The purpose of the Open File Report OF-12-09 is to describe the geology, mineral and ground‐water resource potential, and geologic hazards of this 7.5‐minute quadrangle located northeast of Leadville in central Colorado. Consulting geologists James P. McCalpin and Jay Temple, and field assistants Karri Sicard, David Mendel, and Bashir Ahmad completed the field work on this project during the summer of 2007. Dr. McCalpin and Mr. Temple, the principal mappers and authors, created this report using field maps, photographs, structural measurements, and field notes generated by all five investigators. Digital ZIP/PDF/GIS download. OF-12-09D
From the Introduction:
The Climax quadrangle is dominated by the Mosquito Range, a component range of the Southern Rocky Mountains composed mainly of Precambrian crystalline rocks. This range probably existed as a topographic high during the Laramide orogeny (late Cretaceous—early Tertiary), based on the presence of reverse faults of that age (London fault). However, the present topography of the range is the result of Neogene uplift along the west‐dipping Mosquito and Weston faults on the west side of the range, both normal faults related to the Rio Grande rift. Uplift of 9,000 ft along the Mosquito fault has juxtaposed the Precambrian rocks of the footwall against the Pennsylvanian Minturn Formation, which underlies most of the western half of the Climax quadrangle. Both the Precambrian and Permian rocks are laced by early Tertiary dikes, sills, and stocks, the source of mineralization in the Leadville, Climax, and Alma‐Horseshoe mining districts. In the eastern half of the quadrangle (east of the Mosquito fault), most terrain is composed of the Precambrian core of the Mosquito Range. However, in small areas strata of Cambrian through Pennsylvanian age are preserved atop the Precambrian unconformity.