Carbonate diagenesis and dolomitization of Cambro-Ordovician (Sauk Sequence) Platform strata in central New York.
Item
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Title
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Carbonate diagenesis and dolomitization of Cambro-Ordovician (Sauk Sequence) Platform strata in central New York.
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Identifier
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AAI9917685
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identifier
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9917685
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Creator
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Philips, Shruti Sarah.
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Contributor
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Adviser: Gerald M. Friedman
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Date
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1999
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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 | Geochemistry
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Abstract
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The Cambro-Ordovician platform carbonates exposed on the Saratoga Platform in central New York record a complex diagenetic history ranging from early peritidal dolomitization to late-diagenetic, deep-burial dolomitization. Stratigraphically, this sequence is distinguished here as the Upper Cambrian Little Falls, Galway and Hoyt formations and the Lower Ordovician Gailor and Tribes Hill formations.;The bulk of this sequence has been dolomitized. Stromatolites, intraclasts, fenestrae, herringbone cross strata, chert beds, dissolution-collapse breccia and stylolites are common features observed in this sequence. A peritidal environment of deposition is inferred for the entire sequence.;Cathodoluminescence petrography has revealed seven dolomite generations, which differ from one another in their crystal size, luminescence, trace-element content, and stable-isotope compositions. Four stages of dolomitization are recognized in the rocks studied. The first stage produced microcrystalline Dolomite(1) and fine-crystalline mosaics of Dolomite(2). The second stage was one of massive dolomitization that occurred in the subsurface during progressive burial and involved multiple episodes of textural and geochemical change, resulting in Fe- and Mn-rich, zoned, medium- to coarse-crystalline, planar-e to planar-p Dolomite(3) and nonzoned, xenotopic, medium- to coarse-crystalline mosaics of Dolomite(4). The third stage occurred with uplift of the basin, when Fe-poor, meteoric fluids produced bright, orange-luminescent Dolomite(5) cements. The fourth stage of dolomitization occurred in the deep subsurface, where subsurface brines precipitated Fe-rich Dolomite(6) (saddle dolomite) and Dolomite(7) cements in voids.;Compared to the early-diagenetic dolomites, the late-diagenetic dolomites are more stoichiometric, coarser, more depleted in delta18O and Sr2+, and more enriched in Fe2+ and Mn 2+. These geochemical differences imply that early dolomite generations formed from modified seawater in the depositional environment, whereas later-formed generations of dolomite formed by recrystallization or neomorphism of early formed dolomite, replacement of limestone at elevated temperatures, and cementation in fractures and secondary pores. The dolomite fabrics are also associated with dedolomite, chert, authigenic feldspar, and burial calcite.;The diagenetic sequence, that I have reconstructed in the platform strata is similar to that of the coeval rocks of the Appalachian fold-thrust belt exposed in eastern New York. This implies that the burial histories of the Sauk Sequence from these contrasting tectonic provinces, Saratoga Platform on the west and the Appalachian fold-thrust belt on the east were comparable.
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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.
