Paper No. 8
Presentation Time: 10:15 AM
LATE NEOGENE DRY CLIMATE CONDITION IN THE SOUTHERN APPALACHIANS
LIU, Yusheng (Christopher), Biological Sciences, East Tennessee State University, 100 CR Drive, Johnson City, TN 37614 and QUAN, Cheng, Research Center of Paleontology & Stratigraphy, Jilin University, China, 938, Xi-minzhu Str, Changchun, 130026, China, liuc@etsu.edu
A Neogene site from northeast Tennessee has yielded well preserved floral and mammal remains, demonstrating a unique combination of North American and Eurasian biota in a forest-woodland and a window for understanding the terrestrial Neogene climate conditions in southeastern North America. Fossil vertebrates from the site support the late Hemphillian Land Mammal Age (the latest Miocene to earliest Pliocene, viz. 7 ~ 4.5 my). 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 55 genera, representing more than 25 families of seed plants. Based on the nearest living counterpart comparisons, these fossils can be identified with certainty to their specific modern genera. 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:
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Temperature (oC)
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Precipitation (mm)
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Mean annual
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ColdMonth
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WarmMonth
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Mean annual
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WettestMonth
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DriestMonth
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WarmestMonth
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Paleoclimate at the site
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13.6-17.6
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5.5-7.1
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24-27.5
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979-1551
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148-195
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18-24
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120-176
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Current climate of site
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13
|
-4 -1
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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 (likely last fall to 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 much more seasonal in the late Neogene than that of today.
