| USGS HomeContact USGSSearch USGS           |
|--------------------------------------------|
| Geologic Investigation Series I–2667 |

|                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------|
|  	About USGS / 	Science Topics / 	Maps, Products & Publications / 	Education / FAQ |
|                                                                                                                                     |

## Correlation of Jurassic San Rafael Group and related rocks from Blanding, Utah, to Dove Creek, Colorado

#### By Robert B. O'Sullivan

| The Middle Jurassic San Rafael Group consists of        sandstone, siltstone, and shale. In        the study area, the San Rafael Group is mostly concealed        beneath younger        rocks but does crop out along Comb Ridge and in the canyon of the Dolores        River in the        western and eastern parts of the study area respectively. In an intervening        area along Montezuma        Creek, the upper part of the San Rafael Group crops out for about 10        mi; at one      locality  all of the group is exposed.

 In the study area, two unconformities are associated        with the rocks described herein.        The unconformities separate the San Rafael Group from the underlying        Lower Jurassic Navajo        Sandstone and the overlying Upper Jurassic Morrison Formation. The unconformities—        termed J-2 at the base of the San Rafael and J-5 at the top—are        also recognized        throughout much of the Western Interior of the United States (Pipiringos        and O’Sullivan,        1978). The J-5 unconformity is the datum used to construct the line of        graphic sections and        the restored stratigraphic diagram of this report.

**Version 1.0**
Posted November 1998
Part or all of this report is presented in Portable Document Format. The latest version of Adobe Acrobat Reader or similar software is required to view it. If you wish to download the latest version of Acrobat Reader free of charge, click here. |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

| - **Report** PDF            file (155 KB) | **For viewing and printing.** |
|-------------------------------------------|-------------------------------|

| AccessibilityFOIAPrivacyPolicies and Notices                                                                                                                                                         |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| U.S. Department of the Interior | U.S. Geological Survey      URL: https://pubsdata.usgs.gov/pubs/imap/i-2667/Questions or Assistance: USGS Web ContactPage Last Modified: Wed Nov 30 17:33 EDT 2016 |  |

----