Geologic Map of the Mount Sherman 7.5' Quadrangle, Park and Lake Counties, Colorado By Robert G. Bohannon and Chester A. Ruleman 2013 Scientific Investigations Map 3271 ABSTRACT The Mount Sherman 7.5- minute quadrangle is located along the crest of the Mosquito Range in between Leadville and Fairplay, Colorado. There are eleven 13,000-foot peaks and one fourteener, Mount Sherman, within the quadrangle. General elevations range from 10,400–14,036 feet (3,200–4,278 meters). The western half of the quadrangle primarily consists of Proterozoic granitic rocks reverse faulted over Paleozoic sedimentary rocks during the Laramide orogeny of late Cretaceous and Paleocene time. Coeval to this contractional event, sills and laccoliths of the White porphyry group (which probably includes rocks equivalent to the Pando Porphyry) were emplaced in the surrounding country rocks. Igneous activity continued into the Late Eocene with the emplacement of the Sacramento Porphyry (about 43.9 Ma) and the Gray porphyry group (about 36.7 Ma), and as young as 29 Ma to the north within the Climax quadrangle. With the inception of the Rio Grande rift within the region, the Paleozoic sedimentary rocks and Late Cretaceous to early Oligocene igneous rocks were extensionally faulted and tilted to the east. This resulted in the present 20–30 degree dip-slope of these rocks on top of Proterozoic basement rocks within the eastern half of the quadrangle. This extensional regime has continued well into the Pliocene. Within the southwestern quadrant, suspicious lineaments, alignment of springs, and continuous, measureable escarpments provide reasonable evidence for Quaternary tectonic activity along the western flank of the range. Pleistocene glaciers have dramatically sculpted the region, providing exceptional exposure of the region’s bedrock and structure. DISCLAIMERS Although this information product, for the most part, is in the public domain, it also contains copyrighted material as noted in the text. Permission to reproduce copyrighted items for other than personal use must be secured from the copyright owner. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey. This database, identified as SIM 3271, has been approved for release and publication by the Director of the 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 U.S.Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. DATA FILES List of files: 00ReadMe.txt SIM3271.pdf SIM3271.met Datafiles directory MountSherman_topo.tif/tfw/tfwx MountSherman_topo_invert_trans.tif (transparent topographic base) MountSherman_shd.tif/tfw MountSherman_final.gdb.zip directory (contains GIS data as geodatabase feature classes) MtSherman-shd MtSherman_topo Geology MountSherman_faultconcealed MountSherman_folds MountSherman_labels MountSherman_lines MountSherman_pnts MountSherman_polys MountSherman_xsections SIM3271_shapefiles.zip directory: MountSherman_faultconcealed.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_folds.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_labels.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_lines.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_pnts.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_polys.shp (dbf/prj/sbn/sbx/shp.xml/shx) MountSherman_xsections.shp (dbf/prj/sbn/sbx/shp.xml/shx) HOW TO OBTAIN THE DIGITAL FILES The digital files constituting the geologic map database of this report can be obtained via the Internet from the U.S. Geological Survey publications website. Go to the web page at http://pubs.usgs.gov/sim/3271/ and follow the directions to download the files. The main product is a Portable Document Format (.pdf) map, which requires Adobe Acrobat for viewing, and 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. ArcReader may be downloaded free of charge from http://www.esri.com/software/arcgis/arcreader/download.htm for viewing additional files included in this report.