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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 721

Last Page: 721

Title: Paleogeography of Eustatic Model for Deposition of Mid-Continent Upper Pennsylvanian Cyclothems: ABSTRACT

Author(s): Philip H. Heckel

Article Type: Meeting abstract

Abstract:

The hypothesis that eustatic sea level changes formed Upper Pennsylvanian cyclothems in Mid-Continent North America has been supported by recent documentation of many episodes of Mississippian through Permian glaciation in Gondwanaland. Changes in Mid-Continent paleogeography and sedimentation during a single eustatic advance and retreat are described in 6 phases. (1) At maximum transgression, deep water promoted development of a thermocline, quasi-estuarine circulation, and upwelling, all leading to widespread deposition across the Mid-Continent of phosphatic black shale, which graded in shallower peripheral areas to gray marine shale and carbonates. (2) Progressive shallowing during early regression destroyed the thermocline, restored bottom oxygenation, and caused depo ition of gray shale, and then algal-skeletal calcilutite. Deltas began prograding from Oklahoma and the Appalachians, and shoreline carbonates began prograding southward from the Dakotas. (3) During late regression extensive shoal-water calcarenites developed over most of Kansas, carbonate shoreline facies prograded into southern Nebraska and Iowa, and deltas of Appalachian origin prograded across Illinois. (4) At maximum regression, the sea was confined to the deep basins of west Texas and Oklahoma. Karst, caliche, and residuum developed on the exposed carbonate terrane to the north. The extensive deltaic deposits to the east underwent channeling, alluviation, and soil formation. (5) Expansion of the sea during early transgression restored shoal-water calcarenite deposition across weste n Kansas, caused gray shale deposition in embayments and lagoons along the inundated deltaic terrane to the east, and impounded Appalachian-derived streams flowing westward across the immense alluvial plain to form widespread coal swamps in Illinois. (6) During late transgression deeper seas restored skeletal calcilutite deposition across the Mid-Continent, caused marine shell accumulations over coals in Illinois, and shifted coal swamp formation eastward into the Appalachian region.

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