4000 Feet of shortening with the Kennedy coal bed duplex at McClure, Cumberland overthrust block, SW VA

Conference · Tue Mar 01 00:00:00 EST 1994 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6845723

Morgan, S; Henika, W S ^[1]

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1. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States) Dept. of Geological Sciences

Area balancing of a coal bed duplex developed within the lower Pennsylvanian Norton Fm reveals an approximate shortening of 4,000 feet along an upper level detachment within the Pine Mtn thrust system at McClure, VA. The Kennedy coal bed was examined along a railway cut for nearly 500 feet where an original thickness of 0.6 feet of coal is increased to over 7 feet. The thickened section is characterized by chaotic folding, but local segments exhibit well developed piggyback thrusting. The coal bed duplex mimics larger scale duplex structures, although extensional structures are also observed and seem to relate to the rigidity of the overlying thrust sheet. For most of the 490 foot outcrop measured, an upper and a lower level of piggyback stacking delineates a floor, roof and mid-level thrust system. The mid-level thrust is often folded and faulted, indicating episodic movement on all the faults. Thickness of the repeated coal bed increases gradually northward along the cut, but locally the upper level of thrust slices are missing. These voids are filled by gouge and indicate that once the roof thrust has attained a certain height, that level is maintained and attests to the rigidity of the overlying thrust sheet. Coalbed duplexes may have a profound effect on resource thickness and contribute to roof control problems in SW VA mines. They are also important because such intense shortening has previously been unrecognized at this level of the Pine Mtn thrust system and should be accounted for in reconstructing cross sections and calculating regional shortening.

• OSTI ID: 6845723
• Report Number(s): CONF-9404221-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 26:4; Conference: 43. annual meeting of the Southeastern Section of the Geological Society of America, Blacksburg, VA (United States), 7-8 Apr 1994; ISSN 0016-7592
• Country of Publication: United States
• Language: English

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