Middle and Late Pennsylvanian cyclothems,American Midcontinent: Ice-age environmental changes and terrestrial biotic dynamics |
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| Institution: | 1. U.S. Geological Survey, 425 Brownsburg Turnpike, Rockbridge Baths, VA 20743, United States;2. Department of Paleobiology MRC-121, NMNH Smithsonian Institution, Washington, DC 20560, United States;3. Illinois State Geological Survey, University of Illinois, Champaign, IL 61820, United States |
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| Abstract: | The Pennsylvanian portion of the Late Paleozoic Ice Age was characterized by stratigraphic repetition of chemical and siliciclastic rocks in the equatorial regions of the Pangean interior. Known as “cyclothems”, these stratigraphic successions are a 105 yr-record of glacial waxing and waning, superimposed on longer term, 106 yr intervals of global warming and cooling and a still longer term trend of increasing equatorial aridity. During periods of maximum ice–minimum sea level, the interior craton was widely exposed. Epicontinental landscapes were initially subjected to dry subhumid climate when first exposed, as sea level fell, but transitioned to humid climates and widespread wetlands during maximum lowstands. During interglacials (ice-minima) seasonally dry vegetation predominated. The wetland and seasonally dry biomes were compositionally distinct and had different ecological and evolutionary dynamics. |
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| Keywords: | Climate Coal Cyclothem Paleoecology Pennsylvanian |
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