GEOLOGY I YOUNG STUDIES f UNIVERSITY Volume 12 December 1965 r' r' CONTENTS Thrusting in the Southern Wasatch Mountains, Utah ........ Michael J. Brady 3 Nebo Overthrust, Southern Wasatch Mountains, Utah ........ B. Allen Black 55 Paleoecologic implications of Strontium, Calcium, and Magnesium in Jurassic rocks near Thistle, Utah .... Button W. Bordine 91 Paleoecology of the Twin Creek Limestone In the Thistle, Utah area .................................... .... .....Ladell R. Bullock 121 Geolo of the Stockton stock and related intmsives, &1e County, Utah ................................................. John L. Lufkin 149 Stratigraphy and rifera of Ordovician rocks near Columbia Iceads, Jasper National Park, Alberta, Canada .............................................................. .. .... J. Keith Rigby 165 Lower Ordovician conodonts and other microfossils from the Columbia Icefields Section, Alberta, Canada ........................... .. .......... R. L. Ethington and D. L. Clark 185 Publications and maps of the Geology Department ........................... .. ..... 207 Brigham Young University Geology Studies Volume 12 - December 1965 Contents Thrusting in the Southern Wasatch Mountains, Utah ........ Michael J. Brady 3 Nebo Overthrust, Southern Wasatch Mountains, Utah ........ B. Allen Black 55 Paleoecologic irriplications of Strontium, Calcium, and Magnesium in Jurassic rocks near Thistle, Utah .... Burton W. Bordine 91 Paleoecology of the Twin Creek Limestone in the Thistle, Utah area .................................................... Ladell R. Bullock 121 Geology of the Stockton stock and related intrusives, Tooele County, Utah .................................................... John L. Lufkin 149 Stratigraphy and porifera of Ordovician rocks near Columbia Icefields, Jasper National Park, Alberta, . Canada .......................................................................... J. Kelth Rlgby 165 Lower Ordovician conodonts and other microfossils from the Columbia Icefields Section, Alberta, Canada ............................................ R. L. Ethington and D. L. Clark 185 Publications and maps of the Geology Department ........................................ 207 A publication of the Department of Geology Brlgham Young University Provo, Utah 84601 Ed~tor J. Keith Rigby Editorial Staff Lehi F. Hintze Myron G. Best Brzgham Your~gUniuerszty Geology Studres is published annually by the Department. Geology Studies consists of graduate student and staff research in the Department and occasional papers from other contributors, and is the successor to BYU Research Studies, Geology Serier, published in separate numbers from 1954 to 1960. Distributed December 31, 1965 Prrce $4.00 Nebo Overthrust, Southern Wasatch Mountains, Utah* ABSTRACT.-An overturned and in part recumbent anticline trends slightly east of north and forms the bulk of the Southern Wasatch Mountains north-east of Nephi, Juab County, Utah. Along the west flank of Mount Nebo, the west half of the fold is trun- cated by the normal Wasatch Fault whereas the southern extension is terminated by the Nebo Overthrust. The remaining easterly portion of the anticline is highly dissected and is partially covered by thick sequences of easterly dipplng Late Cretaceous and Tertiary sedimentary and volcanic rocks. The Nebo Overthrust dips west to southwest at a low angle along the western margin of the mapped area, but it assumes an almost horizontal attitude near the center of the mountain range where overturned Paleozoic and Mesozoic rocks are in juxta- position with underlying Jurassic sandstones and shales. Slickensided surfaces in com- petent rocks near the main thrust zone, drag folds associated with minor thrusts in the Jurassic Arapien Shale, direction of overturning of the larger folds in the Jurassic Arapien Shale, and the trend of fold axes in the Arapien Shale indicate an eastward direction of movement for the upper plate of the Nebo Overthrust along a N.60-70" E. line. Minimum displacement is considered to be seven miles based on the occurrence of newly discovered fenstern containing critical stratigraphic units which are located north of the previously mapped position of the Nebo Overthrust. Formations within the' mapped area attest to at least four compressive phases and two episodes of normal faulting, and probably several more. as a consequence of the Cedar Hills, Laramide, and Basin and Range deformations. CONTENTS TEXT Indianola Group ........................ 70 Page Price River Formation ................ 71 Introduction ........................................ 56 Tertiary System ................................ 72 Previous' Work ................................ 56 Golden's Ranch Formation ........ 72 Present Work ................................ 56 Tertiarv-Ouaternarv Svstems f. ?), .... 73 Acknowledgments ................................ 58 Salt 'creek ~an~lomerate............ Quaternary System ............................. Stratigraphy ........................................ 58 Old Alluvium ............................ General Statement ............................ 58 Young Alluvium ........................ Pennsylvanian-Permian Systems .... 58 Igneous Rocks .................................... Oquirrh Formation .................... 58 Structure ................................................ Permian System ................................ 60 Folds ................................................ Kirkman Limestone .................... 60 Diamond Creek Sandstone ........ 60 Nebo anticline ............................ Folds in the Arapien Shale ........ Park City and Phosphoria Other Folds ................................ Formations ................................ 61 Thrust Faults .................................... Grandeur Member ........................ 61 Nebo Overthrust ........................ Meade Peak Phosphatic Foote's Canyon Thrust ................ Shale Tongue ............................ 62 Thrust Faults in the Franson Member ........................ 63 Arapien Shale ........................ Triassic System ................................ 63 Nature, Direction, and Displace- Woodside Shale ............................ 63 ment of Thrust Faults ............ Thaynes Limestone .................... 64 Normal Faults ................................ Ankareh Formation .................... 64 Wasatch Fault ............................ Jurassic System ................................ 66 Cow Hollow Fault .................... 82 Nugget Sandstone ........................ 66 Transverse Normal Faults ........ 83 Arapien Shale ............................ 67 Normal Faults in the Cretaceous Svstem ............................ 70 Ara~ien Shale ........................ 83 - 'A thesis submitted to the Faculty of the Department of Geology, Brigham Young University, in partial fulfillment of the requirements for the degree Master of Science. B. ALLEN BLACK CONTENTS Tectonism ......................................... 83 Nebo Overthrust relative to General Statement ............................ 83 other thrust faults In Utah ........ 57 Cedar Hills Orogeny ........................ 83 2. Generalized stratigraphic Laram~deOrogeny ............................ 84 column ........................................ 59 Montana Phase ............................ 84 3. Correlation of Arapien Shale .... 68 Paleocene Phase ............................ 85 ................................ Eocene Phase 85 plates ........................ following page 80 Basin and Range Deformation ........ 86 1. Nebo Overthrust Summary and Conclusions .................... 87 2. Thrust Faults Nebo Area References Cited ................................ 88 3. Folded Arap~enShale ILLUSTRATIONS 4. Faulted ~r&ienShale figure page 5. Geologic Map of Mount Nebo- 1. Location of thesis area and Salt Creek Vicinity ............ in back INTRODUCTION This report concerns details of two conspicuous structural elements of the Wasatch Mountains east and northeast of Nephi, Utah: the overturned Nebo anticline and the Nebo Overthrust. The Southern Wasatch Mountains in the vicinity of Mount Nebo and Salt Creek was mapped in detail with the primary objective of determining the nature, direction, and amount of displacement of the Nebo Overthrust. Study of the stratigraphic units -resulted in more detailed subdivision than was possible by Eardley's (1933a; 1934) initial work or by Hintze's (1962) photogeologic interpretation. Mapped tripartite subdivision of the Permian Park City and Phosphoria Formations consists of the Grandeur and Franson Members of the Park City Formation a,nd the intervening Meade Peak Phos- phatic Shale Tongue of the Phosphoria Formation. Threefold divisions in the Thaynes Limestone and Ankareh Formation were also recognized but not mapped. The mapped area is at the intersection of the Basin and Range, Middle Rocky Mountains, and Colorado Plateau physiogra hic provinces. It includes approximately 50 square miles immediately east a,ni northeast of Nephi, Juab County, Utah, and comprises parts of T. 12 and 13 S., R. 1 and 2 E. on the Nephi, Santaquin Peak, and Moroni quadrangles. The area is accessible by numerous dirt roads and trails which leave U.S. Highway 91, State Highway 11, and the Nebo Loop Road (Text-fig. 1). Previous Work The first general geologic investigations in the Southern Wasatch Mountains were by various directors of the early Territorial and Fortieth Parallel Survey. Loughlin (191 3) was the first to measure sections and map, in a reconnaissance fashion,