A REINTERPRETATION OF THE 1969 HALES ONSHORE-OFFSHORE SEISMIC PROFILE IN THE NORTHERN GULF OF MEXICO

We present here a re-interpretation of seismic refraction data from the Northern Gulf of Mexico and the Gulf coast Plain collected by Hales (1970; reinterpreted Gurrola, 1985). The data set is a 700 km long, north-south trending line from along the Texas Louisiana border, from the center of the Sabine Uplift to the Sigsbee Escarpment. All the shots were offshore and included 21 one ton shots (recorded to 550 km offsets) and about a hundred small 100 to 150 pound explosions (recorded to offsets of 90 km). Our current model found the basement to be only about 3 km deep above the Sabine Uplift. The basin is deepest from the shore line to about 100 km offshore where there is as much at 13 km of low velocity clastic Gulf Coast sediment. The crust appears to be 42 km thick beneath the Sabine uplift. The continental crust appears to thin to less than 5 km beneath the deepest par tof the sedimentary basin (from the coast to 100 km offshore). In fact the velocity of this very thin crust may be only 5.8 km/s which may be more consistent with crystalline sedimentary rock (such as limestone or volcaniclastics). This region may in fact have no continental crust but may instead be underlined by oceanic crust or serpentinized exhumed mantle. There appears to be a thick "rift Pillow" or serpentinized mantle beneath the crust in this area. The crust toward the Sigsbee Escarpment does appear to thicken and include continental crust. As a result there appears to be an along coast line rift that is opened a small ocean basin but then failed with the southern terminus of Laurentia at the Sigsbee Escarpment