AN EXAMINATION OF DEFORMATIONAL STRUCTURES AS A REFLECTION OF CHANGING STRESSES FROM THE PALEOZOIC TO MESOZOIC IN EASTERN PA

Although the Newark Basin and Ramapo fault are well studied, few studies have examined the relationship between preexisting Paleozoic deformation and the subsequent Mesozoic deformation. The objective of this study is to understand the transfer of stresses across the Ramapo border fault from the Mesozoic into the Paleozoic formations. Throughout the Paleozoic, a series of orogenies occurred in eastern North America resulting in the formation of Pangaea. Mesozoic sediments were subsequently deposited in the rift basins that formed as Pangaea rifted during the Triassic. Thrust faults active during the compression in the Paleozoic were reactivated during the rift of Pangaea, forming the Ramapo border fault (Schlische, 1993; Schlische, 1992; Olsen, 1980).

The Ramapo border fault extends through the Newark Basin, from Pennsylvania to New York. Our study area in eastern Pennsylvania and western New Jersey stretches along and across this fault in a 10-by-20 mile area. Data of bedding, faults, and joint sets were collected using Brunton compasses and the GeoFieldBook iPad application. Stereonet 9 was then used to create stereoplots to compare the deformation on the Paleozoic (North) and the Mesozoic (South) formations.

Similar joint orientations across the border fault seem to suggest that Mesozoic stresses were transferred into the Paleozoic rocks. Preliminary work done by Emily Homan in early 2015 reveals that there was no transfer of stresses between the Paleozoic and Mesozoic. While our preliminary findings of joint sets indicate that there is a transfer of stresses, the data of the fault sets is not as clear. We are continuing to collect data while incorporating data from previous studies in an attempt to draw a rock solid conclusion about the transfer of stress across the fault.