LATE NEOGENE CLIMATE CONDITION IN THE SOUTHERN APPALACHIANS

A Neogene site from northeast Tennessee (36.5^oN, 82.5^oW) has yielded well preserved floral and mammal remains, demonstrating a unique combination of North American and Eurasian biota in a forest-woodland. Fossil vertebrates from the site support the late Hemphillian Land Mammal Age (the latest Miocene to earliest Pliocene). The site consists of about 40 m of dark colored sediment of lacustrine origin, in which the top 4 m-thick fossiliferous laminated facies preserves excellent record of plant fossils, represented by wood, seeds, leaves, and pollen grains. Forty-eight palynological samples from seven different test-pits were analyzed. All pits exhibit a low pollen yield, a result of basic pH levels, drought, and fire events that occurred during the deposition. The palynofloral assemblage has a low to moderate diversity and is largely dominated by a Quercus–Carya–Pinus assemblage (~ 90% of the palynoflora). Floristically, we have recognized at least 40 genera, representing more than 25 families of seed plants. Based on the nearest living counterpart comparisons, these fossils can be identified with certainty to a specific modern genus. Therefore, the Coexistence Approach, a well-established quantitative paleoclimate reconstruction method, was used to reconstruct the paleoclimate condition. Seven climatic parameters are calculated as follows:

	Temperature (oC)			Precipitation (mm)
	Mean annual	ColdMonth	WarmMonth	Mean annual	WettestMonth	DriestMonth	WarmestMonth
Paleoclimate at the site	14-16	3-7	24-27	979-1520	148-225	9-24	120-149
Current climate of site	13	-4 -1	24	1034	109	81	109

The comparison clearly indicates that the southern Appalachians in the late Neogene was under a climate quite different from the modern; especially its winter in the late Neogene was much warmer (above freezing), which could explain the occurrence of alligators and beaded lizards in the fossil record. Furthermore, the much drier month (winter) in the past might be responsible to intensive forest fires, which contribute the common occurrence of charcoals all over the site. In general, the paleoclimate in the southern Appalachians appears less seasonal in the late Neogene.