Black, Giraud, Mayes Paleoseismology of Utah, Volume 9 PALEOSEISMICPALEOSEISMIC INVESTIGATIONINVESTIGATION OFOF THETHE CLARKSTON,CLARKSTON, JUNCTIONJUNCTION HILLS,HILLS, ANDAND WELLS-WELLS- VILLEVILLE FAULTS,FAULTS, WESTWEST CACHECACHE FAULTFAULT ZONE,ZONE, CACHECACHE COUNTY,COUNTY, UTAHUTAH by PALEOSEISMIC INVESTIGATION - WEST CACHE FAULT ZONE, CACHE COUNTY, UTAH UGS Special Study 98 UTAH ZONE, CACHE COUNTY, CACHE FAULT WEST - INVESTIGATION PALEOSEISMIC Bill D. Black, Richard E. Giraud, and Bea H. Mayes Utah Geological Survey SPECIAL STUDY 98 UTAH GEOLOGICAL SURVEY a division of 2000 Utah Department of Natural Resources STATE OF UTAH Michael O. Leavitt, Governor DEPARTMENT OF NATURAL RESOURCES Kathleen Clarke, Executive Director UTAH GEOLOGICAL SURVEY Kimm M. Harty, Acting Director UGS Board Member Representing Craig Nelson (Chairman)...............................................................................................................Civil Engineering D. Cary Smith .................................................................................................................................. Mineral Industry C. William Berge ........................................................................................................................... Mineral Industry E.H. Deedee O’Brien ........................................................................................................................ Public-at-Large Robert Robison ............................................................................................................................... Mineral Industry Charles Semborski .......................................................................................................................... Mineral Industry Richard R. Kennedy ................................................................................................. Economics-Business/Scientific David Terry, Director, Trust Lands Administration ...................................................................... Ex officio member UTAH GEOLOGICAL SURVEY The UTAH GEOLOGICAL SURVEY is organized into five geologic programs with Administration, Editorial, and Computer Resources providing necessary support to the programs. The ECONOMIC GEOLOGY PROGRAM undertakes studies to identify coal, geothermal, uranium, hydrocarbon, and industrial and metallic resources; initiates detailed studies of these resources including mining dis- trict and field studies; develops computerized resource data bases, to answer state, federal, and industry requests for information; and encourages the prudent development of Utah’s geologic resources. The APPLIED GEOLOGY PROGRAM responds to requests from local and state governmental entities for engineering-geologic investigations; and identifies, documents, and interprets Utah’s geologic hazards. The GEOLOGIC MAPPING PROGRAM maps the bedrock and surficial geology of the state at a regional scale by county and at a more detailed scale by quadrangle. The GEOLOGIC EXTENSION SERVICE answers inquiries from the public and provides information about Utah’s geology in a non-technical format. The ENVIRONMENTAL SCIENCES PROGRAM maintains and publish- es records of Utah’s fossil resources, provides paleontological and archeological recovery services to state and local governments, con- ducts studies of environmental change to aid resource management, and evaluates the quantity and quality of Utah’s ground-water resources. The UGS Library is open to the public and contains many reference works on Utah geology and many unpublished documents on aspects of Utah geology by UGS staff and others. The UGS has several computer data bases with information on mineral and energy resources, geologic hazards, stratigraphic sections, and bibliographic references. Most files may be viewed by using the UGS Library. The UGS also manages a sample library which contains core, cuttings, and soil samples from mineral and petroleum drill holes and engineer- ing geology investigations. Samples may be viewed at the Sample Library or requested as a loan for outside study. The UGS publishes the results of its investigations in the form of maps, reports, and compilations of data that are accessible to the public. For information on UGS publications, contact the Natural Resources Map/Bookstore, 1594 W. North Temple, Salt Lake City, Utah 84116, (801) 537-3320 or 1-888-UTAH MAP. E-mail: [email protected] and visit our web site at http://www.ugs.state.ut.us. UGS Editorial Staff J. Stringfellow ....................................................................................................................................................Editor Vicky Clarke, Sharon Hamre...............................................................................................................Graphic Artists Patricia H. Speranza, James W. Parker, Lori Douglas...........................................................................Cartographers The Utah Department of Natural Resources receives federal aid and prohibits discrimination on the basis of race, color, sex, age, national origin, or disability. For information or complaints regarding discrimination, contact Executive Director, Utah Department of Natural Resources, 1594 West North Temple #3710, Box 145610, Salt Lake City, UT 84116-5610 or Equal Employment Opportunity Commission, 1801 L Street, NW, Washington DC 20507. Printed on recycled paper 2/00 FOREWORD This Utah Geological Survey Special Study, Paleoseismic Investigation of the Clarkston, Junction Hills, and Wellsville faults, West Cache fault zone, Cache County, Utah, is the ninth report in the Paleoseismology of Utah Special Studies series. This series makes the results of paleoseismic investigations in Utah available to geoscientists, engineers, planners, public officials, and the general public. These studies provide critical infor- mation on earthquake timing, recurrence, displacement, slip rate, and fault geometry which can be used to char- acterize potential seismic sources and evaluate the long-term earthquake hazard presented by Utah's Quaternary faults. Field work for this paleoseismic investigation was performed in 1997 at three sites (Winter Canyon, Roundy Farm, and Deep Canyon) on the Clarkston, Junction Hills, and Wellsville faults. These faults, along with sev- eral lesser associated faults nearby, comprise the West Cache fault zone on the west side of Cache Valley (Solomon, 1999). No previous paleoseismic studies had been conducted on these faults. Surficial geologic map- ping of the fault zone and initial paleoseismic study results were presented by Black and Solomon (1998) to the 93rd Annual Meeting of the Seismological Society of America in Boulder, Colorado. Those results showed that recent movement on the faults was much younger than previously thought. The information reported here on the size, timing, and recurrence of surface-faulting earthquakes on the West Cache fault zone is critical to pub- lic officials, planners, and others making decisions regarding earthquake-hazard mitigation in Cache Valley and the northern Wasatch front. William R. Lund, Series Editor Utah Geological Survey Other reports in the Paleoseismology of Utah series Special Study 75. Paleoseismology of Utah, Volume 1: Fault behavior and earthquake recurrence on the Provo segment of the Wasatch fault zone at Mapleton, Utah County, Utah, by W.R. Lund, D.P. Schwartz, W.E. Mulvey, K.E. Budding, and B.D. Black, 41 p., 1991 Special Study 76. Paleoseismology of Utah, Volume 2: Paleoseismic analysis of the Wasatch fault zone at the Brigham City trench site, Brigham City, Utah and the Pole Patch trench site, Pleasant View, Utah, by S.F. Personius, 39 p., 1991 Special Study 78. Paleoseismology of Utah, Volume 3: The number and timing of paleoseismic events on the Nephi and Levan segments, Wasatch fault zone, Utah, by Michael Jackson, 23 p., 3 p., 1991 Special Study 82. Paleoseismology of Utah, Volume 4: Seismotectonics of north-central Utah and southwestern Wyoming, by Michael W. West, 93 p., 5 pl., 1:100,000, 1994 Special Study 83. Paleoseismology of Utah, Volume 5: Neotectonic deformation along the East Cache fault zone, Cache County, Utah, by J.P. McCalpin, 37 p., 1994 Special Study 88. Paleoseismology of Utah, Volume 6: The Oquirrh fault zone, Tooele County, Utah: surficial geology and paleoseismicity, W.R. Lund, editor, 64 p., 2 pl., 1:24,000, 1996 Special Study 92. Paleoseismology of Utah, Volume 7: Paleoseismic investigation on the Salt Lake City segment of the Wasatch fault zone at the South Fork Dry Creek and Dry Gulch sites, Salt Lake County, Utah, by B.D. Black, W.R. Lund, D.P. Schwartz, H.E. Gill, and B.H. Mayes, 22 p., 1 pl., 1996 Special Study 93. Paleoseismology of Utah, Volume 8: Paleoseismic investigation at Rock Canyon, Provo segment, Wasatch fault zone, Utah County, Utah, by W.R. Lund and B.D. Black, 21 p., 2 pl., 1998 Map 172 Surficial geologic map of the West Cache fault zone and nearby faults, Box Elder and Cache Counties, Utah, by B.J. Solomon, 1999, at a scale of 1:500,000 is another publi- cation related to this study. CONTENTS ABSTRACT . 1 INTRODUCTION . 1 GEOLOGIC SETTING . 2 PALEOSEISMIC INVESTIGATIONS AND DATA . 4 Radiocarbon Dating . 4 Clarkston Fault . 6 Geology . 6 Sequence of Deposition and Faulting in the Winter Canyon Trench . 8 Earthquake Timing and Recurrence . 8 Displacement and Slip Rate . 9 Junction Hills Fault . 9 Geology . 9 Sequence of Deposition and Faulting in the Roundy Farm Stream Cut . 11 Earthquake Timing and