Search results for "Glacial period"
showing 10 items of 196 documents
Variations in Sediment Yield from the Upper Doubs River Carbonate Watershed (Jura, France) since the Late-Glacial Period
1999
AbstractThe Upper Doubs River Valley is a 910-km2watershed feeding into Lake Chaillexon. The lake was formed by a natural rockfall at the end of the Bølling Chronozone (around 14,250 cal yr B.P.) and since then has trapped material eroded from the watershed. The filling process and variations in sediment yield have been investigated by mechanical coring, seismic surveys, and electric soundings. The detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the Late-Glacial period and Holocene Epoch and estimating the lake's entrapment capacity. This enables us to determine the intensity of the erosion processes in rel…
Late Pleistocene Detrital Sediment Yield of the Jura Glacier, France
2001
AbstractMeasures of present-day glacial erosion vary widely with the technique employed. This paper quantifies the glacial material trapped in a proglacial lake during the Würm glacial period. The Combe d'Ain site was occupied by a meltwater lake where all the detrital material entering it from the Jura glacier accumulated. Sediment yield is computed from three factors: (1) the size of the sediment source area, (2) the length of time the system operated, and (3) the volume of sediment trapped. The sediment budget of the lake system suggests a detrital sediment yield of 4400±1700 metric tons per square kilometer and per calendar year. This represents a denudation rate of 1.6±0.6 mm per year,…
Aeolian sedimentation in arid and semi-arid environments of Western Mongolia
2004
Research on aeolian sediments in Mongolia shows two main cycles of aeolian sedimentation: first the accumulation of major sand fields neighbouring the eastern bank of rivers and lakes, and second the distribution of loess-like sediments on the mountain slopes. The first is resulting from strong westerly winds, being more strength especially during the glacial periods. The latter is resulting in the erosion and accumulation of silt in this region in more humid periods in Interstadial stages and at the end of glacial periods. Both cycles are described on the case study area of the Uvs Nuur Basin in Western Mongolia.
D/H ratios of methoxyl groups of the sedimentary organic matter of Lake Holzmaar (Eifel, Germany): A potential palaeoclimate/-hydrology proxy
2014
Stable hydrogen isotope ratios (dD values) of methoxyl groups in lignin and pectin from a variety of plant types from different locations have been shown to mirror dD values of precipitation, with a mean uniform isotopic fractionation. Since dD in precipitation is mainly influenced by climatic conditions, including temperature, evaporation and precipitation amount, methoxyl groups of organic matter have been proposed as a potential palaeoclimate proxy. Here, we measured the dD values of the methoxyl groups of sedimentary organic matter derived from sediment core segments of Lake Holzmaar (Eifel, Germany). The sediment core covers the entire Holocene and part of the Late Glacial (until 13,65…
Proglacial sediment dynamics from daily to seasonal scales in a glaciated Alpine catchment (Bossons glacier, Mont Blanc massif, France)
2018
The sediment yields of Alpine catchments are commonly determined from streamload measurements made some distance downstream from glaciers. However, this approach indiscriminately integrates erosion processes occurring in both the glacial and proglacial areas. A specific method is required to ascertain the respective inputs from (i) subglacial and supraglacial sediments, (ii) proglacial hillslopes and (iii) proglacial alluvial areas or sandurs. This issue is addressed here by combining high‐resolution monitoring (2 min) of suspended sediment concentrations at different locations within a catchment with discharge gauging and precipitation data. This methodological framework is applied to two …
Climate Change During the Holocene (Past 12,000 Years)
2015
This chapter summarises the climatic and environmental information that can be inferred from proxy archives over the past 12,000 years. The proxy archives from continental and lake sediments include pollen, insect remnants and isotopic data. Over the Holocene, the Baltic Sea area underwent major changes due to two interrelated factors—melting of the Fennoscandian ice sheet (causing interplay between global sea-level rise due to the meltwater and regional isostatic rebound of the earth’s crust causing a drop in relative sea level ) and changes in the orbital configuration of the Earth (triggering the glacial to interglacial transition and affecting incoming solar radiation and so controlling…
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves
2013
Abstract. The Weddell Sea and the associated Filchner–Rønne Ice Shelf constitute key regions for global bottom-water production today. However, little is known about bottom-water production under different climate and ice-sheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distingui…
Subglacial bedforms of the Zemgale Ice Lobe, south-eastern Baltic
2015
Abstract Presented in this paper are the results of the mapping of ∼6600 subglacial bedforms of the Zemgale Ice Lobe (ZIL), their composition and internal structure in the south-eastern Baltic region. Topographic maps at scale 1:10,000 were mainly used to map bedforms in Latvia, while a digital elevation model with cell size of 5 m was used for North Central Lithuania. The ZIL operated during the deglaciation of the Late Weichselian Scandinavian Ice Sheet (SIS), at least in the Middle Lithuanian and North Lithuanian glacial phases, and created a subglacial landform assemblage consisting of glacial lineations such as drumlins, mega-flutings, Mega Scale Glacial Lineations (MSGLs) and transver…
Ups and downs in the Red Sea
2003
Changes in past conditions in the Red Sea have been exploited to provide a detailed record of sea-level variation over much of the last glacial period. That record might tie in with events in the far south and north.
Paleolakes in the Gobi region of southern Mongolia
2018
Abstract Numerous lakes and remnants of paleolakes exist in western and southern Mongolia. For six basins in the area, detailed geomorphological maps were compiled, based on extensive field studies and remote sensing datasets. Several phases of high and low lake levels were reconstructed and dated by radiocarbon and optically stimulated luminescence. During the marine isotope stage (MIS) 6 lakes in southern and western Mongolia mostly disappeared. In contrast, large paleolakes existed during the last interglacial (MIS 5e) and lasted probably until the beginning of the last glacial. These huge lakes were caused by a strong East Asian summer monsoon, which reached southern and even western Mo…