New evidence for geologically instantaneous emplacement of earliest Jurassic Central Atlantic magmatic province basalts on the North American margin

Dikes in the southeastern United States represent a major component of the Central Atlantic STUDIES magmatic province and record kinematics of Pangean breakup near the critical, predrift junction of three major continental ma sses. Until now, the age of these dikes had not been determined with the sa me precision as those of Central Atlantic magmatic province basalts on othe r parts of the circum-Atlantic margin. Our new results for three dike sampl es from the South Carolina Piedmont yield plateau ages of 198.8 +/- 2.2, 19 9.5 +/- 1.8, and 199.7 +/- 1.5 Ma. For comparison, we present new age deter minations of the benchmark Watchung flows I and III of the Newark basin: 20 1.0 +/- 2.1 and 198.8 +/- 2.0 Ma, respectively. Collectively, these data su ggest that basaltic volcanism responsible for the dikes, flows, and sills o f eastern North America occurred within similar to 1 m.y. of 200 Ma. The ti ming, brief duration, and extent of the Central Atlantic magmatism imply th at it may have been causally related to Triassic-Jurassic mass extinctions. The distribution and timing of this magmatism and the absence of regional uplift or an identifiable hotspot track lead us to favor strong lithospheri c control on the origin of the Central Atlantic magmatic province, consiste nt with the modern generation of plume incubation or edge-driven convection models.