Abstract

Wisconsinan interstadial sediments, consisting mainly of moss peat, peaty silt and sand, are exposed near Titusville in northwestern Pennsylvania. They lie beneath the Titusville Till, south of the margin of the Late Wisconsinan Kent Till. Radiocarbon dates obtained range from 35 000 to 40 000 years BP, indicating that the sediments are of late Port Talbot II age (Mid-Wisconsinan).A pollen diagram from the section is divided into the three informal lower, middle and upper zones. Macrofossils of dwarf birch Betula glandulosa var. glandulosa, the only subarctic taxon recovered, characterize the lower dated peat layer (lower zone). The presence of dwarf birch is indicative of a forest–tundra environment during deposition of this peat. In the upper dated peat layer (upper zone) low numbers of Cyperaceae seeds, along with relatively high percentages of Cyperaceae pollen, imply that at least part of the sedge pollen was derived from plants growing on the uplands in an even more open spruce parkland. These data outweigh the implication that the climate was ameliorating as suggested by the marked rise in Pinus pollen in the upper zone. The pine pollen are attributed to the relatively increased effect of long distance transport as the local tree pollen production decreased.

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