Low-angle extensional faulting, reactivated mylonites, and seismic reflection geometry of the Newark basin margin in eastern Pennsylvania
Low-angle 25/sup 0/ to 35/sup 0/ dips have been determined for the border fault of the Newark basin near Riegelsville, Pennsylvania, on the basis of 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 coincides with the updip projection of imbricate fault slices and mylonites associated with the Musconetcong thrust system of Drake et al. (1967). Contrasts in acoustic impedance among mylonitic dolostone and mylonitic gneiss and their protoliths, determined from measurements on samples from a third cored hole, 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 northwest-southeast quadrant was approximately perpendicular to the strike of the ancient thrust faults in eastern Pennsylvania. The data presented here are the most explicit three-dimensional information obtained thus far in the eastern US in support of the concept of fault reactivation in controlling formation of early Mesozoic extensional basins.
- Research Organization:
- Geological Survey, Reston, VA
- OSTI ID:
- 5717848
- Journal Information:
- Geology; (United States), Vol. 14:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
SEISMIC SURVEYS
TECTONICS
PENNSYLVANIA
BASEMENT ROCK
BOREHOLES
CARBONATE ROCKS
DATA ANALYSIS
DRILL CORES
GEOLOGIC HISTORY
GEOMETRY
GNEISSES
MESOZOIC ERA
PALEOZOIC ERA
CAVITIES
FEDERAL REGION III
GEOLOGIC AGES
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
MATHEMATICS
METAMORPHIC ROCKS
NORTH AMERICA
ROCKS
SEDIMENTARY ROCKS
SURVEYS
USA
580201* - Geophysics- Seismology & Tectonics- (1980-1989)