Sandstone petrography and authigenic tourmaline from Lower to early Middle Devonian units of the Appalachian Basin, New York to West Virginia.
Item
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Title
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Sandstone petrography and authigenic tourmaline from Lower to early Middle Devonian units of the Appalachian Basin, New York to West Virginia.
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Identifier
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AAI3037440
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identifier
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3037440
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Creator
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Scal, Roland.
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Contributor
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Adviser: Gerald M. Friedman
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Date
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2002
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Language
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English
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Publisher
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City University of New York.
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Subject
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Geology
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Abstract
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Detrital tourmaline from the Onskany Sandstone is overgrown by authigenic tourmaline crystallogaphically aligned to the detrital core. Petrographic characterization was used to evaluate the origin of tourmaline in the Oriskany Sandstone and younger Middle Devonian units. The Oriskany is lithologically very homogeneous from New York to southern Virginia, suggesting it was derived from similar sources along almost its entire extent. A general paragenesis was derived for the unit. Only quartz overgowths are intergown with tourmaline overgrowths, and these composite gains can survive reworking. Abrasion of authigenic tourmaline indicates that it must have formed either very early before reworking or was derived from older Paleozoic sandstones. In New York some overgowths are euhedral and possibly neoformed, while in Virginia, West Virginia, and Maryland no unabraded tourmaline was found. Samples contained reworked overgowths that vary from unabraded to strongly abraded, suggesting variable transport and possible multiple reworking.;The overgrowth tourmaline is syntaxial schorl-dravite Na(Fe, Mg)3Al6(BO)3Si6O27 (O, OH, F), colorless to pale blue, and exhibits growth zones that vary in hue and refractive index. Overgrowths are up to several hundred microns in length parallel to the c-axis. Vanadium occurs in some of the New York overgrowths, and ranges appreciably from below detection to a few weight percent V 2O3 in different locations. Patterns of elemental zonation and chemistry are consistently similar in any location, but vary between outcrops, suggesting localized occurrences. These variations indicate that a similar set of environmental and postdepositional conditions is responsible for the many isolated incidents of growth, rather than a localized single event followed by redistribution. A general depletion of Fe and a tendency towards dravitic compositions occurs during growth, particularly in New York samples. Though southern samples and New York samples seem to begin formation with similar compositions, New York samples are chemically distinctive. Evidence, particularly from vanadium, suggests a deep burial formation for overgrowths from New York that could not happen if the overgrowths had formed in the Oriskany Sandstone.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
