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West-Central Utah AVAILABILITY of BOOKS and MAPS of the U.S Isotopic Ages and Stratigraphy of Cenozoic Rocks of the Marysvale Volcanic Field and Adjacent Areas, West-Central Utah AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications re­ leased prior to the current year are listed in the most recent annual "Price and Availability List." Publications that may be listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" may no longer be available. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices listed below. BY MAIL OVER THE COUNTER Books Books and Maps Professional Papers, Bulletins, Water-Supply Papers, Tech­ Books and maps of the U.S. Geological Survey are available niques of Water-Resources Investigations, Circulars, publications over the counter at the following U.S. Geological Survey offices, all of general interest (such as leaflets, pamphlets, booklets), single of which are authorized agents of the Superintendent of Docu­ copies of Earthquakes & Volcanoes, Preliminary Determination of ments. Epicenters, and some miscellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from • ANCHORAGE, Alaska-Rm. 101, 4230 University Dr. U.S. Geological Survey, Map Distribution • LAKEWOOD, Colorado-Federal Center, Bldg. 810 Box 25286, MS 306, Federal Center Denver, CO 80225 • MENLO PARK, California-Bldg. 3, Rm. 3128, 345 Middlefield Rd. Subscriptions to periodicals (Earthquakes & Volcanoes and Preliminary Determination of Epicenters) can be obtained ONLY • RESTON, Virginia-USGS National Center, Rm. 1C402, from the 12201 Sunrise Valley Dr. Superintendent of Documents • SALT LAKE CITY, Utah-Federal Bldg., Rm. 8105, Government Printing Office 125 South State St Washington, DC 20402 • SPOKANE, Washington-U.S. Post Office Bldg .• Rm. 135, (Check or money order must be payable to Superintendent of West 904 Riverside Ave. Documents.) • WASHINGTON, D.C.-Main Interior Bldg., Rm. 2650, Maps 18th and C Sts .• NW. For maps, address mail orders to Maps Only U.S. Geological Survey, Map Distribution Maps may be purchased over the counter at the following Box 25286, Bldg. 810, Federal Center U.S. Geological Survey offices: Denver, CO 80225 Residents of Alaska may order maps from • FAIRBANKS, Alaska-New Federal Bldg, 101 Twelfth Ave. U.S. Geological Survey, Earth Science Information Center • ROLLA, Missouri-1400 Independence Rd. 101 Twelfth Ave., Box 12 Fairbanks, AK 99701 • STENNIS SPACE CENTER, Mississippi-Bldg. 3101 Isotopic Ages and Stratigraphy of Cenozoic Rocks of the Marysvale Volcanic Field and Adjacent Areas, West-Central Utah By Peter D. Rowley, Harald H. Mehnert, Charles W. Naeser, Lawrence W. Snee, Charles G. Cunningham, Thomas A. Steven, John J. Anderson, Edward G. Sable, and R. Ernest Anderson U.S. GEOLOGICAL SURVEY BULLETIN 2071 An update of the Cenozoic stratigraphy of the Marysvale volcanic field, based on new and published K-Ar, fission-track, and 40ArP 9Ar ages on igneous rocks UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1994 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director For Sale by U.S. Geological Survey, Map Distribution Box 25286, MS 306, Federal Center Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Library of Congress Cataloging-in-Publication Data Isotopic ages and stratigraphy of Cenozoic rocks of the Marysvale volcanic field and adja­ cent areas, west-central Utah I by Peter D. Rowley... [et al.]. p. em.- (U.S. Geological Survey Bulletin ; 2071) "An update of the Cenozoic stratigraphy of the Marysvale volcanic field, based on new and published K-Ar, fission-track, and 40Arf39 Ar ages on igneous rocks." Includes bibliographical references. Supt. of Docs. no.: I 19.3:2071 1. Geology, Stratigraphic-Cenozoic. 2. Rocks, Igneous-Utah-Marysvale Region. 3. Radioactive dating-Utah-Marysvale Region. I. Rowley, Peter D. II. Series. QE75.B9 no. 2071 [QE690] 557.3 s-dc20 [551.7'8'09792] 93-41469 CIP CONTENTS Abstract........................................................................................................................... 1 Introduction..................................................................................................................... 2 Geologic Setting.............................................................................................................. 4 Lower Cenozoic Sedimentary Sequence . .. .. .. .. ... .. .. .. .. .. .. .......... .. .. .. .. .. .. .. .. .. .. 9 Claron Formation and Related Units ... .. ....... .. .......... .. ......... .. ............. ........ .. ...... 9 Middle Cenozoic Calc-alkaline Igneous Sequence......................................................... 11 Bullion Canyon Volcanics . .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. 11 Mount Dutton Formation...................................................................................... 12 Intertongued Great Basin Ash-flow Sheets........................................................... 13 Local Volcanic Centers......................................................................................... 14 Monroe Peak Caldera............................................................................................ 17 Calc-alkaline Intrusions .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 18 Upper Cenozoic Sedimentary and Bimodal Igneous Sequence ...................................... 21 Potassium-rich Mafic Volcanic Rocks.................................................................. 21 Mount Belknap Volcanics..................................................................................... 23 Small Rhyolite Volcanic Centers.......................................................................... 24 Silicic Intrusions . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. 24 Basalt Lava Flows................................................................................................. 26 Basin-fill Sedimentary Rocks............................................................................... 27 Conclusions..................................................................................................................... 28 References Cited . .. .... .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. 29 FIGURES 1. Index map showing location of the Marysvale volcanic field, Utah............................................................................. 3 2. Composite stratigraphic column of Cenozoic rocks in and near the Marysvale volcanic field ....... .. .. ......... ................ 5 3. Generalized geologic map, showing locality of samples whose ages and analytical data are reported here................ 7 4. Graphs of 40 ArP9 Ar age spectrum for biotite and sanidine of sample 83-69X............................................................ 21 TABLES 1. Data for potassium-argon dates, Marysvale volcanic field and adjacent areas, Utah................................................... 10 2. Data for fission-track dates, Marysvale volcanic field and adjacent areas, Utah.......................................................... 18 3. Data for 40 ArJ39 Ar dates for biotite and sanidine from sample 83-69X, eastern Sevier Plateau, Utah........................ 20 III Isotopic Ages and Stratigraphy of Cenozoic Rocks of the Marysvale Volcanic Field and Adjacent Areas, West-Central Utah By Peter D. Rowley, Harald H. Mehnert, Charles W. Naeser, Lawrence W. Snee, Charles G. Cunningham, Thomas A. Steven, John J. Anderson,1 Edward G. Sable, and R. Ernest Anderson ABSTRACT The Marysvale volcanic field lies at the east end of the The middle Cenozoic calc-alkaline rocks centered in east-northeast-trending Pioche-Marysvale igneous belt, the the northern and central Tushar Mountains and northern site of extensive Cenozoic volcanism and mineralization Sevier Plateau are mostly relatively highly evolved dacite above a major batholith complex. The field is mostly in the and subordinate andesite called the Bullion Canyon Volca­ High Plateaus transition zone between the Great Basin and nics, deposited between about 34? and 22 Ma. Deposits from the main part of the Colorado Plateau. Cenozoic rocks of the volcanic centers that intertongue on the north include the Marysvale field can be divided into three main sequences: andesitic to dacitic volcanic rocks of Dog Valley and the (1) lower Cenozoic (Paleocene through Oligocene) fluvial­ overlying andesitic to dacitic volcanic rocks of Wales Can­ lacustrine sedimentary rocks (mostly the Claron Formation) yon. Deposits from volcanic centers that intertongue on the that overlie Paleozoic and Mesozoic rocks with angular east include the andesitic volcanic rocks of Signal Peak, the unconformity; (2) thick, middle Cenozoic (Oligocene and andesitic volcanic rocks
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