Tectonics, geochronology, and volcanism in the Southern Rocky Mountains and Rio Grande rift. Edited by Steven M. Cather, William C. McIntosh, and Shari A. Kelley Copyright (c) 2004 New Mexico Bureau of Geology and Mineral Resources Peter A. Scholle, Director and State Geologist A division of New Mexico Institute of Mining and Technology Daniel H. Ląpez, President 801 Leroy Place Socorro, NM 87801 (505) 835-5420 Web site: geoinfo.nmt.edu Bulletin 160 ISBN 1-883905-21-4 Issued in electronic format only Individual articles are also available for downloading (as PDFs) on our Web site at: http://geoinfo.nmt.edu/publications/bulletins/160 System Requirements/Recommendations All platforms: The PDF will require Adobe Reader 5.0 or later. The papers in this volume are PDF. The reader will find it most useful if the navigation tool bar is visible. All papers, sheets, and appendices will open in a NEW reader window. Close the new window to return to the Table of contents or to the paper you are currently viewing. Windows Adobe(r) Reader(r) 6.0.1 is included on this CD. Microsoft(r) Windows 98 Second Edition or later. 32MB of RAM (64MB recommended) 60MB of available hard-disk space Data Tables Microsoft Excel: PC 2000, Macintosh 2001 Macintosh Adobe(r) Reader(r) for Macintosh is a free download from www.adobe.com. PowerPC(r) G3 processor Adobe(r) Reader(r) 6.0.1--Mac OS X v.10.2.2-or newer Acrobat(r) Reader(r) 5--Mac OS 8.6 through OS X 32MB of RAM (64MB recommended) 70MB of available hard-disk space Older versions of MSExcel(r) for Mac may experience difficulties when opening some appendices. If a window titled "File Reservation" appears showing the file under modification, either choose "read only" or close the program and get the latest updates and fixes. Summary The fifteen papers included in this volume represent decades of research on the tectonic and volcanic history of the Southern Rocky Mountains and the Rio Grande rift of New Mexico and Colorado. Detailed geologic mapping, geophysics, and expanded geochronology datasets provide important new insights into the tectonic history of major fault zones in New Mexico and document a complex history of Laramide-age faulting. Authors address the Laramide-age structural development of the Front Range of Colorado and identify previously unrecognized trends in the timing and distribution of latest Eocene to Pliocene volcanism in Colorado and New Mexico. A wealth of new geochronologic data is provided, including hundreds of previously unpublished dates. Among other things, these dates document the eruptive history of the Ocate volcanic field and provide ages for some of the youngest lava flows in the state of New Mexico. The data in the appendices are provided in a form that allows them to be imported into other programs (including GIS software) for manipulation. Many of these papers are destined to become classics in the scientific literature on the Rio Grande rift and the Southern Rocky Mountains.