ABSTRACT

Granitic terranes of the now almost wholly buried Coahuila and Tamaulipas Peninsulas furnished the detritus which composes rocks of the Patula Arkose and of other nearly equivalent strata (that is, San Marcos Arkose) exposed in various breached anticlines of the Coahuila Marginal Folded Province of northeastern Mexico. Tilt-corrected cross-stratification measurements at twenty outcrop localities within the Patula Arkose at the La Muralla Crossing of Sierra de la Gavia, Coahuila, Mexico, have yielded data suggesting a major source area to the northwest (Potrero de la Mula area). A secondary source existed westward east of the Las DeliciasAcatita area. A tertiary site of origin, which may be an as yet undefined acid terrane emplaced in rocks of the buried Tamaulipas Peninsula, or altern tely, reworked arkosic detritus from this direction, existed northeastward. Minor loci of acidic nature contributed arkosic debris from the southeast. A histogram of total cross-bed inclinations (160) offers strong support in favor of a fluvial origin for the unit. The high standard deviation and polymodality compare favorably with other inclination histograms of fluvially deposited sedimentaries which have been documented in the literature.