INVESTIGATION OF THE LATE PALEOZOIC COLLISION IN SOUTHERN GEORGIA BETWEEN GONDWANA AND LAURENTIA AND THE RESULTING DEFORMATIONAL RESPONSE OF THE UPPER MANTLE

The purpose of this study is to investigate the late Paleozoic structural collision zone between Gondwana and Laurentia to provide insight into the resulting modes of deformation in the upper mantle characterizing the end of the Alleghanian Orogeny. Most of the current work on this topic has been limited to identifying and characterizing the structural collision zone in the crust due to the difficulty of resolving fine-scale reflection “fabrics” below the crust. Recent investigations of the uppermost mantle have focused on tomographic inversions of body waves and surface waves to broadly delineate features in the lithosphere. Studies of shear wave splitting have also been used to identify broad regions characterized by anisotropy. However, it has been difficult to separate contributions from the crust, sub-crustal lithosphere, and asthenosphere.

This study utilizes recently developed seismological techniques to create finer-scale images of the upper mantle through the analysis of PKIKP reflections. The goals of this study are first to show that PKIKP reflections from teleseismic events can effectively be used to image upper mantle reflection “fabrics” and secondly to provide insight into the modes of deformation in the upper mantle resulting from the late Paleozoic collision.

The results show that PKIKP reflections from teleseismic events are a valid method of imaging reflection fabrics in the upper mantle and also show consistent results for multiple earthquakes. The ability to image reflection fabrics in the upper mantle as shown in this study provides a new technique that can be applied to finer scale investigations of upper mantle structure beneath other mountain ranges, which should contribute to our understanding of the effect of orogenic events on upper mantle deformation.