ORGANIC REMAINS IN FINNISH SUBGLACIAL SEDIMENTS

Many sites in Fennoscandia contain pre-late Weichselian beds of organi c matter, located mostly in the flanks of eskers. It is a matter of de bate whether these fragmentary beds were deposited in situ, or whether they were deposited elsewhere and then picked up and moved by glacial ice. The till-mantled esker of Harrin-kangas includes a shallow depre ssion filled with sand and silt containing, for example, several tight ly packed laminar sheets of brown moss (Bryales) remains. It is argued that these thin peat sheets were transported at the base of the ice s heet, or englacially, and were deposited together with the silt and sa nd on the side of a subglacial meltwater tunnel. Subglacial meltout ti ll subsequently covered the flanks of the esker near the receding ice margin. Information about the depositional and climatic environments w as obtained from biostratigraphic analysis of the organic matter. Poll en spectra for the peat represent an open birch forest close to the tu ndra zone. A thin diamicton beneath the peat contains charred pine woo d, recording the former presence of pine forests in western Finland. T he unhumified, extremely well-preserved peat evidently originated duri ng the final phase of an ice-free period, most probably the end of the Eemian Interglaciation. It was redeposited in the esker by the last i ce sheet. Reconstructions of the Pleistocene chronology and stratigrap hy of central Fennoscandia that rely on such redeposited organic matte r should be viewed with caution. (C) 1995 University of Washington.