Author: Matthew Ryan Harding

Publisher:

Published: 2017

Total Pages: 0

ISBN-13:

The Upper Silurian Salina Group in Pennsylvania's Appalachian basin consists of 2,000+ feet of salt, which have been a significant influence on the tectonic & structural development of the Appalachian Mountains during the late Paleozoic. Understanding how halokinesis and decollement thrusting within the Salina Group has contributed to the present-day structure of the Appalachian Basin is of great importance due the organic-rich shale plays (Marcellus and Utica) currently being explored and developed within this region. Given that most of the seismic data collected from this region was before the advent of high-resolution 3D seismic surveys, a more detailed investigation of structures associated with the Salina Group was warranted.Based on preliminary examination of seismic data from North-Central Pennsylvania, I propose that the reactivation of basement faults during the Allegheny orogeny influenced halokinesis in the overlying Salina, and therefore acted as a control on the development of the salt cored anticlines and associated faulting in the overlying units. This was tested by detailed mapping of structures in the basement and in the Paleozoic sequence above and below the Salina, noting any spatial associations between the structures. Isochronopach maps and profiles were created and analyzed, to constrain the deformation of the Salina Group. Several faults were found within three primary stratigraphic sections of the seismic volume. Those are the above Salina Group (AB1 and AB2), Salina Group (S1, S2, and S3), and basement (B1, B2, B3, B4, B5, and B6). Along with T1, sub-divided into three stratigraphic sections; faulting ~50ms TWTT above top of basement; monoclinal folding and faulting within the Trenton-Black River Group; and faulting between ~1.5-1.8s TWTT. Further a pop-down structure is formed by salt evacuation between S1 and S2 is found from Inline 300 to Inline 90, being most developed at Inline 95 and 90. Structures found within the 3D volume suggests indirect basement control on Salina development. Along with the development of the pop-down structure of the S1/S2 complex further offer evidence of basement influence. Results appear to strengthen the model put forward by Mount (2014) however result maybe only applicable this specific region. The main conclusion of the study are as follows; there is a spatial correlation between the location and development of faulting within and above the Salina Group and a structural high formed by Neoproterozoic basement faults. With the intersection of B1 and B6 associated with the SW ends of S1 and S2, where above the S1 and S2 propagate highest upwards, and where AB2 initiates above where S1 offsets Tully Limestone above this B1/B6 intersection. This suggests that the location of Salina Group faulting is the resultant influence of Grenville basement topography caused by Neoproterozoic rifting. There is also evidence of diffuse deformation below Salina decollement in the same location T1, whose features are most common below the S1/S2 pop-down and above the B1/B6 intersection. Where the changes in overburden thickness due to basement structures acted as foci for later Salina deformation during the Alleghanian orogeny.