Now after reviewing the data in 3D visualization, we believe that the Diablo Platform started forming much earlier, perhaps in Cambro-Ordovician period. Also the culmination of this upliftment took place during Permo-Penn period. Next figure shows the Bouguer anomaly of the Trans-Pecos, and the adjacent area in Mexico. The gravity data, along with other geological and geophysical information, have been used to subdivide the area into various provinces. 12-Marathon Thrust belt.
White rectangle is the area for gravity modeling.
Volcanic igneous intrusions and limited Precambrain rocks are shown in irregular white lines. Bolson are defined as unconsolidated and unsorted sediments. Marfa basin, with a thick volcanic cover, fails to show a distinct gravity low. Increasing gravity anomaly within the Marathon thrust belt is possibly due to increasing thickness of the denser geosynclinal facies rocks of the Marathon thrust to the southeast. Structural highs within the southwest Delaware Basin probably account for the gravity maxima in that area.