High-resolution seismic reflection evidence for middle Holocene environmental change, Owasco Lake, New York

Approximately 70 km of new decimeter-resolution seismic reflection profile data from Owasco Lake, New York define a middle Holocene (similar to 4600 C -14 yr B.P.) erosion surface in the north end of the lake at water depths a s great as 26 m, Beneath the lake, post-glacial sediments are up to 9 m thi ck and represent about 10% of the total sediment fill. Early to middle Holo cene sediments, similar to6 m thick, contain biogenic gas at the south end of the basin and a large (4 km x 300 m x 15 m) subaqueous slide deposit alo ng the east-central portion of the lake. Late Holocene sediments are thinne r or absent, particularly at the north end of the lake. The middle Holocene erosion surface may have been produced by a drop in lake level, Alternativ ely it may represent a change in climate during the transition between the relatively warm Holocene hypsithermal and coot neoglacial. At this time(sim ilar to 4600 C-14 yr B.P.) circulation in Owasco Lake appears to have evolv ed from sluggish to active. The increased circulation, which persists today , probably resulted from atmospheric cold fronts with strong southwesterly winds that piled up water at the north end of the lake. The increased water circulation may have been ultimately driven by decreasing insolation, whic h produced an increased pole-to-equator thermal gradient and, thus, stronge r global winds that began at the transition between the hypsithermal and ne oglacial. (C) 2001 University of Washington.