Desmoinesian sedimentary history of the northern flank of the Ozark uplift
- Illinois State Univ., Normal, IL (United States). Dept. of Geography-Geology
The structural framework of the northern flank of the Ozark Uplift during Desmoinesian time was a gradually subsiding platform connecting the Forest City Basin with the Illinois Basin through the St. Louis Depression. The platform was bounded on the northeast and southwest by major lineaments and was internally broken into numerous rigid crustal blocks by northwest- and northeast-trending lineaments. Depositional patterns of the thin cyclic strata, ranging in thickness from a few to several hundred centimeters, were controlled by vertical or rotational movements of these blocks. Pennsylvanian sediments were deposited on an erosion surface cut into Mississippian rocks. This surface is characterized by broad shallow valleys and numerous karst features. The first Pennsylvanian deposits were conglomerates derived from Mississippian chert, and are overlain by the Cheltenham clay. Desmoinesian sediments unconformably overlie the Cheltenham clay in a transgressive sequence from northwest to southeast. Several Desmoinesian cycles present on the western flank of the Ozark Uplift are absent on the northern flank. These cycles are represented by a thickening of the underclays of the Tebo, Croweburg, Wheeler, and Mulky coals which rest on the Cheltenham. Cycles between the Tiawah Limestone and the underclay of the Croweburg Coal are absent. Although abrupt local changes in thicknesses of individual lithotypes are related to movements of rigid blocks, some regional depositional patterns are identifiable. Strata from the base of the underclay of the Tebo Coal through the Lagonda Formation thin and pinch out from northwest to southeast Post-Lagonda strata through the Blackjack Creek Limestone thicken from northwest to southeast. Post-Lagonda deposits are preserved in scattered localities, making definitive interpretations difficult.
- OSTI ID:
- 7206955
- Report Number(s):
- CONF-9303210-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:3; Conference: 27. annual Geological Society of America (GSA) North-Central Section meeting, Rolla, MO (United States), 29-30 Mar 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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