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A Graptolite Zone Reference Section Ordovician and Silurian 4 Graptolite Succession in the Trail Creek Area, Central Idaho A Graptolite Zone Reference Section GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 4 -t Ordovician and Silurian Graptolite Succession in the Trail Creek Area, Central Idaho A Graptolite Zone Reference Section By CLAIRE CARTER and MICHAEL CHURKIN, JR. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 UNITED STATES GOVERNMENT PRINTING OFF ICE, WASHINGTON: 1977 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Carter, Claire. Ordovician and Silurian graptolite succession in the Trail Creek area, central Idaho-a graptolite zone reference section. (Geological Survey Professional Paper 1020) Bibliography: p. 32-33. Supt. of Docs. No.: I 19.16:1020 1. Graptolites. 2. Paleontology--Ordovician. 3. Paleontology-Silurian. 4. Paleontology-Idaho- Custer Co. 5. Paleontology-Idaho-Blaine Co. I. Churkin, Michael, 1932- joint author. III. Title. III. Series: United States Geological Survey Professional Paper 1020. QE840.5.C37 566 76-608341 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-02982-1 CONTENTS Page Page Abstract.................................................................................................... 1 Systematic descriptions Continued Introduction ............................................................................................ 1 Class Graptolithina Continued Geologic setting...................................................................................... 3 Order Graptoloidea Continued Lithology and structure ...................................................................... 3 Family Dicranograptidae .......................................... 17 Graptolite zones and their correlation .......................................... 5 Genus Dicranograptus ........................................ 17 Lower Ordovician Series ............................................................ 5 Genus Dicellograptus .......................................... 18 Middle Ordovician Series .......................................................... 10 Family Glossograptidae.............................................. 21 Upper Ordovician Series ............................................................ 12 Genus Glossograptus .......................................... 21 Silurian System.............................................................................. 13 Family Cryptograptidae ............................................ 21 Systematic descriptions...................................................................... 13 Genus Cryptograptus .......................................... 21 Class Graptolithina...................................................................... 13 Family Diplograptidae............................................... 22 Order Graptoloidea .............................................................. 13 Genus Dip ograptus ............................................ 22 Family Dichograptidae .............................................. 13 Genus Climacograptus ........................................ 22 Genus Loganograptus.......................................... 13 Genus Glyptograptus .......................................... 24 Genus Goniograptus ............................................ 13 Genus Orthograptus ............................................ 25 Genus Tetragraptus .............................................. 14 Genus Petalograptus ............................................ 27 Genus Phyllograptus............................................ 14 Genus Pseudoclimacograptus .......................... 27 Genus Didymograptus ........................................ 15 Family Lasiograptidae................................................ 28 Genus Isograptus .................................................. 15 Genus Neurograptus ............................................ 28 Genus Maeandrograptus .................................... 16 Family Retiolitidae ..................................................... 28 Family Corynoididae .................................................. 16 Genus Orthoretioiites .......................................... 28 Genus Cornyoides ................................................ 16 Family Monograptidae................................................ 28 Family Nemagraptidae .............................................. 16 Genus Monograptus ............................................ 28 Genus Leptograptus ............................................ 16 Family Cyrtograptidae... .......................................... 30 Genus Pleurograptus ............................................ 17 Genus Cyrtograptus ............................................ 30 References cited...................................................................................... 32 Index ...... .............................................................................................. 35 ILLUSTRATIONS [Plates follow index] Page PLATE Loganograptus, Phyllograptus, Didymograptus, Isograptus, and Tetragraptus. Leptograptus, Dicellograptus, Pleurograptus, Dicranograptus, Isograptus, and Corynoides. Dicellograptus, Glossograptus, Cryptograptus, Pseudoclimacograptus, Diplograptus, Neurograptus, and Petalograptus. Climacograptus, Orthograptus, and Orthoretioiites. Glyptograptus, Monograptus, and Cyrtograptus. Cyrtograptus, Dicellograptus, and Gonioeraptus Sketch of Maeandrograptus, Leptograptus, Dicranograptus, Climacograptus, and Cyrtograptus. FIGURE 1. Map showing location of measured sections .......................................................................... .......................................................... 2 2. Stratigraphic column of the upper plate of the Park Creek thrust in the Trail Creek section, showing zonal sequence and location of graptolite collections......................................................................................................... .. 4 Chart showing correlation of graptolite sequences in western North America, Great Britain, Australia and the U.S.S.R. ............................................................................... 6 Stratigraphic column of the Little Fall Creek section, showing zonal sequence and location of graptolite collections..................................... ..... .. .... .. ...... .......... .. ...... ........................... 9 in IV CONTENTS TABLES Page TABLE 1. Distribution and zonal ranges of Ordovician graptolite genera and species in the lower part of the Phi Kappa Formation, Trail Creek section ........................................................................................................................................................... 8 2. Distribution and zonal ranges of Ordovician graptolite genera and species in the Phi Kappa Formation, Little Fall Creek section......................................................................................................................................................................... 9 3. Distribution and zonal ranges of Ordovician graptolite genera and species in the upper part of the Phi Kappa Formation, Trail Creek section ............................................................................................................................................................ 10 4. Distribution and zonal ranges of Silurian graptolite genera and species in the Phi Kappa Formation, Trail Creek section.................................................................................................................................................................................. 13 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION IN THE TRAIL CREEK AREA, CENTRAL IDAHO A GRAPTOLITE ZONE REFERENCE SECTION By CLAIRE CARTER and MICHAEL CHLRKIX, JR. ABSTRACT faunas described prior to 1963 were not fitted into a The graptolite-bearing sequence in the vicinity of Trail Creek, Idaho, consists of an unusually large number of zones virtually local stratigraphic succession of graptolite faunas. continuously exposed in a homoclinal section of siliceous shale. Ross and Berry (1963) had to use the graptolite Eight Ordovician zones have been distinguished in the Phi Kappa succession of the Marathon region, Texas (Berry, Formation. These include the Early Ordovician Zones of Didymo- 1960), as a standard to compare and correlate the graptus protobifidus and Isograptus, the Middle Ordovician zones isolated graptolite faunas of the Basin and Range of Glossograptus hincksii, Nemagraptus, Climacograptus bi- cornis, and Climacograptus tubuliferus, and the Late Ordovician province "because *** no readily zonable succession Zones of Pleurograptus linearis and Dicellograptus ornatus. The has yet been found in the Great Basin" (Ross and Early and Middle Silurian Zones of Monograptus convolutus and Berry, 1963, p. 68). Cyrtograptus overlie this Ordovician succession. The relative Later, in the vicinity of Trail Creek, Custer and completeness of the graptolite succession from late Early Ordo­ Blaine Counties, central Idaho (fig. 1), an unusually vician through Late Ordovician becomes apparent when it is compared to other known graptolitic sequences of western North continuous stratigraphic section of graptolitic shale America. Thus it is a potentially useful reference section for at was discovered (Churkin, 1963), and a preliminary least the southern part of the North American Cordillera.
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