Forest History of Ohio. I, Radiocarbon Dates and Pollen Stratigraphy of Silver Lake, Logan County, Ohio

Radiocarbon and pollen analysis of a sediment core (8.9 m) from Silver Lake in central Ohio indicates that deposition began in late Woodfordian time (11,000-14,000 radiocarbon years ago) and has been continuous to the present. The pollen sequence includes a basal spruce-fir pollen zone, changing abruptly to oak-elm immediately above a radiocarbon date of 9800 ±210 (OWU-39). A total of 19 radiocarbon dates document the climatic and environmental changes inferred from the sediment record. The Xerothermic interval of Sears (1942c) within the Hypsithermal (Deevey and Flint, 1957) is bracketed by radiocarbon dates (1300-3600 years, B.P.) and a distinct minimum in beech pollen. The presence of Zea pollen stratigraphically lower than the sharp rise in Ambrosia pollen which marks the advent of European settlers is believed to indicate pre-colonization Indian agriculture.