| Summary: | International audience Lake Ohrid (Albania, Macedonia) is probably the oldest and one of the deepest lakes in Europe. It potentially provides a continuous palaeoenvironmental record over the entire Quaternary. In 2004, a 10-m-long sediment record (JO2004-1) was recovered from the south-western part of the lake from a depth of 100 m (40°55.000 N, 20°40.297 E). The record is a composite of two series of consecutive 3-m-long sections taken from two sites within 5 m lateral distance using a modified Streif-Livingston piston corer (UWITEC, Austria). On the basis of seven AMS radiocarbon dating, five tephras layers and derived accumulation rate model, the Ohrid sequence extends back to 140 ka. It covers the last glacial-interglacial cycle with nearly continuous sedimentation (0.075 mm/yr, on average), except for a major hiatus (at 532.4 cm) of roughly 12,000 years between 102.75 and 89.90 ka. We evaluate the potential of using the oxygen and carbon isotope signature of the calcite of the benthic ostracod valves deposited in Lake Ohrid sediments as a palaeoclimate proxy. Twelve ostracod species, which are all endemic to Lake Ohrid, were preserved only during the interglacial phases. Their absence during full glacial periods is most likely due to calcium carbonate under-saturation of the lake water, when permafrost prohibited infiltration of atmospheric water into the limestone complexes in the lake drainage basin. For periods with ostracod preservation, the oxygen isotope signature of ostracod calcite is a reliable measure of the oxygen isotope composition of past lake water. However, the climatic interpretation of this record is strongly biased by water balance variations and by varying contribution of different vapour sources. The carbon isotope record of ostracods responds more consistently to climatic changes, and is a potentially quantifiable proxy for vegetation cover and soil build-up. Ostracod preservation and oxygen and carbon isotopes both record a succession of glacial-interglacial cycles and are therefore ...
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