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Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania

Anna K. Wendt, Mike A. Arthur, Rudy Slingerland, Daniel Kohl, Reed Bracht and Terry Engelder
Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania (in Organic-rich shales, Anonymous)
Interpretation (Tulsa) (August 2015) 3 (3): SV17-SV33


Debate continues over paleoenvironmental conditions that prevail during deposition of organic-carbon (C)-rich marine source rocks in foreland basins and epicontinental seas. The focus of disagreement centers largely on paleowater depth and the prevalence of anoxia/euxinia. The issues of paleodepth and water column conditions are important for prediction of lateral variations in source quality within a basin because the viability of a hydrocarbon play depends on a thorough understanding of the distribution of source rock quality and depositional environments. We used inorganic geochemical data from the Middle Devonian Marcellus Shale in the Appalachian Basin to illustrate interpretive strategies that provided constraints on conditions during deposition. Source evaluation typically relies on the analysis and interpretation of organic geochemical indicators, potentially also providing evidence of the degree of thermal maturity and conditions of the preservation of the organic matter. The Marcellus Formation is thermally mature, making the evaluation of the organic-carbon fraction for geologic interpretation inadequate. Because most labile organic matter has largely been destroyed in the Marcellus Formation, analysis of inorganic elements may be used as an alternative interpretative technique. Several inorganic elements have been correlated to varying depositional settings, allowing for their use as proxies for understanding the paleodepositional environments of formations. A high-resolution geochemical data set has been constructed for the Union Springs Member along a transect of cores from proximal to distal in the Appalachian Basin in central Pennsylvania using major, minor, and trace elemental data. Our results suggested that during deposition, the sediment-water interface, and a portion of the water column, was anoxic to euxinic. As deposition continued, euxinia was periodically interrupted by dysoxia and even oxic conditions, and a greater influx of clastic material occurred. Such variations were likely related to fluctuations in water depth and progradation of deltaic complexes from the eastern margin of the Appalachian Basin.

ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 3
Serial Issue: 3
Title: Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania
Title: Organic-rich shales
Affiliation: Pennsylvania State University, Department of Geosciences, University Park, PA, United States
Pages: SV17-SV33
Published: 201508
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 68
Accession Number: 2015-073882
Categories: Economic geology, geology of energy sourcesGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., sketch map
N39°43'00" - N42°17'60", W80°31'60" - W74°40'00"
Secondary Affiliation: Chevron Corporation, USA, United StatesHess Corporation, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201532
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