39 Rates and Processes of Appalachian Erosion

Wednesday, 22 March 2006
8:00 AM - 12:00 PM

EARLY JOINTING IN COAL AND BLACK SHALE: EVIDENCE FOR AN APPALACHIAN-WIDE STRESS FIELD AS A PRELUDE TO THE ALLEGHANIAN OROGENY

Paper number: 39-4
Program: THEME SESSIONS
Time: 8:45 AM – 9:05 AM

Authors

Abstract

Early ENE striking joints (present coordinates) within both Pennsylvanian coal and Devonian black shale of the Central and Southern Appalachians define an approximately rectilinear stress field with a dimension > 1500 km. This Appalachian-wide stress field (AWSF) dates from the time of joint propagation when both the coal and shale were buried to the oil window during the 10-15 My period straddling the Pennsylvanian-Permian boundary. The AWSF was generated during the final assembly of Pangea as a consequence of plate-boundary tractions from either (1) late-stage convergence where maximum horizontal stress, SH, was parallel to the slip vector of Gondwana relative to Laurentia or (2) dextral slip of Gondwana relative to Laurentia where SH is ≈ 30° from the plate-bounding transcurrent fault. An overprint of Alleghanian joints marks the disruption of the AWSF by local stress fields associated with stratigraphically controlled décollement tectonics of the conventional Alleghanian orogeny.