Ostracod assemblages in late Quaternary varved glaciomarine clay of the Baltic Sea Yoldia stage in eastern middle Sweden

Four cored sites in eastern middle Sweden have been analysed for their cont ent of calcareous fossils. The investigated sediments consist of late Quate rnary varved clay deposited during the Baltic Sea Yoldia stage. Four region al palaeoecological units, A-D, have been established. Unit A reflects ice- proximal conditions, unit B optimal conditions for the benthic fauna and un it C the termination of a saline phase. In unit C oxygen deficiency might h ave occurred. In the fourth unit, D, no fossils were found. The fauna recor ded is poor in taxa and indicates a weak marine influence. The salinity was higher in the western part of the investigated area due to the proximity t o the inlet of marine water. The meltwater influx was high and the salinity probably fluctuated considerably. The ostracod Cytheromorpha macchesneyi ( Brady and Crosskey) is reported for the first time in Quaternary deposits f rom northwestern Europe and indicates that a connection could have existed between the Baltic and the White Sea in Late Glacial times. (C) 1999 Elsevi er Science B.V. All rights reserved.