Title: Geologic Map of the Central Beaverhead Mountains, Lemhi County, Idaho, and Beaverhead County, Montana By Karen Lund 2018 U.S. Geological Survey Scientific Investigations Map 3413 U.S. Geological Survey data release https://doi.org/10.5066/P905PTI4 ABSTRACT: This geologic map of the central Beaverhead Mountains portrays a complex geologic history of depositional basin development interspersed with deformational events. Generalized geology for young basins, compiled from sources on both sides of the range, is combined with newly mapped bedrock geology to better integrate geologic development of the map area. Successive extensional basins were obliquely oriented across deformed strata of each preceding basin and of the Paleoproterozoic basement. Strata deposited in these basins include (1) thick fine-grained arkosic strata of the Mesoproterozoic Lemhi basin deposited on Paleoproterozoic basement with shoreline exposed on the east side of the map, (2) siliciclastic and carbonate strata of the Late Neoproterozoic-early Paleozoic miogeocline that were deposited in deeper environments to the west and interfingered with cratonal basin deposits to the east, and (3) generally coarse deposits in several nested, fault-bounded Eocene to Holocene basins. Syndepositional structural disruption including tilting and angular unconformities is present within strata and between stratigraphic packages formed during the different basin-filling events. Cretaceous, east-northeast-directed thrust faults inverted Mesoproterozoic and Neoproterozoic-Paleozoic basins and stacked strata from diverse stratigraphic packages and different depositional settings. The thrust plates rotated as they impinged on the Paleoproterozoic arch on the east side of the map, resulting in complex fault geometries that present as thrust faults to oblique reverse and tear (or ramp) fault along different fault segments. Cenozoic extension caused successive normal-fault basins of several orientations. Eocene volcanic rocks are preserved in fault-bounded depositional basins formed during the onset of Cenozoic extension. Eocene basins were obliquely overprinted by Oligocene-Miocene normal-fault basins. Holocene basins developed during steep normal faulting that formed the present Basin and Range topography. This geologic map of the central Beaverhead Mountains is mapped at 1:24,000 scale and printable at 1:50,000 scale. These data were collected between 1997 and 2017 and synthesized to provide significant new stratigraphic and structural data and interpretations. DISCLAIMERS: This database, identified as SIM 3413, has been approved for release by the U.S. Geological Survey (USGS). Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty, expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey. Although this information product, for the most part, is in the public domain, it also may contain copyrighted material as noted in the text. Permission to reproduce copyrighted items for other than personal use must be secured from the copyright owner. REPORT FILES: The map, pamphlet, and readme files for this report are located at and can be downloaded via the Web from at the U.S. Geological Survey publications website at https://doi.org/10.3133/sim3413. List of files: sim3413_00ReadMe.txt sim3413_pamphlet.pdf sim3413_sheet.pdf som3413_sheet_georeferenced.pdf HOW TO OBTAIN THE DIGITAL MAP FILES: The map sheet can be obtained via the Internet from the U.S. Geological Survey publications website. Go to the web page at https://doi.org/10.3133/sim3413/ and follow the directions to download the files. The map product is a Portable Document Format (.pdf) map, which requires Adobe Acrobat for viewing. The Portable Document Format (PDF) file can be downloaded, from which paper copies may be printed. Acrobat software runs on a variety of systems, and is available for download free of charge from Adobe at http://www.adobe.com. Suggested citation: Lund, K., 2018, Geologic map of the central Beaverhead Mountains, Lemhi County, Idaho, and Beaverhead County, Montana: U.S. Geological Survey Scientific Investigations Map 3413, pamphlet 27 p., scale 1:50,000, https://doi.org/10.3133/sim3413. DATA RELEASE GIS AND OTHER FILES The GIS database (data release) for this report is located at and can be downloaded via the Web from ScienceBase at https://doi.org/10.5066/P905PTI4 List of files: Beaverhead_metadata_.txt Beaverhead_base.tif (Upper Arkansas sim3413 topographic base) Beaverhead_base.tfw Beaverhead_Hillshade.tif (Osage SW sim3413 shaded relief base) Beaverhead_Hillshade.tfw Beaverhead_GeMS.gdb CorrelationOfMapUnits CrossSectionA GeologicMap OrientationPoints StructureContourPoints CartographicLines Contact and Faults GeologicLines StructureContourLines DataSourcePolys MapUnitPolys DataSources DescriptionOfMapUnits GeoMaterialDict Glossary shapefiles directory: OrientationPoints.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) point StructureContourPoints.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) point CartographicLines.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) line Contact and Faults.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) line GeologicLines.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) line StructureContourLines.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) line DataSourcePolys.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) polygon MapUnitPolys.shp (.dbf/.prj/.sbn/.sbx/.shx.xml/.shx) polygon SIM3413GIS.gdb directory (contains GIS data as geodatabase feature classes). HOW TO OBTAIN THE DIGITAL GIS FILES: The digital files constituting the geologic map database of this report can be obtained via the Internet from the U.S. Geological Survey ScienceBase website. Go to the web page at https://doi.org/10.5066/P905PTI4 and follow the directions to download the files. Suggested citation: Giles, S.A., and Lund, K., 2018, Digital data for the geologic map of the Central Beaverhead Mountains, Lemhi County, Idaho, and Beaverhead County, Montana: U.S. Geological Survey data release, https://doi.org/10.5066/P905PTI4. ArcReader may be downloaded free of charge from http://www.esri.com/software/arcgis/arcreader/download for viewing additional files included in this report. These maps are offered as an online-only, digital publication. Users should be aware that, because of differences in rendering processes and pixel resolution, some slight distortion of scale may occur when viewing it on a computer screen or when printing it on an electronic plotter, even when it is viewed or printed at its intended publication scale.