Lithostratigraphy, Microlithofacies, And
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Lithostratigraphy, Microlithofacies, and Conodont Biostratigraphy and Biofacies of the Wahoo Limestone (Carboniferous), Eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 j^^^fe^i^^t%t^^S%^A^tK-^^ ^.3lF Cover: Angular unconformity separating steeply dipping pre-Mississippian rocks from gently dipping carbonate rocks of the Lisburne Group near Sunset Pass, eastern Sadlerochit Mountains, northeast Brooks Range, Alaska. The image is a digital enhancement of the photograph (fig. 5) on page 9. Lithostratigraphy, Microlithofacies, and Conodont Biostratigraphy and Biofacies of the Wahoo Limestone (Carboniferous), Eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska By Andrea P. Krumhardt, Anita G. Harris, and Keith F. Watts U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 Description of the lithostratigraphy, microlithofacies, and conodont bio stratigraphy and biofacies in a key section of a relatively widespread stratigraphic unit that straddles the Mississippian-Pennsylvanian boundary UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1996 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY GORDON P. EATON, 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. Published in the Eastern Region, Reston, Va. Manuscript approved for publication June 26, 1995. Library of Congress Cataloging in Publication Data Krumhardt, Andrea P. Lithostratigraphy, microlithofacies, and conodont biostratigraphy and biofacies of the Wahoo Limestone (Carboniferous), eastern Sadlerochit Mountains, northeast Brooks Range, Alaska / by Andrea P. Krumhardt, Anita G. Harris, and Keith F. Watts. p. cm. — (U.S. Geological Survey professional paper ; 1568) Includes bibliographical references. Supt, of Docs, no.: I 19.16:1568 1. Geology, Stratigraphic—Pennsylvania^ 2. Geology, Stratigraphic—Mississippian. 3. Geology—Alaska—Sadlerochit Mountains Region. 4. Conodonts—Alaska— Sadlerochit Mountains Region. 5. Paleontology—Pennsylvanian. 6. Paleontology— Mississippian. 7. Wahoo Limestone (Alaska). I. Harris, Anita G. II. Watts, Keith F. III. Title. IV. Series. QE673.K77 1996 551.7'5'097987—dc20 95-31281 CIP CONTENTS Abstract........................................................................................................................... 1 Introduction..................................................................................................................... 2 Acknowledgments................................................................................................... 2 Previous Studies.............................................................................................................. 4 Regional Geologic Setting.............................................................................................. 5 Lisburne Group, Northeast Brooks Range.............................................................. 5 Alapah Limestone........................................................................................... 7 Alapah Limestone-Wahoo Limestone Boundary, Northeast Brooks Range........... 7 Wahoo Limestone............................................................................................ 7 Lithostratigraphy of the Wahoo Limestone, Eastern Sadlerochit Mountains ................. 9 Lower Member of the Wahoo Limestone ............................................................... 10 Upper Member of the Wahoo Limestone................................................................ 10 Conodont Biostratigraphy of the Wahoo Limestone, Eastern Sadlerochit Mountains ........................................................................................................... 12 muricatus Zone ....................................................................................................... 13 Lower muricatus Subzone .............................................................................. 13 Upper muricatus Subzone............................................................................... 13 noduliferus-primus Zone......................................................................................... 14 minutus Fauna......................................................................................................... 15 Lower minutus Fauna...................................................................................... 15 Idiognathodus Fauna............................................................................................... 16 The Mid-Carboniferous Boundary—An Approximation of the Mississippian- Pennsylvanian Boundary .................................................................................... 17 Biostratigraphic Criteria.......................................................................................... 17 Conodont-Based Boundary in the Eastern Sadlerochit Mountains......................... 18 Foraminiferan-Based Boundary in the Eastern Sadlerochit Mountains ................. 18 Morrowan-Atokan Boundary.......................................................................................... 20 Conodont Biofacies......................................................................................................... 21 Conodont Biofacies and Associated Microlithofacies, Wahoo Limestone, Eastern Sadlerochit Mountains ................................................................... 21 Mississippian Part of the Wahoo Limestone................................................... 22 Cavusgnathid Biofacies .......................................................................... 22 Near-Restricted to Open-Platform Environments........................... 22 Cavusgnathid-Kladognathid Biofacies ................................................... 25 Open-Platform to Open-Marine Environment................................ 25 Gnathodid-Hindeodid Biofacies ............................................................. 26 Low-Energy, Open-Marine Environment....................................... 26 Pennsylvanian Part of the Wahoo Limestone.................................................. 26 Lower Member of the Wahoo Limestone....................................................... 27 Adetognathid-Related Biofacies............................................................. 27 Near-Restricted to Open-Platform Environment............................ 27 Low-Energy, Open-Marine Environment....................................... 27 Upper Member of the Wahoo Limestone........................................................ 27 Adetognathid-Rhachistognathid Biofacies ............................................. 27 Restricted to Near Open-Platform Environment............................. 27 Open-Platform to Near-Shoal Open-Platform Environments......... 28 Tidal-Channel(?) Environment....................................................... 28 III IV CONTENTS Rhachistognathid Biofacies.................................................................... 28 Near-Shoal, Open-Platform Environment...................................... 28 Shoal or Tidal-Channel Environments............................................ 28 Near-Shoal, Open-Marine Environment......................................... 29 Declinognathodid-Related Biofacies...................................................... 30 Near-Shoal, Open-Marine Environment......................................... 30 Low-Energy, Open-Platform and (or) Open-Marine Environment........................................................................ 30 Biofacies Summary................................................................................................. 30 Conodont Preservation and CAI Values ......................................................................... 31 Systematic Paleontology................................................................................................. 32 References Cited............................................................................................................. 50 Appendix 1. Conodont Faunas, Biofacies, and Age and Lithology of Collections Mentioned in Text but not Described Elsewhere in this Report......................... 59 PLATES [Plates 1-5 follow appendix 1; plate 6 in pocket] 1-3, 5. Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains, Alaska. 4. Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains, and Pogopuk Creek, Franklin Mountains, Alaska. 6. Conodont zones, faunal intervals, and species distribution and lithologies of the Wahoo Limestone in the study section, eastern Sadlerochit Mountains, northeast Brooks Range, Alaska. FIGURES 1. Map showing distribution and tectonic affinities of the Lisburne Group in the Brooks Range.................................... 3 2. Map showing distribution of the Lisburne Group, major structural features, and location of study section, northeast Brooks Range ................................................................................................................................................ 4 3. Diagram showing generalized stratigraphic succession, northeast Brooks Range and northeast coastal plain............ 6 4. Schematic diagram showing stratigraphic relationships, lithologies, and inferred depositional environments of the Lisburne Group, northeast Brooks Range..........................................................................................................