Geology of Piute County, Utah Item Type text; Dissertation-Reproduction (electronic); maps Authors Kennedy, Richard R. (Richard Ray) Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 04/10/2021 21:36:36 Link to Item http://hdl.handle.net/10150/565611 COPYRIGHT BY RICHARD RAY KENNEDY 1963 GEOLOGY OF PIUTE COUNTY, UTAH by Richard Kennedy A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 1963 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE I hereby recommend that this dissertation prepared under my direction by Richard R. Kennedy entitled "Geology of Piute County, Utah" be accepted as fulfilling the dissertation requirement of the degree of Doctor of Philosophy. /P/o^Z 3 Dissertation Director Date After inspection of the dissertation, the following members of the Final Examination Committee concur in its approval and recommend its acceptance:* ♦This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examina­ tion,, The inclusion of this sheet bound into the library copy of the dis­ sertation is evidence of satisfactory performance at the final examina­ tion. PLEASE NOTE: Figures and tables are not original copy. Some contain indistinct type. Filmed as received. UNIVERSITY MICROFILMS, INC STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of require­ ments for an advanced degree at The University of Arizona and is de­ posited in The University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in their judgment the proposed use of the material is in the interests of scholar­ ship. In all other instances, however, permission must be obtained from the author. SIGNED: GEOLOGY OF PIUTE COUNTY, UTAH by Richard R. Kennedy ABSTRACT Piute County is located in south-central Utah along the west­ ern margin of the Colorado Plateau, and is part of the physiographic subprovince known as the High Plateaus, Elevations range from 5,825 feet to 12,132 feet. The climate is semiarid. Sedimentary rocks, though of limited exposure, reveal an ex­ cellent section that ranges from Middle Pennsylvanian to late Tertiary- Quaternary in age. Total thickness of the exposed sedimentary rocks is about 6,200 feet. The Paleozoic rocks are largely carbonate with subordinate amounts of quartzite. Mesozoic rocks are predominantly sandstone, quartzite, and shale with lesser amounts of carbonate and conglomerate. Rocks from Cretaceous to Pliocene Time are generally absent. Late Tertiary-Quaternary sediments are mainly conglomerate, fanglomerate, and alluvial debris. The area is the site of an extensive accumulation of late ii Tertiary volcanic rocks. Extensive flows are intercalated with more abundant pyroclastic material of regional extent, Six major groups of the igneous rocks are recognized. From oldest to youngest, these groups are: (1) Bullion Canyon Group, consisting of latites, andesites, flows, and breccias; (2) Monzonitic intrusions; (3) Dry Hollow-Roger Park Group, consisting of latite, tuff, and basaltic breccia; (4) Granite intrusion; (5) Mount Belknap Group, consisting of rhyolitic flows, tuffs, and breccias; and (6) Basalt flows. Total thickness of these rocks is variable, but probably exceeds 10,000 feet. Based on petrologic and petrographic observations, the. Bullion Canyon Group and the Mount Belknap Group are each subdivided into three subgroups. The Bullion Canyon subgroups are apparently of re­ gional extent, and are useful as reference planes for subsequent geologic events. Fluidization, air fall, and, locally, water have been responsi­ ble for the wide areal distribution of these rocks. Field relationships and absolute age dating indicate that vol- canism began about middle Eocene and lasted to late Pliocene or early Pleistocene time. - C.I.P.W. and Niggli calculations are applied to available chemical analyses of the igneous rocks. The two methods yield com­ plimentary results. The rocks are all saturated with respect to silica, in the norm. There is an equivalence of the alkalies throughout. The iii rocks are relatively poor in calcium. There are gross chemical dif­ ferences between the various rock groups, however, there is a more or less regular variation from the older to the younger rocks; and with the exception of late basalt, the igneous rocks exhibit chemical consan­ guinity, ■' . The area exhibits structural characteristics that are related to both the Colorado Plateau and the Basin and Range, However, the struc­ ture is relatively simple in that complex folding and thrusting are gen­ erally absent. Structures with north trends are most pronounced; how­ ever, northwest, northeast, and east trends are present, > Faults are the most noteworthy structural features of the area. Relatively linear north-south valley and mountain blocks bounded on both east and west by major faults are characteristic. The major period of faulting probably took place in late Pliocene Time, Two anticlines and two synclines with northwest trends con­ stitute the major folds of the area. Rocks of the area exhibit a widespread and variable suite of alteration minerals, some of which are characteristically associated with ore mineralization. The several different rock types respond dif­ ferently to the alteration processes; but, in general, the older igneous rocks are more highly altered than the younger igneous rocks. The alteration has been largely accomplished through fumarolic-hydrothermal iv action. Mines of Piute County have produced about $19, 000, 000 in min­ eral products, ranging from alunite to uranium. The mineral deposits consist of vein and replacement types. The deposits are thought to have been formed by ascending magmatic waters rich in sulfate, bi­ carbonate, potassic and halogen,components. Relatively low tempera­ ture and low pressure probably prevailed during ore deposition. Open- space filling has been important as a mode of ore deposition. Available absolute age dates indicate that the ore mineraliza- ■ . tion took place during late Miocene and early Pliocene (13-11 m, y .). TABLE OF CONTENTS Page CHAPTER I—INTRODUCTION.................................................... 1 General Statement.............. Location and Accessibility .. CO I j Purpose and Scope........... Q CD I>* CO • Field and Laboratory Studies Acknowledgments ; ............ Previous Work ...................... CHAPTER H—GEOGRAPHY................................................... 10 Climate .................... .’............................................................... 10 •Soils .. ’. ................ 11 Vegetation ....* ..........*........................... .............................;. 11 Physiography .. .............. 12 * CHAPTER HI—SEDIMENTARY ROCKS..............'....................... 21 General Statement ------ ; ...............................................:... 21 Pennsylvanian System .............................................................. 22 Callville Limestone.......... .*................. ......................... 22 Oquirrh Formation .......................................................... 24 • • Permian System ....................................................................... 27 Toroweap Form ation........................................................ 27 Kaibab Limestone ............................................................ 28 Triassic System ........................................... .... .•.................... 29 . Moenkopi Form ation........................................................ 30 Shinarump Conglomerate................................................ 33 Chinle Form ation.............................................................. 34 Triassic - Jurassic and Jurassic System ....................... 35 vi Navajo Formation ...... Jurassic S ystem .................... Winsor Formation ........ Cretaceous(?) System Tushar Conglomerate . Tertiary-Quaternary System Sevier River Formation Quaternary System .............. CHAPTER IV—METAMORPHIC ROCKS CHAPTER V—IGNEOUS ROCKS Extrusive Rocks.............. Bullion Canyon Group Lower Subgroup Middle Subgroup Upper Subgroup . Roger Park-Dry Hollow Group Roger Park Formation Dry Hollow Formation » Mount Belknap Group ...; Red Subgroup........ Gray Subgroup.......... Porphyritic Subgroup Joe Lott Tuff.............. Olivine B asalt.................. Page Intrusive R o c k s................................................................................. 105 Age ....................... 113 Chemical Character of the Igneous Rocks ................................ 118 Interpretation ............................; ................ .......... .. 132 Summary .............................................. '...................« . / .......... .. 140 CHAPTER VI—STRUCTURAL GEOLOGY ......................