Abstract

The margins of the Pedregosa basin can be defined in outcrops of Pennsylvanian and Permian strata in southwestern New Mexico and southeastern Arizona. Siliciclastic basinal rocks crop out along the eastern flank of the Sierra del Cuervo, near Villa Aldama, Chihuahua, Mexico. The late Paleozoic rocks exposed near Villa Aldama have experienced four phases of deformation. Two sedimentary assemblages are recognized within the deformed late Paleozoic section. The upper sedimentary assemblage is a thin-bedded turbidite sequence. Sandstones near the stratigraphic top of the upper assemblage contain Wolfcampian fusulinids. The sandstones and siltstones in the late Paleozoic sequence are quartz-rich rocks with sub-equal amounts of feldspar and lithic fragments. The sediments are of continental block provenance, recycled from quartz-rich, shallow-marine sandstones exposed above rising basement blocks. Granitic debris denoting unroofing of Precambrian granites on the rising basement blocks is found only in a sandstone near the stratigraphic top of the late Paleozic sequence. The rocks exposed near Villa Aldama indicate the existence of a Pennsylvanian-Permian deep-water basin. The mineralogy of the basin-fill sandstones corroborates previous interpretations of the geology of the margins and adjoining shelf and source areas of the Pedregosa Basin.

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