AbstractsEarth & Environmental Science

The Little Burro Mountains are a small fault-block mountain range in central Grant County, New Mexico. Rocks of the Precambrian Burro Mountains batholith are exposed along the southwest scarp of the mountains, and are overlain by Upper (?) Cretaceous Beartooth quartzite and Colorado shale. Faunal evidence indicates the Colorado to be of Turonian age. Above the Cretaceous strata is a thick sequence of Tertiary volcanic rocks. A blanket of Pleistocene and Recent poorly consolidated gravels and conglomerates covered the area, but has been partly removed as a result of uplift along the Mangas fault, which forms the steep scarp bounding the southwest side of the range. Strata dip northeast from the Mangas fault. Fissure veins containing gold, silver, manganese, lead, and copper traverse the granitic rocks of the batholith and, locally, the Tertiary volcanics. Many small mining operations have been carried out in the past.