18 Mar 2004

Cold Mountain—Tundra at King's Gap: Evidence for Late Pleistocene Tundra Conditions in South-central Pennsylvania

Ms. Helen Delano, P.G., Pennsylvania Topographic and Geologic Survey

Plant macrofossils from the lower portion of a sediment core have extended the record of late Pleistocene tundra vegetation in central Pennsylvania 144 km (89 mi) west-southwest of the previously known occurrence. We have obtained several sediment cores from a vernal pond in Kings Gap State Park on the north flank of South Mountain in Cumberland County.  The pond occupies a depression, presumably a sinkhole, in thick sandstone colluvium over the Tomstown dolomite.  Radiocarbon dates from a core obtained in January 2001 (16,080 BP at 4.9 m and 14,410 BP at 2 m) correspond to a time when Wisconsinan ice had retreated north of Pennsylvania. Norton Miller of the New York Biological Survey has identified macrofossils from the core.  Dryas integrifolia (mountain avens), Salix (willow), Carex sp. (sedge), and mosses indicate a tundra environment before about 14,000 BP.   Spruce needles are sparse in this zone, but increase in abundance above the tundra indicators. Confirmation of tundra conditions at Kings Gap increases our knowledge of plant succession in late Pleistocene Pennsylvania and adds credence to descriptions of periglacial features on South Mountain and other areas in south-central Pennsylvania well south of the glacial border.