The Roberts Mountains Formation, a regional stratigraphic study with emphasis on rugose coral distribution GEOLOGICAL SURVEY PROFESSIONAL PAPER 973 The Roberts Mountains Forn1ation, a regional stratigraphic study with emphasis on rugose coral distribution B1' CHARLES W. MERRIAM and EowiN H. McKEE Tl 7ith a section on Conodonts, b_rv JOHN W. HUDDLE GEOLOGICAL SURVEY PROFESSIONAL PAPER 973 A study of stratigraph_v, facies, and coral distribution in the 1niddle Paleozoic (Silurian and De·uonian) limestone belt of the central and southwestern Great Basin UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1976 UNITED STATES DEPARTMENT OF THE INTERIOR THOMAS S. KLEPPE, Serretm)' GEOLOGICAL SURVEY V. E. :McKelvey, Director Library of Congress Cataloging in Publication Data Merriam, Charles Warren, 1905- The Roberts Mountains Formation. (Geological Survey Professional Paper 973) Bibliography: p. 43-45. Includes index. Supt. of Docs. no.: I 19.16:973 1. Geology, Stratigraphic-Silurian. 2. Geology, Stratigraphic-Devonian. 3. Rugosa. 4. Geology-Nevada. 5. Geology­ California. I. McKee, Edwin H., joint author. II. Huddle, John Warfield, 1907- joint author. III. Title. IV. Series: United States Geological Survey Professional Paper 973. QE66l.M45 551. 7'3'0979 76-608307 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-02893-0 CONTENTS Page Page i\bstract -------------------------------------------------- 1 Roberts Mountains Formation of the northern Introduction ---------------------------------------------- 1 Toquima Range-Continued Purpose and scope of investigation _____________________ _ 2 Ikes Canyon window i\cknowledgments _____________________________________ _ 2 Mill Canyon sequence------------------------------ 22 History of investigation _______________________________ _ 3 August Canyon sequence -------------------------- 23 Paleontologic zoning of the Great Basin Silurian and Lower Northumberland window ------------------------------ 23 Devonian _______________________________________________ _ 4 Roberts Mountains Formation in the Toiyabe Range __________ 23 Scarcity of reefs or bioherms in the Roberts Mountains For- Callaghan window ------------------------------------ 24 mation _________________________________________________ _ 4 Dry Creek area---------------------------------------- 24 Distribution of Great Basin Silurian limestone and dolomite Point of Rocks and Straight Canyon ____________________ 24 belts and the regional dolomite problem _________________ _ 6 Pablo Canyon area ------------------------------------ 25 Geographic distribution of Silurian limestones _____________ _ 7 Roberts Mountains Formation in the Shoshone Mountains ____ 25 Roberts Mountains Formation of the Roberts Mountains, Nev __ 7 Silurian and Lower Devonian limestones of the northern Inyo Type section _________________________________________ _ 9 Mountains, Calif __ _ __ _ __ ___ ____ ___ __ ____ __ __ __ __ __ __ 25 Stratigraphic relations to underlying and overlying Mazourka Canyon ------------------------------------ 25 formations -------------------------------------- 9 Vaughn Gulch Limestone -------------------------- 25 Facies changes from limestone to dolomite __________ 10 Physical stratigraphy -------------------------- 25 Stratigraphic paleontology of the type section____________ 10 Stratigraphic paleontology ______________________ 26 Fossils of units 1 and 2 ____________________________ 10 i\ge ------------------------------------------ 27 Fossils of unit 3 ___________________________________ _ 10 Sunday Canyon Formation ------------------------ 28 Age of the Roberts Mountains Formation of the type i\ge ________________________________ ------____ 28 section------------------------------------------ 10 The Silurian-Devonian boundary in central Nevada __________ 28 Roberts Mountains Formation of the northern Simpson Park i\n appraisal of stratigraphic and age values of rugose corals and Mountains ------------------------------------------ 11 associated fossils, with description of previously unknown Geologic setting________________________________________ 11 key Rugosa ____ -------------------------------------- 29 Coal Canyon area ______________________________________ 11 Rugose corals of special stratigraphic value ______________ 29 Coal Canyon fault zone ____________________________ 11 Silurian nondissepimented Rugosa------------------ 29 Physical stratigraphy of the Pine Hill section________ 12 Family Kodonophyllidae ________________________ 29 Stratigraphic paleontology and age of Roberts Moun- Subfamily Kodonophyllinae Merriam ________ 30 tains Formation at Pine HilL_____________________ 13 Subfamily Mycophyllinae Hill ______________ 30 Fossils collected within the Coal Canyon fault zone __ 14 Family Streptelasmatidae Nicholson __________ 30 Physical stratigraphy of the Pyramid Hill section ____ 14 Family Stauriidae Edwards and Haime __________ 31 Problem ofthe Silurian-Devonian boundary at Pyramid Family Tryplasmatidae Etheridge ______________ 31 Hill __ __ _ __ _ __ _ _ ___ __ _ _ _ __ __ ____ __ __ _ _ ____ __ __ __ 15 Family Pycnostylidae Stumm __________________ 31 Roberts Mountains Formation, Tuscarora Mountains _______ _ 15 Compact cerioid Pycnostylidae of Silurian limestone Physical stratigraphy ofthe Bootstrap Hill section _____ _ 16 facies ------------------------------------------ 32 Stratigraphic paleontology of the Bootstrap Hill section __ 16 Dissepimented Rugosa of the Great Basin Silurian i\ge of the Roberts Mountains Formation at Bootstrap limestone facies ______________________________ 32 Hill __ __ _ _ __ __ _ _ __ __ _ _ ______ __ __ __ __ __ ____ __ __ ____ __ 17 Family Spongophyllidae Dybowski ______________ 32 Roberts Mountains Formation of the northern Monitor Range 18 Family Endophyllidae Torley __________________ 34 Physical stratigraphy _________________________________ _ 18 Family Chonophyllidae Holmes ________________ 36 Stratigraphic paleontology and age of the Roberts Moun- Family Kyphophyllidae Wedekind ______________ 36 tains Formation at Copenhagen Canyon ______________ 18 Family Calostylidae Roemer-------------------- 37 Roberts Mountains Formation at Brock Canyon, Monitor Family Lykophyllidae __________________________ 37 Range -------------------------------------------------- 19 Fossils associated with rugose corals in Great Basin Silu- Roberts Mountains Formation at Dobbin Summit, Monitor rian limestones __ ____ ___ ___ ___ __ _ ____ __ __ ___ ___ __ 37 Range -------------------------------------------------- 19 Dasycladacean algae as indicators of the Silurian ____ 38 Roberts Mountains Formation at Bare Mountain ____________ 20 Conodonts of the Roberts Mountains Formation by Roberts Mountains Formation of the northern Toquima John W. Huddle -------------------------------- 38 Range -------------------------------------------------­ 20 Locality register of major fossil localities in the Roberts Moun­ Petes Canyon window---------------------------------­ 22 tains Formation and correlative strata -------------------- 39 Ikes Canyon window ---------------------------------- 22 Selected references ____________________________ ------------ 43 June Canyon sequence ---------------------------- 22 Index ---~------------------------------------------------ 47 III IV CONTENTS ILLUSTRATIONS [Plates follow index] PLATE 1. Stylopleura and Pycnostylus. 2. Stylopleura and Pycnostylus. 3. Fletcheria and Tryplasma. 4. Mucophyllum and Kodonophyllum. 5. Tonkinaria, Kyphophyllum, Kodonophyllum, and Brachyelasma. 6. Spongophyllum, Carlinastraea, and Australophyllum. 7. Carlinastraea, Chonophyllum, and Calostylis? 8. Carlinastraea and A ustralophyllum. 9. Kyphophyllum and Chonophyllum. 10. Verticillopora, Cladopora, Favosites, Kyphophyllum, Ketophyllum, and Hercynella. 11. Verticillopora, Kozlowskiellina, H omoeospira, Dicoelosia, Plectatrypa?, and Gypidula. 12. Coelospira, Fardenia, Kozlowskiellina, Conchidium, Cyathophylloides, Brachyelasma, and lycophyllid. Page FIGURE 1. Index map of part of Great Basin showing distribution of the Roberts Mountains Formation and correlative formations in the intermediate limestone belt in Nevada and California -------------------------------------------------------- 8 2. Geologic map of the Coal Canyon area, northern Simpson Park Mountains _____________________________________________ 12 3. Sketch map of the northern Toquima Range showing Paleozoic sequences that contain Silurian rock in separate thrust sheets __ 21 TABLES Page TABLE 1. Characteristic fossils of the Great Basin Silurian coral zones --------------------------------------------------------- 5 2. Occurrence chart of conodont species collected from Silurian and Lower Devonian formations in central Nevada __________ 40 THE ROBERTS MOUNTAINS FORMATION, A REGIONAL STRATIGRAPHIC STUDY WITH EMPHASIS ON RUGOSE CORAL DISTRIBUTION By CHARLES W. MERRIAM and EDWIN H. McKEE ABSTRACT limestones, mostly argillaceous, and some dolomitic A large part ofthe Silurian and the base of the Devonian Systems marine strata occupying a northerly oriented linear are represented in the central and southwestern Great Basin by belt within the central and west-central Great Basin. limestones of the Roberts Mountains and the Vaughn Gulch Forma­ Diverse fossil assemblages from many localities indi­ tions. In Silurian time the Great Basin region was inundated by northward-trending shelf seaways of three wide facies belts: the cate that in the time-stratigraphic sense