Circular 35 — Geology of Capitan Coal Field, Lincoln County, New Mexico

By Marc W. Bodine, Jr., 1956, 27 pages.

The Capitan coal field, situated west of Capitan, Lincoln County, New Mexico, on the east flank of the Sierra Blanca syncline, contains coal within the Mesaverde group of Upper Cretaceous age. The intertonguing Mancos shale and Mesaverde group include three mappable units of the Mesaverde and are correlated tentatively with the Upper Cretaceous of northwestern New Mexico. Above the Mesaverde lie Cub Mountain terrestrial sediments believed to be of Tertiary or Upper Cretaceous age, possibly correlative with the Galisteo and Baca formations to the north and west or with the McRae formation to the southwest. Igneous dikes, sills, and flows are later than the sediments. The igneous activity is post-Cub Mountain and prefaulting. Three large normal faults, which trend northeast, and numerous small faults were found, but most of them could not be traced, because of a cover of later sediments. Mining at Capitan, once very active, has ceased, in part because of faulting, and in part by reason of the presence of many dikes, which increased mining costs beyond economic limits. One coal seam of minable quality and thickness has been mapped. It is improbable that the mines could be reopened and operated profitably under present conditions.