OF-11-04 Geologic Map of the Jones Hill Quadrangle, Park County, Colorado


The purpose of the Jones Hill quadrangle map is to describe the geologic setting, mineral and water resources, and geologic hazards of this 7.5-minute quadrangle located south of Fairplay in central Colorado. Staff geologist Beth Widmann, consulting geologists Bob Kirkham and Karen Houck, and field assistant Neil Lindsay, completed the field work on this project during the summer of 2006. The bedrock unit descriptions, structural geology, and mineral and water resource sections of this report were written by Ms. Widmann. Mr. Kirkham completed the sections on surficial deposits and geologic hazards. Ms. Houck contributed to unit descriptions and mapping of the Pennsylvanian-Permian rocks and handled the final stages of review and publication. Digital ZIP/PDF download. OF-11-04D

From the Author’s Notes:

The Jones Hill 7.5-minute quadrangle is located on the western margin of the South Park Basin in central Colorado. Jones Hill, at the center of the quadrangle, is about 11 miles south-southwest of Fairplay and about 16 miles north-northeast of Buena Vista. U.S. Highway 285 is just east of the quadrangle boundary. The South Fork of the South Platte River is the main drainage in the quadrangle. Several tributary streams, including Twelve mile Creek, Cave Creek, and Rough and Tumbling Creek flow into the South Fork in the northern half of the quadrangle. Topography is varied throughout the quadrangle with elevations ranging from just under 9,300 ft along stream valley floors to 12,644 ft atop the high mesa in the southwest quarter of the quadrangle. About two-thirds of the Jones Hill quadrangle lies within the Pike National Forest, which is administered by the U.S. Forest Service. The Buffalo Peaks Wilderness Area, established in 1980, extends into the southwest quarter of the quadrangle. Properties in the northeast quarter of the quadrangle are privately held ranches, fishing clubs, and residences or are leased sections belonging to the Bureau of Land Management and Colorado State Land Board.

The oldest rocks exposed in the Jones Hill quadrangle are Precambrian in age and consist primarily of biotite gneiss, migmatite, and granite. These rocks crop out along the western margin of the quadrangle. Generally east-dipping lower Paleozoic rocks overlie the Precambrian rocks and include, from oldest to youngest, the Cambrian Sawatch Quartzite and Dotsero Formation, the Cambrian-Ordovician Manitou Formation, the Devonian Parting Formation and Dyer Dolomite (both part of the Chaffee Group), and the Mississippian Leadville Limestone. The eastern three-quarters of the quadrangle are underlain by Pennsylvanian to Permian Formations, which include the Belden Shale, the Minturn Formation, and the Maroon Formation.