Sequence-stratigraphic implications of glacial-eustatic Pennsylvanian cyclothems in North America
- Univ. of Iowa, Iowa City, IA (United States). Dept. of Geology
Only glacial eustasy accounts for all characteristics of Pennsylvanian northern Midcontinent cyclothems that consist of transgressive limestone, offshore ( core') shale, regressive limestone, and variable nearshore to terrestrial shale. Because of the rapidity of glacial eustatic fluctuations of sea level relative to tectonic movements of the shelf or to sediment filling of the large accommodation space provided by sea-level highstand, sequence-stratigraphic concepts and terminology require modification for these cyclothems. It is mainly the condensed intervals of sediment-starved, phosphate- and conodont-rich core shales that represent true highstand deposits on the mid to lower shelf (which is all that is presently preserved). The basic cyclothem was modified in Texas and Illinois by detrital overwhelming of regressive limestone deposition from nearer sources, but similar widespread condensed intervals still represent most of highstand. Higher shelf deposits are preserved in the Appalachian basin where phosphate- glaucony- and conodont-rich Conemaugh marine limestones represent highstand deposits in shallower water. These are penetrated locally eastward by deltaic clastics, which also represent highstand as well as early regression. Later regression involved greater fluvial incision, local terrestrial deposition and widespread paleosol formation, which continued through lowstand and early transgression. Late transgression produced widespread coal swamps, migrating ahead of inundation as a result of rising water table and increasing source of rainfall.
- OSTI ID:
- 6002800
- Report Number(s):
- CONF-9303212--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:1; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Petrology and depositional significance of Conemaugh marine units in the Appalachian Basin
Biostratigraphic correlation of eustatic cyclothems (basic Pennsylvanian sequence units) from Midcontinent to Texas and Illinois
Related Subjects
580000* -- Geosciences
AGE ESTIMATION
CARBONACEOUS MATERIALS
CARBONATE ROCKS
CARBONIFEROUS PERIOD
COAL
DEPOSITION
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
GLACIERS
LEVELS
LIMESTONE
MATERIALS
NORTH AMERICA
PALEOZOIC ERA
ROCKS
SEA LEVEL
SEDIMENTARY ROCKS
SHALES
STRATIGRAPHY
VARIATIONS