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Documenting the Geometry and Magnitude of Shortening at the Allegheny Front: Lycoming County, Pennsylvania

Ace, Ashley (2016) Documenting the Geometry and Magnitude of Shortening at the Allegheny Front: Lycoming County, Pennsylvania. Master's Thesis, University of Pittsburgh. (Unpublished)

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The Appalachian Mountain belt extends through the eastern United States and into southeastern
Canada, and is expressed as elongated topographic ridges and valleys of folded and thrust faulted
sedimentary and crystalline rock. The Appalachian Plateau (AP) in northwest Pennsylvania, and
the Appalachian Valley and Ridge in southeastern Pennsylvania have pronounced differences in
geologic structure and topographic expression. The AP consists of gentle folds and low relief (but
higher elevation) topography, and 10-15 percent layer parallel shortening (LPS) in rocks sampled
at the surface. In contrast, the Valley and Ridge province is a blind fold and thrust belt. The
duplexing sequence in the Valley and Ridge is bound by a deep decollement surface within shales
of the Cambrian Waynesboro Formation, underlying a detachment at the base of the Ordovician
Reedsville shale. Twenty-four kilometers of shortening in the Cambrian – Ordovician sequence
is expressed as LPS in the AP. Due to the deficiency of geophysical and outcrop data, all the strata
in the AP above the Silurian salt detachment has been assumed to be shortening via LPS plus very
gentle folding. Increased hydrocarbon exploration has led to the acquisition of new high quality
3-D seismic and well log data which reveal that the strata from Silurian Salina Group through the
Devonian Marcellus shale is shortening through a variety of mechanisms including wedge-style
thrust faulting and folding. Through kinematically restored and balanced cross sections we show
that the magnitude of microscale shortening calculated from the rocks exposed at the surface of
the AP is equal to the magnitude of macroscale shortening in the Silurian-lower Devonian units
immediately above the salt detachment. Comparing our interpretations with previously published
seismic throughout the AP allows us to extend our model of how shortening in the Salina Group
through Marcellus shale is balanced by LPS in the rocks above the Marcellus shale to include the
extent of the previously published studies. As the hydrocarbon-rich Marcellus shale is a part of
this uniquely deforming Silurian-Devonian package, understanding the geometries of these
structures has a potential impact on the quality and quantity of hydrocarbon recovery.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ace, Ashleyasa92@pitt.eduASA920000-0001-9174-3026
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairMcQuarrie, Nadinenmcq@pitt.eduNMCQ
Committee MemberSak,
Committee MemberHarbert, Williamharbert@pitt.eduHARBERT
Date: 20 September 2016
Date Type: Publication
Defense Date: 27 June 2016
Approval Date: 20 September 2016
Submission Date: 17 July 2016
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 92
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Appalachian Plateau, Valley and Ridge, Seismic, Marcellus Shale, Geologic Structure
Date Deposited: 20 Sep 2016 15:03
Last Modified: 20 Sep 2021 05:15


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