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This GIS dataset is reproduced from: “Best, M.G., Hintze, L.F., and Holmes, R.D., 1987, Geologic map of the southern Mountain Home and northern Indian Peak Ranges (central Needle Range), Beaver County, Utah: U.S Geological Survey Miscellaneous Investigations Series Map I-1796, 1 plate, scale 1:50,000.” The map covers four standard 7.5' quadrangles in southwestern Utah: Lopers Spring, Sawtooth Peak, Miners Cabin Wash, and Buckhorn Spring. The GIS dataset was completed by Anthony Blackham and Gerrit Gardner, students at Brigham Young University, and final GIS review and preparation for public release were completed by Zach Anderson, a geologist with the Utah Geological Survey.The UGS appreciates the volunteered time and effort of Brigham Young University students Anthony Blackham and Gerrit Gardner who produced the GIS data for this project under the guidance of Brigham Young University professor Eric Christiansen.The map area is in the Basin and Range Province of southwestern Utah and is dominated by north-south-trending mountain ranges and broad valleys. The southern part of the Mountain Home and northern part of the Indian Peak Range expose a nearly complete section of Middle Cambrian through Lower Mississippian sedimentary rocks that generally dip east. Uppermost Ordovician and Silurian rocks in the north part of the map are cut by numerous attenuation faults that are subparallel to bedding and are thought to be the result of thin-skinned detachment faulting that occurred during relaxation of the thrust belt sometime after the Late Cretaceous Sevier orogeny. Late Eocene to late Oligocene volcanic and volcaniclastic rocks unconformably overlie Paleozoic rocks. Portions of the Pine Valley and Indian Peak calderas, the sources of multiple volcanic units in the map area, are present within the central and southern portion of the map. North- to northeast-striking normal faults are a result of the Tertiary Basin and Range extension. The west side of the Indian Peak Range is cut by a major down-to-the-west normal fault that bounds the west side of the range and the east side of Hamlin Valley. A sediment-veneered pediment extending a few kilometers into Pine Valley is present on the east side of the ranges.This dataset was produced as part of a UGS multi-decade effort to provide statewide intermediate-scale (approximately 1:50,000 to 1:100,000) GIS data to the public, federal to local government agencies, educational groups, exploration and development companies, and other map users. The GIS dataset reproduces the original source map as close as reasonably possible; however, some geologic decisions were made to resolve cartographic problems such as inconsistent faults and incomplete polygons. We changed some geologic line symbols to better match the UGS 2018 data model. While the map is considered a good representation of the geology of the map area, users should be aware that it was produced in 1987 and does not meet all modern cartographic, spatial control, or geologic standards. Line and point attributes and symbology were selected from current (2018) UGS schema and do not necessarily match the intent of the original map. Selected attributes most closely represent the general geologic interpretation depicted on the original map, but are not an exact match, as noted below. ContactsOriginal attribute is “Contact – Dashed where approximately located or inferred on cross sections.” These lines are now depicted as “Contact, well located.”Normal FaultsOriginal attribute is “High-angle fault – Dotted where concealed. Bar and ball on downthrown side.” These lines are now depicted as “Fault, normal, well located” or “Fault, normal, concealed.”General faultsLine types do not have a description in the explanation of the original map. These lines are now depicted as “Fault, unknown, well located” or “Fault, unknown, concealed.”Attenuation FaultsOriginal attribute is “Younger-on-older attenuation fault.” These lines are now depicted as “Fault, attenuation, exposed” where younger rocks are faulted over older rocks.FoliationOriginal attribute is “Strike and dip of compaction foliation in tuff and flow layering in intrusive bodies.” These points are now depicted as “Foliation, inclined, field measured” or “Foliation, horizontal.”Hydrothermal AlterationThe original source map shows areas of hydrothermal alteration denoted by a black stipple pattern on top of the host rock fill color. These areas are now denoted with a separate polygon that is attributed with a unit symbol of “ha” and unit name of “Hydrothermal alteration.” These hydrothermal alteration polygons overlie the host rock polygon, have a transparent background and a black stipple pattern, and are a unique feature class.Units – Descriptions/Names/AgesMap is not modified from original source map even in locations where newer interpretations may exist. |