Early rift-basin deposition: Triassic-Jurassic sedimentation and subsequent diagenesis in the Newark Basin, New Jersey.
Item
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Title
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Early rift-basin deposition: Triassic-Jurassic sedimentation and subsequent diagenesis in the Newark Basin, New Jersey.
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Identifier
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AAI9432339
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identifier
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9432339
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Creator
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El Tabakh, Mohamed Elsayed.
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Contributor
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Adviser: B. Charlotte Schreiber
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Date
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1994
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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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Geochemistry | Geology | Hydrology
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Abstract
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The sedimentary characteristics of the Late Triassic sedimentary sections (7 km) of the Newark rift basin of eastern North America seen in the subsurface of New Jersey exhibit a great diversity of depositional environments, lithological associations, and authigenic mineral assemblages. The studied sedimentary section (Newark Supergroup) includes fluvial-alluvial deposits (Stockton Formation), lacustrine depositional cycles (Lockatong Formation), and massive red mudstones and associated evaporites (Passaic Formation).;Within the sediments of the Newark Supergroup there is lithologic and geochemical evidence that indicates changes of the depositional system through time and that regional and later paleofluid movements have mobilized some components of the original lithologies. Depositional changes were mostly related to variations in the original paleoclimatic and tectonic conditions that have affected the basin during its sedimentary evolution.;The Stockton Formation (1800 km) is the early rift basin sedimentary phase, consisting of conglomerates, sandstones and shelly mudstones that contain nodular carbonates (calcrete), arranged in repeated packages of upward fining sequences. The formation is characterized by an overall upsection decrease in grain size. Several distinct diagenetic features are seen within the calcrete and the mudstone lithologies. These features include early diagenetic cementation by calcite, displacive development of nodular calcite along root and burrow traces, and calcite replacement of some clays within the mudstone. Later diagenetic alteration includes albitization of some calcite in calcrete and the transformation of illitic clays into 2M-illite (muscovite). The late authigenic mineralogy resulted from circulation of hot basinal diagenetic fluids which altered and remobilized components of the original mineral assemblage, and apparently did not bring in a significant volume of new ions.;Lockatong Formation (1.1 km) includes organic-rich shales and carbonates. Isotopic data of the lacustrine carbonates indicate that the carbonates are largely primary in origin and that their original isotopic signatures have not been significantly modified by later diagenetic fluids. This is because the sedimentary porosity and permeability were reduced at an early stage of deposition, due to the synsedimentary alteration of clays to analcime which infilled the original porosity of the sediments.;Within the Passaic Formation (3,500 m) there is evidence of an upward progressive increase in the deposition of evaporites. Evaporites were formed displacively within the soft muds of shallow lakes and playas that occupied the rift-basin. Evaporite formation was probably due to progressive concentration of dissolved sulfates in the basin both due to an upward increase in aridity and an increase in basinal depositional area through time. During later diagenetic events (post Middle Jurassic to Modern), evaporites were exposed to extensive dissolution and remobilization that caused the formation of fibrous gypsum cements.
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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.
