Geology of parts of the Peach Lake and Brewster quadrangles, southeastern New York and adjacent Connecticut, and basement blocks of the north-central Appalachians. (Volumes I and II).
Item
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Title
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Geology of parts of the Peach Lake and Brewster quadrangles, southeastern New York and adjacent Connecticut, and basement blocks of the north-central Appalachians. (Volumes I and II).
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Identifier
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AAI9325069
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identifier
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9325069
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Creator
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Brock, Pamela Jean Chase.
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Contributor
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Adviser: Allan Ludman
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Date
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1993
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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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The three parts of this thesis have different focuses. Part I covers the bedrock geology of parts of the Peach Lake and Brewster quadrangles (New York - Connecticut). New interpretations of the stratigraphy, structural development, and metamorphic history of the northeastern Manhattan Prong are proposed. In Part II, a compilation of isotopic data from the north-central Appalachians is used to define five fundamental basement blocks (two juvenile, three of ancient continental crust). Part III builds upon compiled geologic data to infer the timing of the accretion of these blocks, and to model the Acadian orogeny.;Part I presents a newly recognized, rift-related Eocambrian unit, the Ned Mountain Formation (NMF). The NMF consists of bimodal metavolcanic rocks, meta-arkoses, meta-wackes, and calc-silicate rocks which crop out between the Grenvillian Fordham Gneiss and the Cambro-Ordovician Inwood Marble. The NMF is subdivided into a graphitic Basal Member, a Volcaniclastic Member (including "Pound Ridge granite"), Wacke Member, and an uppermost Calc-Silicate Member (including "Lowerre Quartzite"). NMF strata are compositionally distinct in many respects from rocks of other formations. Reconnaissance transects outside the study area confirm persistence of the NMF over a large area.;Six episodes of Paleozoic deformation are recognized in the study area. The Hartland terrane was emplaced over the Manhattan Prong during (Taconian) D{dollar}\sb1{dollar}; D{dollar}\sb2{dollar} backfolding produced a series of large folds, which were later deformed around northeast-striking F{dollar}\sb3{dollar} hinge surfaces. Minor recumbent D{dollar}\sb4{dollar} folding and shearing followed. The last two events involved Carboniferous ductile faulting: first, normal-sense shearing was accompanied by a syntectonic suite of two-mica granites (previously dated as Mississippian); later, east-directed thrusting produced mylonites that yield Pennsylvanian K-Ar mica ages.;Three principal metamorphic events are recognized: granulite-facies M{dollar}\sb1{dollar} (syn-D{dollar}\sb1{dollar}), upper-amphibolite facies M{dollar}\sb2{dollar} (late-Taconian), and greenschist- to middle-amphibolite facies M{dollar}\sb3{dollar} (Mississippian). M{dollar}\sb2{dollar} and/or M{dollar}\sb3{dollar} retrogression commonly obliterates evidence for M{dollar}\sb1{dollar}. However, inclusions in garnets indicate high pressures ({dollar}>{dollar}12 kb) for early-M{dollar}\sb1{dollar}, and relict spinel + quartz assemblages imply peak-M{dollar}\sb1{dollar} temperatures approaching 1000{dollar}\sp\circ{dollar}C.;The model developed in Parts II and III places the Manhattan Prong into regional geological context.
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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.
