Date of Award
Open Access Dissertation
James N. Kellogg
The southeastern North American margin (SENAM) is one of the world’s oldest intact passive margins, containing the ancient southern Appalachian Mountains, the South Georgia Rift (SGR), and the Central Atlantic Magmatic Province (CAMP).
Potential field data is used in combination with seismic imaging, borehole data, and surface geology to better constrain the lithospheric configuration created by Appalachian orogenesis and Atlantic rifting. In combination with filtering techniques, maps and 2D potential field forward models, and Euler inverse modeling are used to illuminate the pre-Cretaceous basement including basement faults, shear zones, and granites in the hinterland of the southern Appalachians, and rift basins and mafic intrusions beneath the Atlantic coastal plain and continental shelf.
Focusing on the Laurentia – peri-Gondwana suture zone, modeling confirms the importance of low-angle basement thrust faults in producing Alleghanian uplift and exhumation of metamorphic core complexes. The Appalachian paired gravity anomaly is explained by an increase in crustal thickness and a decrease in upper crustal density northwest of the Carolina superterrane, suggesting that Grenville-age basement rocks extend southeastward beneath the coastal plain.
The source of the enigmatic and controversial Brunswick Magnetic Anomaly (BMA) is interpreted to be a series of late-stage rift-related mafic intrusions segmented by incipient fracture zones. This interpretation is supported by the observation that the BMA is independent and inboard of the East Coast Magnetic Anomaly, implying a pre-drift source, and that the amplitude and frequency of the anomaly change nearshore across the Blake Spur fracture zone that divides the offshore BMA, where continental breakup occurred, from the onshore BMA.
Basin boundaries of the SGR were revised using tilt derivative maps of gravity and filtered magnetic data. These maps delineate the northern boundaries of the SGR in South Carolina, and suggest the existence of a class of lenticular basins peripheral to the SGR developed within the Piedmont (Carolina) magnetic terrane. A major crustal boundary between the Piedmont and Charleston-Brunswick magnetic terranes in eastern Georgia and South Carolina is proposed as the Suwannee (Alleghanian) suture. The Tifton and McClellan magnetic anomalies are interpreted to be mega-scale mafic igneous complexes, which are evidence of focused rift-related magmatism.
Duff, P. D.(2020). The Evolution of the Southeastern North American Margin From Integrated Analyses of Potential Field Data: Continent-Continent Collision and Rifting. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/5698