Date of Award

2017

Document Type

Open Access Dissertation

Department

Earth and Ocean Sciences

Sub-Department

College of Arts and Sciences

First Advisor

James H. Knapp

Abstract

A series of exotic terranes with complex tectonostratigraphic relationships construct the North American margin and record information critical to understanding the evolution of the Appalachian orogen. The Coastal Plain cover remains a challenge in this region; however, synthesis of seismic reflection, seismic refraction, well, and aeromagnetic data allows for a substantially revised interpretation of the basement rocks and structures that comprise the pre-Mesozoic crust of southeastern North America. These data reveal: (1) a Neoproterozoic subduction zone and paired continental-margin arc are preserved in Gondwanan crust in southeastern North America, (2) the Gondwanan Suwannee Basin of Early to Mid-Paleozoic age is much more extensive than previously thought, and (3) one of the largest faults in eastern North America, termed the Pangean Transcurrent Fault System (PTFS), transects the Alleghanian suture and crosscuts tectonic boundaries internal to Laurentian and Gondwanan crust. The revised extent of the Suwannee Basin strata provides critical new age constraints on the long-debated age and tectonic origin of the dipping reflectivity associated with the Brunswick Magnetic Anomaly (BMA). Previously thought to be the Alleghanian suture, this tectonic boundary is now documented to represent a Neoproterozoic suture zone, termed the Brunswick Suture Zone (BSZ). The geometry and location of the BSZ can be correlated with Neoproterozoic volcanic and intrusive rocks identified as the Osceola Arc. Lithological, geochemical, and geochronologic evidence suggest these igneous rocks formed in a

continental margin arc along the former Gondwanan margin, and are now preserved along with their inferred subduction zone (BSZ) in the subsurface of southeastern North America. Integration of known geological constraints with aeromagnetic and seismic reflection data suggest that the BSZ, the Alleghanian suture, and other tectonic boundaries internal to the Appalachian orogen are all truncated by a regionally extensive, dextral, transcurrent fault system identified as the PTFS. This crust-scale boundary likely transects the former plate boundary between Gondwana and Laurentia and therefore, cannot represent the Alleghanian suture as previously interpreted.

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