Cyclothems of the Black Warrior Basin, Alabama, U.S.A.: Eustatic Snapshots of Foreland Basin Tectonism
Jack C. Pashin, 2004. "Cyclothems of the Black Warrior Basin, Alabama, U.S.A.: Eustatic Snapshots of Foreland Basin Tectonism", Sequence Stratigraphy, Paleoclimate, and Tectonics of Coal-Bearing Strata, Jack C. Pashin, Robert A. Gastaldo
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Flooding-surface-bounded depositional cycles were used to make three-dimensional models of total effective subsidence in the lower Pennsylvanian Pottsville Formation of the eastern Black Warrior Basin and demonstrate the utility of Pennsylvanian cyclothems for assessing controls on the development of accommodation space. The Black Warrior foreland basin underwent tectonic loading during Pottsville deposition, and the regional subsidence pattern reflects superposition of an Appalachian depocenter on an older Ouachita flexural moat. Modeling cycle duration within the constraints of biostratigraphy and foreland-basin geodynamics indicates a transition from dominant third-order cyclicity to dominant fourth- and fifth-order cyclicity that may be equivalent to the 0.4- and 0.1-m.y. Milankovitch orbital eccentricity periods. Changes in subsidence pattern from cycle to cycle are most pronounced in the distal part of the basin and reflect significant spatial and secular excursions of subsidence rate. These excursions indicate that high-frequency tectonic activity that generally has not been considered in stratigraphic and geophysical models of foreland basins can be detected by backstripping and mapping Pennsylvanian cyclothems.