Early Jurassic-age basalts preserved in deeply eroded basins in Eastern North America have recently been proposed to be remnants of vast flood basalt province. This hypothesis, based on the wide geographic extent of feeder dikes, suggests that the basalt extended far beyond the present boundaries of the basin. If this were the case, we would expect to see a strong basaltic signature in the sedimentary rock within the basin. However, analysis of Nd and Sm/Nd isotope ratios of red shale from the Hartford Basin are between the basalts and show that the shales have a uniformly continental-not basaltic-signature, even from shales samples directly above (<1m) from the basalt. This lack of evidence for a basalt contribution to the sedimentary record indicates that the basalt flows were much smaller than previously thought.
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Last updated: 8 January 2001, KAK.