This folded transparent map is at the same scale as its corresponding Geologic Atlas of Texas (GAT) sheet and can be superimposed on it to compare gravity information with surface geology.

The Big Wells (San Miguel) reservoir in Dimmit and Zavala Counties, South Texas, produces from a broadly lenticular, wave-dominated deltaic sandstone encased in prodelta and shelf mudstones. An updip porosity pinch-out coincides with a gentle undulation on a uniformly gulfward-dipping monocline and forms a structurally modified stratigraphic trap. The reservoir is relatively tight and has average porosity of 21 percent and average permeability of 6 md; wells require fracturing to stimulate production.

This folded transparent map is at the same scale as its corresponding Geologic Atlas of Texas (GAT) sheet and can be superimposed on it to compare gravity information with surface geology.

Changes in shoreline position occurring for more than a century provide estimates of the relative stability of shorelines and, along the Texas coast, allow comparisons of shoreline changes before and after human modifications became significant.