Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associated with the Midcontinent Rift System U.S. GEOLOGICAL SURVEY BULLETIN 1989-E 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 Chapter E Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associated with the Midcontinent Rift System By PIETER BERENDSEN and ANDRZEJ BARCZUK U.S. GEOLOGICAL SURVEY BULLETIN 1989 STRATEGIC AND CRITICAL MINERALS IN THE MIDCONTINENT REGION, UNITED STATES WARREN C. DAY and DIANE E. LANE, Editors U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Published in the Central Region, Denver, Colo. Manuscript approved for publication April 21, 1993. Photocomposition by Marie Melone 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 UNITED STATES GOVERNMENT PRINTING OFFICE: 1993 For sale by USGS Map Distribution Box 25286, Building 810 Denver Federal Center Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Berendsen, Pieter. Petrography and correlation of Precambrian clastic sedimentary rocks associated with the Midcontinent Rift System / by Pieter Berendsen and Andrzej Barczuk. p. cm. (U.S. Geological Survey bulletin ; 1989) (Strategic and critical minerals in the midcontinent region, United States; ch. E) Includes bibliographical references. Supt. of Docs, no.: I 19.3: 1989E 1. Geology, Stratigraphic Precambrian. 2. Rocks, Sedimentary Middle West. 3. Petrology Middle West. 4. Stratigraphic correlation Middle West. 5. Keweenawan Rift. I. Barczuk, Andrzej. II. Title. III. Series. IV. Series: Strategic and critical minerals in the midcontinent region, United States: ch. E. QE75.B9 no. 1989-E [QE653] 557.3 s dc20 (551.7'1'0977] 93^722 CIP CONTENTS Abstract El Introduction El Methodology El Generalized stratigraphy E2 Petrographic study of surface samples E2 Oronto Group E2 Copper Harbor Conglomerate E2 Nonesuch Shale E2 Freda Sandstone E4 Bayfield Group E6 Orienta Sandstone E6 Devils Island Sandstone E6 Chequamegon Sandstone E6 Bayfield Group Equivalent Rocks E9 Fond du Lac Formation E9 Hinckley Sandstone E9 Jacobsville Sandstone Ell Petrographic study of subsurface samples Ell Minnesota E12 Iowa E13 Nebraska El 5 Kansas E15 Modal analysis E16 Heavy-mineral analysis E17 Discussion E18 Acknowledgments E19 References cited E19 FIGURES El. Chart showing stratigraphic terminology and correlations of upper Keweenawan clastic rocks E3 E2. Generalized geologic map of the western Lake Superior region showing the distribution of and sample localities for Keweenawan surface rocks E3 E3. Triangular diagram showing petrographic composition of Precambrian sedimentary rocks of the northern part of the Midcontinent Rift System E8 E4. Triangular diagram showing petrographic composition of Precambrian sedimentary rocks of the northern part of the Midcontinent Rift System based on the composition of their constituent rock fragments E10 E5. Generalized geologic map showing the subsurface distribution of Keweenawan rocks in southern Minnesota, Iowa, and eastern Nebraska, and the location of drill holes discussed in text Ell E6. Map showing generalized distribution of Keweenawan-age rocks in Kansas and approximate location of drill holes from which samples were taken E12 E7. Chart showing preliminary stratigraphic correlation of drill-hole cuttings from Kansas with established stratigraphy in the northern part of the Midcontinent Rift System E16 Contents III TABLES El. Petrographic composition of volcaniclastic and clastic sedimentary rocks associated with the Midcontinent Rift System E5 E2. Heavy-mineral composition of volcaniclastic and clastic sedimentary rocks associated with the Midcontinent Rift System E7 E3. Heavy-mineral composition of core and cuttings from drill holes in Minnesota, Iowa, and Kansas E14 IV Contents STRATEGIC AND CRITICAL MINERALS IN THE MIDCONTINENT REGION, UNITED STATES Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associated with the Midcontinent Rift System By Pieter Berendsen 1 and Andrzej Barczuk2 Abstract offset with respect to each other. The initial extensional phase of rifting, beginning about 1,100 Ma, was accom­ Rocks from exposures in the Lake Superior region and panied by emplacement of sizable mafic intrusive bodies from core and cuttings of exploration drill holes in Iowa, and subsequent voluminous outpouring of mafic volcanic Nebraska, and Kansas were analyzed to correlate the sub­ rock. In the ensuing stages of rift development, initially surface clastic sedimentary rocks in the southern extension coarse and immature sediments, followed by increasingly of the Midcontinent Rift System with rocks of the estab­ finer and more mature sediments, collected in the basins lished Keweenawan stratigraphy in the Lake Superior that developed along the trend of the rift. The coarser region. Petrographic properties and heavy minerals were sediments contained a large percentage of debris derived used to characterize the various formations. Rocks similar from mafic volcanic rocks in the center of the rift, and the in character to those of the Oronto Group and the Bayfield younger, predominantly fluviatile sediments were domi­ Group are recognized in the subsurface in Iowa, Nebraska, nated by material from the rift shoulders. and Kansas. For comparative purposes, additional analy­ This study contributes information on the petrology ses were made on surface samples collected throughout and mineralogy of subsurface Precambrian sedimentary the Lake Superior region. rocks encountered in drill holes in Minnesota, Iowa, Nebraska, and Kansas. New data from surface samples collected as part of this study, together with published INTRODUCTION information on volcaniclastic and clastic rocks in the out­ crop area, allow for a comparison and initial correlation During the past five years cooperative studies by the between the subsurface stratigraphy of the rift and the Kansas Geological Survey and the U.S. Geological Survey exposed stratigraphic sequence in the Great Lakes region. (USGS) as part of the USGS Midcontinent Strategic and Critical Minerals Project (MSCM) have significantly con­ tributed to our understanding of the stratigraphy and struc­ METHODOLOGY ture of the Precambrian rocks associated with the Mid- continent Rift System, especially in that part of the rift where Phanerozoic rocks overlie the Precambrian. The During the first phase of this MSCM project 23 out­ approximately 1,000-mi (l,500-km)-long arm of the Mid- crops of the major post-volcanic clastic sedimentary rocks continent