U.S. Department of the Interior U.S. Geological Survey The Nature and Timing of Tectonism in the Western Facies Terrane of Nevada and California—An Outline of Evidence and Interpretations Derived From Geologic Maps of Key Areas U.S. Geological Survey Professional Paper 1592 The Nature and Timing of Tectonism in the Western Facies Terrane of Nevada and California—An Outline of Evidence and Interpretations Derived From Geologic Maps of Key Areas By Keith B. Ketner T OF U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1592 EN TH TM E R I A N P T E E D R . I O S . R U M 9 A 8 4 R C H 3, 1 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1998 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Mark Schaefer, Acting Director For sale by U.S. Geological Survey, Information Services Box 25286, Federal Center Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Library of Congress Cataloging-in-Publication Data Ketner, Keith Brindley, 1921– The nature and timing of tectonism in the western facies terrane of Nevada and California : an outline of evidence and interpretations derived from geologic maps of key areas / by Keith B. Ketner. p. cm. — (U.S. Geological Survey professional paper ; 1592) Includes bibliographical references. 1. Geology, Structural—Nevada. 2. Geology, Structural—California. I. Title. II. Series. QE627.5.N3K47 1998 551.8′09793—dc21 97-44447 CIP CONTENTS Abstract........................................................................................................................... 1 Introduction ...................................................................................................................1 Definitions of Terms ...................................................................................................... 2 Significant Features of Maps in Key Areas of Nevada and California ......................... 3 Rowland Area ........................................................................................................ 3 Bull Run Mountains ............................................................................................... 5 Mountain City Area................................................................................................ 6 Northern Independence Mountains ....................................................................... 7 Southern Independence Mountains ....................................................................... 8 Mount Ichabod Area............................................................................................... 8 Northern Adobe Range and Peko Hills .................................................................. 8 Elko Hills................................................................................................................ 9 Piñon Range............................................................................................................ 9 Cortez Mountains ................................................................................................... 10 Northern Shoshone Range...................................................................................... 10 Edna Mountain ....................................................................................................... 11 Osgood Mountains and Hot Springs Range ........................................................... 11 Battle Mountain ...................................................................................................... 12 Sonoma Range........................................................................................................ 12 East Range .............................................................................................................. 12 Southern Toyabe Range.......................................................................................... 14 Emigrant Pass and Railroad Pass............................................................................ 14 Monte Cristo Range and Candelaria Hills.............................................................. 15 Convict Lake........................................................................................................... 15 Pilot Knob Valley and El Paso Mountains ............................................................. 15 Conclusions .................................................................................................................... 16 References Cited............................................................................................................. 17 FIGURE 1. Index map showing localities discussed in text ......................................................................................................... 3 III IV CONTENTS TABLES 1. Locations of exposures showing Ordovician western facies strata conformably overlying thick sequences of miogeoclinal units ....................................................................................................................... 4 2. Locations of exposures showing Upper Devonian and Mississippian strata of the overlap assemblage disconformably overlying western facies units ...................................................................................... 4 3. Locations of exposures of Middle Pennsylvanian to Permian strata of the overlap assemblage disconformably or unconformably overlying older parts of the overlap assemblage, western facies units, and miogeoclinal strata underlying the western facies assemblage....................................................... 5 The Nature and Timing of Tectonism in the Western Facies Terrane of Nevada and California—An Outline of Evidence and Interpretations Derived From Geologic Maps of Key Areas By Keith B. Ketner ABSTRACT This report is essentially a critique of selected maps (fig. 1), most of which have been published since 1958 when cur- Along the outer miogeocline of Nevada and southern rently accepted concepts of the tectonic history of the region California, lower Paleozoic siliceous sediments and basalt were first formulated by R.J. Roberts and others. The purpose flows, known collectively as the western facies rocks or the of this report is to highlight the most significant stratigraphic western assemblage, accumulated in deep water concor- and structural relations displayed on these geologic maps, dantly on a thick substrate of Proterozoic to Upper Cambrian stressing the significance of the maps individually and col- shallow-water to deep-water terrigenous sediments. In the lectively for the tectonic history of the region. mid-Frasnian of Late Devonian time, the western facies ter- The age ranges of several stratigraphic units shown on rane emerged and was deeply eroded. Structural evidence many of the maps are no longer valid, and the maps are that this event, the Antler orogeny, involved intense folding unlikely to be revised in the near future. Accumulating pale- and thrust faulting is notably scarce. Starting in late Fras- ontological data has led to improved stratigraphic concepts nian, siliceous sediments and intercalated basalt flows accu- and therefore made possible an improved understanding of mulated disconformably on deeply depressed parts of the the tectonic history. A principal aim of this report is to make western assemblage forming the lower strata of the Havallah the revised ages of stratigraphic units more widely known. and equivalent sequences of the overlap assemblage. In Mid- Existing maps represent tremendous physical and men- dle Pennsylvanian the entire stack was moderately tal effort by geologists over the last four or five decades, but deformed, elevated, and again deeply eroded. Starting in unfortunately, the tectonic interpretations in many cases later Middle Pennsylvanian, the western assemblage and seem to have been driven more by ideology than by the overlying units subsided and marine sediments accumulated observed structural relations. As a result, interpretations are through the Permian over broad areas. Beginning in the commonly at variance with the map evidence as noted in the Jurassic and ending in the Eocene, the entire region was following pages. strongly folded and thrust faulted. Almost all of the intense This report necessarily demands much from the reader. folding and thrust faulting of Proterozoic to Permian strata For maximum benefit from the discussions that follow, the dates from the Jurassic to Eocene interval. If this tectonic reader should examine the principal geologic maps to which history is valid, then the genesis of the Antler orogeny is reference is made. Brief summaries of pertinent aspects of reduced to a question of vertical tectonics. The presence of stratigraphy and structure are presented, but to duplicate basaltic flows at all levels in the Paleozoic column suggests herein parts of the many geologic maps to which reference is a persistently tensional stress regime both before and after made, or to describe in detail the stratigraphy and structure of the Antler orogeny. Pre-Jurassic contraction involving sub- each map area, would be impractical. Simplified sketches of duction and collision with island arcs is not indicated or the maps would be useless; the message is in the details. required, but the ultimate origin of Paleozoic tectonism Tables 1–3 give locations of some of the more critical remains unclear. exposures. Acknowledgments. This paper benefitted greatly from INTRODUCTION reviews by N.J. Silberling