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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)


Journal of Sedimentary Petrology
Vol. 43 (1973)No. 1. (March), Pages 137-146

The American Upper Ordovician Standard. XVII: Areal Variation of Limestone Frequencies in the Kope and Fairview Formations, Hamilton County, Ohio

Robert H. Osborne


Principal component analysis based on the frequency of limestone classes 1-2, 3, 4, 5, and 6 in 22 stratigraphic sections of the Kope Formation and in 18 sections of the Fairview Formation suggests three significant eigenvectors. The first vector shows a mutual exclusion between limestone classes 1-2 plus 5 and class 3, and is interpreted as representing differences in mechanical energy at the depositional site. The second vector is strongly related to class 4, and is interpreted as representing biogenic comminution of shell fragments. The third vector is strongly related to class 6, and is interpreted as representing bioturbation at the depositional site. Trend-surface analysis based on the frequency percent of classes 1-2 plus 5/ frequency percent class 3 at each section may be used to delimit the sites of relatively high and low mechanical energy, which are presumably coextensive with seafloor topographic highs and lows respectively. During deposition of the middle and upper Kope Formation, a north-northeast trending low extended across central Hamilton County, whereas a similar trending high occurred to the southeast. During deposition of the Fairview, a west-trending high occurred in southeast Hamilton County, whereas a northwest-trending low occurred to the northwest. Although intensive shoalling occurred in eastern Hamilton County during deposition of the Kope, the subtidal environments typical of the Kope and Fairview Formations were nearly identical.

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