GEOLOGY OF PRE- TERTIARY ROCKS IN THE NORTHERN PART OF YELLOWSTONE NATIONAL PARK, m WYOMING "* ,~ - DivMOri Coforado Distril'l r ih•." n' Geology of Pre-Tertiary Rocks in the Northern Part of Yellowstone National Park, Wyon1ing By EDWARD T. RUPPEL With a section on Tertiary laccoliths, sills, and stocks in and near the Gallatin Range, Yellowstone National Park GEOLOGY OF YELLOWSTONE NATIONAL PARK GEOLOGICAL SURVEY PROFESSIONAL PAPER 729-A UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 72-600268 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 2401-00242 Yellowstone National Park, the oldest of the areas set aside as part of the national park sys­ tem, lies amidst the Rocky Mountains in north­ western Wyoming and adjacent parts of Montana and Idaho. Embracing large, diverse, and complex geologic features, the park is in an area that is critical to the interpretation of many significant regional geologic problems. In order to provide basic data bearing on these problems, the U.S. Geological Survey in 1965 initiated a broad pro­ gram of comprehensive geologic and geophysical investigations within the park. This program was carried out with the cooperation of the National Park Service, and was also aided by the National Aeronautics and Space Administration, which supported the gathering of geologic information needed in testing and in interpreting results from various remote sensing devices. This professional paper chapter is one of a series of technical geo­ logic reports resulting from these investigations. CONTENTS Page Page Abstract _____________________________________________________________________________________ _ Al Geology- Continued Introduction ______________________________________________________________________________ _ 2 Mesozoic sedimentary rocks- Continued Previous work------------------------------------------------------------------- 2 Jurassic- Continued Acknowledgments _____________________________________________________________ _ 4 Ellis Group- Continued Topography and drainage--------------------------------------------- 4 Swift Formation.... --------------------·------------· A26 Gallatin Range _________________________________________________________ _ 4 Morrison Formation--------·-···-·--·-------·-------------· 26 Mount Everts-Rescue Creek-------------------------------- 5 Cretaceous__________________________________________________________________ 27 Buffalo Plateau ________________________________________________________ _ 5 Lower Cretaceous formations----------------------· 27 Slough Creek-Soda Butte Creek_ _______________________ _ 5 Upper Cretaceous formations----------------------- 28 GeologY---------------------------------------------------------------------------------------· 5 Tertiary igneous rocks--------------------------------·-----·------------- 29 Precambrian metamorphic rocks--------------------------------· 8 PetrographY------------------------------------------------------------·· 30 Schist--------------------------------------------------------------------------- 9 Quartz monzonite------------------------·-------------------- 30 Granitic gneiss---------------------------------------------------------­ 9 Rhyodacite and quartz latite_________________________ 33 Age and regional relations .... -------·--------------------·-· 10 Granodiorite, quartz diorite, and related Paleozoic_ sedimentary rocks ________________________________________ _ 11 rocks------------------------·-·---------------·------·-·---------·-· 33 Cambrian-----------------------------------·----·-------·····-·---·--·-··-·· 11 Descriptions of intrusive masses.---------------·-·------ 34 Flathead Sandstone ________________________________________ _ 12 Mount Holmes stock-------·----------------·-···------···· 34 Wolsey Shale ____________________________________________________ _ 13 Metamorphism... ----------·-·-----·····-··············· 35 Meagher Limestone------------------------------------------ 14 Laccoliths and sills----------------··--·-·-----------·----·· 36 Park Shale ... ------------------------------------------------------ 14 Metamorphism------------------------····---·----------· 37 Pilgrim Limestone.. -------------------------------·------·--- 15 Indian Creek laccolith-------------------------·-·· 37 Snowy Range Formation.... ___________________________ _ 15 Gallatin River sills .... ------·--------------··-----· 39 Dry Creek Shale Member-----------------------­ 16 Gray Peak-Snowshoe laccoliths and Sage Limestone Member ..... -------------------· 16 sills .. -------------------------------------------------------- 39 Grove Creek Limestone Member ........ 17 Fan Creek sills---------------------------···-----·---·- 40 Ordovician------------------------------------------------------------------ 17 Electric Peak sills .. -----------------------·-·--------· 40 Bighorn Dolomite----------------·---------------·------·----- 17 Gallatin River laccolith .... -----·---------------· 41 Devonian -------------------------------------------------------····-····--· 17 Mount Everts sills .. -------------····--·------·-···-· 41 Jefferson Formation---------------------------------------­ 18 Electric Peak stock---------------·--·-·-····------···---··· 42 Three Forks Formation.-------·--------·--------·------ 18 Metamorphism__________________________________________ 42 Mississippian ___________________________________________________________ _ 19 Bighorn Pass sheet-------·----·------·-------·----···-·---- 42 Lodgepole Limestone ______________________________________ _ 19 Age of intrusive rocks-----------------------------·--·------------ 43 Mission Canyon Limestone __________________________ _ 20 Structure·-----------------------------------------------------------------------·--- 44 Pennsylvanian-----·-----------·--··---------·------------·--·----·------ 21 Structure of Precambrian crystalline rocks....... 45 Amsden Formation _________________________________________ _ 22 Folds in sedimentary rocks ... -------------·------··-·-------- 45 Quadrant Sandstone.......... ------------·-----------------· 22 Crowfoot fault zone .. -----------------·------------·---------------·- 45 Permian _____________________________________________________________________ _ 23 Reverse faults----------------------------·------------------·--·-·--·--- 49 Shedhorn Sandstone. _______________________________________ _ 23 Age of reverse faulting .. --------------------------------· 50 Mesozoic sedimentary rocks------------------------------------·---· 23 North-trending normal faults_______________________________ 51 Triassic ______________________________________________________________________ _ 24 Age of north-trending faults ...... ----·-------------- 54 Dinwoody Formation.-------------------------------------· 24 Other north-trending probable faults and Woodside Formation _______________________________________ _ 24 lineaments-------------------------·------·-------·-·-----·--···· 54 Thaynes (?) Formation... ------------------------------·· 24 Northwest-trending normal faults_______________________ 55 Jurassic _____________________________________________________________________ _ 25 Regional implications and speculations .. ___________ 55 Ellis Group---------------------------------·------------·--·----·· 25 Stratigraphic sections------------------------------------------·-··--·-----------· 58 Sawtooth Formation.... ___________________________ _ 25 References cited-----------------------------------------·--·---·--·-·--·-···-------···· 62 Rierdon Formation _________________________________ _ 26 IndeX----------------------------------------------------------------·--------·--·----------······ 65 v VI CONTENTS ILLUSTRATIONS Page PLATE 1. Geologic map and sections of pre-Tertiary rocks, northern part of Yellowstone National Park _______________ Jn pocket FIGURE L Map showing areas of pre-Tertiary rocks, northern part of Yellowstone National Park, Wyo________________________ A3 2. Sketch showing the Gallatin Range from the southeast, with the Gibbon Geyser basin in the foreground 6 3. Photograph of cirques and glaciated valleys, Gallatin Range____________________________________________________________________________________ 7 4. Chart showing nomenclature of sedimentary rock units in Yellowstone National Park----------------------------------- 8 5-8. Photographs showing: 5. Sedimentary rocks exposed on Crowfoot Ridge, Gallatin Range------------------------------------------------------------------ 12 6. Three Rivers Peak, showing location of measured section of the Pilgrim Limestone and Snowy Range Formation·------------------------------------------------------------------------------------------------------------------------------------------- 13 7. Cliff outcrops of Cambrian and Ordovician rocks, view toward the south from Bighorn Pass, Gallatin Range·----------------------------------------------------------------------------------------------------------------------------------------------------------------- 16 8. Bannock Peak and the head of Panther Creek, showing location of measured section of Mississip- pian rocks, Gallatin Range·--------------------------------------------------------------------------------------------------------------------------- 19 9. Schematic cross section of part of Crowfoot Ridge, showing