THE SOUTH GEORGIA RIFT BASIN, MAGMATISM, AND THE BREAK-UP OF PANGAEA

I use elastic finite element models in an attempt to determine the possible affect the South Georgia Rift (SGR) basin and the timing of the magmatic events along the Southeast coast of North America had on the evolution of the break-up of Pangaea around 200 Ma. The ENE-WSW trending SGR stretches from offshore the Florida panhandle in the Gulf of Mexico across Georgia to the coast of South Carolina. Its formation and the formation of the massive basalt extrusions are dated to around the time of the magmatic event and rifting of Pangaea along the Eastern North American Margin (ENAM), however, the exact relationship is not well understood. Along the southeastern ENAM, NW trending dikes and NE trending extensional basins dominate, making the relationship and timing all the more complicated. I used finite element models to test the timing and viability of the formation of the SGR and the NE trending ENAM basins with regard to both changes in large plate motions (South America, North America, and Africa) and with regard to segmentation and changes in continental strength modified by faulting and magmatism. The models were constrained by the need to meet known parameters including; the age of the NE trending extensional basins along the ENAM margin, the age and orientation of the mafic dike swarms along the ENAM margin, approximate ages for the SGR magmatics and rifting, and the known physical properties of the region. Initial results indicate that the enigmatic NW trending dikes of South Carolina and Georgia can be created if both South America and North America pull away from Africa and South America is still exerting stress on North America at the time. However, the effect of the generally southward motion of South America must have been different when the ENE trending SGR was formed and when the NE trending ENAM basins were formed. The complicated results of the models suggest that while plate motions were changing during this time period (230-190 Ma), the apparent rapid changes in stress fields were more likely modified by the formation of zones of weaknesses (the SGR) and strength which mitigated the effects of the plate motions. The magmatism and the formation of the SGR and a subsequent offshore rift in the Gulf of Mexico likely protected ENAM from the full effect of the separation of South America from North America.