At the end of the Triassic, ∼200 m.y. ago, the Central Atlantic Magmatic Province (CAMP), one of the largest igneous provinces in the world, was emplaced within a very short period of time. The flows, sills, and dikes that mark the event are predominantly preserved in Triassic rift basins along the Atlantic margins. Conventional wisdom implies that the areally largest of the CAMP flows is preserved in the South Georgia Rift, a Triassic rift basin buried beneath the Atlantic Coastal Plain. The extent of this flow has been mapped on the basis of a prominent seismic reflection referred to as the J horizon. This seismic horizon has been used as a time marker for estimating the end of rifting in the southern United States and the beginning of seafloor spreading. Reanalysis of existing well and seismic data, however, shows that the extent of the flood basalt is limited to a few areas, and that the J horizon coincides with the base of the Coastal Plain. This reopens the question of how the CAMP relates to the rift-drift transition of eastern North America.

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