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Crustal evolution in the Southeastern United States Constrained by Teleseismic Receiver Functions

Elias H. Parker, Jr.1, Robert B. Hawman1, Karen M. Fischer2, and Lara S. Wagner3
1University Of Georgia
2Brown University
3University Of North Carolina, Chapel Hill

The EarthScope SESAME flexible-array experiment is designed to study lithospheric evolution in response to Late Paleozoic continental collision and Mesozoic rifting in the southeastern United States. The array consists of 85 broadband seismometers deployed along three transects across the crystalline terranes of the southern Appalachians and sedimentary cover of the Atlantic Coastal Plain. A primary goal of the study is to determine the relationship between the crustal-scale Suwannee suture zone and development of the South Georgia rift basin buried beneath the Coastal Plain. We analyzed teleseismic receiver functions to determine variations in crustal thickness and average crustal Vp/Vs across the accreted terranes exposed north of the suture zone. H-k stacking results indicate that both crustal thickness and Vp/Vs increase towards the high elevations of the Blue Ridge, consistent with previous wide-angle and receiver function studies. Low Vp/Vs ratios (1.69-1.72) across the Carolina arc terrane and parts of the Inner Piedmont are indicative of a felsic average crustal composition. The low values are incompatible with models of arc collision involving under-thrusting of the Carolina arc beneath the continental margin. Instead, the results are consistent with Alleghanian thin-skinned tectonic models showing the sub-horizontal Appalachian detachment extending beneath the Carolina terrane and possibly the Coastal Plain. If this model is correct, then the South Georgia basin may have formed above a mid-crustal detachment partly inherited from Alleghanian collision. Future work using additional SESAME stations will address the role of simple shear extension during continental rifting and formation of the Atlantic passive margin.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013