Sequence-stratigraphic implications of glacial-eustatic Pennsylvanian cyclothems in North America

Conference · Mon Feb 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6002800

Heckel, P H ^[1]

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1. 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-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:1; Conference: 27. annual Geological Society of America (GSA) South-Central Section meeting, Fort Worth, TX (United States), 15-16 Mar 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC DEPOSITS
DEPOSITION
STRATIGRAPHY
NORTH AMERICA
AGE ESTIMATION
CARBONIFEROUS PERIOD
COAL
GLACIERS
LIMESTONE
SEA LEVEL
SHALES
VARIATIONS
CARBONACEOUS MATERIALS
CARBONATE ROCKS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGY
LEVELS
MATERIALS
PALEOZOIC ERA
ROCKS
SEDIMENTARY ROCKS
580000* - Geosciences