Previous hypotheses proposing that the Triassic of Connecticut and New Jersey were deposited in a single, connected basin assumed that (1) three lava flows occurred at the same stratigraphic position in each basin, (2) an anticlinal link was subsequently eroded (except for the Pomperaug Outlier), and (3) the Triassic lithofacies distribution in each basin represented a “half-graben” remnant of a larger fault trough.
Recent work on Triassic lava flow stratigraphy in Connecticut has revealed local complications in field mapping that makes regional correlation difficult. Measurements of the inclination of thermal remanent magnetization (TRM) of lava flows has shown that three distinct magnetic events occurred in Connecticut, but only one in New Jersey. Previous correlation of the three lava flows is not tenable, therefore. Potassium-argon measurements of Triassic sedimentary rocks and source rocks indicate that the New Jersey Triassic basin was an isolated basin, as previously documented from paleocurrent and mineralogical studies. Preliminary paleocurrent data indicate that the Connecticut Valley was an isolated basin too. Comparison to paleocurrent analyses of other Triassic basins of eastern North America confirms that each was a separate basin at the time of deposition.
New data on Recent sediments in a modern graben show that the so-called “half-graben” distribution of sedimentary facies can occur in a simple graben where structural and physiographic boundaries do not coincide. Thus, facies analysis must be used with care when reconstructing the size of fossil fault trough basins such as the Triassic of eastern North America.