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Characterization and development of subsurface fractures observed in the Marcellus Formation, Appalachian Plateau, north-central Pennsylvania

Scott Wilkins, Van Mount, Keith Mahon, Andrew Perry and Jon Koenig
Characterization and development of subsurface fractures observed in the Marcellus Formation, Appalachian Plateau, north-central Pennsylvania
AAPG Bulletin (November 2014) 98 (11): 2301-2345

Abstract

We report on subsurface deformation features measured from recently acquired core and image logs from the Marcellus Formation in north-central Pennsylvania, supplemented with data collected from Valley and Ridge outcrop. The subsurface data are from an area that bridges a gap in existing published data between outcrop in the Valley and Ridge province of Pennsylvania and the relatively undeformed outcrop exposed on the Appalachian Plateau of New York. We find one distinct set of vertical veins that strike orthogonal to Appalachian Plateau fold axes and an associated set of low-angle reverse faults and stylolites that strike parallel to fold axes. As the trend of the fold axes changes around the Pennsylvania salient, the trend of associated mesostructures changes to maintain kinematic compatibility with the shortening direction change along the salient. These structures are interpreted to support a single, although possibly protracted, strain event during Alleghanian deformation, as opposed to multiple events previously interpreted to occur in different regions and stratigraphic levels within the fold belt. The veins are associated with clusters of bedding-plane slip surfaces, which are found at distinct mechanical stratigraphic positions where the competence contrast between shale and stiff limestone units is greatest. We interpret this association to indicate that bed parallel-shear within detachment zones provides the sufficient driving force required to nucleate vertical veins, and the decoupling of beds accommodates extension orthogonal to the shortening direction. Although these veins are oriented orthogonal to the present-day maximum principal horizontal stress, they remain propped open by crystalline cements. Homogenization temperatures of fluid inclusions trapped in the veins, combined with one-dimensional burial and thermal history models, suggest that the pervasive vein set formed during the Late Pennsylvanian-Permian during the Alleghanian orogeny.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 98
Serial Issue: 11
Title: Characterization and development of subsurface fractures observed in the Marcellus Formation, Appalachian Plateau, north-central Pennsylvania
Affiliation: Anadarko Petroleum Corporation, Geoscience Technology Group, The Woodlands, TX, United States
Pages: 2301-2345
Published: 201411
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 67
Accession Number: 2014-091710
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diag., 4 tables, sketch maps
N40°30'00" - N45°00'00", W79°45'00" - W71°55'00"
N39°43'00" - N42°17'60", W80°31'60" - W74°40'00"
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 American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 201448
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