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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 57 (1973)

Issue: 4. (April)

First Page: 777

Last Page: 778

Title: Quantitative Petrology and Depositional Environments Within Essentially Isochronous Units of Detrital Sediment, Upper Devonian, New York: ABSTRACT

Author(s): Frank G. Ethridge

Article Type: Meeting abstract


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Previously studied sedimentary environments and time-stratigraphic relations in the Sonyea Group (Upper Devonian) and adjacent units of New York provide an excellent framework for examining the effects of transport distance and environment of deposition on sediment composition and texture within an essentially isochronous unit of detrital sediment.

Samples for this study consist of 250 thin sections from 54 exposures and 12 environments of deposition, ranging from nonmarine to marine-slope and basin. Preliminary petrographic analyses reveal the following basinward trends: (1) fine-grained, foliated metamorphic rock fragments, a common constituent of the nonmarine sediments, are almost totally absent from sediments of the marine shelf, slope, and basin; (2) mean size of quartz grains ranges from fine sand in nonmarine environments to coarse silt in basin turbidites, whereas the maximum size ranges from granule to fine sand; (3) percentages of matrix range from 20% in nonmarine to over 80% in prodelta sediments; (4) rock fragments, including polycrystalline quartz, vary from 50% in nonmarine sediments to 4% in basin trubidites; an (5) monocrystalline quartz ranges from 23% in nonmarine sediments to over 40% in delta-front sediments.

In addition to these general trends, different sedimentary environments with similar mean sizes of quartz grains are distinguished on the basis of differences in petrology and size distributions of quartz grains. For example, fluvial floodplain, estuary, delta-channel, and delta-front environments, all having a very fine mean size of quartz grains, show significant differences in percentages of quartz, rock fragments, and matrix, or in the nature of the size distributions of quartz grains.

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Copyright 1997 American Association of Petroleum Geologists