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| Miscellaneous Field Studies Map 2375                                                  |

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## GEOLOGIC MAP OF THE VAIL EAST QUADRANGLE, EAGLE COUNTY, COLORADO

#### By Karl S. Kellogg, Bruce Bryant, *and*Margaret H. Redsteer

| **Abstract**
      New 1:24,000-scale geologic mapping along the Interstate-70 urban corridor in western Colorado, in support of the State/USGS Cooperative Geologic Mapping Project, is contributing to a more complete understanding of the stratigraphy, structure, tectonic evolution, and hazard potential of this rapidly developing region.  The 1:24,000-scale Vail East quadrangle straddles the Gore fault system, the western structural boundary of the Gore Range.  The Gore fault system is a contractional structure that has been recurrently active since at least the early Paleozoic and marks the approximate eastern boundary of the Central Colorado trough, a thick late Paleozoic depocenter into which thousands of meters of clastic sediment were deposited from several uplifts, including the ancestral Front Range.  The Gore fault was active during both the late Paleozoic and Upper Cretaceous-lower Tertiary (Laramide) deformations. In addition, numerous north-northwest faults that cut the crystalline rocks of the Gore Range were active during at least 5 periods, the last of which was related to Neogene uplift of the Gore Range and formation of the northern Rio Grande rift.

Early Proterozoic crystalline rocks underlie the high Gore Range, north and east of the Gore fault system.  These rocks consist predominantly of migmatitic biotite gneiss intruded by mostly granitic rocks of the 1.667-1.750 Ma Cross Creek batholith, part of the 1,667-1,750 Ma Routt Plutonic Suite (Tweto, 1987).

Southwest of the Gore fault, a mostly gently south-dipping sequence of Pennsylvanian Mimturn Formation, as thick as 1,900 m, and the Permian and Pennsylvanian Maroon Formation (only the basal several hundred meters are exposed in the quadrangle)were shed from the ancestral Front Range and overlie a thin sequence of Devonian and Cambrian rocks. The Minturn Formation is a sequence of interlayered pink, maroon, and gray conglomerate, sandstone, shale, and marine limestone.  The Maroon Formation is mostly reddish conglomerate and sandstone.

Glacial till of both the middle Pleistocene Bull Lake and late Pleistocene Pinedale glaciations are well exposed along parts of the Gore Creek valley and its tributaries, although human development has profoundly altered the outcrop patterns along the Gore Creek valley bottom.  Landslides, some of which are currently active, are also mapped.

**Version 1.1**

Posted January 2006

This map is available at Information                Services (1-888-ASK-USGS)

Part or all of this report is presented              in Portable Document Format (PDF); the latest version              of Adobe Acrobat Reader or similar software is              required to view it. Download              the latest version of Acrobat Reader, free of charge. |
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| -  **Pamphlet** PDF            file (4.9 MB)
-  **Map** PDF            file (2.6 MB) | **For viewing and printing upon download.***A text version of the map and the pamphlet are accessible as defined in Section 508 of the Rehabilitation Act of 1973, Amendments of 1998.)* |
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| -  **Downloads** Directory | This geospatial database consists of topographic base map (ve_base), as well as ArcInfo &anp; ArcView shapefiles (mf-2375) contained in a gzipped tar archive or zip archive.  Both compressed archive files contain both types of geospatial database files.  Please refer to the file 2890.met for detailed metadata documentation. |
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| U.S. Department of the Interior | U.S. Geological Survey      URL: https://pubsdata.usgs.gov/pubs/mf/2003/mf-2375/Questions or Assistance: USGS Web ContactPage Last Modified: Thr Dec  1 12:09 EDT 2016 |  |

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