Pennsylvanian tectonic and depositional history, southern Ozark dome, Arkansas and Missouri
- Univ. of Arkansas, Fayetteville, AR (United States). Dept. of Geology
- Arkansas Mining Inst., Russellville, AR (United States)
Pennsylvanian strata of the southern Ozarks comprise only the Morrowan and Atokan Series, although beds of Desmoinesian age occur in the Arkoma Basin. Significant, regional unconformities occur at the Mississippian-Pennsylvanian boundary, within the upper Morrowan Series, and at the Morrowan-Atokan boundary. The Mississippian-Pennsylvanian boundary is an angular unconformity, representing the first loading of the crust by the rising Ouachitas. Beds of the basal Morrowan Series (Hale Formation) onlap progressively older Mississippian (Chesterian) units (Pitkin Limestone or older Fayetteville Shale) from south to north across the southern Ozarks. An intraformational unconformity occurs in the type Morrowan succession of northern Arkansas at the base of the dye Member, Bloyd Shale. It is associated with a pronounced facies change from shallow carbonates in northeastern Oklahoma, to coal-bearing shales in the type region (Washington County, Arkansas), to massive sandstones representing braided streams in north-central and northeastern Arkansas. The duration of the unconformity increases with the facies change eastward, involving units as old as Mississippian. Tectonism is not indicated; the break appears to be entirely eustatic, probably related to glaciation. The Morrowan-Atokan boundary exhibits some regional tilting associated with an off-lapping depositional sequence. An emergent Ozark Dome is indicated by detrital ore minerals in basal Atokan strata of the Arkoma Basin and Atokan chert breccias. Ouachita orogenic movement deformed all Pennsylvanian strata of the Arkoma Basin and raised the Ozark Dome, never allowing for coverage of the Ozarks by epicontinental seas again.
- OSTI ID:
- 7069838
- Report Number(s):
- CONF-9303210--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:3; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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