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This GIS dataset is reproduced from Crittenden, M.D., Jr., 1988, Bedrock Geologic Map of the Promontory Mountains, Box Elder County, Utah: U.S. Geological Survey Open-File Report 88-646, 1 plate, scale 1:100,000. The map is compiled for use at 1:100,000 scale. The map depicts geologic formations, faults, bedding attitudes, folds, and other information, and is accompanied by explanatory information including correlation of map units, description of map units, structure discussion, references, symbols, and a generalized cross section.The Promontory Mountains are in the eastern Basin and Range physiographic province of north-central Utah, dominated by north-south-trending mountain ranges and broad valleys. The Promontory Mountains exhibit about 8 kilometers thickness of the upper plate of the Willard thrust, in which three major structural units are grouped by their age and internal structure: (1) a lower unit containing Neoproterozoic and Cambrian strata, (2) a middle unit of Ordovician to Upper Mississippian strata, and (3) and an upper unit of Upper Mississippian to Lower Permian strata. The structure reflects the Sevier fold-thrust belt and subsequent extensional tectonics.This dataset was produced as part of a Utah Geological Survey (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 newer mapping in the area and the UGS 2017 data model. While the map is considered a good representation of the geology of the map area, users should be aware that it was released in 1988 and does not meet all modern cartographic, spatial control, or geologic standards. Not all features on the original map precisely match options in the 2017 UGS geologic map schema as noted below. Line attributes and symbology were selected from current (2017) UGS schema and do not necessarily match the intent of the original map. Selected attributes most closely represent the general geologic interpretation depicted by the original map, but are not an exact match.Marker bedsThese lines are now depicted as “Bed, marker A,” "Bed, marker B," and "Bed, marker C."High-Angle faultsThese lines are now depicted as normal faults or unknown faults.Low-Angle faultsThese lines are now depicted as unknown faults, detachment faults, or thrust faults.BeddingThese symbols are now depicted as “Bedding, inclined,” “Bedding, overturned,” and “Bedding, vertical.”Units – Unit Symbols/NamesThe following changes in formation and unit names were made. We added unit Csn – St. Charles Dolomite and Nounan Dolomite, undivided. We added queries to selected units where original map labeling was poor. We used the unit label Zmc? for the Maple Canyon Formation (?). We queried the Jefferson Formation (unit Dj?) herein, as this nomenclature is likely incorrect for this area; further work is needed. |