1. Map showing paleogeography of the continental shelf during the low stand of sea level, Wisconsin glacial epoch, Port Isabel 1° x 2° quadrangle, Texas [cartographic material] Yale Public content 1980. 2015-06-23T18:56:32Z. 2015-07-07T22:09:35Z. Berryhill, Henry L., Jr. (Henry Lee), 1921-2013. U.S. Geological Survey. English. cartographic image. Public. Texas, Padre Island, and Port Isabel.