Variability of river discharge and Atlantic-water inflow at the Laptev Sea continental margin during the past 15,000 years: implications from maceral and biomarker records

Abstract

In order to reconstruct the depositional environment from the Laptev Sea continental slope and shelf during the past~15,000 years BP maceral analysis was carried out on two sediment cores (PS2458-4, PS2725-5) and compared with organic-geochemical parameters. During the transition from the Last Glacial to the Holocene the environment of the Laptev Sea shelf was controlled by the post-glacial sea level rise, variations in river discharge, surface-water productivity, and Atlantic-water inflow along the Eurasian continental margin. Based on our results, we identify the following significant changes of the environment: (a) at approximately 13,500 years BP the first step of deglaciation (Termination 1a) is documented by the deposition of marine and fresh-water organic matter; (b) at approximately 10,400 years BP the first post-glacial influence of Atlantic-water inflow along the Eastern Laptev Sea continental margin is indicated by an increase in marine organic matter; (c) at the beginning of the Holocene an increased fluvial supply is documented by an increase in fresh-water alginite; and (d) since~9500±8000 years BP modern marine conditions are established at the Laptev Sea continental margin as documented in increased amounts of marine macerals, biomarkers (dinosterol, brassicasterol, short-chain fatty acids), and dinoflagellate cysts.

History of freshwater runoff across the Laptev Sea (Arctic) during the last deglaciation

“…Second, enhanced fluxes of terrigenic particles can cause an extreme dilution of the biogenic content, resulting (statistically) in a barren sediment section. We exclude this possibility, because none of the sedimentological, sedimentphysical, and geochemical parameters of the sediments shows a significant change at 525 cm (Boucsein et al, 2000;Müller and Stein, 2000;Stein and Fahl, 2000;Spielhagen, unpublished data). Carbonate dissolution, as a third possibility, is unlikely because there is no evidence for a partial dissolution below or above the interval.…”

“…Associated freshwater events could be detected in central Arctic Ocean planktic isotope records (Poore et al, 1999;Spielhagen et al, 2004). Deglacial changes in freshwater runoff from the Kara and Laptev Seas could be deduced from geochemical and sedimentological records (Lubinski et al, 1996(Lubinski et al, , 2001Polyak et al, 1997Polyak et al, , 2002Hald et al, 1999;Boucsein et al, 2000;Müller and Stein, 2000;Stein and Fahl, 2000). In this paper, we report on results from investigations of a large volume sediment core from the Laptev Sea continental margin (Fig.…”

Late Pleistocene-Holocene and Recent Ostracoda of the Laptev Sea and their importance for paleoenvironmental reconstructions

“…By approximately 9.5-8 cal. ka BP modern marine conditions were established on the Laptev Sea continental margin (Boucsein et al, 2000). It seems likely that before 9.8 cal.…”

Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion

“…Cauwet and Sidorov (1996) and Lara et al (1998) estimated the annual modern Lena River POC discharge as 1.8 Tg (1 Tg = 10 12 g), higher than that of any other GSAR, and the Lena River DOC discharge as 3.6 Tg, twice as high as that of the Yangtze River -the largest among Asian rivers. Boucsein et al (2000) argue that a significant change in composition of sediment OM (an increase of freshwater alginite and immature plant material) on the Laptev Sea continental slope at the beginning of the Holocene was due to increased Lena River discharge. Alternatively, Bauch et al (2001) believe that the increased Holocene deposition of OM in the Laptev Sea was mainly the result of coastal erosion due to sea level transgression.…”