I) K I» A \i T M K NT () I'1 TII K INT K KI()K

BULLETIN

UN IT.KI) ST.AT.KS

GEOLOGICAL SURVEY

No. 119

A (iKOLOGH'AI, KKCOXNOISSANCE IN NOUTHWKST 

WYOMING KI.DRIDCE.

WASH I NUT ON

GOVKBTOIKNT PRINTING 

18i)4
LIBRARY CATALOGUE SLIPS.

United States. Department of the interior. (U. S. geological survey). 

Department of the interior | | Bulletin | of the | United 

States I geological survey | no. 119 | [Seal of the department] | 

Washington | government printing office 11894

 Second title: United States geological survey | J. W. Powell, 

"C director | | A | geological reconnoissance | in | northwest 

66 Wyoming | by | George Homans Eldridge | [Vignette] | 

Washington | government printing office 11894

8°. 72pp.

Eldridge (George Homans;.

United States geological survey | J. W. Powell, director | ) 

A | geological reconnoissance | in | northwest Wyoming ) 

by | George Homans Eldridge | [Vignette] |

Washington | gQvernmeut printing office | 1894

8°. 72pp.

[UNITED STATES. Department of the interior. (U. S. geological survey). 

Bulletin 119].

£ United States geological survey | J. W. Powell, director | |

S A | geological reconnoissance | in | northwest Wyoming |

g by | George Homans Eldridge | [Vignette] |

2f Washington | government printing office | 1894

" 8°. 72pp.

"S [UNITED STATES. Department of the interior. (U. S. geological survey).

3 Bulletin 119].

H
[Bulletin No. 119.]

' The publications of the United States Geological Survey are issued in accordance with the statute

approved March 3, 1879, -which declares that 

I "The publications of the Geologi cal Survey shall consist of the annual report of operations, geological 

i and economic maps illustrating the resources and classification of the lands, and reports upon general 

and economic geology and paleontology. The annual report of operations of the Geological Survey 

sball accompany the annual report of the Secretary of the Interior. All special memoirs and reports 

of said Survey shall be issued iu uniform quarto series if deemed necessary by the Director, but otherwise in ordinary octavos. Three thousand copies of each shall be published for scientific exchanges 

and for sale at the price of publication; and all literary and cartographic materials received in exchange 

shall be the property of the United States and form a part of the library of the organization; and the 

money resulting from the sale of such publications shall be covered into the Treasury of the United 

States."

On July 7,1882, the following joint resolution, referring to all Government publications, was passed 

by Congress:

"That whenever any document or report shall be ordered printed by Congress, therewhall be printed, 

in addition to the number in each case stated, the 'usual number' (1,734) of copies for binding and 

distribution among those entitled to receive them."

Except in those cases iu which an extra number of any publication has been supplied to the Survey 

by special resolution of Congress or has been ordered by the Secretary of the Interior, this office has 

no copies fo"r gratuitous distribution.

ANNUAL REPORTS.

I. First Annual Report of the United States Geological Survey, by Clarence King. 1880. 8°. 79 pp. 

1 map. A preliminary report describing plan of organization and publications.

II. Second Annual Report of the United States Geological Survey, 1880-'81, by J. W. Powell. 1882. 

8°. Iv, 588 pp. 62 pi. 1 map.

in. Third Annual Report of the United States Geological Survey, 1881-'82, by J. "W. Powell. 1883. 

8°. xviii, 564 pp. 67 pi. and maps.

TV. Fourth Annual Report of the United States Geological Survey, 1882-'83, by J. "W. Powell. 1884. 

8°. xxxii, 473 pp. 85 pi. and maps.

V. Fifth Annual Report of the United States Geological Survey, 1883-'84, by J. W. Powell. 1885. 

8°. xxxvi, 469 pp. 58 pi. and maps.

VI. Sixth Annual Report of the United States Geological Survey, 1884-'85, by J. "W. Powell. 1885. 

8°. xxix, 570 pp. 65 pi. and maps.

VII. Seventh Annual Report of the United States Geological Survey, 1885-'86, by J. "W. Powell. 1888. 

8°. xx, 656 pp. 71 pi. and maps.

VIII. Eighth Annual Report of the United States Geological Survey, 1886-'87, by J. "W. Powell. 1889. 

8°. 2pt. xix, 474, xii pp. 53 pi. and maps; 1 pi., 475-1063 pp. 54-76 pi. and maps.

I.. Ninth Annual Report of the United States Geological Survey, 1887-'88, by J. "W. Powell. 1889. 

8°. xiii, 717 pp. 88 pi. and maps.

.. Tenth Annual Report of the United States Geological Survey, 1888-'89, by J. W. Powell. 1890. 

8°. 2pt. xv, 774pp. 98 pi. and maps; viii, 123 pp.

 XI. Eleventh Annual Report of the United States Geological Survey. 1889-'90, by J. W. Powell. 1891. 

'8°. 2pt. xv, 757 pp. 66 pi. and maps; ix, 351 pp. 30 pi.

XII. Twelfth Annual Report of theUnitedStatesGeologicalSurvey, 1890-'91, byJ. W. Powell. 1891. 

8°. 2pt. xiii, 675pp. 53 pi. and maps; xviii, 576 pp. 146 pi. and maps.

XIII. Thirteenth Annual Report of the United States Geological Survey, 1891-'92, by J. W. Powell. 

1893. 8°. 3 pt. vii, 210 pp. 2 pi.; x, 372 pp. 105 pi. and maps; xii, 486 pp. 79 pi. and maps.

XIV. Fourteenth Annual .Report of the United States Geological Survey, 1892-'93, by J. W. Powell. 

1893. 8°. 2 pt. vi, 321 pp. 1 pi.
n ADVERTISEMENT.

MONOGRAPHS.

I. Lake Bonneville, by Grove Karl Gilbert. 1890. 4°. xx, 438 pp. 51 pi. 1 map. Price $1.50.

II. Tertiary History of the Grand Canon District, with atlas, by Clarence E. Button, Capt..TT. S. A. 

1882. 4°. xiv, 264 pp. 42 pi. and atlas of 24 sheets folio. Price $10.00.

III. Geology of the Corns took Lode and the Washoe District, with atlas, by George F. Becker. 1882. 

4°. xv, 422pp. 7 pi. and atlas of 21 sheets folio. Price $11.00. 

3TV. Comstock Mining and .Miners, by Eliot Lord. 1883. 4°. xiv, 451 pp. 3 pi. Price $1.50.

V. The Copper-Bearing Rocks of Lake Superior, by Roland Duer Irving. 1883. 4°. xvi, 464 pp. 

15 1. 29 pi. and maps. Price $1.85.

VI. Contributions to the Knowledge of the Older Mesozoie Flora of Virginia, by William Morris 

Fontaine. 1883. 4°. xi,144pp. 541. 54 pi. Price $1.05.

VII. Silver-Lead Deposits of Eureka, Nevada, by Joseph Story Curtis. 1884. 4°. xiii, 200 pp. 16 

pi. Price $1.20. ' . . Vin. Paleontology of the Eureka District, by Charles Doolittle Walcott. 1884. 4°. xiii, 298 pp. 

241. 24 pi. Price $1.10.

IX. Brachiopoda and Larnellibranchiata of the Raritan Clays and Greensand Marls of New Jersey, 

by Robert P. Whitfield. 1885. 4°. xx,338pp. 35 pi. 1 map. Price $1.15.

X. Dinocerata. A Monograph of an Extinct Order of Gigantic Mammals, by Othniel Charles Marsh. 

1886. 4°. xviii,243pp. 561. 56 pi. Price $2.70.

XI. Geological History of Lake Lahoutan; a Quaternary Lake of Northwestern Nevada, by Israel 

Cook Russell. 1885. 4°. xiv, 288pp. 46 pi. and maps. Price $1.75.

XII. Geology and Mining Industry of Leadville, Colorado, with atlas, by Samuel Franklin Emrnons. 

1886. 4°. xxix, 770 pp. 45 pi. and atlas of 35 sheets folio. Price $8.40.

XIII. Geology of the Quicksilver Deposits of the Pacific Slope, with atlas, by George I\ Becker. 

1888. 4°. xix, 486 pp. 7 pi. and atlas of 14 sheets folio. Price $2.00.

XIV. Fossil Fishes and Fossil Plants of the Triassic Rocks of New Jersey and the Connecticut Valley, by John S. Newberry. 1888. 4°. xiv, 152pp. 26 pi. Price $1.00.

XV. The Potomac or "Kouuger Mesozoie Flora, by "William Morris Fontaine. 1889. 4°. xiv, 377 

pp. 180 pi. Text and plates bound separately. Price $2.50.

XVI. The Paleozoic Fishes of North America, by John Strong Newberry. 1889. 4°. 340 pp. 53 pi. 

Price $1.00.

XVII. The Flora of the Dakota Group, a posthumous work, by Leo Lesqtoereux. Edited by F. H. 

Knowlton. 1891. 4°. 400pp. 66 pi. Price $1.10.

XVIII. Gasteropoda and Cephalopoda of the Raritan Clays and Greensand Marls of New Jersey, 

by Robert P. Whitfleld. 1891. 4°. 402pp. 50 pi. Price $1.00.

XIX. The Penokee Iron-Bearing Series of Northern Wisconsin and Michigan, by Roland D. Irving 

and C: R. Van Hise. 1892. 4°. xix, 534 pp. 37 pi.

XX. Geology of the-Eureka District, Nevada, with atlas, by Arnold Hague. 1892. 4°. 419pp. 8 pi.

XXI. The Tertiary Rhynchophorous Coleoptera of North America, by Samuel Hubbard Scudder. 

XXLT. A Manual of Topographic Methods, by Henry Gannett, chief topographer.

Jn press:

XXni. Geology of the Green Mountains in Massachusetts, by Raphael Pumpelly, J. E. Wolff, 

and T. Nelson Dale.

In preparation:

 Mollusca and Crustacea of the Miocene Formations of New Jersey, by R. P. Whitfield. 

 Sauropoda, by 0. C. Marsh.

 Stegosauria, by O. C. Marsh.

 Brontotheridsu, by 0. C. Marsh.

 Report on the Denver Coal Basin, by S. F. Emm on s.

 Report on Silver Cliff and Ten-Mile Mining Districts, Colorado, by S. F. Emmons.

 The Glacial Lake Agassiz, by Warren Upham.

BULLETINS.

1. On Hypersthene-Andesite and on Triclinic Pyroxene in Augitic Rocks, by WTiitman Cross, with a 

Geological Sketch-Of Buffalo Peaks, Colorado, by S.F. Emmons. 1883. 8°. 42pp. 2 pi. Price 10 cents.

2. Gold and Silver Conversion Tables, giving the coining value of troy ounces of fine metal, etc., computed by Albert Williams, jr. 1883. 8°. 8pp. Price 5 cents.

3. On the Fossil Faunas of the Upper Devonian, along the meridian of 76° 30', from Tompkins County, 

New York, toBradford County, Pennsylvania, by Henry S.Williams. 1884. 8°. 36pp. Price 5 cents.

4. On Mesozoie Fossils,, by Charles A. Wliite. 1884. 8°. 36pp. 9 pi. Price 5 cents.

5. A Dictionary of Altitudes in the United States, compiled by Henry Gannett. 1884. 8°. 325 pp. 

Price 20 cents.

6. Elevations in the Dominion of Canada, by J. W. Spencer. 1884. 8°. 43 pp. Price 5 cents.
ADVERTISEMENT. Ill

7. Mapoteca Geologica Americana. A Catalogue of Geological Maps of America (North and South), 

1752-1881, in geographic and chronologic order, by Jules Marcou and John Belknap Maroou. 1884. 

8°. 184 pp. Price 10 cents.

8. On Secondary Enlargements of Mineral .Fragments in Certain Eocks, by E. D. Irving and C. K. 

VanHise. 1884. 8°. 56pp. 6 pi. Price 10 cents.

9. A report of work done in the Washington Laboratory during the fiscal year 1883-'84, F. W. Clarke, 

chief chemist. T. M. Chatard, assistant chemist. 1884. 8°. 40pp. Price 5 cents.

10. On the Cambrian Faunas of North America. Preliminary studies, by Charles Doolittle "Waloott. 

1884. 8°. 74 pp. 10 pi. Price 5 cents.

11. On the Quaternary and Eecent Mollusca of the Great Basin; with Descriptions of New Forms, 

by E. Ellsworth Call. Introduced by a sketch of the Quaternary Lakes of the Great Basin, by G. K. 

Gilbert. 1884. 8°. 66 pp. 0 pi. Price 5 cents.

12. A Crystallographic Study of the Thinolite of Lake Lahontan, by Edward S. Dana. 1884. 8°. 

34 pp. 3 pi. Price 5 cents.

13. Boundaries of the United States and of the several States and Territories, with a Historical 

Sketch of the Territorial Changes, by Henry Gannett. 1885. 8°. 135 pp. Price 10 cents.

14. The Electrical and Magnetic Properties of the Iron-Carburets, by Carl Barus and Vincent 

Strouhal. 1885. 8°. 238 pp. Price 15 cents.

15. On the Mesozoic and Ceuozoic Paleontology of California, by Charles A. White. 1885. 8°. 33pp. 

Price 5 cents.

16. On the Higher Devoniau Faunas of Ontario County, New York, by John M. Clarke. 1885. 8°. 

86 pp. 3 pi. Price 5 cents.

17. On the Development of Crystallization in the Igneous Eocks of Washoe, Nevada, with notes on 

the Geology of the District, by Arnold Hague and Joseph P. Iddings. 1885. 8°. 44 pp. Price 5 

cents.

18. On Marine Eocene, Fresh-water Miocene, and other Fossil Mollusca of Western North America, 

by Charles A. White. 1885. 8°. 26 pp. 3 pi. Price 5 cents.

19. Notes on the Stratigraphy of California, by George F. Becker. 1885. 8°. 28 pp. Price 5 cents.

20. Contributions to the Mineralogy of the Eocky Mountains, by Whitman Cross and W. F; Hillebrand. 1885. 8°. 114 pp. 1 pi. Price 10 cents.

21. The Lignites of the Great Sioux Eeservation. A Eeport on the Eegion between the Grand and 

Moreau Rivers, Dakota, by Bailey Willis. 1885. 8°. 16 pp. 5 pi. Price 5 cents.

22. On New Cretaceous Fossils from California, by Charles A. White. 1885. 8°. 25 pp. 5 pi. 

Price 5 cents.

23. Observations on the Junction between the Eastern Sandstone and the Keweenaw Series on Keweenaw Point, Lake Superior, by E. D. Irving aud T. C. Chaniberliu, 1885. 8°. 124 pp. 17 pi, 

. Price 15 cents.

24. List of Marine Mollusca, comprising the Quaternary Fossils and recent forms from American 

Localities between Cape Hatteras and Cape Eoque, including the Bermudas, by William. Healy Dall. 

1885. 8°. 336pp. Price 25 cents.

25. The Present Technical Couditiou of the Steel Industry of the United States, by Phineas Barues. 

1885. 8°. 85pp. Price 10 cents.

26. Copper Smelting, by Henry M. Howe. 1885. 8°. 107 pp. Price 10 cents.

27. Eeport of work done in the Division of Chemistry and Physics, mainly during the fiscal year 

1884-'85. 1886. 8°. 80pp. Price 10 cents.

28. The Gabbros and Associated Hornblende Eocks occurring in the neighborhood of Baltimore, 

Md.,. by George Huntington Williams. 1886. 8°. 78pp. 4 pi. Price 10 cents.

29. On the Fresh-water Invertebrates of the North American Jurassic, by Charles A. White. 1886. 

8°. 41 pp. 4 pi. Price 5 cents.

30. Second Contribution to the Studies on the Cambrian Faunas of North America, by Charles Doolittlo Walcott. 1886. 8°. 369 pp. 33 pi. Price 25 cents.

31. Systematic Eeview of our Present Knowledge of Fossil Insects, including Myriapods and Arachnids, by Samuel Hubbard Scuddcr. 1886. 8°. 128 pp. Price 15 cents.

32. Lists and Analyses of the Mineral Springs of the United States; a Preliminary Study, by Albert 

C.Peale. 1886. 8°. 235pp. Price 20 cents.

33. Notes on the Geology of Northern California, by J. S. Diller. 1886. 8°. 23 pp. Price 5 cents. 

' 34. On the relation of the Laramio Molluscan Fauna to that of the succeeding Fresh-water Eocene 

and other groups, by Charles A. White. 1886. 8°. 54 pp. 5 pi. Price 10 cents.

35. Physical Properties ot the Iron-Carburets, by Carl Barus and Vincent Strouhal. 1886. 8°. 62 

pp. Price 10 cents.

36. Subsidence of Fine Solid Particles in Liquids, by Carl Barus. 1886. 8°. 58 pp. Price 10 cents.

37. Types of the Laramio Flora, by Lester F. Ward. 1887. 8°. 354 pp. 57 pi. Price 25 cents.

38. Peridotite of Elliott County, Kentucky, by J. S. Diller. 1887. 8°. 31pp. 1 pi. Price 5 cents.

39. The Upper Beaches and Deltas of the Glacial Lake Agassiz, by Warren Upham. 1887. 8°.- 84 

pp. 1 pi. Price 10 cents.

40.. Changes, in Eiver Courses in Washington Territory due to Glaciation, by Bailey Willis. 1887. 

8°. 10pp. 4 pi. Price 5 cents.
IV ADVERTISEMENT.

41. On the Fossil Faunas of the Upper Devonian the Genesee Section, New York, by Henry S. 

Williams. 1887. 8°. 121pp. 4 pi. Price 15 cents.

42. Eeport of work clone in the Division of Chemistry and Physics, mainly during the fiscal year 

1885-'86. F. W. Clarke, chief chemist. 1887. 8°. 152 pp. 1 pi. Price 15 cents.

43. Tertiary and Cretaceous Strata of the Tuscaloosa, Tombigbee, and Alabama Eivers, by Engene 

'A. Smith and Lawrence C. Johnson. J887. 8°. 189 pp. 21 pi. Price 15 cents.

44. Bibliography of North American Geology for 1886, by Nelson H. Darton. 1887. 8°. 35 pp. 

Price 5 cents. .

45. The Present Condition of Knowledge of the Geology of Texas, by Robert T. Hill. 1887. 8°. 94 

pp. Price 10 cents.

46. Nature and Origin of Deposits of Phosphate of Lime, by E. A. F. Penrose, jr., with an Introduction by N. S. Shaler. 1888. 8°. 143pp. Price 15 cents.

47. Analyses of Waters of the Tellowstone National Park, with an Account of the Methods of 

Analysis employed, by Frank Austin Gooch and James Edward Whitfleld. 1888. 8°. 84pp. Price 

10 cents.

48. On the Form and Position of the Sea Level, by Eobert Simpson Woodward. 1888. 8°. 88pp. 

Price 10 cents.

49. Latitudes and Longitudes of Certain Points in Missouri, Kansas, and New Mexico, by Eobert 

Simpson Woodward. 1889. 8°. 133 pp. Price 15 cents.

50. Formulas and Tables to facilitate the Construction and Use of Maps, by Eobert Simpson Woodward. 1889. 8°. 124pp. Price 15 cents.

51. On Invertebrate Fossils from the Pacific Coast, by Charles Abiathar "White. 1889. 8°. 102 pp. 

14 pi. Price 15 cents.

52. Subaerial Decay of Eocks and Origin of the Eed Color of Certain Formations, by Israel Cook 

Eussell. 1889. 8°. 65pp. 5 pi. Price 10 cents.

 53. The Geology of Nantucket, by Nathaniel Southgate Shaler. 1889. 8°. 55 pp. 10 pi. Price 10 

cents.

54. On the Thermo-Electric Measurement of High Temperatures, by Carl Barus. 1889. 8°. 313 pp., 

incl. 1 pi. 11 pi. Price 25 cents.

55. Eeport of work done in the Division of Chemistry and Physics, mainly during the fiscal year 

1886-'87. Frank Wigglesworth Clarke, chief chemist. 1889. 8°. 96 pp. Price 10 cents.

56. Fossil "Wood and Lignite of the Potomac Formation, by Frank Hall Knowlton. 1889. 8°. 72pp. 

7 pi. Price 10 cents.

57. A Geological EeconiJaissance in Southwestern Kansas, by Eobert Hay. 1890. 8°. 49 pp. 2 pi. 

Price 5 cents.

58. The Glacial Boundary in "Western Pennsylvania, Ohio, Kentucky, Indiana, and Illinois, by George 

Frederick Wright, with an introduction by Thomas Chrowder Chamberlin. 1890. 8°. 112pp., incl. 

Ipl. ffpl. Price 15 cents.

59. The Gabbros and Associated Eocks in Delaware, by Frederick D. Chester. 1890. 8°. 45 pp. 

Ipl. Price 10 cents.

60. Eeport of work done in the Division of Chemistry and Physics, mainly during the fiscal year 

1887-'88. F. W. Clarke, chief chemist. 1890. 8°. 174 pp. Price 15 cents.

61. Contributions to the Mineralogy of the Pacific Coast, by William Harlow Melville and "Waldomar 

' Lincigren. 1890. 8°. 40 pp. 3 pi. Price 5 cents.

62. The Greenstone Schist Areas of the Menoniinee and Marquetto Eegions of Michigan; a contribution to the subject of dynamic metamorphism in eruptive rocks, by George Huntiugton Williams; 

with an introduction by Eoland Duer Irving. 1890. 8°. 241 pp. 16 pi. Price 30 cents.

 63. A Bibliography of Paleozoic Crustacea from 1698 to 1889, including a list of North American 

species and a systematic arrangement of genera, by Anthony W. Vogdes. 1890. 8°. 177 pp. Price 

15 cents. '

64. A report of work done in the Division of Chemistry and Physics, mainly during .the fiscal year

 1888-'89. F. AV. Clarke, chief chemist. 1890. 8°. 60 pp. Price 10 cents.

65. Stratigraphy of the Bituminous Coat Field of Pennsylvania, Ohio, and West Virginia, by Israel 

C. White. 1891. 8°. 212pp. 11 pi. Price 20 cents.

66. On a Group of Volcanic Eocks from the Tewan Mountains, New Mexico, and on the occurrence 

of Primary Quartz in certain Basalts, by Joseph Paxson Iddings. 1890. 8°. 34 pp. Price 5 cents.

67. The Eolations of the Traps of the Newark System iu the New Jersey Eegion, by Nelson Horatio 

Darton. 1890. 8°. 82pp. Price 10 cents.

68. Earthquakes in California in 1889, by James Edward Keeler. 1890. 8°. 25 pp. Price 5 cents.

69. A Classed and Annotated Bibliography of Fossil Insects, by Samuel Hubbard Scudder. 1890.

 8°. 101pp. Price 15 cents..

70. Eeport on Astronomical Work of 1889 and 1890, by Eobert Simpson Woodward. 1890. 8°. 79pp. 

. Price 10 cents.

71. Index to the Known Fossil Insects of the World, including Myriapods and Arachnids, by Samuel 

Hubbard Scudder. 1891. 8°. 744 pp. Price 50 cents.

72. Altitudes between Lake Superior and the Eocky Mountains, by Warren Upham. 1891, 8°. 

229 pp. Price 20 cents.
ADVERTISEMENT. V

73. The Viscosity of Solids, by Carl Barus. 1891. 8°. xii, 139 pp. 6 pi. Price 15 cents.

74. The Minerals of North Carolina, by Frederick Augustus Genth. 1891. 8°. 119 pp. Price 15 

cents.

75. Record of North American Geology for 1887 to 1889, inclusive, by Nelson Horatio Darton. 1891. 

8°. 173 pp. Price 15 cents.

76. A Dictionary of Altitudes in the United States (second edition), compiled by Henry Gannett, 

chief topographer. 1891. 8°. 393 pp. Price 25 cents.

77. The Texan Permian and its Mesozoic Types of Fossils, by Charles A. White. 1891. 8°. 51 pp. 

4 pi. Price 10 cents.

78. A report of work done in the Division of Chemistry and Physics, mainly during the fiscal year 

1889-'90. F.W. Clarice, chief chemist. 1891. 8°. 131pp. Price 15 cents.

79. A Late Volcanic Eruption in Northern California and its Peculiar Lava, by J. S. Diller. 1891. 8°. 

33 pp. 17 pi. Price 10 cents.

80. Correlation papers Devonian arid Carboniferous, by Henry Shaler Williams. 1891. 8°. 279pp. 

Price 20 cents.

81. Correlation papers Cambrian, by Charles Doolittle Walcott. 1891. 8°. 447 pp. 3 pi. Price 

25 cents.

82. Correlation papers Cretaceous, by Charles A'. White. 1891. 8°. 273pp. 3'pl- Price 20 cents.

83. Correlation papers Eocene, by William Bullock Clark. 1891. 8°. 173pp. 2 pi. Price 15 cents.

84. Correlation papers Neocene, by W. H. Dall and G. D. Harris. 1892. 8°. 349 pp. 3 pi. Price 

25 cents.

85. Correlation papers-The Newark System, by Israel Cook Kussell. 1892. 8°. 344 pp. 13 pi.

Price 25 cents.

86. Correlation papers Archean and Algonkian, by C. R. Van Hise. 1892. 8°. 549 pp. 12 pi. 

Price 25 cents.

90. A report of-work done in the Division of Chemistry and Physics, mainly during the fiscal year 

1890-'91. F. W. Clarke, chief chemist. 1892. 8°. 77 pp. Price 10 cents.

91. Kecord of North American Geology for 1890, by Nelson Horatio Darton. 1891. 8°. 88pp. Price 

10 cents.

92. The Compressibility of Liquids, by Carl Barus. 1892. 8°. 96pp. 29 pi. Price 10 cents.

93. Some insects of special interest from Florissant, Colorado, and other points in the Tertiaries of 

Colorado and Utah, by Samuel Hubbard Scudder. 1892. 8°. 35 pp. 3 pi. Price 5 cents.

94. The Mechanism of Solid Viscosity, by Cail Barus. 1892. 8°. 138pp. Price 15 cents.

95. Earthquakes in California in 1890 and 1891, by Edward Singleton Holden. 1892. 8°. 31 pp. 

Price 5 cents.

96. The Volume Thermodynamics of Liquids, by Carl Barus. 1892. 8°. 100pp. Price 10 cents.

97. The Mesozoic Echinodermata of the United States, by William Bullock Clark. 1893. 8°. 207 

pp. 50 pi. Price 20 cents.

98. Flora of the Outlying Carboniferous Basins of Southwestern Missouri, by David White. 1893. 

8°. 139 pp. 5 pi. Price 15 cents.

99. Kecord of North American Geology for. 1891, by Nelson Horatio Darton. 1892. 8°. 73 pp. Price 

15 cents.

100. Bibliography and Index of the Publications of the U. S. Geological Survey, 1879-1892, by Philip 

Creveling Warman. 1893. 8°. 495pp. Price 25 cents.

. 101. Insect Fauna of the Rhode Island Coal Field, by Samuel Hubbard Scudder. 1893. 8°. 27 pp. 

2pi. Price 5 cents.

102. A Catalogue and Bibliography of North American Mesozoic Invertebrata, by Cornelius Breckinridge Boyle. 1893. 8°. 315 pp. Price 25 cents.

103. High Temperature Work in Igneous Fusion and Ebullition, chiefly in relation to pressure, by 

CarlBarus. 1893. 8°. 57pp. 9 pi. Price 10 cents.

104. Glaciation of the Yellowstone Valley north of the Park, by Walter Harvey Weed. 1893. 8°. 

41pp. 4 pi. Price 5 cents.

105. The Laramie and the overlying Livingston Formation in Montana, by Walter Harvey Weed, 

 with Report on Flora, by Frank Hall Kuowlton. 1893. 8°. 68pp. 6. pi. Price 10 cents.

106. The Colorado Formation and its Invertebrate Fauna, by T. W. Stanton. . 1893. 8°. 288 pp. 

45 pi. Price 20 cents.

107. The Trap Dikes of the Lake Champlain Region, by James Furman Kernp and Vernon Freeman Marsters. 1893. 8°. 62pp. 4 pi. Price 10 cents.

108. A Geological Reconnoissance in Central Washington, by Israel Cook Russell. 1893. 8°. 108pp. 

12 pi. Price 15 cents.

109. The Eruptive and Sedimentary Rocks on Pigeon Point, Minnesota, and their contact phenomena, by William Shirley Bayley. 1893. 8°. 121 pp. 16 pi. Price 15 cents.

110. The Paleozoic Section in the vicinity of Three Forks, Montana, by Albert Charles Peale. 1893. 

8°. 56 pp. 6 pi. Price 10 cents.

111. Geology of the Big Stone Gap Coal Field of Virginia and Kentucky, by Marius R. Campbell. 

1893. 8°. 106pp. 6 pi. Price 15 cents.

112. Earthquakes in California in 1892, by Charles D. Perrine. 1893. 8°. 57 pp. Price 10 cents.
VI ADVERTISEMENT.

113. A report of work done in the Division of Chemistry during the fiscal years 1891-'92 and 1892-'93l 

F. W. Clarke, chief chemist. 1893. 8°. 115pp. Price 15 cents.

114. Earthquakes in California in 1893, by C. D. Perrine. 1894. 8°. 23 pp. Price 5 cents.

115. A Geographic Dictionary of Ehode Island, by Henry Gannett. 1894. 8°. 31 pp. Price 5 cents.

116. A Geographic Dictionary of Massachusetts, by Henry Gannett. 1894. 8°. 126 pp. Price 15 

cents.

117. A Geographic Dictionary of Connecticut, by Henry Gannett. 1894. 8°. 67pp. Price 10 cents.

118. A Geographic Dictionary of New Jersey, by Henry Gannett. 1894. 8°. 131 pp. Price 15 cents.

119. A Geological Eeconnoissance in Northwest "Wyoming, by George H. Eldridge. 1894. 8°. 72 pp. 

Price 10 cents. 

In press:

120. The Devonian System of eastern Pennsylvania and New York, by Charles S. Prosaer.

121. A Bibliography of North American Paleontology, by C. E. Keyes. 

In preparation:

 The Moraines of the Missouri Coteau, and their attendant deposits, by James Edward Todd.

 A Bibliography of Paleobotany, by David White.

STATISTICAL PAPEES.

MineralEesources of the United States, 1882, by Albert Williams, jr. 1883. 8°. xvii, 813pp. Price 

50 cents.

Mineral Eesources of the United States, 1883 and 1884, by Albert Williams, jr. 1885. 8°. xiv, 1016 

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To THE DIRECTOR OF THE . UNITED STATES GEOLOGICAL SURVEY,

WASHINGTON, D. C. 

< WASHINGTON, D. C., 'July, 1894.

i_.
U.S.GEOLOGICAL SURVEY BULLETIN, 119. PL. I.

Geology by G. H. Eldridge JULIUS B1EN I CO UTH N Y.

EOCENE

Bridger Wasatch

FTb i rTvTl

Laramie Montana.

CJRJETAC^OUS

Colorado Dakota

JURA -TRIAS CARBONIFEROUS SILURIAN CAMBRIAN ARCHEAN BRECCIAS ERUPTIVE

Upper Lower ~l

Coal mines. X Coal prospects. GEOLOGY OF NORTHWESTERN WYOMING. o oil. Route of reconnaissance.

Scale of Miles.

10 20
DEPARTMENT OF THE INTERIOR

BULLETIN

OF THK

UNITED STATES

GEOLOGICAL SURVEY

No. 119

WASHINGTON

GOVERNMENT PRINTING OFFICE

1894

UNITED STATES GEOLOGICAL SURVEY

J. AV.POWBLL, DIRECTOR

GEOLOGICAL RECONNO-ISSANCE

NORTHWEST WYOMING

BY

GEORGE HOMANS ELDRIDGE

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1894

CONTENTS.

Page.

Letter of transmittal ....................................................... 9

Preface..................................................................... 11

Geographic position......................................................... 13

Topography ................-.-...I............................................ 13

Inclosing ranges........................................................ 13

Basins.................................................................. 16

General geology ......................................^..................... 17

Formations............................................................. 17

Structure............................................................... 29

Economic geology........................................................... 49

Coal.................................................................... 49

Stratigraphy........................................................ 49

Areas.............^................................................. 50

Chemical analysis (table)........................................... 61

Petroleum.............................................................. 63

Building materials: stone, clay, lime, gypsum........................... 66

Gold.................................................................... 66

Hot springs............................................................. 67

Agriculture............................................................. 68

5

ILLUSTRATIONS.

Pago. 

PL. I. Geologic map of northwest Wyoming ....................... Frontispiece.

II. Sections of coal seams.............................................. 49

III. Sections of coal seams.............................................. 54

IV. Sections of coal seams .............................................. 56

FIG. 1. Section showing relative positions of coal seams at Red Lodge,

Montana ......................................................... 53

7

LETTER OF TRANSMITTAL.

DEPARTMENT OF THE INTERIOR,

U. S. GEOLOGICAL SURVEY, 

DIVISION OF GEOLOGY AND PALEONTOLOGY,

Washington, J). C., March 6, 1894.

SIR: I have the honor to transmit herewith my report of a reconuoissance in northwest Wyoming, made during the summer of 1893, 

and authorized by you under date of July 1, 1893. 

Very respectfully,

GEO. H. ELDRLDGE,

Geologist. 

Hon. J. W. POW-ELL,

Director, U. S. Geological Survey.

PREFACE.

The reconnoissance which forms the basis of the following report 

was authorized with special reference to the coal resources of the Big 

Horn basin in northwest Wyoming. Incidentally regions adjoining 

were to be included, and such examinations as time permitted were to 

be made for oil, building stones, and other economic materials. The 

route of reconnoissance was, therefore, controlled by these conditions, 

and many areas could be examined only in a most general way. The 

southeastern portion of the area mapped was beyond reach, and for 

this the reports of the Territorial geologists and the maps of the early 

Hayden Survey were freely consulted.

Formation lines, except in the southeastern area, are drawn upon 

the map solid or broken, according as the respective portions have 

been approximately determined by direct observation or still remain 

uncertain 5 in the southeast the solid portions have been traced from 

the early maps and descriptions, while uncertainty is indicated by a 

broken line.

As a base for the geology the map of the U. S. General Land Office, 

edition 1892, has been employed, but it leaves much to be desired 

respecting accuracy, particularly as regards stream courses. No other 

maps of the region, however, exist, excepting the Hayden sheets in 

the southern part.

11

A GEOLOGIC RECONNOISSANCE IN NORTHWEST WYOMING, WITH SPECIAL REFERENCE TO ITS ECONOMIC 

RESOURCES.

BY GEORGE H. ELDRIDGE.

GEOGRAPHIC POSITION.

The area of Wyoming covered in this reconnoissance lies between 

meridians 106° 30' and 109° 30' W. and parallels 42° 45' and 45° 

N. about 150 by 150 miles, or 22,500 square miles. The examination, 

however, extended about 15 miles across the Montana-Wyoming line, 

making a total area of 24,750 square miles. (PI. I.)

Four important towns lie within this region: Sheridan and Buffalo in 

the northeastern portion; Bed Lodge, in Montana, in the northwestern; 

and Lander in the southern. Besides these, are two army posts: Fort 

McKinney and Fort Washakie, the former 3 miles west of Buffalo, the 

latter 16 miles northwest of Lander. Sheridan and Bed Lodge have 

railroad communication with the East and West, the former by the Burlington route, the latter by the Northern Pacific Railroad.

In the southern part of the region is the reservation of the Shoshone 

and Arapaho Indians, in area 60 by 66 miles, or 3,960 square miles.

TOPOGRAPHY.

The topographic features of the region are two structural valleys, 

the Big Horn and Wind River basins, each nearly inclosed by high 

mountain ranges: the former basin, however, is separated from the 

country to the north by only a gentle rise; the latter from the valley 

of the Platte by a low divide of complex structure. The Wind Biver 

passes by a deep gorge in the Owl-Rattlesnake Range into the Big 

Horn basin, where it becomes the Big Horn River, flowing thence to 

the.Yellowstone valley through one of the most rugged and impassable 

canyons of the West.

INCLOSING RANGES.

The Roclcy Mountains. The Rocky Mountains border the region on 

the west and southwest. Their eastern slopes are deeply cut by four 

large streams, Clarks Fork, Stinking Water, Grey Bull, and Wind

13
14 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

Biver. The general mass is divided into three subordinate ranges, 

Absaroka, Shoshone and Wind Eiver.

The Absaroka Eange extends from the Stinking Water, 50 or 60 miles 

south of the Montana-Wyoming line, northward to the Yellowstone 

Eiver. It occupies the eastern portion of the Yellowstone Park 

Eeserve and constitutes in part the watershed of the Yellowstone 

Eiver, Clarks Fork, and the Stinking Water, but does not enter into 

the formation of the continental divide. The configuration of the 

range in the interior and more elevated portions is that of a. lofty mass 

of castellated peaks and ridges and cliff-bound canyons, carved out of 

horizontal beds of breccias and conglomerates, while at lower altitudes 

and adjacent to the prairies the topography is characteristic of an 

Archean core, fringed by sedimentary formations dipping usually 

between 45° and 90° B. or RE. Occasionally, secondary parallel ridges 

skirt the base of the main range, the result of minor folding.

The Shoshone Eange lies between the Stinking Water and WindEiver 

valleys. It enters only slightly into the formation of the continental 

divide, but sends from it to the northeast and southeast two rugged 

and almost impassable ridges, that to the southeast being the more 

important. The spur to the northeast has the subordinate name of 

Meeteetse Mountain. Like the more elevated part of the Absaroka 

Eange, this is a confused mass of castellated peaks and ridges in 

the breccias and conglomerates which extend southward from it; this 

configuration is maintained to the mountain front. A broad belt of low 

foothills succeeds, composed in the main of the remnants of early folds, 

parallel in trend with the range front and belonging to the transition 

zone between prairie and mountain structure.

The Wind Eiver Eange is one of the highest and most rugged seg;- 

nients of the Eocky Mountains. It has a general northwest trend, and 

extends from the Tukwatika1 Pass to a point a little southeast of Lander, constituting for nearly its entire length the continental divide. 

The topographic aspect of the range is that of a great anticlinal fold 

with an exposed core of Archean rocks and a bordering zone of sedimentaries of more of less steep dip, reaching an altitude of 1,000 and 

2,000 feet above the mountain base. The range is deeply cut by mountain streams, and across their cany on mouths may be observed in many 

instances the terminal moraines which mark the extent of early glaciers. 

The Big Horn Range. This is a lofty anticline about 100 miles east of 

the Eocky Mountains. The trend varies from N. 10° E. at the southern 

end to northwest at the northern, near the Montana-Wyoming line. 

The general altitude is between 7,000 and 8,000 feet, or 3,000 to 4,000 

feet above the prairies to the east. Elevations between 8,000 and 9,000 

feet, however, are frequently encountered, and the principal point,

'Tukwatikaor Tukwarika, "MountainSheep Eaters." This, according to Dr. Hoffman.of theTJ. 

S. Bureau of Ethnology, is the name of a band of Shoshone Indians. It has long been applied to the 

pass in question, but on existing maps is spelled "Twogwotee,e," a form not as acceptable as that 

adopted in the text.
ELDEIDGE.] TOPOGRAPHY. 15

Cloud Peak, reaches a height of about 13,500 feet. In topography the 

range is an instance of a broad, flat, anticlinal arch presenting an 

Archean core within sedimentary formations which dip more or less 

steeply from the center. The summit of the range is from 10 to 25 miles 

wide. The higher peaks, of crystalline rocks, occur midway its length, 

while beyond these the surface is undulating or studded with low buttes 

and ridges, the uneroded remnants of Paleozoic quartzites, limestones 

and shales. The drainage of the summit is peculiar in the long north 

and south courses pursued by the streams before they break through 

the rim to fall rapidly to the prairies below 5 this is due to the frequency 

of minor folds and faults running with the range, by which the early 

channels were directed. The scenic features of the Big Horn Mountains are remarkably beautiful. On the summit broad grassy parks 

exist in picturesque contrast with extended masses of heavy timber j 

and on the slopes of the range are wild canyons with swift-flowing torrents, broken at the rim of the upturned sedimentaries by cascades 

over hard Archean granites, the whole in the midst of boldest crags 

which tower high on the mountain face.

The divide letiveen the Big Horn basin and the valley of the Yellowstone. This is in the main low and developed largely by what may be 

termed the accidents of erosion, although primarily determined by a 

gentle anticline. At the eastern end the divide passes into the Pryor 

Mountains; at the western, into a projecting spur of the Absaroka 

Eange. The trend is irregular, particularly in the middle section, 

where folding has been slight and erosion the chief factor in development. Five or six miles from the western end is the sharp double 

peak of Heart Mountain, an isolated hill rising from 1,000 to 1,200 feet 

above the general prairie level, and constituting a landmark visible 

from all parts of the basin and its rim.

The Pryor Eange, at the eastern end of the divide, attains an elevation between 7,000 and 8,000 feet. Structurally it is the northwestern 

extension of the Big Horn Mountains, from which it is separated by 

the Big Horn Canyon and the valley in its immediate vicinity. The 

range is twinned by a northwest to southeast strike fault, the gentler 

slopes of both ridges being to the west. The northeast ridge is the 

greater, and a little distance from its northwestern end is cut by the 

gorge of Pryor's Fork. The southwest ridge terminates at the head of 

Sage Creek, a tributary of the Stinking Watei0 rising opposite Pryor's 

Fork. The Pryor Range disappears at the north and west by a gradual sinking of its axis, but a large area of the country is maintained 

at a considerable elevation above the prairies along the Yellowstone.

The Owl and Rattlesnake Mountains. These form the southern side 

of the Big Horn basin and separate it from the Wind River valley 

beyond. They extend from the Shoshone Range to the southern end 

of the Big Horn Mountains, the general trend of the chain being N. 

50° to 60° W. The Owl Mountains lie to the west of the Wind River 

Canyon, the Rattlesnake Mountains to the east.
16 GEOLOGY NOETHWEST WYOMING. [BULL.IW.

The Owl Mountains have the appearance at their crest of a series of 

ridges diagonally placed with reference to the general trend of the 

range and rising from 400 to 500 feet above intervening depressions. 

This appearance is brought about by a series of anticlinal folds possibly with an occasional fault of which the trend is approximately 

northwest or slightly diagonal to that of the range as a whole. This 

structure is locally continued to both north and south slopes of the 

range, producing a series of subordinate ridges in a position en echelon 

with reference to one another. The altitude of the range is probably 

between 6,000 and 7,000 feet, or 2,000 to 3,000 feet above the general 

level of the valleys on either side. The southern slope is the more 

precipitous, the northern being gentle and deeply cut by canyons a 

condition also existing on the southwestern or gentler slope of the 

Pryor Mountains.

The Rattlesnake Range unites the Owl and Big Horn Mountains. 

It is an anticline, with a precipitous slope to the south, the northern 

being gentle and considerably cut by erosion. Upon the latter slope 

the several members of the Cretaceous extend well up toward the summit rim.

The divide between the drainage of the Wind and Platte rivers. This 

is low and is in part structural and in part the accident of erosion.

BASINS.

The Big Horn basin. The topographic features of this area are mainly 

those of the well known " Bad Lands" of the West. The outcropping 

strata are clays and sandstones, the former predominating. Gray is the 

prevailing color, but white, purple, pink and black, in bands, also occur. 

The surface is a plain, relieved by buttes and ridges and by the broad 

bottoms of the larger streams and their tributary gullies. The configuration is the result of erosion, or of erosion combined with structure, 

the latter being the case in the numerous anticlinal ridges, from 1 to 30 

miles in length, which occur within a belt of 5 to 15 miles along the 

inclosing ranges. Valleys now occupy the longitudinal axes of many 

of these folds and sharp incisions cross them. In the interior of the 

basin the ridges are more the result of erosion alone, and, with the 

buttes, occur without system; here, too, both ridges and buttes may 

consist wholly of clay, when they are sharp crested or pointed, or they 

may be capped by sandstone, becoming tabled. The height of the elevations is between 100 and 500 feet above the general bench levels, the 

stream bottoms being from 50 to 200 feet below. The general altitude 

of the basin is about 4,000 feet. Areas of great fertility exist about the 

periphery of the basin in the portions of the valleys occupied by the 

clays of the Montana Cretaceous. These tracts are often several iuiles 

in width and length, and in certain localities they are repeated two 

or three times from structural causes, increasing materially the total 

area available for agriculture.
FORMATIONS :ARCHEAN, CAMBRIAN. 17

The topographic features of the Big Horn basin extend across the 

divide to the 01 arks Fork valley.

The Wind River basin. The area from Torrey's Fork east is, with 

the exception of the bottoms of the main streams and a narrow zooe 

along the base of the inclosing ranges, a barren waste of sand, clay 

and grit, relieved in configuration only by an occasional butte or the 

shallow depressions of its dry stream courses. Nearly all of its water 

is carried well toward the southern side, the Wind Biver Range affording almost the only supply. This edge of the basin has many fine 

streams and broad valleys, presenting large tracts of valuable agricultural land. Crow Heart and Pavillion buttes are the prominent landmarks of the basin. Thirty to forty miles above the former the valley 

begins to narrow, the topography of the Wind River Range prevailing 

to the head on the south, while on the north the Shoshone Range presents its bold cliffs and deep gorges carved in horizontal beds of breccia.

GENERAL GEOLOGY. 

FORMATIONS.

The Archean. The Archean consists of granites, gneisses and 

schists of various types. It forms the cores .of the Big Horn, Wind 

River, Absaroka and Owl-Rattlesnake Ranges. The area of exposure 

varies in the different ranges, depending upon the conformation of the 

folds, the amount of reduplication, the degree of erosion, and the cover 

of late Tertiary conglomerates and breccias of eruptive material. On 

th'e summit of the Big Horn Range the Archean forms the bottoms 

of many beautiful parks, and towards the central portion of the range 

enters into the structure of the higher peaks. In the latter case it is 

cut by eruptive bodies of considerable importance. In the Wind 

River and Absaroka Ranges the area of Archean is very extensive, 

while in the Shoshone Mountains it is reduced to a minimum, if, indeed, 

there is a single exposure. The condition in the Shoshone Range is 

brought about by heavy deposits of eruptive breccias and conglomerates, which not only cap the highest peaks but extend in long ridges 

quite to the front of the range and prairie border. In the Owl-Rattlesnake Range, in addition to the main exposure, an independent outcrop of Archean occurs further to the west, induced by erosion of a 

sharp anticlinal fold or denudation along a possible fault line, in direction somewhat diagonal with the general trend of the range.

The Cambrian. This consists of a series of shale, sandstone, grit, 

conglomerate and limestone, the shale and sandstone locally having 

the general composition and hardness of quartzite, and also containing 

a variable, though always small, amount of lime. The material at the 

base of the formation is usually coarse, constituting the chief conglomerate of the series 5 in many instances it is apparently derived from 

Bull. 119 2
18 GEOLOGY NORTHWEST WYOMING.

the neighboring Archean, but not infrequently there is found the white 

quartzite and quartz conglomerate so common in the Colorado areas 

of Cambrian, the source of which is possibly somewhat more distant. 

The color of the arenaceous or quartzitic members varies from darker 

brown to gray, white, or, locally, red or green, but the first predominates.

The shales, which are greenish gray or brown, constitute by far the 

larger part of the formation, the sandstones and grits being distributed 

from base to summit of the series, in beds 2 to 20 feet thick, in the Big 

Horn Eange an especially prominent zone occurring about midway.

The limestones are impure and occur in thin beds at a few horizons 

only. The entire series contains disseminated grains of the green 

silicate of iron (glauconite) which is now recognized as characteristic 

of the Cambrian throughout the Eocky Mountain region.

The thickness of the formation varies from a few feet with possibly 

entire absence in one or two localities to about 900 feet, the region of 

minimum development being the Owl Mountains, that of maximum the 

canyon of Clarks Fork. On the eastern slopes of the Big Horn 

Eange, in the canyon of Big Goose Creek, the estimated thickness is 

from 400 to 600 feet, which is maintained over the greater portion of 

this range.

The fossils of the Cambrian within the region examined are doubtless far more numerous than casual search revealed, but aside from 

a few trilobites no attempt at collection was made.

The Cambrian exposures are confined to the mountains. The formation occupies considerable areas of the summits of the Owl and Big Horn 

ranges, while in the Absaroka and Wind Eiver Mountains it is confined 

to the lower slopes. On the summit of the Big Horn Eange it forms 

numerous low buttes which rest upon the Archean floor and are usually 

capped by the lowermost strata of the Silurian.

The Silurian. Overlying the Cambrian, the upper limit of which is 

somewhat arbitrarily taken at the top of the shales, are several hundred 

feet of limestone and quartzite in which it is difficult to trace a definite 

line of division but approximately the lower half of which is of Silurian 

age, and the upper half, Subcarboniferous. The Silurian series presents three varieties of rock: a peculiar, laminated, pebble-bearing 

limestone at the base, and light colored cherty limestones and white 

quartzites, overlying to the summit.

The basal limestone is from 50 to 100 feet thick. Some of its layers 

abound in lenticular pebbles, also of limestone, in size minute up to 

1 or 2 inches in maximum diameter. The colors are green, greenish 

gray, purple or purplish brown. The layers devoid of pebbles are 

crystalline in texture and delicately laminated, the color changing 

with the laminations j their hardness also varies, causing the rock to 

weather in delicate corrugations. The matrix of the pebbly layers is 

simi|ar to the above. The texture of the pebbles is homogeneous, the
KLDBIDOE.] FORMATIONS SILURIAN, CARBONIFEROUS. 19

grain very fine; the prevailing color is green without, gray within. 

The pebbles lie both with the lamination planes and across them. 

Pebbles and matrix are of equal hardness, the rock fracturing across 

both alike. The presence of this series is general in the mountains 

bordering the Big Horn basin.

The nature of these pebble-limestones seems to be that of an intraformational conglomerate, the pebbles having been formed shortly after 

deposition of the original material by the breaking up of the bed, and 

settling in their new positions in the midst of fine calcareous matter 

brought down at the same time.

The chert-bearing limestones form the mass of the Silurian series. 

They occur in heavy beds of 50 to 100 feet and are white to light gray, 

mottled purple or brown. Locally they contain a varying amount of 

quartzose matter, by reason of which they not infrequently graduate 

into true quartzite, and vice versa. Limestones of this appearance and 

nature characterize the Silurian throughout the Eocky Mountain region.

The Silurian quartzites are usually pure white and of considerable 

uniformity of texture. In the region examined they are distributed 

throughout the chert-bearing limestone in beds from 1 to 30 feet thick, 

but in several localities in the Eocky Mountains concentration into 

one or two heavy beds has been observed.

The thickness of the Silurian over the field examined varies. In the 

Big Horn Mountains it is estimated at about 600 feet 5 on darks Fork 

at 1,000 feet; in the Owl-Eattlesnake Eange there is marked diminution 

with, possibly, even total disappearance at one or two localities; in the 

Wind Eiver Mountains a thickness of 1,000 feet is again attained.

Characteristic fossils were obtained from a layer within 75 feet of the 

probable top of the formation.

The area of Silurian in the Big Horn Mountains is little less than 

that of the Cambrian; the lower members of the formation, having 

escaped erosion, cap many of the buttes on the summit, while there 

is a general rim of both quartzites and limestones about the whole 

periphery of the crest. In the Absaroka Eange the formation is chiefly 

confined to the loAver slopes, extending to higher altitudes only to the 

south of Clarks Fork, and in the vicinity of the Stinking Water, where 

additional area of exposure has been acquired by the presence of minor 

folds parallel with that of the general uplift. In the Wind Eiver Eange 

the conditions of outcrop and exposure are relatively the same as in the 

Absaroka. In the Owl-Eattlesnake Mountains the Silurian area is not 

extensive except in the immediate vicinity of the Wind Eiver Canyon, 

where erosion has been carried to a degree that has left it the superficial rock over much of the crest. In the Pryor Mountains the delineation of the Silurian was undetermined, but it doubtless appears in the 

canyon of the Big Horn Eiver, and possibly just Avest of the fault line 

in the valley separating the two ridges of which the range is composed.

The Carboniferous. This embraces both divisions usually found in' 

the West the Subcarboniferous and the Coal-measures.
20 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

The Subcarboniferous includes the upper half of the great Paleozoic 

series of limestones and quartzites of which the lower half has been 

described as Silurian. Not more than 50 feet above the horizon 

regarded as the probable base of the formation characteristic fossils 

are found, while the upper limits are equally well denned by a sharp 

change in sedimentation. The thickness of the series varies between 

300 and 1,000 feet, the maximum being attained in the Absaroka and 

Wind Biver Ranges, the minimum and average occurring in the OwlRattlesnake Mountains and in the Big Horn Range respectively.

The mass of the Subcarboniferous is limestone, divided into two 

or three varieties. In the region of the Big Horn Mountains there are 

two: the upper, the typical, massive "blue limestone" of the Rocky 

Mountains; the lower, a bedded, white, quartzite-bearing limestone, 

resembling that of the upper portion of the Silurian. In the region of 

Clarks Fork Canyon in the Absaroka Range, the quartzite is at a 

minimum and the limestone, which is of a more decided gray than usual, 

occurs in two or three broad bands separated by 50 to 100 feet of thin 

bedded limestone of reddish hue. The whole series is locally more or 

less ferruginous, while the blue limestone proper is also frequently 

cavernous. The beds occur in either one or two pronounced benches 

or with the Silurian form an unbroken cliff from base to summit.

The distribution of the Subcarboniferous includes the slopes of most 

of the great ranges bordering the Wind River and Big Horn basins, 

and, within the latter basin, the central terrane of the Sheep Mountain anticline a long, low ridge near the eastern side of the basin 

and the crest of Heart Mountain, near the western end of the divide 

between Clarks Fork and the Stinking Water.

The Coal-measures of the Carboniferous are the most variable of the 

formations within the present field. The series is most complete along 

Big Goose Creek in the Big Horn Mountains where the following beds 

are present: at the summit, 60 to 80 feet of white sandstone, in two 

benches, a red layer of 5 or 10 feet between; for 130 feet below this, thin 

beds of limestone, quartzite and shale, all more or less noncontinuous 

and shading into each other; beneath this, 20 feet of limestone in thin 

layers, some of which are white and very pure, others brown and more 

or less quartzose; shales with narrow quartzites and limestone now succeed for 60 feet; finally, the lowest bed consists of 40 feet of deep red 

sandstone with a few very thin beds of limestone interlaminated. The 

last rests directly on the Subcarboniferous.

Of the foregoing series the most important bed, both from general 

occurrence and the determinative value attached to it, is the heavy 

sandstone or quartzite at the top. This forms the outer rim of the 

Paleozoic measures in all the lofty ranges about the Big Horn and 

Wind River basins, except the Shoshone. The remainder of the series 

between this and the blue limestone is not only very variable, but, as 

in the section at Clarks Fork Canyon, locally disappears. At many
KLDRIDQE.] FORMATIONS TEIAS, JURA. 21

points, however, and in the Big Horn Eauge especially, the prominent 

red sandstones at the base are present, and afford a ready means for 

identification of stratigraphic horizons. In the Wind Eiver Eange the 

quartzite is present, but the general constitution of the Coal-measures 

differs from that elsewhere in having a greater proportion of shale.

The distribution of the Coal-raeasures follows that of the Subcarboniferous.

The Trias. 1 This is represented wholly by the well known "Eed 

Beds" of the Eocky Mountains heavy bedded, bright red sandstones 

and conglomerates, the former often of fine, even texture and uniform 

color, the whole consisting of quartzose and other Archean-derived 

material and being somewhat ferruginous. The upper 50 to 75 feet are 

usually more thinly bedded and carry a few narrow bands of limestone, 

constituting a transitional zone, to the overlying Jura. The thickness 

of the Trias varies approximately between 300 and 1,000 feet.

The folding and erosion that have taken place in the localities of the 

subordinate anticlines which parallel the main ranges have exposed 

much greater and more numerous areas of the Eed Beds than would 

have been shown under circumstances of greater regularity. As a consequence, therefore, the Trias not only skirts the base of the more lofty 

ranges in zones of greater or less width according to the degree of dip, 

but occupies considerable areas in the basins themselves. Prominent 

among these areas in the Big Horn basin are the Sheep Mountain and 

Five Spring ridges on the east, the southern extension of the Eattlesnake Eidge a spur of the Absarokas on the west, and the region 

along the. northern base of the Owl-Eattlesnake Eange, in which both 

minor folds and gentle dips on the mountain slope itself have added 

materially to the breadth of outcrop. Other localities in the basin 

where the area of Eed Beds is thus considerably increased are the southwestern base of the Pryor Mountains, and the western base of the Big 

Horn Eange both in the vicinity of the Big Horn Canyon and between 

No Wood Creek and the main range. In the Wind Eiver basin, in the 

vicinity of Fort Washalde and the town of Lander, are two very prominent anticlines parallel with the Wind Eiver Eange at a distance of 12 

to 15 miles from its base, and on the southern spurs of the Owl Mountains adjoining the Shoshone Eange, in the northwestern portion of the 

Shoshone Eeservation, are several other folds en Echelon with one another where extensive exposures of Eed Beds exist.

The Jura. 1 This, so far as the evidence obtained indicates, is, 

within the region under examination, wholly of marine origin. The 

thickness is between 400 and 600 feet, \vhich is approximately maintained over the entire area of exposure. Shales constitute the mass 

of the formation in which from base to summit occur thin bedsof sandstone and fossiliferous limestone of types characteristic of the Jura in 

the Eocky Mountain region. Gray is the predominating color of the

1 In the text Jnra corresponds to Upper Jura-Trias of map; Trias, to Lower Jura-Tria8.
22 GEOLOGY NORTHWEST WYOMING. [nuM,.H9.

shales, but throughout the formation red, purple, yellow, slate and pink, 

in greater or less intensity, may be observed. At a number of localities 

a considerable amount of siliceous matter appears, in occurrence suggesting the action of hot waters.

The sandstones are of slight importance. They are chiefly gray with 

a slightly greenish tint. The lower beds, however, are red, shaly, and 

transitional from the Trias, while near the summit are two of greater 

thickness, which, but for their tint and the overlying typical Jura shales, 

might be confounded with the Dakota.

The limestones are nearly all fossiliferous, and of the drab color 

peculiar to the Jura in the west. In thickness they vary from a few 

inches to 15 feet. Three or four in the lower 100 feet and one or two 

in the upper third of the formation are especially prominent.

The distribution of the Jura is approximately that of the/Trias, the 

one succeeding the other in all localities.

The Dakota. As elsewhere in the Northwest, this is essentially a 

formation of quartzose sandstone with a few minor layers of shale or 

clay which locally become somewhat carbonaceous or, perhaps, take 

on the nature of a fire-clay. The sandstone is gray, but usually tinged 

yellow, red or brown from the presence of iron. At the base of the formation is a layer of conglomerate in which pebbles and matrix are more 

or less silicified, a feature also characteristic of the formation in other 

parts of the West. Plant remains occur.

The thickness of the Dakota varies, but is generally less than 100 feet. 

In the region of Five Spring Creek, at the western base of the Big Horn 

Eange, the formation is entirely absent, the black shales of the Benton 

resting directly upon the variegated clays of the Jura. This is, however, 

a local occurrence, and within 3 or 4 miles of the base of the range the 

formation reappears, first in a clearly recognizable layer hardly G inches 

in thickness, then gradually increasing westward until a general thickness of 50 feet is attained. The phenomenon is apparently one of nondeposition.

The Colorado. The component members of the Colorado the Benton 

and Niobrara formations are grouped under one color on the map, 

their line of division being too indistinct to permit separation.

The Benton is a body of leaden gray and black shales carrying a few 

thin bands of limestone and numerous small, lenticular ironstones. The 

formation maintains the general features that characterize it throughout the West. Its thickness is between 300 and 600 feet.

The Niobrara consists largely of light gray shales, but it also carries some impure, shaly limestones, a characteristic sandstone locally 

developed, and an equally remarkable conglomerate in which the 

pebbles are of black chert in one or two places mingled with more or 

less eruptive debris. The thickness varies from 300 to 800 feet.

The shales constitute a broad, light colored zone between the darker 

clays of the Benton and Pierre. In general they are soft, friable and 

earthy, but there are layers more especially associated with the local
BLDRIDOB.] FORMATIONS COLORADO, MONTANA. 23

sandstones and conglomerates, which are of extremely close grain and 

of fine even texture, indurated in a marked degree, and which, though 

gray on fresh fracture, weather a characteristic milky white. They 

occur in bauds from 1 to 3 feet thick.

The limestones are not of a pronounced character, but rather are 

calcareous layers of the shale, which are held together with greater 

tenacity than portions containing less lime. These layers are rarely over 

a foot or two thick, are very earthy and are usually of a fine texture. 

They contain numerous inolluscan casts, poorly preserved.

The sandstones are white, stained yellow or brown from the presence 

of iron, and they carry an occasional ferruginous concretion from 1 to 3 

feet in maximum diameter. They are especially well developed along 

the front of the Absaroka Eange in the vicinity of Clarks Fork, here 

attaining a thickness with the associated conglomerates of 50 feet. 

There are apparently two horizons of these sandstones one 200 feet 

above the base of the formation, another at the summit. The sandstones 

are either massive or divided into layers 1 to 6 feet thick.

The conglomerates have a matrix of sand, but the pebbles are chiefly 

black chert, averaging half an inch in diameter, in some places sparsely 

scattered through the rock, in others constituting almost its entire mass. 

Mingled with the chert pebbles are others of eruptive material; these 

are especially abundant in the vicinity of Clar-ks Fork. The pebbles 

of the Niobrara conglomerates, particularly those of black chert, are 

characteristic of the formation for the region examined and afford ready 

identification of the geologic horizon.

The sandstones of the Mobrara in the Clarks Fork region are leafbearing, affording the only instance within the United States in which 

this formation has been found to contain plant remains.

The Niobrara occurs not only in the regular succession of beds along 

the base of the several mountain ranges but includes numerous areas 

in the basins proper, where it occupies the center or rim of most of the 

subordinate anticlines about their peripheries. Notable among these 

anticlines are several along the west base of the Big Horn Eangej 

others very extensive north of the Owl Mountains, having a N. 60° W. 

trend; a number in the region between Wood Eiver and Stinking 

Water, of a general north-northwest direction; portions of the general 

divide between the Big Horn basin and the Yellowstone valley; and, 

in the Wind Eiver valley, several along the Wind Eiver Eange, and 

others extending in a southeasterly direction from the Owl Mountains.

The Montana. This embraces the Pierre and Fox Hills formations, 

which, by reason of their gradual passage one into the other, it has 

been impossible to separately delineate upon the map.

The Pierre is composed entirely of dark, leaden gray clays, which 

carry numerous concretions of limestone, averaging 2 to 3 feet in 

diameter. These concretions are often veined with calcite seams, and 

easily break into angular fragments; they are fossiliferous, affording 

many typical Pierre forms.
24 GEOLOGY NORTHWEST WYOMING. [BULL. no.

The Pierre outcrops over a much greater area than any of the older 

formations. This is due to the low degree of dip beyond the immediate base of the mountains, to the many gentle anticlines mentioned, 

and to the general level of erosion attained at the present day. In the 

Wind Eiver valley broad areas of Pierre exist both on its northern and 

southern sides. In the Big Horn basin the Pierre occupies a broad 

belt along the base of the inclosing ranges, locally, however, as along 

the base of the Absaroka Bange, contracted by reason of its steeper 

dip. East of the Big Horn Eange the formation again occurs at a comparatively gentle dip, 10° to 20°; here, opposite the Laramie, its area of 

exposure is from 3 to 5 miles wide, while to the south of this formation 

it is reported over a much more extended stretch of prairie. The thickness of the Pierre is probably between 1,000 and 2,000 feet, but no actual 

determination was made.

The Fox Hills was not definitely recognized in the present field of 

exploration. Towards the top of the clays which constitute the Montana series the material locally becomes a little sandy, but no heavy 

beds of sandstones, such as mark its summit in many western localities, 

appear, and no fossils characteristic of the horizon were obtained.

The Laramie. This is a series of alternating sandstones and clays, 

with seams of lignite or coal at various horizons from base to summit.

The clays as a rule predominate. They are gray, and often bear plant 

remains or carbonized particles of wood sufficiently abundant to stain 

layers of them a brownish hue, or to impart to thin beds a more or less 

lignitic character. They frequently carry concretionary bodies of indurated sandstone, and in a single locality one mile below the town of Eed 

Lodge, on Eocky Fork, in Montana limestone concretions from 1 to 6 

feet across, containing leaf and wood impressions. The latter concretions resemble those of the Pierre in texture and fracture, but are 

yellowish gray and are associated with lignite-bearing beds.

The sandstones are almost wholly composed of quartz grains, of 

medium size. The normal color is gray to white, but a variable amount 

of iron locally imparts a brownish tint. The beds vary in thickness 

from 1 to 50 feet, those of 20 to 30 feet being of common occurrence. 

They are of considerable persistence, particularly those of the lower 150 

to 200 feet. As n, rule the lower beds form prominent outcrops, whether 

their position is vertical or but slightly inclined. Leaf impressions are 

common.

The clays and sandstones of the Laramie in the Big Horn and Wind 

Eiver basins and the Olarks Fork valley are segregated into two broad 

divisions: the lower, 300 to 500 feet, composed chiefly of the sandstones; 

the upper, 400 to 600 feet, of the clays. East of the Big Horn Mountains 

this separation is not nearly so pronounced.

The thickness of the Laramie varies from a few feet to 1,000, or possibly over. The maximum thickness is attained beneath the prairies 

oast of the Big Horn Mountains, the minimum along the base of the
ELDRIDGE.] FORMATIONS LARAMIE, LIVINGSTON, WASATCH. 25

Absaroka Eange immediately south of Clarks Fork, where but a few 

feet now separate the Pierre from the overlying Wasatch. At other 

points the average thickness of at least 600 or 700 feet is maintained. 

The extreme thinness in the vicinity of Clarks Fork is due to denudation from the summit prior to deposition of the younger formations.

The area of exposed Laramie is extensive. Bast of the Big Horn 

Mountains it reaches fully half of the distance to the Black Hills, 

while to the north and west it constitutes the surface formation over 

much of the Yellowstone and Clarks Fork valleys. It underlies horizontally the Tertiary formation in the central portion of the Big Horn 

basin, and outcrops with gentle dip in a broad belt about its periphery. 

In the Wind Eiver valley it appears from beneath the later beds in 

detached masses at the base of the inclosing ranges, and probably 

Underlies the greater portion of the basin area.

Succeeding the Laramie in chronological order in the Big Horn and 

Wind Eiver basins are the equivalents of the Wasatch and Briclger 

formations of an area further south, with possibly a third series of beds 

belonging to the Livingston, a formation of recent identification in 

Montana The last has been assigned to the Cretaceous, while the 

first two belong to the Eocene Tertiary. Each at one point or another 

rests directly upon the Laramie, at the top of which is one of the 

greatest unconformities known.

The Livingston. This formation, on account of its uncertain occurrence, will not here be discussed beyond the remark that in its recognized localities to the northwest of the present field it consists of a 

series of sandstones, grits, conglomerates and clays, made up very 

largely of the debris of andesitic lavas and other volcanic rocks and 

including local intercalations of volcanic agglomerates.'

The Wasatch. This is a series of clays with occasional beds of sandstone and local conglomerates, the thickness variously estimated from 

1,000 to 2,000 feet.

The clays are chiefly gray, but are banded white, buff and red, the 

reds being most conspicuous, and, taken with the composition of the 

beds and their stratigraphical position, a characteristic and determinative feature of the formation. Small calcareous concretions, more 

or less ea.rthy, occur throughout the clays; these are fossiliferous.

The higher sandstones in the series are argillaceous and generally 

weather in slopes uniform with the clays. Occasionally, however, purer 

layers occur, which are more resisting and outcrop in ledges that break 

the otherwise monotonous descents. Towards the base of the formation 

the sandstones are usually more pronounced and the lower layers may 

become coarsely conglomeratic. This is especially the case in the 

vicinity of Clarks Fork Canyon, along the foot of the Absaroka Eange, 

where there are 600 or 700 feet of conglomerates, grits, and sandstones,

1 The Laramio and the overlying Livingston Formation iu Montana, by W. H. Weed. Bull. 105, 

U. S. Geol. Surv., p. 21.
26 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

all more or less ferruginous. The pebbles constituting the conglomerates vary in size up to 6 or 8 inches in diameter, and consist chiefly of 

limestones, qnartzites, and sandstones derived from the older sedimentary formations of the neighboring mountains; a small quantity 

of Archean de"bris is also present. Towards the top of the conglomerates or sandstones are intercalated thin beds of red clay, similar to, 

but passing with gentle easterly dip beneath, those so conspicuous 

further out in the basin. The conglomerates rapidly disappear to the 

south of Clarks Fork Canyon, but to the north continue beyond the 

Montana line, where, however, their relations to other formations were 

nob investigated. In this direction, as the series is ascended, the material becomes finer, and the 5 or 6 miles of prairie along the MontanaWyoming line next the range is, chiefly occupied by grits and sandstones, with a minimum of the coarser constituents.

The beds which are here described as Wasatch have been studied 

jointly by Prof. H. F. Osborn and Dr. J. L. Wortman1 with reference 

to their fossil mammalia. These have been found practically the same 

as those that characterize the Vermilion Creek beds of the Fortieth 

Parallel Survey, while lithological identity is apparent from the foregoing description. 'There is, therefore, no doubt as.to the propriety of 

referring the series to the Vermilion Creek or Wasatch Eocene, the 

lowest division of the western Tertiary.

The Wasatch beds occupy a broad area in the central portion of the 

Big Horn basin. They have been traced and identified, both lithologically and by their fossils, in the Clarks Fork valley and northward to 

the Montana line, and they appear from beneath the lower Bridger 

beds in certain localities in the Wind River valley.

In the Big Horn basin they constitute the prominent McCullocks 

Peak, near the western edge of the formation, from here passing northward into the eastern spurs of Heart Mountain, and beyond into the 

bluffs of Pat O'Hara Creek and the hills on both sides of the Clarks 

Fork valley, in the vicinity of the canyon of the latter stream approaching within a half mile of the base of the range. South from McCullocks Peak, between the Stinking Water and Grey Bull, their western 

boundary lies at a distance of 10 to 15 miles from the base of the Shoshone Range. The formation appears in the high bluffs southeast 

of Meeteetse, and continues southward to the region of Twentyon£ or Upper Cottonwood Creek, where its outcrop turns to the east 

and passes across the Big Horn basin on an irregular? line 10 to 15 miles 

from the base of the Owl-Rattlesnake Range. East of the ±>ig Horn 

River the series of clays again appears in a high ridge in the forks of 

this stream and No Wood Creek. The eastern line of the formation 

recrosses the Big Horn near the mouth of No Wood, and passes north1 Fossil Mammals of the Wasatch and Wind River beds, collection of 1891, by Henry Fairfield 

Osborn and J. L. Wortman. Bull. Am. Mus. Nat. Hist., Vol. IV, 1892, Art. XI, p. 81 et seq. Also 

Proc. Am. Phil. Soc., December, 1891, p. 139.
M.DRIDGE.] FORMATIONS WASATCH, BRIDGER. 27

west approximately parallel with the Big Horn Rang* 1- at a distance 

from it of 15 to 20 miles. The thickness of the Wasatch beds within 

this area is possibly between 1,500 and 2,000 feet.

On the western side of the Big Horn basin, against the foot of the 

Shoshone Eange, in the vicinity of the Grey Bull and Wood rivers, 

occur several isolated patches of Wasatch, consisting of sandstones, 

conglomerates, and red and gray clays, separated by erosion from the 

main body of the formation in the center of the basin. These remnants 

are probably nowhere over 100 feet in thickness.

In the Wind River valley the Wasatch clays appear to the west of 

the stage road from Embar to Fort Washalde, on both sides of the 

divide between Muddy Creek and Wind River. In the southern bluffs 

of this divide their outcrop passes eastward beneath the Bridger beds 

in the direction of Pavilion Butte. Their area in this valley was not 

determined, but they probably underlie much of the Bridger west of 

the Wind River, with a marked line of unconformity between.

The Bridf/er. T]\\s formation consists of grits and sandstones, of 

which the material is largely quartz, with some feldspathic and other 

debris, derived possibly from an eruptive source, or perhaps from the 

Archean. The cementing substance of the grains is an opaque, white, 

siliceous material, apparently more or less characteristic of the formation as a whole, but less conspicuous in the sandstones than in the 

more gritty beds. The formation easily breaks down, and has been 

converted into a vast sand-desert over much of the area covered by it.

The identification of the beds with the lower portion of the Bridger 

to the south is based upon its fossil mammals, discovered and examined 

by Prof. Osborn and Dr. Wortman in the season of 1891. 1

The extent of the Bridger in the Wind River basin is undetermined. 

A considerable area has been allotted to it on the map, but there have 

possibly been included in it other Tertiary divisions, some of which 

have been distinguished by the members of the early Hayden Survey.2

Volcanic breccias. This great body of rocks is confined to the Shoshone and Absaroka ranges, and lies almost wholly beyond the present 

field. They will not be described in this paper.s

Quaternary. These deposits in the Big Horn and Wind River basins 

and adjoining areas are limited chiefly to stream bottoms, the uplands 

being comparatively devoid of them. They are variable in areal extent, 

and no attempt to map them has been made.

The interrelations of the formations. The Paleozoic measures are 

apparently conformable throughout. The Cambrian and Coal-measures show a marked variation in thickness, but this is probably one 

of ordinary nondeposition, and is not the effect of interformational

1 Op. cit.

"Maps of the U. S. Gool. and Geog. Surv. of the Territories, F. V. Hayden, Geologist in Charge. 

Parts of Central Wyoming, and portions of Wyoming, Idaho, and Utah.

3For details of the composition and occurrence of these beds see Geological History of Yellowstone 

Park, by Arnold Hague. Trans. Inst. Mining Eng., vol, xvi, 1888.
28 . GEOLOGY NORTHWEST WYOMING. [BULL.lid.

i

erosion and unconformity. In the Owl Mountains the formations are 

locally thinner, and towards the west center of the range both Silurian 

and Cambrian are absent, the Carboniferous resting directly on the 

Archean; whether this is due to the presence of an Archean island of 

such height that the Subcarboniferous limestones were the first of 

the series that overlapped its summit, or to a possible fault which 

has brought these two formations into their present relations, was not 

satisfactorily determined.

Succeeding the Paleozoic measures, conformably and without apparent interruption among themselves, are the Mesozoic formations the 

Trias, Jura and Cretaceous to the summit of the Laramie. Subsequent 

to the period of the Laramie, however, there follows a series of unconformities, chiefly by erosion, in which the later formations rest in 

broken succession not only upon one another but upon the several 

members of the Cretaceous as well. At many points evidence exists 

of the great amount of denudation that took place at the close of the 

Laramie the Wasatch, for example, resting at one point on the lowermost strata of the Laramie, at another upon the Montana, and in a 

third locality even upon the Mobrara itself. In the latter instance, 

which happens just south of Sunshine in the high ridge separating 

Wood Eiver from Gooseberry Creek, unconformity both by position 

and erosion exists, the Wasatch lying approximately horizontal across 

a sharp anticlinal fold in the Cretaceous series, the center of which is 

occupied by the Niobrara. With all the instances of unconformity, 

however, accidental conformity is often encountered.

The presence of the Livingston beds within the region explored has 

not been definitely determined, but this formation is strongly developed 

to the northwest, in the valley of the Yellowstone and the mountains to 

the north and south, and it is also reported by Mr. Arnold Hague north 

of the Stinking Water, west of Eattlesnake Eidge, where it rests successively upon all the older formations from Laramie to Carboniferous 

inclusive.

The Wasatch of the present area0 bears a certain lithological resemblance to the upper division of the Livingston as described by Mr. 

Weed,1 which is composed of conglomerates derived from the older 

sedimentaries, and carries also beds of shales in which grays, purples, 

and reds occur. Mr. Weed himself suggests (p. 31) that some evidence 

exists that may prove sufficient cause for the separation of these conglomerates and silts from the Livingston and their recognition as the 

base of the Fort Union (Tertiary) group. It is therefore possible that 

in the absence of definite determination this series of conglomerates in 

the Yellowstone valley and vicinity corresponds with the Wasatch of 

Clarks Fork and the Big Horn and Wind Eiver basins.

The Bridger, so far as observed by the writer, rests upon the Wasatch, 

except along the southern base of theOwl-EattlesnakeEange, where it

1 Op. cit., p. 30.
ELDHIDGE.] STRUCTURE ABSAROKA RANGE. 29

apparently lies directly against the younger Paleozoic formations of 

the mountain, the border of the Cretaceous series being here buried 

beneath its sediments.

Regarding the statement of Dr. Wortman 1 that the " Puerco and 

Laramie do not underlie the Wasatch in the Big Horn basin, but the 

strata rest upon the older sedimentary rocks," it is to be remarked that 

the itinerary of Osborn and Wortman shows a comparatively limited 

area of exploration, rendered necessary by the special object to be 

attained by them. A broader examination would have proved the 

general existence beneath the Wasatch of the Laramie, except in the 

localities cited in the preceding pages of this report. The Puerco is 

absent and the Wasatch does locally rest on older formations than the 

Laramie.

Dr. Wortman 2 also states that the Stinking Water cuts Wasatch 

strata clear to its mouth. Probably from the same cause as the last 

he has been led to overlook the occurrence of the Colorado, Montana 

and Laramie Cretaceous in the valley of this stream over a belt 

extending from the Big Horn River westward beyond the mouth of 

Sage Creek.

STRUCTURE.

The structural features of the region under consideration have been 

developed upon two lines of force, one of the general direction K. 70° 

E. S. 70° W., the other of a K 30° E. S. 30° W. direction. Upon the 

former have originated the Absaroka and Big Horn Ranges; upon the 

latter the Wind River, Shoshone, Owl-Rattlesnake, and Pryor Ranges. 

The influence of the forces thus acting has extended over the entire 

region of exploration, as may be seen by the multitude of subordinate 

flexures, parallel to the larger, which occur far out towards the centers 

of the inclosed basins, and also on the prairies to the east. The action 

of the forces on the two lines was probably synchronous, their interference resulting in the connecting portions between the main uplifts.

The great mountain ranges of northern Wyoming are all primarily 

anticlinal elevations which have subsequently been modified by erosion, 

or, as in portions of the Rocky Mountains proper, by erosion followed 

by local deposition over their summits of an enormous mass of volcanic 

breccias now deeply cut by modern stream courses.

The Absaroka Range. This includes the general mountain mass 

between the Upper Yellowstone River and the prairie to the east, and 

lies for the most part beyond the region of reconnoissance. Its structure is complex, but in general is that of a broad uplift having an 

Archean core fringed along the prairie front with a band of Paleozoic 

and later sedimentary formations. The latter are usually in a highly 

inclined position, dipping east or northeast from 60° to 90°. The harder

1 Op. cit., p. 144. 2 Op. cit., p. 139.
30 GEOLOGY NORTHWEST WYOMING. [BULL-IIS.

(Paleozoic) measures constitute the mountain face, while the softer 

(Triassic, Jurassic, and Cretaceous) beds form a zone of varying width 

along its base. The steep dip of the strata at the edge of the mountains rapidly diminishes beneath the prairie, and usually within 1 or 2 

miles of the base of the range is reduced to between 5° and 15°, the 

curvature generally taking place in the Laramie, but in some localities 

lower down in the Cretaceous series. The trend of the sedirnentaries 

varies between N. 20° W. on the Clarks Fork front to K 60° W. on the 

northern or Yellowstone front. Along the latter front, at the base of 

the range, is a fault by which beds of Laramie age occupying an 

approximately horizontal or slightly undulating position are opposed 

to others of Carboniferous age and highly inclined, the downthrow 

being on the north of the fracture. 1 At the turn in the range the fault 

possibly bends around to the south, but disappears before reaching the 

Montana-Wyoming line. South of Clarks Fork the Paleozoic strata 

extend with easy dip far into the mountains, and, as reported by Mr. 

Hague, form a portion of the south wall of the upper canyon of this 

stream.

Between Pat O'Hara Creek and the Stinking Water two important 

anticlines extend southeastward from the range at angles of abouu 20° 

and 40°, their axes gradually sinking beneath the prairie. The north 

fold lies at the greater angle with the range. On its southwest side 

the Eed Beds and underlying Carboniferous dip 50° to 80° southwest; 

on the northeast a bold escarpment of Paleozoic limestones and quartzites is presented, suggesting a line of fracture along the axis of the 

anticline with the northern half somewhat depressed. The throw 

disappears at the general level of the foothills, which are here somewhat elevated, and the anticline itself- is lost but a short distance 

from the base of the range in the ridge that separates the drainage 

of Pat O'Hara Creek from that of the Cottouwpod, a tributary of the 

Stinking Water. The western end of the fracture was undetermined, 

but it is probably near the origin of the subordinate fold in the range 

proper.

On a direct line with the foregoing anticline, and about 5 miles east of 

the main range, is the isolated peak of Heart Mountain, the structure of 

which was but indefinitely determined. The peak, twinned by denudation, is capped with the quartzites and limestones of the Carboniferous, which dip 10° to 20° northeast and present abrupt cliffs on all 

sides. Along the southern side of the peak, 500 or 600 feet below the 

summit, are shales closely resembling the Jurassic, and which are 

here regarded as such. Their strike and dip are obscure, but they have 

a general appearance of lying horizontal, or slightly inclined from the 

peak, while at one or two points considerable irregularity in their position appears. Farther to the south the Laramie strata appear with

JThis fault was first observed in 1882 by Mr. J. E. Wolff, of tho Northern Transcontinental Survey 

Tenth Census Reports, ¥, S., vol. X, p. 755 and opposite plate.
ELDBIDOE.] STRUCTURE ABSAROKA RANGE. 31

normal strike and dip. To the east and north of the peak the strata of 

the Vermilion Creek or Wasatch formation lie well up on the higher 

slopes, with a possible inner rim of the Jurassic between them and the 

Carboniferous. The Wasatch beds have a gentle dip to the northeast, 

an evidence of movement as late as Tertiary times. West of the peak 

theLaramie series pass uninterruptedly from the valley of Pat O'Hara 

and Skull Creeks to that of the Stinking Water and its tributaries, 

showing but few local irregularities of* either dip or strike, the former 

being generally east-northeast. The relations between the Cretaceous 

and Tertiary formations and those entering into the structure of the 

peak itself are extremely obscure. The most plausible interpretation of 

the regional geology, however, seems to be that of an upward thrust, 

perhaps developed from extreme compression, by which the older beds, 

the Carboniferous and Jurassic, were carried through the surrounding 

formations of younger age, developing as it were between the two 

series of formations a practically circular fault, the strata in the immediate vicinity of which are in considerable confusion.

The southern of the two folds springing from the Absaroka Eange 

forms nil angle of about 20° with the trend of the main mountain mass, 

and is locally known as Eattlesnake Eidge. It is divided from the 

range proper for the greater part of its length by Eattlesnake Creek, 

which enters the Stinking Water just below the confluence of the North 

and South forks. The anticlinal structure is clearly shown in the Paleozoic measures on both sides of the ridge, while the canyon of the 

Stinking Water exposes the arch and the formations involved to the 

Archean. Between the northern anticline and the present, the strata 

form a sharp trough, the axis rapidly rising to the northwest. Both 

these folds spring from the' main range at about the same point, and 

as their distance apart increases, the included, angle shows other and 

subordinate folds, which are nearly parallel with the Eattlesnake Eidge. 

Of these, one of importance lies along the main fork of Cottonwood 

Creek, the present stream channel being a little east of the axis, the 

lowest beds exposed, the base of the Jura. The anticline extends the 

entire length of the creek, although the more pronounced portion, involving the Dakota and underlying formations, constitutes a sharp ridge 5 

to 6 miles in length, considerably north of the Stinking Water.

South of the Stinking Water the Eattlesnake Eidge is continued in 

the knob-like peak of Cedar Mountain, which constitutes the southern 

end of the anticlinal fold in the Paleozoic measures. From this point 

southward the axis of the anticline rapidly sinks, but a crumpled structure is preserved in the Mesozoic formations underlying the prairie for a 

distance of 10 to 15 miles farther, quite to the valley of Grey Bull. The 

most important of these prairie folds commences just east of Cedar 

Mountain in the red sandstones of the Trias, which have not yet 

finally disappeared beneath the surface from the uplift of Eattlesnake 

Eidge5 a short distance southeast the Eed Beds are succeeded by the
32 GEOLOGY NORTHWEST WYOMING. [HULL. 119.

Jura, and this in turn by the Dakota, Beuton, and other Cretaceous 

formations to the summit of the Laramie, the fold showing conspicuously in each. This fold, together with one or two subordinate flexures, 

has an east and west extent of about 10 miles. The prairie thus 

included presents a series of low parallel ridges, inclosed valleys and 

isolated hills, the combined result of folding, erosion and the nature of 

the materials.

The region west of the Rattlesnake Eidge and north of the Stinking 

Water presents a number of crumples within a general synclinal depression, but little of the earlier mountain structure is shown, owing to. 

the presence of the great series of volcanic breccias which lie unconformably across older formations and folds alike.

The Slioshone Range. This embraces the great mass of mountains 

between the Stinking Water and Wind Eiver and is the development 

of three distinct geologic incidents: a post-Cretaceous folding followed 

by a certain amount of erosion 5 deposition upon the area thus prepared 

of a heavy thickness of volcanic breccias and conglomerates which for 

the most part still retain their horizontal position; finally, erosion of 

later times, which has brought about the present configuration of the 

surface. So widespread is the deposit of breccias, however, that the 

earlier structural history is suggested only by the folds along the base 

of the range. These preserve a general trend of N". 30° to 60° W., S. 

30° to 60° E., but local departures from this direction appear, however, 

as in the approximately east and west fold in the Stinking Water valley, and the north and south fold between Wood Elver and Grey Bull.

Commencing at the north, two anticlines occupy the northeastern 

slope of Meeteetse Mountain, crossing the heads of Sage, Carter, and 

Belkriap creeks. One of these, the southwestern, has a N. 60° W. 

trend, with a lineal extent of 10 to 12 miles; the other, or northeastern, 

has a course & little nearer east and west and is somewhat shorter.

The crest of the former fold is exposed in strata of probable Laramie 

age at an altitude of 1,000 to 1,200 feet above the valley of the Stinking 

Water. The southwestern half of the fold, a short distance from the 

axis, becomes more or less obscured by d6bris from the mountain slopes 

above or passes into an area of broken and confused strata; at the few 

points, however, where clear observations are attainable, the dip of the 

beds along this side of the flexure varies from 20° to 80°. The northeastern half of the anticline is more regular, and the strata have a 

general dip of 25° to 30°, with a few, local, minor flexures. The anticline appears almost wholly in Laramie strata, but between the heads 

of Carter and Sage Creeks is a series of red, white and gray clays and 

yellow sandstones and conglomerates which closely resemble certain 

phases of the Wasatch. The stratigraphic relations of the two series 

of beds are, however, indefinite. This anticline disappears to the 

west in the valley of the Stinking Water; to the east in the slopes 

of Meeteetse Mountain at the head of Sage Creek,
KLUDGE.] STRUCTURE SHOSHONE RANGE. 33

The second anticline, northeast of that just described, lies along the 

base of the Meeteetse Range in the valley of the Stinking Water. It 

extends west nearly to Belkuap Creek. To the east it enters the bluff 

of Carter Creek and is lost in the broad flat between this and Sage 

Creek. Transversely the fold is asymmetric, the strata on the southwest side having the steeper dip, 40° to 60°. North of the axial line 

the strata dip but 15° to 20°, and pass beneath the broad valley of the 

Stinking Water, to remain buried beneath the breccias of the Absarokas, or to reappear in the river bluffs or about the base of the Cedar 

Mountain and Rattlesnake Ridge. This profile of the fold therefore 

resembles that of the large anticline to the southwest. The crest of 

the smaller anticline is .eroded to the Jurassic, while the highest beds 

on either side are now those of Mobrara age.

Between this anticline and that to the southwest there is a sharp 

syncline, so sharp, in fact, that it suggests the presence of a fault along 

a considerable portion of its length.

The structure beneath the valley of the Stinking Water, in the broad, 

triangular flat above Cedar Mountain, is doubtless that of a syncliue 

modified by slight minor flexures, some of which appear in the bluffs 

on the north side of the river.

In the valley of Upper Sage Creek, between Meeteetse Mountain and 

the southern prolongation of the Rattlesnake fold, is a small anticline 

parallel with the Rattlesnake flexure, the northern end of which is 

within 5 or 6 miles of the Stinking Water, the southern in the high 

mesa separating Sage and Meeteetse creeks, the breadth of the fold 

being 3 or 4 miles. The fold shows a median ridge of Mobrara flanked 

on the east, across a valley of Montana shales, by a second ridge, of 

Laramie sandstones. West of the Mobrara ridge the area of the Montana is very broad, but the line between this formation and the Laramie 

is obscured by the structure about the immediate base of Meeteetse 

Mountain.

Between the anticline just described and that next east is a narrow 

synclinal valley, 1 to 2 miles wide, lying wholly in the Laramie shales 

and bounded east and west by the underlying sandstones of the same 

formation. The axis of the trough tilts up to the north of Sage Creek, 

and this end of the valley is also closed by a rim of the sandstones at 

the base of the Laramie. The southern end of the valley is closed by 

the Meeteetse mesa, in the sharp and eroded face of which the general 

structure of the trough is well exposed. The syncline is sharp, the 

sandstones on either side varying in dip from 45° to 70° or 80°. The 

details of the structure of the mesa between Sage and Meeteetse Creeks 

are obscured beneath wash and soil.

The Sunshine district. In the southern face of the Meeteetse mesa,

from a little above Arland Post-office to the mouth of Meeteetse Creek,

strata of the lower Laramie are again exposed and show one or two

broad, gentle anticlines, with a general trend of N. 40° to 50° W. and

Bull. 119 3
34 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

extending southeast beyond the valley of the Grey Bull. Additional 

folds also appear in the bluffs of the latter stream, a series of anticlines 

with the intervening synclinal troughs extending from the edge of the 

Wasateh below Meeteetse Creek to the base of the Shoshone Range, 

greatly increasing by repetition the surface area of the Laramie, Montana, and Colorado beds. These flexures are, again, connected with 

others south of the Grey Bull, extending to the vicinity of Gooseberry 

and Grass creeks. The region thus indicated is so united in its geologic development that it may be regarded as a district in itself and 

designated, " Sunshine," from its central post-office and settlement on 

Wood River. The area of the district is approximately 25 miles 

squaTe. The flexures which it embraces have a general trend of K. 30° 

to 50° W., varying locally N. to 3sT. 80° W., but their distribution is 

more or less irregular, the result of general crumpling.

The front of the Shoshone Range bordering this district is a bold 

escarpment of volcanic breccias and interstratified lava flows, from 

beneath which at the prairie level pass the great series of Cretaceous 

clays and, perhaps, other beds a little above or below. The Montana 

and Colorado groups constitute a broad zone, 5 to 10 miles wide, at 

the base of the range. Locally these are overlain by patches of 

Wasatch which have been separated from the main deposit in the center of the basin. Areas of this Tertiary formation occur north of the 

Grey Bull, between this stream and Wood River, and capping the high 

lands to the south of the latter valley. These beds show comparatively little flexing, the great series of folds in the district being confined to the Cretaceous, upon which the Wasatch rests unconformably.

Two or three miles below the debouchment of the Grey Bull from 

the Shoshone Range a prominent anticlinal ridge appears in Mobrara 

beds, extending from a mile or two north of the river to five or six 

south, the trend being northwest. West of the ridge the Montana 

underlies the surface nearly to the mountain, local outcrops of Laramie 

being reported immediately beneath the eruptive series. These were 

not observed by the writer, but it is quite possible that they exist.

Passing eastward along the Grey Bull from this anticline, a broad 

stretch of several miles is crossed, underlain by the Montana. The Laramie first appears below Pranks Ranch, 6 or 7 miles above the mouth of 

Wood River, where it caps a line of bluffs presenting a sharp face to 

the west. From this line, which is approximately north and south, the . Laramie extends eastward in a synclinal trough, followed still further 

to the east by an anticline which occupies the residue of the region to 

Wood River. The northward extent of these flexures beyond Grey 

Bull is 5 to 6 miles. Southward they are continued to Gooseberry 

Creek, crossing the Wood River valley in the vicinity of Sunshine.

The syncline is marked by a broad topographic depression, with the 

rim raised considerably above the surrounding prairie. The center is
ELDBIDOE.] STRUCTURE SUNSHINE DISTRICT. 35

occupied by the sandstones of the lower Laramie, which are chiefly 

confined to the region south of Grey Bull. The strata dip to the interior 

from 20° to 45° or 50°, those on the east and south having the steeper 

inclination; along the western rim the beds flatten considerably, forming a lip to this edge of the basin. In addition to the Grey Bull, the 

syncline is also cut about midway its length by a stream heading 

against the Shoshone Range. At the southwest corner of the area the 

Laramie measures are unconformably capped by the conglomerates 

and red clays of the Wasatch. The syncline derives special importance 

from the presence of coal seams of workable thickness and quality.

The anticline east of the syncliue is chiefly exposed in the Montana, 

but the Mobrara outcrops for a few miles along the central portion of 

its axis. The fold appears in section in a hill a half mile north of Grey 

Bull, and again in the bluffs of Wood River near Sunshine. South of 

Sunshine it passes into the ridge between Wood River and Gooseberry 

Creek, where it is partially overlain by the conglomerates of the 

Wasatch. From this point it crosses Gooseberry Creek, a sharp flexure, 

and a little beyond becomes complicated by the presence of other 

folds, which extend into the higher foothills of the region further 

south, and probably eventually pass beneath the breccias of the Sho. 

shone Eange. Along the northern half of the fold Wood Eiver occupies 

the broad belt of Montana shales east of the axis, while the Laramie 

appears in the high ridges east of this stream, crossing, however, to the 

west side a little above its mouth, and Grey Bull a little beyond. This 

outcrop of the Laramie is the western edge of the main body of the 

formation which now extends with a feAv local interruptions beneath the 

center of the Big Horn basin.

On Grey Bull, at the mouth of Rawhide Creek, another gentle asymmetric anticline may be seen in the basal sandstones of the Laramie. 

It extends north 4 or 5 miles, and south into the region between Wood 

River and Iron Spring Creek. East of this for several miles the bluffs 

of Grey Bull are occupied by the lower measures of the Laramie, the 

upper division of the formation the lignitic clays appearing just west 

of Meeteetse Post-office, Avhile the lower beds of the Wasatch form the 

crest of the bluffs just below the mouth of Meeteetse Creek. The strata 

here dip gently east-northeast or northeast and gradually pass beneath 

the center of the basin. The rim of the Wasatch passes from the bluffs 

of Grey Bull with regular trend S. 30° E., a distance of nearly 20 miles 

to Gooseberry Creek, forming for most of the way a high prominent 

ridge with cliffs looking to the west.

In the hills south of the Meeteetse Post-office is one of the most prominent anticlines of the district. Its longitudinal axis, which has a general trend of N. 50° W., is from 15 to 20 miles long, its transverse, from 

8 to 10 miles. The southern extremity is on Gooseberry Creek, at the 

mouth of Enos, where the axis has a local trend of JST. 70° W. to conform 

with other folds of this vicinity. For 5 to 7 miles along the middle por-
36 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

tion of its axis the anticline presents a deep topographic depression 

locally known as the Upper Buffalo basin. The basin is occupied by 

the Montana shales and is surrounded by a high and almost impassable 

wall of Laramie sandstones dipping outward at angles from 20° to 45°, 

the drainage being by a single sharp cut on the eastern side. About 

the sandstone rim, on the exterior, is the upper, or shaly, division of 

the Laramie. The hills at the southern end of the basin, just north of 

Gooseberry Creek, are exceptionally high, the basal sandstones of the 

Laramie outcropping in bold spires and rugged ridges.

East of the Upper Buffalo basin, and forming a portion of the general prairie region, is the extensive Lower Buffalo basin. This is not, 

ho>vever, a structural basin, but, rather, one of accidental erosion, common in regions where variation in "the component materials of the beds 

is marked.

Six or seven miles southwest of the Upper Buffalo basin and 2 or 3 

above the confluence of Iron Spring and Gooseberry Creeks is another 

anticline, of similar structure and topography. This is cut transversely 

by the valley of Gooseberry Creek, and shows a central body of Montana shales inclosed by a rim of Laramie sandstones dipping outward 

from 10° to 20°. The longitudinal axis of the fold has a north-northwest trend, and is, perhaps, 5 or 6 miles long; the transverse axis, 

somewhat shorter. This anticline is the first below the western rim of 

the Laramie, which crosses the stream valley several miles farther up, 

south-southeast from Sunshine Post-office. Still another anticline, smaller than the foregoing, crosses Gooseberry Creek at the mouth of Iron 

Spring, being well shown in the heavy sandstone walls of both stream 

valleys.

Within the area between Gooseberry and the Grey Bull, in the confusion of hills and valleys that there exists, several other folds in the 

Laramie were observed, all of greater or less importance, but detailed 

examination was not undertaken.

In the lower portion of the canyon of Gooseberry Creek, from the 

mouth of Iron Spring to 5 or 6 miles below Enos, and in the region to 

the south, the folding is of considerable complexity. Eor 3 or 4 miles 

below Iron Spring Creek the valley of Gooseberry is cut in the trough 

of a syncline. A little lower down the strata bend from the syncline 

to an anticline, and a mile below this, in the sharp point of land 

between the middle and east forks, another syncline follows, showing 

in a patch-of Wasatch sandstones overlying the Laramie shales. On a 

small tributary of Gooseberry from the south, 2 or 3 miles east of Enos 

Creek, an important anticline, 4 or 5 miles in longitudinal extent and 

having a trend of N. 50° W., exposes at the center a small area of 

Montana, within a rim of Laramie sandstones carrying workable coal 

seams. Separating this from the southern end of the fold of the Upper 

Buffalo basin is a slight syncline, and on Enos Creek, halfway between 

the mouth and head, is a broader trough, in' higher Laramie strata.
ELDRIDOE.] STRUCTURE OWL-RATTLESNAKE RANGE. 37

The entire region between Gooseberry and Grass Creeks is an area of 

many folds, some in continuation of those already described, others 

orginating within the hills themselves. East of this region the high 

foothills give way to the gentler and more regular ridges of the prairies, 

and the formations appear in succession from periphery to center of 

basin.

Grass Creek displays in its walls three or four more or less important 

flexures in the lower Laramie series, both above and below the point 

at which the stage road enters it from the north. Near the head of the 

valley the Wasatch appears, and on the divide between this and 

Twenty-one Creek, a tributary of the Cottonwood, the breccias and 

conglomerates of the Shoshone Range, in an eastward extension. The 

latter formation indeed covers a considerable area between this and 

North Owl Creek, capping the greater portion of the higher foothills 

which lie between these streams. -

The Owl-Rattlesnaice Range. The system of folds to which this range 

belongs extends from out the Shoshone Mountains and connects them 

structurally as well as topographically with the Big Horn Range 80 or 

90 miles east. The system includes the folds which constitute the 

mountain mass proper and numerous others parallel with these and 

occupying a broad belt of prairie on either side of the base of the range. 

The total width of territory thus embraced is not less than 25 or 30 

miles.

The Owl Mountains topographically trend N. 70° W. Structurally, 

however, the range consists of a series of folds and, possibly, faults, 

which trend N. 50° to 60° W. or somewhat diagonal with the topographic trend, and this direction, N. 50° or CO0 W., is that on which 

the geologic features of the entire region are developed. Four folds, or 

the faults into which they are possibly developed along a portion of 

their length, occupy the summit of the range, their axes being intersected about midway by the crest-line. Erosion along the axes has left 

in the intervals large blocks of Carboniferous limestones and quartzites, which cap the higher portions of the range.

Both sides of the Owl Mountains send out subordinate folds, in one 

or two instances but slightly less important than the main flexures. On 

the north side of the range, just east of the point where the stage 

road begins the ascent of the mountain, a sharp anticline is cut by 

the South Fork of Owl Creek, the general trend of its axis being 1ST. 

50° W. The lowest beds exposed are the Carboniferous qnartzites. 

The fold extends but a short distance beyond the North Fork. Eastward along the range are several folds showing the Eed Beds and 

underlying qnartzites and conglomerates of the Carboniferous sharply 

cut by the stream courses to depths between 200 and 400 feet. Of 

these folds some end at the base of the mountain slope, others reach 

far into the basin. In the vicinity of the Wind River canyon other 

folds occur, with occasional small displacements along short fault
38 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

lines. Through one of these flexures has been eroded, deep into the 

mountain, the gorge known as "Red Canyon," of which the walls are 

composed almost wholly of Triassic sandstones. The range itself, in 

the vicinity of the Wind River Canyon, is a simple anticlinal fold, 

of which the northern slope is very gentle, the southern, precipitous. 

The entire southern face of the Owl Mountains, however is steep, 

the strata on this side dipping from 60° to 90°.

South of the range several pronounced anticlines spring from the 

western third. Here three or four sharp flexures originating at the summit of the mountain rapidly succeed each other, corresponding synclines 

intervening. Their axes make an angle of about 20° with the trend of the 

main range, and .sink more or less fapidly to the southeast, beneath the 

general valley of Wind Eiver. The height of the ridges sharply decreases 

beyond the outcrop of Carboniferous quartzites, but the folds continue 

pronounced in the Jurassic and Cretaceous strata, far out from the base 

of the range. In the Niobrara the flexures show particularly well, the 

sandstones and harder shales of this formation constituting a sharp 

ridge between Benton and Montana shales, the latter underlying the 

broad valley of the Mud,dy and its tributary coul6es. The region embracing the foregoing anticlines extends from a point in the range near 

the Embar and Fort Washakie stage road westward beyond the borders 

of the Shoshone Indian Eeservation, and it is reported that flexures 

more or less similar occur nearly to the head of the Wind Eiver valley.

Along the northern base of the Owl Mountains, within a belt of 10 

miles, are many folds, all having an approximately K. 60° W. trend, 

some being confined wholly to the prairie, others extending a short distance into the range. From a high point opposite the confluence of 

the North and South Forks of Owl Creek, six anticlines are in view. 

Of these the most important extends across both Cottonwood and 

Owl Creeks, its axis intercepting the latter stream 10 or 12 miles below 

Embar. The linear extent of this anticline can not be less than 20 

miles, passing to the northeast into the great body of Laramie strata 

between Cottonwood and Grass Creeks, and to the southeast into the 

lower Cretaceous and Jurassic beds of the lower slopes of the Owl Mountains. On the axis two low ridges of Mobrara are developed, one cut 

by Cottonwood, the other a little north of Owl Creek. The Niobrara 

ridges are surrounded by a broad expanse of Montana, and this in turn 

is inclosed on the north by a bluff of Laramie sandstones from 100 to 

400 feet high. A smaller outlier of Laramie also caps a knoll a little 

southwest of the southern of the two Mobrara ridges, the strata forming a shallow syncline.

Northeast of the foregoing anticline is a second, a shallow syncline, 

5 or 6 miles broad, intervening. The flexures show particularly well 

in the edge of the Laramie, which for several miles forms a wavy 

line in and out about the northern portions of the folds. A general 

easterly trend is, however, preserved for this edge of the formation,
STRUCTURE OWL-RATTLESNAKE RANGE. 39

which, after one or two additional flexures just west of the Big Horn 

River, crosses this stream and pursues its course 15 or 20 miles further 

east.

Opposite the confluence of North and South Owl Creeks, about midway between the large anticline first described and Embar Postoffice*, is another sharp anticlinal fold, also showing a low ridge of 

Mobrara for some distance along its axis. This anticline disappears 

a mile or two north of the stream, but. to the south passes into the 

lower slopes of the range a distance of 5 or 6 miles. Southwest of this 

is still another small anticline, again with a small Niobrara exposure 

at its center.

In the region of the Ked Canyon, and extending along the lower 

slopes and foothills of the range for several miles in either direction, is 

a broad, N. 70° W. fold, with nearly the whole series of Triassic Bed 

Beds exposed at the center, in the canyon walls. On the outer or 

northern slope of the fold the canyon creek has also cut a broad expanse 

of Jurassic sediments, affording an exposure visible for many miles.

Owing to these folds, the strata along the base and on the lower 

slopes of Owl Mountain display considerable irregularity of outcrop. 

In general, however, the Eed Beds extend for a distance upon the 

slopes of the range. The Jurassic measures lie at the immediate base 

or, by a fold, extend a short distance prairieward. The Dakota and 

Benton often form a line of low knolls or ridges just without, while the 

Niobrara occurs both along the front of the range and, by folding, in 

numerous ridges-out in the basin; the Montana follows, and beyond 

this are the long bluffs of the Laramie and Wasatch sandstones.

South of the Owl Mountains and east of the Embar and Fort 

Washakie stage road and the region of anticlinal spurs given off from 

the western end of the range, are several flexures, extending along the 

front of the range a distance of 15 to 20 miles and embracing the formations from Trias to Laramie.

The first anticline encountered extends east from the Mail Camp for 

several miles, at a distance from the range of one-half to three-fourths 

of a mile, its axis being coincident with the center of a prominent Niobrara ridge. Between this and the mountain is a sharp syncline, 

while without, another separates it from a second and parallel anticline, 3£ to 4 miles south.

The second anticline appears in the Montana and Laramie formations. Its length is probably between 10 and 15 miles, the strata 

forming a low ridge most of the distance. The western end of the 

ridge is indented by erosion of the beds along the axis of the fold to a 

horizon low down in the Montana. North and south of this indentation are conspicuous promontories, formed of the portion of the 

Laramie still preserved, the strata showing slight synclinal flexures. 

The area north and south of the promontories is occupied by Montana 

shales. The heavy Laramie sandstones in the southern promontory
40 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

are continued eastward for 10 or 12 miles in a prominent bluff, 200 to 

300 feet high, overlooking a broad, shallow depression in Montana, 

to the south. Around the eastern end of this depression the sandstones bend with one or two changes in dip, the most important showing 

the end of a gentle syncline which has a general east to west trend and 

a length of 10 to 15 miles, the axis being crossed by the stage road 

between Embar and Fort Washakie about 12 miles from the base of 

Owl Mountains.

South of this syncline is the final anticline observed in connection 

with the Owl Mountain system. It occupies the ridge dividing the 

drainage of Muddy Creek from that of Wind River, and has for its 

central formation the Mobrara shales and sandstones. It is a sharp 

crumple, the length of which is about 15-miles. At the western end it 

merges with the folds which spring from the western end of the Owl 

Mountains. The folding of this region has apparently extended to the 

Wasatch strata, a slight local dip to the southwest occurring in them 

at one or two points.

The Rattlesnake Range is the structural continuation of the Owl 

Mountains. It is in general a broad anticlinal uplift, with steep southern and gentle northern slope. It unites with the Big Horn Range, 

apparently by gradual change in axial trend, but the region of their 

union was not visited.

On the south side of the general fold, for some distance east of the 

Wind River Canyon, the Paleozoic measures, dip from 60° to 90° south. 

Along portions of this front of both the Owl and.Rattlesnake mountains erosion has removed the Carboniferous and underlying formations nearly to the prairie level, while the Mesozoic beds, which further 

west occupy a broad superficial area at the base of the range are, in the 

vicinity of Wind River, concealed beneath deposits of Tertiary age. 

Several miles east of the Wind River Canyon the Carboniferous and 

older strata entirely span the range, while even the Cretaceous beds 

locally reach well towards the summit.

The north side of the Rattlesnake Range presents an even, gentle 

slope, with a minimum amount of subordinate folding; but in a belt 

about 10 miles wide along the base of the range, especially in the valley 

of the Big Horn River and its tributary, Kirby Creek, several important flexures were observed together with an occasional fault.

Passing down the Big Horn River from the base of the range, the 

strata dip gently northward for a distance of 2 or 3 miles, the formations 

succeeding each other to a horizon a little above the base of the Montana, the Red Beds forming a prominent ridge next the foot of the 

mountain. Within a mile or two of the Hot Springs, the dip changes 

to the south and at the springs the axis of an anticline is encountered, 

the trend of which is approximately N. 75° W. The fold forms a prominent ridge for 10 to 15 miles along the front of the Owl-Rattlesnake 

Range, the Big Horn River cutting it about one-third the distance from
ELDBIDQB.] STRUCTURE BIG HORN RANGE. 41

the western end. The center of the anticline is occupied both east and 

west of the river by the red Triassic sandstones. The flexure in these 

is very sharp and the rocks are extensively cracked, the copious waters 

of the present hot springs finding their way through some of the still 

open fissures. The largest of these springs is fully 25 feet in diameter, 

with an unmeasured and possibly unmeasurable depth. The Jura, 

Dakota, Benton and Niborara succeed one another in regular order 

no the flanks of this anticline, and at the ends close around and over 

the formations lying within.

Between the Hot Springs nticliue and Kirby Creek, 6 or 7 miles 

north, several other east and west flexures of greater or less importance 

occur in middle Cretaceous clays, but the details of their structure and 

their interrelations were i\ot examined.

North of Kirby Creek the Laramie sandstones form a line of bluffs 

extending east from the Big Horn. River for 15 miles. Ten miles out the 

bluffs are doubled by a strike fault, which is 4 or 5 miles long and ends 

to the east with the bluff line. The displacement along the fault is 

about 300 feet, the strata to the south being downthrown. East of the 

line of bluffs a gentle anticline appears, involving both upper and lower 

divisions of the Laramie and the Montana. The area embraced by the 

fold is very extensive, and is one of the most broken, topographically, 

in the entire Big Horn basin. The Laramie sandstones and shales, 

with their slight dips, have been, eroded into innumerable and labyrinthine gulches, utterly devoid of water except in the winter or in a cloudburst in the summer. The whole region about, from the Big Horn to 

No Wood Creek, is intensely barren and parched, and is considered 

almost impassable.

Down the Big Horn the formations preserve considerable regularity 

of dip, but about 8 miles above the mouth of No Water Creek, in the 

bluffs east of the river-, the axis of a broad syncline is passed. North 

of it is a low anticlinal arch, this in turn being succeeded by another 

syncline. The trend of these folds is more to the northwest than those 

nearer the base of the Rattlesnake Eange, holding a position intermediate between the Owl-Rattlesnake and Big Horn systems of flexures. 

The Big Horn Range. This is structurally a broad anticlinal fold, the 

general trend of which is, for the southern half, north to south, to the 

north of this veering round to N. 20° W., and finally, as the Montana 

line is approached, to N. 40° W. In the Pryor Range the structural 

continuation of the Big Horn the trend is N. 60° W. A cross section 

of the Big Horn fold shows it to be asymmetric, but the steeper inclination of the strata is now on one side of the range, now on the other. 

In a profile west from Sheridan the gentler slope is to the east, the 

strata dipping but 35° or 40°. On the west the dip passes sharply 

from 25° or 30° on the higher slopes of the range to vertical on the 

lower with, possibly, even local faulting. Toward the Montana line 

the dip on both sides the range shallows considerably, on the west
42 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

diminishing to but little over 20° and, locally, even below this. From 

the region of Shell Creek south the dip on this side the range again 

decreases to between 20° and 30°, and this, so far as observed, holds to 

the southern end of the fold. On the opposite or eastern side of the 

range, for a long distance south of Fort McKinney, the strata are nearly 

vertical. Thus the force which brought the range into existence, or the 

resistance opposed to it, seems to have been unequally distributed along 

the length of the fold, the effect, being greatest now on. one side, now 

on the other. The Big Horn anticline is a comparatively flat-topped 

flexure, the distance from base to base of the present range as limited 

by the harder (Paleozoic) formations being about 50 miles, and the general elevation above the prairie approximately but 5,000 to 6,000 feet. 

This, with 2,000 to 3,000 feet added for erosion of the Paleozoic strata 

from the summit, would increase the original height to between 7,000 

and 9,000 feet, or considerably below the ratio of 2 to 50. But the topographic range of to-day is of considerably less area than that of the 

original fold. From the Carboniferous quartzites at the present base 

of the range outward, on both sides, the fold is continued in the Mesozoic measures, with diminishing dip, in some localities a distance of 10 

to 15 miles.

In the development of the general fold of the Big Horn Mountains 

a considerable number of subordinate flexures came into existence both 

in that portion which constitutes the present topographic range and 

in the region along its base. In the range itself several flexures are 

shown in transverse section in the Paleozoic beds upon the slopes and 

crest, particularly east of the median line, in the canyon walls of the 

present stream courses. Folding of this nature has taken place over 

the entire length of the range, but the linear extent of the individual 

flexures is rarely greater than 5 or 10 miles. Conspicuous among the 

observed flexures on the eastern face and crest of the range are: one 

4 to 5 miles long cut by the canyon of Wolf Creek, showing particularly well in its northern wall and occupying the slope of the range; a 

second in the canyon of Little Tongue Elver; a third, several miles in 

extent, on the summit of the range west of Dayton, the axis of which 

lies in a longitudinal valley just within the outer or easternmost line 

of crests, and which is crossed by the Bald Mountain trail a mile or 

two after reaching the summit; a fourth, southeast of the latter, of 

still greater extent, also just within the outer line of crests; a fifth on 

a branch of Pass Creek, which now flows along its axis. On the 

western side of the range, in the vicinity of the Bald Mountain trail, 

only a few minor and very gentle flexures exist, confined to the more 

horizontal portion of the strata on the higher slopes. On the Canyon 

Creek trail, several miles south o'f Cloud Peak, and along the range to 

the south of this, both east and west of the median crest line, are 

several slight undulations, hardly sufficient, however, to give local 

character to the crest.
ELDBIDQE.] STRUCTURE BTG HORN RANGE. 43

In addition to the folds, strike faults, usually of comparatively slight 

throw between 200 and 500 feet are quite numerous, especially on 

the summit of the range within the first or outer rim. Not only have 

these caused a reduplication of the strata and the area occupied by 

them, but to the fracture lines and the folds are often due the long 

north and south courses within the range peculiar to so many of the 

streams. Just north of Canyon Creek, on the west side of the range, 

a prominent east to west fault crosses the Carboniferous quartzites 

and limestones, by which a sharp bluff of several hundred feet is 

created by the elevation of the beds north of the fracture. This bluff 

overlooks the range to the south and constitutes from this direction a 

most noticeable landmark.

The Big Horn Mountains present a massive granitic core, which is 

exposed at the summit of the range over a maximum width of between 

20 and 30 miles. Eemnauts of the Paleozoic shales, limestones and 

quartzites are left here and there upon the Archean, forming buttes 

from 300 to 500 feet high, the strata showing but moderate dips in any 

direction. Toward the periphery of the crest the area of the early sedimentaries rapidly increases, and at the rim all are complete. In the 

central or Archean area large bodies of eruptive rock and also dikes of 

the same material were observed, the former constituting many of the 

prominent peaks; whether all, however, are of eruptive material, was 

not determined by the writer, their mapping as such being based upon 

reports of members of the topographic corps of the Geological Survey. 

Flanking the range at either base are the Triassic Bed Beds (here and 

there constituting a low ridge), the Jura, the Dakota (occurring locally 

in sharp, comb-like exposures), the Benton, Niobrara, Montana, and 

Laramie. The Niobrara also locally forms a slight ridge separating the 

two Cretaceous formations of shale, while the Laramie often outcrops in 

low bluffs capping slopes of Montana shales.

The anticlines of the Big Horn basin that belong to the present system of folds are: two in the northeast portion, at a distance of 10 to 12 

miles from the base of the range; and a complex to the south, along 

the valley of No Wood Creek, from 3 to 5 miles from the base. The 

latter is parallel with the range, but the axes of the others lie a little 

more to the northwest than the axis of the range. These folds constitute the Five Spring Ridge, Sheep Mountain, and the Bonanza 

Ridges, the first being the northernmost. Ihe Five Spring Ridge and 

Sheep Mountain have a position en Echelon with each other, while the 

Bonanza complex is nearly in line with Sheep Mountain, with a possible slight offset to the west. Together these folds extend nearly the 

entire length of the Big Horn Range.

The Five Spring Ridge extends from the Stinking Water valley 

south to the vicinity of Salt Creek. The exposed core of the anticline 

is of Triassic Red Beds, which outcrop for 8 or 10 miles of its length 

and near the southern end are cut transversely by the Big Horn River.
44 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

The section at this point shows an asymmetric fold, the westerly dip 

being 15° to 20°, the easterly 45° to 60°, the present elevation above 

the surrounding prairie 300 to 400 feet. On the east the Jurassic, and 

Cretaceous formations to the Montana succeed in turn the Eed Beds, 

the Montana entering into the fold but slightly. West of the ridge, for 

some distance along the middle portion of its length, the younger 

measures have been eroded, leaving only the gently dipping Eed Beds, 

which, after occupying a slight depression between this and the Sheep 

Mountain fold, pass directly into the latter, with, possibly, a small 

intervening fault. To the north and south the younger formations close 

around those lying within, the axis dips in both directions beneath the 

prairie, and the fold gradually disappears.

The Sheep Mountain anticline has a like trend with the Five Spring 

and overlaps it on the west for several miles. The distance between 

the two axes is about 4 miles. The Sheep Mountain fold extends 

from near the Stinking Water valley to a little beyond Shell Creek, 

although the elevated ridge which marks its median line is somewhat shorter than the extreme length. The flexure is sharp and for 

much of its length asymmetric, the easterly dip being between 60° 

and 80°, the westerly somewhat less. The ridge formed by the anticline has a maximum height of 500 or 600 feet; this in the vicinity of 

the Big Horn Eiver, which cuts it transversely about midway. The 

cut exposes in its walls a central body of Carboniferous limestones and 

quartzites, that also extend along the crest, and slopes of the ridge 

5 to 10 miles north and south of the stream. Beyond this the topographic ridge consists of the softer Triassic and overlying beds, and 

has been eroded to a height usually less than 300 feet. The fold finally 

disappears in tbe Pierre shales.

The effect of the Five Spring and Sheep Mountain anticlines has been 

to greatly enlarge the areas of exposure of the formations involved, particularly those of Mesozoic age; to increase their line of outcrop to more 

than twice that under ordinary conditions; and, in the case of the 

Laramie, to throw the main line of its coal-measures far to the west in 

some localities 10 to 25 miles from the base of the Big Horn Eange. 

Both the Five Spring and Sheep Mountain folds are clearly visible from 

the western edge of the Big Horn basin, 60 to 70 miles distant.

The Bonanza complex of anticlines extends from a few miles north of 

No Wood Creek nearly t8 the head of this stream, a distance of 50 miles. 

The general system, of folds is parallel with the Big Horn Eange and 

occupies a belt from 5 to 10 miles wide along its base. Some of the folds 

appear in the Colorado and Montana, while others, nearer the range, 

occur in the Dakota, Jurassic and Triassic formations. The anticlinal 

axes vary in length from 10 to 30 miles, and the east and west slopes 

of the folds are usually between 20° and 40°.

Passing up No Wood Greek, the first important flexure is crossed 4 

or 5 miles above the mouth of the stream, the axis having a N. 25° W. 

trend, the fold being in Middle Cretaceous shales.
ELDBIDOB.] STRUCTURE PRYOR MOUNTAINS. 45

East of this 2 or 3 miles, and separated from it by a narrow syncline, 

is a second anticline in Mobrara and Benton shales. This also trends 

N. 25° W., and extends from a point several miles north of No Wood to 

one 7 or 8 miles south -of Bonanza, where it merges into other folds. 

The axis of the anticline passes east of Bonanza, the strata being 

thrown into a prominent ridge 200 to 300 feet high, which is more or 

less eroded on the west

One mile west of Bonanza is the axis of a third parallel anticline. 

This appears several miles below Bonanza, and extends beyond it, to the 

south, between 15 and 20 miles. The axis of the anticline is occupied 

along its middle portion by the Niobrara, in the shales of which opposite Bonanza a petroleum spring occurs.

Twelve miles south of Bonanza a fourth and very large anticline occurs, 

the strata exposed along the axis being the Bed Beds. - Other folds of 

considerable prominence were observed still farther south. The folds 

of this entire complex are all more or less intimately related, the synclinal troughs usually being narrow, the anticlines sooner or later 

merging into one another. The entire area of this complex is, indeed, 

one of much crumpling.

The anticlines between the foregoing and the Big HornEange occur 

in the lower Mesozoic formations, but were not examined in detail by 

the writer.

The Pryor Mountains. These are structurally the northwestern continuation of the Big Horn Bange, extending from the Big Horn River, 

south of the Montana-Wyoming line, some 30 or 40 miles west-northwest, into the State of Montana. The range belongs to the ET. 60° W. 

series of flexures, or to the same system as the Owl Creek Mountains 

and the Wind Eiver Range.

Though excellent exposures occur in the Big Horn Canyon and on 

the slopes of the mountain above, a transverse section of the range 

was observed only at a distance, from points to the southeast and 

southwest on the general route of reconnoissance. The range is an 

anticline, but has a double crest, induced by a longitudinal fault along 

the western slope of the fold. The fault passes along the valley 

between the two crests, the strata on both sides the fracture dipping 

southwest about 30°, those on the east being downthrown. Southeast 

the fault probably does not extend beyond the Big Horn Canyon; northwest it disappears at the head of Sage Creek, beyond which the range 

is single, a continuation of the eastern of the two ridges.

The formations which constitute the Pryor Mountains are of Paleozoic and Archean age, the latter exposed in the canyon of the Big 

Horn River. The Mesozoic formations the red sandstones of the 

Trias and overlying series have been eroded to the base of the range 

both on the north and south, and from between the crests they have 

disappeared except a few scattered outcrops. The backs of both 

ridges consist of the Carboniferous quartzites, which in the western
46 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

ridge particularly, have been deeply channeled with sharp canyons 

that diagonally cross dip and coincident topographic slope. The 

extent of the Pryor fold is considerably greater than the area of the 

range itself. The Trias, Jura, Dakota and Ben ton, outcrop along the 

base of the mountain, continuous with the outcrops farther to the 

south. Their dip in the Big Horn basin is usually below 15°, shallowing still further as distance from the range is gained. The formations appear, therefore, in wide terranes, the Laramie lying well out 

in the valley of Sage Creek. Moreover, the area of Laramie has been 

further diminished by a gentle rise of the strata along a portion of 

Sage Creek and their removal from the arch by erosion.

The Pryor Eange disappears to the northwest by a gradual sinking 

of its axis. The region about, however, for a long distance is maintained at a considerable elevation and shows numerous minor folds, 

spurs of the main flexure or crumples of a secondary character but of 

synchronous development.

The divide between the Big Horn basin and the Yellowstone. One of 

the minor folds given off from the western end of the Pryor Eange is 

the gentle anticline which now forms the divide between Sage Creek 

and the tributaries of the Yellowstone. The trend of the fold is nearly 

east and west, and along the axis Bridger Creek, a confluent of Clarks 

Fork, has cut a deep canyon, walled in with Dakota, Jurassic and 

Triassic formations. Oil approaching the valley of Clarks Fork a 

number of irregularly disposed folds or crumples are locally developed in the Mesozoic beds, but beyond, the strata resume a gentle 

north arid south dip which continues with undulations to the Yellowstone on the one hand and to the Stinking Water on the other. 

Toward the southwest a gentle fold in Laramie and Wasatch strata 

forms the remainder of the divide to Heart Mountain. In the vicinity of this peak and also west of Clarks Fork these flexures blend 

with the north and south system of folds developed with the Absaroka 

Eange.

In the foregoing description so much of the Big Horn basin has been 

considered as is structurally peculiar. Within the zone thus defined 

about the periphery of the basin that is, towards the center of the 

depression the strata have undergone hardly more than an occasional 

flexure, and the formations occupy a practically horizontal position.

The Wind River Mountains. These were observed only from the 

north. On this side, the range appears as a massive body of Archean, 

with a belt of Paleozoic measures at the base. The general trend is 

N. 60° W., and the sedimentaries dip from 30° to 80° north-northeast, 

locally reaching the vertical. The fold is apparently a simple anticline. 

The Carboniferous quartzites, which form the slope of the range for 

1,000 to 1,500 feet above the base, are somewhat thicker than in the 

other mountain ranges examined, and, moreover, are accompanied by 

a series of shales not elsewhere encountered. The blue limestone is
ELDRIDGE.] STRUCTURE WIND RIVER RANGE. 47

also heavily developed. The Silurian appears about as in the Big : 

Horn Mountains, but the shales of the Cambrian are less conspicuous. 

Terminal moraines occur at the entrances to the many canyons. Prominent among these is one across the mouth of the canyon of the South 

Fork of Wind Eiver. This is from 400 to 500 feet high and between 1 

and 2 miles broad at the summit, covering a considerable area of the 

older Mesozoic formations. Existing glaciers also are reported on the 

higher peaks of the range.

Within a zone of 10 to 15 miles along the base of the Wind Eiver 

Mountains, from the vicinity of Fort Washakie east, there are several 

prominent anticlines, some of which are of special interest from the 

presence of petroleum springs along their axes. The two most important have been referred to by others as the Shoshone and Washakie 

anticlines.

The Shoshone anticline is the most western. It has a N. 50° W. 

trend, and a length of 12 to 15 miles, the center being opposite Fort 

Washakie and 2 or 3 miles north of it. The western end lies in the 

vicinity of Sage Creek, 7 or 8 miles northwest of the fort, while the 

eastern is at an equal distance east-southeast of this point. The strata 

north of the axis dip 15° to 20°; south of it, between 45° and 80°. 

The center of the anticline is occupied by the" Red Beds, which, besides 

forming the bottom of a valley 2 or 3 miles wide, also constitute its rim. 

The valley is cut transversely by the Little Wind Eiver, and appears 

therefore as an amphitheater on either side of the stream, extending 

4 or 5 miles to the west of it and 1 or 2 east. The Jurassic and Cretaceous measures lie about the Trias in successive outcrops, the Montana 

shale constituting the valley bottom between the anticline and the 

base of the Wind Eiver Eange. The Laramie measures have been 

deflected to the north or nortfieast by this fold and are seen outcropping in the low bluffs to the north of Lower Sage Creek at its confluence with Little Wind Eiver. The western half of the anticline has 

been considerably denuded by the drainage of Sage Creek, and from 

this cause aud from the presence of one or two minor folds, the lines of 

outcrop are somewhat irregular. The eastern end of the fold is a prominent ridge 100 to 200 feet high, composed of the Niobrara, and encircled about the base by the Montana shales. The axis of the fold is at 

this end slightly deflected to the east, towards the Washakie anticline 6 

or 7 miles off. The center of the Shoshone anticline displays an important petroleum spring, a mile or two west of the channel of Wind Eiver, 

and a very large hot spring in close proximity to the stream.

The Washakie anticline lies about 7 miles southeast of the. Shoshone, 

the northern end of the former overlapping a little the southern end 

of the latter. Where confined -to the Montana shales the fold does 

not appear above the general level of the prairie, but the Eiobrara 

j and underlying beds form a prominent ridge which extends from the 

point above mentioned southward to the head of Twin and Beaver
48 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

Creeks. Below Lander the anticline is cut transversely by the Popoagie, and again, several miles to the south by its branch, the Little 

Popoagie, the latter stream now occupying its axis to the forks of 

Twin Creek. From the Popoagie south, far beyond Dallas, the central rocks exposed are the Red Beds, which along Little Popoagie are 

eroded to a depth of several hundred feet, forming lofty cliffs east of the 

stream and others less lofty west of it. North of the Popoagie the 

ridge chiefly consists of the Cretaceous series, the Niobrara occupying 

over half its length along this portion. Between the ridge and the 

sharp bluffs of the Laramie to the east is a broad valley of Montana 

shales; west of the ridge the Laramie does not occur, and the Montana and underlying beds are bent into a well-pronounced syncline 

which occupies the space to their westernmost outcrops along the base 

of the range. Almost on the axis of the Washakie anticline, near the 

northern extremity of the Niobrara ridge, is the Washakie oil spring, 

and a little north of Dallas, in the canyon of the Little Popoagie, are 

several oil wells of large capacity.

Northeast of th'e Washakie and Shoshone anticlines the flexures 

belonging to the Wind River system are but slight undulations, hardly 

visible except under favorable circumstances of outcrop. Along the 

immediate base of the range, however, the strata are here and there 

thrown into folds which, while not of the extent and size of the Shoshone and Washakie folds, are nevertheless well denned and contribute 

to both the structural and topographic features of the country. These 

minor anticlines usually occur in the Mobrara or in the underlying 

formations to a horizon near the top of the Trias.

The Wind River S^sm. This was crossed twice in the present reconnoissance: once on the Embar and Fort Washakie stage road j and once 

on the road leading from Lander down Wind River to its canyon in 

in the Owl-Rattlesnake Range. On the former line the folds encountered belonged either to the Owl Mountain or Wind River systems, and 

have been described. On the latter road the valley between ranges 

is much broader and the area beyond the region of the mountain folds 

proper much greater. In crossing on this line the beds of the Bridger formation occupy the valley for nearly its entire width, covering 

all the older Cretaceous formations. A single flexure of importance 

was observed in the Tertiary beds. The axis of this lies about 12 

miles north of St. Stephens Mission, and extends east and west bebetween 5 and 10 miles, forming a noticeable elevation in the otherwise flat valley. The rise of the arch is but slight, the beds dipping 

hardly more than 5° or 6° north and south. The occurrence of the 

fold is, however, important, and establishes the action offerees in later 

Tertiary times, already noticed in connection with the Wasatch Tertiary both in this basin and in the Big Horn.

For a description of the region, east of Wind River the reader is
U. 8. GEOLOGICAL SURVEY BULLETIN NO. 119 PL. II

IOIZ.

G

0 I Z 3 4 5FEET

Ufc-l i U=bJ i k^ 

SCALE

SECTIONS OF COAL SEAMS.
EXPLANATION OF PLATE II.

A. Sheridan district; prospects miles east of Beckton; portion above the coal a

mixture of lignitic shale and sandstone. 

B. Sheridan district; mine 5 miles north of Sheridan. 

C. Buffalo district; mine 1 mile east of Buffalo. 

D. Prospect at mouth of No Wood Creek. 

E. Red Lodge district, Montana; No. 1 or Yankee Jim seaui. 

F. Red Lodge district, Monbana; No. 2 seam. 

G. Red Lodge district, Montana; No. 3 seam. 

H. Red Lodge district, Montana; No. 4 seam.
ELDEIDOE.] COAL STRATIGRAPHY. 49

referred to the reports of the Territorial geologists 1 and to the maps of 

the Hayden Survey,2 from which the data for the accompanying map 

have been obtained.

ECONOMIC GEOLOGY. 

COAL.

STRATIGRAPHY.

The workable,coal of the region under discussion is of Laramie age. 

Reports of its existence in the Dakota formation, in the foothills at 

the east base of the Big Horn Bange, 5 miles southwest of Dayton, are 

current. The locality was visited by the writer and the lt coal" found 

to be merely a very carbonaceous sandstone. Coal occurs in the 

Niobrara in the vicinity of the Olarks Fork Canyon, but the seam is very 

irregular a mixture of shaly coal and slate, and of but 2 feet or»2 

feet 6 inches maximum thickness. The chief interest lies in its presence 

in the Niobrara, heretofore not known to be carbonaceous or, indeed, 

except in Canada, to carry even an occasional leaf bed, both of which 

conditions exist here.

The coal beds of the Laramie are distributed throughout the formation from base to summit. No distinguishing features exist for determining the horizon of a particular bed except by direct reference to the 

base of the series or to one of the broad divisions of the formation the 

lower, sandstone division, or the upper, clay division and this only in 

an area where both are present and their relations may be clearly observed. Reference by direct measurement has been impracticable in the 

present reconnoissance, and it has therefore been impossible to establish the absolute position of all the seams encountered. However, some 

are known to occur near the base of the formation, and it is believed 

that others belong to a horizon about midway but in the shaly division 

of the series. «

Beginning at the bottom, the first workable coal bed anywhere 

encountered occurs about 100 feet above the base of the Laramie; the 

second, in some localities, 70 feet higher. With these exceptions the 

seams in the lower or sandy division are thin and unimportant.

In the upper or shaly division the coal seams are numerous and form 

one of its characteristic features. With two or three local exceptions, 

however, all are too thin for economical working, and the coal is 

usually of a poorer quality than that at the base of the formation. 

The exceptions are the heavy beds north and west of Sheridan, east of 

the Big Horn Eange, and a bed about 2 feet thick on Grey Bull, a 

little above the mouth of Meeteetse Greek, in the Big Horn basin.

1 Annual Report of the Ten oorial Geologist to the Governor of Wyoming. Tears 1886-1888 and 1890.

'Maps, U. S. Geol. and Geog. Surv. of the Territories, F. V. Hayden. Parts of Central Wyoming.

And TJ. S. Geol. .and Geog. Surv. of Terr. Geological Map of Portions of Wyoming, Idaho, and Utah.

Bull. 119 4
50 GEOLOGY NORTHWEST WYOMING. [BOLL. 119.

In the lower part of the formation the succession of the component 

strata and of the coal beds is very changeable; and a single coal seam 

of 10 feet in one locality may in another be split into two 8 to 10 feet 

apart, or, in a third, into a half dozen seams embracing a thickness of 

measures of 30 to 50 feet. Such separation is effected by the increase 

of sandstone or slate partings already present, or the acquirement of 

others wholly new. Again, the coal seams themselves may thicken to 

a workable size or diminish to the merest trace.

AKEAS.

The distribution of coal within the confines of the Laramie in the 

region examined is quite general; but the localities of workable coal, 

so far as exposed in outcrop, are limited to four: that east of the Big 

Horn Range; the Bed Lodge district, in Montana; the Sunshine area 

on the western edge of the Big Horn basin; and the Lander district, 

in the Wind Eiver valley. That these four districts, however, embrace all the areas of coal of a workable thickness in this region is 

doubtful, for, from the general manner of occurrence of this mineral in 

the West, it is quite possible that beds of sufficient size may exist at 

other points, beneath the formations of later age.

Powder Eiver field. This name has been assigned by the Territorial 

geologist, Dr. L. D. Ricketts, 1 to the area of Laramie east of the Big 

Horn Mountains. It extends from a parallel at least 20 miles south of 

Buffalo north far into Montana and in an easterly direction it covers 

nearly half the distance to the Black Hills. Coal probably underlies 

much of it. Examination in the present reconnoissance has been confined to the western periphery and the region about Sheridan in the 

valley of Goose Creek.

The western rim of the Laramie for the greater part of its length is 

clearly defined by the outcrops of the more prominent sandstones at the 

base, these often constituting a line of low ridges, 6 to 10 miles from the 

foot of the Big Horn Range. Along other portions of the rim, however, 

the sandstones are broken down, the ridges disappear, and the limiting 

line of the formation, is concealed beneath superficial deposits. The 

general trend of this line and consequently of the coal horizon at the 

base of the formation, from the vicinity of Trabing, its southern end, 

to the Montana line, is N. 35° W. It passes close to the town of Buffalo, 

either a little to the east or west, continuing thence to the valley of 

Little Goose Creek. Along this portion of its course the edge of the 

formation was not followed but its trend is apparently direct, except, 

perhaps, in the vicinity of Massacre Hill, or the divide between Piny 

and Prairie Dog Creeks, a region of topographic peculiarities. On Big 

Goose Creek the basal sandstones of the formation outcrop about 1£ 

miles above Beckton Post-office, passing thence directly across ridges

1 Annual Keport of the Territorial geologist of Wyoming. January, 1890, p. 38.
ELDBIDOE.] COAL POWDER RIVER FIELD. 51

aiid valleys to a point on Tongue Eiver a mile above Dayton. North 

of Tongue Eiver, for much of the distance to the State line, the sandstones form a series of low ridges, denning the lines of drainage and 

giving to the streams a direction parallel with the strike of the beds. 

The dip of the strata along the western edge of the Laramie is usually 

less than 25°, shallowing rapidly to 5° of even less, as distance from the 

mountain increases. Over the interior of the Laramie area the strata 

vary in the direction of their dip, but the amount of dip is everywhere 

slight, rarely over 5° or 10°.

The stratigraphical distribution of the coal in the Laramie of the 

Powder Eiver field has never been determined in detail. Seams from 

1 inch to 10 feet thick are encountered at various horizons almost, 

indeed, from base to summit. The workable seams, however, are apparently of two horizons, near the bottom and midway the series.

The lowest coal recognized is that opened in the vicinity of Buffalo, 

which is probably within 200 feet of the base of the formation; but 

nowhere else along the western rim has a Avorkable seam either been 

observed or reported at this horizon. The next highest seain of 

economic value is that opened on Big Goose Creek, about 2£ miles 

east of Beckton and just north of the road to Sheridan. This seam 

occurs several hundred feet above the base of the formation, in the 

more shaly series of beds usually forming the middle and upper portions of the Laramie. Five miles north of Sheridan, on the line of the 

Burlington and Missouri Eailroad, a mine has been opened by drift on 

a seam, the horizon of which is not satisfactorily determined but may 

be either the same as that of the one near Beckton or still higher in 

the series, a point that can be settled only by a profile and section of 

the measures from the base up. North of this, still other openings, of 

local importance, occur, and in the Tongue Eiver valley, several miles 

below Daytoii, coal of uncertain horizon is again reported. Several 

hundred feet of shale and sandstone overlie the Sheridan seam, constituting the high region east of Goose and Prairie Dog Creeks and 

extending beyond the Powder Eiver. In this region several outcrops 

and openings have been reported but uo attempt at correlation has 

been made.

The mines in the vicinity of Buffalo are three, and lie to the east, 

north and northeast of the town from 1 to 5 miles. They are opened 

in strata of gentle and somewhat variable dip, but withal 2° to 3° 

eastward. At a recently developed mine, which is 1 mile east of 

Buffalo and of all the openings the nearest to the western rim of the 

formation, the coal is reached at a depth of 103 feet beneath the surface, and presents the general section given in C, Plate n. The coal 

of the Buffalo district varies but little in appearance, and probably 

but little in its chemical constituents, in both particulars being an 

especially typical lignite. The woody structure is maintained in a 

remarkable degree, while the streak is a dirty brown, the fracture
52 GEOLOGY NORTHWEST WYOMING. [Buu.119.

conchoidal, and its resistance to weathering slight. The analysis 

given in the general table at the end of the chapter affords an insight 

into the relative proportions of its components, and its fuel ratio is far 

below the limit usually adopted as the dividing line between lignite 

and bituminous coal. Moreover, both water and ash are high. The 

coal, however, is extensively used for domestic purposes in Buffalo 

and the United States military post, Fort McKinney, and is said to 

afford a considerable degree of satisfaction.

The openings near Beckton are hardly more than prospects, from 

which, however, a small amount of coal has been taken to supply local 

demand. Sec. A, Plate n, represents the seam at the outcrop, but the 

coal was not sampled.

In the Sheridan district but a single mine is at present worked. 

This is on the line of the Burlington and Missouri Railroad, 5 miles 

north of Sheridan, and is the most extensive opening in the Powder 

Eiver field, the main entry extending about 500 feet from the outcrop. 

The section represented in B, Plate n, varies little from that at other 

points in the mine, the coal maintaining itself comparatively clean 

and free from partings with the exception of the clay streak 6 to 8 

inches from the bottom, which is persistent, and local developments of 

slate or bone. The coal is fibrous, jointed and compact, and in texture 

it occasionally resembles a coal of the bituminous variety. In composition, however, it is a lignite, the fuel ratio being generally below 1, 

altho'ugh one or two analyses made by the mine-owners place it at 

1.12 to 1.14. The moisture is high, but the ash is remarkably low, a 

percentage as low as 4 being rarely encountered in this class of coals. 

Another noticeable feature brought out in the analyses of the Sheridan coals is the marked variability in the relative proportions of 

fixed carbon and the volatile hydrocarbons; the samples taken being 

illustrative not only of different localities on the seam but as well 

of different parts of the seam in the same vertical section. This important feature was unlocked for, and whether it will be found general for 

the mine and, indeed, for the field, must be decided by future analyses.

The Sheridan coal is largely used for domestic purposes and is said 

to be satisfactory in this respect. For stationary engines also it 

answers well in the absence of coals of higher grade, but for locomotive 

steaming it is reported too light. It also yields easily to atmospheric 

influences.

The No Wood region. West of the Big Horn Range, at the mouth of 

No Wood Creek, a coal seam has been prospected to the depth of 40 or 

50 feet, showing the section given in D, PI. n. The seam is too much 

split by slate and sandstone partings to be of value, but its presence 

is indicative of the possibilities of the region, which is, perhaps, the 

western continuation of the Powder River field, from which it may have 

been separated by erosion across the crest of the Big Horn anticline.
ELDR1DGE.1 COAL RED LODGE DISTRICT. 53

The coal of the No Wood seam is in appearance and constitution a 

lignite. The single analysis of it shows a higher fuel ratio than that of 

the Powder Eiver field, the upper division of the seam reaching but 

little short of 1. The moisture is also noticeably lower than in the coal 

east of the Big Horn Range, but this can not be regarded general from 

a single sample. The ash is much higher, as anticipated from the 

appearance of the coal, in which the distribution of impurities is 

marked.

The Red Lodge district of Montana. Although this is beyond the 

confines of Wyoming and was but incidentally visited in connection 

with the present reconnoissance, it has so many features important for 

the comparison of coals further south, in the Big Horn basin, that a brief 

reference to it is here made. Sections of the seams thus far opened are 

given in E, F, G, H, PI. ii, and A, B, C, PI. m.

The field was first examined and reported upon by Mr. J. E. Wolff, 

of the Northern Transcontinental Survey, in 1881 or 1882. l Since then 

it has been visited by Mr. W. H. Weed, of the U. S. Geological Survey,2 

from whom also a brief statement has come, in connection with other 

coal fields in Montana. To these two reports the reader is referred for 

more extended information than is given below.

^ Scale.

Fig. 1. Section showing relative positions of coal seams.

The field extends several miles east and west of Eocky Fork, occupying a belt 3 to 5 miles wide along the northern base of the Absaroka 

Eange. The productive coal-measures occur in a zone of 1,000 feet, 

apparently somewhere in the middle of the formation, but the exact 

stratigraphical position has never, so far as known, been determined. 

The coal-measures, along their northern edge, outcrop with varying 

southerly dip in the region of Eocky Fork about 20°. To the south 

this dip gradually shallows to horizontal or slightly undulating, which 

position is maintained to the fault line at the base of the mountains, 

a distance of 3 to 4 miles. The coal horizon abuts against the faultplane at a considerable distance beneath the surface.

The relative positions of the coal seams already opened, in the upper 

half of the zone, are shown iu the accompanying section (Fig. 1).

In addition to these, seven others are reported within 600 or 700 feet 

below, five of which are said to be of workable thickness.

A point of special interest in the coal seams of this district is the 

number of partings of slate or other material. These vary in thickness

1 Vol. xv. Tenth Census of the United States, p. 755 and plates.

» Engineering and Mining Journal, Vol. un, No. 20, May 14, 1892, p. 521.
54 GEOLOGY NORTHWEST WYOMING. t«n.L.no.

from yL of an inch to 6 or 8 inches, on the one hand too thin for separation in mining and of necessity going into the coal shipments, on the 

other hand too thick to pass into the coal product and therefore requiring separation in the mine. This is, moreover, a feature of many of the 

seams in the Rocky Mountains in southern Montana, and yet both vertical and horizontal beds are mined with advantage. In illustration 

of the effect of inclusion in the shipping product of partings too small 

for separation in mining, two samples, Nos, 117 and 118, were taken at 

the same section in the slope of the No. 4 seam, the former including all 

partings finding their way into the shipments, the latter of clean coal. 

The analyses show a diminution of one-third in the amount of ash in 

the coal from which the partings were excluded.

The analyses of the Eocky Fork (including Bear Creek) coals show 

them to be of a higher grade than any sampled elsewhere during the 

present reconnoissance. The fixed carbon is higher and the volatile 

combustible matters, the moisture and the ash, are lower than in the 

others, while the fuel ratio is very noticeably advanced.

Bofore passing from the consideration of the coals of the Rocky Fork 

district, attention is called to the sample No. 120, obtained from a Bear 

Creek prospect. It illustrates the- slight change that some coals of the 

lignite class occasionally undergo in the mine, even after long exposure, 

in the present instance three years having elapsed since the face was 

cut, and in sampling but an inch or two having been removed. This 

coal is well up to those taken at depths in other portions of the district, 

even allowing for a possible higher quality of coal.

The front of tlie Absarolca and Shoshone Ranges. From the Rocky 

Fork coal field, which extends to a point 7 or 8 miles north of the 

Montana-Wyoming line, southward to the Sunshine district, the northern limit of which is between Meeteetse and Grey Bull Creeks, there 

are numerous exposures of coal, but all, so far as explored, show a seam 

too thin for economic development on an extended scale, and with one 

or two exceptions even below the limits of a working thickness to supply local demands. The coal beds of this belt occur both in the lower, 

more sandy division of the Laramie, and in. the upper or shaly zone 

of the formation. In the former but a single seam has been observed, 

this extending through the entire length of the belt with the preservation of all its characteristic features. In the shaly division the 

seams are numerous, but generally either very thin or of a low grade 

of lignite intermingled with dirt streaks. The seam of chief importance in this division has a thickness of 2 feet of clean coal and is 

exposed on. Grey Bull above the mouth of Meeteetse Creek (H, PI. m). 

The chief exposures of the lower coal are: on a branch of Line Creek, 

near the boundary of Wyoming and Montana; along the base of the 

Laramie in Heart Mountain; on Sage Creek, near the Frost ranch; 

and at Arland on Meeteetse Creek. Besides the foregoing seams and 

their exposures, two others of undetermined geological horizon exist
EXPLANATION OF PLATE III.

A. Red Lodge district, Montana; No. 5 seam. 

B. Red Lodge district, Montana; No. 6 seam. 

C. Red Lodge district, Montana; Bear Creek mine. 

D. Big Horn Basin; Nutting outcrop; near Montana-Wyoming line. 

E. Big Horn Basin; Frost outcrop; Sage Creek south of Stinking Water. 

F. Big Horn Basin; Brundage outcrop; SE. spur of Meeteetse Mountain. 

G. Big Horn Basin; Arlaud mine.

H. Big Horn Basin; Grey Bull River; outcrop, 1 mile above mouth of Meeteetse Creek. 

I. Big Horn Basin; Sunshine district; outcrop, north bank of Grey Bull River, 1 mile 

below mouth of Iron Spring Creek.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 119 PL. Ill

I27

E

H

.123

135

SECTIONS OF COAL SEAMS.
H.miinon.1 COAL SUNSHINE DISTRICT. 55

high up on the northeast slopes of Meeteetse Mountain, at the head of 

Carter Creek arid the north fork of Sage. (F, PI. in.)

The coal bed in the lower portion of the Laramie occurs between 100 

and 150 feet above the base of the formation. It is included in a narrow zone of lignitic clays, which are quite generally underlain by a heavy 

bed of white sandstone and overlain by one of yellow. The seam itself 

is usually made up of two benches of coal, separated by a 2 to 4 inch 

band of brown lignitic slate, which Aveathers a milky white. These 

features are so pronounced and persistent that, with the constant position of the bed, they serve as a general means of its identification. Sections D, B, G, and I, PI. in, and B, PI. iv, give the general character 

of the seam, excepting that in the region affording the last two (the 

Sunshine district) the coal has increased to workable thickness.

The coal of this horizon usually lies vithin the region of mountain 

folding, either on the flanks of the main uplifts or included in the 

subordinate (parallel) folds along their base. The flip is, therefore, 

rarely less than 15°, often 45°, and occasionally 70°, and the direction 

generally eastward, except where, as on Sage Creek, it is included in a 

subordinate fold, either eastward or westward, according to the side 

of the flexure upon which it is.

In appearance the coal is hard, black, of bright and sometimes oily 

luster, and bears a close resemblance to coals of the bituminous variety. 

It is, however, a lignite, with high moisture contents, ash from 6 to 15 

per cent, and a fuel ratio considerably below 1. This applies also to 

the coals of uncertain horizon in the slopes of Meeteetse Mountain, and, 

indeed, to the seam in the upper Laramie series, on Grey Bull, near the 

mouth of Meeteetse Creek. The latter coal, however, has a more general resemblance to lignite than the former.

Sunshine district. This embraces an area approximately 9 by 15 miles, 

the greater dimension being east and west. The northern limit is between Grey Bull and Meeteetse Creeks; the southern,probably between 

Gooseberry and Grass Creeks; the western, a north and south line a 

few miles west of Sunshine Post-office; and the eastern, arbitrarily 

taken, along the edge of the region .of subordinate folds, a few miles 

east of Enos Creek, a tributary of Gooseberry from the south. It is 

highly improbable that this entire area is underlain with coal, but the 

general distribution of known outcrops and the thickness of the beds 

render it a region of considerable possibilities.

The coal area of the district is separable into a main body lying 

almost wholly east of Wood River, and an inlier west of this stream, 

the two separated by erosion along an anticlinal fold.

The coals occur in both the lower and upper divisions of the Laramie, 

but the most important seams are found in the former. Two occur in 

this division: the lower and larger, Sec. I, PI. in, and Sections A, B, C, 

D, H, PI. iv, about 100 feet above the base of the formation; the upper.
56 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

E, PI. iv, smaller and of local prominence only, 70 feet higher in the 

series. The lower, by its stratigraphical position and component layers two benches of coal separated by a characteristic slate is identified with that already described at this horizon further north. In the 

upper division of the Laramie the single seam of importance is that 

shown in Sec. G, PI. iv; it occurs in the lower portion of this division. 

The observed northernmost outcrop of the large seam ne"ar the base 

of the formation is in the banks of Grey Bull, 1 mile below the mouth 

of Iron Spring Creek arid about 7 miles north-northeast of Sunshine 

Post-office. The outcrop presents the appearance in I, PI. in. The dip 

of the measures is here about 7° N. 60° E., or down stream. West of 

this the coal rises in the bluffs of the valley, and after one or two gentle 

flexures reaches the line of its north and south outcrop a little above 

the mouth of Wood Eiver. North of Grey Bull this outcrop passes 

into the prairie and, with one or two irregularities of trend caused by 

local folds, finally unites with that passing south from Arland. Beneath 

how much of the area north of the stream the coal maintains a workable thickness is undetermined, the examination not having been carried beyond the immediate river valley. South of Grey Bull the coal 

horizon passes into the bluffs in the forks of this stream and Wood 

Eiver, crosses the channel of the latter between 1 and 2 miles above its 

mouth, and thence enters the high ridge to the east, in which it continues to Gooseberry Creek, a distance of 7 or 8 miles. On this line of 

outcrop the only exposure of importance encountered was in the banks 

of Wood Eiver, 4 to 5 miles below Sunshine, where is a seam comprising two benches of coal separated by 2 to 4 inches of slate. This, 

except for the thinning of the upper bench to 5 or 6 inches, closely 

resembles the bed of general occurrence along the range to the north, 

and in its main divisions, also the larger seams of the Sunshine district. 

There is thus an indefinite area in this vicinity over which the main 

coal bed has either been reduced below workable thickness or has been 

split into a number of minor seams, as on Gooseberry Creek, on this 

same line of outcrop, where the section in F, PI. iv, is to be seen. 

South of Gooseberry Creek the basal series of Laramie rocks was not 

followed.

Within the periphery of the main body of Laramie in the Sunshine 

district the several anticlines already described in the structural chapter each expose a rim of the lower coal-measures of the formation. 

These have not all been explored for coal, but in two instances seams 

of workable thickness have been, one observed by the writer, the other 

reported to him. The anticlines that have brought to the surface these 

seams are the one crossing Gooseberry Creek, 2 miles above Iron 

Spring, and that south of Gooseberry Creek, 2 or 3 miles below the 

mouth of Enos Creek.

The exposure of the coal horizon in the former or upper anticline is
EXPLANATION OF PLATE IV.

A. Big Horn Basin; Sunshine district; outcrop, Wood River, 1-J- miles above its

mouth. 

B. Big Horn Basin; Sunshine district; outcrop, north side Sunshine Gulch, 2 miles

NNW. of Sunshine post-office. 

C. Big Horn Basin; Sunshine district; outcrop, tributary Sunshine Gulch, 2f miles

NW. Sunshine post-office. 

D. Big Horn Basin; Sunshine district; outcrop, tributary Sunshine Gulch, 3 miles

NW. Sunshine post-office. 

E. Big Horn Basin; Sunshine district; outcrop, tributary Sunshine Gulch, 3 miles

NW. Sunshine post-office. An upper seam locally developed. 

F. Big Horn Basin; Sunshine district; outcrop, south bank Gooseberry Creek, 4

miles SE. Sunshine post-office. 

G. Big Horn Basin; Sunshine district; outcrop, Gooseberry Creek, 2 miles above

mouth of Enos Creek. 

H. Big Horn Basin; Sunshine district; outcrop, tributary of Gooseberry Creek from

south, 2 or 3 miles east of Enos Creek. 

I. Big Horn Basin; Embar district; Smith prospect; outcrop, 4miles NE. of Embar

post-office. 

J. Wind River Basin; Lander district; mine, 8 miles NE. of Lander.
U. 8. GEOLOGICAL SURVEY BULLETIN NO. 110 PL. IV

1001

B

M

131

U

140

H

1003

136

1004I

1008

1009

SECTIONS OF COAL SEAMS.
COAL SUNSHINE DISTRICT. 57

about 10 miles long, and the workable coal is reported on the northeastern side of the fold in a sharply eroded gnlch entering Gooseberry 

Creek one-quarter to one-half mile above Iron Spring. Here an opening is said to show 5 feet of coal in 3 or 4 benches separated by partings of slate from 1 to 3 inches thick. The bed is probably identical 

with the main seam of the district, and the appearance of the coal is 

said to be the same in both. The area of workable coal in this portion 

of the district is undetermined.

The anticline below Enos Creek presents an exposure of the coal 

horizon of 4 or 5 miles. The coal outcrops in workable thickness near 

the northern end of the topographic basin eroded along the axis of the 

fold, having a dip of 5° northeast. Two beds are present, separated 

by 10 to 20 feet of sandstone and shale, the entire section being given 

in Fig. H, PI. iv. The upper bed affords 3 feet 7 inches of workable 

coal; the lower 2 feet 8 inches, separated into three bands. The latter 

somewhat resembles the seam so generally present near the base of the 

formation north of the Sunshine district, there being two main benches 

separated by a bluish white slate parting. The bed widens to 12 feet 

a few hundred feet southeast, the amount of coal remaining the same, 

but its benches being further separated or split into minor layers by 

fresh partings. The sandstone layer separating the two main beds is 

also variable from, point to point. The variability of this series of coal, 

shale and sandstone renders an estimate of the possible productive 

areas of the district very difficult. Only careful prospecting along the 

outcrop of the beds and drilling in the interior portions will furnish reliable answers to questions of this nature.

The inlier of Laramie west of Wood Biver, which is in structure a 

syncline, is approximately 8 or 10 miles long by 2 or 3 wide. It is completely encircled by the horizon of the coal, the chief exposures of the 

seams being near the southern end, from 2 to 4 miles northwest of 

Sunshine Post-office, in the bluffs of Sunshine Gulch and its tributaries. The beds here dip 10° to 35° northwest to north, according to 

their position on the periphery of the syncline, the axis of which has a 

general north and south trend. The sandstones of the formation are 

heavily developed, and the individual beds for 150 or 200 feet above the 

base are readily recognizable by their thickness, persistence and color. 

Those immediately underlying and overlying the main coal seam are 

particularly prominent, the former being a heavy bed of white sandstone, the latter of yellow, characteristics that are maintained, not only 

over the Sunshine district, but along much of the area bordering the 

mountains to the north and south.

Two beds of coal occur in this region. The Jpwer is the important 

one, the upper, 70 feet above, being but 2 feet 8 inches thick and apparently of local development only. Exposures of the lower seam are given, 

in Sections B, C, and D, PI. iv, and its identity with that generally
58 GEOLOGY NORTHWEST WYOMING. [BULL. lift.

developed at this horizon to the north of this district is clearly established by comparisou of the component layers; two broad benches of 

coal appear in Sections B and D, PI. iv, more or less split by narrow partings, indeed, but separated from each other by the usual 2 to 

4 inch band of brown carbonaceous slate, weathering bluish white. 

Section 0, taken at a point midway between the localities of B and D, 

also shows this parting, but there has apparently been a local interpolation of sandstone and shale in the upper part of the seam. The 

extent of outcrop covered by the three sections is about 1 mile, but 

other prospects, showing the seam still of workable thickness, are 

reported farther west, which would increase the length for this region 

to between 1 and 2 miles. Coal also outcrops at other points about the 

syncline, but the seams were of necessity left unopened.

Comparison of the lower seam of the Sunshine district with those of 

theEocky Fork region, shows a similarity between them in the proportion 

of coal to partings, and in the distribution of the latter throughout the 

seam, that enables the statement to be made that, notwithstanding the 

amount of dirt contained in the Sunshine beds, they can be economically 

worked on a large scale.

The coal of the lower seam in the Sunshine district is of two varieties : that of the upper bench above the middle parting of brown or 

bluish white slate is fibrous, dry and brittle, with a brown streak, and 

tendency to rapid weathering; the lower bench, on the contrary, has a 

black streak, is oily in appearance, hard, only slightly fibrous, breaks 

in blocks, and resists weathering far more than the upper coal. The 

physical properties of the lower bench indicate it to be of the better 

quality, and this implication is borne out in the chemical analysis of the 

few samples taken.

The chemistry of the coal shows it to be lignite. Its true value as a 

fuel can not here be correctly estimated, owing to the necessarily few 

samples and their proximity to the outcrop of the seam, but the analyses 

combined with a field acquaintance with the coal warrant the statement that while it may fall a little below the coals of the Eocky Fork 

mines, it will yet compare favorably with them upon being opened. 

The fuel ratios of the samples are, with one or two exceptions, very low, 

but it is believed that the higher ones will more nearly represent the 

character of the coal. The ash is comparatively low; the moisture 

comparatively high.

The coal is, in its combined physical and chemical properties and in 

the size and character of the seam, superior to other coals of the Big 

Horn basin, and by reason of this the Sunshine district is to be recommended for private exploration to individuals or corporations directing 

their efforts toward opening this intermoutaue region to commerce and 

settlement.

The upper or shaly division of the Laramie in the Sunshine district
(p

COAL SUNSHINE AND EMBAR DISTRICTS. 59

has but one coal seam of prominence, although many from an inch to a 

foot exist wherever the series has been preserved from erosion. The 

seam referred to outcrops on Gooseberry Creek opposite the niouth 

of Middle Fork, about 2 miles above Bnos Creek. It is represented 

in Sec. G, PI. IT. There are 3 feet 6 inches of coal, separated twothirds the way from bottom, to top by a 7-inch band of black slate, 

which is locally very carbonaceous. The strike at the outcrop is N. 50° 

to 70° W., but the trend of the strata in the vicinity is variable by 

reason of the folding to which they have been subjected. The dip of 

of the coal is 10° southwest. The extent of the seam is undetermined. 

The appearance of the coal is much more that of a typical lignite than 

the coals of the lower division of the formation, and the chemical analysis shows it also to be slightly higher in water, with a low ash, and a 

very low ratio between its fixed carbon and volatile combustible matter.

The coal of the Sunshine district is said to outcrop as far south as 

Grass Creek, and, again, on the Middle Fork of Gooseberry, probably 

along the western rim. of the Laramie. So far as observed by those 

reporting it, the seams are not of workable thickness, but in an unprospccted region of such rapid variation this signifies but little.

Emlar district. The exposure of coal next south of the Sunshine 

district is the Smith prospect, 4 miles northeast of Embar.

The coal lies at a distance of between 3 and 4 miles from the base of 

the Owl Mountains and the seam is somewhat beyond the area of the 

la,rger folds which there exist. The locality of the outcrop is in a point 

oFLaramie projecting southeastward between Cottonwood Creek and 

the North Fork of Owl Creek. The edge of the formation lies in the 

bluffs north of the latter stream, and opposite the forks turns north and 

passes into the high ridge beyond Cottonwood. '

The coal seam is of the lower Laramie series. The section at the 

outcrop is given in I, PI. iv, arid shows the coal to be below workable 

thickness. The dip is here 5° east, but the strata of the region are 

slightly folded and the dip consequently somewhat variable. The coal 

is a bright, hard, and oily-looking lignite, higher in its fuel ratio than 

some other coals of the Big Horn basin. The ash is low, but the water 

content is one of the highest met with.

The information concerning the occurrence of coal in the Big Horn 

basin does not show it to be a region of general promise. The nature of 

a reconnoissance precludes detailed examination, but the Laramie has 

been crossed on many lines, and it is believed, that little if any coal of 

importance has escaped attention. Even if some coal fields have not 

been found, the future lines of examination by private individuals are 

here suggested. Of tlie different areas the Sunshine district is the most 

favorable for coal enterprises, but it requires the most careful and 

detailed examination before investment and development.

The important coal beds of the Wind Itiver valley are chiefly con-
O ^ '

60 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

fined to the lower or sandstone division of the Laramie, the seams probably corresponding to those of the same stratigraphic horizon in the 

Big Horn basin.

Muddy Creek field. This embraces the area of Larainie immediately 

south of the Owl Mountains. Several small seams were observed near 

the base of the formation in the two promontories southeast of the Mail 

Camp at a distance of 2 to 4 miles from the Owl Creek Range, and 6 

or 7 miles farther east, in the southern face of the outer ridge, between 

3 and 4 feet of coal are reported dipping southeast 15° to 25°. The 

coal is a lignite, of use for domestic purposes but unfitted for the heavier 

demands of commerce. This coal is on the reservation of the Shohone and Arapaho Indians, and at present not open to prospectings 

or development by private individuals.

Lander field. This field is at present the most important in the Wind 

River valley. It lies 8 miles northeast of Lander, the coal being opened 

just south of the confluence of the Big and Little Popoagie Creeks. 

The basal sandstones of the Laramie here outcrop in a prominent line 

of bluffs, dip northeast about 13°, and pass beneath the prairie beyond. 

The area of workable coal is unknown, but is probably several square 

miles, with portions where the seams would be unprofitable to open. 

Northwest of the Big Popoagie the coal has not been opened and little 

is known of the character of the seam in this direction. The measures 

pass across the prairie to the valley of Little Wind River, where they 

are found in the bluffs north of the stream, dipping slightly northeast.

A section of the Lander seam is shown in Sec. J., PI. iv. The coal 

is fibrous, bright arid hard, and has a splintery fracture, but weathers 

rapidly. In appearance it resembles a lignite of the higher class, and 

the chemical analyses place it among the better coals encountered in 

the reconnoissance.

Upper Wind River region. On the Upper Wind River and its tributary, Warm Spring Creek, and also on several other streams in this 

vicinity, coal is reported in seams of a thickness somewhat below the 

requirement for economic working. The locality was necessarily left 

unvisited, but three samples were sent by owners of properties or 

their representatives, the analyses of which have been incorporated 

in the general table at the close of the chapter. The samples sent did 

not coke, and they still appear to belong to the class of lignites, but 

their high place in the scale of the coals of the Big Horn and Wind 

River basins is clearly perceptible upon comparison of analyses, and 

their quality, and their position within the more massive part of the 

mountains, merit for them special attention in the future.
CHEMICAL ANALYSES.

District.

f

Sheridan .......... <

I 

Buffalo ..............

No Wood ..........

Lander ............ 

i

f 

Clarks Fork .......

Sage Creek ........

Mine or prospect.

5 miles N. of town .... 

......do ...............

......do...............

......do...............

......do...............

1 mile E. of town... .. 

No Wood .............

......do ...............

8 miles NE. of town . . 

......do ...............

The slope, No. 4 seam . 

......do ...............

..'....do ...............

......do ..............

......do ...............

......do ...............

Wood River ..........

Sunshine Gulch, No. 1. 

......do...............

Tributary of Sunshine Gulch, No. 2.

Locality in mine.

......do.......................

Breast of return (air) entry . . 

Room 125 feet from outcrop . .

Sideof entry, 40 feet from outcrop.

Room near slope, 250 feet 

down. 

Room near slope, 200 feet 

down. 

From side of slope, 830 feet 

down.

......do.......................

Considerable distance in. ....

Surface. Sample from A bed 

(top). 

Surface. Sample from B bed 

(bottom).

......do.......................

Surface. Blufl'at stream level . 

......do.......................

......do.......................

......do.......................

Surface pit. ..................

......do.......................

Remarks.

......do...............

......do...............

100 feet southeast of 

112-114. Fresh.

Fresh. Cover, 103 feet. 

6 to 12 months idle; 

top. 

6 to 12 months idle; 

bottom.

......do...............

Comparatively fresh ; 

included small partings. 

Comparatively fresh ; 

clean coal. 

Comparatively fresh .

Top ..................

Exposed 6 to 10 

mouths.

Top ..................

Whole................

Top ..................

Bottom of series occurring in other pits.

T

n

F

5 

5 

5 

6 

2 
CHEMICAL ANALYSES Contin

District.

Do...............

Do...............

Mine or prospect.

Tributary of Sunshine Gulch, No. 3. 

......do...............

......do ...............

Tributary of Sunshine Gulch, No. 4.

Tributary of Gooseberry Creek. 

Gooseberry Creek. 

Smith ................

Locality in mine.

......do.......................

......do.......................

......do.......................

.:....do...... .................

Surface. Bluff, edge of stream.

...... do........ ...............

Remarks.

Whole. ...............

Seam overlying that 

of the foregoing 

three prospects.
ELDBIDQE.] OIL IN WYOMING. 63

PETROLEUM.

The oil resources of Wyoming have already been described in a preliminary manner by the territorial geologists, Drs. Samuel Aughey and 

Louis D. Ricketts, 1 and to their reports the reader is referred for more 

extended information than is here given.

The petroleum observations during the present reconnoissauce were 

limited to such localities as lay directly in the line of exploration. 

These were the vicinity of Fort Washakie, the region about Dallas, and 

the neighborhood of Bonanza, on No Wood Creek in the Big Horn 

basin.

The petroleum in each of these localities occurs along an anticlinal 

axis, coming to the surface in two instances in strata of Niobrara age, 

in the other in the Triassic Bed Beds. The structural details of the 

anticlines have been given.

The petroleum spring of the Shoshoue anticline, 2 or 3 miles northeast of Fort Washakie, occurs in a broad flat just off and west of the 

main valley of the Little Wind Kiver, closed in by a low escarpment 

of Triassic Ked Beds. Its position is near the axial line of the anticline, perhaps a little to the southwest of it. The escape of the oil 

at this point, as well as of the great hot spring 1 mile to the -southeast, is probably due to the fracturing of rocks along the axis of the 

fold, where the bending has been sharper than elsewhere. The fold is 

asymmetric, the strata on the southwest dipping from 45° to 80°, those 

on the northeast 15° to 20°. The dip, however, flattens considerably 

on either side as distance from the center is gained.

The petroleum comes to the surface through a wash that occupies 

the flat, but the Ked Beds are just beneath, their horizon being roughly 

estimated at about 500 or 600 feet below the summit of the formation. 

The oil, together with a small amount of gas and water, rises iu a 

number of little springs within an area of 100 or 200 square yards. A 

hard crust of asphalt has been formed about the springs by the evaporation of the more volatile hydrocarbons. The oil is brownish black, 

and evidently heavy, though its gravity was not measured. The 

asphalt from this deposit has been very satisfactorily employed at the 

military post near by in the construction of walks and for other purposes in and about the buildings. The oil is occasionally used in the 

crude state as a lubricant.

A second oil spring, to which the name Washakie has long been 

applied by Indians and others, occurs 8 or 9 miles southeast of the 

first, near the northern end of the long ridge of the Washakie anticline. 

The oil rises to the surface nearly in the axis of the fold, in somewhat 

sharply crumpled Mobrara strata. The Mobrara is a series of argillaceous, arenaceous and calcareous shales, and it is apparently in

r 1 Ann. Report, Territorial Geologist, Jan., 1886, Laramie, Wyo.; Ann. Keport, Territorial Geologist, 

Jan., 1888, Cheyenne, Wyo.
64 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

the somewhat more sandy varieties that the oil here seeps to the surface. 

The amount of seepage is small, collecting slowly in two or three little 

holes dug for the purpose. The petroleum saturates a belt of strata 

from 10 to 20 feet wide, and nearly 100 feet in length. The spring has 

long been famous among the Indians for its healing properties.

The Dallas oil field is 12 to 15 miles southeast of Lander, near a 

post office of the same name. This region was designated by Prof. 

Aughey as the Shoshone oil field. The central feature is the anticlinal 

structure, at the western end of which is the Washakie Spring. It 

is parallel with the Wind River Eange, from which it is separated 

by a long, narrow syncline. The anticline is several miles wide, the 

center being occupied by the Eed Beds of the Trias, fully 2,000 feet 

thick, one-third of which are exposed along the canyon of Little Popoagie Creek, which here occupies the axis of the fold. The strata dip 

outward 10° to 20°. The oil is said to have been discovered near 

the mouth of Twin Creek as seepage from the rocks along the edge of 

the valley and as saturating a considerable area of the soil and wash 

occupying the bottom. The locality is fully described by both Drs. 

Aughey and Eicketts, and it is desirable in this reference only to 

emphasize the mode of occurrence of the petroleum. At present three 

oil wells have been sunk in the valley bottom, at points forming nearly 

an equilateral triangle, the maximum distance apart of any two being 

about 600 feet. The wells are sunk at the base of the cliffs, a little 

on either side of the anticlinal axis, and are 400, 600 and 1,000 feet 

deep,'respectively. All are productive in a large degree, and have a 

steady surface flow when turned on. They are, however, kept plugged, 

and only so much oil is lost as escapes by accident or comes up outside 

the casing. The product forms an excellent lubricant, and supplies 

the several mining camps, and town and farm requirements, throughout a large adjoining area. The petroleum is said to contain about 

45 per cent of illuminating oil. A strong accumulation of gas is 

acquired by keeping the well closed. The details of various analyses 

and tests to which the product has been submitted are given in Prof. 

Aughey's report for 1886.

The Bonanza district, on No Wood Creek, in the Big Horn basin, 

is again illustrative of the occurrence of oil springs in close proximity to the axis of a strongly developed anticline. The petroleum 

here reaches the surface in two or three small springs in the more or 

less argillaceous strata of Niobrara age near the northwest end of the 

prominent ridge and fold which extends for several miles along the 

western base of the Big Horn Mountains, and to which the name 

Bonanza has been applied. The springs occur in a gulch just within 

the ridge and are but slightly off the central line of the fold. The 

oil is accompanied by a small amount of water and gas, the globules 

breaking and spreading on the surface of the water in a thin irides-
ELDRIDQE.l OIL IN WYOMING. 65

cent film which may be collected by skimming. For some distance 

on all sides the strata are heavily saturated with oil. The product is 

the lightest observed during the recounoissance, and probably contains 

much the largest amount of illuminating oil. The color is green by 

"reflected light and a rich wine by transmitted light. The spring is not 

a large one, affording in its present condition about a barrel a day.

Other springs are reported on the general line of this anticline at 

points 1, 17, 25 and 50 miles south, that 25 miles distant being the 

largest.

Eeports of other petroleum occurrences in the Big Horn basin could 

not be corroborated.

The geologic horizons at which the oil of the foregoing springs finds 

the surface are the Triassic Bed Beds and the Mobrara shales. In 

other portions of Wyoming, particularly east of the Wind Kiver, oil 

appears at the surface in the Trias, the Dakota, and what is regarded 

by Dr. Ricketts as the Fox Hills formation. Minor amounts are also 

found seeping from other formations, as the Benton and Laramie, and 

possibly even some of .the Tertiary beds. The actual source of these 

oils can not be determined with the small amount of data at present 

available. The reservoirs may be the more sandy strata of either of the 

formations mentioned, or there may be one primary reservoir the Triassic sandstones and conglomerates from which the oil has escaped 

to the others, which would then be regarded as secondary reservoirs. 

Transmission would have been greatly interfered with by intervening 

shales, but it is not impossible that a most potent aid to it was derived 

from fissuring. Between the Trias and Dakota, perhaps the two chief 

reservoirs, the deposits of shales are not heavy, and passage from the 

lower to the upper may easily have been established. With the Fox 

Hills such communication across the broad band of Colorado and Montana shales would have been opened with much greater difficulty, and 

perhaps between the Dakota and Fox Hills there may have been an 

intervening source of oil. Very considerable differences exist in the 

gravity and other characteristic of the oils from the various localities, 

but from them little satisfactory evidence as to the source of the oils 

has thus far been adduced.

Regarding structural influences upon the appearance of oil at the surface, it is a significant fact that in nearly every case, whether observed 

by the writer or by the local geologists, the oil escapes at the surface 

along the axis of an anticline or in a region where the rocks have 

been folded, and crushed or fractured in some degree. Fracturing is 

most pronounced along the axis of a fold, and it is here, therefore, 

that the springs, the natural oil wells, are most often found.

The natural occurrences of oil and the success thus far attained in 

the drilled wells, warrant firm and favorable belief in the future of 

the Wyomin g petroleum fields.' 

Bull. 119 5
66 GEOLOGY- NORTHWEST WYOMING. [BULL. 119. 

BUILDINGr MATERIALS.

The building materials of the region explored will be found numerous, 

varied and accessible when the demand is created for them. Granites 

and schists occur in the mountains, and sandstones, limestones and 

clays for the manufacture of brick, on their flanks and over the adjoin 

ing prairies. The variety of grain, color, texture and composition is 

great, and, with the effects of combination, the most exacting demands 

of architecture may be successfully met. With the exception of the eruptive series of rhyolitic tuffs and a few marbles, the same building materials are found as exist in Colorado, which is the leading, as it was the 

pioneer State in the production of architectural and ornamental stones 

of the West.

Among the stones which will be found of special importance are the 

granites of the Archean and the quartzites of the Silurian and Carboniferous, for foundations and the lower courses of higher buildings. For 

the middle and upper portions and for private dwellings there are the 

red Triassic sandstones, and the grey, yellow, and white sandstones 

of the Laramie. The several varieties are coincident in their distribution with the formations to which they belong, but careful search for 

localities of superior stone must be made, for even within the same 

layer the properties vary from point to point. No attempt was made, 

in the work of the past season, to determine these details.

The clays particularly adaptable for brick-making are the Cretaceous, 

although doubtless much of the Wasatch of the Big Horn basin would 

likewise be found suitable. Many horizons in both the Laramie and 

the upper portion of the Montana are well suited to the manufacture 

of pressed brickj in other regions also yielding materials of excellent 

color, durability and strength.

For flagging and paving purposes, the stones, excepting the granites, 

are not well adapted, unless, perhaps, an occasional layer of quartzite 

in the Silurian. None was observed of the hardness and durability of 

the upper beds of the lower Trias in the vicinity of Denver, Colorado.

Limestone and gypsum occur in the Carboniferous and Jurassic, 

respectively, in enormous quantities. The gypsums are very pure and 

from 5 to 30 feet thick. They are distributed about the periphery of 

both the Big Horn and Wind Biver basins, and are also found to the 

east of the Big Horn Mountains, and northward in Montana along the 

Pryor Mountains and the Absaroka Bange.

GOLD.

The only metal at present produced along the route of reconnoissance 

is gold. This occurs about Bald Mountain on the summit of the Big 

Horn Bange a few miles south of the Montana-Wyoming line. The productive strata are a series of red conglomerates and sandstones of 

Archean debris, lying directly upon the Archean; but whether they
BLDBIDGE.] HOT SPRINGS. 67

were local developments of Cambrian age or merely deposits of recent 

times was not determined. They occupy broad flats on the summit of 

the range, between the high, surrounding Cambrian hills. Their material 

was apparently derived from a source near at hand. Thus far mining 

has been only experimental.

HOT SPRINGS.

Three enormous hot springs exist in the Big Horn and Wind River 

basins, the waters of which are in greater or less degree charged with 

sulphur, and salts the nature of which is not determined. The springs 

are located on the Stinking Water just below the canyon between Rattlesnake Ridge and Cedar Mountain; on the Big Horn, 5 miles below 

the base of the Owl Mountains; and on the Little Wind River 3 miles 

below Fort Washakie.

The Stinking 'Water springs. These are the present remnants of 

early geyser action. The original area was about 1 mile square. 

Within this, besides a heavy deposit of calcareous tufa, several old 

geyser cones still exist, from which, however, all traces of activity have 

long since departed. There are also the usual circular depressions from 

10 to 30 or 40 feet deep and 50 to 100 feet in diameter, peculiar to such 

regions. The tufa now forms a broad flat on either side the river gorge, 

about 150 or 200 feet above the present stream level. The flat is 

limited by the higher hills of the Triassic. sandstones and their debris 

of denudation, which constitute a rim 30 to 50 feet high. ' The Red 

Beds also formed the platform upon which the tufa layer was deposited, 

outcropping in the canyon walls with a general dip of 10° to 15° 

downstream, but showing some flexures, with a dip for a short distance 

in the opposite direction. The beds have been more or less altered, 

and deposits of foreign salts have taken place in certain.layers while 

in others the rock itself seems to have -been replaced by matter derived 

from the springs. The present seat of activity is limited to a number 

of springs, of greater or less volume, at the water's edge, or rising 

directly from the bottom of the river through the superincumbent 

waters. At high water nearly all the springs are covered. The temperature was not taken, but the water was warm, not hot. The waters, 

besides sulphuretted hydrogen, contain a greater or less amount of sulphuric acid and arc otherwise considerably mineralized..

The Big Horn Hot Springs. These occur in the axis of an anticline 

parallel with the Owl-Rattlesnake Range. Like the Stinking Water 

Springs, they reach the surface in the Triassic Red Beds. They were 

originally active for a mile or more along the anticline on both sides 

the present river channel, but now are chiefly confined to the eastern 

bank where a heavy deposit of calcareous tufa exists, extending along 

the stream for a half mile with a width varying between 100 and 300 feet. 

The largest spring flows from a -circular hole in the steeply dipping 

Triassic strata, in diameter 20 to 25 feet, and of undetermined depth. 

The body of water coming to the surface through this spring is enor-
8 GEOLOGY NORTHWEST WYOMING. [BULL. 119.

mous, and so hot that cooling1 by passage through an open channel is 

necessary before it can be used for bathing purposes. Besides this 

duct, there are others leading to the river edge beneath and through 

the tufaceous bed. The waters are quite strongly impregnated with 

sulphur and with their high temperature are said to be most efficaceous 

in rheumatic and many other diseases. The springs are at all seasons 

above the level of the stream. They already have a wide local reputation and are visited yearly by numbers of invalids with reported satisfactory results.

The Fort Washalcie Hot Spring. This is situated in the valley of 

Little Wind Eiver, its waters reaching the surface through Quaternary 

deposits; but the red sandstones of the Trias appear at short distances 

to the east and west and underlie the river debris at no considerable 

depth. Like the Big Horn Hot Spring this also is found at the axis 

of an anticline, the nature, of which has already been described. The 

crater of the spring is several hundred feet across and of considerable 

depth, constituting an excellent swimming pool. The temperature is 

considerably lower than that of the Big Horn Hot Springs.

The waters of all three of the foregoing springs will doubtless display marked curative properties, but the Big Horn Spring stands 

highest in point of temptrature.

AGRICULTURE.

The agricultural possibilities of the Big Horn and Wind Eiver basins 

are limited to local areas at the foot Of the several mountain ranges, including both bench land and stream bottoms, and to the valleys of the 

larger streams in the central part of the basins, chief among them 

being the Wind Eiver, the Big Horn, Stinking Water, Grey Bull, Wood 

Eiver, and No Wood.

In the Big Horn basin the belt at the base of the mountains has a 

general width of 3 to 5 miles, which with the areas of Montana and Lararnie shales along the stream bottoms from reduplication through 

folding, is very considerably increased. Below the line of the Laramie, 

however, the smaller streams run dry. In this belt, adjacent to the 

mountains, agriculture has already been carried sufficiently far to indicate a general success under similar conditions for much of the periphery of the basin. Grain and grasses, including alfalfa and timothy, grow 

in heavy crops wherever care is used in sowing, cultivation, and irrigation. Vegetables, excepting corn, and berries of all kinds may be raised 

with no more than the ordinary efforts in the productive portions of 

the West. Much of the present productive area is located on the Montana clays, but this is due to position where water is available and 

the valley broad. The uplands are not generally of a topographic form 

to permit cultivation, being too rugged next to the mountains and too 

high and far removed from water in the more interior portions of 

the basins. There are localities, however, on both the east and west
AGRICULTURE. 69

sides of the basin \vhere considerable areas of this nature may be found, 

advantageously situated for crop growing. Of the foothill valleys the 

most highly cultivated and productive at present are those of Wood 

Eiver, Grey Bull, Meeteetse Creek, Owl Creek and No Wood. In the 

central part of the Big Horn basin the Big Horn Eiver, the Stinking 

Water and Grey Bull are the only streams which can be advantageously 

settled, the water of these streams alone being abundant all the year 

for the demands of agriculture. Away from these streams the basin is 

a vast desert, intensely heated in summer, wind-swept in winter, with 

hardly a spear of grass for grazing.

The productive area of that, part of the Wind Eiver basin on the 

route of reconnoissance.is confined to a belt of 5 or 6 miles along the 

base of the Wind Eiver Mountains, and to the Wind Eiver valley, all 

else being even more barren than the center of the Big Horn basin. 

In the part adjacent to the Wind Eiver Eange the possibilities of 

agriculture are unexcelled. The bottoms of Popoagie Creek about 

Lander are uninterrupted in the stretch of hay, grajn and vegetable 

fields, and well indicate what can be attained elsewhere along the range; 

here, again, the cultivated area is on Montana shales. Water in this 

belt is abundant. Along the southern base of the Owl Mountains there 

are only a few small springs, capable of irrigating a minimum acreage 

of land. The Wind Eiver bottoms are capable of irrigation and present 

considerable acreage for agriculture. Nearly all the other portions of 

the basin are covered with the loose sands derived from the Tertiaries 

which there prevail.

East of the Big Horn Mountains and north, in Montana, the capabilities of the soil are well known, and farming is already in an 

advanced stage.

Artesian wells are possible in many parts of the Big Horn and 

Wind Eiver basins.

INDEX,"

A.

Page.

Absaroka Range, general description of... 14 

structure of........;................... 29-32

coal in the Shoshone and............... 54-55

Analyses of coals, table of................. 61-62

Arcbean formations, areas of.............. 17

Aughey, Samuel, cited .................... 63,64

B.

Ben ton formation, described............... 22

Big Horn Basin, agriculture in ............ 68-fi9

divide between the valley of the Yellowstone and the ........................ 15, 46

general description of.................. 16-17

hot springs in.......................... 67

Big Horn Hot Springs, described.......... 67-68

Big Horn Range, general description of ... 14-15 

occurrence of gold in................... 60, 67

structure of............................ 41-45

Bonanza district, oil in..................... 64

Bridger formation, described............... 27

Building stones, varieties of............... 66

C.

Cambrian formation, rocks of.............. 17-18

Carboniferous, areas of .................... 19-20

Coal-measures of....................... 20

Subcarboniferous series................ 20

Coal, areal distribution of.................. 50

chemical analyses of................... 61-62

in the Absaroka and Shoshono Ranges. 54-55 

in the Dakota formation ............... 49

Ejnbar district......................... 59-60

in the Lander field..................... 60

in the Laramie formation .............. 49

in the Muddy Creek field .............. (JO

in the Niobrara formation ............. 49

No "Wood region ....................... 52

Powder River field..................... 50-52

in Red Lodge district.................. 53-54

' in the Sheridan district ................ 52

in Sunshine district.................... 55-59

in Upper "Wind River region ........... 60

Coal-measures, description of.............. 20

Colorado formation, component members of 22-23

D.

Dakota formation, coal reported in.

described ......................

thickness of....................

Dallas oil field, described...........

F.

Page. 

Port AVashakie Hot Springs, described ..... 68

G. 

Gold, in Big Horn Kange. .................. 66-67

H.

Hot Springs, the Big Horn ................. 67-68

the Fort Washakie.. ................... 68

the Stinking "Water. ................... 75

J. 

Jura, description of ........................ 21-22

thickness of. ........................... 21-22

L. 

Lander field, coal iii ........................ 60

Laramie formation, coal in.... ............. 49-62

described .............................. 24

thickness of ............................ 24-25

M.

j Montana, formations embraced by the ..... 22 

Muddy Creek field, con 1 in ................. 60

Niobrara formation, coal in ................ 49

described .............................. 22-23

oil in........................ ........ 63-64,65

No Wood region, coal in ................... 52-53

0.

Oil, Bonanza district. ...................... 64-65

Dallas field............................. 64

geologic horizons of .................... 65

localities visited ....................... 63

"Washakie spring ...................... 63, 64

Owl and Rattlesnake Mountains, general

description of ............................ 15-16

Owl-Rattlesnake Range, structure of ...... 37-41

Osborn, H. "F., and "Wortmau, J. L., cited. . . . 26, 27

Pierre formation described ................ 23-24

Platte River, divide between the drainage 

of the "Wind and.......................... 16

Powder River field, coal in................. 50-52

Pryor Mountains, structure of............. 45-46

Embar district, <;oal in....... '. ............. 59-(iO | Quaternary deposits, areas of.

11
72 INDEX.

R.

Kattlesnake Mountains, general description of Owland.......................... 15-16

"Bed Beds" of the Trias, description of... 21 

oil in ..............................*..... 65

Ked Lodge district, coal in ................ 53-54

Eicketts, Louis D., cited .................:. 63

Sheridan district, coal in ...... -............ 52

Shoshone Range, general description of....' 14

structure of............................ 32-33

coal in the Absaroka and .............. 54-55

Silurian series, areas of exposure .......... 19

basal limestone of....................... 18-19

chert-bearing limestones of ............ 19

quartzites of........................... 19

thickness of............................ 19

varieties of rock exposed .............. 18-19

Subcarboniferous series, description of.... 20

thickness of............................ 20

Stinking "Water Hot Springs, described .... 07

Sunshine district, structure of..... ; ....... 33-37

coal in ................................. 55-59

Page.

Triassic period, " R§d Beds" of............ 21

U. 

Upper Wiud River region, coal in.......... CO

W.

Wasatch series, description of............. 25-27

thickness of ........................... 25

Wind River basin, general description of.. 16,17 

structure of............................ 48-49

hot springs in.......................... 67

agriculture in ......................... 69

Wind River, divide between the drainage of 

the Platte and ........................... 16

Wind River Range, general description of. 14 

structure of............................ 46-48

Wortman, J. L., and Osborn, H. P., cited. 26,27,29

Y.

Yellowstone Valley, divide between the 

Big Horn Basin and the ................. 14-15

Yellowstone River, structure of the divide 

between the Big Horn Basin and the .... 46