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Showing 1 to 17 of 17 for “"varves"”.
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Climatic signals and frequencies in the Swedish Time Scale, River Ångermanälven, Central Sweden
… as the Swedish Time Scale (STS) and the c. 8000 varves were deposited in River Ångermanälven, Central Sweden. Of these varves, the last c. 2000 years are considered secure in terms of coherent chronology and internal thickness variation. A 2000 year long geometric mean varve thickness series was …
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Analysis of laminated sediments from Lake DV09, northern Devon Island, Nunavut, Canada
… clastic-organic couplet each year. The thinnest varves occur from AD800-1050, and the thickest from AD1100-1300, during the Medieval Warm Period. The relative sediment density is also highest during this period suggesting increased sediment transport energy. The coldest period of the Little Ice …
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East African monsoon variability since the last glacial
… the inverse relation between the two, thicker varves represent windier and thus drier years. El Niño (La Niña) events are associated with wetter (drier) conditions in east Africa and decreased (increased) surface wind speeds. Based on this fact, the thickness of the varves can be used as a tool …
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Genesis and Sedimentation of an Ice-Walled Lake Plain in Northeastern Illinois
… that have previously been thought to be annual varves, appear to have clay layers that are too thin and inconsistent for annual varves. The fourth facies is also considered lake sediment for the same reasons as facies three, but facies 4 also contained thicker sand beds. Bedforms and scours …
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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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The hydrological and limnological characterization of two Canadian water catchments sensitive to anthropogenic influences: Crawford Lake, Ontario and Old Crow Flats, Yukon
… setting facilitates the accumulation of varves below the chemocline where the lack of bioturbation is attributed to the saline, alkaline, and isolated nature of the monimolimnion, allowing the undisturbed laminations to provide an annually resolvable chronology of local and global …
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Laminated Sediments of Loch Ness, Scotland: Indicators of Holocene Environmental Change
… developed that the finer laminations represent varves. This was tested by means of lamination counting, and by radiocarbon dating of material from one 'long' core. Comparison of the two chronologies thus derived suggested that the hypothesis was correct, and that a non-continuous chronology had …
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Setting the Holocene clock using varved lake sediments in Sweden
… environmental prerequisites for the formation of varves and, therefore, provides a tool for finding annually laminated sediments in the Swedish boreal environment. Varve chronologies, supported by other independent dating methods, i.e. radiocarbon dating, tephra isochrones and paleomagnetic …
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Mid- to Late Holocene flood reconstruction from two varved sediment profiles of pre-alpine Lake Ammersee (Southern Germany)
Climate is the principal driving force of hydrological extremes like floods and attributing generating mechanisms is an essential prerequisite for understanding past, present, and future flood variability. Successively enhanced radiative forcing under global warming enhances atmospheric …
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A 7000 yr runoff chronology from varved sediments of Lake Mondsee (Upper Austria)
… years. This sediment record consists of calcite varves and intercalated detrital layers, which range in thickness from 0.05 to 32 mm. Detrital layer deposition was analysed by a combined method of microfacies analysis via thin sections, Scanning Electron Microscopy (SEM), μX-ray fluorescence …
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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
… 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 project, but also and foremost to …
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Investigating potential climatic cycles in glacially-influenced rhythmites of the upper Gowganda Formation using geochemical, sedimentological and spectral analyses
The upper Gowganda Formation of the 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 …
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High-Resolution Record of Vegetation and Climate Change During the Holocene in Southwestern Québec
A varved sediment sequence spanning the past ~11.0 ka was collected from Lac Noir (45.77N, 75.13W, 168 m a.s.l.) in southwestern Québec. A high-resolution pollen record documents the post-glacial vegetation history of the region over the course of the Holocene. The record shows an initial open …
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Reconstructing climate from the Dead Sea sediment record using high-resolution micro-facies analyses
The sedimentary record of the Dead Sea is a key archive for reconstructing climate in the eastern Mediterranean region, as it stores the environmental and tectonic history of the Levant for the entire Quaternary. Moreover, the lake is located at the boundary between Mediterranean sub-humid to …
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Hydroclimate variability in Central America during the Holocene inferred from lacustrine sediments in Lake Izabal, eastern Guatemala
"Holocene hydroclimate reconstructions have contributed to our understanding of the mechanisms controlling precipitation in Central America. Recent hydroclimate proxy records from the region, however, have revealed considerable spatiotemporal complexity in precipitation variability. This complexity …
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Holocene development of Lake Lögurinn and Eyjabakkajökull : a multi-proxy approach
The North Atlantic region has experienced significant climate fluctuations during the Holocene. It has been shown that these fluctuations affected the terrestrial environment in Iceland, including its glaciers and ice caps. However, the full Holocene development of Icelandic glaciers, including the …
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Investigations of temporal changes in climate and the geomagnetic field via high-resolution radiocarbon dating
Geological archives have shown periods of abrupt climate change in the relatively stable Holocene epoch (last ca. 11 700 years). One of these periods was around 2800 cal BP. Several records, mainly from Europe, reveal a shift towards wetter, cooler and windier conditions. There are, however, …