AN ABSTRACT OF THE THESIS OF John Byron Alexander for the M. S. in Geology (Name) (Degree) Major) Date thesis is presented ! /1) Q TitleSTRATIGRAPHY AND TRUCTURE OF PART OF THE FISH LAKE PLATEAU, SEVIER COUNTY, UTAH Abstract approved Major Pr ofessor) Over 3, 000 feet of nonmarine Late Cretaceous sedimentary rocks are exposed within the northern Fish Lake Plateau. The Cre- taceous strata are overlain by over 2, 000 feet of Early Tertiary non- marine sedimentary rocks and volcanics.Landslide deposits cover over one-half of the area. The Late Cretaceous Blackhawk Formation, the oldest forma- tion exposed, was deposited in fluvial, swamp, coastal lagoon, and possibly shallow marine environments during the eastward retreat of the Mancos sea.This formation is overlain disconformably by the Late Cretaceous Price River Formation which is composed largely of quartz arenites derived from Paleozoic and Mesozoic sedimentary rocks exposed to the west.The sediments were carried into the area by streams and were deposited under piedmont and flood plain condi- tions. The Late Cretaceous and Early Tertiary North Horn formation conformably overlies the Price River Formation. The lower part is composed largely of fluvial sandstones but, in the upper part, lacus- trine mudstones and siltstones predominate.The latter were deposited in the Uinta Lake which persisted until late middle Eocene. In this lake the Early Tertiary Flagstaff, Colton and Green River For- mations were deposited in succession.After an interval of erosion, the Eocene Gray Gulch Formation was deposited and, later, lavas of Oligocene age. Two periods of folding are reflected by structures within the area.The Early Laramide orogeny caused the disconformity between the Blackhawk and Price River Formations, and a later period of folding, between the late Eocene and Miocene, formed the Wasatch and Gates Creek monoclines.Late Tertiary normal faulting has been superimposed on the earlier structures. There do not appear to be favorable structures for the accum- ulation of oil and gas. However, stratigraphic conditions exist for both the formation and accumulation of oil and gas.The Mancos Shale, a known source rock for oil and gas farther to the east, is present in the sub-surface.Sand pinchouts in Late Cretaceous strata are believed to exist in the subsurface.Potential production in this area will depend on the presence of these updip sand pinchouts. STRATIGRAPHY AND STRUCTURE OF PART OF THE FISH LAKE PLATEAU, SEVIER COUNTY, UTAH by John Byron Alexander A THESIS submitted to OREGON STATE UNIVERSITY in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE June 1964 APPROVED: In Charge of Major "/,V, k 4,jlht-t" Chairman of the Department of Geology Deanof Graduate School Date thesis is presented' Q/'/f65 Typed by Trudie Vallier ACKNOWLEDGMENTS The writer wishes to thank the Union Oil Company of Califor- nia for providing financial assistance during the fieldwork.Special thanks are due to Mr. George H. Feister, of Union Oil Company of California, who visited the writer in the field and offered valuable suggestions and advice. Appreciation is extended to Dr. Keith F. Oles, my major R professor, for his invaluable advice and careful editing of the manu- script. Acknowledgments are due the following members of Oregon State University Department of Geology: Dr. W. D. Wilkinson, Chair- man of the Department, who visited the writer in the field and criti- cally read the manuscript; and Dr. Harold E. Enlows, who suggested the thesis problem, accompanied the writer on a preliminary recon- naissance of the thesis area, and also critically read the manuscript. Special thanks are also extended to Mr. William Hill, Forest Supervisor, Fish Lake National Forest, and to his assistants for their help in obtaining maps and answering many questions concern- ing the region. The writer would also like to thank the many inhabitants of Salina, Utah and particularly Mr. and Mrs. Ivan Mills for their hospitality and friendship. TABLE OF CONTENTS Page INTRODUCTION....................................... 1 Location and Accessibility.......................... 1 Purposes and Methods of Investigation................ 3 Previous Work..................................... 5 Relief......... .................................. 6 Drainage.......................................... 6 Climate........................................... 8 Vegetation ......................................... 9 STRATIGRAPHY ....................................... Regional Stratigraphy............................... Thesis Area Stratigraphy........................... Subsurface Stratigraphy......................... Surface Stratigraphy............................. Blackhawk Formation........................ Price River Formation ....................... North Horn Formation ...... ............... Flagstaff Formation...................... Colton Formation......................... Green River Formation ...................... Gray Gulch Formation ....................... Tertiary Lavas .............................. Unconsolidated Sediments .................... STRUCTURAL GEOLOGY ............................... 74 Regional Structure................................. 74 Thesis Area Structure.............................. 76 Folds.......................................... 76 Wasatch Monocline 76 Gates Creek Monocline....................... 78 Other Folds................................. 78 Faults......................................... 79 Musinia Graben ............................. 81 Water HollowGraben........................ 82 GEOMORPHOLOGY .................................... 85 Stream Erosion .................................... 85 Terraces.......................................... 86 Pedimentation ..................................... 87 Landsliding ........................................ 89 HISTORICAL GEOLOGY ................................ 92 TABLE OF CONTENTS (Cont.) Page ECONOMIC GEOLOGY ................................. 96 Oil and Gas ........................................ 96 Possible Reservoir Rocks ........................ 96 Structural and Stratigraphic Traps ................ 98 Oil and Gas Possibilities ........................ 100 Coal .............................................. 100 BIBLIOGRAPHY ....................................... 103 LIST OF FIGURES Figure Page 1 GooseberryValley ............................... 7 2 Dip slopes formed on strataof theNorth Horn For- mation........................................ 7 3 Vertical cliff formed by the Castlegate Member of the Price River Formation...................... 22 4 Coal seam in the Blackhawk Formation ........... 22 5 Rose diagrams recording the results of measure- ments of foreset cross-laminations............... 24 6 Outcrop of the Price River Formation in the Water Hollow graben.................................. 28 7 Castlegate Member of the Price River Formation rising out of the subsurface in Salina Canyon...... 28 8 Outcrop of the upper member of the Price River Formation in Salina Canyon................... 30 9 Conglomerate and sandstone in the Castlegate Member of the Price River Formation ............ 30 10 Cuesta in Gooseberry Valley formed on strata of the North Horn Formation .................... 35 11 Sandstone lense in the North Horn Formation along Salina Creek ................................... 35 12 Outcropof theFlagstaff Formation at the north end of GooseberryValley ............................ 41 13 Outcrop of Flagstaff limestone east of the Salina Reservoir ..................................... 45 14 The nearly horizontal Flagstaff Formation over- lying steeply dipping strata of the Indianola Group in Salina Canyon ................................ 50 15 Gradational contact between the Green River and the underlying Colton Formation in Gooseberry Valley....................................................................... 53 LIST OF FIGURES (Cont.) Figure Page 16 Cross-bedded sandstones and conglomerates within the Colton (?) Formation.................. 57 17 Outcrop of the Gray Gulch Formation north of Gates Lake.......................................... 66 18 View south from near Salina Reservoir showing a cliff formed by Tertiary lava flows............... 70 19 Toe of the Wasatch monocline viewed from the cen- ter of Sevier Valley............................. 80 20 Drag fold in the Blackhawk Formation on the north side of Salina Creek............................. 80 21 View of the western boundary fault of the Musinia graben........................ 83 22 View north into Brown's Hole .................... 83 23 Pediment surface forming Flat Top Mountain between Niotche and Yogo Creeks........................ 88 24 Landsliding in the southern part of the area, below the lava covered plateau......................... 91 LIST OF PLATES Plate Page 1 Map of Utah showing location of thesisarea........ 2 2 Index map of central Utah physiographic subdivisions................................... 4 3 Geologic map of part of the Northern Fish Lake Plateau ....................................... 102 LIST OF TABLES Table Page 1 Correlation chart ................................ 12 2 Stratigraphic units exposed in the Northern Fish Lake Plateau.................................... 18 3 Summary of oil and gas test holes in the thesis area..97 STRATIGRAPHY AND STRUCTURE OF PART OF THE FISH LAKE PLATEAU, SEVIER COUNTY, UTAH INTRODUCTION Location and Accessibility The area investigated is located in the central part of Sevier County, Utah, approximately