Geology of the Bear Peak area, Dona Ana County, New Mexico

The Bear Peak area, in south-central New Mexico at the south end of the San Andres Mountains, includes structural elements of both the westward-dipping San Andres Mountains and the Organ Mountain igneous mass.Rocks exposed in the area range in age from Precambrian to Recent.The Precambrian rocks include schist, quartzite, granite, and associated rocks.Paleozoic rocks, which make up much of the mountain mass, include the Bliss Sandstone of Late Cambrian and Early Ordovician age, the El Paso Formation of Early Ordovician age, the Montoya Dolomite of Middle and Late Ordovician age, the Fusselman Dolomite of Middle Silurian age, and undivided Devonian and Mississippian rocks.The Pennsylvanian System is represented by the Lead Camp Limestone (a new name) and the Panther Seep Formation.The Lower Permian (Wolfcamp) Abo and Hueco Formations interfinger within the area, and the Lower Permian (Leonard) Yeso Formation is present in outliers.Undivided rocks of Cretaceous age are present in a few exposures.Rocks of Tertiary age are the Love Ranch Formation, which is chiefly conglomerate derived from local sources, and igneous sills and dikes.The sills and dikes are genetically related to the Organ Mountain igneous mass to the south.Alluvium and dune sand of Quaternary age are present along the edge of the mountain uplift.Normal faults are the most conspicuous structural features in the area, but a major system of reverse faults is present in the southern part of the San Andres Mountains.Movement along this fault system was toward the north, and the reverse faults mark the structural boundary between the San Andres Mountains and the Organ Mountains.Cl C2

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• "Red Beds" and associated formations in New Mexico, with an outline of the geology of the state

  Nelson Horatio Darton•1928

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