DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIBECTOR' 596 GEOLOGY AND COAL RESOURCES OP NORTH PARK, COLORADO BY A. L. BEEKLY WASHINGTON GOVERNMENT PRINTING OFFICE 1915 CONTENTS. Page. Introduction _ ______ _,___________ 7 Location and area__ _ _ _____. __________1___ 7 Accessibility_________________________________ 8 Explorations in the region________________________ 8 Preparation of the map___________________________ 10 Base map_.______________________________ 10 ' Field work_______________________________ 10 Office work______________._________ __ 11 Acknowledgments_______________________________ 11 Geography ______________ ______________________ 12 Relief______________________________________ 12 Major features..____________.________________ 12 Medicine Bow Range_______.________ ______ 12 Park Range____________________________ 13 Continental Divide____________.___________ 13 Floor of the park____________ '._.___________ 13 Minor features________________:_. ______ 14 Drainage___________________ ______________ 16 Settlement__________i_______________________ 18 Stratigraphy __________ __________.___________ 19 Sedimentary rocks ______________________________ 19 Age and correlation.. ______!____ .___________ 19 Geologic section________________._________'_ 20 Carboniferous (?) system_______________________ 21 Pennsylvanfan or Permian (?) series______________ 21 Distribution and character_____.___________ 21 Stratigraphic relations________.___________ 21 Fossils_____________________________ 22 Triassic (?) system___________________________ 23 Chugwater formation_______________________ 23 Distribution, character, and thickness__________ 23 Stratigraphic relations____________________ 24 Fossils____________________________ 26 Jurassic or Cretaceous system___ ____ _ 26 Morrison formation___________________^___ .26 : Character, thickness, and distribution___________ 26 Stratigraphic relations_________________ _ 27 Fossils,________________________._____ 29 Cretaceous system (Upper Cretaceous series).__ 30 Dakota sandstone____________________ _ 30 Correlation_____________________ __ 30 Character and thickness__________ 30 Distribution ____ ________ 31 Stratigraphic relations __________ _ 33 Fossils _________.,__________________ 34 3 4 CONTENTS. Stratigraphy Continued. Page. Sedimentary rocks Continued. Cretaceous system (Upper Cretaceous series) Continued. Colorado group __________________'__________- 34 General features_______________:_______ 34 Benton shale ________________________ 34 Character and thickness________:________ 34 Distribution _______________________ 35 Stratigraphic relations.___________ ___ 36 Fossils _________,.________________ 38 Niobrara formation_____________________ 39 Distribution, character, and thickness________ 39 Stratigraphic relations________________ 41 Fossils __________________________ 42 Montana group _________________________._ 43 General features____________________ __ 43 Pierre shale___.______________________ 43 Character and thickness__^____._________ 43 Distribution _______________________ 45 Stratigraphic relations_________________ 45 Fossils __________________:________ 47 Cretaceous or Tertiary system_______________ ___ 49 Coalmont formation____________________ _ __ 49 General features_________________________ 49 Character and thickness____________ _ 50 Distribution __________________________ 58 Stratigraphic relations_______________ 58 Fossils _________*___________________ 61 Tertiary system___________:_________________ 66 North Park formation_______________________ 66 Designation__________________________ 66 Character and thickness_______:___________ 66 Distribution ______________1*._________ 67 Stratigraphic relations_________________ 68 Quaternary system ______________;__ ___ 71 General features_________________________ 71 Alluvium ______________________"- 71 Terrace gravel______'____________________ 72 Dune sand _____________________:_____ 72 Glacial deposits and glaciation___________________ 73 General features_______________________ 73 Park Range______________________ __ 74 Arapaho Creek ___:_______________________ 75 Medicine Bow Range____________________- 75 Igneous and metamorphic rocks______________________ 76 General features_______________..___..________^__ 76 Crystalline rocks___r._______________________'________ __ 76 Volcanic rocks__l___________ _ _ _____ _ 78 Extent of volcanism____ ________ 78 Distribution and character '____ .. 78 Age of eruptive rocks__ _ 81 Structure___________________ :~ 81 General character and representation_____ _ 81 CONTENTS. 0 Structure Continued. ' Page. Major features. _ _____ _________ 82 Location and character_________________________ 82 Park Range and Medicine Bow uplifts_________ 82 Divide between North and Middle parks________ 83 Independence Mountain fault _______.____________ 83 Minor features. _______________________"__ 83 Faults __________________________________ 83 Extent and influence_________________ ___ 83 Independence Mountain fault____________ 84 Sheep Mountain fault series______________ __ 84 Sentinel Mountain fault _______________ __ 86 Kerr ranch fault__________________________ 86 Hill Valley fault___._______________________ 88 Fault near north end of McCallum anticline___ _ 88 Miscellaneous small faults__ __ _ __ 89 Folds _______________________1________ 89 Location and origin__________________ ___ 89 North Park syncline_______________________ 90 McCallum anticline__________________________ 90 Folds near the Kerr ranch,________________ ______ 92 Pinkham Creek folds______________________ 92 Miscellaneous small folds_______:_______ ____ 93 Economic geology ________ -_________________ ____ 93 Mineral resources_________________________ ____ 93 Coal ______________'________ __________,.____ 93 Geologic occurrence ______________.__-_________ 93 McCallum anticline district________________ ____ 95 General features____________±___________ _ 95 Coal beds of the district_______________ ____ 95 Sudduth bed_________________________ 95 Capron beds_________________ __ _ _ 98 Winscom beds __________________ ____ 98 Hill bed ____________________________ 99 Development _______________________ _ _ 99 McCallum mine ________________ _ 99 Sudduth mine_________________________ 100 Marr mine_____ _______ __ __ _ 100 Kerr mine_^__________________________ 101 Lange, Manning, and Ballinger prospects___ ____ 101 Capron mine_________________________ 101 Winscom mine___________________ ___ 102 .Hill mine-.___________________________ 102 Coalmont district _____________________ ___ 102 General features __________________________ 102 Coal beds______________________________ 103 Riach bed ___________J________________ 103 Lower beds of Coalmont section______________ 104 Development_________________.__________ ' 106 Northern Colorado Coal Co.'s mine____________ 106 Abandoned mines _______ ____________ 106 Local coal areas _____________________________ 107 Mitchell________________'________________ 107 Location and extent-______ _ ___~____ 107 D ILLUSTRATIONS: Economic geology "Continued. c Page. Coal Continued. Local coal areas Continued. Mitchell Continued. - . Coal bed____________________________ 107 Mitchell mine ________________________ 107 Monahan __ __________r___________ 108 Location and extent_____________________ 108 Coal beds _______:___....._____________ 108 Monahan mine_________________________ 108 Colorado Creek _______________,__________ 109 Arapaho Pass____________________________ 109 Character of the coal__________________________ 109 Physical properties________________________ 109 Chemical properties _______________________ 111 Classification.__________________________ 114 Production ______.._ _____'.-_________________________ 114 Estimated tonnage ________..__________________ 114 Future development __________________________ 115 Metals_____________________________________ 116 Copper____________..____________________ 116 Gold._____________..____________________ 117 Silver___________________________________ 117 Gilsonitel___________________________________ 117 Index________________________________i________ 119 ILLUSTRATIONS. Page. PLATE I. A, Eroded sandstone of Coalmont formation; B, Crest of Zir- kel Mountain ___ _____ _________________ 12 II. Floor and rim in southeast part of North Park__________ 13 III. A, Dune sand; B, Banded gneiss near top of Zirkel Mountain.. 72 IV. Mouth of Red Canyon ____ _____ 73 V. A, Weathered granite; B, Erosion forms in granite_______ 78 VI. A, Columnar basalt capping Spicer Peak; B, Volcanic breccia__ 79 VII. Porphyry dike ____ ! 80 VIII. Delanos Butte ___________ _____ _. 81 IX. A, V-shaped fold in Dakota sandstone; B, Marr coal bank 92 X. Sections of coal beds of North Park, Colo__ 96 XI. A, Coalmont from the southeast; B, Upper 30 feet of Riach coal bed ________________________ _-_ 102 XII. Geologic map and sections of North Park, Colo_:_ In pocket. FIGURE 1. Index map of Colorado, showing location of North Park. 7 GEOLOGY AID COAL RESOURCES OF NORTH PARK, COLORADO. By A. L. BEEKLT. INTRODUCTION. LOCATION AND AREA. North Park is a great natural depression in the Rocky Mountains of northern Colorado. Its remoteness from much frequented routes of travel, amounting until recent years almost to isolation, has re­ sulted in its geology remaining but very little known until the pres- 200 MILES FIGURE 1. Index, map of Colorado, showing location of North Park. ent time. It covers about 1,400 square miles, including practically all of Jackson County. (See fig. 1.) Its northern boundary is