Structural Geology of the Hawthorne and Tonopah Quadrangles, Nevada By HENRY G. FERGUSON and SIEMON W. MULLER GEOLOGICAL SURVEY PROFESSIONAL PAPER 216 A study of the geology of pre-Tertiary rocks and Jurassic diastrophism UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : J949 UNITED STATES DEPARTMENT OF THE INTERIOR J. A. Krug, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $2.00 (paper cover) CONTENTS Page Page Abstract---__________----------_--_-_--_------_--_- 1 Areal geology Continued Introduction _________---_____-_____-____-_____-_-__ 1 Garfield Hills . ___________..___..._...______ 16 Location _________-__-_--_-___-______----__----_ 1 Rocks exposed. ____________^____________ 16 Accessibility ___________________________________ 2 Excelsior formation. _ _________________ 16 Previous investigations__________________________ 3 Luning formation_____________-___-____ 16 Field work and acknowledgments.________________ 3 Gabbs and Sunrise formations. __-__-__- 18 General geology. ____-_____-_____-_-____--___----__ 4 Dunlap formation. _. _________________ 18 Outline of stratigraphy__._______._______________ 4 Intrusive rocks____________-_____---_._ 19 Distribution of the pre-Tertiary rocks.________ 4 Structure- _----_---_-------__-----------_ 19 Paleozoic rocks.______:.__________---___----_ 4 Pre-Jurassic folding______ ______________ 19 Mesozoic rocks._______-___--____-_-_____-__ 4 Early folding of Luning formation. __ __. 19 Triassic system.________________________ 4 Garfield Flat thrust ____________ _ .-_ 20 Candelaria formation (Lower Triassic) _ 4 Uplift and change in trend of folding. _ _ _ 23 Grantsville formation (Middle Trias­ Marble Quarry thrust. _________________ 23 sic) ______-___________--_-__-_--- 4 Ashby thrust.- .__ ____ ______________ 23 Excelsior formation (Middle Triassic)__ 4 McGee thrust---.--------.----.------- 24 Luning formation (Upper Triassic)-___ 5 Pamlico thrust. _______________________ 24 Gabbs formation (Upper Triassic) 5 Gillis thrust _ __-______-__----_----___ 24 Jurassic system.._______________________ 5 Later normal faults. ___________________ 25 Sunrise formation (Lower Jurassic)____ 5 Gabbs Valley Range. __ ________ _ ._--__--_-._ 25 Dunlap formation (Lower Jurassic) 6 Rocks exposed __ ________________________ 25 Intrusive rocks (Jurassic ?)_ ___-__-_--__ 6 25 Tertiary rocks..______________-____--__---_- 7 Folding prior to thrusting _ _____________ 26 Diastrophic history_____________________________ 7 Sunrise Flat thrust_.__ _ -_-_-___-__--__ 26 Pre-Jurassic deformation___________________ 7 New York Canyon thrust _ _____________ 26 Pre-Permian folding___________________ 7 Later folding and tilting... ______________ 29 Unconformity at base of Lower Triassic-__ 8 Pilot Mountains- . _____________--__-_---________ 29 Unconformity at base of Middle Triassic. __ 8 Rocks exposed__-_______________.-__________ 29 Pre-Upper Triassic folding _______________ 8 Excelsior formation. _ ___________________ 29 Development of the Luning Embayrnent___ 8 Luning formation.. _ ____________________ 29 Jurassic orogeny.____._________..__._._._-__ 9 Sunrise formation.. _ ____________________ 30 Sequence of events_____--___----_----__- 9 Dunlap formation __ ___________________ 30 Early Jurassic warping and Dunlap Intrusive rocks-___-------------_-----._ 30 sedimentation ____________________ Structure __________________________________ 30 Localized folding and thrusting and Pre-Jurassic folding_________. ___________ 31 development of structural troughs _ _ Deposition of the Dunlap sediments_-_____ 31 Folding and thrusting in the Luning Early Jurassic folding and thrusting __ ___ 31 Embayment. _ __________________ 10 Outline of structural development __ . 31 Large-scale thrusting.____---__.--___ 12 Mac thrust-____----_--_---_----._- 32 Deformation of the marginal Paleo­ Spearmint thrust. .____-_____-_.____ 33 zoic rocks..._____________________ 12 North-west thrust______________.____ 33 Other faults__-_______----_------_ 13 Dunlap Canyon thrust- _--_-_-____-_ 34 Intrusion of granitic rocks.__________ 13 South Fork thrust..... __ _ _._. _ 35 Date of diastrophism..._________________ 13 Later thrusting________. ________________ 35 Post-Jurassic structure____________-_-_----__ 13 Cinnabar Canyon thrust. __ ___-__._.. 35 Thrusting.._ ___.________.__-_---_-----_ 13 West Ridge thrust_-_____--__-.____- 36 Flaw in Soda Spring Valley ______________ 14 East Ridge thrust __ ______________ 36 Basin Range faulting________----_---____ 14 Normal faulting. _______________________ 37 Areal geology.______---__-___-_.__-____----_---__-_ 14 Cedar Mountain_-__-_-___--_--_-______-________ 38 Wassuk Range._____-______________-----___--__ 15 Rocks exposed... _ _________________________ 38 Gillis Range____---________________--------___ 15 Structure __________________________________ 38 Rocks exposed .________________________ 15 Areas of Mesozoic rocks east of Cedar Mountain. ___ 39 Structure. ____-______-_________----_-_--__ 16 Paradise Range _ ---__-__-__--____-_--_----____ 39 Gillis thrust _._____-________--_-_-_-___ 16 Rocks exposed_..___.____. ___.___.__.._______ 39 Tertiary normal faults.__________________ 16 Permian (?) volcanic and sedimentary rocks- 39 IV CONTENTS Areal geology Continued Page Areal geology Continued Page Paradise Range Continued Excelsior Mountains Continued Mcsozoic rocks______________________ 40 Structure._-__-____________--__. 44 Excelsior formation(?)________ 40 Pre-Jurassic folding._________ 45 Luning formation____________ 40 Jurassic folding_____________. 45 Gabbs and Sunrise formations. 40 Later faulting..______._____. 45 Dunlap formation_____________ 40 Miller Mountain and Candelaria Hills.. 45 Intrusive rocks__________________ 40 Rocks exposed_-__---__----_-_-_. 45 Structure-____-_-_-___-_-__-_-_____. 40 Cambrian sedimentary rocks.. 45 Paradise thrust._________________ 40 Ordovician sedimentary rocks. 45 South thrust.___________________ 40 Permian sedimentary rocks _ _. 45 Shoshone Mountains.____________________ 40 Candelaria formation _ ________ 46 Rocks exposed.______________________ 41 Excelsior (?) formation_______. 46 PermianC?) rocks..___-.__.-_----_ 41 Intrusive rocks______________ 46 Sedimentary rocks.__________ 41 Structure _______________________ 47 Volcanic rocks.______________ 41 Pre-Permian folding__ ._____. 47 Mesozoic rocks._________________ 41 Monte Cristo thrust.____---_. 47 Grantsville formation._______ 41 Later faulting-.________--__. 48 Luning formation ____________ 41 Monte Cristo Range.___-____-_._.-_. 48 Gabbs and Sunrise formations. 41 Rocks exposed___________________ 48 Dunlap formation.__________ 41 Monte Cristo thrust_-_-._-__--_. 48 Intrusive rocks._________________ 41 Lone Mountain______________________ 48 Structure-______________-__-_-_-_--_ 41 San Antonio Mountains. _____________ 48 Pre-Jurassic folding._____________ 42 Toquima Range. _-_________.-__.._. 51 Shoshone thrust.________________ 42 Rocks exposed...._______________ 51 Later faulting._______._--______- 43 Structure _______________________ 51 Excelsior Mountains.____________________ 44 Toyabe Range_______________________ 52 Rocks exposed____________-.--._-___. 44 Rocks exposed______.____________ 52 Excelsior formation ______________ 44 Structure._ __--____-______-__-_. 53 Dunlap formation.___________ __. 44 Index _________-:._.-_-__--__-__---_.--. 55 Intrusive rocks.________________ 44 ILLUSTRATIONS Page PLATE 1. Geologic map of Hawthorne and Tonopah quadrangles, Nevada_____-__-_-_-__-____-____--_-_--_________ In pocket 2. Geologic map and sections of parts of the Gabbs Valley Range, Garfield Hills, Pilot Mountains, and Excelsior Mountains-_---._-_______-______________________-____--__--__-__-__-____-----_--_-----_-_--__-_ In pocket 3. Diagrammatic sections in northwestern part of Pilot Mountains-_______________________________________ In pocket 4. A, Limestone conglomerate of Dunlap formation, unconformable on limestone of Luning formation; B, Coarse fan- glomerate of limestone boulders in Dunlap formation, overlying limestone member of Luning formation; C, Basal conglomerate of Dunlap formation resting on slate member of Luning formation; D, West front of Gabbs Valley. Range......____-_--__--___ _____ ___._.__________.___-_.___-_--_--..____---_.._--__..._____ 26 5. Geologic map and sections of area near mouth of New York Canyon, Gabbs Valley Range. ___________ _____ In pocket < 6. A, "Thrust conglomerate" on ridge south of Sunrise Flat, Gabbs Valley Range; B, Interbedded chert with tuffa- ceous slate and sandstone in Excelsior formation; C, Upper part of Mac Canyon showing bend in Mac thrust; D, Hill between Mac and Spearmint Canyons, west front of Pilot Mountains_______________________________ 42 7. Geologic map and sections of northwestern part of Pilot Mountains_____________________________________ In pocket 8. Isometric projection showing superposed thrust plates and individual formations, northwestern Pilot Mountains.In pocket 9. A, Corrugations in Mac thrust at bend, upper part of Mac Canyon; B, "Thrust conglomerate" in fissures in dolo­ mite of overturned upper plate of Mac thrust; C, Brecciated dolomite in upper unit of Luning formation, between Mac and Spearmint thrusts; D, North wall of Spearmint Canyon, Pilot Mountains__________________________ 42 10. A, Intricately contorted sandstone of Dunlap formation below Spearmint thrust, Mac Canyon, Pilot Mountains; B, Hill north of Mac Canyon showing