THE PENNSYLVANIA SALIENT: SEISMIC AND OTHER EVIDENCE FOR AN IAPETAN ARCUATE RIFT INFLUENCE ON THE ARCUATE MAP PATTERN

Integration of 11 types of data, including reprocessed proprietary seismic data from the Appalachian Plateau of NYS and northern PA, indicate that the arcuate structural map pattern characteristic of the Alleghanian Pennsylvania Salient was strongly influenced by an arcuate system of Iapetan opening/Rome Trough faults.

In the Appalachian Plateau of NYS, shallow structural-level features were assumed to reflect Alleghanian salt-cored folds and associated thrusts related to the arcuate map pattern of the fold and thrust belt in Pennsylvania. Data sets included primarily shallow well logs and dips of surface rocks measured by leveling lines, some salt mine data and extremely limited seismic reflection data. However, in NYS these arcuate fault systems are coincident with some aeromagnetic anomalies, suggesting basement involvement. Further, seismic data across NE-trending lineaments in NYS show that several lineaments, formerly believed to represent shallow folds, actually represent fault systems that affect the entire Paleozoic section. Some of these faults were initially Iapetan-opening growth faults. Similarly, in northern PA, the Alleghanian Smethport-Sharon Anticline is coincident with an arcuate aeromagnetic anomaly, and reprocessed seismic shows a dramatic hinge in Iapetan opening time beneath the anticline.

These and other examples suggest that the Iapetan opening faults in this “corner” zone have an original arcuate map pattern. The arcuate faulting was interrupted by northerly-trending Iapetan-rift faults that are reactivated intra-Grenvillian suture faults. The intersecting pattern of northerly and arcuate fault trends may have an analog in the present eastern North Atlantic corner zones west of the UK where northerly-trending micro-continents such as Porcupine, Rockall, and Bill Bailey banks lie north (and east) of the present deep Atlantic that sweeps around the banks and their intervening deeps.

The Iapetan arcuate faults (and intersecting faults) controlled (through weakened, fractured rock from fault reactivations) the locations of later Alleghanian faults (including ramps). Little tightening of the arc occurred through time (consistent with paleomagnetics. The numerous reactivations of the fault systems controlled deposition in the shallow Appalachian Basin.