|
|||||
|
|
Plio-Pleistocene climatic transition and the lifting of the Teton Range, Wyoming |
|
| Authors: | Estella B Leopold Gengwu Liu David W Love |
| Institution: | a Department of Biology, Quaternary Research Center, University of Washington, Box 351310, Seattle, WA 98105, USA b Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing 210008, PR China c U.S. Geological Survey, Laramie, WY, USA d New Mexico Bureau of Mines, Institute of Mining and Technology, Socorro NM 87801-4681, USA |
| Abstract: | Fine-grained lacustrine, riverine and ash-fall sediments of the Shooting Iron Formation, whose late Pliocene age is established by Blancan gastropods and vertebrates, yield a pollen flora that is essentially similar in composition to the modern pollen rain in the Jackson Hole area. The Pliocene assemblage suggests a climate like that of the Jackson valley and foothills today. These spectra also resemble a Pliocene pollen flora from Yellowstone Park dated at ∼ 2.02 Ma. However, the underlying Miocene Teewinot sediments differ by containing pollen of four exotic deciduous hardwoods (Tertiary relicts) that suggest a summer-moist climate, unlike that of today. The Shooting Iron sediments lie with an angular unconformity on and above the Miocene lake sediments of the Teewinot Formation. Both of these deposits probably preceded the main uplift of the Teton Range based on the absence of Precambrian clasts in the Tertiary valley deposits. Because the Pliocene floras were modern in aspect, a Plio-Pleistocene transition would be floristically imperceptible here. The sequence denotes a protracted period of relative stability of climate during Teewinot time, and a shift in vegetational state (summer-wet trees drop out) sometime between the latest Miocene and latest Pliocene. The Pliocene spectra suggest a dry, cooler climate toward the end of Shooting Iron time. |
| Keywords: | Plio-Pleistocene transition Pliocene pollen Climate shift Teton Range Shooting Iron Formation Mountain uplift |
| 本文献已被 ScienceDirect 等数据库收录！ | |