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Post-Paleozoic Structural Styles in Northern Sierra de Palomas: Chihuahua, Mexico

David J. Sivils

Sierra de Palomas is the largest and most northerly range of the Boca Grande trend in northwestern Chihuahua, Mexico. Sierra de Palomas is composed of more than 1.5 km of late Paleozoic shelf carbonates and clastics. Detailed mapping of the northern 150 km2 of the range (at a scale of 1:12,500) has shown that four post-Paleozoic tectonic events have affected the range.

The Laramide orogeny, two separate periods of basin and range extension, and recent (Rio Grande rift?) extension have left very distinct structures in the range. Laramide structures are predominantly vergent to the northeast, and are manifested as folds and thrusts. Folds are asymmetric and northwest trending, with amplitudes on the order of 10-50 m. Major thrusts in the range have minimum displacements on the order of a few kilometers. Basin and range structures include two distinct sets of high-angle faults; an "early" northeast-trending set is truncated by a "late" northwest-trending set. Recent Rio Grande rift(?) extension in the area is evident in fault scarps that offset alluvial fan deposits and in steeply eastward-tilted alluvial deposits.

AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.