LATE-QUATERNARY CLIMATE IN THE RIDGE AND VALLEY OF VIRGINIA, USA - CHANGES IN VEGETATION AND DEPOSITIONAL ENVIRONMENT

Brown Pond, Virginia, in the Ridge and Valley physiographic province, contains a record of changing vegetational and depositional environments that dates to 17,130 BP. Six cores were retrieved in a transect of the pond. Pollen and macrofossils were identified from the longest central core and a series of AMS radiocarbon dates obtained from identified macrofossils and sediment. The pollen and macrofossil record combined with laterally consistent changes in lithostratigraphy reveal a changing climate. From 17,300 to 14,100 BP, a closed boreal forest of Pinus-Picea-Abies grew at the site. Pinus dominates the pollen assemblage while Picea and Abies dominate the macrofossil assemblage. Subtle increases in more thermophilous and mesophytic taxa indicate gradual climate amelioration after the full-glacial. A marked increase in Alnus at 14, 100 BP signals an increase in moisture, possibly related to the global evidence for rapid climate change at 14,000 BP. At this central Appalachian site, Abies and Alnus are found in relatively greater amounts in the late-glacial forest than previous studies indicated. Low organic contents and evidence of gleyed conditions, seen in the core transect from 10,000 to 8000 BP, point towards low-water levels in the early Holocene-approximately coincident with the expansion of Quercus.