Stratigraphy and Depositional Environments of the Mississippian Rocks, Garnet Range-Bearmouth Area, Granite County, Western Montana
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AN ABSTRACT OF THE THESIS OF Richard C. Schneider for the degree of Master of Science in Geology presented on May 2, 1988. Title: Stratigraphy and Depositional Environments of the Mississippian Rocks, Garnet Range-Bearmouth area, Granite County, western Montana Signature redacted forprivacy. Abstract approved: Keith F( Oles The Garnet Range-Bearmouth area of western Montana was the depositional site for basinal, platform slope, shelf, and peritidal Mississippian carbonate rocks. The following stratigraphic units, listed in ascending order, are recognized: the Paine Limestone, Middle Canyon Formation, Mission Canyon Limestone, and McKenzie Canyon Limestone of the Tendoy Group; the Kibbey Sandstone and the Lombard Limestone of the Snowcrest Range Group; and the Quadrant Sandstone. Although the Rattler Gulch section most closely resembles the Mississippian sequence described in the Tendoy Mountains of Montana, the Tendoy Group exposures at Rattler Gulch are older and occupied a position closer to the Transcontinental arch during the Mississippian. The geologic history of the thesis area consists of a major Early to Late Mississippian transgressive-regressive marine eustatic cycle documented by the Tendoy Group, and a less extensive Late Mississippian to Early Pennsylvanian transgresssive-regressive cycle represented by the Snowcrest Range Group and the Quadrant Sandstone. The first eustatic cycle began with a major transgression of the sea onto the Cordilleran platform in the Early Mississippian (late Kinderhookian). This resulted in the progradation of subtidal to lagoonal platform carbonates of the Mission Canyon Limestone over basinal limestones of the Paine Limestone and carbonate slope deposits of the Middle Canyon Formation. This cycle ended with a major regression that began in the Late Mississippian (early Meramecian). It is evidenced by the intertidal and supratidal sediments of the McKenzie Canyon Limestone and by the emergence of the carbonate shelf as a broad karst plain exposed to subaerial weathering. With renewed marine transgression in the late Meramecian, red tidal-flat and lagoonal siliceous sediments of the Kibbey Sandstone filled and covered the McKenzie Canyon Limestone karst. As the transgression continued into Early Pennsylvanian (Morrowan) time, the progressively clearer and deeper waters favored deposition of shallow-water carbonates of the Lombard Limestone. Following deposition of the Snowcrest Range Group, a slow westward regression, concurrent with the development of a rising land source in north-central Idaho, resulted in the deposition of the latest Mississippian-Early Pennsylvanian Quadrant Sandstone throughout western Montana. Stratigraphy and Depositional Environments of the Mississippian Rocks, Garnet Range-Bearmouth Area, Granite County, western Montana by Richard C. Schneider A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed May 2, 1988 Commencement June 1988 APPROVED: Signature redactedfor privacy. Profeof Geolog in charge of major Signature redacted for privacy. H9'ad f Departme Geology Signature redactedfor privacy. Dean of GracaJe School ç7 Date thesis is presented May 2, 1988 Typed by researcher for Richard C. Schneider ACKNOWLEDGMENTS I thank Dr. Keith F. Oles for his continual support and knowledgeable guidance throughout the preparation of my thesis. I also thank Drs. J. G. Johnson and Edward N. Taylor for their critical reviews of my thesis. Additional appreciation goes to Dr. Alan R. Niem for his helpful technical comments on carbonate petrography. A special thanks is given to Dr. William J. Sando of the United States Geological Survey who initially recommended my project and has provided enlightening suggestions and criticism of my research. Dr. Sando and his colleagues, Bruce R. Wardlaw, R. Stamm, and B. L. Mamet, also provided valuable analyses of the fossils found in my thesis area. The financial support provided by Amoco Production Company is gratefully acknowledged. Finally, a very special thanks to my parents, Dr. Richard F. and Virginia F. Schneider, and my wife, Ann, for their support and loving encouragement. TABLE OF CONTENTS INTRODUCTION I Results 6 Location and Accessibility 7 Investigative Methods 8 Previous Work 11 STRATIGRAPHIC INTERPRETATIONS 15 Paine Limestone 15 Middle Canyon Formation 24 Mission Canyon Limestone 49 McKenzie Canyon Limestone 73 Kibbey Sandstone 83 Lombard Limestone 91 Quadrant Sandstone 95 SEDIMENTATIONPL MODEL 102 MISSISSIPPIAN HISTORY 108 CONCLUSIONS 129 BIBLIOGRAPHY 131 APPENDIX A - RATTLER GULCH SECTION 141 APPENDIX B - MEGAFOSSIL FAUNAL LISTS 171 APPENDIX C - CONODONT FAUNAL LISTS 174 APPENDIX D - FORAMINIFER FAUNAL LISTS 183 LIST OF FIGURES Figure Page Mississippian structural features during the middle Osagean. 2 Cross-section of west-central United States showing Mississippian structural and geographic features above, and generalized Mississippian sediment types below. 3 Index map showing location of Garnet Range- Bearmouth area. 5 View of Mission Canyon Limestone ridges in Rattler Gulch. Photo taken from the mouth of Rattler Gulch looking to the north; red Kibbey Sandstone outcrop in left foreground. 9 Revised nomenclature for Mississippian stratigraphic units recognized in the northern Tendoy Mountains as compared with stratigraphic units previously recognized in this area. 14 Revised western interior Mississippian time scale showing biozonations based on foraminifers, conodonts, and corals and showing correlation of stratigraphic units in selected western interior rock sequences. 19 View of vertically dipping ridge of Middle Canyon Formation. Photo taken on the west side of Rattler Gulch looking to the west. Note the regular interbedding of limestone and ribbony chert. Jacob's staff (five feet long) for scale. 26 S. Photomicrograph of sponge spicules in micrite. Most of these spicules are monaxons and show characteristic spicule shape. All were originally opaline silica; now they are all calcite. Sample PS224, unit 16, lower member, Middle Canyon Formation. 30 9. Geopetal sediment infilling of cephalopod chamber. Sample PS223, unit 15, lower member, Middle Canyon Formation. 31 Figure Page Photomicrograph of large crinoid ossicle showing characteristic circular shape and central canal. The calcite ossicle (stained pink) is being replaced by dolomite rhombs (unstained) which have replaced the original matrix. Sample PS230, unit 21, middle member, Middle Canyon Formation. 36 Photograph of chertified Syringopora colony situated on the upsection edge of unit 13 (Middle Canyon Formation). 40 Translational slide in the lower member of the Middle Canyon Formation. Photo taken on the west side of Rattler Gulch looking to the west. Rock hammer near bottom center for scale. 45 View of vertically dipping Mission Canyon Limestone ridges on the east side of Rattler Gulch. Hitchcock limestone quarry at bottom center; red Kibbey Sandstone exposures at bottom right. 51 View of Tertiary karst cave in a ridge of Mission Canyon Limestone. Note the irregular boundaries and the thin, horizontal, siltstone beds filling the cave. 52 View of Hitchcock limestone quarry on the east side of Rattler Gulch. Although the quarry has been abandoned, the working faces are still discernible on a vertically dipping ridge of Mission Canyon Limestone. 53 Photomicrograph of a cross-section of a solitary coral. Sample PS32, unit 67, lower member, Mission Canyon Limestone. 56 Photomicrograph of normally packed oosparite with mostly well-formed, concentrically and multiple-coated, spherical grains. Sample PS62, unit 92, middle member, Mission Canyon Limestone. 59 Photomicrograph of foraminifers (upper right and lower left) and echinoderm fragments in a packed biomicrite. Sample PSIO6, unit 120, upper member, Mission Canyon Limestone. 62 Figure Page View of sinkhole filled with red-stained carbonate breccia in matrix of evaporite solution breccia of unit 139, McKenzie Canyon Limestone. Photo taken on the west side of Rattler Gulch looking to the east; upsection is to the right. 82 View of subdued Kibbey Sandstone outcrop. Photo taken on the west side of Rattler Gulch looking to the west. Vertically dipping Kibbey beds in the foreground are surrounded by flaggy Kibbey float. 85 Photomicrograph of well-sorted, subangular to subrounded, quartzose Quadrant sand surrounded by carbonate cement. Sample PS14O, unit 151, Quadrant Sandstone. 97 Diagram showing the depositional environments interpreted for the Tendoy Group in Rattler Gulch. This figure is not to scale and is modified from Shinn (1983) and Cook and Mullins (1983). 103 Plan view of the geometry of a modern tidal flat complex. Note that tidal flats can be present both adjacent to the land or in the lee of lime sand shoals (modified after James, 1984). 107 Paleogeography and lithofacies (partly restored) of middle Kinderhookian rocks during formation of initial Antler uplift at time of Siphonodella sandbergi conodont zone. 110 Paleogeography and lithofacies (partly restored) of upper Kinderhookian rocks during the development of the carbonate platform at the beginning of the Siphonodella isosticha-Upper S. crenulata Zone. 113 Paleogeography and lithofacies (partly restored) of lower Osagean rocks during development of the Woodhurst carbonate ramp at the time of the Lower Gnathodus typicus conodont zone. 117 Figure Page Paleogeography and lithofacies (partly restored) of middle Osagean rocks during a major transgression in the middle of