Dan Hammarlund

A Late Weichselian sediment succession from the Kullen Peninsula, southern Sweden, was studied by means of stable carbon and oxygen isotope analyses of calcitic valves of selected ostracod taxa. The lower part of the record was deposited in a slightly brackish marginal sea close to the receding inland ice, whereas the upper part is lacustrine in origin as a result of glacio-isostatic rebound. The site was deglaciated at c. 17200 cal BP (c. 14500 C-14 BP) within the earliest ice-free area of Sweden, and the isolation took place c. 1100 cal years later. As a result of extensive input of glacial meltwater to the near-shore, shallow basin, the isotopic records predating the isolation give no clear indications of marine conditions. However, the isolation of the lake from the marginal sea is reflected by a distinct depletion of O-18 in ostracod calcite as a response to the changing isotope hydrology of the basin. The change towards a lacustrine environment also fostered a decrease in the input of minerogenic material and a related increase in organic carbon content of the sediments, which may explain a short-lasting depletion of C-13 in dissolved inorganic carbon and ostracod calcite. During the period of c. 14700-13900 cal BP a pronounced warming occurred associated with the onset of the Late Weichselian interstadial complex (Greenland Interstadial I). Based on a distinct enrichment of O-18 in ostracod calcite and applying modern spatial relations between delta(18)O of precipitation and temperature, this climatic shift involved an increase in mean annual air temperature in southernmost Sweden of at least 7 degrees C.