Climate-driven changes in lake conditions during late MIS 3 and MIS 2: a high-resolution geochemical record from Les Echets, France

Veres, D., Lallier-Verges, E., Wohlfarth, B., Lacourse, T., KEravis, D., Bjorck, S., Preusser, F., Andrieu-Ponel, V. & Ampel, L.: Climate-driven changes in lake conditions during late MIS 3 and MIS 2: a high-resolution geochemical record from Les Echets, France. Boreas, 10.1111/j.1502-3885.2008.00066.x. ISSN 0300-9483. A new set of geochemical data obtained from a long sediment sequence from the Les Echets basin provides a new record of palaeoenvironmental change for western Europe. The sequence covers the late part of Marine Isotope Stage (MIS) 3 and MIS 2 (c. 46.1-15.0 cal. kyr BP) and extends over 30 m of sediment, allowing for high sampling resolution. Distinct cyclic fluctuations in aquatic productivity proxies suggest a tempo of environmental change at Les Echets that resembles the one established for Dansgaard-Oeschger cycles and Heinrich events. Increases in organic carbon are paralleled by high hydrogenous contents and enriched delta C-13(org) and C-org/N-tot ratios, implying a mixture of aquatic and land-derived constituents. The stable isotope values are directly linked to primary aquatic productivity and the input of terrestrial organic matter, enriched during warm, productive, periods, and drastically depleted during cold periods, particularly Heinrich events. Phases of relatively high productivity correlate with Dansgaard-Oeschger interstadials 8-2, while Heinrich events 3 and 2 are also clearly delineated by distinct lithological horizons with very low organic contents, high dry densities and enhanced organic matter oxidation. A large hiatus occurring about the time of Heinrich event 4 suggests that the cold and dry climate reconstructed for this event in the North Atlantic region also greatly affected Les Echets and its catchment.