment core (11.5 m) was extracted from the distal end of the delta to examine the geomorphic evolution of the Mkhuze River Delta and links with variations in Holocene sea level and climate. Radiocarbon and optically-stimulated luminescence dating show that the core captured the entire Holocene infill and documents changes in sedimentation over the last ~13.8 kyr. Grain size and high resolution XRF analysis indicates that initiation of the modern delta occurred since ~7200 cal yr BP , when deglacial sea-level rise reached present-day level. Initial Holocene aged sediments are dominated by clay and silt material that was deposited when seawater intruded into Lake St Lucia via a palaeo-river connection to the ocean at Leven Point. The influx of silt and clay material was accompanied by the emergence of an onshore proto-barrier that created a sheltered lagoonal environment and promoted the accumulation of fine fluvial sediment. The presence of discrete, coarse-grained horizons enriched in zircon identifies a period of increased marine palaeostorm activity between 4700 and 2500 cal yr BP. This period is characterised by the presence of discrete shell fragment accumulations and is interpreted to reflect a strongly positive Indian Ocean dipole anomaly, which resulted in warmer sea surface temperatures and an increase in regional cyclone activity and frequency. The upper part of the core is characterized by generally fine silt and is marked by a decrease in sedimentation rate that corresponds to a phase of lateral delta progradation. The last ~1700 cal yr BP years of the record identify with subtle changes in grain size that can be attributed to a strengthening in El Niño–Southern Oscillation (ENSO) activity, which is known to be associated with prolonged drought and wind erosion in eastern South Africa. This study highlights the usefulness of coastal geochemical records in identifying environmental changes and related climate signals at a regional scale.
GR2018
38
Vardy, Sheila R. "The deglaciation and early postglacial environmental history of southcentral Newfoundland : evidence from the palynostratigraphy and geochemical stratigraphy of lake sediments /." 1991. http://collections.mun.ca/u?/theses,103501.
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Miller, Warwick Richard. "The bathymetry, sedimentology and seismic stratigraphy of Lake Sibaya- Northern KwaZulu-Natal." Thesis, 1998. http://hdl.handle.net/10413/4431.
Full textAbstract:
The morphology of Lake Sibaya is a product of an ancient fluvial system that drained a coastal
landscape dominated by aeolian processes. The sedimentary processes within the lake are driven
by wind generated currents. The dominant sedimentary process is one of lake segmentation,
whereby prograding bedforms isolate the lake into smaller water bodies. The prograding
bedforms include cuspate forelands and sand spits. The size and mobility of these bedforms is a
function of sediment availability and current regime.
The bathymetry of Lake Sibaya is discussed, with emphasis on geomorphic features derived from
the ancient aeolian landscape as well as features related to modern sedimentary processes. The
presence of underwater knickpoints and terraces indicate that lake level fluctuations have been
common in Lake Sibaya. It is during lake highstands that large volumes of sand are eroded from
aeolian dunes which surround the lake and made available for shoreline progradation. Ancient
dune topography is preserved to depths of 20 m below water-level within the lake.
Surface sediment distribution maps were compiled from 515 grab samples and thirteen core
samples. Fine grained, well sorted, coarse skewed quartz sand comprises the majority of the
surface area of the lake floor. Gyttja is the other dominant sediment type and accumulates in
palaeovalleys and depressions on the lake floor. Sediment distribution in Lake Sibaya is discussed
in terms of modern lacustrine processes as well as inherited sedimentary characteristics.
The stratigraphy of the sediments underlying Lake Sibaya was investigated using a Uni-Boom
seismic profiling system. Seismic profiles were compiled by identifying acoustically reflective
surfaces that show regional development. Thirteen seismic overlays were prepared, and are
illustrated as west - east and north - south seismic profiles. Five sequences ranging in age from
late Cretaceous to Holocene were identified from the seismic profiles, and are described in terms
of sequence stratigraphic principles. The seismic sequences were interpreted within a
lithostratigraphic framework and are presented as a series of idealised geological sections.
Thirteen sediment cores were collected from the Lake Sibaya area in order to ascertain the
accuracy of the stratigraphic interpretation of the seismic records, to investigate reflective
horizons identified from seismic records and to collect dateable material. Interpretation of the
sediment cores reveals that a proto Lake Sibaya existed on drowned dune topography, during the
period ± 43500 BP to ± 25500 BP prior to the Last Glacial Maximum. During the early to mid
Holocene the Lake Sibaya site was occupied by a saline lagoon which underwent isolation from
the sea ± 5030 BP. Since the mid-Holocene the lake has evolved to totally freshwater conditions
and has undergone little sedimentation.
The geological evolution of the Lake Sibaya area is discussed in terms of the geometry of the
identified seismic sequences, the sedimentary characteristics of these sequences and the
radiocarbon dates provided from the sediment cores. Palaeo-environmental conditions during the
accumulation of the sedimentary sequences is discussed where fossil remains permit.Thesis (M.Sc.)-University of Natal, Durban, 1998.
40
Pugh, J. M. "The late Quaternary environmental history of the Lake Heron Basin, Mid Canterbury, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Geology in the University of Canterbury /." 2008. http://hdl.handle.net/10092/1766.
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Lister, Guy. "Late Pleistocene Alpine deglaciation and post-glacial climatic developments in Switzerland the record from sediments in a peri-alpine lake basin /." 1985. http://catalog.hathitrust.org/api/volumes/oclc/24036988.html.
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De, Deckker P. (Patrick). "Australian Quaternary studies : a compilation of papers and documents submitted for the degree of Doctor of Science in the Faculty of Science, University of Adelaide." 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdd299.pdf.
Full textAbstract:
"April 2002" Includes bibliographical references and list of the publications and papers submitted. Pt. 1: section 1. Ostracod taxonomy and ecology -- section 2. Limnology of salt lakes -- section 3. Ostracod palaoecology - Quaternary environments -- section 4. Palaolimnology - Quaternary paleoenvironments and geology -- pt. 2: section 5. Geochemistry of ostracod shells -- section 6. Palaeoceanography Contains the majority of the author's scientific publications. Aims at reconstructing Quaternary paleoenvironments, mostly from the Australian region, using the fossil remains of organisms as well as new geochemical techniques.
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Roberts, Sarah Elizabeth. "Breccia of Frog Lakes : reconstructing Triassic volcanism and subduction initiation in the east-central Sierra Nevada, California." Thesis, 2014. http://hdl.handle.net/1805/4085.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)The Antler and Sonoma orogenies occurred along the southwest-trending passive Pacific margin of North America during the Paleozoic concluding with the accretion of the McCloud Arc. A southeast-trending sinistral transform fault truncated the continental margin in the Permian, becoming a locus for initiation of an east-dipping subduction zone creating the Sierran magmatic arc. Constrained in age between two early Triassic tuff layers, the volcanic clasts in the breccia of Frog Lakes represent one of the earliest records of mafic magmatism in the eastern Sierra Nevada. Tholeiitic rock clasts found in the breccia of Frog Lakes in the Saddlebag Lake pendant in the east central Sierra Nevada range in composition from 48% to 63% SiO2. Boninites produced by early volcanism of subduction initiation by spontaneous nucleation at the Izu-Bonin-Mariana arc are more depleted in trace element concentrations than the clasts while andesites from the northern volcanic zone of the Andes produced on crust 50 km thick have similar levels of enrichment and provide a better geochemical modern analogue. Textural analysis of the breccia of Frog Lakes suggest a subaqueous environment of deposition from a mature magmatic arc built on continental crust > 50 km thick during the Triassic. The monzodiorites of Saddlebag and Odell Lakes are temporal intrusive equivalents of the breccia of Frog Lakes and zircon geochemistry indicates a magmatic arc petrogenesis.