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Showing 1 to 20 of 20 for “"varve"”.
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Varve Chronology, Proxy Calibration, and Holocene Climate of Minnesota
Despite the numerous Holocene paleoclimatic records from the North American continent, few existing records from the American Midwest have adequate chronological controls, marking it problematic to link regional climatic changes to possible larger-scale forcing. With solid 14C chronologies, the …
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Varve and event layer chronology of Lake Suigetsu (Japan) back to 40 kyr BP and contribution to the international consensus atmospheric radiocarbon calibration curve
… intention of the PhD project was to create a varve chronology for the Suigetsu Varves 2006' (SG06) composite profile from Lake Suigetsu (Japan) by thin section microscopy. The chronology was not only to provide an age-scale for the various palaeo-environmental proxies analysed within the SG06 …
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Setting the Holocene clock using varved lake sediments in Sweden
… of this thesis was to study annually laminated (varved) Holocene lake sediment in Sweden, their formation and their potential as chronological and palaeoecological archives. Five lakes with continuous Holocene varved lake sediment sequences in northern (Västerbotten) and west central Sweden …
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Climatic signals and frequencies in the Swedish Time Scale, River Ångermanälven, Central Sweden
… variation. Along the Swedish East Coast varved deposits of sand silt and clay couplets make up a chronology, which extend from the present into the Late Glacial. This chronology is known as the Swedish Time Scale (STS) and the c. 8000 varves were deposited in River Ångermanälven, Central …
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A 7000 yr runoff chronology from varved sediments of Lake Mondsee (Upper Austria)
… flood events are needed. Annually laminated (varved) lake sediments are meaningful natural geoarchives because they provide continuous records of environmental changes > 10000 years down to a seasonal resolution. Since lake basins additionally act as natural sediment traps, the riverine …
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Pollen analysis, chronology and palaeomagnetism of three Late Weichselian sites in southern Sweden
… dating and, for two of the sites, on a clay-varve chronology. The stratigraphies were correlated to the GRIP event stratigraphy and their ages are expressed in calendar years BP. The pollen records compare well to the established Late Weichselian pollen stratigraphy for southern Sweden, and …
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Analysis of laminated sediments from Lake DV09, northern Devon Island, Nunavut, Canada
… 89° 18'55"W) contains annually-laminated (varved) sediments, providing a 1600-year record of climate variability. A minerogenic lamina deposited during the annual thaw period and a thin deposit of organic matter deposited during the summer and through the winter, together form a …
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Investigating potential climatic cycles in glacially-influenced rhythmites of the upper Gowganda Formation using geochemical, sedimentological and spectral analyses
… Huronian Supergroup contains glacially-induced, varve-like rhythmites composed of turbiditic micro-laminae that potentially preserve a detailed record of climatic conditions during the Paleoproterozoic Era. A sedimentological analysis of upper Gowganda Formation deposits enabled identification of …
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Mid- to Late Holocene flood reconstruction from two varved sediment profiles of pre-alpine Lake Ammersee (Southern Germany)
… paleoclimate archives like annually laminated (varved) lake sediments allows to fill this gap in knowledge offering precise dated time-series of flood variability for millennia. During river floods, detrital catchment material is eroded and transported in suspension by fluid turbulence into …
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Holocene climate and environmental variability in NE Germany inferred from annually laminated lake sediments
… is compiled by using a multiple-dating concept. Varve counting and tephra findings form the chronological framework for the last ~6000 years. The good agreement with independent radiocarbon dates of terrestrial plant remains verifies the robustness of the age model. The resulting reliable and …
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Depositional Environments of Siliceous Laminites in the Laney Member of the Green River Formation, Sublette County, Wyoming
… Green River formation. The shales are rhythmic, varve -like laminites, composed of quartz, authigenic potassium feldspar , dolomite, and zeolite minerals. The association of these minerals suggest that the original sediment contained significant amounts of volcanic ash, and were deposited in a …
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Investigating laminated sediments of the Al-Azraq basin, Jordan and the implications for paleoenvironmental variability
… from the Dead Sea basin, and determined to be varved deposits, or seasonal couplets forming annual deposits. A current debate in the literature refutes the varve designation of Dead Sea sediments (Lopez et al. 2016; Ben Dor et al., 2019; Bookman, 2020; Ben Dor et al., 2020). This study focuses …
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Extreme events in geoarchives
… flood recorders. Therefore, annually laminated (varved) lake sediments seem to be the most suitable archives since (i) lake basins act as natural sediment traps in the landscape continuously recording land surface processes including floods and (ii) individual flood events are preserved as …
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East African monsoon variability since the last glacial
… of the laminations and demonstrates that the varve-thicknesses are strongly linked to the duration and strength of the windy season. Given the modern control of seasonal ITCZ location on wind and rain in this region and the inverse relation between the two, thicker varves represent windier and …
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High-resolution environmental change in the late Jurassic Kimmeridge clay formation
… of scales. These changes ranged from yearly 'varve couplet' alternations of organic-rich and coccolith-rich fabric, to 60-100 year and perhaps 200-400 year storm events and larger scale events of the order of several 1000 years. The later represent changes in climatic humidity over the …
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Investigations of temporal changes in climate and the geomagnetic field via high-resolution radiocarbon dating
… precise chronology of the annually laminated (varved) sediments of Lake Gyltigesjön in south-west Sweden for the period around 3000-2000 cal BP. With this technique, it was possible to estimate the old-carbon effect (14C reservoir age) in the lake sediments. The bulk sediment based chronology …
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Living with a changing climate: Holocene climate variability and socio-evolutionary trajectories, central Turkey
… in 2010 cover the last ~14000 years based on varve counting and climate-stratigraphic correlation. The changing chemical composition of these sediments has been obtained using high-resolution Itrax XRF core scanning, mainly at 200μm resolution over 21.6m. Temporal differences in Ca and Sr are …
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High resolution palaeoceanography and palaeoclimatology from mid and high latitude Late Cretaceous laminated sediments
… techniques and found to contain marine varves. The varve interpretation is based on the pervasive occurrence of laminae types that can be related to different seasons and placed into robust annual flux cycles. In the Marca Shale this consists of intermittent near-monospecific laminae of …
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Lateglacial to Holocene climatic and environmental changes in Europe : multi-proxy studies on lake sediments along a transect from northern Italy to northeastern Poland
… circulation (MOC). Combining microscopic varve counting and AMS 14C dating yielded a precise duration estimate (ca. 150 years) and absolute dating of the 8.2 ka cold event, both being in good agreement with results from other palaeoclimate records. Moreover, a sudden temperature overshoot …
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Reconstructing ice dynamics in the central sector of the last British-Irish Ice Sheet
… on till matrixes, clast lithological counts, varve analysis and microstructural (thin sections) data. Results from this study have demonstrated that the central sector of the ice sheet was characterised by repeated ice-flow switches, initiation and termination of ice streams, drawdown into ice …