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Geochemical insights into provenance of the Middle Devonian Hamilton Group of the central Appalachian Basin, U.S.A.

Brittany N. Hupp and Amy L. Weislogel
Geochemical insights into provenance of the Middle Devonian Hamilton Group of the central Appalachian Basin, U.S.A.
Journal of Sedimentary Research (October 2018) 88 (10): 1153-1165

Abstract

In order to better understand the relationship of clastic influx and organic-matter accumulation and preservation in the Middle Devonian Acadian foreland basin, we conducted a high-resolution provenance analysis of a composite section of the Hamilton Group. The Hamilton Group includes the organic-rich Marcellus Shale, one of the most lucrative unconventional shale gas plays in the world, and the overlying Mahantango Formation. Geochemical analysis of 121 samples from two nearby wells in Monongalia County, West Virginia, reveals subtle changes in clay provenance throughout deposition of the Marcellus Shale and the Mahantango Formation. Major-element and trace-element geochemistry suggest derivation from a felsic igneous, granodioritic, upper-continental crustal source with additional influx from a recycled quartzose sedimentary source. All weathering indices indicate increasing chemical weathering intensities throughout deposition of the Marcellus Shale, followed by consistently moderate chemical weathering associated with accumulation of the Mahantango Formation. Sm-Nd isotopic analysis of ten samples throughout the Hamilton Group yield epsilon Nd values ranging from -7.06 to -11.75, and Nd depleted-mantle model ages (tau DM) ranging from 1.63 to 1.85 Ga, with ages becoming younger upsection. Our results suggest that the extrabasinal detritus of the Hamilton Group originated from a mixed sediment source, with clay influx from both rocks associated with the Superior Craton to the north and northwest (tau DM > 2.7 Ga) and Grenville-sourced sediments derived from the adjacent Acadian fold-thrust belt to the east (tau DM approximately 1.4-1.6 Ga). Older Sm-Nd model ages, felsic composition, and evidence of sediment recycling suggest little to no contribution from the Acadian volcanic arc, indicating that volcanic tuff of the Tioga ash beds represent isolated episodes of volcanic input into the basin. Model ages, epsilon Nd values, and trace-element geochemistry indicate increased sediment influx from the Acadian fold-thrust belt throughout deposition of the Hamilton Group, with the highest sediment influx having occurred during Mahantango Formation deposition. Increased clay influx from sediment shed off from the Acadian fold-thrust belt associated with marginal marine regression increased delivery of clastic detritus, diluting the flux of organic matter and likely disrupting basin water stratification that aided in preservation of organic matter in the lower Marcellus Shale. The Middle Devonian Acadian Basin serves as an example of the influence of detrital influx on organic-matter accumulation and preservation in mud-dominated depositional systems.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 88
Serial Issue: 10
Title: Geochemical insights into provenance of the Middle Devonian Hamilton Group of the central Appalachian Basin, U.S.A.
Affiliation: West Virginia University, Department of Geology and Geography, Morgantown, WV, United States
Pages: 1153-1165
Published: 201810
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 92
Accession Number: 2019-002015
Categories: Geochemistry of rocks, soils, and sedimentsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., 2 tables, sketch map
N39°25'00" - N39°43'00", W80°25'00" - W79°46'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 2019
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