New Evidence for the Reactivation of Basement Faults in the Development of Alleghany Plateau Folds in the Central Appalachians

Abstract

Reactivation of Cambrian and older faults throughout the central Appalachians has been long recognized. However what has only recently been recognized and documented is the extent to which these faults have episodically moved throughout the Paleozoic. This recognition has evolved through the benefit of 3-D and better 2-D seismic coverage integrated with well logs studies. These reactivations resulted in thin- or thick-skinned tectonics, depending upon numerous factors including the presence/thickness of salt. Extensive examples of structures with inferred dip-slip and strike-slip motion are presented for faults that trend parallel to both the Iapetan and cross-strike discontinuity (CSD) fabrics. Structural inversion of the Rome Trough faults is very common, and is best observed where there is a minimal Salina salt cover, and where there is significant throw on the faults. Some notable examples are Paint Creek Uplift in eastern Kentucky, Warfield Anticline in southern West Virginia, and Arches fork, Wolf Summit and Chestnut Ridge anticlines in northern West Virginia. Timing on these inversion structures generally had been thought to be primarily Alleghanian; however, reversals in motion (both dip slip and strike slip) compared to original Rome Trough fault motions began as early as Taconic time. Although the throw on the Rome Trough faults diminishes to the north into Pennsylvania, many of the anticlines (e.g., Chestnut ridge, Fayette, Belle Vernon) associated with these faults also reactivated. In addition to reversal of dip slip movement, strike slip movement occurred on many of these faults, as evidenced by series of Riedal shear structures in the Paleozoic section overlying Iapetan faults in West Virginia and Pennsylvania. Right lateral motion is inferred for most of the orogen-parallel, reactivated Rome trough faults. In addition, generally left lateral reactivation of (CSDs) occurred throughout Pennsylvania in Taconic through Alleghanian times. Lastly, the reactivation of many of the Iapetan faults throughout western Pennsylvania beneath the cover of Salina salt during Acadian time caused the initiation of a gravity sliding episode which was later greatly amplified by Alleghanian tectonics.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015