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Larger Foraminifera: A Tool for Paleoenvironmental Analysis of Cenozoic Carbonate Depositional Facies

1986; Society for Sedimentary Geology; Volume: 1; Issue: 1 Linguagem: Inglês

10.2307/3514459

1938-5323

Pamela Hallock, Equisha Glenn,

Geological and Geophysical Studies

Previous studies of test shape and distribution trends of reefassociated Foraminiferida provide the basis for a model of foraminiferal distribution in Cenozoic carbonate depositional facies. The model predicts distributions offoraminifera in Wilson's Standard Carbonate Facies. Basinal sediments from above the calcium carbonate compensation depth will contain predominantly low latitude planktonic foraminifera with a minor component of deeper benthic species. Open shelf and toe of reef slope sediments from euphotic zone depths will be visually dominated by very large, flat, rotaliine foraminifera. Larger foraminifera of carbonate foreslope environments are of intermediate thicknesses; total foram faunas of foreslope and ecologic reef are typically diverse. Shelf edge sands are often concentrations of tests of large, robust, subspheroid rotaliine species. Open carbonate platform sediments are characterized by robust to intermediate rotaliines and soritids. Lagoons and other restricted carbonate shelf environments of normal or hypersalinity are dominated by miliolids, peneroplids and small rotaliines. This model, when tested on thin sections cut from lower Miocene carbonate cores from four Philippine wells, enhanced the paleoenvironmental analysis and interpretation developed using standard petrographic techniques. The model is based upon recognition of three major groups of easily recognizable foraminifera: 1) thin, larger, rotaliineforaminifera plus planktonics, 2) ovate, larger rotaliines, and 3) miliolines and smaller rotaliines. The relative percentages of these environmentally diagnostic foraminifera, when plotted on triangular diagrams, provide graphic indication of paleoenvironment.