Late Weichselian ostracod assemblages from the southern Kattegat, Scandinavia: a palaeoenvironmental study

The ostracods in three vibro cores (representing the time between c. 13 000 and 12 000 BP) from southern Kattegat were studied to further elucidate palaeoenvironmental conditions in an area interpreted to be influenced by a Late Weichselian drainage of the Baltic Ice Lake via the Oresund Strait. This time represents an extremely important phase of the deglaciation of the northern hemisphere. It is characterized by rapid climatic change and enormous amounts of meltwater that are drained into the ocean. The ostracod assemblages identified are characterized by a peculiar mixture of marine (arctic and temperate) and freshwater species believed to characterize environments ranging from the tidal zone of an outer estuary (or delta) to fully marine sublittoral conditions in a subarctic climate. Dominant species display autochthonous population structures typical of in situ elements of such environments. Indications of very shallow conditions are, however, difficult to reconcile with palaeobathymetrical inferences from earlier studies of shore-level displacements. It is, therefore, possible that the present assemblages are mainly death assemblages deposited offshore by postmortem meltwater discharge. Rare pre-quaternary ostracods similar to Mesozoic species previously reported from the Oresund Strait (drill holes) and the Swedish west coast may have been redeposited by outflowing meltwater.