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Abstract Detail


Hamersma, Ashley [1], Manchester, Steven [2].

The Beaver Creek flora, a late Paleogene - early Neogene flora of southwestern Montana.

Present-day habitats of North America include regions displaying significant floristically disjunct components, with biogeographic disjunctions existing between eastern Asian, eastern North American, and western North American taxa. Phylogenetic, paleoclimatic and modeling studies of the areas have suggested a complex history leading to modern vegetation, with several temporally and spatially separated events contributing to changing phytogeography. Studies of extant taxa can be useful in delimiting modern arrangements, but fossil evidence is necessary in order to provide support and validate hypotheses. The late Oligocene - early Miocene vegetation of western North America experienced a unique climatic situation, with temperatures fluctuating near the boundary between ice-free and glacial conditions. Paleoclimate modeling of published localities in the area supports a highly heterogenous environment, with highland-basin dominated areas expressing significant altitudinal zonation. With this heterogeneity, a high-resolution fossil record is necessary to resolve patterns and trends. The Beaver Creek flora is a late-Paleogene or early-Neogene flora located in Powell County, southwestern Montana, in the Northern US Rocky Mountains. It preserves adpression fossils of leaves and reproductive structures in lacustrine shales, and represents a very different landscape from the conifer-dominated areas of today. The flora hosts several genera no longer present in modern local vegetation (e.g., Ginkgo, Lindera, Ulmus), and several genera that today show a strong disjunct east-Asian, east-North American distribution pattern (e.g., Cercis, Acer, Sassafras). Fossil material is described from collections made by Mr. Gary Eichhorn and colleagues and housed at the University of Florida. Characterization of this flora facilitates discussion of paleoclimatic and biogeographical change in the northern U.S. Rocky Mountains in Montana during a period of highly variable climate, and adds to the paleobotanical record of the area, with potential implications for the timing and processes of floristic disjunctions between North America and eastern Asia.

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1 - 730 NE 10th Ave, Apt B, Gainesville, FL, 32601, United States
2 - University of Florida, Museum of Natural History, 1659 Museum Road, Gainesville, FL, 32611, USA

none specified

Presentation Type: Oral Paper
Session: PL7, Paleobotany: Mesozoic/Cenozoic Paleobotany
Location: /
Date: Thursday, July 22nd, 2021
Time: 1:30 PM(EDT)
Number: PL7005
Abstract ID:1021
Candidate for Awards:None

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