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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 51 (1967)

Issue: 3. (March)

First Page: 477

Last Page: 477

Title: R-Mode Factor Analysis of Cincinnatian (Upper Ordovician) Limestones: ABSTRACT

Author(s): Robert H. Osborne

Article Type: Meeting abstract

Abstract:

An R-mode factor analysis based on 20 petrographic variables observed in thin sections of 60 Cincinnatian biomicrosparrudites was made to determine genetic relations among several limestone classes. Thin sections were used for point-count estimates of whole and broken brachiopod grains, whole and broken bryozoan grains, disarticulated crinoid columnals, whole gastropods, and broken trilobite carapaces, as well as matrix (micrite and enclosed dolomite) and sparite. The correct volume of each measured variable lies within 5 per cent on each side of the obtained value with a 95 per cent confidence. The weight percentage of insoluble residue contained in each limestone sample also was determined. These measurements were combined into a 20 × 60 data matrix. The product-mo ent correlation coefficient was computed for each pair of variables, and the results were arranged in a 20 × 20 correlation matrix. Five statistically significant factors were extracted from the correlation matrix, which account for 82 per cent of the total variance. The geologic interpretations of the factor axes in order of extraction (decreasing significance) are: (1) mechanical energy gradient at the depositional site, (2) substrate firmness, (3) degree of lithification, (4) relative contributions of carbonate mud and skeletal grains to the sediment, and (5) Eh at or slightly below the depositional interface.

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Copyright 1997 American Association of Petroleum Geologists