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Biostratinomic Utility of Archimedes in Environmental Interpretation
Julie Iris Wulff
Vol. 5, No. 2 (Apr., 1990), pp. 160-166
Published by: SEPM Society for Sedimentary Geology
Stable URL: http://www.jstor.org/stable/3514812
Page Count: 7
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Biostratinomic information from the bryozoan Archimedes can be used to infer paleocurrent "senses" when other more traditional sedimentary structures are lacking. As with other elongate particles, Archimedes zooaria become oriented in the current and, upon settling, preserve a sense of the flow direction. Orientations and lengths were measured on over 200 individuals from bedding plane exposures in the Upper Mississippian Union Limestone (Green-brier Group) of West Virginia. These were separated into long and short populations and plotted on rose diagrams. The results show that long and short segments become preferentially oriented in the current and the bimodally distributed long segments can be used to infer the current sense. The current sense is defined by the line which bisects the obtuse angle created by the two maxima in the rose diagram for long segments. Statistical evaluation of the long and short populations indicate they are significant to the 99.9 percent level. Elongate fossils such as Archimedes can be used in paleocurrent evaluations and can add more detail to the interpretation of paleodepositional conditions.
PALAIOS © 1990 SEPM Society for Sedimentary Geology