Seismic reflection geometry of the Newark basin margin in Eastern Pennsylvania. Evidence for extensional reactivation of Paleozoic thrust faults
Low-angle 25/sup 0/ to 35/sup 0/ dips have been determined for the border fault of the Newark basin near Riegelsville, Pennsylvania, based on a VIBROSEIS profile and two continuously-cored drill holes across faults at the basin margin. A group of moderately strong planar reflections in a zone 0.5 km thick in gneiss and carbonate rocks of the footwall block coincide with the updip projection of imbricate fault slices and mylonites associated with the Musconetcong thrust system of Drake and others (1967). Contrasts in acoustic impedance among mylonitic dolostone and mylonitic gneiss and their protoliths, determined from measurements on core samples, are sufficiently large to account for reflections seen in the footwall block. Analysis of drill core and surface outcrops supports the conclusion that low-angle extensional faulting in the Early Mesozoic was localized by reactivation of Paleozoic imbricate thrust faults in the basement rocks. Extension in the NW-SE quadrant was approximately perpendicular to the strike of the ancient thrust faults in Eastern Pennsylvania and a passive origin of the Newark basin here is suggested. The data presented here represent some of the most explicit three-dimensional information obtained thus far, in the Eastern United States, in support of the concept of fault reactivation in controlling formation of Early Mesozoic extensional basins.
- Research Organization:
- Geological Survey, Reston, VA (USA)
- OSTI ID:
- 5649340
- Report Number(s):
- NUREG/CR-4676; ON: TI86901567
- Country of Publication:
- United States
- Language:
- English
Similar Records
Mesozoic contractile and extensional structures in the Boyer Gap area, northern Dome Rock Mountains, Arizona
The Chunky Gal Mountain fault-detachment-normal fault providing evidence for Early-to-Middle Paleozoic extensional unroofing of the eastern Blue Ridge, or folded thrust