2008 Alaska Park Science Symposium
October 14, 2008
Beringia from a Cretaceous Perspective
Anthony R. Fiorillo1, David W. Norton2, Paul J. McCarthy3
1Paleontology, Museum of Nature and Science, P.O. Box 151469, Dallas, TX, 75315, USA, tfiorillo@natureandscience.org
2Arctic Rim Research, 1749 Red Fox Drive, Fairbanks, AK, 99709, USA, Phone 907-479-6898, Fax 907-479-5313, arcrim@ptialaska.net
3Geology and Geophysics, University of Alaska Fairbanks, Fairbanks, AK, 99775-5780, USA, Phone 907-474-6894, mccarthy@gi.alaska.edu
National Park Service units in Alaska contain some of the most informative fossil-bearing rocks anywhere in North America. What makes some of these Alaska rocks especially valuable is their location within the dynamic subcontinental region denoted by “Beringia.” By linking similar aged rocks within the National Park Service lands together with the fossil resources found on other public lands administered by federal agencies, additional paleoecological insights on specific ecosystems can be obtained. Here we address the antiquity of terrestrial Beringian ecosystems and the implications of this antiquity.
The concept of Beringia as primarily a Quaternary phenomenon depends entirely on the mechanism by which glacial advances and retreats account for reciprocal drops and rises in sea level. These climate-induced changes alternated over time. High sea levels facilitated exchanges of marine biota between the Pacific Ocean and Arctic Basin; lower sea levels enabled terrestrial faunal and floral exchanges between Asia and North America. Recent advances in resolution of geochronologic methods suggest that climate-driven sea level changes have been relatively recent and weak determinants of biogeographic patterns—an epilog to a longer planetary story.
Beringian ecosystems have fostered specializations of flora and fauna over time, as is especially evident among those vertebrates that leave abundant fossils. Striking faunal and floral structural parallels in ecosystems are manifest in the Cretaceous of this region. Current paleontological investigations on correlative fossil-bearing rocks in Yukon-Charley Rivers National Preserve, Denali National Park and Preserve, and on Alaska’s North Slope, combined with revised tectonic reconstructions of the region lead us to conclude that Beringia became an identifiable region with the bridging of Eurasian and North American plates, some 100 million years ago. This extension of Beringia back in time requires a reordering of the importance we assign to underlying mechanisms. Atmospheric and oceanic phenomena became significant as climatic determinants of cyclic changes in Beringia during the Quaternary. Accepting Beringia’s accretionary origins in the Cretaceous, however, implies that Beringia is rooted in its tectonic, rather than its climatic, history.
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