General and Engineering Geology of the Northern Part of Pueblo, Colorado By GLENN R. SCOTT Description of the geology of the bedrock and surficial deposits in and near Pueblo, Colo. Engineering behavior of the rocks is summarized at the end of report UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKLE, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress catalog-card No. GS 68-37,9 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Abstract...._ _-__-___-_-_-_-__-_---_----_______--_________________ 1 Introduction._____________________________________________________ 2 Sources of information, and acknowledgments.____________________ 4 How to interpret the geologic map.._____________________________ 6 Investigation procedure and engineering-geology practice.___________ 7 Climate.___----------_--_---------_________________________ 21 Floods---------.----.--------------_--_--------_-----_,_.__ 22 Explanation of the use of technical terms...______________________ 25 Description and engineering-geology properties of outcropping rocks_ ____ 26 Sedimentary rocks.__________-____-_-_________________________ _. 28 Dakota Sandstone.__-__--__-__-__.__-____________-______-_ 28 Granerps Shale_________---_-_-___-_____-_-________._____ 30 Greenhorn Limestone.___--___----_______________._---__-__ 34 Lincoln Limestone Member.____________________________ 34 Hartland Shale Member________--___-____--____________ 37 Bridge Creek Limestone Member.---_-___________--_____ 38 Carlile Shale.._____._.-._.....________________.__ 41 Fairport Chalky Shale Member. ______________________ 41 Blue Hill Shale Member_______.____________________ 43 Codell Sandstone Member_-_________-.____-_____-______ 47 Juana Lopez Member.-.__-____--___-_-_-_-_-__--___-__ 49 Niobrara Formation.___________^_______-____.______-______ 50 Fort Hays Limestone Member._________________________ 50 Smoky Hill Shale Member____________________________ 52 Shale and limestone unit__________________________ 52 Lower shale unit ________________________________ 53 Lower limestone unit__----_--___---___-__-__-___-__ 55 Middle shale unit..._______________________________ 56 Middle chalk unit-___-____-____-____..--_-___-__-__ 58 Upper chalky shale unit.________---__-----__-______ 60 Upper chalk unit.___.-____--_________-----________ 62 Pierre Shale____________-------____-_-__--__----------_-_- 65 Transition member.__--._-____--___-_____-___-_____-__ 65 Apache Creek Sandstone Member.______________________ 70 Sharon Springs Member________________________________ 74 Rusty zone.______--_-_-_---_____-__--_-_--___-_--__-_ 77 Tepee zone._____________-__-______-___-_-_-__--___-__ 80 Surficial deposits._____________________________________________ 84 Nussbaum Alluvium..___--_-_________________-____-_-__--- 86 Rocky Flats Alluvium_____________________________ ______ 89 Verdos Alluvium____.-_____-___---__-____-----_______-__ 90 Slocum Alluvium.____------________-_-__--___-___.--___--- 92 in rv CONTENTS Description and engineering-geology properties of outcropping rocks Con. Surficial deposits Continued Page Louviers Alluvium.._______________________________________ 97 Broadway Alluvium_____________________________________ 100 Eolian sand.______________________________________________ 102 Piney Creek Alluvium____________________________________ 106 Colluvium______________________________________________ 109 Post-Piney Creek alluvium_______________________________ 111 Artificial fill_______---____-_-__________--_-_______.________ 114 Structural geology.________________________________________________ 115 Geologic history____--_-__-_----__-___--__--____________________-_ 116 Economic geology_____-___--_-______----_-_-___-_-_________-____ 117 Limestone.___________________________________________________ 118 Clay_--__-____--_-_---_---------_--_---_--___------_-----_-__ 118 Riprap. _____________'_________________________________________ 118 Ornamental stone___________________________________________ 119 Structural and dimension stone________________________________ 119 Gravel and sand____________________________________________ 119 Summary of engineering behavior of geologic units at Pueblo__________ 120 References cited_________________________________________________ 122 Index..___________________-_--_----_-.-- ____________________ 125 ILLUSTRATIONS [Plate 1 in pocket; plate 2 follows index] Page PLATE 1. Geologic map of the Northwest and Northeast Pueblo quadrangles, Colorado. 2; Drawings of fossils characteristic of the Cretaceous rocks at Pueblo. FIGURE 1. Map showing location of Pueblo_--_----_----------__- 2. Design curves for thickness of surfacing and subbase courses, ________-___________-_-____--_-----_--_-- 3. Photograph of PVC (potential volume change) meter____ 12 4. Photograph of two tablets of soil after removal from PVC meter______________________-._.________ 13 5. Graph showing results of consolidation test of remolded Pierre Shale..____________________________________ 14 6-9. Photographs: 6. Alligator cracks in bituminous mat.___________ 17 7. Destruction of sidewalk by sulfate reaction. ____ 18 8. Efflorescence of sodium sulfate along the channel of a seep from the Apache Creek Sandstone Member of Pierre Shale____-_____--_-___- 19 9. Dakota Sandstone along Arkansas River. ------ 29 10. Graph showing general size-distribution characteristics of a typical sample of Graneros Shale_________________ 30 11. Diagram showing X-ray diffractometer traces of Graneros Shale.___-_-_--_________________________________ CONTENTS V Page FIGURE 12. Graph showing plasticity index versus liquid limit for shale units of Cretaceous age________________1____ 33 13. Photograph of Lincoln Limestone Member of Greenhorn Limestone._______---__----____-_________________ 34 14. Photograph of "marker" bentonite 1.5 feet above base of Lincoln Limestone Member_______________________. 35 15. Graph showing general size-distribution characteristics of typical shale samples of Lincoln Limestone and Hartland Shale Members._________________________ 36 16. Photograph of Bridge Creek Limestone Member of Greenhorn Limestone._-___.._-_.-..-______.____-. 39 17. Photograph of Fairport Chalky Shale Member of Carlile Shale..-----_------------------------------..--- 42 18. Graph showing general size-distribution characteristics of typical samples of Fairport Chalky Shale and Blue Hill Shale Members_____..__________.__.........._ 43 19-24. Photographs: 19. Lower part of Blue Hill Shale Member of Carlile Shale .... - _. -.-_...-...._.... 44 20. Upper part of Blue Hill Shale Member of Carlile Shale..----_------_--___-__--------.-__ 45 21. Septarian concretion in Blue Hill Shale Member. 46 22. Codell Sandstone Member of Carlile Shale.____ 48 23. Fort Hays Limestone Member of Niobrara Formation. _________________________________ 51 24. Shale and limestone unit of Smoky Hill Shale Member. __________________________________ 53 25. Graph showing general size-distribution characteristics of typical samples of lower and middle shale units and upper chalky shale unit.______----_____-_-________ 54 26-32. Photographs: 26. Lower limestone, lower shale, and shale and limestone units of Smoky Hill Shale Member. 55 27. Concretion subunit of middle shale unit of Smoky Hill Shale Member.________________ 57 28. Middle chalk unit of Smoky Hill Shale Member. 59 29. Upper chalky shale unit of Smoky Hill Shale Member. ________________________________ 61 30. Crack in facing beneath the Interstate 25 Free­ way bridge over 2d Street________________ 63 31. Upper chalk unit of Smoky Hill Shale Member. 64 32. Transition member of Pierre Shale.___________ 66 33. Graph showing general size-distribution characteristics of typical samples of transition member.____________ 67 34. Photograph showing damage caused by swelling clay in transition member._______________________________ 69 35. Photograph of Apache Creek Sandstone Member of Pierre Shale__-______--____-__-__-____-______-- 70 36. Graph showing general size-distribution characteristics of Apache Creek Sandstone Member ________________ 71 VI CONTENTS Page FIGUKE 37. Photograph of Sharon Springs Member of Pierre Shale_ _ 75 38. Graph showing general size-distribution characteristics of typical samples of Sharon Springs Member and Rusty and Tepee zones._________________________ 76 39-43. Photographs: 39. Rusty zone of Gilbert of Pierre Shale.________ 78 40. Tepee zone of Gilbert of Pierre Shale. _________ 81 41. Tepee butte limestone in Tepee zone._________ 82 42. Tepee buttes rising out of the Tepee zone______ 83 43. Nussbaum Alluvium on Baculite Mesa_--_____- 87 44-46. Graphs showing 44. General size-distribution characteristics of typical samples of Nussbaum and Rocky Flats Alluviums______________________________ 88 45. Plasticity index versus liquid limit for pre-Bull Lake Alluvium.__________________________ 91 46. General size-distribution characteristics of Verdos Alluvium._____________ ____________ 91 47. Photograph showing coarse-grained Slocum Alluvium of Arkansas River origin..___________________________ 93 48. General size-distribution characteristics of fine-grained and gravel facies of Slocum Alluvium.______________' 94 49. Photograph showing coarse-grained Louviers Alluvium of Arkansas River origin_-__--__-_________---_-_-_-__ 98 50-52. Graphs showing 50. General size-distribution characteristics of typical samples of coarse-grained facies of Louviers Alluvium