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DEPARTMENT OF THE INTERIOR. 

Hubert Work. Secretary 

U. S. GEOLOGICAL SURVEY 

Georlfe Otis Smith. Director 

PROFESSIONAL PAPER 153 

STUDIES OF BASIN-RANGE STRUCTURE 

STATE 

BY 

GROVE KARL GILBERT 

L G EO r-: r:'!, "l t,' l.", 

U 1\1 " ! '-.. :1' ,-; "i c. :'. ~ ~: ~ . ~ I\T B RDcKPQIi • " • I ~ •• \ '_" f' ~ ,.: L 1. ... L ... ~ 

BROC:<PORT, NEW YORK ,/ .' 

--

UNITED STATES 

GOVERNMENT PRINTING OFJ'ICm 

WASHINGTON 

1928 
DEPARTMENT OF THE INTERIOR 

Hubert Work. Secretary 

U. S. GEOLOGICAL SURVEY 

Geor~e Otis Smith. Director 

Professional Paper 153 

' .. ",_ .. 

STUDIES OF BASIN-RANGE STRUCTURE 

BY 

GROVE KARL GILBERT 

UNITED STATES 

GOVERNMENT PRINTING OFFICE 

WASHINGTON 

1928 
ADDITIONAL COPIES 

OF TmS PUBLICATION MAY BE PROCURED FROM 

THE SUPERINTENDENT OF DOCUMENTS 

U .S.GOVERNMENT PRINTING OFFICE 

WASmNGTON, D. C. 

AT I 

60 CENTS PER COpy 
CONTENTS 

PREFACE, by George Otis Smith ____________________ _ 

CHAPTEU I. Introduction ______ - _______ - - - - - - - - - - - - --

CHAPTEU II. Wasatch Range, Utah _________________ _ Generalfeatures ______________________________ _ 

The frontal fault ___________________ - _ - - - - - - - - -- ~omenclature ____________________________ _ 

Lake Bonneville _____________ --- - - - --- - --- --

Products of fault friction ________ - ___ - - - - - - --

General character ______________ - - - - - - - - Localities ____________________________ _ 

Rock Canyon locality _________ - __ - -

Fort Canyon locality ______________ _ 

Draper locality _______________ - ___ _ 

Mill Creek locality ________________ _ 

Beck's Spring locality _______ - - - - __ --

Ogden Reservoir locality _____ - - - _ - -- Jump-off locality ________ ~ _________ _ 

Willard locality ___________________ _ 

North Ogden fire clay _____________ -

Discussion _________________ ~ _________ _ 

Outline of the fault ________________________ _ 

Dip of the fault ___________________________ _ 

Fault-block spurs _________________________ _ 

City Creek spur ______________________ _ 

Pleasant View spur ____________________ _ Traverse spur ________________________ _ 

Honeyville spur _______________________ _ 

Madsenspur _________________________ _ 

Other spurs __________________________ _ 

Summary and conclusions __________________ _ 

Piedmont scarps ______________________________ _ 

Scarps related to piedmont scarps _______________ _ 

The escarpment _______________________________ _ 

Truncation of ribs _________________________ _ 

Truncation of canyons ___ ~ _________________ _ 

Tru ncation of structural features ____________ _ 

Interpretation of truncation ________________ _ 

Comparison of Wasatch escarpment with 

escarpments north of the Grand Canyon_ Volcanic escarpments __________________ _ 

Ice-made escarpments ________________ _ 

Wave-made escarpments _______________ _ 

Wind-made escarpments _______________ _ 

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CHAPTER II. Wasatch Range, Utah-Continued. 

The escarpment-Continued. 

Interpretation of truncation-Continued. 

Stream-made escarpments ______________ _ 

Summary and conclusions ______________ _ Facets ___________________________________ _ 

Old graded slopes _____________________________ _ 

Throw of the frontal fault ______________________ _ 

Cross drainage and back valleys ________________ _ Cross drainage ____________________________ _ Back valleys _____________________________ _ 

HeberValley _________________________ _ 

Rhodes Valley ________________________ _ 

Morgan Valley _______________________ _ 

Parleys Park _________________________ _ 

Ogden Valley and Eden Pass ___________ _ 

Mantua Valley and Dry Lake trough ____ _ 

Discussion of back valleys _____________ _ 

The Wasatch a horst ______________________ _ 

The through canyollS __________ "" ___________ _ 

Discussion of cross drainage _____ _ D __________ _ 

Faults within the range ________________________ _ 

Review of range structure and range history ______ _ 

Review of physiographic characters of marginal faults _____________________________________ _ 

CHAPTER III. Fish Springs and House Ranges, Utah __ _ Generalfeatures ______________________________ _ 

Fish Springs Range ___________________________ _ House Range _________________________________ _ 

CHAPTER IV. Klamath Lake region, Oreg ____________ _ Generalfeatures ______________________________ _ 

Plum Ridge and vicinity _______________________ _ 

Modoc escarpment ________________________ ' ____ _ 

Fort Klamath escarpment _____________________ _ 

The face of the Cascade Range _________________ _ 

Ridges west of upper Klamath Lake _____________ _ Thevalleys _________ ~ ________________________ _ 

The prefaulting topography. ____________________ _ 

CHAPTER V. Fault scarp near Bakersfield, CaliL ______ _ General features _____________________________ _ 

Vertical grooving and joints ____________________ _ 

Character and relations of the Miocene beds ______ _ Summary and conclusions ______________________ _ INDEX ________ £ __________________________________ _ 

III 

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ILLUSTRATIONS 

PSire 

PLATE 1. A, Bonneville shoreline near Logan, Utah; B, Shear zone of west face of Wasatch Range, near Draper, Utah______ 16 

2. A, Shear zone at mouth of Mill Creek Canyon, Wasatch Range, Utah; B, Slickensides at base of Wasatch escarpment near city reservoir, Ogden, Utah __________________________________________________ ----------_____ 16 

3. Mill Creek Canyon, Wasatch Range, Utah: A, Shear zone at mouth of canyon; B, High-dipping Paleozoic strata in 

north wall of canyon ________________________________________________ ' ___________________________ - _ _ 16 

4. Fault phenomena in Mill Creek Canyon, Wasatch Range, Utah: A, Slickensides; B, Shear zone and facets_ 16 

5. Exposure of fault rock north of Salt Lake City, Utah: A, General view; B, Nearer view, showing slickensides__ ____ 16 

6. Fault phenomena near Jump-'off Canyon, Wasatch Range, Utah: A, View from the north; B, View from the south- west ________________________________________ :___________________________________________________ 16 

7. Fault phenomena of Wasatch Range near Willard, Utah: A, A pseudo-anticline in Cambrian quartzite; B, General 

view from the north__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 16 

8. A, Western escarpment of City Creek spur, Wasatch Range, Utah; B, West face of Wasatch Range near Ogden, 

Utah___________________________________________________________________________________________ 16 

9. A, Pleasant View spur and the Wasatch escarpment, Wasatch Range, Utah; B, Mouth of Taylor Canyon, Wasatch Range, Utah _______________________________________________ --____________________________ 24 

10. Lone Peak salient of Wasatch Range, Utah: A, Saddle between the salient and the Traverse spur; B, Ancient channel of CornerCreek_______________________________________________________________________________ 24 

11. Features at the heads of spurs of Wasatch Range, Utah: A, Corner Creek groin; B, Scarp opposite Honeyville spur _ 24 

12. Features of spurs of Wasatch Range, Utah: A, Landslides at Madsen spur; B, Spur of dark gneiss, north of Ogden Canyon __ ~ _____________________________________________________________________________ :_ 24 

13. Piedmont scarps in Wasatch Range, Utah: A, Scarps in moraine; B, Scarp and graben in alluvial apron___ __ _____ _ 32 

14. Piedmont scarps in Wasatch Range, Utah: A, Scarps in alluvium; B, Scarps and graben in moraine_____________ _ 32 

15. Piedmont scarps on Wasatch Range, Utah: A, Scarps north of Ogden Canyon; B, Scarp on Bonneville delta near Weber Canyon__________________________________________________________________________________ 32 

16. Landslides in Berkeley Hills, Calif.: A, Slide on a steep hillside; B, Slide on a moderate slope___________________ 32 

17. A, Landslide near Uintah, Utah; B, Piedmont scarps near city reservoir, Ogden, Utah_________________________ 32 

18. Piedmont scarps about black spur of Wasatch Range, Utah: A, Scarp along south base; B, Scarp along north base_ 32 

19. Facets of the Wasatch escarpment, Wasatch Range, Utah: A, West side of Lone Peak salient; B, View south of 

Provo__________________________________________________________________________________________ 40 

20. Facets of the Wasatch escarpment north of Provo, Utah: A, General view from Provo; B, Details at Rock Canyon_ 40 

21. Facets of the Timpanogos front, Wasatch Range, Utah: A, Near Battle Creek; B, Near American Fork_______ 40 

22. A, Wasatch escarpment opposite Willard, Utah; B, Bonneville shore line near Tooele, Utah________________ 40 

23. Faceted escarpments made by stream erosion: A, Escarpment on South Fork of Ogden River, Utah; B, Escarpment on Kern River, CaliL_______________________________________________________________________ 40 

24. Views in Wasatch Range, Utah: A , Wasatch escarpment opposite Pleasant View spur; B, High-level grade plains_ _ 40 

25. Views in Wasatch Range, Utah: A, The range seen from the west near Kaysville; B, Mouth of Weber Canyon__ 56 

26. Back valleys of the Wasatch Range, Utah: A, Margin of Heber Valley, near Charleston; B, South end of 

Morgan Valley___________________________________________________________________________________ 56 

27. Provo Canyon, Utah: A, The canyon near its head; B, An opening above the canyon______________________ 56 

28. East face of Wasatch Range, Utah, near Eden Pass____________________________________________________ 56 

29. Map of Dry Lake trough and part of Mantua Valley, Utah______________________________________________ 64 

30. Views in Wasatch Range,. Utah: A, North wall of Provo Canyon; B, View eastward in Eden Pass____________ 64 

31. Topographic map of Fish Springs and House Ranges, Utah______________________________________________ 72 

32. Views in Fish Springs Range, Uiah: A, West front of the range, north of Fish Springs mines; B, Fault cliff and 

shear zone on west front of the range, 5 miles south of Fish Springs mines __________________________ ,_ _ _ _ 72 

33. A, West front of House Range, Utah, from a summit at the south; B, 0, Slickensides associated with fault scarps in Plum Ridge, near Algoma, Oreg_ _ ________ _ ___________________________ ________ _ _ _ _ _ _ __ ______ _ ___ _ 72 

34. Map of region about Upper Klamath Lake, Oreg_______________________________________________________ 80 

35. Slickensided faces on footwall of Plum Ridge fault, 1 mile south of Algoma, Oreg _______________ ,___________ 80 

36. Modoc fault scarp________________________________________ __________________________________________ 80 

37. Topographic details near Upper Klamath Lake, Oreg.: A, Lenticular buttress on Modoc fault scarp, a little 

south of Modoc Point; B, Hills south of lake, from the east___________________________________________ 80 

38. Fault scarp at mouth of lower canyon of Kern River, CaliL_____________________________________________ 80 

39. Details of fault scarp at mouth of canyon of Kern River, Calif: A, Footwall of fault about 1,000 feet north of the 

river; B, View southeastward across the mouth of the canyon_________________________________________ 80 

40. Details of fault scarp at mouth of canyon of Kern River, Calif.: A, Slump terrace under scarp; B, 'Unslumped scarp. ___________________________________________________________ .______________________________ 80 

IV 
CONTENTS V 

Pal. 

FIGURE 1. Diagram of generalized mountain sections, discounting denudation __________ ~____________________________ 1 

2. Types of surface cracks associated with the horizontal fault slip which caused the California earthquake of April 18, 1906 _________ ---_ _ _ ______ _ ____ _ ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _______ _ _ _ _ ___ _ _ _ _ _ _ _ _ __ _ 13 

3. Ideal sections of faults and of subsidiary slickened partings _____ ' __________________________ ~_____________ 13 

4. Generalized profile section of the lower part of the Wasatch front near Provo, Utah________________________ 14 

5. Section exposed at the mouth of Rock Canyon, Wasatch Range, Utah____________________________________ 14 

6. Diagrammatic profile section of rock surface near Ogden Reservoir, Utah_________________________________ 16 

7. Ground plan of faults near Ogden Reservoir, Utah_____________________________________________________ 16 

8. Diagram of elements of the cross fault near Ogden Reservoir, ptah ____________________ -_________________ 17 

9. Section of west front of Wasatch Range north of Jump-of! Canyon, Utah_________________________________ 18 

10. Profile section of pseudo-anticline near Willard, Utah__ _ _____ _ _____ _ _____ __ ____ ______ ______ _____ _ ____ __ 18 

11. Diagram to explain Plate 7, B_____________________________________________________ _________________ 19 

12. Map of frontal fault of Wasatch Range, Utah_________________________________________________________ 20 

13. Map of that portion of the frontal fault of the Wasatch Range north of Weber Canyon, Utah_______________ 20 

14. Ground plan of Wasatch frontal fault at Taylor Canyon, Utah__________________________________________ 21 

15. Diagrammatic section of City Creek spur of Wasatch Range, Utah______________________________________ 23 

16. Graded ridges near City Creek spur, Wasatch Range, Utah_____________________________________________ 24 

17. Dissected terrace along Red Butte Canyon, Wasatch Range, Utah ______________________________________ 24 

18. Map of Pleasant View spur, Wasatch Range, Utah_____________________________________________________ 25' 

19. Section of Pleasant View spur and part of Wasatch Range, Utah________________________________________ 25 

20. Profiles of base of Wasatch Range, Utah, at points, ~etween canyon mouths_______________________________ 26 

21. Sketch map of Traverse spur and adjoining part of Wasatch Range, Utah________________________________ 27 

22. Sketch of Lone Peak salient of Wasatch Range, Utah, from the west, showing spiral furrows________________ 28 

23. Diagram of southern face of Lone Peak salient of Wasatch Range, Utah _________________________________ 28 

24. East-west section of Madsen spur of Wasatch Range, Utah_____________________________________________ 30 

25. Diagrammatic north-south profile of Madsen spur of Wasatch Range, Utah_______________________________ 31 

26. Ground plan of block spur north of mouth of Ogden Canyon, Wasatch Range, Utah_______________________ 31 

27. Ideal section of progressive dislocation o~ valley block and range block, to illustrate hypothetic derivation of 

spurblock______________________________________________________________________________________ 32 

28. Profile of piedmOint scarp, illustrating measurement of throw ___________ ,_________________________________ 34 

29. Sketch map of Corner Creek groin, Wasatch Range, Utah __________________________________ ,____________ 35 

30. Diagrams to illustrate the simpler types of piedmont scarps_____________________________________________ 37 

31. Profile of piedmont scarps on a delta of the Provo stage of Lake Bonneville at the mouth of Rock Canyon, near the city of Provo, Utah ____________________________ -:-______________________________________________ 38 

32. Profile of piedmont scarps near Ogden Canyon, Utah___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 38 

33. Map of Bonneville shore escarpment and shore terraces near Dove Creek, Utah ______________ .' _ _ _ _ _ _ _ _ _ _ _ _ 44 

34. Outlines of mountain escarpments where joined by rock-cut piedmont plains, Silver Creek quadrangle. N. Mex_ 46 

35. Outline of the Little Burro Mountains, N. Mex., showing the boundary between the bedrock of the range and 

the surrounding alluvial apron_ _ _ _ _ __ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ ___ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___ _ __ _ _ _ _ _ 46 

36. View of west face of Wasatch Range, Utah, north of City Creek spur, illustrating the evenly graded crests of 

interfiuveridges_________________________________________________________________________________ 49 

37. Diagrammatic profile of west face of Wasatch Range, Utah, between City Creek spur and Weber Canyon_ _ _ _ 50 

38. Profile of Wasatch Range and Jordan Valley, Utah, illustrating data on throw of Wasatch frontal fault_______ 51 

39. Stereogram of a portion of the central Wasatch Mountains, Utah _______________________________________ '_ 54 

40. Diagram of two members of Wasatch Range, Utah, opposite Ogden Valley________________________________ 58 

41. Diagrammatic profiles of Wasatch Range at Eden Pass, Utah___________________________________________ 58 

42. Diagram to illustrate directions of drainage lines at Eden Pass, Utah __________ ..:__________________________ 58 

43. Plan of drainage across Wasatch Range, Utah, at and near Box Elder Canyon____________________________ 63 

44. Profile elevation of a portion of the Wasatch Range near Utah Lake, Utah, showing the main crest and a shoulder or terrace of the western face _______ ".._ _ _ _ _ __ _ _ _ __ _ _ _ _ _ __ _ _ _ __ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 65 

45. The broad structural features of the Fish Springs and House Ranges, Utah_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 70 

46. Fault system of the eastern base of the Fish Springs Range, Utah _____________________ .:.__________________ 71 

47. Diagram illustrating truncation of structure in the Fish Springs Range, Utah______________________________ 72 

48. Diagrammatic profile and section across the Plum Ridge fault scarp, Klamath County, Oreg________________ 76 

49. Longitudinal profile of northern part of Plum Ridge, Klamath County, Oreg______________________________ 77 

50. Cross profiles of northern part of Plum Ridge and of associated ridges and valleys, Klamath County, Oreg__ _ _ 79 

51. Fault splinter on Modoc scarp, near Naylox, Oreg _________________________________________ .:.___________ 80 

52. Thinner fault splinters of Modoc scarp, near Naylox, Oreg______________________________________________ 81 

53. North end of Long Lake Valley, Klamath County, Oreg________________________________________________ 83 

54. Map of Swan Lake Valley and vicinity, Oreg ________________________________ ..:_________________________ 84 

55. Ideal segment of the granite body near mouth of Kern River Canyon, CaliL______________________________ 86 

56. Ideal sketch to show the relation of an observed outcrop of limestone on a hill of Miocene beds to the granite face 

against which the hill rests, Sierra Nevada, CaliL _ _ __________________ _ _ __ _ __ _ _ _ _ _ ______ __ _ _ _ _ __ _ _ _ __ 88 

57. Profile of fault scarp at principal exposure of footwall north of Kern River, CaliL _____________ -:___________ 88 
- ... 

\ 
PREFACE 

By GEORGE OTIS SMITH 

In the death of Grove Karl Gilbert on May 1, 1918, 

American geology lost one of its greatest investigators. 

Although gradually failing in physical strength, he 

maintained during his last years the same clearness of 

conception, the same power of analysis, and the same 

lucidity of expression that had been characteristic of 

all his previous work. He so wisely conserved bis 

failing health and so regulated his working hours that 

the quality of his product was not impaired. 

The present paper represents the partial fruition of 

a broad plan to reexamine critically the subject of 

Basin-Range structure. The chapter on the Wasatch 

Range is complete. That on the Fish Springs and 

House' Ranges is nearly complete. It was Mr. Gilbert's purpose, I believe, to review and condense the 

chapter on the Kern River fault and perhaps also 

that on the Klamath region. This ho was not able 

to do, anod the manuscript is published essentially as 

he left it. 

Geologists and physiographers the world over, I am 

sure, will welcome Mr. Gilbert's mature judgment as 

set forth in these pages on the validity of a concept 

which, as a young man, he first gave to the scientific 

world in 1874. His last paper is thus an amplification 

and clarification of one which he wrote more than 

half a century ago. The cycle is now complete. 

VII 
STUDIES OF BASIN -RANGE STRUCTURE 

By G. K. GILBERT 

CHAPTER I. INTRODUCTION 

Between the Wasatch Mountains and the Sierra' 

Nevada lies a region traversed by numerous minor 

mountain ranges. Alternately with the ranges stretch 

valleys floored by detritus, and the whole system 

exhibits a rough parallelism. It was early recognized 

that these mountains are of a peculiar type. Because 

the district of interior drainage to which Fremont 

gave the name Great Basin is also bounded on the 

east and west, approximately, by the Wasatch and 

the Sierra, the system of peculiar, ranges was called 

the Great Basin system, or the Basin Ranges. It was 

well known, however, that the boundaries of the orographic province are quite distinct from those of the 

drainage district. Davis has introduced "fault block" 

as a descriptive term applicable to the typ.e of structure, and "fault-block structure" has partly supplanted "Basin Range structure" in the literature. 

If with the advance of knowledge geologists shall 

conclude that the fault-block structure is not the dominant structure of the Basin Ranges, the term Basin 

Range structure can no longer be used in its original 

sense and may properly be abandoned. 

Volcanic mountains differ from all others in that 

they are built by the addition of material to the 

earth's surface. Leaving them out of account, we 

may classify mountains broadly as diastrophic and 

residual. A coordinate classification of valleys distinguishes the diastrophic from the erosional. A simple conception of a system of diastrophic ridges and 

valleys is that of parallel folds created by tangential 

compression of the crust. A contrasted conception 

is that of a plateau dissected by parallel streams, 

where the resulting .valleys are erosional and the 

resulting ridges residual. Such, simple systems pf 

corrugation are, however, ideal rather than actual. 

Folding is but one of several diastrophic processes 

capable of producing mountain ridges and valley 

troughs, and whatever the process of production the 

forms are modified by erosion" or by erosion and deposition, during their development. The hypogene 

forces that make mountains and the' epigene forces 

that make plains work coincidently and in antagonism, 

and mountains result only when diastrophism is more 

active than gradation. If diastrophism is feeble its 

product may never achieve a rank above that of hills. 

As strong diastrophism wanes and eventually ceases, 

the epigene forces resume dominance, continuing the 

work of sculpture which they began on the inception 

of the deformation and finally reducing ridges and 

troughs to a common plain. 

In the creation of the Appalachian Mountains folding was a leading factor. Stratified rocks were 

pushed in to parallel folds, some of the folds were 

overturned, and thrust faults were developed. The 

sculpture that accompanied and followed the deformation was largely a work of selective erosion, valleys 

being opened in weak rocks and ridges being developed 

from resistan t rocks. The ridges as we know them are 

related to the folds but are not upfolded crests, and 

the valleys are related to the folds but are not downfolded troughs. The valleys are erosional and the 

ridges residual. The system of valleys and ridges, the 

visible corrugation of the district, has been carved 

from a complex rock body which owes its structure 

to tangential compression. A characterisitc fea.turea feature observable wherever the rocks are sedimenFIGURE I.-Diagram of generalized mountain sections, discounting denudation 

tary and have escaped metamorphism-is that each 

ridge and valley ~rends with the strike of the strata. 

It was through comparison with Appalachian characters that the characters of the Basin Ranges were 

first recognized and described. 

In outlining the development of knowledge and 

opinion as to Basin Range structure I find it impossible 

to avoid the apparent egotism of beginning with my 

own work. In the summers of 1871 and 1872 I 

accompanied topographic parties of the Wheeler 

Survey, passing rapidly through parts of Utah, Nevada, 

California, Arizona; and New Mexico and gleaning 

geologic data by the way. A preliminary report was 

published in 1874 and a fuller report in 1875. The 

following passages, the first quoted from the preliminary report and the second from the fin aI, summarize 

my impressions and generalizations as to the Basin 

Ranges: 

The sections accumulated by our geological observers admit 

of the following classifications (see fig. 1): 

1. Faulted monoclinals occur, in which the strata on one side 

of the fault have been lifted, while those on the opposite side 

either do not appear (a) or (less frequently) have been elevated 

1 
2 STUDIES OF BASIN-RANGE STRUCTURE 

a less amount (b). Two-thirds of the mountain ridges can be 

referred to this class. 

2. Other ridges are uplifts limited by parallel faults (c), and 

to these may be assigned a few instances of isolated synclinals 

(d), occurring under circumstances that preclude the idea that 

they are remnants omitted by denudations. 

3. True anticlinals (e) are very rare except as local, subsidiary features, but many ranges are built of faulted and dislocated rock masses (f)" with an imperfect anticlinal arrangement. 

Not only is it impossible to formulate these features by the 

aid of any hypothetical denudation in such a system of undulations and refoldings as the Messrs. Rogers have so thoroughly 

demonstrated in Pennsylvania and Virginia, but the structure 

of the western Cordillera system stands in strong contrast to 

that of the Appalachians. In the latter, corrugation has been 

produced commonly by folding, exceptionally by faulting; in 

the former, commonly by faulting, exceptionally by flexure. 1 

To begin with the simplest generalization, the ranges are a 

system not indeed formed at the same time but exhibiting 

certain common characters over a great area~ They are parallel; 

they recur with some regularity of interval; they are of moderate 

dimensions. 

Second. The ridges of the syst~m occupy loci of upheaval and 

are not mere residues of denudation; the valleys of the system 

are not valleys of erosion but mere intervals between lines of 

maximum uplift. Within the ranges there are indeed eroded 

valleys, and the details of relief show the inequality of erosion 

due to unequal resistance, but there is not on a grand scale that 

close dependence of form or durability that must maintain were 

the great features of the country carved by denuding agents. 

Third. The movements of the strata by which ridges have 

been produced have been in chief part vertical along planes of 

fracture and have not involved great horizontal compression. 

There are some notable local exceptions to this, but considering 

the prevalence of faulted monoclinals, which demand no horizontal motion, the existence of the feature as a distinctive one 

need not be questioned. 

Fourth. We may say, without fairly entering the field of 

speculation, that the forces which have been concerned in the 

upheaval of the Basin Ranges have been uniform in kind over 

large areas; that whatever may have been their ultimate sources 

and directions, they have manifested themselves at the surface 

as simple agents of uplift, acting in vertical or nearly vert.ical 

planes; and that their loci are below the immediate surface of 

the earth's crust.2 

I,n a classification of mountain forms and structure, 

published in 1877, Powell characterized the Basin 

Ranges in essentially the same manner, in a statement 

, based in part on his own observations. 

The field work of the Geological Exploration of the 

Fortieth Parallel was executed in 1867 to 1873 and 

covered a belt of country 100 miles wide, from the 

eastern base of the Rocky Mountains to the eastern 

base of the Sierra Nevada. Its first publication on 

the geology of the Basin Ranges appeared in 1870 

and contained descriptions of individual ranges by 

King, Hague, and Emmons. The descriptive work 

was completed in a volume by Hague and Emmons 

which was issued in 1877, and the broader generaliza1 Gilbert, G. K., U. S. Geog. and Geol. Surveys W. 100th Mer. Progress Rept., 

1872, p. 50, 1874. 

I Gilbert, G. K., Report on the geology of portions of Nevada, Utah, California, 

and Arizona, examined in the years 1871 and 1872: U. S. Geog. and Geol. Surveys 

W.l00th Mer. Rept., vol. 3, p. 41,1876. 

tions were published the following year by King, from 

whom I quote: 

These remarkable quasi-parallel mountain bodies separated 

from each other by depressed valleys, which are occupied by 

fresh-water Tertiary and Quaternary beds, are a series of mountain islands lifted above desert plains. They have given rise to 

considerable discussion, and there is already some difference of 

opinion between Powell and Gilbert on the one hand and myself 

on the other. In volume 3, of this series, in a brief sketch of 

the Green River Basin, I alluded to the Basin Ranges as a series 

of folds. Powell and Gilbert have called attention to the 

abundant evidence of local vertical faults and the resultant 

dislocation into blocks. One of the most common features of 

the Basin Ranges is a mountain body composed of a steeply or 

gently dipping monoclinal mass, edged on both sides by the 

horizontal desert formations, the back of the monoclinal mass 

consisting of inclined planes of strata, while the other face of 

the mountain body consists of an abrupt cliff, evidently t.he 

result of a vertical fault, which has been more or less modified 

by a comparatively recent erosion. The frequency of these 

monoclinal detached blocks gives abundant warrant for the 

assertions of Powell and Gilbert that the region is one prominently characterized by vertical action; yet when we come to 

examine with greater det3il the structure of the individual 

mountain ranges it is seen that this vertical dislocation took 

place after the whole area was compressed into a great region of 

anticlinals with intermediate synclinals. In other words, it was 

a region of enormous and complicated folds, riven in later time 

by a vast series of vertical displacements, which have partly 

cleft the anticlinals down through their geological axes and 

partly cut the old folds diagonally or perpendicularly to their 

axes.s 

King then describes the relations which the axes of 

folds within the several ranges bear to the trends of 

the ranges and proceeds to the following generalization: 

While this brief description, from the complicated nature of 

the facts, may fail to convey a full idea of the state of things 

on the Basin Ranges, yet a careful scrutiny of the axis lines, as 

laid down upon analytical maps X, XI, and XII, will show 

(a) that the region is one displaying a continuous series of folds 

of Paleozoic and Mesozoic rocks; (b) that the general trends of 

these axes approach more nearly a meridian than an east and 

west line; (c) that the axes themselves often display broad 

general curves traced through a hundred miles, their grander 

convexities being turned to the west; (d) that in detail the axes 

are further subject to minor sinuosities obviously due to longitudinal compression; and (e) that the whole region had been 

most irregularly invaded by a series of faults which are east 

and west, north and south, northeast-southwest, and northwestsoutheast. The result of this complicated interlacing system of 

dislocation is that all the ranges of the Great Basin are broken 

into irregular blocks, sections of which have sunk many thousand feet below the level of the adjoining members. It frequently happens that anticlinal or synclinal axes have been the 

loci of the fissure planes and t.hat in the accompanying dislocations halves of folds are left in long, well-defined monoclinal 

ridges. When a fold is cut, either diagonally or transversely, 

by a fault, there is not infrequently a considerable horizontal 

displacement, as may be seen in the case of the West Humboldt, 

where the anticlinal axis is displaced 5 miles horizontally, and 

in the case of Pinon Range, wh~re there is a still greater lateral 

movement. 

That these faults were not contemporaneous with the great 

folding period is obvious from their relations to the axis. 

I King, Clarence, U. S. Geol. Expl. 40th Par. Rept., vol. 1, p. 735,1878. 
INTRODUCTION 3 

Pat'aIlel faults often cut blocks which could never have been 

formed if the faults were contemporaneous with the folding. 

When we remember that the Eocene and Miocene Tertiary 

rocks which have been laid down within the hollows of these 

post-Jurassic folds have themselves been thrown into waves 

and inclined positions up to 40° and that these Tertiary beds 

are often violently faulted, it is evident that in extremely" 

modern geological history there has been sufficient dynamic 

action to account for the system of faults.· 

The recognition of two principal epochs of disturbance helped greatly to clarify conceptions of range 

structure and constituted a valuable contribution to 

this subject. 

The next contribution was by Dutton, whose 

II Geology of the High Plateaus of Utah" appeared in 

1880. In order to characterize vividly the structure 

of the Plateau province, to which his field belonged, 

he contrasted it with the structures of two adjoining 

mountain systems, the Park province of Colorado and 

the Basin Range province on the west. I quote two 

passages: 

Yet in some portions of this great expanse of territory there 

are important flexings and warpings of the strata.' This is 

particularly true of the Basin Ranges. But a very significant 

distinction is necessary here. These flexures are not, so far 

as can be discerned, associated with the building of the existing 

mountains in such a manner as to justify the inference that the 

flexing and the rearing of the ranges are correlatively associated. 

On the contrary, the flexures are in the main older than the 

mountains, and the mountains were blocked out by faults 

from a platform which had been plicated long before, and after 

the inequalities due to such preexisting flexures had been nearly 

obliterated by erosion. It may well be that this anterior curvation of the strata has been augmented and complicated by 

the later orographic movements. But it is not impossible to 

disentangle the distortions which antedate the uplifting from 

the bending and warping of the strata which accompanied it, 

and it is only the latter that we can properly associate and correlate with the structures of the present ranges. These present 

no analogy to what is usually understood by plication. The 

amount of bending caused by uplifting of ranges is just enough 

to give t.he range its general profile, and seldom anything more. 

The same fact is presented in the noble ranges of Colorado. 

Along their flanks the sedimentary strata roll up, usually with 

a single sweep, and high on the slopes are cut off by erosion. 

The typical anticlinal axis is not a characteristic feature of the 

Rocky Mountain system. 

The type section of the Park Mountains of Colorado, as 

given by the late A. R. Marvine, shows a series of broad platforms, uplifted with a single monoclinal flexure or fault on 

either side. The width of these platforms varies from 20 to 

45 miles, and from these masses the individual mountain piles 

have been carved by erosion. The restored profiles obtained 

by replacing the material removed by erosion are not indeed 

horizontal nor straight lines but ordinarily convex upward, 

with slight curvature, becoming abrupt or even passing into a 

great fault at the margin of the uplift. Inasmuch as almost 

any configuration of the strata which is convex upward, be it 

ever so little, is called an anticlinal, these platforms would 

probably be so characterized by most geologists. But what a 

contrast to the short, sharp waves of the Appalachians! If 

we analyze the form carefully, it will become apparent that we 

have to do with a structure which has nothing in common with 

• Idem, pp. 742-743. 

a true anticlinal except this slight convexity and which possesses 

characters which the true anticlinal does not.6 

The Basin Ranges are many in number and inferior in magnitude to those of Colorado, though of no mean dimensions. 

They are strongly individualized, each being separated from its 

neighbors by broad expanses of plains as lifeless and expressionless as Sahara. It is as difficult to find a type form representing the construction of these ranges as for those of Colorado. 

Yet there are common features of almost universal preyalence 

among them and at the same time thoroughly distinctive of the 

group. There is on one side of the range sometimes a single 

great fault or more frequently a repetition of faults throwing 

in the same direction while upon the other side the strata slope 

down to the neighboring plains and there smooth out again. 

There is much variety in the details of the dislocations, and so 

complicated do they become in certain localities that they 

sometimes mask the general plan until we carefully unravel 

it. The strata also are almost invariably tilted to high degrees 

of inclination, thus contrasting strongly with the low and 

almost insensible slopes of the plateaus. Hence on one side of 

the range the slope of the profile is along the dip of the strata; 

on the other side it is across their upturned edges.6 

The idea that the Great Basin district, corrugated 

by folding at the end of the Jurass,ic period, had been 

reduced by erosion to a condition of low relief aids the 

conception that the mountains of to-day were created 

by the later and disruptive deformation. It is distinctly Dutton's addition, although King had paved 

the way for it by pointing out that the district had furnished a great body of sediment to Cretaceous seas 

farther east. 

A study of Quaternary lakes in northern Nevada 

and adjacent parts of Utah, Oregon, and California, 

which was carried on by Russell in the years from 1880 

to 1885, gave him large opportunity for observation 

of the external features of Basin Ranges, and his 

reports contain much new orographic material. His 

characterization of the general structure follows the 

lines of his predecessors and serves only to show that 

his observations supported no dissent, but his generalizations amplify the subject by recognizing what may 

be called a subtype of Basin Range structure. In the 

great lava field of the Columbia-Snake Basin the lava 

is largely disposed in horizontal beds, so that the body 

of effusive material has a stratified structure and its 

upper surface constitutes a plain. In a district 

bordering the plain Russell found a system of mountain ridges composed of the same material but with 

the beds inclined, 'and these ridges he described as 

portions of the 'original plain which had been dislocated by faulting and tilting. There was no evidence of folding, and he therefore inferred that the 

lavas had been erupted after the post-Jurassic period 

of folding described by King and before the Tertiary 

and post-Tertiary period of deformation by fracture. 7 

a Dutton, C. E., Geology of the High Plateaus of Utah, pp. 47-48, U. S. Geog. and 

Geol. Survey Rocky Mtn. Region, 1880. 

eIdem, p. 51. 

1 Russell, I. C., A geological reconnaissance in southern Oregon: U. S. Geol. 

Survey Fourth Ann. Rept., p. 443 (especially), 1884. 
4 STUDIES OF BASIN-RANGE STRUCTURE 

It is a remarkable fact that during this development of a theory as to the essential structure of the 

ranges the observers who reported the existence of 

faults gave no adequate statement of the evidence on 

which their determinations were based. In a local 

description I said: 

Worthington Mountain * * * is remarkably acute in 

its cross section. The strata are nearly horizontal but incline 

slightly to the east and pass completely through so as to appear 

on both sides. * * * At the southern end the limestones 

of its section are uncovered and spring abruptly from the talus 

of gravel. I can conceive of no erosion that should have left 

this thin segment as the remnant of an inclined table or of a 

fold. Its narrowness, its straightness, and its isolation mark 

it as a mass of strata thrust upward between two faults-strata 

of which the companion parts lie beneath the debris at its foot.s 

. Emmons, in his description of the Wasatch Range, 

says: "Nor could one imagine an erosion which woUld 

leave an abrupt wall of 7,500 feet in height on one 

side of a valley nearly 20 niiles wide." \I In 1890 I had 

occasion to consider the relation of the Quaternary 

Lake Bonneville to diastrophism and wrote: 10 

In the district of the Great Basin the characteristic structure 

of mountain ranges is one in which faults play an important 

part. Foldings of 'strata are not wanting, buif' the greater 

features of relief appear to have been wrought by the displacement of orographic blocks along lines of fault. Sometimes a 

mountain range consists of a great block of strata cut off along 

one side by a profound fault and inclined in the opposite direction until it descends beneath the plain constituted by the 

alluvial deposits of the adjacent valley. More frequently there 

are other faults within the range, trending parallel to its length 

and having throws on the same side with the throw of the 

greater fault at the base. 

It was probably these internal faults which originally suggested the structure of the ranges as faulted orographic blocks; 

but the structure was soon connected with a certain set of 

topographic features and came to be recognized by means of 

these. A range consisting of a faulted block generally has a 

bold front on the side of the fault and is less abrupt on the 

opposite slope. On the side of the bold front the line separating 

the rock of the mountain from the alluvium of the valley is 

simple and direct, while on the opposite side it is tortuous. 

On the side of the fault the strata usually dip away from the 

adjacent valley; on the opposite side, toward it. It was not 

until after the structure had been discovered and described by 

several geologists that the more decisive evidence afforded by 

the fault scarp was brought to bear. Th~ writer first became 

aware in the summer of 1876 that lines of faulting may sometimes be traced upon the ground by means of low cliffs or 

scarps due to displacement of so recent date that the atmospheric processes of sculpture have not yet restored the ordinary 

forms of topographic detail. Since that time he had observed 

many such scarps in various parts of the Bonneville Basin and 

in other portions of the Great Basin, and the observation has 

been still further extended by others, especially by Russell. 

The observed fault scarps for the most part follow the outcrops of fault planes whose position had previously been inferred 

from the configuration of the adjacent mountains, but they 

have served also to betray a number of faults whose existence 

. might otherwise not be suspected. 

These meager and ~ part belated statements contain the only indications of the grounds of our faith, 

I Gilbert, G. K., U. S. Geog. and Geol. Surveys W.l00th Mer. Rept., vol. 3, p. 

37,1875. 

I Emmons, S. F., U. S. Geol. Expl. 40th Par. Rept., Vol. 2, P. 345,1877. 

10 GUbert, G. K., Lake BonneVille: U. S. Geol. Survey Mon. I, pp. 34~341,1890. 

and this despite the fact that the recognition of faults 

by means of physiographic characters was practically 

novel. Their failure to satisfy the real needs of the 

subject was shown by the discussion which arose a 

decade later. 

In 1900 Spurr made a geologic reconnaissance in the 

Great Basin, crossing it in an east.-west direction on 

three different lines, and the following year he published a discussion of Basin Range structure. His' 

paper treats of the structure of individual ranges as 

observed by himself and others, gives a history of 

deformation in the province, considers the relative 

ascendancy of erosion and deformation and the relative ascendancy of erosion and faulting, gives a history of the development of the fault theory as applied 

to the ranges, and closes with the following analysis 

and summary: 11 

The present writer, seeking the foundation of facts on which 

rests the fault theory of the origin of the Basin Ranges, has 

been obliged to fall back almost wholly on the original work of 

Mr. Gilbert, who appears to have conceived the hypothesis. 

The views of subsequent investigators seem to have been based 

chiefly on the a priori assumption that all the scarps of the 

region were necessarily fault scarps, and much of the literature 

has been prepared with little or no personal acquaintance with 

the field. 

Analyzing Mr. Gilbert's reasons for the propounding of the 

hypothesis, moreover, we find them almost wholly physiographic. The frequently abrupt ascent of the mountains from 

the level desert and the proximity of the great fault scarps of 

the Colorado Plateau seem to have suggested the idea. They 

may be epitomized as follows: . 

(1) The ranges are principally monoclinal blocks. (2) These 

blocks are limited on one or both sides by scarps. (3) These 

blocks and scarps can not have been formed by erosion and 

must therefore be fault scarps. 

On this foundation there rests a great superstructure of theory 

and. deduction. 

The refutation of these points may be summarized from the 

foregoing pages: 

1. According to the accumulated record of observation, 

ranges consisting essentially of a single monoclinal ridge are 

exceedingly rare. The writer does not remember a single 

instance where such a structure was persistent when followed 

sufficiently far along the strike. The apparent monocline 

almost invariably merges into a synclinal or anticlinal fold, of 

which it constitutes one of the limbs. 

2. The writer has undertaken to show that the mountain 

fronts studied are; in general, not marked by great faults, and, 

conversely, that the ascertainable faults are very rarely attended 

by simple fault scarps. 

3. In regard to the impossibility of erosion producing the 

desert ranges as we have them, especially the monoclinal ridges, 

the writer finds chiefly the most normal type of erosiori in the 

Great Basin. In this poiI.lt, however, he is glad to call the 

opinion of Mr. Clarence King to his aid, who has shown th~t in 

the Fortieth Parallel region the monoclinal ridges are in most 

cases parts of anticlinal or synclinal folds and can be traced 

into them longitudinally,12 

11 Spurr, J. E.; Origin and structure of the Basin Ranges: Geol. Soc. America 

Bull., vol. 12, PP. 264-266, 1901. 

12 Spurr here gives reference to "Geological Exploration of the Fortieth Parallel, 

vol. 1, p. 737," but I fail to discover on that page any allusion to erosion. On the 

contrary, King describes certain portiOns of the Gosiute and Peoquop Ranges as 

monoclinaI and Interprets them as the western hal ves of anticlinaIs, the entire eastern 

halves "having been dislocated downward out of sight."-G. K. G. 
INTRODUCTION 5 

The conclusion is that the topographic forms of the Great 

Basin, as we see them, are the net results of compound erosion 

active since Jurassic times, operating on rocks upheaved by 

compound earth movements which have been probably also 

continuous during the same period. Only the more recent 

faults or folds find direct expression in the topography, as in 

most others deformation lags behind erosion. This is true 

chiefly of the local movements, which produce faulting and folding, and not of vast general upheavals and depressions, which 

seem relatively rapid. But folding and especially faulting are 

of irregular speed, while erosion is more uniform, so that local 

deformation may outstrip erosion for a time but in any long 

period is likely to be beaten itself. Thus of the faults in the 

Great Basin, among them even some post-Pliocene faults, 

nearly all have no direct expression in the topography. Nevertheless, some Pleistocene faults are expressed in the topography, 

and these have sometimes a very great displacement, as in the 

Colorado Plateau. 

In the case of the Grapevine Mountains the range appears 

to have been already in existence in pre-Eocene or Cretaceous 

times. In some of the mountains of erosion which have not 

suffered comparatively recent deformation, as has the range 

just mentioned, their ancient origin is still more clear, for the 

Tertiary beds rest against their bases unconformably, generally 

occupying only the present valleys and not being found in the 

mountains. Therefore the main system of ranges was probably 

laid out in pre-Tertiary times. It was at the close of the Jurassic, so far as we can judge from the rather scant evidence, that 

the Great Basin region was uplifted above the sea and plicated. 

During the Cretaceous the region was probably a land mass, 

and this was very likely the period when many of the ranges 

were differentiated. Their regularity is no more than one 

would expect in view of their resulting from parallel folds and 

is not so striking as in the Appalachian region. To explain this 

early dissection we must assume a greater precipitation than 

now and must conclude that the country was traversed by many 

rivers. Subsequently the climate became arid and the water 

supply was not sufficient to remove the detritus from the valleys, 

which filled up, so that for a long period the reverse of differentiation, or leveling, has been going on. Nevertheless the 

Tertiary rocks show that warping, folding, and faulting went 

on continuously all through the Tertiary into the Pleistocene 

and is even now progressing. To this warping, doubtless, 

the Tertiary lake basins were due. 

According to this conclusion these mountains are not simple 

in origin and structure. However, the writer would compare 

the typical Basin Range to the less compressed portions of the 

Appalachians and the Alps. Among the exceptional types of 

ranges the Funeral Range type is conspicuous. This has a 

structure similar to that of a portion of the Jura Mountains, 

as described and fig~red by Professor. Davis.1S 

It is not easy to summarize the considerations 

which cause Spurr to infer erosion where others have 

inferred dislocation, but they are in part illustrat~d 

by the following passage: 

The Ombe Mountains are situated at the extreme western 

edge of Utah, near the Nevada line. According to Mr. King,H 

the structure in the southern portion is an anticlinal fold, which 

has a northeast-southwest strike and thus diverges from the 

general north and south trend of the range. Northward this 

fold is succeeded, on account of this divergence, by the adjacent synclinal. Still farther northward the entire range has 

a uniform westerly dip, apparently representing one side of the 

next anticlinal fold, the other side having been removed by erosion. The east face of this portion of the mountains is a steep 

18 Davis, W. M., Physical ieography, p. 168,1899. 

It U. 8. Geol. Expl. 40th Par. Rept., Yol.l, p. 736, 1878. 

escarpment several thousand feet high, which is supposed by 

Mr. King to be a fault scarp. Mr. Hague, who has described 

in detail the range and from whose descriptions Mr. King's 

conclusions are presumably drawn, does not mention the fault, 

although agreeing with the description already given of the 

folds. 

From the above, especially the fact of the ridge being for at 

least a portion of its length synclinal, 'it is probable that the 

mountains, on the whole, are due to erosion.1S 

Davis's first contribution to the subject took the 

form of a critical review of Spurr's paper.16 Afterward he twice visited the Great Basin in order to 

study the physiography of the ranges, and each visit 

was followed by a publication. 17 The three papers 

are of signal value in that they furnish definite physiographic criteria for the recognition of mountain faces 

which have been produced by faulting. Some, perhaps most of the criteria had doubtless been used by 

one or another of the earlier observers. Their recognition of faults marginal to the ranges would otherwise 

have been impossible, but the criteria had not been 

formulated, and their formulation was essential to 

demonstrative and convincing diagnosis of individual 

ranges. 

In the following abstract of Davis's results no 

attempt is made to preserve his terminology, and the 

sequence of his presentation is also ignored. It is to 

be observed, moreover, that some matters which 

might' properly receive mention are omitted because 

I shall have occasion to cite them in other connections. 

1. On the assumption (a) that a normal fault of 

orographic magnitude is gradually produced in a 

region initially of low relief and underlain by homogeneous rock, (b) that the disjoined crust blocks are 

at the same time tilted in the direction toward the 

(relatively) uplifted block, (c) that the drainage conditions are such that debris from the lifted block is 

deposited on the thrown block, and (d) that the rate 

of faulting is such that the dissection of the rising 

block keeps pace with it, there will result: (a) The 

horizontal plan of the mountain base-the line of 

contact between the rising block and the deposited 

detritus-will be a line of simple curvature. (b) There 

will be a definite change of slope along this line. (c) 

There will be carved in the'mountain block a series of 

canyons, and these will hold their V section to the 

mountain base. (d) The interstream ridges will end 

abruptly at the mountain base, their ends being alined 

along that base. (e) The ends of the ridges, if unmodified by erosion, will be triangular facets, having the 

slope of the fault plane. Their modification by erosion 

will tend to dissect them by steep, short canyons, 

'between which there will be triangular facets. 

2. If the faulting is more gradual, or if after a period 

of activity it becomes slower, the dissecting canyons 

15 Spurr, J. E., op. cit., p. 221. 

16 Davis, W. M., Science, new ser., yolo 14, pp. 457-458, 1901. 

If Davis, W. M., The mountain ranges of the Great Basin: Harvard ColI. Mus. 

Compo Zoology BulL, vol. 42, pp. 129-177, 1903; The Wasatch, Canyon, and House 

Ranges: Idem, vol. 49, pp. 17-56, 1905. 
6, . STUDIES OF BASIN-RANGE STRUCTURE 

will not hold the V section to the mountain base but 

will broaden their beds, and the flood plains within 

their wider mouths will be continuous with the alluvial 

fans outside the mountain base. The spur ends will 

still be alined, but in their maturer sculpture the 

definite facets will not appear. 

3. When the movement creating the mountain has 

ceased the broadening valleys of dissection will eventually coalesce in their lower parts and the separating 

spurs will then no longer reach the line of the fault; 

the mountain base, or rock base~the line separating 

visible rock bodies from the alluvial slope-will be 

sinuous, winding in and out among sprawling spurs, 

and the features peculiar to an uplifted ridge will be 

lost. 

All the typical characters under paragraph 1 are 

subjett to modification by local conditions, and especially by inequality in the power of the rocks that 

constitute the uplifted block to resist the agencies of 

sculpture. 

Wherever the mountain range is composed of bedded rocks and the structure lines are oblique to the 

margin of the range, the margin is presumably determined by a fault, for in a system of residual ranges, 

determined by selective erosion, the margins run 

parallel to the lines of structure. As it is quite possible that a marginal fault may coincide with the 

strike of the beds it dislocates, faulting is not disproved by accordant structure lines, but discordance 

of structure lines is a character indicative of faulting. 

Davis discusses also the topographic development 

of the back slope of a titled block, as well as that of a 

block lifted between two faults. His formulation of 

criteria is largely deductive, but all the criteria were 

tested by observation, and his papers illustrate their 

application in the diagnosis of range type by a number 

of examples. 

After Davis's visit to the Wasatch and other ranges 

and before the printing of his second paper, the material of the paper was communicated in oral abstract 

to the Geological Society of America as part of a 

symposium on Basin Range structure. In continuance of that discussion Johnson wrote on the structure 

of block mountains in New Mexico,18 dealing particularly with the fault systems of the Sandia and Magdalena Mountains. The displacement in each of these 

areas is distributed through a large number of faults, 

which agree in the direction of their throw but differ 

as to the amount. The mountain range, in each 

area, exists because the displacement on a particular 

plane is large. 

The second of Davis's papers was followed in 1904 

by a contribution by Louderback.19 He studied a 

group of ranges near Humboldt Lake, Nev., with spe1I10hnson, D. W., Block mountains in New Mexico: Am. GeolOgist, vol. 31, pp. 

13.5-139, 1003. 

II Louderback, G. D., Basin Range structure of the Humboldt region: Oeol. Soc. 

America Bull., VOl. 16, pp. 28H46, 11104. 

cia! reference to the question of structural type. As 

compared with the work of the Fortieth Parallel 

Exploration his study had the advantage of specially 

focused attention. It differed from that of Davis 

in that it included features of internal structure as 

well as of external form. Its geographic field comprised the Humboldt Lake Range, the adjacent intermont valleys, the southern part of the Star Peak 

Range, and a portion of the East Range called Table 

Mountain.2o 

The body of 'each range consists of Triassic and 

Lower Jurassic strata, which are folded and faulted. 

They are also somewhat altered and are invaded by 

plutonic rocks. Collectively the Mesozoic strata and 

intrusive rocks are called the bedrock complex. 

Above the bedrock is an unconformable series of volcanic' rocks, comprising rhyolite and tuff below and 

basalt above. Although the areas covered by this 

series are not now continuous they are correlated by 

means of common characters, and it is believed that 

they were originally connected, the lavas covering a 

large part of the district. Prior to the epoch of eruption the surface had been reduced by erosion to a 

condition of low relief; after the spreading of the basalt 

it was a gently sloping plain. The deformation that 

created the existing ranges and valleys took place after 

the epoch of eruption, and its type is expressed in the 

present attitudes and relations of the volcanic beds. 

The basalt surfaces in particular serve to characterize 

the deformation. No folds are thus shown but many 

faults, and the faults are normal. The eastern slope 

of the West Humboldt Range is sheathed by basalt, 

which inclines in unbent blocks to the east. The west, 

slope exposes little besides the bedrock complex with 

its ancient folds but nevertheless affords evidence of 

.the later faulting. There are minor features of sculpture interpreted as consequent on relatively recent 

normal faulting because not yet adj usted to the distribution of more or less resistant rock masses. The 

line of the mountain base runs independently of the 

strikes of Mesozoic strata; the mountain gorges are 

narrow to the mountain base, where they end abruptly; 

the mountain spurs also end abruptly along the same 

line; and these characters serve to indicate the position of a marginal fault. The history and structure 

thus indicated are portrayed by Louderback in diagrams.21 

The Star Peak Range stands en echelon with the 

Humboldt Lake Range, its western base touching the 

eastern base of the Humboldt Lake Range where 

their ends overlap. The line of con tact is also a 

10 The East Range of Louderback appears on the Fortieth Parallel maps as the 

Pah-Ute Range. The Humboldt Range of Louderback, which is made up of the 

Humboldt Lake and Star Peak Ranges, is the "Koipato or West Humboldt Range" 

of the Fortieth Parallel maps and is quite distinct from the Humboldt Range of the 

Fortieth Parallel maps, which is 150 miles farther east. The southern parts of both 

ranges appear on the topographic map of the Carson Sink quadrangle published by 

the U. S. Geological Survey. On that map Louderback's" East Range' " Is entitled, 

Stillwater and his .. Humboldt Range" Humboldt. 

IlLouderback, O. D., op. cit., p. 308. 
INTRODUCTION 7 

fault line, and the relative uplift is on the side of the 

Star Peak Range. The dislocation is interpreted. as 

an elem.ent of the later period of deformation, although 

the basalt does not contribute its direct evidence at 

this point. Elsewhere the presence of a fault following 

the western base of the range is indicated by the same 

features as in the Humboldt Lake Range and in addition by the occurrence of a fresh scarp in the alluvial 

apron just outside the mountain base. 

Table Mountain, east of the Humboldt Lake Range 

and separated from it by a wide valley, bears a cap of 

volcanic rocks in which the beds are nearly horizontal. 

The basaltic surface is not a simple plane but is composed of a number of minor plane elements, which 

stand at different levels and are separated by sharp 

vertical breaks or by channels of erosion. The slopes 

on both sides of the table are occupied chiefly by the 

bedrock complex, but on the west there is a partial 

covering of basalt. This cover is not a continuous 

mclined sheet but is a series of horizontal bodies 

constituting steps, and there is evidence that a compound fault separates the tabular mountain from the 

valley west of it. 

The alluvial surface of the valley between the Humboldt Lake Range and Table Mountain is interrupted 

in one place by a small ridge that is a miniature of the 

Humboldt Lake Range. It has the same trend and is 

composed of the same bedrock complex, with an 

overlying body of similar volcanic rocks, which dip 

eastward and are sliced by parallel normal faults. 

The valley west of the range contains two allied 

occurrences, in one of which the lava beds dip to the 

northeast and in the other to the north. 

This relatively detailed local study serves to verify, 

so far as the features of one locality may verify, 

several of the results of earlier studies, and it adds 

materially to the mental picture of Basin Range 

structure. By .the aid of the volcanic beds the results 

of earlier and later deformations are clearly differentiated, and the later deformations are shown to be 

alone responsible for the greater features of the existing 

relief. At the same time the block faulting is shown to 

be less silnple than would be understood from some of 

the earlier descriptions and to correspond essentially 

to the type described by Johnson. Instead of a 

system of simple, broad) tilted blocks, each one of 

which determines a range by its higher edge and a 

valley by its' lower, there is a more complicated 

system of dislocation and one which involves a less 

extreme contrast in altitude between the structural 

mountains and structural valleys. 

In a series of papers,22 the first of which appeared in 

1908, Keyes advanced and amplified the theory that 

the Basin Ranges are largely remnantal, their promi .. 

nence having resulted from differential degradation, in 

which the wind has been chief agent. The ranges 

exist because their rocks are harder than those of the 

intermont valleys. They have steep fronts because 

deflation is at a maximum along their bases. Alined 

truncation of mountain spurs is not demonstrative of 

faulting, for it may result also from eolian widening of 

valley plains by lateral corrasion. Keyes's citation of 

localities indicates that the theory was developed 

among the desert ranges of New Mexico, but it has 

been applied also to the mountain system of the 

Great Basin. Speaking of the Great Basin, he says :23 

The present mountains seem to owe their existence not so 

much to general flexing or to recent and profound faulting as 

they do to the differential effects of true desert leveling, in which 

the most resistant rocks longest retain the highest elevations. 

In another place,24 after discussing the relative 

efficiency of erosional processes, he concludes: 

The American arid country was at the beginning of the present geographic cycle essentially a peneplain recently uplifted. 

This conclusion is believed to be amply attested by the great 

remnantal plains which are still found standing high above the 

existing plains surface. Above the latter more than 4,000 feet 

rises, for instance, the unique Mesa de Maya. The numerous 

plateau plains of the dry region appeB:,r to have a like significance. 

The evolution of the present relief expression of the desert 

country is not believed to be from a surface initially of rugged 

mountainous topography and through the sculpturing agencies 

of running water but is thought to be from a plains surface 

through eolation principally. 

The origin of the Basin Ranges and of the desert ranges generally is therefore regarded as due in the main to extensive 

and vigorous differential deflation on a region that had been 

previously flexed and profoundly faulted and then planed off, 

bringing narrow belts of resistant rocks into juxtaposition 

with broad belts of weak rocks, the former now forming the 

desert highlands and the latter the desert lowlands, or intermont plains. 

21 Keyes, C. R., Arid monadnocks: Jour. Geography, vol. 7, pp. 30-33, 1908; 

Some relations of the older and younger tectonics of the Great Basin region: Iowa 

Acad. Sci. Proc., vol. 15, PP. 145-146, 1908; Differential effects of eolian erosion upon 

rock belts of varying induration (abstract): Science, new ser., vol. 29, pp. 752-753, 

1909; Erosional origin of the Great Basin ranges: Jour. Geology, vol. 17, PP. 31-37; 

1909; Relations of present profiles and geologic structures in desert ranges: Geol. 

Soc. America Bull., vol. 21, pp. 543-564, 1910; Fault scarps of the Basin Ranges 

(abstract): Science, new ser., vol. 33, p. 466, 1911; Critical criteria on Basin Range 

structure: Science, new ser., vol. 37, p. 226, 1913; False fault scarps of desert ranges: 

Geol. Soc. America Bull., vol. 26, p. 65,1915. The subject receives attention also in 

the following papers: Base·level of eolian erosion: Jour. Geology, vol. 17, pp. 659-663, 

1909; Deflation and the relative efficiencies of erosional processes under conditions of 

aridity: Geol. Soc. America Bull., vol. 21, pp. 565-598, 1910; Deflation scheme of the 

geographic cycle in an arid climate: Geol. Soc. America Bull., vol. 23, pp. 537-562, 

1912; Arid plateau plains as features of eoUc erosion: Iowa Acad. Sci. Proc., vol. HI, 

pp. 157-162, 1912. 

II Keyes, C. R., Geol. Soc. America Bull., vol. 21, p. 549, 1910. 

a.ldem, p. 598. 
8 STUDIES OF BASIN-RANGE STRUCTURE 

Of the "fault scarps" of the BasiD. Ranges he 

says:25 

In the instance of the Basin Range type of mountain structure normal faulting on a prodigious scale was long regarded as 

the principal factor. Its mountain block was considered as 

upraised. The face of the hard mountain rock rising abruptly 

out of the less resistant valley deposits was believed to represent a true fault scarp. This hypothesis is not exclusive, nor 

is it very satisfactory. 

A main objection to the theory is the fact that the evidences 

of recent displacement are seldom ever disclosed at or even near 

the so-called fault scarps. Whenever the line of major faulting is discovered it is miles away from the mountain foot, out 

on the intermont plain. 

On the theory of general denudation of arid regions chiefly 

through means of eolic rather than aqueous agencies the belt 

of maximum deflation is at the foot of the desert ranges, where 

the mountain meets the plain. Within the limits of this narrow belt the topographic result is a tendency toward a steep, 

plainlike slope. This piedmont belt chances also to be the 

horizon where torrential water action is most pronounced, 

cutting deep canyons in the mountain and spreading out detrital 

fans on the plains. In the struggle between water and wind 

for corrosive supremacy the results in the mountain area are 

a succession of sharp ridges trending at right angles to the range 

axis, sharply truncated at their lower end by deflative action. 

The faceted mountain foot thus produced resembles closely 

the ideal effects of a fault-bounded upraised mountain block 

the dissection of which is well advanced. 

The following passage 26 is preceded by a statement 

of the work of windjn grading plains: 

Whenever bare or hard rock masses are encountered, there 

is vigorous sand-blast action. Thus, hypsometrically, among 

the desert ranges, which are all composed of very hard rocks 

usually devoid of a soil mantle, the notably. exposed zone is 

at the very base of the mountains, or immediately above the 

surface level of the surrounding plains. This is probably the 

chief reason why there are no foothills flanking the mountain 

ranges of the desert, why mountain and plain so sharply meet, 

and why the bases of the desert ranges are often so abrupt a:n.d 

straight as to suggest at once the presence of fault scarps as an 

explanation of the steep faces of the mountains. 

When we institute search for direct evidences of fault lines 

which are supposed to give rise to escarpments, we usually look 

in vain. Although the mountain inay be a faulted block the 

movement, however profound, is commonly discovered to be 

of ancient date. Its fault plane is found to be far out in the 

plain, often at a distance of 4 or 5 miles. The intervening 

space has a smooth and gently sloping rock floor and has every 

appearance of a marine plain of denudation from which the 

sea has but recently retired. 

In a later note, after ascribing to Spurr an assertion 

"that no one has ever seen the fault lines blocking out 

the desert ranges," Keyes 27 says: 

With the challenge of the Basin Range hypothesis there has 

come a demand for cita~ions of concrete examples in support of 

the theory. Thus far, after the elapse of a full decade and after 

frequent repetition of the demand, the evidence has not been 

forthcoming. 

Baker's contribution to the subject 28 was based on 

observations made during three expeditions into dift5 Keyes, O. R., Science, new ser., vol. 33, p. 466, 1911. 

IS Idem, vol. 29, p. 753, 1909. 

17Idem, vol. 37, p. 226, 1913. 

IS Baker, O. L., The nature of the later deformations in certain ranges of the 

Great Basin: Jour. Geology, vol. 21, pp. 273-278, 1913. 

"ferent regions of the southwestern part of the Great 

Basin. Those expeditions were primarily concerned 

with Tertiary formations and with the history recorded 

in their deposition, deformation, and erosion. Strata 

of later Tertiary age have been folded and then beveled 

by erosion, and the erosion surface cut from them has 

in places been warped into valley synclines and mountain anticlines and elsewhere faulted. The faulting 

is in part associated with grabens and in larger part 

with tilted blocks. The longitudinal profile of a 

block-faulted range is essentially that of the longer 

axis of an anticline. Some of the Basin Ranges are 

structural upwarps. Many of the intermont basins are 

true spoon-shaped synclines. 

In the Death Valley region, where faulting has probably 

taken place on as great a scale as anywhere in the Great Basin, 

closely folded Tertiary strata, referred to the Miocene by Spurr 

and Ball, bound the valley side of the Funeral Range fault. It 

is difficult to conceive how this folding and thrusting can have 

been caused by tensional stresses manifested in normal faults. 29 

The recency of the movement to which the existing Basin 

Ranges owe their forms is such as to leave intact, in large measure, the superficial rocks of the lithosphere, even when these lie 

high in the zone that was affected by fracture during this deformation. We know this because there is still preserved much of 

the erosion surface developed previous to this deformation. 

It also happens that a large portion of this superficial rock is of 

a competent nature and, without any load, seems quite as 

likely, or more likely, to break than to fold. The Basin Ranges 

may very possibly have originated by tangential compression. 

Their present elevations and structures may be a joint product 

of the initial intensity of the deformative forces and of the reiative resistance to deformation of the strata involved. This is a 

very elementary conception but is as far as the writer is willing 

to go on his present data. 

The mid-Mesozoic deformation was apparently the most 

intense, the folds in the Death Valley region and in the Pilot 

Range being as close as those of the central Appalachians. 

The first later Tertiary deformation was probably on the whole 

less intense, although locally noncompetent beds are closely 

crumpled and overthrust. The writer's studies have not been 

of such a detailed nature as clearly to separate the effects of 

these two movements on the older rocks. The most recent deformation is the least intense, at any rate as exhibited on the surface 

but is the one which is responsible for the present orographic 

features of the Basin Ranges. What has happened in the zone 

of flow, or in the zone of combined fracture and flow, during 

this latest deformation, we have no means of knowing, since 

erosion has not yet laid bare these zones. But it is probable that 

in the southwestern portion of the Great Basin the competent 

brittle rocks at the surface or close to the surface have deformed 

somewhat differently from the dominantly sedimentary rocks 

of the Rocky Mountains, the Jura, the California Coast Ranges, 

the central and northern Appalachians, the Alps, and the Himalayas, which are taken as classic types of tangentially compressed 

mountains.SO 

The subject of the preceding summary is the development of opinion as to the general nature of the structure of the Basin Ranges. The growth of knowledge 

of range structure has been mentioned only as it has 

affected the development of opinion, and problems of 

primary causation have been avoided. In the chapters 

which follow I shall present and discuss the results of 

10 Idem, p. 275. 

10 Idem, pp. 277-278. 
INTRODUCTION 9 

personal observations not previously published. Up 

to a certain point the development of opinion was 

harmonious, in the sense that each new view was an 

amplification of the preceding and was accepted by 

earlier investigators, but the harmony was broken by 

Spurr and has not since been restored. The stimulus 

of an antagonistic view sent Davis to the field and 

focused the attention of Louderback and Baker, and 

whatever the merits of the view its announcement has 

been eminently successful in the promotion of critical 

inquiry. It r~mains to be seen whether an equal pro62436-28--2 

motion will result from the equally radical contention 

of Keyes. My own later work received its impulse 

from Spurr's paper. I went to the field the following 

sumlner and visited a number of ranges in central and 

western Utah. An accident prevented prompt publication of my observations, and the motive for early 

pUblication was afterward largely removed by the 

appearance of Davis's papers, which anticipated many 

of my results. In returning to the subject at the 

present time I am able to add the data from a number 

of brief local studies in Utah, Oregon, and California. 
CHAP'1'ER II. WASATCH RANGE, UTAH 

GENERAL FEATURES 

The general trend of the Wasatch Range is with 

the meridian. As seen from the west it is a bold, 

high ridge. From the east its aspect is less c?mmanding. Its western face is an escarpment, sprIng-: 

ing abruptly from the broad, low valley plains. 

Its eastern flank is joined to a mountainous upland, 

which has in part the character of a dissected plateau. 

The drainage of its eastern flank all reaches the 

western lowland, a small part only passing around 

the ends of the range and the remainder crossing its 

axis in a series of deep gorges. Because it is bordered on one side only by valley plains, such as are 

characteristic of the Great Basin, it has not always 

been classed with the Basin Ranges, but it is their 

close ally in history and structure. 

With a length of 130 miles, from Nephi to Collinston, it has a general height above the bordering plains 

of 4,000 feet, and a dozen peaks rise from 1,500 

to 4,000 feet higher. Beyond Collinston at the 

north a low ridge reveals the continuance of the 

axis of uplift and ties the Wasatch to an unnamed 

range northwest of Cache Valley. Beyond Nephi 

at the south the axis is represented for 30 miles by 

the San Pitch Mountains, a little-studied range of 

plateau type. 

The structure is complex, and our knowledge of 

it is imperfect. Certain general features were determined by the exploratory work of Emmons 1 and 

Hague,2 others have been contributed by Blackwelder 3 and Loughlin,4 and local details have been 

added by HoweU,5 Boutwell,6 Butler,? and Hintze,S 

but the work of comprehensive and adequate study 

has not yet been undertaken. The following 'sketch 

of structure and history, which is based on the recorded work of these geologists, is necessarily in1 Emmons, S. F., Wasatch Range: U. S. Geol. Expl. 40th Par. Rept., vol. 2, 

pp. 340-392, 1877. 

2 Hague, Arnold, Northern Wasatch region: Idem, pp. 393--419. . 

3 Blackwelder, Eliot, New light on the geology of the Wasatch MountalDs, Utah: 

Geol. Soc. America BulL, vol. 21, pp. 517-542, 1910. 

4 Loughlin, G. F., Reconnaissance of the southern Wasatch Mountains, Utah: 

Jour. Geology, vol. 21, pp. 436-452, 1913. 

~ Howell, E. E., The Basin Range system of southwestern Utah and southeastern Nevada: U. S. Geog. and Geol. Surveys W. 100th Mer. Rept., vol. 3, pp. 

231-264, 1875. (See pp. 231-237, 251-253.) Howell's publication preceded the more 

comprehensive account of the Provo Wasatch by Emmons (1877), but his field 

studies (1872) followed those of Emmons (1869), and some of Emmons's results 

received advance publication by King in 1870. (See U. S. Geol. Expl. 40th Par. 

Rept., vol. 3, pp. 451-456, 1870.) 

6 Boutwell, J. M., Stratigraphy and structure of the Park City mining district, 

Utah: Jour. Geology, vol. 16, pp. 434--458, 1907; Geology and ore deposits of the 

Park City district, Utah: U. S. Geol. Survey Prof. Paper 77, 1912. 

7 Butler, B. S., and Loughlin, G. F., A reconnaissance of the CottonwoodAmerican Fork mining region, Utah: U. S. Geol. Survey Bull. 620, pp.165--226, 

1915. 

8 Hintze, F. F., A contribution to the geology of the Wasatch Mountains, Utah: 

New York Acad. Sci. Annals, vol. 23, pp. 85-143, 1913. 

10' 

complete and in certain respects is provisional. 

Such contributions as have resulted from my own 

recent field work are not here included but will 

be found in a review at the end of the chapter. 

The rocks that compose the body of the range are 

of Archean,' Algonkian, Paleozoic, Triassic, and Jurassic age, and there are large masses of granite. Two 

notable unconformities have been recognized among 

the sedimentary formations, but, so far as known, 

deposition was continuous from Carboniferous to 

Jurassic time. The Jurassic deposition was followed 

by a diastrophic revolution. The formations were 

folded and faulted on a grand scale, and among the 

faults were extensive overthrusts. The intrusion of 

the granite bodies is assigned to the same period. The 

mountains and valleys created by these dislocations 

were not coincident with the present mountains and 

valley's. The position of the uplift a'ssociated with the 

intru~ions is now marked, it is true, by lofty summits, 

but the line of the adjacent profound syncline crosses 

the Wasatch Range, in the latitude of Salt Lake City, 

at right angles. At the south the axis of an important 

an ticline enters the pres en t range 0 bliq uely , and at 

the north the upbuilding by overthrust is not expressed 

by the existing relief. 

The topography created by dislocation was so far 

reduced by erosion in Cretaceous time that a transgression by the sea spread sands of Dakota age over 

worn edges of Jurassic, Triassic, and upper Carboniferous strata. The evidence of that transgression has 

been found only on the eastern flank of the range. 

After the retreat of the sea came other crustal changes, 

and then a long period of relative quiet in which the 

general movement of detritus was from west to east 

and a broad area at the east received terrestrial and 

lacustrine deposits. These deposits, which are referred 

to the Eocene, rest in the Wasatch. district on all 

formations of earlier date, from Archean to Cretaceous. 

At the extreme south and also near Salt Lake City 

their original area appears to have included portions 

of the Wasatch axis. In the Wasatch district the 

Eocene strata have been moderately flexed and faulted, 

and they have been involved in the greater displacements which created the Wasatch Range. 

The diastrophism to which the greater features 

of the present relief are due is clearly post-Eocene, 

but the date of its beginning can not yet be assigned. 

Its changes have continued to the present time, but 

only a small fraction are post-Pleistocene. They 

appear to have made large progress before an epoch of 

Pliocene time when lake beds were deposited in a chain 

of valleys adjoining the eastern flank of the range, 
." 

WASATCH RANGE, UTAH 11 

but they were even then so far from completion that 

the lake beds themselves have been faulted and tilted. 

One crustal change of the Tertiary system was of 

a broad or epeirogenic character and resulted in a 

general reversal of the slopes controlling drainage. 

The field of Eocene deposition became an upland, 

and a western district, which had been a field of Eocene 

degradation, beCf\.me a lowland. The upland is part 

of the physiographic province known as the Colorado 

Plateaus, and the lowland is part of the Basin and 

Range province. At the north the boundary between 

the two provinces lies east of the Wasatch Range, but 

at the south the axis of the range is crossed obliquely 

by the boundary. 

A coordinate crustal change was orogenic-the 

creation of mountain ridges and. intermont troughs. 

The Wasatch Range was separated from the chain 

of broad valleys that follow its western base by a great 

fault. 

Such a diastrophic event as the creation of a great 

fault is not solitary. The force creating it must have 

other effects, and even if we could conceive of the great 

dislocation as an initial and causeless occurrence we 

must recognize the need of a system of crustal adjustInents to prevent the formation of a void. It is therefore probable that minor deformations and dislocations 

have acc01npanied the major dislocation along the 

western front of the range; but as yet relatively little 

is known of them, and it is not easy to discriminate 

the products of later and earlier diastrophism. Emmons 9 has pointed out that in the region of Timpanogos and Provo Peaks a normal fault parallel to the 

frontal fault is expressed in the topography of the 

range. Loughlin10 observed that a system of narrow 

ridges and troughs close to the western base of the range 

near Santaquin corresponds to a system of minor 

faults that involve Tertiary strata and lavas. 

Blackwelder 11 has tentatively referred certain transverse faults in the Ogden region to the later diastrophism. All students of structl~re in the mining region 

about Alta and Park City recognize more than one 

period of faulting, and Hintze 12 regards certain faults 

of later date as probably synchronous with the frontal 

fault of the range. N one of the structural features 

that have been thus correlated with the frontal fault 

are comparable with it in magnitude; their displacement and their linear extent are relatively small. 

The existence of the frontal fault, first announced 

by Emmons, has been recognized by all later students 

of the structure of the range. It has not been specifically denied by the writers who regard most of the 

Basin Ranges as residual, although denial is probably 

implied by certain of their general statements. On 

the other hand, the discussion by Davis of the physiDEmmons, S. F., U. S. Goal. Expl. 40th Par. Rept., vol. 2, p. 345,1877. 

10 Loughlin, G. F., Jour. Geology, vol. 21, pp. 447-451,1913. 

II Blackwoldor, Eliot, Geol. Soc. America BulL, vol. 21, pp. 539-541, 1910. 

II Hintze, F. F., New York Acad. Sci. Annals, vol. 23, pp. 137-140, 142, 1913. 

ography of the Wasatch escarpment has made the 

escarpment in some sense a type, and in that character 

it warrants a full presentation of the evidence by which 

it is recognized as a product of block faulting. 

Up to the present time only physiographic characters 

have been adduced in support of the view that the 

escarpment was created by faulting. In my judgment 

the physiographic evidence is adequate, but not all 

are prepared to f!.ccept it, and for this reason I shall 

begin the discussion of the subject by presenting evidence other than phy~iographic. Afterward several 

classes of physiographic evidence will be taken up, 

and in their treatment the phenomena of this range 

will be used as a text for the discussion of the criteria 

for the recognition of block-mountain structure. 

THE FRONTAL FAULT 

NOMENCLATURE 

In the terminology of faults this paper follows the 

recommendations of the committee of the Geological 

Society of America on the nomenclature of faults, as 

printed in volume 24 of the society's Bulletin. The 

confusion caused by diversity of usage may be 

escaped by the adoption of a standard, and the 

standard offered by the committee has the important 

merit that it takes full account of the complexity of 

the geometric relations and thus enables the user to 

guard against the confusion that arises from imperfect conception of the relations expressed. 

The movements involved in faulting-like all other 

movements-are relative. To define their directions 

it is necessary to refer them to some body or place 

regarded as fixed. As the movements on the plane 

of the frontal fault of the Wasatch Range have a 

large vertical component their directions are conveniently indicated as upward and downward; but in 

that indication the words are not used in their most 

familiar sense, and for that reason there is possibility 

of misunderstanding. In the nomenclature of faults 

the prefix" up" does not imply increase of distance 

from the earth's center or from the plane of mean sea 

level but only the direction of movement of the rock 

body on one side of a fault plane with reference to the 

rock body on the other side of the same plane. To 

say that the one body moved upward is the exact 

equivalent of saying that the. other body moved 

downward. Similarly the statement that the horizontal component of the movement of one faulted 

body was eastward is equivalent to saying that the 

movement of the companion faulted body was westward. The movement of each body is referred to the 

other body and not to a terrestrial meridian. 

The waste from a range, including the detritus 

washed fr01n the range front and that discharged at 

the mouths of the canyons, is built into a sloping 

plain known as the alluvial apron. This plain is 

called also the piedmont plain or simply the piedmont. 
12 STUDIES OF BASIN-RANGE STRUCTURE 

It may be interrupted by a scarp or scarps running 

parallel to the rock base of the range and caused by 

dislocation of the alluvium. Such scarps were originally called faUlt scarps, but that title has been diverted 

to another use, and for that reason the scarps in the 

alluvial apron are in this paper called piedmont scarps. 

A special section is devoted to their discussion. 

LAKE BONNEVILLE 

Some of the features of the frontal fault are affected 

by features of Lake BonnevilJe. At least twice in 

Quaternary time the basin west of the range was 

occupied by a deep lake, the water surface rising from 

some low level and afterward falling. The last great 

rise carried it about 1,000 feet above the level of 

Great Salt Lake, and all parts of the range front and 

piedmont slope below that level were modified by the 

attack of shore waves. For about one-fourth of the 

length of the range the modification was confined to the 

piedmont and affected only a portion of its slope; for 

the remainder it included the whole of the piedmont 

and a portion of the rock face. The rock face was 

affected chiefly by erosion but in places received a 

deposit of beach gravel. The piedmont alluvium was 

superficially reworked, with the washing out of a portion of the finer debris and the rounding and sorting 

of the coarser, which was so rearranged as to constitute 

a series of beaches contouring the slope. 

The lower parts of the piedmont slope received 

argillaceous and marly deposits and were made flatter.· 

The material of the piedmont thus includes alluvium, 

shore deposits, and lake beds, a. heterogeneous aggregate for which usage has no less cumbrous designation 

than unconsolidated formations. In many places in 

this chapter the short title alluvium is substituted for 

the more exact phrase. 

At the time of the last great expansion of the lake 

it found outlet across a pass occupied to a depth of 

400 feet by alluvium. The alluvium was· quickly 

scoured away, and the lake surface fell to the level of 

the rock sill at the outlet, where it remained for a long 

time. That level is marked along the Wasatch front 

by a shore line of exceptional strength, to which a 

special name has been given-the Provo shore line. 

The highest shore line, exceptionally conspicuous 

because itis highest, is called distinctively the Bonneville shore line. The time during which the lake 

stood at the level of the rock sill is called the Provo 

epoch. Certain diastrophic events have known relations to parts of the lake history. If earlier or later 

than all the wave work they are styled pre-Bonneviile 

or post-Bonneville; if later than the Provo epoch, 

post-Provo. 

An aspect of the Bonneville shore line is shown in 

Plate 1, A. The waves have eroded the range front 

along a horizontal line, creating a terrace and a cliff 

or row of cliffs. The Provo shore line is less conspicuous in this view, its most marked feature being a 

terrace near the center. In Plate 12, B, the Provo 

line is the more conspicuous, appearing as a rock 

shelf near the base of the spur. In Plate 8, A, two 

lines catch the eye; the upper of the two is the Provo; 

the Bonneville, near the top of the escarpment, is less 

easily discovered. The Bonneville and Provo shore 

lines are marked by color boundaries near the middle 

of Plate 7, B, and cliffs of the Bonneville shore line 

appear at the right in Plates 4, B, and 6, A. 

PRODUCTS OF OF A ULT FRICTION 

GENERAL CHARACTER 

According to the previously cited committee of the 

Geological Society of America, "A fault, in its simplest 

form, is a fracture in the rock of the earth's crust, 

accompanied by a displacement of one side with respect to the other in a direction parallel with the 

fracture. " The fracture surfaces of the two rock 

b.odies are the walls of the fault. Nearly always 

during the faulting the walls are in contact or partly 

in contact, and there is friction between them. 

A result of the friction is the ·abrasion of one or both 

walls. By the abrasion smooth surfaces are produced, with striation in the· direction of motion. The 

striation consists of a system of parallel grooves with 

intervening ridges, and though typically these are 

.minute, they may also be large, and if so they appear 

as fluting. The coordinate product of abrasion is 

detritus, and the detritus remains between the walls, 

constituting fault rock. The smallest fragments are 

minute, making collectively a fine powder or, if adhesive when moist, a plastic "gouge"; the largest fragments are "horses";· and between these two extremes 

are breccias. In general the fragments are sharply 

angular, but to this rule there are exceptions. In a 

matrix of gouge may occur "boulders of attrition," 

with blunted angles and slickensided facets or with 

forms unevenly rounded. The fragments may be 

either loose or cemented into a coherent mass. Some 

fissure veins are bodies of cemented fault rock. 

The effects of friction may extend beyond the sur~ 

faces of the walls and modify the wall rocks. N ear the 

fracture surface the rock may be made to flow in the 

direction of the fault movement. Evidence of such 

flow may appear in the bending of strata, in the welding together of strata with obliteration or obscuration 

of the partings between beds, in brecciation, in foliation or sheet structure parallel to the fracture surface, 

and in small a.reas of subsidiary surfaces of slipping 

revealed by polish and striation. Where strong and 

weak rocks are-associated the flow of weak rocks may 

be accompanied by the fracture of strong rocks. 

Where strong rocks show evidence of flow it is inferred 

that the flowing took place at considerable depth 

within the crust. The collocation of faulting with a 

flowing of the rock adjacent to the fault suggests the 

border land between what Van Rise has called the 

zones of fracture and flowage. 
WASATCH RANGE, UTAH 13 

The tract of modified wall rock is sometimes called 

a shear zone, and the nalne shear zone is also applied 

to dislocations, equivalent to faults, in which definite 

walls are not developed but Inerely sheetlike tracts of 

crushed or foliated rock. 

The opposed walls in any part of a fault may be of 

like or unlike material. The intervening fault rock 

may be derived from immediately adjacent wall rock 

or Inay consist mainly of fragments unlike the local 

rock of either wall. The cementing material may be of 

local origin, or it may have been brought in solution 

from distant sources and may have reacted chemically 

on fault rock and wall rock. Much of our knowledge 

of the petrographic features of faults has been gathered. through the exploitation and study of fissure 

veins. 

In the polished and finely striated surfaces-slickensides-it is advantageous to recognize two types, 

although they ar.e connected by the occurrence of intermediate form.s. One is approxilnately plane or at least 

has a rectilinear section in the direction of motion; the 

other is conspicuously fiexuous. Plane slickensides are 

characteristic of the main walls of faults; flexuous slickensides of the slip surfaces of branching and subsidiary 

fracture~. As I interpret the phenomena, the slickensides on subsidiary fractures are flexuous because a 

small amollnt of differential movelnent has not sufficed 

to obliterate initial irregularities of the fracture surfaces-irregularities that arise from inequalities of 

rigidity and of strain. If similar irregularities affected 

the initial surfaces of great faults they have been 

effaced during the progress of the greater movement. 

According to this interpretation, flexuous slickensides 

indicate differentiallnovelnent of snlall Rrnount. 

c 

FIGURE 2.-Types oC surface cracks associated with the horizontal fault 

slip which caused tho California earthquake oC April 18, 1906. Arrows 

show directions 01 movemont of underlying crust blocks 

Successive slippings of a progressive fault may not 

coincide accurately in position of slipping surface; a 

single slipping surface in one part of a fault may be 

represented by a group of parallel surfaces in another 

part, and all the surfaces may be of the plane type. 

Where sheet structure is developed within a fault wall 

there may be small movements on the partings between 

sheets, and the resulting slickensides may be of the 

flexuous type. 

Slipping surfaces of another class are not parallel 

but oblique to the main fault surface. Their obliquity 

follows a law, and the law is illustrated by analogous 

phenomena connected with the California earthquake 

of 1906. The fault 1l10Vement which caused that 

earthquake was horizontal, on a fault plane trending 

northwest. The crust block on the southwest side 

moved northwest. The visible expression of the faulting was mainly in a surface mantle of earth and 

included a system of oblique cracks, such as are shown 

diagrammatically in Figure 2. In places (a, fig. 2) 

the fault trace included two walls, with relative displacement as indicated by arrows, and between them 

a belt of broken earth. The principal cracks within 

the belt were oblique, as indicated. In other places 

(b, fig. 2) the walls were not developed and the fault 

trace consisted of a system of oblique cracks, as indicated. From the walls of the fault trace ran branching cracks (e, fig. 2), the divergence being at various 

a b 

l<'IOUItE 3.-Ideal sections of faults and of subsidiary slickened partings, to illustrate. the relations of the attitude of the partings to 

normal faults (a) and reverse faults (b) 

angles but always to the right of oue looking along the 

trace. 'The trace in places (d, fig. 2) swerved to the 

right and gradually disappeared, to reappear at the 

left en echelon. 

Reid 13 discussed the mechanics of these cracks, 

showing the relation of their systematic obliquity to 

shearing strains created in the ground by the shifting 

of the crust blocks beneath. It would be easy to 

paraphrase his analysis and apply it to oblique slipping surfaces developed in rock under shearing strain, 

but the analogy may suffice for present purposes. 

The law, both theoretic and empiric, is that the 

planes of oblique subsidiary slipping surfaces associated with a fault all deviate in the same way from the 

plane of the fault. In connection with a normal fault 

their deviation is toward the vertical; in connection 

with a reverse fault, toward the horizontal. (See 

fig. 3.) The law applies to oblique slickened partings 

within the fault rock, as well as to those' in wall rock, 

and is of service in determining the direction of slip 

on the principal fault plane. 

The earlier paragraphs of the preceding elementary 

account of faults are believed to contain nothing novel. 

The discussion of slickensides depends largely on my 

own observations. This statement is not a claim but 

an admission. The inference that flexuous slickensides indicate small slip and "the rule that the attitudes 

of oblique subsidiary slip surfaces are systematically 

related to the direction of fault movement were derived 

largely from the very phenomena to whose interpretation they are to be applied, and I would warn' the 

critical reader of the possible danger of the logicians" 

"vicious circle." 

13 Reid, H. F. Report of the [California] State Earthquake Investigation Commission: Carne~e Inst. Washington :rub. 87, vol. 2, pp. 33-35, 1910. 
14 STUDIES OF BASIN-RANGE STRUCTURE 

LOCALITIES 

Rock Oanyon locality.-The most southerly point at 

which I have examined the base of the Wasatch 

escarpment in looking for petrographic and structural 

evidence of faulting is near the town of Provo. In 

that division of the range the rocks are sedimentary, 

with a predominance of limestone, and the prevailing 

dips are easterly at moderate angles. Opposite Provo 

an anticline appears in the lower part of the escarpment, and with it is associated a quartzite, which is 

locally the lowest member of the conformable sedimentary series. In the western. limb of the anticline 

the dips are relatively steep-by estimate, 40° to 50°. 

Figure 4 gives a g~neralized profile section and IS 

w. c. 

Quartzite 

FIGURE 5.-Section exposed at the mouth of Rock Canyon, Wasatch 

Range, Utah. Q, Quartzite 

based mainly on observations made from the plain 

below. The quartzite, which is distinguished from the 

other rocks by its yellow color, crosses the face of the 

escarpment as a band and separates blue-gray limestone 

above from blue-gray limestone below. Between the 

upper limestone and the quartzite lies a terrace without 

observed outcrops, which presumably marks the position of a shale, but the lower limestone lies close to 

the quartzite, leaving no space for a corresponding 

body of shale. The upper part of the quartzite band 

shows bedding, with small dip, and it is evident that 

the formation has a thickness of many hundred feet. 

The lower part of the band gives less indication as to 

structure but is apparently conformable with the 

steeply dipping limestone. 

These features are observable for about 2 miles, 

with minor variations. Farther south the axis of the 

anticline retreats from the front of the range toward its 

heart; farther north the escarpment shows only eastward-dipping limestone. Not far from Provo the 

escarpment is crossed by Rock Canyon, which exposes 

the section sketched in Figure 5 and thus aids in the 

interpretation of the profile section in Figure 4. It is 

there seen that the quartzite rests unconformably on a 

core of foliated rock a and that the body of quartzite 

U This rock is a slightly metamorphosed sediment, originally a clay with many 

embedded pebbles. Howell calls it chloritic schist (U. S. Geog. and Geol. Surveys 

W. lOOth Mer. Rept., vol. 3, pp. 234-235, 1875). Emmons, who calls it clay slate, 

does not regard its relation as unconformable (U. S. Geol. Expl. 40th Par. Rept., 

vol. 2, pp. 345-346, 1877). Loughlin, who saw the formation in Rock Canyon and in 

another canyon farther south, speaks of it as" a conglomerate bed in the quartzite" 

(lour. Geology; vol. 21, p. 445, 1913). These conflicting interpretations ha ve aroused 

doubt in mr mind ~ to mr own, but l h&ve bad no opportunitr ~o r~vi~i~ ~h~ spot. 

in the outer or western limb of the fold is much thinner 

than the body in the eastern limb. At the point 

marked by a cross is an exposure of pale-yellow fault 

gouge. N ear by is a bench of alluvium, built as a 

delta in Lake Bonneville, and this bench is crossed by 

a fault scarp parallel to the mountain front. Just 

south ·of the canyon the westward-dipping limestone 

was examined and found' to be locally crushed, recrystallized, and shot with white gash veins; and in the 

part thus altered the bedding planes were not recognized. Slickensides were noted on a fallen block. 

The relations of the fault gouge are in doubt. At the 

point of examination it lies just outside the quartzite 

and presumably rests against it, but the contact 

was not seen. The presence of the gouge at other 

points was indicated by patches of pale color seen from 

a distance, and all such' patches noted are at the 

boundary between limestone and quartzite. (See B, 

fig. 4.) That association suggests that the gouge 

belongs to a fault walled on one side by the limestone 

and on the other by quartzite, but the sample obtained 

at the canyon mouth contains no calcareous matter. 

The designation "gouge" is perhaps not strictly applicable. The material is coherent when moist but after 

w. E. 

FIGURE 4.-Generalized profile section of the lower part of the Wasatch 

front near Provo, Utah 

drying crumbles between the fingers. For the following petrographic description I am indebted to Prof. 

George D. Louderback: 

The sample is composed essentially of quartz; other material 

is of very insignificant amount and apparently of no particular 

consequence in the interpretation of the material. The quartz 

is chiefly in the form of angular and irregularly and roughly 

rounded crystal fragments, varying in size from about one 

five-hundredth of an inch up to one-twentieth of an inch or 

larger. Some of it shows granulation in part, frequently about 

the periphery of the grains. Some of the crystals show distinct 

strain phenomena. The larger pieces in the material (up to 

three-fourths of an inch or more) are made up of numerous 

quartz grains and show the effects of crushing, granulation, 

fracturing, and strain. In two pieces distinct effects of shearing 

were noted. The particles of which the larger pieces are made 

and the small fragments first described show identical characters, and all the pe,culiarities found in one group can be found in 

the other. All of the material appears to be the result of the 

crushing of an original crystalline granular quartz rock. No 

effects of solution or deposition from solution were observed. 

I interpret these features as follows: The anticline 

belongs to the earlier .period of diastrophism and may 

originally have been a simple arching fold. In the 

A different diagnosis of the formation would not affect the discussion of the features 

ascribed to faulting, Tl1e anticline is recognized by Emmons and Loughlin but not 

br II<?W~lI. . 
WASATCH RANGE, UTAH 15 

later period it was cut away obliquely by a westwarddipping norn1al fault, and parts adjacent to the fault 

plane were sheared and partly rearranged. The 

visible portion belongs to the footwall, and the hanging wall is buried under valley deposits. The position 

of the main fault plane coincides approximately with 

the sloping face of;the escarpment near its base '(inclination 35°), but the rearrangement of the rocks 

involved slipping on other planes. The observed local 

alteration of limestone is a feature of the main fault, 

and so also is the fault gouge. 

Fort Oanyon locality.-The next point of special 

exanunation is 17 miles north of Rock Canyon and 

2 miles north of the village of Alpine. N ear Alpine 

the trend of the Wasatch escarpment swings from 

N. 10° W. to N. 80° W., and the westerly trend is 

held for 4 miles before the northerly trend is resumed. 

As shown by Figure 21, the deflection is intimately 

related to a huge body of granite which occupies all the 

southward-facing portion of the escarpment. At the 

base of the granite face are low foothills that contain 

Paleozoic limestone and sandstone. Fort Creek, 

which descends from the granite, has divided the 

foothills, opening a narrow valley called Fort Canyon. 

The contact of the granite with the foothill rocks is 

concealed by alluvium, but its position is Inarked by a 

groin, and the granite is exposed along the side of the 

groin. In an outer zone the granite is sheared and 

close to its outer surface is foliated, the foliation being 

parallel to the slope, which is at an angle of 29°. No 

slipping surfaces were discovered. The depth of the 

modified zone can not be stated, as the unmodified 

granite was not there seen in place, but the amount of 

change, as expressed by the development of parallel 

structure, was seen to diminish with distance from the 

outer face. Specimens were examined by Mr. Adolph 

I(nopf, who charactedzes the less foliated rock as "a 

crushed granite consisting of microcline, quartz, and 

chloritized biotite" and the more foliated as "a green 

schistose rock composed of quartz, feldspar, and epidote." Of the schistose rock he says: "It is probably 

a crushed facies of a basic variant of the granite 

represented by the first-mentioned specimen." 

Looking northward from this locality I noted m 

distant parts of the granite face the appearance of 

structure parallel to the outer surface.' This is 

obscurely shown in Plate 10, A, where the granite 

slope appears at the right. 

Draper locality.-Two miles west of Fort Canyon 

the trend of the escarpment swings toward the north, 

and farther on it swings toward the northeast. In 

thus curving it outlines (fig. 21) the southern and 

western sides of the great body of granite. On the 

western side the escarpment exhibits a series of large 

triangular facets (pl. 19, A), which are slightly convex 

in profil~ and have a slope near the base of 35°. 

Opposite the villag'e of Draper, which is 5 miles from 

Fort Canyon, .rocks other than granite appear ill the 

lower part of the face. The conspicuous rock is 

quartzite, but there are also schists; and the arrangement, as seen from the plain below, indicates that 

the schists lie between the quartzite and the granite. 

The outcrop of quartzite is about 2 miles long and has 

a width on the slope of 600 to 800 feet. Several small 

canyons divide it, showing that its thickness normal 

to the plane of the facets is several hundred feet. A 

nearer view, at the mouth of Little Willow Creek 

canyon, showed it to be traversed by four or more 

systems of parallel joints. 

If the bedding planes were identified, which is not 

certain, they there strilce with the mountain face and 

dip westward at about 60°. Between Bear Canyon 

and Crow Canyon were found division planes parallel 

to the plane of the facet. (See pI. 1, B.) These division surfaces bear slickensides of the plane type, and 

the plates of quartzite between them are brecciated. 

Many other polished surfaces were seen from a distance, and it is inferred that the outer face of the 

quartzite as a whole is part of the footwall of the frontal 

fault. N ear the mouth of Little Willow Canyon a 

miner's prospect hole has exposed a fault rock in such 

position as to indicate contact with the quartzite, 

although the actual contact was not exposed. The 

material, exa'inined microscopically by Mr. Knopf, is 

th us described: 

The specimen contains large quartz grains showing marked 

strain shadows; the remainder of the rock consists of finegrained sericite. This rock evidently represents a shear zone 

altered by thermal waters; possibly the rock has been strained 

subsequent to mineralization, but this is not certain. 

Mill Oreek locality.-Mill Creek issues from its canyon 12 miles north of Draper and 5 miles south of 

Salt Lake City. The contour of the range front is 

there notably simple, with a slight convexity. The 

trends of range front near the canyon are N. 17° W. 

and S. 25° E. Each side shows a triangular facet; 

that on the south is especially well developed and 

has a slope of 29°. The rocks of the n10lmtain are 

sedimentary, and the stronger strata are lilnestones, 

sandstones, and quartzites. They are mapped by 

Emmons as "Upper Carboniferous." They strike 

eastward, nearly at right angles to the trend of the 

front, and dip northward at 60° to 70°. Half a mile 

farther south the strata determine a group of furrows 

on the facet of the mountain front, but near the canyon they do not reach the outer face, which is occupied 

by a breccia. Just inside the canyon mouth and south 

of the creek the strata abut against a wall of breccia 

(see pI. 2, A), which there has a thickness of 150 to 

200 feet. North of the creek the brecciated tract (see 

pI. 3, A) is perhaps 300 feet wide but does not extend 

far up the face and is not definitely limited on the 

inner side. Either it includes large masses of strata 

or the boundary between it and the unfractured sedimentary rocks is very irregular. In part the breccia 

is wholly quartz.itic i in larger part the matri4 a..nd some 
16 STUDIES OF BASIN-RANGE STRUCTURE 

of the included fragments are calcareous. It exhibits 

many partings with slickensides. All observed slickensides are flexuous (see pI. 4, A), and their dips are 

stee1?er than the slope of the outer face of the breccia, 

which is also the outer face of the range (see pIs. 3, A, 

and 4, B). 

My interpretation of the phenomena is as follows: 

The triangular facets, rising from the base of the range 

with a slope of 29°, are part of the footwall of the 

frontal fault and have lost little by weathering. The 

body of breccia by which they are faced is a shear 

zone within the footwall. The observed slickensided 

surfaces, with relatively steep dips, do not belong to 

the main fault but represent subsidiary yieldings 

within the grinding footwall. 

Beck's Spring locality.-N ear Salt Lake City the 

general trend of the range front is northerly, but just 

north of the city, near Beck's Spring, a broad spur 

projects 3 or 4 miles westward. The spur has a basement of Paleozoic rocks like those in the adjacent part 

of the range, but its superstructure is of Eocene (?) 

conglomerate, and a post-Eocene fault separates it 

from the range. The west face of the spur is steep 

(pI. 8, A) and is met abruptly by the flat plain of the 

valley. In one place a line of cemented alluvium 

clings to the face about 40 feet above the plain, marking a former line of junction of spur face and plain. 

Above the line the slope is approximately that of talus; 

below the line it is steeper, except as modified by 

fresh-fallen debris. (See pI. 5, A.) The steeper part 

is composed of limestone breccia, with slickensides on 

several parallel planes. (See pI. 5, B.) The slickensides are of the plane type, and their dip is 70°. In 

one place, where the base of the cliff is almost free 

from talus, thermal springs rise, the water issuing from 

cavelike openings in the breccia. Back of the breccia 

occur limestones with high dip to the south; and a 

one place the beds bend toward the zone of the slipping 

planes. In notes of these limestones made long ago 

when the possible significance of the feature was not 

appreciated, I find mention also of their brecciation. 

My interpretation of the phenomena follows: The 

steep western face of the spur is a fault scarp'. The 

dip of the fault plane is 70°. The latest slip, between 

the spur and the alluvial plain, amounted to 40 feet. 

Before it occurred there was a period of rest in which 

the slope of the spur face was reduced by erosion. Presumably the entire throw, of about 1,05'00 feet, was 

accomplished in parts, with intervals of no movement, 

and the wasting of the face maintained its slope near 

the angle of rest. After each partial movement a 

strip of fault rock was exposed, as at the present time, 

but the exposure was temporary. 

Ogden Reservoir locality.-Of the rocks exposed in 

the escarpment the one that best resists the agencies 

of erosion is quartzite. For that reason it best preserves the evidences of fault friction. Where a considerable body of it occurs at the base of the escarpment its features are usually significant of faulting. 

A thick quartzite, identified by Blackwelder 15 as of 

Cambrian age, reaches the base at several points north 

FIGURE 6.-Diagrammatic profile section of rock 

surface near Ogden Reservoir, Utah, showing 

the relation of subsidiary Slipping surfaces to 

the footwall of the Wasatch frontal fault 

of Weber Canyon, and at three of these I have examined it. The three localities have so much in common 

that accounts of the local details may advantageously 

be preceded by a .statement of the common features. 

The formation is 1,000 to 1,500 feet thick and is 

~\ 

Quartzite 

Alluvium 

Quartzite 

FIGURE 7.-Ground plan of faults near Ogden Reservoir, Utah, 

showing the relation of a cross fault to the frontal fault of the 

Wasatch Range 

rather coarsely stratified. It rests unconfornlably 

on dark gneisses called Archean. Much of the gneiss 

is hard and tough and comparable with- the quartzite 

10 Blackwelder, Eliot, New light on the geology of the Wasatch Mountains, Utah; 

Cleol. SOC • .t1111ericll Bull., VQ1. 21, pp. 518-527, 1910. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE I 

The shore lioe appears as a cut. t.errace wit.h cliffs a bove. Lower d own the Provo shore li ne is sh own, but less clearly. The shore lines a rc carved o n Lhe west face of the Bear River R a nge. wh ich is a fa ult scarp 

T he rock is quarlziLc. It has a sheet strucLurc parallel to the sloping face, a nd the parLing surfaces bea r slickensides. The face is parL of a facet of the \Vasatch escarpment that. appears at the right in P late 19, A 
U. S. GEOLOGICAL SURVEY 

A. SHEAn ZONE AT MOUT H OF MILL CREEK CANYON, WASAT CH RA NGE, UTA H 

The shear zone makes a wall athwart the canyon, the ouLcr face of the wall being parl of tlw faceted moun tain front., as seen in PJate 11,13. The \l iew shows the inner face of the wall , with s lC<'piy dipping strata abutting against it 

PROFESSIONAL PAPEH 153 P LATE 2 

B. SLICKENSIDES AT BASE OF II ASAT CII ESCA RP.\I El'iT NEAH CIT Y n ESERVOlR, 

OG DEN, UTAIl 

l 'ho rock is Cambrian q uarlzilf', and the exposed face is parl of I he foo l..wall of the f ro nt.a l fn ul l 

oj' the rungc. The general dip of the stra t.a is backward olld to the lef t, but neur the polished 

surface the strata ure bent down toward it 

• 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 3 

A. SIlEAB. ZONE AT MOUTH OF CANYON 

A mass oC brt:ccia, including blocks of strata and divide I irregularly by slickened parlings. This view overl ap~ the onc beneath. A detail is shown in Plate 4, A 

B. IIIGH-DlPPING PALI;;QZOIC STRATA IN NORTH WALL OF CANYON 

The view overlaps the one above ami shows the relation of less disturbed stra la to the rocks of the shear zone. The strata dip down into the canyon wa ll. For views of the opposite canyon wall sec Plate 2 

MILL CREEK CANYON, WASATCH RANGE, UTAH 
U . S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 4 

A detail of the shear zone shown in Plate 3; one of many slickened p artings. The rock is a breccia of quartzite and limestone fragments, and the polish is preserved only 011 Lhe quartzite 

B . SHEAR ZONE AND FACETS 

At t~ e left is the south wall of the ca nyon . The crags in t.he foreground show Lhe shear 7.one of the frontal faull, otherwise exhihited by Plate 2, A. The ev~ n profiles slopi ng toward the righ t a re of facets of Lhe range froot. The cHIl' at the base of the nearer facet is a shore cliff of Lake Bon neville 

FAULT PHE OMENA I N MILL C REEK CANYO , WASATCH RANGE, UTA H 
U. S. GEOLOGICAL SURVEY 

A. GENERAL VIEW 

The exposure is at. lhe base of the fault. sca rp (pI. 8, A) bounding the Cily Creck spur on the west and has heen made by a late movement on the fault. Tllp. fault rock is a limestone breccia 

PROFESSIONAL PAPER 153 PLATE 5 

B. NEAREH VIEW. SHOWING SLICKENSIDES 

EXPOSURE OF FAULT ROCK NORTH OF SALT LAKE CITY, UTAH 
U. S. GEOLOGICAL SUHVEY PROFESSIONAL PAPEH 153 PLATE 6 

A. VIEW FROM THE NORTH 

The gully at the left, follows a slulle outcrop. Cambrian Iirnesl.one appears at. the left of it., and Cambrtan quartzite at Lhe right, bOLh 

dipping eastward. (See section in fig. 9.) The quartzite has been broken over, crushed, and dragged down toward the west. The sbeared rock, a fnulL breccia including large horses, sheaths the mountain face at the right. T he bluff on that face is a shore clifT of Lake Bonneville 

B. VIEW FROM THE SOUTHWEST 

Outcrop of Cambrian Quartzite, dipping backward. Bf"low it are Archean gneisse~. partly masked by lalus. At the left the outcrops arc over placed by the faulL rock described ahove. The allu vium of the foreground is crossed by piedmont scarps 

FAULT PHENOMENA NEAR JUMP-OFF CANYON, WASATCH RANGE, UTAH 
U. S. GEOLOGICAL SURVEY 

A. A PSEUDO-ANTICLINE IN CAMBRIAN QUARTZITE 

Compare with Figure 10 

PROFESSIONAL PAPER 153 PLATE 

B. GENERAL VI I!:W FROM THE NORTH 

The pale rock at the sky line is Cambrian quartzite, dipping eastward. B elow it, at the ri g-ht, are Archean gneisse~. The nearer part of the quartzite is sheathed by sheared rock of the frontal fault" of' the ra nge. For further p-xp lanation sec Figure 1"1 

FAULT PHENOMENA OF WASATCH RANGE NEAR WILLARD. UTAH 
U. S. GEOLOGICAL SURVEY 

A. WESTERN ESCARPMENT OF CITY CREEK_SPUR, WASATCH ... RANGE, UTAH 

H is a Cault scarp. The hanging valley helongs to a topographic development older than the Cault The face has been washed by Lake Bonneville; the higher of the two conspiclious shore lines is the Provo. The fl at plain of the valley, occupied by la ke clays, meets the steep face with litLle 

intervention of alluvial apron 

PROFESSIONAL PAPER 153 PLATE 8 

B . WEST FACE OF WASATCH HANGE NEAR OGDEN, UTAll 

Ogden River, which rises cast of the rangc, here issue.., from its canyon. Outside the caoyon it has 

opened n valley through a dpila previously huilt by it in Lake Bonneville. Piedrnontscarps rtln~ 

paralld to the base of Lhe range frool. The same scarps are shown in Plate 17, B 
, 

WASATCH RANGE, UTAH 17 

in strength, but it weathers more rapidly. Above the 

quartzite is a shale several hundred feet thick, and 

above that a heavy body of limestone. The range is 

composed of a number of large tectonic blocks separated by faults, and the three occurrences of quartzite pertain to three distinct blocks. In all of t;hem the 

attitude of the formation is about the same. The 

formation dips eastward at 30° to 50°, and its strike 

is oblique to the range front. In the southern part of 

each block it crops out as a rugged cliff, overlooking 

a tract of gneiss; in passing northward the outcrop 

approaches the plain and at the same time descends; 

and the outcrop ends where the rock base is bordered 

by the alluvium of the plain. At and near the base 

of the escarpment the formation shows modification 

of various kinds. The line of the rock base is convex 

toward the valley where it passes the quartzite, but 

the convexity is not of large amount. Its existence is 

emphasized by the fact that above the base line the 

quartzite is brought into strong relief by the relatively 

rapid weathering of the formations that inclose it. 

The southern of the three localities is a short distance south of Ogden Canyon, and near it stands a 

reservoir of the municipal water system of the city of 

Ogden. The quartzite there appears at the rock base 

for nearly half a mile, and its surface shows many 

patches of slickensides. Some of these patches are 

plane (see pI. 2, B) and coincide with the outer face 

of the rock, but a greater number curve downward into 

the rock. The general slope of the rock face is 35° to 

45°, and the striation of plane slickensides descends 

this slope without recognized obliquity-that is, the 

strike slip of the fault is very small or zero. Brecciation is not conspicuous to the unaided eye. In the 

sheared zone the reconstruction is so perfect as to 

give the appearance of flexure and flow. At a few 

points the strata are bent downward near the slipping 

surface, becoming thinner as they curve; and in one 

place they are so welded that bedding planes are 

obliterated. Subsidiary slipping surfaces, with slickensides, curve downward from surfaces parallel to the 

fault in the manner indicated at the points marked a 

in Figure 6. The zone in which shearing is shown is 

everywhere thin-at most a few feet in thicknessand there are places where the strata seem to have' 

been merely broken across and ground to smoothness 

without any internal change. No fault rock was seen; 

the observed evidences of shearing all belong to the 

footwall. 

A special feature of .the locality is the offsetting of 

the plane of the frontal fault by a cross fault. The 

relations of the faults are shown in plan in Figure 7, 

where it will be noted that the strike of the frontal 

fault changes abruptly at the junction of the cross 

fault. It is to be noted also that each division of the 

frontal fault meets the plane of the cross fault with a 

curve. The curved surfaces bear the marks of fault 

friction and must have been shaped while the footwall 

and hanging wall were in contact. The cross fault is 

therefore at least as old as the frontal fault. If it is 

older, we have here an example of the control of local 

details of the frontal fault by preexistent structures of 

the terrane--a subject to receive attention in another 

section. If it is not older it was formed at the same 

time, and its occurrence serves to illustrate the general 

fact that faulting is not a solitary phenomenon but is 

necessarily accompanied by other changes. 

The offset of this cross fault affects the entire face 

of the quartzite and also a limestone cliff above. It 

is associated with a shallow groove on the escarpment 

which guides storm water; and the descending water 

has washed out fault rock so as to open a cleft and 

expose parts of the walls of the cross fault. On the 

north wall I found the direction of the slip recorded by 

striae and made a rough measurement of their direction. The south block movec;l downward and westward. In Figure 8 the relations are shown diagrammatically, as projected on the plane of'the cross fault. 

FIGURE S.-Diagram of elements of tho cross 

fault ncar Ogden Reservoir, Utah 

A portion of the north wall, AB OD, is bounded by 

bedding planes, AB and OD, and by the frontal fault, 

BO. The corresponding portion of the south wall is 

EFGH. J 1 on the south wall corresponds to J on 

the north wall. The slip is JJ1 ,the dip slip J K, and 

the strike slip KJ1• Although the strike component 

of the displacement, as referred. to the northern block, 

is westward, the offset, LJ1, is eastward. The amount 

of offset, roughly measured, is 90 feet; the strike slip 

is a little greater, an'd the dip slip about twice as great. 

The offset in the limestone face, seen only at a distance, 

seemed to be the same as that in the quartzite, indicating that the fault movement was without rotation. 

Jump-off ZocaZity.-The second of the quartzite 

bodies is crossed by Jump-off Canyon near the place 

where it begins to descend and reaches the rock base 

about 2 miles south of North Ogden Canyon. Plate 

6, B, gives a view of its western face from the southwest, and Plate 6, A, a view of its northern end from 

the north. The section in Figure 9 passes through . 

the apex of the quartzite as represented in Plate 6, A. 

A quantity of quartzite has been torn from the fractured edge of the formation in the footwall and dragged 
·18 STUDIES OF BASIN-RANGE STRUCTURE 

down so as to rest in part against the fractured face 

of the gneiss. The fragmental mass contains large 

blocks that might be called horses, but their boundaries 

are indefinite. Though they retain traces of bedding 

they· are traversed, in common with the rest of the 

mass, by partings, ascribed to shearing, which are 

approximately parallel among themselves and are 

thought to be parallel to the plane of the fault. The 

partings undulate after the manner of flexuous slickensides and are fluted in the direction of their dip, but 

no striae were found on them. As all the exposures 

examined have been washed by the waves of Lake 

Bonneville, it is thought that striae may have been 

ground away. From these broad parting surfaces small 

subsidiary partings curve downward into the rock. 

w. 

FIGURE 9.-Section of west front of Wasatch Range north of Jump-off 

Canyon, Utah 

At a short distance south of the line of section the 

facing of dragged rock is connected with the upper 

part of the quartzite bed by a curve, giving the appearance, as seen from the plain, of continuity. This 

feature will be referred to again in connection with 

an allied feature seen near Willard. 

Still farther south the facing of disturbed rock comes 

abruptly to an end, terminating in' a scarp which faces 

southward (seen at left of center in pI. 6, B); and 

beyond that scarp appears the normal outcrop of the 

eastward-dipping quartzite, with its basement of gneiss. 

In this locality the footwall is not exposed in such 

a way as to afford a direct measurement of the dip of 

the fault. From the partings ascribed to shearing 

the dip is estimated at 33°. The entire visible body 

of brecciated and sheared rock is thought to belong 

to the footwall. 

Willard locality.-The northern of the three localities is near the town of Willard, and the quartzite 

outcrop reaches the rock base a little north of Willard 

Creek canyon. Here also fragments have been torn 

from the quartzite body and dragged down in the direction of the fault movement, and among the fragments 

are blocks that would be called horses if encountered 

in a mine. In at least one of the larger blocks a structure has been developed parallel to the fault plane. 

The finer material has the character of breccia. There 

is room for doubt as to the position of the footwall. 

The entire body of dislocated material may belong to 

the uplifted block, and if so the footwall surface has 

been effaced by weathering and erosion; or part of 

the dislocated material may properly be called fault 

rock, and if so the footwall surface has escaped recognition. The first-mentioned alternative is regarded 

as the more probable, chiefly because of the coarseness of the material. Where fault rock was definitely 

recognized at other points along the mountain base 

it was found to have been ground much finer. 

No direct measurement of the dip of the fault 

could be made. Indirect measurements gave angles 

ranging from 33° to 37°. 

Conditions near the upper edge of the quartzite 

outcrop are complicated by a feature that belongs to 

the earlier diastrophism. The plane of the Willard 

overthrust, discovered by Blackwelder,16 here touches 

the quartzite, and it is probable that the quartzite 

body had been locally modified before the inception 

of the frontal fault. For that reason there is doubt 

as to the interpretation of the pseudo-anticline 

described in the next paragraph. 

Beyond the end of the continuous outcrop of quartzite a shallow ravine reveals a small patch of the same 

rock. The relations of the patch to the greater body 

are concealed by alluvium and beach deposits. There 

is an apparent pitching anticline, the axis of which 

makes a considerable angle with the strike of the 

neighboring quartzite. Plate 7, A, gives a view from 

below, the camera having been directed up the slope. 

The diagram in Figure 10 is made from a notebook 

sketch. At a and b are planes of bedding. At care 

partings parallel to the outer surface and ascribed to 

shearing. At b shearing and bedding planes intersect at an angle. No striae were seen; the surfaces 

are smooth but have the habit of surfaces ground by 

beach sand. At many points on the arch are minor 

partings of moderate extent, which enter the rock 

FIGURE lO.-Profile section of pseudo-anticline 

near Willard, Utah 

obliquely, and these all dip to the right. They show 

that the direction. of the shearing force was from left 

to right. This simulation of an a.nticlinal fold by 

the association of bedding with shearing structure 

suggests that the arch observed near Jump-off Canyon may not in fact be that which it seems, a fold of 

strata. 

In Figure 11, a diagram to explain Plate 7,. B, a 

heavy line marks tentatively the outcrop of the 

Willard overthrust. The overthrust dips toward the 

left, and Algonkian formations (A) at this point overlap the Cambrian quartzite (Q). The distant outcrop 

of the quartzite shows a high dip, the nearer a low 

dip. The different attitude of the nearer outcrop may 

16 l31ackwelder, Eliot, op. cit., pp. 534-536. 
WASATCH RANGE, UTAH 19 

have been acquired in connection with the formation 

of the overthrust; and it is also possible that the 

upper part of the nearer quartzite is a separate body, 

the overthrust plane, or an accessory thrust plane, 

passing below it. The sheet of fault rock, exposed at 

F, also underlies the detrital slope between and above 

the old shore lines, Band P. 

North Ogden fire clay.-A few rods north of North 

Ogden Canyon a body of fault gouge is worked as fire 

clay by means of an open pit. About 1~ miles 

farther north is an older opening in similar material. 

Between the two openings are indications of a linear 

outcrop, continuous for nearly half a nlile. All the 

occurrences are' on faces of scarps in alluvium that 

have the habit of pied~ont scarps. Their line traverses the alluvial apron of the range. 

The southern opening reveals no boundary of the 

formation but shows a horizontal extent in all directions of more than 50 feet. The northern opening 

FIGURE n.-Diagram to explain Plate 7, B. G, Archean 

gneiss; A, Algonkian; Q, Cambrian quartzite; L, CambrIan limostone; F, fault rock; B, Bonneville shoro line; 

P, Provo shore line; heavy line between A and Q, outcrop 

of Willard overthrust 

shows a short contact with alluvium on the side nearer 

the mountain, the surface of contact dipping toward 

the mountain. Not far away is a bench tentatively 

ascribed to a landslide, and it may be that the gouge 

at this opening has been affected by such a movement. 

The indication of linear outcrop is a whitish band, 

corresponding in color to the gouge, which appears on 

a steep alluvial slope where the slope is made still 

steeper by recent faulting. The place was not visited. 

The relations of the linear and the southern outcrops 

to the rock base are accordant with the hypothesis 

that the gouge is a fault rock of the frontal fault, and 

the hypothesis finds further support in the occurrence 

on the mountain face of quartzite, which is the material of the gouge. 

The material is yellowish white and closely resembles 

that found at the mouth of Rock Canyon. (See p. 14.) 

It consists of angular fragments of quartzite, without 

cement. In a sample sorted by sieves, one-half by 

weight was found to have diameters under 0.5 millimeter and one-eighth under 0.1 millimeter. After 

wetting and drying it coheres, but the cohesion is 

feeble. 

DISCUSSION 

Visible discontinuity and offsetting of bedded rocks 

on the two sides of an intersecting plane is direct 

evidence of faulting. In a massive rock such evidence 

is usually not available, and the geologist depends 

on that which is less direct. If he finds a surface 

of separation and on that surface slickensides he infers 

faulting, and he also infers faulting if he finds a massive rock traversed by a shear zone. In all occurrences that involve two adjacent terranes faulting 

is inferred without question, either from visible dislocation, or from a surface of separation with slickensides, or from the intervention of a shear zone. The 

evidence of a fault may include all the items mentioned, 

with duplication of some of them. There may be a 

shear zone bounded by slickensided walls; that shear 

zone may be bordered by other zones of shearing within 

the wall rocks; and the wall rocks may be so constituted 

that dislocation is directly demonstrable. 

Along the western base of the Wasatch Range 

the evidence is less full. In all the localities described a shear zone is found. In some of them it 

is bounded on the outer side by a definite surface 

(wall) with slickensides. In some a second shear 

zone (fault rock) occurs outside the wall. A second 

w~ll surface and a second wall rock are not seen, 

and dislocation is not directly observed. Never_ 

theless the evidence seems to me adequate. The 

phenomena are all explicable on the hypothesis 

that they were 'produced by faulting and that the 

western fault block is concealed by valley deposits. 

So far as I lmow, there is no alternative hypothesis 

to be discussed. 

The shear zones contain many slipping surfaces of 

small area which are oblique to the principal plane of 

faulting. Without exception they indicate that the 

fault is normal, the hanging wall having descended. 

Some of the shear zones contain deformations of 

the nature of flow. Strata of quartzite have been 

bent and stretched or have been welded together. 

The process of flow probably involved crushing 

and reunion, but the preservation of continuity 

while the forms of strong rocks were changed implies such coercion as is given by a heavy load of 

superjacent rock. The deformations were produced 

at a considera'ble depth beneath the surface. In 

some of the gouges, on the other hand, finely divided 

quartzite has not been reunited, nor even bound 

together by a cement; and the condition of these 

indicates formation at small depth. Despite the 

great contrast between the two groups of facts they 

are really harmonious-under the hypo thesis that 

faulting on this plane created the entire escarpment. 

If the faulting began when the tops of the valley 

block and mountain block were at about the same 

level, that part of the footwall which is now visible 
20 STUDIES OF BASIN-RANGE STRUCTURE 

at the base of the escarpment lay initially at a depth 

beneath the surface roughly equivalent to the present 

height of the escarpment plus the amount of degradation of the mountain block, and the frictional 

Collinstono 

M as ,illIl-~ Box Elder Pk a enCC ~M;' 

Honeyvilleoc 

Ben Lomond 

o 

PleaS'8ntVlew(,Q:; 

North Ogden.o 

SALT LAKE CITY~ 

oLebi 

American:Forko 

TwinPk 

It,} ~ Clayton PK 

Provo Pk 

fI 

o 5 10 20 Miles ~I ~I~I~I~I-L'~~I ~I~I-LI ____________ ~I 

FIGURE 12.-Map of frontal fault of Wasatch Range, Utah 

effects in that part of the footwalf were conditioned 

by the corresponding pressure. As the faulting 

progressed the pressure on that part of the footwall 

gradually diminished, with the result that deform ation within the wall rock ceased after a time, and 

the products of the earlier high-pressure dragging 

were thus fixed for continuous preservation. But 

between the fault walls friction continued, and the 

fault rock was ground finer and finer. That part 

of the fault rock near what is now the base of the 

escarpment was worked over, with gradually diminishing pressure, until finally it was freed from contact 

with the hanging wall, and when that stage was 

reached it had been reduced to the gritty powder 

of the gouges. 

OSlO ISMiles ~I~I~I-LI ~I~I ____ ~~I ____ ~I 

FIGURE 13.--Map of that portion of the frontal 

fault of the Wasatch Range north of Weber 

. Canyon, Utah 

OUTLINE OF THE FAULT 

In characterizing ranges that have a bold front due 

to faulting I wrote in 1890: "The line separating the 

rock of the mountain from the alluvium of the valley is simple and direct. "17 The statement is perhaps 

defensible because the context compares such a line 

with th~ corresponding line on the back slope of a 

range consisting of a tilted block; but it is fair to say 

that my conception of the flexuosity which may 

affect fault outlines has been materially enlarged by 

17 GUbert, G. K., U. S. Geol. Survey Mon. 1, p. 341, 1890. 
\ 

WASATCH RANGlD, UTAH 21 

more recent studies of the Wasatch front. As the 

outlines drawn in Figures 12 and 13 are based in part 

on reconnaissance maps and in part on rough traverses, 

they have no claim to accuracy, but the general impression they convey is not misleading. The line of 

the fault is crooked. It not only curves through considerable arcs but in two places turns sharply at 

right angles, and in three other places its course runs 

for Iniles athwart the general direction of the fault as 

a whole. 

Some of the deflections, but not all, are evidently 

associated with preexistent structural features. The 

outward convexity of the outline in' passing certain quartzite bodies has already been mentioned. 

One of the greatest deviations occurs in passing 

around the granite body north of Alpine. That 

body, the outcrop of which is mapped by Emmons as 

oval, with a longer (northeasterly) axis of 15 miles 

and a shorter axis of 6 miles, is exposed through a 

vertical range of 6,000 feet, and its base is not seen. 

One-fourth of its area proj ects beyond the general 

FIOURE H.-Ground plan of Wasatch frontal fault at Taylor 

Canyon, Utah 

line of the range front in its vicinity. It is easy to 

surmise that these convexities were induced by the 

ability of the quartzite to resist the deformation and 

abrasion that affected weaker formations and by the 

ability of the huge and strong granitic mass to resist 

the stresses that initiated the fault fracture. 

The small jog in the line near the Ogden Reservoir 

(p. 16) is definitely connected with ,a cross fault that 

was not Inade after the frontal fault and may have 

been made before. A mile farther south is an angular 

notch that is probably connected with a fault belonging to the internal structure of the range. At 

the apex of the notch (see fig. 14) is Taylor Oanyon, 

and the notch is partly occupied by the alluvial fan 

of Taylor Oreek. These relations suggest that the 

notch is part of the canyon mouth and was eroded 

from the mountain block by the creek, but there is 

no merging of the canyon with the notch. The canyon 

does not flare but holds its V form to the rock base 

and there ends ,abruptly. Furthermore, the line 

of the fault is outlined by a fresh post-Bonneville 

piedmont scarp, a feature whose significance will 

be discussed in another section. The scarp testifies 

to local depth of alluvium, and its presence at the 

head of the fan (see pI. 9, B) implies a steeper descent 

of the suballuvial rock slope than would accord with 

the grade of the canyon bed. In the south wall of 

the canyon there is a discordance of dips indicative of 

a dislocation of some sort, and although I observed 

the dips only from a distance I regard it as probable 

that an ancient fault, with high dip, has the course 

indicated by the broken line in Figure 14 and coincides in direction with the northeast face of the notch in 

the escarpment. If such a fault existed before the 

starting of the frontal fault it may have determined 

the notch by giving to a wedge of rock a weaker 

attachment to the footwall of the frontal fault than 

to the hanging wall. 

For other deflections of the fault line I have no 

specific explanations to suggest. Doubtless a fuller 

knowledge of the internal structure of the range 

would lead to other suggestions, but it is probable 

that after all the plausible relations to structure 

, had been di~covered a large share of the deflections 

would remain unexplained because the structural 

features to which they are related are not now visible. 

The conditions under which an extensive fault occurs 

are almost necessarily complex. Whatever the primary force, and however simple, it loses simplicity in 

transmission through a heterogeneous crust. In the 

actual field of the fault weak rocks seek adjustment by 

flow, and by partial yielding they not only increase the 

strain in hard rocks but modify its distribution and diversify its direction. For these reasons the surface of 

eventual fracture is neither plane nor of simple curvature. As soon as movement takes place the walls cease 

to be fitted one to the other. A prominence of one wall 

,leaves the companion hollow and becomes opposed to 

an incompatible surface. Adjustments are then necessary to preserve contact. If the prominence is of 

strong rock strongly set, it may plow a furrow in the 

opposite wall; if of weak rock, it may 'be split off or 

ground away. A prominence of strong rock with a 

backing of weak rock ''inay be forced back into its wall, 

adjustment being effected chiefly by the flow of weak 

rock. After much movement the walls will become 

fluted in the direction of the slip; between the walls 

will occur products of attrition, and within the wall 

rock will be tracts affected by the internal changes that 

have aided in the adjustment. 

With such a conception of the immediate mechanism 

of a great fault, it is easy to understand that details of 

configuration may depend on elements of structure not 

revealed at the surface. The huge body of granite 

that determined the Wasatch salient near Alpine may 

be assumed to have remained with the footwall, because 

the major part of the bulk lay on that side of the generalline of the fault. Had its major part lain in the 

hanging wall, it might all have remained with that 

wall and thereby have deflected thA fault line toward 

the east, creating a reentrant; and if so, the factor 
22 STUDIES OF BASIN-RANGE STRUCTURE 

determining the reen tran t would be concealed along 

with the hanging wall under the valley deposits. 

Where level formations bury deeply a foundation of 

complex structure and a long fault is afterward formed, 

the ground plan of the fault may be determined wholly 

by features of the foundation and thus involve complexities out of harmony with the character of the 

formations in which the relief is expressed. 

From present knowledge it is not easy to determine 

whether the Wasatch fault, with its crooked trace, is 

exceptional or whether it represents the type of major 

faults in the Great Basin. No faults of similar extent 

in the region have yet been mapped in detail. 

Dutton's map of displacements in the plateau province 18 includes a number of long faults, and all the 

lines drawn swing in simple curves, but the lines 

were based on reconnaissance studies and plotted on 

a reconnaissance map. An outline of the Wasatch 

fault that I drew in 1890 is nearly as simple in its 

curvature.19 . 

Whether the Wasatch fault is exceptional or typical, 

in its contour, it is evident that great simplicity of 

basal outline is not an essential characteristic of 

faulted range fronts. 

On the other hand, the phrase "simple and direct" 

may properly be used in a relative sense when basal 

outlines of faulted fronts are compared with rock bases 

shaped chiefly by erosion. The erosive outline, as 

will later be shown, is greatly influenced by the 

arrangement of drainage lines and by the distribution 

of strong and weak rocks; the fault-block outline is 

independent of drainage lines and its adjustment to 

rock texture is partial and local; and these differences 

serve to make the erosive outline comparatively tortuous and the fault outline comparatively direct. 

DIP OF THE FAULT 

At the Warm Spring locality the dip of the fault 

plane is 70°, but the locality is exceptional. The 

fault there seen is not, properly speaking, the frontal 

fault of the range but is a SUbsidiary displacement 

outlining an associated but distinct crustal block. An 

measurements of dip on the frontal fault proper give 

lower angles. The records of dip already cited are 

as follows: 

At Rock Canyon ________________________ 35° 

At Fort Canyon _________________________ 29° 

Near Draper ____________________________ 35° 

At Mill Creek Canyon ___________________ 29°· 

At Ogden Reservoir _________________ 35°-45° 

Near Jump-off Canyon ___________________ 33° 

Near Willard~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 33°-37° 

A few other observations are of similar tenor, 35° 

being noted at the mouth of Ogden Canyon and 30° 

near Provo. Lower dips occur about the Lone Peak 

18 Dutton, C. E., Tertiary history of the Grand Canyon district: U. S. Geol. 

Survey Mon. 2, atlas, sheet 3, 1882. 

10 Gilbert, G. K., U. S. Geol. Survey Mon. 1, pl. 45, 1890. 

salient. The measurement at Fort Canyon, 29°, was 

on the southern face of the salient, and that near 

Draper, 35°, on the western face. Between the two 

places lies the rounded apex of the salient, and the 

dips diminish toward the apex, where the angle 

indicated by the rock profile is 20°. Traces of fault 

friction were not observed at the apex, but there is 

much evidence that the original form of the granite 

body is well represented by the present contours and 

profiles near the rock base. From the apex of the 

salient to a high crest in the direction of Lone Peak 

the granite presents a blunt edge that separates the 

southerly and westerly faces. Those faces are relatively steep, but the profile of the edge itself is gentle. 

It is also convexly curved, from 10° in its higher part 

to 20° at the rock base. It would appear that in the 

process of faulting this edge cleaved the descending 

block, as the unyielding granite prong plowed a furrow 

through the weaker rocks of the hanging wall. As 

thus conceived the local dip of 20° has an exceptional 

local cause. If the local profile of the granite should 

be explored below the surface it would probably be 

found to steepen. 

With the omission of the observation on the salient 

the measurements of dip give an average of 33:4°. 

Consideration of the throw of the' fault, which might 

logically follow consideration of the dip, is deferred to 

page 50, because it involves data to be presented in the 

sections that immediately follow. 

FAULT-BLOCK SPURS 

CITY CREEK SPUR 

To the general fact that the fault front of the range 

is bordered by valleys and valley deposits there are 

exceptions. A number of spurs that are associated 

with the range but are not part of it invade the valleys, 

and these will now be described, beginning with one 

just north of Salt Lake City. Topographically the 

City Creek spur is a member of the range. Some of 

its higher slopes are continuous with slopes of the 

range, and City Creek, which rises in the range and 

flows to Jordan Valley, crosses the spur obliquely on 

its way. Structurally the spur is distinct, being 

separated from the range by a fault, which is continuous with the frontal fault of the range. The spur 

is also structurally distinct from the valley, being 

bounded on the north, west, and south by a curving 

fault. It consists of a tectonic block that stands 

lower than the adjacent block of the range and higher 

than the adj acen t block or blocks of the valley. 

rhe spur has a length, parallel to the range, of 6 

miles, and a width, measured from the base line of 

the range, of 3 to 4 miles. At the west, where its 

steep face overlooks the flat delta built by Jordan 

River in Great Salt Lake, its height is about 1,200 

feet, and there is a gradual rise toward the range. 

The upland is hilly and may be described as a disI 
WASA~CH RANGE. UTAH 23 

sected plateau. .It is divided unequally by the incised 

valley of City Creek, the northern division being the 

larger. 

In the adj acent part of the range the rocks dip at high 

angles toward the south and southeast. Just south of 

the spur lies the axis of a great syncline, which crosses 

the range from west to east, and along the axis are 

strata of Jurassic and Triassic age. Opposite the 

north end of the spur are metamorphic rocks referred 

by ]~mmons to the Archean. The interval is occupied by Paleozoic formations that dip away from the 

Archean and toward the synclinal axis. The Paleozoic 

rocks include lnuch limestone and a smaller amount of 

sandstone and quartzite. 

The upland of the spur is occupied by a Tertiary 

fOl'lnation, which the Fortieth Parallel atlas correlates with an ]~ocene formatioll on the eastern flank 

of the range. This correlation is to be regarded as 

tentative, for Enlnlons 20 in his text does not indicate it, but I know of no facts to contravene it. 

The formation consists in large part of coarse conglomerate but includes also finer beds. The pebbles 

and boulders are chiefly of sandstone and limestone 

W. E. f"'" - - - - - - - - - - - - - - - - - - -. --- - - - - - -- - - ~ - - - - - - - -- : ~ra~~ : City Creck spur : Range: 

: : I 

, 

FlounE IS.-Dlagrammatlc section of City Creek spur of Wasatch 

Han go, Utah. A, Alluvium and lake beds of Jordan·Salt Lake Valloy; '1', 'l'ertlary conglomerate and sandstone; P, pre-Cretaceous 

rooks, mainly Paleozolo 

and show the imperfect rounding characteristic 

of alluvial fans. The cement is chiefly calcareous. 

In the western escarpment of the spur the conglomerates are seen at the top, and below thenl lie Paleozoic rocks that dip steeply toward the southeast. 

The Paleozoic belt, about 3 miles long, includes 

a large stratigraphic range. Although no contacts 

were observed, it is evident that the conglomerate 

rests unconfol'lnably on tilted and eroded Paleozoic 

beds. Presulnably the t~ctonic block constituting 

the spur is COlllposed largely of olaer rocks and bears 

the Tertiary beds as a capping formation. (See 

fig. 15.) 

The Tertiary formation has suffered much disturbance. As it yields rather easily to weathering 

n,gencies the full determination of its' structure would 

be difficult, but nearly all observed outcrops show 

notrtble dips, which reach 50° or 60°. In one place 

a broad syncline was noted, with northerly axis. 

In another place the repetition of a particular 

sequence of beds seemed best explained by assuming the presence of several faults. In another place 

the hypothesis of a graben seenled best to explain 

f1n occurrence of conglomerate between hills of Paleozoic limestone. The direction of dip most frequently 

to Emmons, S. F., U. S. Gaol. Expl. 40th Par. Rept., vol. 2, pp. 374-376, 1877. 

recorded is eastward, and only that direction was 

noted in the place where faulting was inferred. The 

disturbance of the Tertiary cap implies disturbance 

of the older rocks on which it rests. So the Paleozoic 

beds were dislocated both before and after the time 

represented by the conglomerate. 

The statement above that the spur is separated 

from the range by a fault continuous with the frontal 

fault of the range was made with a mental reservation, for the eyidence is not complete. The contact was not seen, its position being at all points 

masked by waste. The best estimate of the attitude of the contact plane assigns a westward slope 

of 30°. Tertiary beds that not far from the contact 

dip toward it at 30° were observed to have less 

dip as they approached the contact. On the other 

side of the contact and close to it were seen limestone strata nearly parallel with the contact plane, 

their strike in this position being nearly at right 

angles to the strike of the near-by body of similar 

limestone. These features accord with the hypothesis 

of It fault, accompanied by dragging of the strata 

of both walls,' but they' are not demonstrative, 

because the structure on both sides is complex. I 

was told by the late Mr. J. E. Clayton, geologist and 

mining engineer, that in inspecting a prospector's 

tunnel near the north end of the spur he had observed a normal fault approximately on the plane 

of the contact, but my record of his statement contains no details. My acceptance of this meager 

evidence has been largely determined by the fact that 

two other spurs, in some respects similar to this one, 

are demonstrably separated from the range by 

faults. 

The evidence of faulting on the outer periphery 

of the spur is more satisfactory. Slickensides, breccia, and deflected strata have already been described 

in the account 'of the Beck's Spring locality (p. 16). 

Olosely associated with them is a piedmont scarp, 

which follows or parallels the rock base on the w~stern and northern sides, just as such searps parallel 

the rock base of the range through the greater part 

of its length. A scarp that is similar but less fresh 

was seen near the southern base. A part of the 

western faee that is composed chiefly of limestone 

stands as a steep wall (see pI. 8, A) and is almost 

free from cliff waste at its base. The waste has 

doubtless been buried by deposits of Great Salt Lake 

and the Jordan delta, but such deposition is so slow 

in comparison with the wasting of a cliff that the 

burial is hard to explain without the assumption 

of local subsidence. At the top of the cliff are 

hanging valleys (pI. 8, A), which are. easily understood if the steep face is a fault scarp but otherwise 

hard to explain. 

The highest part of the spur is a graded plain that 

slopes' away from the range. The plain is built of 

coarse alluvium, and the proportion of limestone 
24 STUDIES OF BASIN-RANGE STRUCTURE 

debris in this alluvium is greater than was seen in 

the Tertiary conglomerate. Neighboring outcrops 

of conglomerate show dips that do not accord with 

the slope of the plain, and it is inferred that the 

alluvium rests unconformably on the conglomerate. 

The alluvium is believed .to be a remnant of a fan 

that has its apex in the ·mountain canyon of Oity 

Oreek and to record an epoch in which the base-level 

for Oity Oreek was 1,500 or 2,000 feet higher than 

at present. The alluvial fan was part of the alluvial 

apron of the Wasatch Range at a time when there 

was less difference in altitude between the range and 

the flanking valley than there is now. It marks a 

stage in the development of the range, and during 

that stage the Oity Oreek spur probably did not 

FIGURE l6.-Graded ridges near City Creek spur, Wasatch Range, 

Utah. (After s~etch by author) 

exist. It is possible that some remnants of graded 

plains observed high on the range belong to the 

same stage, but more possible that they are of earlier 

origin. 

Below the summit plain of the spur are valleys 

of gentle slope and mature development that mark 

an early stage in the dissection of the upland. To 

this stage belong the hanging valleys of th~ western 

scarp of the spur. They pertain to a base-level 

somewhat lower than that of the summit plain, 

and while they were forming the spur must have 

been in existence. They mark a stage in the development of the fault that separates the spur block 

from the valley block. 

They are correlated tentatively with some wellgraded profiles (fig. 16) observed on intercanyon 

ridges of the range just south of the spur, and also 

with a dissected terrace (fig. 17) in the neighboring 

canyon of Red Butte Oreek. 

If there is warrant for the suggested correlation, 

the range and spur have similar histories with reference to their base-level of erosion, which is the valley 

plain, and there has probably been no' differential 

movement between the range block and the spur 

'block since the separation of the spur block from 

the valley block. 

Arranged in order of time, the changes recorded 

in and near the spur indicate the following elements 

of local history: 

1. A land surface made up of Jurassic and preJurassic rocks, which had been folded and reduced 

by erosion, had such relief in early Tertiary time 

that its lower slopes received alluvial deposits, mainly 

coarse. 

2 and 3. The Wasatch Range w.as differentiated 

from a valley tract west of it by the initiation of a 

normal fault-now the frontal fault. The valley 

block was completely shattered on a relatively small 

scale. The shattering of the valley block may 

have preceded or accompanied its separation from the 

range block. 

4 .. In.an epoch of orogenic rest the slope from mountain to valley was graded, with removal of early 

Tertiary deposits from the range and partial burial 

of those deposits in the valley. 

5. Renewed up faulting of the range occurred and 

inception of the outer fault of the spur. In this 

and later movements the relation of the spur block 

to the range block was not changed, but they were 

lifted together with reference to the valley block. 

The spur. block suffered no internal disturbance. 

Oity Oreek, having previously contributed to the 

work of grading by building an alluvial fan at the 

range margin, now incised a channel in the fan, and 

its course was thus superimposed on the structural 

features of the spur. 

6. In another epoch of rest the drainage of the 

spur developed mature minor valleys, and some 

neighboring canyons of the range were broadened. 

7. Renewed faulting, on the same lines as in (5), 

caused streams of range and spur to incise their 

FIGURE l7.-Dissected terrace along Red Butte Canyon, Wasatch 

Range, Utah. (After sketch by author) 

channel ways, leaving the valley floors of (6) as terraces and hanging valleys. There was concomitant 

partial grading of fault scarps. . 

8. The Salt Lake Valley and Jordan Valley were 

flooded by the Quaternary Lake Bonneville, with 

reworking of alluvial slopes and fault scarps, up to 

a height of 1,000 feet, by waves. 

9. The latest fault movement, a continuance of (7), 

disturbed the alluvial and lacustral slopes and created 

low scarps in them'. 

PLEASANT VIEW SPUR 

Between the villages of North Ogden and Willard, 

35 miles north of the Oity Oreek spur, is a spur of 

somewhat smaller area and of much less height. A 

little creek from the range crosses it, and on the banks 

of the creek stands a hamlet once known as Pole 

Patch but now called Pleasant View. The range 

front, with its fault line, is here inflected., the general 
U . S. GEOLOGICAL SUR VEY PROFESSIONAL PAPER 153 PLATE 9 

A. PLEASANT VIEW SPUR AND THE WASATCH ESCARPMENT, WASATCH RANGE, UTAH 

The view was taken from a stalion on the spur and shows the contrast be tween its plain Lop and the bold face of the range 

B . MOUTH OF TAYLOR CANYON, WASATCH RANGE, UTAH 

In the foreground is an alluvial fan built hy Taylor Creek in an embayment of tbe range front. (See fi g. 14 .. ) The fan is crossed by a fresh piedmont scarp, 40 feet high. The present channel of Lhe creek is to the right of the searl? 
U. S. GEOLOGICAL SUHVEY PHOFESSIONAL PAPEH 153 PLATE 10 

A. SADDLE BETWEEN THE SALIENT AND THE TRAVERSI~ SPUR 

The view is westward from the head of Fort Canyon. At. the right is the granite of the salient, with structure ascribed to shearing. A fault separates it from the rocks of the spur, seen at the left 

B. ANCIENT CHANNEL OF CORNER CREEK 

Corner Creek, following t.he groin belweeu the salient aod the Traverse spur, sinks its channel into the gran.ite of the salient. As the bod y 

of Lhe spur retreats down the granite slope successive creek channels arc slranded. The view is 00 the lowest of the stranded channels shown in Figurcs 22 and 23 

LONE PEAK SALIENT OF WASATCH RANGE, UTAH 
U. S. GEOLOGICAL SURVEY PROFESSIONAl. PAPER 153 P LATE 11 

At the right is the Traverse spur ; at the left the faccl,cd slope of the Lone Peak salient of the range. Spur and sali ent are terraced by t.he Bonneville shore lino. In Lhe foregrou nd is a delta plain built. by the creek at the Provo stage of Lake Bonne ville. A piedmont scarp crosses t he d elta pl a in to the hau k of the creek. (See also fi g. 29) 

B . SCARP OPPOSITE HONEYVILLE SPUR 

The spur is separated from the base of Lho range by a belt of grabens. with undrained hollows. The v iew shows grabens and the high scarp beyond them 

FEATURES AT THE HE ADS OF spuns OF THE WASATCH RANGE, UTA H 
U. S. GEOLOGI AL SURVEY PROFESSIOK AL PAPER 153 PLATE 12 

A. LANDSLIDES AT MADSEN spun 

The view is westward along the northern face of the spur. The hummocks at the right and the table beyond them have slumped from the 

higher table at the loft 

A piedmont scarp passes below its base and is strongly marked Oll an alluvia l fan at the left. The level terrace above was carved out by the waves of Lake Booneville at the Provo stage. P late 18 gives details of the piedmont scarp 

FEATunES OF SPURS OF WASATCH RANGE, UTAH 
WASATCH RA~GE, UTAR 

northerly trend being interrupted for a few miJes by a 

northwesterly trend. As shown by Figure 18, the 

spur adjoins the face with northwesterly trend and 

has its longer dimension in the Sfune direction. As 

shown by the profile in Figure 19, the spur is much 

lower than the range. Its higher parts rise 200 to 300 

feet above the Bonneville shore line, 

which is here nearly 1,000 feet above GRJEAT 

the level of Great Salt Lake. ExSALT 

LAKE 

LA K E 

waters frOlll intervening steep facets of the front. 

The older alluvium had a like origin but is no longer 

traversed by waters from the range. One tract of 

older alluvium, marked A in Figure 18, retains the 

slopes of deposition but stands a little above the 

present channels, which dissect it. Another tract, 

, 

$ 

Ben Lomo~ 

-<l ~/Will~peak) 

~/ ').. 

~ I 

v/( C o;r- H 

"'c:V-? 

posures of bedrock occur only on 

the outer or southwestern half of 

the spur and nre there discontinuous, the surface consisting largely 

of local fragmental material, sorted 

and rearranged by lake waves. The 

conspicuous rocks are quartzite and 

linlestone. To casual observation 

the structure appears c(nnplex, and 

I did not attempt to decipher it. 

Both Hague 21 and Blackwelder 22 

speak of the rocks as lnuch disturbed, and both correlate thenl 

with a quartzite and tl. linlestone 

that occur high on the face of the 

range. Hague's map indicates an 

outer belt of quartzite and an inner 

of limestone, and Blackwelder's 

shows the same sequence doubled 

P LA IN 

with a reverse fault between. 

Between the tract characterized 

by outcrops and the base of the 

range is a bel t more th an a mile 

wide occupied wholly by alluviuln. 

.(i) 

In the portion of the belt that is ~ ~ ~ i ~ Miles 

below the level of Lake Bonneville FIGURE lS.-Map of Pleasant View spur, Wasatch Range, Utah. A and B, Tracts of alluvium 

the alluvium has been rearranged by the waves; in marked B in Figure 18, is avoided by the present 

the portion above wave action it is possible to make drainage of the range, which passes around it, u,nd 

a distinction between younger and older alluviums. has lost all semblance of the graded slopes that doubtl"he younger alluvium is the modern detrital apron of less once characterized it. Its surface is corrugated 

in a system of subparallel 

~:.-. - - ., - - - - - - - -, - "I - - - ,-- - - -.- - - - - ~ - - - - _N_~. ridges and hollows, with 

I I I I Ben Lomond I 

Valley I Outcrop of I : Older I l Wasatch (Willard Peak) I a relief of 25 to 75 feet., 

plain I Paleozoic rocks I 'alluvium I I escarpment. and the arrangement' of , I L. E , I L. E I ':'. 

~ : tl ! : tl ;<~0~j lit :.e~~c!~e~p!r~:~~~~ j

': I ~m I I ~ IG I ::.:.~~,:::<,;.':;.,.., I I "':.-:<~~:: ...... The hollows, although I I I .... 

~--- troughlike and long, are 

not abandoned watercourses:' their forms' are 

not erosional, their genFIGURE 19.-Section or Pleasant View spur and part of Wasatch Range, Utah, along line 8-8' of Figure 18. Qal, Alluvium; £q, eral direction is no t that 

Cambrian quartzite; PR, Archean gneiss of the original waterthe range, with characteristic graded slopes, down 

w1;lich flow small streams from the canyons and storm 

1\ Hague, Arnold, U. S. Oeol. Expl. 40th ·Par. Rept .. vol. 2, p. 402,1877. 

n Blackwelder, Eliot, Oeo1. Soc. America Bull., vol. 21, p. 539, 1910. 

62436-28--3 

made slopes, and among them are several undrained 

basins. The corrugation has been given to the tract by 

sonle sort of differential lnovement of the alluviuln. 

As its origin is not of evident inlportance in the present 
26 . STUDIES OF BASIN-RANGE STRUCTURE 

connection it is not considered here but is taken up in 

a section that is devoted to disturbances of the piedmont slopes. 

The adjoining face of the range (see fig. 19) has at 

its base a broad outcrop of gneissic rocks, then a 

broad outcrop of quartzite, and above that limestones 

and shales. These rocks necessarily furnish the material of the piedmont alluvium. In both the older and 

the younger alluvium the conspicuous and readily 

identifiable materials are quartzite and gneiss, the 

quartzite being specially distinguished by its pale 

colors. I did not visit tract A of the older alluvium 

but was able to compare the material of tract B with 

that of an adjacent tract of modern alluvium. In 

both tracts the greater number of boulders and large 

blocks are of quartzite and the greater number of 

pebbles are of gneiss, but the proportions are not the 

same. I estimated the percentages of quartzite and 

gneiss among the boulders and found about 60 per cent 

of quartzite in the modern alluvium and 95 per cent in 

the older. The difference seems too large to be 

E.. 

N. 

Bonneville shore terrace 

Rock \ 

\ 

\ 

\ 

w. 

A 

5 

Talus and -a-lI-uvi-um---'Bo~~g:~lIgliff 

B 

FIGURE 2O.-ProfUes of base of Wasatch Range, Utah, at points between canyon mouths. Approximate scale; 1 inch=4,500 feet. A, 

Profile about 1 mile south of Willard; constructed from photographic 

data. B, Profile at A, Figure 22; copied from photograph 

ascribed to accident of locality and gives some support 

to the inference that at the time when the alluvium of 

tract B was accumulating the belt of outcrop of the 

gneiss was narrower than now. On the other hand, 

the presence of a few boulders of gneiss in the older 

alluvium shows that the gneiss was not wholly covered 

while the deposit was being formed. The throw of the 

frontal fault may have been 1,000 feet less than now 

at the date of the older alluvium. 

The history of the alluvium of tract A was not made 

out but is believed to differ materially from that of 

tract B. The piedmont forms are there peculiar in 

several ways. As a rule an alluvial apron is made up 

chiefly of conical deposits spread from canyon mouths, 

. and contributions received from intercanyon waste 

are relatively small, so that the convex elements of 

contour are opposite to canyons, but in this place there 

is a pronounced salient of the alluvial apron between 

canyons. As a rule the slope of the apron near the 

rock base of the Wasaich1Range is so much gentler 

than the adjacent rock slope that the position of the 

rock base is closely defined by change of slope, but 

here the profile (fig. 20, A) shows a continuous sweeping curve from a point high on the range to one low 

on the apron. As a rule, along this part of the range 

front, the line of the rock base is paralleled by a fault 

scarp in the piedmont slope, but just here the piedmont 

scarp is interrupted. Associated with these features 

is an . element of internal range structure. The range 

front here exchanges a southward trend for an eastward, but the tectonic block that constitutes the front 

from Willard to this point does not follow the bending; 

it ends here and is shown in cross section on the 

southerly. face. Another block, with unrelated dip, 

adjoins it on the east, and beyond that stands yet 

another, each characterized by the position and attitude in which it holds the same conspicuous quartzite 

member. The peculiar phase of the piedmont is 

opposite the end of the first-mentioned block. 

The evidence of a fault between the spur and the 

range consists in part in the continuity of range 

features from the escarpment back of the spur to the 

sheared quartzite at the Willard locality. The outcrops of quartzite and gneiss are visibly continuous, 

and so is the fresh scarp in the piedmont. alluvium, 

which runs to the point marked C in Figure 18. 

After disappearing at C the scarp reappears at about 

D; and between D and North Ogden Canyon it is 

accompanied by outcrops of fault gouge. (See p. 19.) 

So the position of the spur lies between two localities 

that afford evidence of fault friction at the base of 

the escarpment. Of the same tenor is the relative 

abundance of gneiss boulders in the newer alluvium 

near tract B, with its implication of the broaden~g of 

the belt of exposed gneiss on the face of the range. 

The arrangement of quartzite and limestone belts in 

the spur is also indicative of faulting, although it 

. implies nothing as to the time of faulting or the 

particular position of the fault plane. In the range 

the outcrop of the quartzite (the older formation) is 

west of the outcrop of the limestone, arid in the spur 

also the quartzite, as mapped by Hague and Blackwelder, is west of the limestone. This is the arrangement that would result from dislocation by faulting 

and not that which would be given by an anticlinal fold. 

Hague's map should perhaps not be cited in this 

connection, because the inference with which it is here 

associated is not sustained by his text. He wrote of 

the range in this part as the eastern part of It an anticlinal fold, whose western member has been broken 

down and carried away," and in speaking of outcrops 

on the spur he said: 

Broken masses of quartzite and limestone are seen lying, 

sometimes :flat, sometimes tipped up at steep angles, and 

dipping both east and west. It is evident that these are the 

remains of the Cambrian and Silurian beds which form part of 

the western fold, but the masses are too much obscured to 

afford any definite structure lines which may give the clue to 

the position of the beds beneath the valley.23 

II HagUe, Arnold, U. S. Gool. Expl. 40th Par. Rept., vol. 2, pp. 393, 402, 1877. 

I 
WASATCH RANGE, UTAH· 27 

The evidence of faulting about the outer margin of 

the spur is comparatively meager. Despite the irregularity of its surface the spur is a plateau (see pI. 9, A), 

sloping gently toward the southwest, and the plateau 

top is separated from the valley plain by a relatively 

steep slope. For more than a mile on the west side 

the limiting slope abounds in cliffs. The base of the 

steep slope, mapped in Figure 18 as the position of 

the fault, is a line of simple character, although it 

bends from west-northwest to northeast. Olose to the 

rock base, at a point where the plateau front is specially 

steep, is a group of hot springs. A considerable number 

of thermal springs in the cordilleran region are so 

associated with special geologic features as to admit 

of genetic classification, and these fall into two groups. 

The source of heat for one group is volcanic; the waters 

of the other group rise from great depths along faults. 

Therefore the occurrence of thermal springs is not by 

itself demonstrative of faulting, but in connection 

with other evidence it may be regarded as confirmatory. 

In Figure 18 the fault line has been drawn with 

confidence along the base of the plateau front as far 

as the front contains rock exposures. From one end 

it has been continued tentatively northeastward 

toward the base of the range because the plateau and 

plateau front continue to the base of the range. From 

the other end it has been turned tentatively toward the 

north, so as to separate the tract with scattered rock 

crags from a piedmont tract without visible rock. 

In this deflection it has been directed toward 0, the 

end of the fresh piedmont scarp, that course being 

suggested by the fact that the history of the alluvial 

tract A differs from that of tract B. 

TRAVERSE SPUR 

From the Lone Peak salient of the range a spur runs 

westward, as shown in Figure 21. It is about 7 miles 

long and 3 miles wide, and its highest points are 

1,200 to 1,500 feet above the bordering valleys. Its 

sculpture is mature. Its contact with the range lies 

along the south face of the granite body of the salient. 

The intermont valley invaded by it is invaded from 

the opposite side by a broader spur of the Oquirrh 

Range, and the two spurs leave a passage only 2 miles 

wide. As the two spurs are regarded as a partition 

that separates Utah Valley at the south from Salt 

Lake or Jordan Valley at the north, they have -been 

given a single name-the Traverse Mountains. It is 

possible that they belong together geologically, but so 

far as now known their structural features are independent. The easter~ hills have a basement of sedimentary rocks and are partly covered with trachyte. 

In the western hills have been found only volcanic rocks. 

In the following paragraphs the hills connected with 

the Wasatch Range are called the Traverse spur. 

A single stream from the rang~ crosses the spur and 

by opening through it a steep-sided valley, Fort 

Oanyon, has separated a small eastern part from the 

main portion. The smaller division contains only sed-

-imentary rocks. The western division shows limestone and sandstone along Fort Oanyon and also along 

part of the southern base, and much of its northwestern 

base consists of quartzite. All the higher part is known 

to be made up of trachyte, but the boundaries have 

not been traced. The age and structure of the sedimentaryrocks have not been determined, but there can 

be little question that the formations are Paleozoic 

-and that they have shared in the early diastrophic 

changes of the rocks of the range. 

The junction of the spur with the range is marked 

topographically by a sag or groin. In part this sag 

follows the line of contact, and in part it runs within 

the spur and approximately parallel to the contact. 

Where it is not on the contact the details of hill form 

suggest landslides. (See pI. 10, A.) As shown in 

another section (see p. 39), there is reason to regard 

this sag as a variant or an equivalent of the fault 

Quaternary 

Granite 

Draper 0 

.... ,.l:: 

>'~.'Lone Peak 

Paleozoic 

N 

r 0 SMILES I I 

FIGURE 21.-Sketch map of Traverse spur and adjoining part of 

Wasatch Range, Utah 

scarps of the alluvial apron. Post-Bonneville scarps 

of the usual type follow the base of the range on both 

sides of the spur and disappear at the junction of 

spur and range. A careful scrutiny of the alluvial 

apron of the spur discovered no similar scarp. It is 

inferred that at the time of the latest movement or 

thJlater movements, on the frontal fault, the relation 

of the spur to the valley was not changed. 

The shearing of the granite, near the contact, at 

Fort Oanyon has already been mentioned. A similar 

structure farther west is suggested by the appearance 

of the granite slope, as shown at the right in Plate 10, 

A, but I did not visit the spot. Still farther west 

Emmons 24 fq,und at the contact of granite with trachyte 

a foliated rock apparently identical with the contact 

rock at Fort Oanyon. He refers it, with such qualification as is implied by the word "doubtless," to the 

group of Archean schists which flank th~ granite on . 

U Emmons, S. F., U. S. Geol. Expl. 40th Par. Rept., vol. 2, p. 357,1877. 
28 STUDIES OF BASIN-RANGE STRUCTURE 

the northwest, but the fact that it occurs at the contact 

gives plausibility to the alternative suggestion that it 

belongs to the shear zone of the granite. 

There is a saddle between the range and the crest 

of the spur at S, Figure 21. The view in Plate 10, A, 

looks toward the saddle from the east, showing the 

spur at the left and the granite of the range at the 

right. The drainage line of the sag here runs wholly 

on the spur. Beyond the saddle the descent is northwestward, and a small stream, aptly named Corner" 

Creek, flows along the. groin. The creek for sonle 

distance follows the contact and for much of that 

distance has sunk its channel into the granite. The 

slope of the granite surface is 200 or less, and the rock 

FIGURE 22.-Sketch of Lone Peak salient of Wasatch Range, 

Utah, from the west, showing spiral furrows. At right, 

hill of the Traverse spur. In the distance a peak of the 

Timpanogos Wasatch 

resting against it is either trachyte or a product of 

the decomposition of trachyte (see p. 39), both more 

easily eroded. than the granite. Under such conditions the stream may erode its weaker bank and shift 

its channel laterally down the surface of the stronger, 

or it may corrade the stronger rock beneath it and 

thus intrench itself and establish a permanent channel. 

The determination of one or the other of these alternatives will depend on several factors, among which are 

the relative erosibility of the two rocks, the slope of 

the central plane, and the power of the stream to 

corrade. 

On the face of the granite above the creek are 

anomalous channels, which find their explanation in 

the channel of the creek. Instead of descending the 

face in the direction of its general slope they descend 

obliquely, following lines which approach more neEh-ly 

topographic contours. They are approximately parallel to the channel of the creek and are in fact ancient 

channels of Corner Creek, stranded on the face of the 

salient. They mark former positions on the granite of 

the edge of the trachyte. In 1901 'I sketched the old 

channels from a neighboring summit on the spur, and 

the lines of. the sketch have been reproduced at b in 

Figure 23. In 1917 a sketch was made from the northern base of the spur, and the lines of this sketch appear 

in Figure 22. In each figure the sky line of the spur is 

drawn from a photograph too poor to afford details of 

the mountain face, and the lines of the sketch have 

been adjusted to the more accurate data from the 

canlera. The later sketch represents three spiral channels; the earlier represents two, each with a branch. 

It is probable that the highest line was not recognized 

in the earlier view and that the branches fall outside 

the field of the later view: At the time of the earlier 

sketch I estimated the vertical interval between the 

creek and the lowest stranded channel at 200 to 300 

feet near its lower end and at 500 feet near its head; 

and I estimated the interval between the two observed 

old channels at 500 to 600 feet. As shown by Figure 

22, the interval below the highest channel is still 

greater. 

Plate 10, B, gives a view on the lowest of the old 

channels. The trench still carries drainage, for it is a 

gutter, intercepting all precipitation on the slope 

between it and the channel above, and its V-shaped 

section indicates that its storm-water streanl is efficient. The rounded rim tells of weathering, and its 

granite shows decomposition, but there is no deep 

decay. 

The stranding of the creek channel is evidently a 

result of the shifting of the line of contact between the 

granite and the rock of the spur. On the assumption, 

for simplicity of statement, that the granite has held 

its place, the surface of the trachyte has been lowered 

and with its lowering the position of the creek has 

shifted" down the granite slope. The lowering of the 

trachyte has been due in part to wasting but in 

larger part, I think, to faulting. In the intervals between fault slippings the creek has corraded the granite, and occasionally, during a long interval, it has corraded so deeply as to become intrenched .. After the 

next faulting all the water from the granite slope above 

Lone Peek 

FIGURE 23.-Diagram of southern face of Lone Peak salient of Wasatch 

Range, Utah. The profile is taken from a distant photographic view. 

The middle line represents the rock base. From a to g the base is at 

contact with the Traverse spur, passing Fort Canyon at t. From 

g to i it is at contact with an alluvial apron 

wou~d be caught by the corraded channel and all the 

water from the trachyte slope would gather along the 

newly placed contact line. With further faulting the 

interspace between the stranded channel and the new 

contact channel would increase, and with its increase 

the discharge of the contact stream would become 

greater; and it is possible that the rhythnlic character 

of the stranding was determined in this way. I would 

not, however, give emphasis to this suggestion, for 

epochs of local rest in a period of general diastrophism 

might be inferred as probable from what we know of 

the time distribution of earthquakes. 

The fact that the old channels approach one another 

as they descend affords a clue to the relative effective-
WASATCH RANGE, UTAH 29 

ness of faulting and degradation in the lowering of the 

spur at the contact. Under the assumption that 

changes in the valley to which Corner Creek discharges 

have been relatively small, so that the valley has 

nfforded a fairly constant base-level, the lowering of 

the creek profile should be greatest at its head and 

diminish downs tre anl , and such a change of grade is 

of the proper kind to explain the lack of parallelism in 

the old channels. It is true that the crustal block on 

which the creek runs may be tilting eastward and that 

the crustal block of the mountain may be tilting westward, but if such changes are in progress they are probably slower than changes of profile from progressive 

degradation. If it is proper to ascribe the whole of 

the convergence to degradation, and also to think of 

the creek level at the lower end of the groin as stable, 

then the height of an old channel opposite that point 

on the creek represents the addition to the throw of the 

fault since the creation of the channel. The lower end 

of the highest channel, shown in Figure 23, is opposite 

the lower end of the groin, and the difference in height 

has been estimated, with the aid of a photograph, at 

1,300 feet. The height of the same channel at the 

sky line of the picture, above the corresponding part 

of the creek bed, is estimated at 2,000 feet. The 

difference between these, 700 feet, is the estimated 

vertical factor in the change of creek slope since the 

epoch when the old channel was formed. 

'rhe state of preservation of the old channels and 

especially the fact that they have not been convel'ted into deep gorges but are still inconspicuous 

notches on the granite face warrant the inference 

that during the existence of the channels the wasting 

of that face has made little progress. It is believed 

that so little has been removed from the general surfn,ce that the smooth profiles in Figures 22 and 23 do 

not grossly misrepresent the shape of the granite mass 

before it was uncovered. This subject will receive 

further attention, and additional evidence will be 

presented in another connection. 

In the present connection may be mentioned another 

set of oblique channels, seen on the southern face of 

the salient at points farther east. They are represented at d, e, j, and h in Figure 23. Their angles of 

descent are very s,teep compared to those of the Corner 

Creek group. The lower end of the channel marked 

e was seen close at hand ~d was thought to be related 

to the groin between the granite and the eastern division of the spur, but the higher portion of the same 

channel did not seem to admit of explanation as an 

ancestor of the groin. No adequate interpretation 

of the group has been suggested, and it is mentioned 

only as a promising subject for future study. 

While the waves of Lake Bonneville were making 

their highest record there was a small bay into which 

Corner Creek then discharged. They carved rather 

deeply on neighboring slopes of the range and the 

spur, and the cliffs they created are now conspicuous 

features,. but they did not carve the shores of the, bay. 

Detritus from the cliff at the north was drifted along 

the shelf at the base of the cliff and built into a bar 

across the mouth of the bay, thus separating a triangular lagoon from the lake. Afterward the creek washed 

out the middle part of the bar, so that it is represented now only by its ends, one of which stands on 

the range and the other on the spur. The remnants 

are on opposite sides of the fault, and their present 

difference in level gives a definite record of the addition that has been made, at this point, to the throw 

of the fault since the time of the lake. It is 37 feet. 

During the Provo stage of the lake, 400 feet lower, 

. whatever bay may have at first existed was filled by 

debris brought by the creek, and through the plain 

thus formed the creek has since opened its valley. 

A remnant of the plai;n is crossed by a fresh fault 

scarp with a throw of about 15 feet. (See pI. 11, A.) 

From these data it appears that only a part of the 

vertical change since the time of the higher shore 

line has occurred since the completion of the lower 

shore line. The remainder of the change took place 

during the presence of the lake. 

Definite evidence of faulting was not' found along 

the outer margin of the spur. Where the rock at the 

margin is trachyte the margin may represent the 

limit of a lava flow, with subsequent shaping by 

erosion. The lava may not everywhere have a foundation of Paleozoic rock but may rest in part on alluvium 

or other valley deposits. Except at the east end of 

the spur, where there is no trachyte, the topographic 

prominence of the spur may be due wholly to eruption. On the northwest side, where the foundation 

rocks are best known, they do not stand in wellmarked relief above the valley deposits, and the line 

of separation has been obscured by the work of the 

waves of Lake Bonneville. Perhaps the best indication of the position of the hypothetic fault is given by 

a group of warm springs about half a mile northwest 

of the tract in which the foundation rocks are exposed. 

HONEYVILLE SPUR 

The village of Honeyville stands in part on a low 

table that projects as a step from the base of the range. 

The table is less than 100 feet high, and its width in 

any direction is between three-quarters of a mile and 1 

mile. It is a dislocated tract of valley plain and piedmont slope that has been moved valleyward a short 

distance, tilted mountainward, and perhaps slightly 

lifted. Its visible material is gravelly alluvium, 

partly reworked by waves and partly cemented. The 

western (outer) half of its surface is nearly level,. except 

for scattered, isolated subconical hillocks. N ear the 

mountain the surface shows ridges, that have a northsouth trend, in graben and horst fashion. The corrugation is strongest close to the mountain base and ends 
30 STUDIES OF BASIN-RANGE STRUCTURE 

iin a fresh-looking scarp, the height of which is estimated at 100 to 125 foot. Next to the scarp is a graben 

which is in part undrained. (See pI. 11, B.) The 

high scarp is about half a mile long and at its south 

end is curved vaUeyward, with diminishing height. 

The weste~n face of the table may have been washed 

by waves, but the scarps, ridges, and hillocks show no 

modification by waves. The table was formed after 

the retirement of the waters of Lake Bonneville. 

The hillocks have the same material as the table, 

including cemented gravel; and blocks of cemented 

gravel in them are tilted. Apparently they have been 

pushed up from below, but no adequate explanation of 

their uplifting has occurred to me. The only related 

features with which I am acquainted are certain 

gravel hills that rise above the lake plain a few miles 

farther south. One of these hills, north of Call's Fort, 

is cut through by the Ogden & Idaho Interurban Railway, and two others stand near that railway between 

Perry and Woods stations. As seen from the train 

they appear to be whol1y surrounded by the lake beds 

of the plain, which is there fia.t. 

The table may be the summit of a crustal block that 

has recently been disturbed in its relation to other 

MADSEN SPUR 

A short distance north of the Honeyville spur is the 

Madsen spur. Its width and length are each somewhat more than 1 mile. Its height near the outer edge 

is about 200 feet and near the mountain about 300 feet. 

Its upper slopes join those of the alluvial apron, as 

indicated in Figure 24. Its visible material is gravelly 

alluvium, in large part worked over by shore waves, 

and the details of its form testify to wave action at all 

levels. Its steepest face fronts toward the west and 

overlooks a level plain througb which winds the incised 

channel of Bear River. Under the base of the steep 

face is a group of hot springs with large discharge, and 

the issuing stream on its way to Bear River follows a 

deeply sunken channel through the plain. In visiting 

the locality I neglected to make a close inspection of 

the springs and failed to observe a rock exposure which 1 

as I now know, was noted by both Fremont (1843) 

and Gunnison (1850). Fremont 25 says that thespringR 

issue" beneath a conglomerate consisting principally 

of fragments of a grayish-blue limestone"; and Gunnison 26 characterizes the rock as "conglomerate and 

limestone." These records, related as they are to 

FIGURE 24.-East-west section of Madsen spur of Wasatch Range, Utah. Length of section about 7,500 feet 

blocks beneath the valley deposits, or the movement 

creating it may have involved only superficial formations. The dislocation of a crust block would produce 

a fault scarp about the outer margin, and a fault scarp 

as recent as the scarp along the mountain base could 

not have escaped attention, unless it was obliterated 

by more recent wave action. Such a fault scarp was 

not noted, and if the margin has been reworked by waves 

the resulting beaches are inconspicuous. I therefore 

incline to regard the table as a landslide. The corrugation of a landslide arises chiefly from the breaking 

away of successive slices of earth. If the table, which 

is corrugated only along the edge near the~ mountain, 

is a landslide it may be assumed that the main body 

moved all together and practically as a unit and that 

the ridges started o,ne at a time and later. The slope 

of the piedmont is here gentle, and the intermont 

valley is occupied mainly by a lake plain. These 

features indicate the need of an exceptionally good 

slipping·surface, and they also suggest that the surface 

may be' furnished by a buried lacustrine ooze of even 

inclination. The hypothesis as thus formulated, how-

~yer; faUs' to explain th~ sqbconical hiUoc~s. 

waters of high temperature issuing from the base of a 

tabular spur, indicate unmistakably a fault breccia 

similar to that at the base of the City Creek spur. 

(See p.23.) 

From these data I infer that the spur represents 

a crustal block which at some late but pre-Bonneville stage of the ·frontal fault of the range parted 

company with the sinking valley block and joined 

itself to the rising mountain block. In rising the 

block carried with it a body of alluvium that had 

previously been washed from the rising range to the 

valley, and the lifted alluvium, although exposed 

to the waves of Lake Bonneville, has not been so long 

subject to agencies of erosion as to have lost its tabular character. (See fig. 24.) 

The northern face of the spur has been greatly 

modified by landslides, and the resulting topographic 

forms show no trace of subsequent wave action. 

The sliding has therefore taken place since'-Jthe reu Fr6mont, J. c., Report of the exploring expeditions to the Rocky Mountains In 

th,e year 1842 and to Oregon and North California in the years 1843-44, p. 159, 1845. 

26 Gunnison, J. W., in Stansbury, Howard, Explorations and survey of the valley 

of the Great Salt Lake of Utah, including a reconnaissance OfB new route through the 

ltock}" Moqntains: 3~q Cong., spec. sass., S. Ex. Doc. 3, p. 213, 1853. 
ASATeH RANGE, UTAH 31 

tirement of the old lake. Nevertheless it has been 

extensive, and its history appears not to have been 

altogether simple. The dominant trend of the displaced ridges is easterly, but in the western part of 

the area are some with northerly trend. Figure 25' 

shows diagrammatically the disposition of the easterly 

ridges, which are in two groups. Those of the more 

ant and earlier-formed group are relatively small 

and stand at a lower level. Plate 12, A, shows the 

scarp at the head of the series, with ridges of the later 

group and an associated broader earth block that was 

tilted forward as it moved. 

OTHER SPURS 

Half a mile north of Odgen Canyon is a buttress of 

the range, rather abruptly salient, as indicated in 

Figure 26, and roughly conical in shape, as 

to lowlands at the north and south, are not occupied 

by belts of detrital plain but are narrow passages 

between discontinuous bodies of rock. 

SUMMARY AND CONCLUSIONS 

The Honeyville table is of doubtful origin and need 

not be included in a summary of fault-block spurs. 

The Madsen, Pleasant View, City Creek, and Traverse 

spurs are the upper parts of crustal blocks that are 

separated by normal faults from the Wasatch block 

on one side and from the valley block on the other, so 

that they stand lower than the one and higher than 

the other. Their dislocations belong to the later, 

post-Eocene period of diastrophism, but at least two 

of the spur blocks show internal faults that were 

acquired in a pre-Eocene period. The Madsen, 

Pleasant View, and City Creek blocks are capped in 

N. 

shown in Plate 12, B. Its rock is an exception- . s. 

ing 

ally 

it 

hard 

in the 

and 

body 

tough 

of 

dark-gray 

the range 

gneiss. 

are gneisses 

Adjoinof FIGURE ~ 

25.-Diagrammatic north-south proftle of Madsen spur of Wasatch Range, Utah. 

~ The 

spur is a little over a mile in width and 200 to 300 foet in height paler color which weather more easily. When 

viewed from a distance it has the appearance of an 

excrescence of the range, but the nature of its separation from the body of different gneiss was not determined. A piedmont scarp, which follows the rock base 

of adjacent parts of the range, follows with equal 

fidelity the somewhat angular base of the buttress. 

I did not satisfy myself whether the buttress should 

be classed as an independent crust block or as a knob 

projecting from the Wasatch block, a knob so strong 

and hard that it has plowed its way through the hanging wall as the valley block descended. 

Most other spurs and flanking tables are associated with canyon mouths from which large streams 

issue and are remnants of the deltas built by the 

same streams in Lake Bonneville. They occur in 

pairs, each original table having been divided by 

later stream erosion; their gravel is better rounded 

than that of the alluvial apron, and sections show 

inclined, "foreset" bedding. These features serve 

to distinguish them from spurs of diastrophic origin. 

South of Santaquin the range is bordered by' a 

group of ridges which have been described by Loughlin.21 These ridges are parallel to one another and 

to the range front and are separated by faults with 

downthrow to the west. The faults, which are 

demonstrated by stratigraphic evidence, are also 

expressed in the topography, and the ridges, although 

too short and narrow to rank topographically with 

features commonly called ranges, must be classed 

structurally with the fault-block ranges. They differ 

in topographic type from the range system of the 

Great Basin in that the interridge troughs, draining 

17 Loughlin, G. F., Reconnaissance of the southern Wasatch Mountains, Utah: 

Jour. Geology, vol. 21, pp. 436-45~, 19~3. (See ~specially ~~. 448-4~2 ~nd fi~. 4.) 

whole or in part by alluvium from the Wasatch Range, 

alluvium that was once part of the piedmont apron of 

the range; the Traverse block mayor may not have a 

similar deposit beneath its capping of trachyte. The 

presence of this alluvium and its dislocation from the 

general modern alluvial apron of the range show that 

the spur blocks were once so associated with the valley 

N 

r 

FIGURE 26.-Ground plan of block spur north 

of mouth of Ogden Canyon, Wasatch Range, 

Utah. The heavy line shows the rock base; 

the light line the piedmont scarp 

block as to receive the same deposit and have since 

been lifted with reference to the valley block. 

A post-Bonneville piedmont scarp runs between the 

range and the Pleasant View spur, and the s~me is 

true of the Traverse spur and perhaps of the Madsen, 

the indication being that in the very latest movem~nts 

these spur blocks have adhered to the valley block. 

The post-Bonneville scarp runs outside the City Creek 

spur, showing that in recent time that spur block ha.s 
32 STUDIES OF BASIN-RANGE STRUCTURE 

adhered to the range block. These diversities in history show that the conditions determining adhesion 

to the rising range or to the sinking valley were local 

and variable. . 

The City Creek spur bears an early Tertiary formation on the back of its body of pre-Cretaceous rocks. 

The Pleasant View spur is definitely characterized by 

the absence of a similar early Tertiary cover. The 

constitution of the Madsen spur is masked by its cover 

of piedmont alluvium, and that of the Traverse spur 

has not been adequately studied. At the time of the 

initial dislocation between the range and the valley 

the City Creek and Pleasan t View blocks went down 

with the valley block and were thereby protected, 

wholly or partly, from the erosion to which the rising 

range was subject. Their condition therefore tells 

something of the condition of the land at the beginning 

of the orogenic movement. The surface was in part 

occupied by dislocated and inelined bodies of older 

rocks, much reduced by erosion, and in part by early 

Tertiary terrestrial deposits which had also been disturbed and eroded. 

Two of the spurs are associated with pronounced 

salients of the range. The Traverse spur adjoins the 

great granite salient; the Pleasant View spur touches 

an equally marked outward curve of the frontal fault. 

The Madsen spur is opposite the northern limit of a 

small embayment of the range front, so that it is 

associated with a minor convexity of the front. (See 

fig. 13.) The Honeyville table stands opposite the 

southern limit of the same embayment. The City 

Creek spur probably but not certainly covers a local 

outward swing of the line of the frontal fault. These 

relations suggest that .~he local conditio~s that determined the spurs were the same as or were connected 

with the conditions that determined the salients. 

Irregularity in the fracture surface of the great orogenic 

fault 'was occasioned by heterogeneity of the faulted 

terrane. Elements of irregularity in the direction of 

strike are manifested in flexures of the fault line, and 

to this class belong the salients. Coordinate with 

these flexures are irregularities on lines of dip, and as . 

the fault .movements were in the direction of the dip 

there was a constantly renewed discordance between 

the forms of hanging wall and footwall. Also, because 

the weight of the overlapping valley block enforced 

contact, there was a constantly renewed adjustment. 

As already pointed out, part of this adjustment was 

accomplished through abrasion and another part 

through flow. In the upper and less loaded portion 

of the valley block part of the adjustment may have 

been affected through fractlires that reach the top, 

and it1 the thin portion of the valley block near the 

fault line fractures may have extended from top to 

bottom, so that fragments of the valley block may 

have been detached and dislocated. Figure 27 is introduced to illustrate this suggestion by an ideal example. 

The local dip line is a!3sumed to be straight except at 

a single place, low down, where a firmly fixed knob of 

strong rock projects from the footwall. During early 

stages of the movement (A) weaker rocks of the valley 

block make the necessary adjustment by flow. At some 

later stage the knob punches out a piece of the valley 

block, creating a spur block. If the spur block were 

merely severed aud the valley block moved away from 

it a chasm would be created (B) like the crevasse of a 

glacier, but the parts are too heavy to permit this, and 

their settling yields a condition like that shown in 

(C), with canting of surfaces toward the range block 

and a scarp between the spur block and the valley 

bloek. 

v R 

A 

R 

v 

B 

R 

v 

c FIGURE 27.-Ideal sections of progressive dislocation of valley blook, 

V, and range block, R, to illustrate QypotQetic derivation of spur 

block S 

It is noteworthy that all four of the fault-block 

spurs are accompanied by thermal springs, whose 

waters rise along their outer bases. I know of but 

two localities of thermal springs on the line of the 

frontal fault of the range. The SpW' base is lower 

than adjacent parts of the range base, and the point 

of issue at each spur locality may be determined by 

that fact, but that consideration does not explain 

the scarcity of thermal waters on the long line of the 

frontal fault. It may be that the outer faults of the 

spurs are peculiarly favorable for the conveyance of 

deep penetrating circulation because of the less perfect adjustment there of the fault walls. 

The highest recorded temperatures for the thermal 

springs are, Madsen spur, 134° F.; Pleasant View spur 

(Red Springs, Utah Springs), 136°; City Creek spur 

(Beck's Spring), 133°; Traverse spur (Draper Springs), 
U. S. GEOLOGICAL SURVEY 

A SCAHPS IN MOHAINE 

The Pleistocene glacier of Lillie CoUonwood Canyon protruded beyond the mouth of the canyon and bu il t laleral moraines just.. outside. The view shows the left or south moraine, with doubl e crest and wilh d islocations marked by scarps. 'rhe scarp at the left, running up from the railway cut, is relatively young and is scantily clothed by 

bushes. Others at the right arc older 

PROFESSIONAL PAPER 153 PLATE 13 

B. SCAnI' AND GBABEN IN ALLUVIAL ArBor; 

Vicw a long the west face of the range. The valley features ate north of Big Collonwoo:l Canyon. Bel,ween the foreground and the high pied mont scarp is a tract of land dropped 

below the general level 

PIEDMONT SCAHPS IN WASATCH RANGE, UTAH 
U. S. GEOLOGICAL SURVEY PROFESSION AL PAPER 153 PLATE 14 

A.. SCARPS IN ALLUVIUM 

The Wasa tch escarpment between Big Cottonwood "and LiLLIe Cottonwood Canyons shows dissected facets. The piedmont scarp nearest the mountain is at the right the strongest of the series, but in the center and at lhe left the second scarp is the strongest. At the right of the center the second branches; its upper branch joins the first scarp; its lower branch tapers and nearly disappears. Below the second arc several smaller scarps 

The left lateral moraine left by the Little Cottonwood glacier is shown in Plate 8, A. The right. tuleral moraine, here shown, is fl at-topped. The principal piedmont searo crossing it has a companion scarp faciog toward the range, aod bel ween them is a graben. The view looks northward 

PIEDMO T SCARPS IN WASATCH RANGE, TAB 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 15 

A. SCARPS NORTH OF OGDEN CANYON 

The lower of the two scarps is the younger, as shown by ils sharper definition at the top. Compare Plate 17, B 

While the Lake Bonneville waves were shaping the Provo shore line Weber River built a large delta at t he edge of the lake. The piedmont scarps across this delLa are high. The. terrace above the one pictured is an undisturbed part of the della. The plain below it is another part of the delta, dropped and tilted toward the range. The highest Bonneville shore line appears as a terrace on the faeels of tbe range front 

PIEDMONT SCARPS IN WASATCH RANGE, UTAH 
U . S. GEOLOGICAL SURVEY P R OFESSIONAL P APER 153 PL ATE 16 

A. SLIDE 0 A STEEP HILLSIDE 

The material is regolith. The irregular scarp at the head corresponds to unevenness of Lhe surface of unaltered rock over which the body of regolith. moved. The bulging mass below is the complement. of the cavit.y above. The slide was s tarted by an earthquake shock, but the principal movement Look place lat..ee, afLer the ground had been sa tura ted by rains 

B. SLIDE ON A MODERATE SLOPE: 

The materi al is earth, washed f rom above. A large coherent block inclj nes forward ; o ther blocks incline backwa rd. The scarp shows III nate forms 

LANDSLIDES IN BERKELEY HILLS. C ALIF. 
U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 17 

A. LANDSLIDE NEA ll U INTAH, UTA H 

Weher River has carved n valley Lhrough a delLa huil L by Lhe same r.iver in Lake Bonneville. T he va lley walls break away ill la nd slides. The lop of one of the slid masses appears at, the lert in the view as a group of hiJlocks. At the right is lhe scarp from which the mass par led. The sag between contuined a small pond, which has been eLl largcd by means of a dam 

B. PIEDMONT SCARPS NEAR CITY RESE RVOIR, OGDEN, UTAH 

At this point are tbree scarps, as sbown by the profile in Figure 32. The view, commanding two of them, is from the crest of the tbird. Tbe upper of tbe two shown is t he younger, as indicated by its sharper definition. Compare with P late 15, A. Tbe upper scarp is a con- spicuous feature in Plate 8, B 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 18 

A. SCARP ALO G SOUTH BASE 

B. SCAnI' ALONG NonTH BASE 

PIEDMONT SCARPS ABOUT BLACK SPUR OF W ASATCII RANGE, UTAH 

The black spur is at tho west base of the range, 1 mile north of Ogden Canyon. Its form , shown in Plate 12, B. is closely related to the dip of the fault about its base. Wbere the fault dip is relatively steep (north side) the piedmont scarp is rcla- ti vely near to the rock base 
WASATCH RANGE, UTAH 33 

128°; frontal fault at lnouth of Ogden Canyon, 150°. 

In some springs, however, and probably in all, the 

temperatures are variable. For the hottest Madsen 

spring the records range from 128° to 134°, for Beck's 

Spring from 126° to 133°. The observations of Bradley 28 on the Madsen springs show that the higher 

telnperatures are associated with relatively small 

volume. He found larger volume and lower tempern.ture (128°) in June, the snIaller volume and higher 

temperature (132°) in November of the same year. 

Observations of the temperature of Beck's Spring are 

accordant but are less significant because made in 

different years and without comparative data on 

volume. On' July 5, 1877, I obtained 126°, and on 

August 30, 1917, Mr. Sterling B. Talmage 29 foulld 

133°. 

As ground-water springs are lowest i,n autumn, and 

as the circulation at great depth is less sensitive to 

seasonal influences, it is safe to infer that the fluctuating temperatures of such thenual springs depend on 

the dilution of a practically constant discharge of 

uniformly hot water rising from the depths with a 

variable discharge of cool!ground water. If the volumes of the springs associated with different temperatures were known, and also the ground water temperature, it would be possible to compute the temperature of the undiluted hot water. Lacking these data, 

we may infer that even the hottest spring water is 

probably sOlnewhat diluted by ground' water, and 

that the temperature of the water rising along the 

fault is higher before dilution than any of the recorded 

spring temperaturcs. In localities that show no indications of recent volcanism the heat of waters rising 

n.long faults is presmnably derived from the inner 

earth's store. The water that rises toward a spring is 

necessarily part of a circulation; it has received heat 

in the lower portion of its course and has parted with 

some of it whUe ascending. Its temperature as it 

approaches the surface luay be near to but can not 

equal the rock temperature of the lower part of its 

course. The luean annual temperature of the air at 

Salt Lake City is about 52° F.,30 and this nIay be assumed as the earth temperature at the surface. The 

highest recorded spring temperature at the base of a 

spur is 134°, or 82° above the surface temperature. 

On the assumption that the local temperature gradient 

is 1° for each 75 feet, the depth at which a rock temperature of 134° is reached is 6,150 feet. This may be 

accepted as an underestimate of the depth to which 

water circulates on the faults that limit the spurs. 

IS Bradley, F. H., U. S. Geol. Survey Terr. Sixth Ann. Rept., p. 199, 1873. 

tD Finding confusion in the records of thermal springs near Salt Lake City, I sent 

out a letter of inquiry, which fell into the hands of Mr. Talmage. His response 

Included asulteoftemperatureobservations, made Aug. 30-31, 1917, which are worthy 

oC record although, in their fullness, not germane to my text. In the following list 

the order is from south to north: Salt Lake City warm springs, No.1, 350 C. (950 F.); 

No.2, 360 C. (970 F.); No.3, 40° C. (104° F.); No.4, 42° C. (1080 F.). Sanitarium 

Spring, "The Pump," 112° F. (reported by management of sanitarium). Jones's 

warm spring, 37° C. (99° F.). Beck's hot spring, 56° C. (1330 F.). 

II U. S. Weather Bur. Bull. R, 1908. 

A probable estimate would include allowance for the 

water's loss of heat by conduction during its ascent 

and for the fact that the observations of tenIperature 

are made after the rising current has received more 

.or less ground water. 

The fault-block ridges near Santaquin, described by 

Loughlin, have definite trends, parallel to the trend of 

the Wasatch Range. This description could be applied 

to one of the fault-block spurs, the Pleasant View. 

The Traverse spur trends westward, and the others 

are without notable trend. This difference probably 

indicates that the Santaquin ridges and the spurs are 

of distinct types. The Santaquin ridges are small 

fault-block ranges. The spurs are subsidiary features 

of the frontal fault of the large range. The relation 

of the San~aquin ridges to Juab Valley and to Utah 

Valley suggests that they may constitute an exceptionally high part of the floor of a long intermont 

trough, that other parts of the floor may be made up 

of a system of minor fault-block ridges, and that the 

"valley block," which on earlier pages has been mentioned as coordinate with the range block, may in fact 

be an elaborate compound of many minor blocks with 

prevalent north-south trend. 

PIEDMONT SCARPS 

The structural data set forth in the preceding sections as proof that a fault creat~d the western face of 

the range are mainly new and receive here 'their first 

publication. They were unknown to those who early 

recognized the fault by lueans of its physiographic features and to those who afterward discussed the physiographic evidence. So as a matter of history they constitute supplementary evidence, and their function 

has been to confirm a conclusion already reached. 

They are here given first place because they are supposed to appeal to the understanding of those geologists whose opinions are little affected by physiographic evidence and the physiographer's reasoning. 

In the following pages I propose to present and dis. 

cuss the physiographic data, not primarily for the 

purpose of adding evidence of the existence of the 

fault but in order to determine if possible the value 

and limitations of physiographic characters as criteria 

for the discrimination of fault-block mountains. 

The alluvial slopes that descend from the rock 

base of the great escarpment are interrupted by small 

scarps or bluffs which are evidently results of dislocation. When these were first observed in the Great 

Basin they were called fault scarps, and in my own 

writings that usage has been continued. By other 

writers, beginning with Russell, the term fault scarp 

. has been used in a broader sense, being applied to 

any escarpment created by faulting; and by one 

writer it has been applied also to escarpments created 

by differential erosion along lines of faulting.31 The 

II Spurr, J. E., Geol. Soc. America Bull., vol. 12, pp. 258-259, 1901. 
34 STUDIES OF BASIN-RANGE STRUCTURE 

dominant usage is that of Russell, and it is properly 

dominant because the term where thus used is selfexplanatory. Having now to write of the phenomena 

to which the name was first given, I feel the need 

of a distinctive designation and have selected" piedmont scarp." I shall use the name to designate a 

scarp that occurs on the piedmont slope and that is 

caused by dislocation. By avoiding the word fault, 

it involves no implication as to the nature of the 

dislocation. 

Except at two' localities the piedmont scarps of 

the Wasatch occur in unconsolidated formations. 

Ordinarily they interrupt the slopes· of the alluvial 

apron, and the faces of the scarps are composed of 

the piedmont alluvium. In a considerable number 

of localities they interrupt either the aiiuvial slopes 

of deltas built at the shore of Lake Bonneville or the 

slopes of the gravel beaches into which the Bonneville 

waves rearrange<\, the material of the alluvial apron. 

At a few localities they traverse glacial moraines. 

In one of the exceptional localities the scarp is at the 

ro.ck base and its face is composed of consolidated 

rock-a fault breccia. In the other it is partly in 

cemented gravel of a Bonneville beach. 

The piedmont scarps are near the rock base and 

approximately parallel to it. In places a single one 

is seen; elsewhere two or more. Where several occur 

they may all face toward the valley or one or more 

may face toward the mountain. Without exception 

the scarp nearest the· rock base faces toward the 

valley, and the net vertical shift of a group of scarps 

is downward on the side of the valley. In many 

places it is evident that the members of a group were 

not all made at the same time. The more recent, as 

a rule, stand at the angle of repose for earth, are sharply defined at the top, and bear only a scant growth of 

bushes; the less recent are less steep, join the normal 

piedmont slope· above by a curve, and are well covered by bushes. These differences are illustrated by 

Plates 17, B; 18, A; 13, A; and 13, B. In several 

places it is evident that two or more movements have 

occurred on the same line. . 

The more recent movement may be indicated by a 

relatively steep slope near the base of a scarp otherwise subdued by long weathering; or the difference 

in date may be shown by the relations of the scarp 

to stream terraces in an alluvial fan or a Bonneville delta. A scarp may fade out longitudinally 

and be replaced by another en echelon, either above 

or below it on the slope. (See pI. 14; A.) Where 

such an offset occurs a strip of alluvium, lying between 

the two scarps, slopes gently and obliquely from the 

alluvial plain above the scarps to the alluvial plain 

below. The relation of the scarps to features' of the 

Bonneville shores and Pleistocene moraines makes it 

possible to say definitely that some are post-Bonneville and postglacial and others pre-Bonneville. 

In some places the alluvial slope is seen to be less 

steep below the piedmont scarp than above it; and 

this is probably a general character. In a few places 

the alluvium close to the base of a scarp slopes toward 

the scarp. These features, which are illustrated by 

Plates 17, B, 15, B, and 15, A, serve to show that the 

amount of vertical descent of the outer block of 

alluvium, considered as a unit, is usually not only less 

than the height of the scarp but less than the vertical 

distance from the base of the scarp to the plane of the 

upper alluvial slope-that is, the measurement of the 

distance a-b in Figure 28 ordinarily gives an overestimate of the vertical displacement of the alluvial 

plain. The maximum apparent post-Bonneville vertical displacement is about 150 feet. The average 

vertical shift for the Wasatch belt of piedmont scarps 

is perhaps one-fourth as great . 

. Where two scarps face each other (see pI. 14, B) it 

is evident that the block of alluvium between them 

has been dropped farther than the valley block. This 

is a phenomenon closely allied to the canting mountainward of tIre upper edge of the lower alluvial 

FIGURE 28.-Profile of piedmont scarp, illustrating measurement of throw 

block, and account must be taken of the two phenomena in any discussion of the origin of the scarps. 

In earlier accounts of piedmont scarps, beginning 

with my own, they have been regarded as the surface 

expression of faults. There is, however, an alternative view which is worthy of consideration-the view • that the movements creating them' are of the nature 

of landslides. The hypothesis that ascribes the 

scarps to faulting assumes that a crustal block under 

the valley is separated by a fault from a crustal block 

in the range, and that a new movenlent has occurred, 

increasing the throw of the fault. The alluvium on 

the valley block has descended with it, all except the 

remnant that adheres to the mountain block. The 

landslide hypothesis ~ assumes no movement of the 

indurated rocks but only a nlovement of superficial 

unconsolidated material. 

The landslides with which we are most familiar 

occur on hillsides and involve a descent of loose surface 

material over a sub terrane of firmer material. Above 

the head of the moving mass is a scarp (pIs. 17, A; 

12, A; and 16, A and B), the surface of the slide near 

its head is apt to be canted toward the scarp, and the 

general surface of the disturbed ground has a gentler 

slope than before the disturbance. A protuberance 

at the lower end is the correlative of the hollow created 

at the upper end. The ground plan of the scarp 
WASATCH RANGE, UTAH 35 

above maybe quite irregular but is likely to be an 

arc, or a series of arcs, concave toward the slide; and 

the scarp about the head of the slide is continuous 

with two scarps that run down the slope and for a 

distance border the sides of the slide. All these 

characters are illustrated by one or another of Plates 

17, A; 12, A; 16, A; and 16, B. 

In connection with a study of the California earthquake of 1906 I examined scores of landslides that 

had been started by the shock. Most of them merely 

started, moving only far enough to open a crack and 

develop a small scarp at the head. Presumably they 

moved during the period of strong agitation-between 

one and two minutes-and came to rest when the agitation ceased. A comparatively small number moved so 

far down their beds that the movement must be 

supposed to have lasted longer than the earthquake; 

and the movement of these had the character of 

flow. 82 They were composed of wet earth. The 

annual climatic cycle of the district in which I examined such slides consists of a wet season and a dry 

season. The earthquake occurred so long after the 

beginning of the dry sea.son t.hat there was little 

water in the ground and none on the surface. In the 

following wet season many of the slides that had 

barely started and then stopped resumed their movement. The views in Plate 16 were made after the 

second movement. It seemed evident that the cracks 

opened by the earthquake had admitted the rain 

water necessary to the progress of the slides. From 

these phenomena I infer that loose material having a 

surface of such moderate slope that it can retain its 

position indefinitely if dry and unshaken may flow 

under gravity (1) if saturated with water or (2) if 

nnd while shaken by an earthquake, and that it will 

be peculiarly fluent when both saturated and shaken. 

In accordance with these laws of earth flow it 

appears possible that' the gravel and sand of the 

Wasatch piedmont nlOve valleyward without the 

occurrence of a local fault slip. At some depth below 

the surface they bear water, and the region is not 

exempt from earthquakes. Thus the landslide hypothesis is not excluded by the qualitative consideration 

of conditions of earth flow. 

The typical form of the piedmont scarp is distinct 

from the forms of the scarps at the head of undoubted 

landslides, but I am not sure that the differences are 

of cruclal character. The greater number of undoubted landslides with which I have direct acquaintance have moved over uneven surfaces-surfaces of 

firm rock under nlan tIes of regolith-and the irregu1arities of their head sca.rp·!:; have been determined in 

part by the unevenness of the slipping surfaces. The 

ordinary landslide is a small unit,. and the lunate form 

U For a classification and general discussion of the landSlides associated with the 

California earthquake see Lawson, A. C., Report of the State Earthquake Investl-

~tlon CommlssJon: Carnegie Inst. Washington Pub. 87, VOl. I, pp. 384-401, 1908, 

of the head scarp is determined by that fact. If the 

piedmont formations of the Wasatch Range have 

moved valleyward under the incitement of an earthquake they have moved in broad bodies and their 

slipping surface has been the smooth footwall of the 

,fault, and it would seem that th~ head scarps thus 

produced might be simply. flexuous. Thus the landslide hypothesis is not definitely excluded by consideration of the forms assumed by the piedmont 

scarps. 

The superficial landslide is usually characterized by 

a bluff ~t its lower end, and the fact that terminal 

bluffs of landslide type are not associated with the 

piedmont scarps of the Wasatch shows that these 

scarps can not be ascribed to the sliding of thip. bodies 

of piedmont deposits. It is conceivable that a shift .. 

r 

u 

~ 

« 

tf) 

« 

~ 

FIGURE 29.-Sketch map of Corner Creek groin, Wasatch 

Range, Utah. C, C, Cliffs of Bonneville shore line; R, R, 

remnants of bay bar of Bonneville shoreline; PS, piedmont 

scarp 

ing of the whole body of valley deposits might occur 

without producing a terminal bluff. It would, however, raise the surface at lower levels and disturb the 

relations of streams to graded slopes, and if the movement were conditioned by the agitation of an earthquake there would probably be a notable ridging of 

the surface. As will be shown later, certain corrugations of the Wasatch piedmont may plausibly be 

ascribed to earthquakes, but they are confined to a 

belt near the base of the range. 

There are two localities in which the Wasatch piedmont scarps admit of no explanation other than that 

of faulting. One is at the junction of the Traverse 

spur with the range, where Corner Creek issues from 

the groin. A post-Bonneville movement on the fault 

is there demonstrated by the dislocation of the highest 

shore line. (See p. 29.) A post-Bonneville piedmont 

scarp follows the base of the range to the edge of the 

eroded valley of Corner Creek, its course being directed 

toward the groin (see pI. 11, A), and it does not 

reappear on the opposite bank of the creek valley, 

which is on the spur. The relations are shown dia-
36 STUDIES OF BASIN-RANGE STRUCTURE 

grammatically in Figure 29. If the scarp had been 

created by a slumping valleyward of the piedmont 

deposits it would appear on the alluvial apron of the 

spur as well as on that of the range. The fact that it 

occurs only along the base of the range connects it 

definitely with the post-Bonneville fault movement 

that is demonstrated by t.he dislocation of the shore 

line. 

The second locality is opposite the Pleasant View 

spur. The modern piedmont apron, composed of 

alluvial fans with well-adjusted slopes, occupies the 

narrow space, half a mile wide, between the r~nge and 

the spur. At the head of the apron is a piedmont 

scarp. It could not have been created by a landslide 

without visible disturbance of the simple profiles of 

the fans but is satisfactorily explained as the result of 

a movement on the frontal fault. 

Among the secondary products of the Oalifornia 

earthquake of 1906 were systems of small ridges. A 

previously smooth mud flat of Tomales Bay was left 

with a corrugated surface, in which the ridges were in 

part parallel to the earthquake fault and in part 

transverse to its direction.33 The ridges stood 1 to 3 

feet above the troughs, and their intervals, crest to 

crest, would be measured in tens of f~et. During the 

agitation the mud, as a quasi liquid, was thrown into 

waves, and the waves were preserved because when 

the agitation ceased the mud became a quasi solid. 

A similar result was observed in a tract within the 

city of San Francisco, where a tide marsh had been 

converted into dry land by a filling of earth.34 The 

111Ud beneath was firmer than that of Tomales Bay, 

and the ridges created -by the vibration were broader 

and higher. Somewhat similar ridges were formed in 

alluvial flood plains, where the ridges were monoelinal and parallel to the stream channe1.35 ·The size 

of the ridges was related to the condition of the 

alluvium: they were small where the alluvium was 

very wet and relatively large where it was drier. 

With these earthquake ridges may be compared 

certain features of the Wasatch piedmont. A short 

distance north of Jump-off Oanyon is a piedmont 

tract of which the general slope is e~cepti6nally low, as 

the rock base of the range is little above the valley 

plain. Piedmont scarps are well'developed, with one 

or two grabens, all parallel to the rock base, and outside these is a wider area in which the alluvium has 

suffered disturbance of a less regular character. Its 

surface is made up of low, broad mounds and hollows, 

arranged without recognized system. Among the 

piedmont scarps are springs, and in some of the hollows are ponds. The ground-water plane must lie 

near the surface, and if the tract were now shaken by 

a strong earthquake its surface might be disturbed 

83 Lawson, A. C., op. cit., vol. 1, pp. 78-79, 1908. 

34 Idem, vol. 1, p. 237. 

~6 Idem, vol. 1, pt. 2, pp. 40Q--401. 

very much as it has been disturbed at sonle time in the 

past. The association of the peculiar topography 

with the frontai fault indicates that a post-Bonneville 

slipping or series of slippings on the fault plane has 

created the piedmont scarps, and that the earthquake 

vibrations caused by the fault movements, acting 

through the saturated deposits of the adjacent plain, 

have created the undulations of its surface. 

The delta built in Lake Bonneville by Weber Rivera huge body. of sand and gravel-has been divided by 

the modern river. The piedmont scarps across the 

two remnants are high and multiple, and anlong them 

are large grabens, which intercept the drainage from 

the range. The scarps and grabens are approximately 

parallel to the range front. On the northern remnant 

there is also a disturbed district just outside the belt 

of piedmont scarps, and in that district the general 

trend of ridges and hollows is at right angles to the 

trend of the range front. The corrugation of the outside district is on a scale comparable with that of the 

belt of scarps; the ridge crests stand 40 or 50 feet 

above the hollows. 

Some of the hollows have caught elements of drainage and been deepened thereby, but not all are thus 

modified, and their forms and relations are such that 

they can not be accounted for as valleys of erosion. 

They appear to be products of dislocation, and the 

only plausible explanation I have been able to suggest 

is that they have resulted from the quaking of the 

delta at a time when movement on the near-by fault 

was creating the piednlont scarps. If this explana-

·tion is correct it applies also to the corrugation of the 

"older alluvium" on the Pleasant View spur, already 

described (p. 25). Although the hypothesis is the best 

now available it is advanced as provisional only. The 

troughs and hollows on the delta and on the spur are 

not wavelike, as were those of Tomales Bay and San 

Francisco .. They suggest, rattier, the breaking of the 

terrane into blocks and the separation of the blocks. 

They approach nlOre nearly, perhaps, the corrugation 

of flood plains by the earthquake, but the flood-plain 

. blocks, which in their separation lurched toward the 

stream channel, were systematically rotated, so that 

their backs inclined in a cOlllinon direction, whereas 

the ridges formed in the Wasatch piedmont are not 

systematically tilted. There is also a difference in 

scale, the Wasatch ridges being much larger than the 

Oalifornian, but that difference is not specially significant, because the Oalifornia earthquake, although of 

high rank, was ilot of the first rank in intensity. If the 

ridges of the Wasatch piedmont were made by an 

earthquake its shock was presumably the most 

powerful that emanated from the frontal fault during 

a very long period. 

The preceding statement of facts and considerations 

bearing on the origin of the piedmont scarps has a 

regrettable prolixity because it is the record of an 
WASATCH RANGE, UTAH 37 

endeavor to free my own mind from an initial bias in 

favor of op.e hypothesis by a thorough examination 

of its rival. When the piedmont scarp was first 

observed in the Great Basin, in 1876, it was at once 

ascribed to movement on a frontal fault, the existence 

of which had already been inferred from independent 

physiographic evidence. During the succeeding decade the same association of characters was found in 

Inany places, and the piedmont scarp was thought, 

especially by Mr. Russell and Inyself, to afford strong 

corroborative eVIdence of °the fault-block theory of 

Basin Range structure. When, therefore, one of nly 

colleagues in discussing the structure treated the evidence of the scarp as "no evidence," and others suggested that the scarp nlight be due to slunlping of the 

piedmont deposits, I was led to suspect that I had been 

overconfident of the credibility of the witness whose 

testimony had so strengthened my preconceptions and 

to. review the subject with special care in later field 

studies. 

It appears to nle now that because at two points on 

the Wasatch front the piedInont scarps can be explained only as direct consequences of fresh movements 

on the frontal fault, the presumption is in favor of 

that explanation for the scarp at any other point. The 

possibility that scarps of the same habitus may be 

produced by dislocation of superficial deposits only 

can not be denied, but at present it is merely an academic possibility. The correlative features that 

theoretically should characterize the distal part of a 

slumping foreland have not been discovered. Moreover, the connecting links between typical piedmont 

scarps and typical landslide scarps have not been 

found. So far as the terms of description are concerned the types may seem to overlap, but in habitusthe ensemble of form detail that so often appeals to 

the eye while it eludes definition-the' types are 

distinct. The Wasatch piedmont region has many 

landslides. The bluffs created by the trenching of 

Bonneville deltas slump toward the trenching streams, 

Bonneville beaches have slid toward the valley, landslides have started from the faces of piedmont scarps, 

and the alluvial mass uplifted on the Madsen spur has 

fallen away in a great series of waves, but the scarps 

created by such surface Inovements can not be confused 

by the physiographer with the piedmont scarps. 

If anywhere there are scarps of the piudmont type, 

silnple in outline and parallel to the rock bases of 

mountain ridges, which have been created by the 

slumping of piedmont deposits, their simplicity of outline has been determined by the simplicity in the contour of the surface down which they have moved. 

Such simplicity of contour may have been acquired 

in various ways, but where it pertains to the part of a 

mountain range buried under the alluvial apron its 

probable mode of origin is by faulting. An alluvial 

SIUHlP that leaves a scarp of the piedmont type presum ably slides on the footwall of a frontal fault;. and 

thus a piedmont scarp, even if directly caused by 

slumping, affords presumptive evidence of the existence 

of a frontal fault. 

On the other hand, I am disposed to regard slumping 

as the frequent or constant accompaniment of the 

making of piedmont scarps by faulting. The earthquake caused by a fault movement is most violent in 

the immediate vicinity of the fault and is a factor in 

the readjustment of the unconsolidated formations. 

Were there no readjustInent the outer 

body of piedmont 

deposits, in moving 

away from the remnant that adheres to 

the footwall, would 

leave a chasm, and 

the filling of that poten tial chaSIn is accomplished at a time 

when the whole mass 

is in a state of agitation. The mobile 

parts· of the mass are 

the more mobile because of the shaking, 

and loose beds filled 

with water behave for 

the time being as 

liquids. The visible 

effect may be restricted to the filling 

of the chasm or it may 

extend much farther, 

and where the piedI 

I 

B 

----------- • I , I 

\ I , 

, 

c 

niont and bordering FIGURE 30:-Diagrams to illustrate thasimpler 

types of piedmont scarps plain are water-logged 

they may acquire undulations of the type observed in 

Tomales Bay. In an account, on an earlier page, of such 

undulations I have mentioned only a locality near Jumpoff Oanyon, because there only is the observed relief so 

pronounced as to be unmistakable, but there are also 

places where the adj acent lake plain displays a pattern 

of marsh and pool, or of dry land and marsh, which 

I think indicative of a relatively gentle undulation of 

similar type .. 

The complexity of the cross profile of the zone of 

piedmont scarps is ascribed in part to the slumping 

that filled the potential chasm, and in part to the fact 

that the scarps made by slips of different dates have 

not always been on the same lines. The principal 

elements involved in the adjustments are shown in 

Figure 30, where diagram A indicates the potential 

chasm, B a filling of the chasm by spreading and 

settling of the outer wall, with reduction of the scarp 
38 STUDIES OF BASIN-RANGE STRUCTURE 

to the angle of rest, and C the separation from the 

outer (or the inner) wall of a slice which settles and 

spreads, producing a graben. The more complex profiles erl.ibit combinations of these elements. In the 

Was,atch piedmont the best opportunities for the 

stuciy of the scarps are found on the Bonneville 

deltas. In general the piedmont slope has lost the 

simple curves of alluvial deposition through modification by wave attack, with the result that the exact 

profiles before faulting are not now evident, but the 

old delta plains of the Provo stage retain their original 

by a bend of the river, has been sapped by recent 

action of the river. Scarp a, first seen in the view at 

the eastern edge of this terrace, follows the edge for a 

space and then climbs the slope, crossing the Provo 

beach. 

Not all scarps and not all parts of the same scarp 

are at the same distance from the rock base. The 

distance is roughly related to the dip of the fault 

plane, being in general relatively great where the angle 

of dip is small. An extreme example is found at the 

base of the City Creek spur, where the dip is 70° and 

E. 

w 

--------------------------------------------~-----------b---~ ~ ~ ~ 

I ·',500 ',000 500 o FEET 

FIG UItE 31.-Profile of piedmont scarps on a delta of the Provo stage of Lake Bonneville at the mouth of Rock Canyon, near the city of Provo, Utah. 1.'he bl'oken line 

is a restored profile of the delta slope before faulting 

slopes, except as modified by later faulting. The 

pr9file shown in Figure 31 was found on a delta near 

the city of Provo and is drawn to scale. The estimate of vertical shift is about 40 feet. Scarp a 

represents two movements, both more recent· than 

those of scarps band c. Some of the small scarps 

outside of a have the same freshness as a, and probably all of them were made by the later movements. 

The sequences were inferred in part from the relations 

of the scarps to alluvial terraces in the valley of the 

stream that has trenched the delta. Figure 32, 

drawn to the same scale, shows three scarps on a wavedressed slope between the Bonneville and Provo 

levels. The presence or absence of scarps at lower 

levels was not determined. At this locality the outer 

b w c~ __________________ ------

I,SOO 1.000 

the distance is 0, and the opposite extreme is found at 

a point on the Mineral Range, where the dip is 19° and 

the distance is about 1,500 feet. Between these 

extremes are the two sides of the black spur near 

Ogden Canyon. By comparing Figure 26 with Plates 

12, B, and 18, .A and B, the reader will see that the 

rock face of the spur is very steep where it meets the 

alluvial apron on the north side and is less steep near 

the southern base, and that the piedmont scarp runs 

much nearer to the north' base than to the south. 

These relations suggested a tendency of the alluvium 

to break apart where it has a particular depth, and 

explanations in the line of that suggestion were considered, but none appeared adequate. They failed, 

in particular, to account for the fact that successive 

E. 

a FEET 

FIGURE 32.-Profile of piedmont scarps near Ogden Canyon, Utah 

scarp, c, was first made, and the inner scarp, a, is the 

most recent. The sag between band c deepens. 

toward the south and has been selected as the site of 

the city reservoir of Ogden. The view in Plate 17, 

B, was photographed from the crest of scarp c and 

shows scarps a and b, with the sag below b in the foreground. Scarps a and b appear also in Plate 8, B, 

and scarp a is there a conspicuous feature. That 

view shows the mouth of Ogden Canyon, with a remnant of the delta built in Lake Bonneville at the 

Provo stage. A stream terrace, carved from the delta 

movements at the same place are likely to form scarps 

at different distances from the rock base, the distance 

for later scarps being in some places the greater, as in 

Figure 31, and in other places the less, as in Figure 32. 

The explanation that accords best with the known 

facts is connected with ground water. The shallow 

edge of the alluvium is not well supplied with water, 

but where the alluvium is deep the lower portions are 

saturated and are correspondingly mobile. The limit 

between a water supply adequate for mobilization and 

an inadequate supply is thought to determine the line 
WASATCH RANGE, UTAH 39 

of parting. The distance of the locus of the limiting 

condition from the rock base differs from place to 

place and from time to time and may be affected also 

by the intensity of the vibration associated with the 

faulting. 

In many places the grabens of the piedmont-scarp 

belt bear undrained hollows in which water stands 

after rains. In a few places the graben troughs have 

intercepted and diverted lines of minor 'drainage. 

The southern remnant of the Bonneville delta of 

Weber River has in this way been deprived altogether 

of drainage from the range, the grabens guiding part 

of the water southward and another part northward. 

I t was probably through such diversion that the tract 

of "older alluvium" on the Pleasant View spur (see 

p. 25) became isolated, although the hypothetic 

grabens are not now to be seen. In 'the position 

ascribed to them is a graded plain, the modern alluvial 

apron, and across the plain, near its upper margin, 

runs a young piedmont scarp. 

The groin between the Traverse spur and the Lone 

Peak salient may have originated in the same way but 

lnore probably was established at the time of the 

eruption of the trachyte that caps the spur. The 

drainage routes of the groin run partly along the line 

of contact between the strong granite of the range and 

the weaker rocks of the spur and partly in the weaker 

rocks on lines parallel to the contact. If their position 

had been determined by erosion alone, the drainage 

streams would either occupy the line of contact, 

shifting gradually down the granite slope, or would 

establish permanent channels in the granite. Their 

partial diversion to channels outside the granite is 

tentatively ascribed to the creation of grabens by 

progressive faulting, but the hypothesis has not been 

tested by determination of the character of the rocks 

along the border. If those rocks are firm-the limestone, sandstone, and trachyte which probably constitute the body of the spur-they might be expected 

to retain continuity iD: moving down the granite 

slope; but if they are unconsolidated-the products of 

decomposition and disintegration-their surface might 

be broken by the formation of scarps and grabens. 

The hummocky topography shown in Plate 10, A, 

suggests unconsolidated material, and Emmons,36 after 

describing the trachyte of the spur, notes that near 

the contact with the granite" there is found a greenishwhite earthy, decomposed rock, in which the only 

traces of crystallization left are white irregular spots 

of partially kaolinized feldspar." 

The relative ages of piedmont scarps are shown in 

part by stages of weathering and in part by relations 

to other features. The most recent have scarcely or 

perhaps not wholly attained the slope of rest. Their 

upper edges are sharply defined, and their faces are 

not fully occupied by vegetation. In those of earlier 

10 Emmons, S. F., U. S. oeol. Expl. 40th Par. Rept .• vol. 2, pp. 440-441, 1877. 

origin the edges are rounded, the faces have gentler 

slopes, and the benches above them have been trenched 

by the drainage, so that the faces are divided into 

facets. On the aprons of other ranges are seen scarps 

in all stages of progress toward obliteration, but illustrations of the more advanced stages are not readily 

to be found along the Wasatch front because the 

greater part of the piedlnont tract has been remodeled 

by the shore work of the waves of Lake Bonneville. 

Below the highest shore line all pre-Bonneville scarps 

have been either obliterated or so nearly effaced that 

their identification is problematic, and the only unquestioned records are those of post-Bonneville dislocations. The fact that none of the post-Bonneville 

scarps exhibit extreme senility indicates that the 

ordinary life of a scarp is longer than post-Bonneville 

time. Fault-block ranges without piedmont scarps 

and also parts of such ranges that lack the scarps have 

presumably felt no paroxysm of growth for tens of 

thousands of years. Of the entire western front of 

the Wasatch about three-fourths is bordered by scarps, 

and the number of separate movements ranges from 

one to at least four, but no post-Bonneville movements 

are recorded for the remainder of the front. The 

longest stretch without piedmont scarps, 16 miles in 

length, lies between points near Willard and Honeyville. From Willard to Brigham the range front is 

smoothly molded, as if composed of rocks that weather 

rapidly, and it is possible that piedmont scarps have 

been les~ durable here than elsewhere; but this suggestion does not apply to the front between Brigham 

and Honeyville, which is bold and rugged. It is not 

to be assumed that the orogenic forces are there dormant, but rather that strains are slowly growing, to 

be relieved at some time in the f~ture by a renewal of 

faulting. 

As scarps of dislocation, distinct in type from 

landslide scarps, piedmont scarps are evidence of 

recent faulting. As they occur on alluvial aprons 

close to the feet of mountain fronts, they are evidences of frontal faults. If simulating scarps may be 

produced by the slumping of piedmont formations 

the characters that constitute simulation are best 

explained by assuming that the slipping surface is the 

smooth footwall of a frontal fault. In the absence of 

steep slope, the probable cause of a piedmont slump is 

earthquake vibra'tion, and the earthquake of highest 

local efficiency is one that originates in a movement 

on the local fault plane. 

SCARPS RELATED TO PIEDMONT SCARPS 

Russell 37 has described a number of scarps in the 

Lahontan basin which are clearly due to dislocation 

but are not so related to mountain fronts that'the title 

piedmont is appropriate. They traverse broad, 

smooth plains occupied by the Lake Lahontan depos17 Russell, I. C., U. S. oeol. Survey MOD. 11, pp. 278, 280-281,1885. 
40 STUDiES OF BASiN-RANGE STRUCTUM 

its, and their faces expose the upper part of the deposits in section. At their bases are thermal springs, 

and in connection with one of them Russell notes a 

til ting of the plain. Two of them run parallel to 

mountain fronts at a distance of some miles; another, 

which crosses an embayed plain, falls in line with a 

piedmont scarp not far away. The thermal springs 

serve to show that the fractures penetrate to a great 

depth. The scarps are the surface expression of dislocations in the rock floor below the alluvial and 

lacustrine filling. Presumably they outline the outcrops of faults in the sub terrane, copying at the surface the deformations of crustal blocks beneath. If 

this interpretation is correct they may properly be 

distinguished from piedmont scarps of the Wasatch 

type, which are caused by crevasses at the heads of 

alluvial bodies that have slid down sloping footwalls. 

In the same' connection should be mentioned the 

scarps created in the alluvium of Owens Valley at the 

time of the earthquake of 1872. On visiting the 

locality in 1883, I referred the scarps without question 

to the Wasatch type, but they have been differently 

interpreted by Hobbs,3s who published an account of 

relatively extensive observations and surveys made in 

later years by W. D. Johnson. The principal scarps 

mapped by Johnson are parallel to the base of the 

Alabama Hills, a small range near the foot of the great 

Sierra Nevada escarpment. With them are many 

minor scarps, and the system of dislocations includes 

a number of large grabens. The displacements have 

horizontal components as well as vertical. P As construed by Hobbs, the individual dislocations of the 

ground, instead of being incidental to the filling of an 

earth crevasse, are surface expressions of distinct dislocations of the sub terrane. This view is supported 

by two special features which I failed to discover but 

which are clearly brought out by Johnson's maps and 

notes. Oertain scarps created in 1872 not only traverse the alluvial fans between spurs of the Alabama 

Hills but are continued on the spurs, and the dislocation of the bedrock is similar in amount to the dislocation of the alluvium. Oertain other scarps, which 

occur at some distance from bedrock, have zigzag 

courses, changing direction abruptly, repeatedly, 

and in a somewhat systematic manner. Scarps 

caused by earth crevasses would not be continued in 

the adjacent bedrock spurs, and the zigzagging of 

alluvial scarps suggests a fault line conditioned by 

peculiarities of structure in the faulted subterrane. 

The Owens Valley scarps, as· interpreted by Hobbs, 

show relationship to the scarps of the Lahontan lake 

plain. They are further related to scarps in alluvium 

that occur in places where the alluvial deposit is thin, 

constituting a veneer on a gra.ded rock plain, and also 

to fault scarps in bare bedrock. As expressions of 

8a Hobbs, W. H., The earthquake of 1872 in Owens Valley, Calif.: Beitr. Geophysik, Band 10, Heft 3, pp. 352-385, 1910. 

bedrock faulting they are more direct than piedmont 

scarps, and they have no necessary connection with 

the growth of existing mountain ranges. 

THE ESCARPMENT 

TRUNCATION OF RIBS 

To the geographer an escarpment is a face, more or 

less wall-like and .more or less elongate, bounding an 

upland. The west face of the Wasatch Range is an 

escarpment. The sculpture of the escarpment has 

elements that are distinct from the sculptural features 

of the body or interior of the range, and those elements 

are connected with the origin of the escarpment. 

A mountain range, considered in its entirety, is a 

ridge, and usually it is composed in large part of minor 

ridges. Some of the minor ridges end at the lateral 

margins of the range, and these, for want of a better 

name, I shall call ribs, thus extending the use of the 

anatomical figure under which an axial ridge is some-

~imes styled a backbone. 

In a general way the western margin of the Wasatch 

Range is defined by the rock base, the line along which 

the bedrock of the mountain disappears beneath the 

alluvium and other discrete formations of the piedmont 

slope. The line of the rock base is essentially also 

the outcrop of the frontal fault and differs little from 

a contour of the fault surface, so that Figures 12 and 

13, which are intended to represent the fault contour, 

serve also to portray the rock base. There are a few 

angles in the outline, but in the main it swings in free 

curves. 

Along this line end the ribs of the range. The base 

line, or rock base, of the end of each rib runs somewhat 

directly from the mouth of a canyon to the mouth of 

the next canyon. It has indeed some curvature, but 

the curvature is part of the general curvature of the 

range base and has no relation to the character or 

size of the rib. It is concave toward the valley in as 

many places as convex. To express this character 

briefly, we may say that the'rib ends are alined. 

. Above the base line the contours of rib ends tend 

toward alinement, but the tendency is not equally 

strong in all parts of the range front. It is favored by 

uniformity in the character of the rock and is especially favored by the power of the local rock to resist 

erosion. Under favorable conditions each higher contour of a rib end is parallel to the contour at the base 

line and is alined with the corresponding contours of 

neighboring rib ends. A row of rib ends in such a 

locality seem to' be parts of a once continuous plane 

or gently flexed surface, the outer surface of an original 

great rock body out of which the canyons have been 

carved. Or, as an alternative conception, we may 

imagine that the ribs once ran farther valleyward but 

have been cut away-truncated-as by a single stroke 

of a gigantic blade. Ribs that end thus are appro-
U. S. GE OLOGICAL SURVEY P R OFESSIONAL P APER 153 PLAT E 19 

A. WEST SIDE OF LONE PEAK SALIENT 

The Caeels are parl of a once continuous surface lhat has been dissec t.ed by t.he erosion of canyons. The principal roc k is granit.e. but rela tively weak schis t a nd relatively strong qua rtzite occur in t he lower pa rts of the face. The difl'erences of rock streng th find lilUe expression in the configura tio n of the facct.s 

B. VIEW SOUTH OF PROVO 

At the left is Slate Canyon. The principal rock is limestone. The slr"uc ture includes an anticHne. with axis somewhat. ohlique to the range front. Of the strata trunca t.ed by the facets, some dip with Lhe slope bu t more s teeply, others dip with the slope but less s teeply, and others dip away from the face 

FACETS OF THE WASATCH ESCARPMENT, WASATCH RANGE, UTAH 
U. S . GEOLOGICAL SURV.I,Y PROFl'SSIONAL PAPER 153 PLATE 20 

A. GENERAL VIEW j<' flOM PItOVO 

The faceted escarpmcn l is the face of a subsidi ary ridge of the Wasa l eh n.ange. The crest of the ridge descends northward toward Provo Can- yon , at the left.. A t. the ri g-hl of the centol' is n ook Canyon. The principal rock is limestone, but. there arc smaIL outcrops of quartzite 

a nd shale. The general dip is eastward and genUe, but a ll abrupt a nlicli ne is exposed near the bases of the nearer faceLs. (See figs. 4 a nd 5) 

B. DETAILS AT ROC K CA YON 

The struc ture at this point is shown by F igure 5. It is truncated by the smooth facet. In Lhe distance is Timpanogos Peak 

FACETS OF TIlE WASATCH ESCARPMENT NORTH OF PROVO, UTAH 
U . S . GE OL OGICAL SURVEY P R OFESSIONAL P AP E R 153 P L AT E 21 

A . N EAR J3ATTLE CREEK 

Lower ridge runs pa ra llel to the m u ill ridge of Lhe Wasa tc h Ha ngc, as shown in Figure 44 .• a nd streams cross this in V-sectio n canyons. Tile facets of Lhe escarpment mee t. the canyo n walls in well-defined corners 

The lower ridge m enlioned und er A is divided b y American F ork Canyon. t.he wa lls of which ha ve a different. sculpLurc from tha t of the faceted fro nta l f acc. The faceL a t the left of the canyon has lost its original surface by wea thering, a nd the rock struc ture trun- ca ted by the frontal escarpment is thus revealed 

FACETS OF THE TrMPANOGOS FHONT, WASATCH RANGE, UTAH 
U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 22 

A. WASATCH ESCARPMENT OPPOSITE WILLARD, UTAH 

The view illustra tes the obLique trunca tion of structure by the pLane of the ra nge frout. The broad pale band marks tbe outcrop of the Cambrian quart.zile. which descends from right. to left, reaching t.he base line of t.he front.. just. outside t.he view. Below it. is Archean gneiss, with tnpering exposure. Plate 7, B, shows t.he same features from 8noLhcr direct.ion 

' , --. . _-- :;, .... :::--. '-

B. BONNEVILLE SHORE LINE NEAR TOOELE, UTAH 

The escarpment produced by wave erosion truncates rock ribs of Lhe Oquirrh Range, as well as the allu vial apron. ParL of Plate 9, iVlonograph I, from a drawing 

by F. D. Owen 
U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 23 

A. ESCARPMENT ON SOUTH FORK OF OGDEN RIVER, UTAH 

T hese triangu lar facets were developed by the migration of a stream valley down the dip of gently inclined strata. Photograpb a nd description by Eliot Blackwelder 

B. ESCARPMENT ON KERN RIVER, CALIFORNIA 

The facets are features of a bluff made by a meander of Kern River, which has developed a flood plain 1 mile wide 

FACETED ESCARPMENTS MADE BY STREAM EROSION 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 24 

A. WASATCH ESCARPMENT OPPOSITE PLEASANT VIEW SPUR 

T he peak, Ben Lomond, is made up of limestone, and the escarpment shows Cambrian quartziLe above Archean gneiss 

B. HIGH-LEVEL GRADE PLAINS 

The grade plains slope from lefL Lo righL in the region of the snowdrifts. The portion of the range on which Lhey lie is just south of Weher Canyon 

VIEWS IN WASATCH RANGE, UTAH 
WASATCH RANGE. UTAH 41 

priately called trunc.ate without any implication as 

to the origin of their forms, and a range front characterized by the terminal facets of truncate ribs is 

appropriately said to be faceted. 

Examples of faceting are shown in Plates 19 and 20. 

Plate 19, A, presents the western side of the Lone 

Peak salient, where the rock is an exceptionally resistant granite. In the Provo division of the range, 

illustrated by the other views, the rocks are sedimentary and mainly calcareous. It will be noted that 

the facets are best preserved near the base and have 

suffered from erosion higher up. Plate 14, A, shows 

a large facet the erosion of which, in ways analyzed 

by Davis,39 has resulted in the production of subsidiary facets that have a tendency toward triangular 

forms. Facets in more advanced stages of dissection 

an.d demolition are shown in Plates 7, B; 9, A; and 

25, A, and the profile of a well-preserved facet appears 

in Plate 4, B. Quadrangular facets appear in Plate 

21; and the nearer facet in Plate 21, B, shows a partial dissection that has been promoted by diversity of 

rock texture. 

TRUNCATION OF CANYONS 

The canyons of the range, except as modified by 

Pleistocene glaciers, have steep walls and narrow beds. 

Those that debouch on the western side hold these 

characters to the face of the escarpment. Where the 

rocks are strong the walls are specially steep and crags 

abound; where the rocks are weak the walls are steeply 

graded. The degree of narrowness of the beds also is 

related to rock characters. Whatever the nature of 

the rock the narrowness of bed continues to the rock 

base and there ends abruptly. Where the rocks are 

strong the canyon walls hold their character and direction to the range front and there meet the facets of the 

escarplnent in well-defined angles. This feature is 

strikingly illustrated by Plates 4, B; 8, B; 19, A; and 

21, A and B, and is shown also by Plates 19, B, and 20, I 

A and B. Where the rocks are weak there is more or less 

blending of canyon walls and frontal facets, except at 

the rock base. Where the rocks are of unequal strength 

all other expression may be masked by differential 

weathering. 

The general fact, which receives its full expression 

in strong rocks, is that the canyons hold their character 

to the plane of the facets and there lose them. In the 

saIne sense in which ~he ribs are truncate the canyons 

are truncate. 

TRUNCATION OF STRUCTURAL FEATURES 

Within the body of the range are folds and faults. 

The strikes of dipping strata and the strikes of faults 

are in general not parallel to neighboring parts of the 

western escarpment but meet it at some angle. For a 

few miles north of Brigham, for a few miles south of 

19 Davis, W. M., Harvard Coll. Mus. Compo Zoolog~ Bull., vol. 42, p. 151, 1903. 

62436-28-4 

Willard, and for a few miles north and south of Provo 

Canyon the strike of the strata is approximately parallel to the rock base, but these localities are exceptional. Elsewhere, including not less than seveneighths of the range front, the strike meets the rock 

base at a notable angle. The greatest fold of the 

range, a syncline that brings a great series of Paleozoic 

and Mesozoic formations in succession to the rock 

base, runs athwart the range in the latitude of Salt 

Lake City. As already described, the basal quartzite 

of the Cambrian comes obliquely to the rock base at a 

number of different points, its outcrops at the several 

localities belonging to distinct tectonic blocks. The 

outcrop of the Willard overthrust is intersected by the 

range' front, and in the Ogden region normal faults of 

great displacement meet the rock b~se at right angles. 

All these elements of structure appear in section in the 

range front. 

The obverse of these facts is that the line of the 

range base crosses the strike lines of the structure at all 

angles. The range front transects the range structure. 

The structural features that are exhibited in section 

in the range front are truncate, just as are the features 

of relief. 

Davis 40 illustrates the transection of structural fea--

tures by a sketch of the range front near Mona and 

points out that certain ridges and canyons developed 

on the outcrops of strong and weak strata are obliquely 

cut off at the line of the rock base. Plate 22, A, shows 

an outcrop of Cambrian quartzite as it obliquely 

descends the mountain face near Willard, and the 

same descent is p'ortrayed in Plate 7, B. Plate 7, A, 

with its explanatory diagram, Figure 11, shows also the 

oblique outcrop of the Willard overthrust. In Plates 

2, A, and 3, B, are seen strata on edge that lneet the 

line of the front at right angles; and a similar relation 

is illustrated by the nearer facet of the view in Plate 

21,·B. 

INTERPRETATION OF TRUNCATION 

COM.PARISON OF WASATCH ESCARPMENT WITH ESCARPMENTS NORTH OF THE GRAND CANYON 

Men are prone to take the familiar as a matter of 

course and to ask the meaning of the strange only; 

and by our manifestation of this trait we geologists 

are assured of our humanity. To one who has lived 

solely in a glaciated region the forms of landscape 

peculiar to ice erosion suggest no mystery, and it is 

only through acquaintance with the dOlninant topography of aqueous origin that he is able to recognize the 

strongly marked characteristics of the work of ice. 

The illustration is drawn from personal experience, 

but its moral finds support in the circumstance that 

those who have undervalued the power and aCCOlnplishment of glaciers have been dwellers in lands once 

overrun by Pleistocene ice sheets. It has occurred to 

40 Davis, W. M., Harvard ColI. Mus. Compo Zoology Bull., vol 49, pp. 20-21, 1905. 
42 STUDIES OF BASIN-RANGE STRUCTURE 

me, as I wrote of the phenomena of truncation, and 

especially the truncation of canyons and of structural 

features, that such phenomena may be so familiar as 

features of mountain fronts that not all students of 

orogeny feel the need of their explanation, and I shall 

therefore preface a consideration of the' meaning of 

truncation by a brief account of a group of escarpments 

whose characters stand in contrast. 

From the brink of the Grand Canyon of the Colorado the general surface rises northward for 75 miles, 

but it does not rise in a simple, continuous slope. 

The ascent, as described by Powell 41 in one of the 

classics of physiography, is a stairway. The tread of 

each stair slopes gently northward, and the riser of 

each stair is an escarpment that faces towarcl the 

canyon. The rocks are stratified and dip northward 

at a low angle, and discriminative erosion has brought 

the stronger members of the series into topographic 

prominence. The northward slopes are on the bared 

tops of strong beds; the escarpments exhibit the edges 

of the same beds, sapped by the wasting of underlying weak beds. The general direction of drainage is 

southward to Colorado River. Each major stream 

traverses the strong beds in canyons, but between the 

canyons it has a wider valley. Minor streams, wetweather streams, head in the escarpments and join 

the major streams. Each canyon broadens downstream, flaring widely as its stream leaves the strong 

bed. The head of each minor stream is in a reentrant 

angle of an escarpment. The outline or ground plan 

of each escarpment is a series of convex scallops, large 

and small, the larger scallops spaced by the major 

drainage and the smaller by the minor drainage. The 

canyons and gullies of the drainage correspond to the 

canyons of the Wasatch front, and instead of being 

truncated at the basal outlines of escarpments they 

determine reentrants of the escarpments. The ridges 

between lines of drainage correspond to the ribs of 

the Wasatch, and instead of being truncated along the 

bases of the 'escarpments they determine the salient 

scallops of the escarpments and their bases. 

The district is crossed by faults and monoclinal 

folds, which trend in the direction of the general dip 

and are thus transverse to the general trend of the 

escarpments. In one place two monOclinal folds are 

so related as to constitute an' anticline. The escarpments met by this anticline are deflected far to the 

north, swinging in great reentrants 25 miles from their 

normal courses. They are thus deflected because 

their positions are determined by the conditions 

affecting erosion and because the elevation of the 

cliff-making beds in the anticline exposes them to 

more active erosion. A cognate deflection is found 

41 Powell, J. W., Some remarks on the geologic structure of a district of country 

lying north of the Grand Canyon of the Colorado: Am. Jour. ScL, 3d ser., vol. 5, 

pp. 456-465, 1873. 

wherever an escarpment is cro§sed by a fault or a 

monoclinal fold. The escarpment is advanced on the 

side of the down throw and carried back on the side 

of the upthrow. 42 The Vermilion escarpment is offset 

by the Sevier fault through a space of 7 or 8 miles and 

by the East Kaibab fault and fold through about 

32 miles. Thus such structural features as faults and 

folds, instead of being truncated by the escarpments, 

serve as important factors in the control of the courses 

of the escarpments. 

The control of the forms of these escarpments by 

elements of structure and by elements of drainage 

pattern is effected mainly through processes of stream 

erosion, and it is a general fact that the forms of 

escarpments created· by stream erosion are largely 

controlled by the structure of the eroded terrane and 

by the pattern of its drainage. Because flowing water 

is the dominant agency in the sculpture of the land, 

the form types it produces constitute the norm, and 

departures from its types call for explanation. When, 

therefore, so important a form element as the basal 

outline of an escarpment is found to be independent of 

the rock structure, independent of the drainage pattern, and independent of the distribution of intercanyon ridges (distribution which is of course a function of drainage pattern), so that the basal outline 

appears to cut off or truncate these features, the 

phenomenon is one requiring explanation. 

For the Wasatch escarpment the explanation is at 

hand, because the base line of the escarpment is also 

the line of a great fault, characterized by an abundance 

of the phenomena created by fault friction and followed 

through long distances by piedmont scarps. The 

escarpment· is evidently the face of an uplifted tectonic 

block, and the adjacent depressed block is buried under 

waste from the sculpturing of the uplifted block. The 

structural elements of the uplifted block end at the 

fault line because they were actually cut off by the 

faulting. The ribs end where the block frOln which 

they were carved ends. The canyons also end where 

the block ends, and they end without flaring because 

the upfaulting was too rapid to give their streams time 

for lateral corrasion. 

If faulting affords the only admissible explanation 

of the phenomena of truncation, then all ranges whose 

fronts are truncate may be classed at once as faultblock mountains. If the phenomena of truncation 

may be produced also in other ways, then truncation 

alone, although suggesting fault-block structure, is 

not demonstrative. In considering the question thus 

arising attention should be givento the several natural 

agencies or processes, other th~n faulting, that are 

known or supposed to produce escarpments. These 

are volcanism, ice erosion, wave erosion, wind erosion, 

and stream erosion. 

42 Idem. pp. 461-462, 
WASATCH RANGE, UTAH 43 

VOLCANIC ESCARPMENTS 

The inward-facing wall of an ordinary crater is an 

escarpment created by explosion. The Krakatoa 

explosion made an escarpment by blowing out the 

side of a volcanic cone. The inner walls of Hawaiian 

craters are escarpments due to engulfment. N one of 

these types need be considered here because their 

forms do not reselnble mountain ridges of the Great 

Basin. For a sinlilar reason the mention of several 

minor types may be omitted. 

The edge of a coulee, or streaJll of soli9.ified lava, 

though ordinarily a very low escarpment, is exceptionally of such size as to deserve attention in the present 

connection. The eruptive plateau of the Mono craters, 

for exmnple, is bounded by an escarpment 500 to 

1,000 feet high; and the faces of the effusive portion 

of the Mount Elden dacite body, which Robinson 43 

has shown to be part laccolith and part coulee, are 

2,000 feet high. 

A coulee is a single body of rock; it is a bed but is 

not composed of beds. So one character of its escarpment is the lack of such structural elements as are 

necessary to exhibit truncation of structural features. 

Initially the coulee lacks surface drainage because it 

is penetrated by a plexus of shrinkage cracks. By the 

time it has acquired surface drainage and canyons 

have been opened in it the original definition of its 

escarpment has been dimmed by weathering, but 

there is a stage of dissection in which canyons and 

residual ribs end along a line of rock base, so that the 

features of internal structure are truncate. It is 

therefore possible that an escarpment that is composed 

of unbedded lava and that exhibits truncation of 

sculptural features originated by a purely volcanic 

process. 

Coulee-edge escarpments of the magnitude of mountain ranges are rare, but high escarpments composed 

wholly or mainly of volcanic rock are not rare. An 

escarpment that shows two or more lava beds can not 

generally be regarded as an original product of eruption, because of the improbability that a free-flowing 

lava stl'el1ln in spreading over an earlier stream should 

stop at the same line. Superposed lava flows that are 

halted by a barrier, however, may have a common 

limit, and an escarpment may afterward be created by 

the erosion of the barrier. Lavas that rest on weaker 

beds may be brought into strong relief throuo-h the 

erosion of bordering land's and thus become th~ conspicuous elmnents of escarpments, and lavas, like other 

rocks, 11lay compose fault scarps. 

ICE~ADE ESCARPMENTS 

The U valley of glacial sculpture is bounded by 

~nural escarpnlents that truncate tributary valleys, 

Intervalley ridges, and structural features of the ter41 Robinson, H. H., 'l'he San Franciscan volcanic field, Arizona: U. S. Geol. 

Survey Prof. Paper 76. pp. 74-85, 1913. 

rane. Among the truncated valleys are many hanging 

valleys, whose m'ouths are high on the walls. The 

contours of the escarpments, may be as simply curved 

as those of a fault, surface but differ in that they are 

not wholly independent of truncated valleys and ribs. 

Other resemblances and differences might be pointed 

out, but it will suffice to say that the characteristics 

of ice sculpture are so well known that a hypothesis of 

glacial sculpture need not be considered in a discus-

~ion of frontal escarpments of Basin ranges.' The 

mtermont troughs were her.e and there invaded in the 

~leistocene epoch by tongues of alpine glaciers, and . 

In a few places piedmont glaciers nlay have been 

developed, but ice-sheet conditions were not approached, and none of the troughs were traversed by longitudinal ice currents. 

WAVE-MADE ESCARPMENTS 

.Erosion of a coast by waves creates an escarplnent 

WIth all the features of truncation. Structural features are truncated, ribs are pared away until their 

ends are truncate and alined,· inter-rib valleys· and 

canyons are Inade to debouch at the comnlon line 

of truncation, and the resulting base line of the escarpment is simply curved. These are the results of 

long-continued wave attack, and they should perhaps 

be characterized as ideal because no example of a 

finished coastal escarpment can be cited. In the 

coasts, recent and fossil, 'of my acquaintance the work 

is unfinished. There are stretches, some of them long, 

of perfected escarpment, but there are bays whose 

shores are protected from wave attack by wave-built 

barriers, and there are obdurate ribs not yet reduced 

to the scheme of alinement. 

All these characters are exemplified by the Bonneville shore line, and some of them by the illustrations 

of this paper. Plate 1, A, shows a piece of perfected 

coastal escarpment-perfected, that is, at the time 

of its 'making and still preserving its main features. 

The rib facets are alined, and they rise from a base line 

that is simply curved. The canyons, which once ended 

at the same base line, have been extended as gullies 

by recent work of their streams. The facets of the 

wave-nlade escarpment, which stand at the angle of 

earth slope, have been carved from the less steep facets 

of an older escarpment. The older escarpment a 

fault scarp, is thousands of feet high, and the wa~e­ made facets are a few hundred feet high. The perfection of the wave-wrought alinement depends in 

this case on the fact that it has been superposed on 

a perfect fault-made alinement. Plate 22, B, portrays another piece of perfected shore escarpment 

in which the facets of truncation are in part on rock 

ribs of a Basin range and in part on flat-topped ribs 

Inade by the dissection of alluvial fans. The higher 

facets and the lower, those on bedrock and those on 

alluvium, are aiined in the same simple curve. The 
44 STUDIES OF BASIN-RANGE STRUCTURE 

map in Figure 33 shows a piece of protected and 

unscarped coast between two portions truncated by 

wave attack. Waves of efficient size reached this 

tract of coast from the northwest and from the southeast. The waves from the northwest carved out a 

westward-facing escarpment and drifted the debris 

southward; the waves from the southeast carved a 

southward-facing escarpment and drifted the debris 

westward; and their work produced embankments of 

coarse debris by which the intervening coast was 

the upper edge of the alluvial apron, which is controlled 

by a Il:umber of conditions. The base line of a coastal 

escarpment lies initially in a horizontal plane but may 

afterward lose horizontality through deformation and 

dislocation. 

The size and therefore the efficiency of waves are 

related to the width and depth of the water body on 

which they are generated. Lake waves are weaker 

than ocean waves, and the waves of a lake in the bottom of an intermont valley are feeble as compared to 

FIGURE 33.-Map of Bonneville shore escarpment and shore terraces near Dove Creek, Utah. Scale, 1 inch= 1,600 feet. Contour interval, 10 

feet. (Part of pI. 22, U. S. G~ol. Survey MOD. 1, 1890) 

sheltered. The embankments stand at different levels, 

corresponding to different positions of the lake surface. 

The protection of bay coasts is further illustrated 

by the sketch map in Figure 29. The waves of Lake 

Bonneville did not carry their work of erosion into 

the Corner Creek Bay but built a curving bar in front 

of it. The whole physiography of coasts shows that 

waves do not erode in angular reentrants of coast 

lines, and it follows that such reentrant angles of the 

Wasatch escarpment as that at Taylor Creek (fig. 14) 

could not be made by wave erosion. 

The base line of the escarpment made by a frontal 

fault lies in the plane of the fault and may have any 

relation to a horizontal plane. It rises and falls with 

those of Lake Bonneville. The waves of Lake Bonneville have in places steepened the Wasatch escarpment at certain levels, but it is evident that the 

scarped front of a Basin range could not be created by 

lake waves, because intermont lake waves are inefficient at low levels. 

Coordinate with erosion by lake waves is deposition 

on lake bottoms, an9. the volum!l..,of lake deposits is 

much greater than the volume orrllaterial moved by 

lake erosion because the deposits include also debris 

brought by tributary streams. Lakes are thus fillers 

of intermont valleys and can not either make them or 

aid in their making. They have had no part in t.he 

creation of the corrugation of the Great Basin. 
WASATCH RANGE, UTAH 45 

Because wave erosion truncates structure awl sculpture there lllay be examples of truncation in the Great 

Basin which are wholly attributable to waves. The 

gl:eat exanlples, howev~r, have been createu along 

wIth the corruga tion of the province and are therefore 

independent of wave work. I find no reason to regard 

the lnodification of escarpments by lake waves as of 

quantitative importance. The relative magnitude 

of the work of Pleistocene waves is fairly expressed by 

the contrast shown in Plate 1, A, between wave-made 

ffl.cets and the preexistent facets from which tpey we:r;e 

carved. The work of Pliocene and Miocene waves can 

not be evaluated in the same way, because the Tertiary wave scarps have not been recognized and are 

probably worn beyond recognition. 

WIND-MADE ESCARPMENTS 

It is the opinion of I{eyes that in the more arid parts 

of the Cordillera truncate escarpments are produced 

by wind erosion. His view is that although stream 

erosion dominates within· the ranges, causing dissection, wind erosion dominates in the intermont valleys, 

causing planation; that the valley floors are being 

lowered and leveled by deflation; that the lowland 

plains encroach on the mountains by eolian lateral 

corrasion; and that by this lateral corrasion mountain 

fronts are sapped at the base, steepened, and straightened, so as to have a deceptive resemblance to fault 

scarps. 

Such degradation of desert plains should produce 

tracts of planed rock, with little waste on the surface. 

Such lateral corrasion at mountain bases should produce piedmont slopes with rock floors. The eolian 

theory finds support not only in the existence of such 

rock floors but in the fact that they abound especially 

in a very arid belt across the southern parts of New 

Mexico, Arizona, and California and are comparatively 

rare in northern parts of the Great Basin, where the 

climate is less arid. 

This support is qualified by another factor of distribution-that rock-cut plains occur chiefly in 

regions of exterior drainage and are rarely found in 

closed basins. Their rarity in closed basins may 

indicate that deflation does not there keep pace with 

the aqueous deposition of waste from surrounding 

uplands; their relative abundance in regions of exteriOl' drainage points to aqueous transportation as 

the efficient means of removing waste. 

Whatever the local conditions in our desert regions; 

it is evident that in a district of extreme aridity eolian 

agencies must dominate, and there is advantage, 

therefore, in considering the probable result of dominant wind work in the shaping of mountain fronts. A 

wind blowing against a·mountain face and up its sloJ>e 

is somewhat checked against the rib ends and strength-· 

ened at the cany~:m mouths, Its erosive wori( has a 

corresponding distribution and tends to preserve fea 

tures of aqueous sculpture instead of truncating them. 

A wind blowing down the slope finds tools for corrasion 

only in the hollows and corrades only there. A wind 

parallel to the front behaves somewhat like an ocean 

current parallel to a coast; it makes eddies of low 

velocity in the bays and is accelerated against the 

capes. It is strongest high on the capes but does not 

corrade there for lack of tools. Its most efficient attack is at and near the bases of rib ends, and it tends 

to truncate the ribs. The work of oblique winds and 

of variable winds shows intermediate characters. It 

is probable that a wind truncation comparable with 

truncation by faulting can be accomplished only by a 

wind of fixed direction and is not ordinarily possible 

to cyclonic winds. 

The foregoing statements, although largely deductive, have been guided in part by observations of 

eolian corrasion in three localities where the direction 

of efficient winds is controlled by local configuration. 

The observations most in point were made along the 

base of the Shinarump cliff, near the head of Marble 

Canyon, in northern Arizona. The cliff exposes 

sandstone at the top and sandy shale below. The 

only strong winds that carry sand for corrasion blow 

from the southwest, parallel to the general trend of 

the cliff. The cliff base is not straightened but has 

reentrants and salients adjusted to the drainage 

system. The wind has blunted the salients and keeps 

their ends free from talus, but the shale slopes in the 

reentrants are covered by talus. 

Unfortunately the mountains cited by Keyes as 

~xamples have not been adequately mapped, and he 

Illustrates their characters only by diagramm~tic 

sections. 

Before the development of the eolian hypothesis 

McGee 44 wrote of the rock-cut plains of the Sonoran 

deserts and ascribed them to a special typ; of water 

action which he called sheet-flood erosion. After the 

development of McGee's hypothesis Paige 45 discussed 

the rock-cut piedmont plains of the Silver City quadrangle, in southwestern New Mexico, and ascribed 

them to normal stream erosion. ~aige's study had the 

advantage of such comprehensive knowledge -of local 

structure as is acquired in the preparation of a folio 

of the Geologic Atlas and a further advantage arising 

from the fact that one of the plains studied has been 

dissected in consequence of a recent local uplift. The 

dissection has revealed the fact that the alluvial 

mantle of the beveled rock surface, although a mere 

veneer near the mountain base, thickens valleyward; 

and this character indicates that the retreat of the 

mountain front and the concomitant development of 

U McGee, W J, Sheet-flood erosion: Geol. Soc. America.Bull., vol. 8, pp. 87-112, 

1897. . 

f5 Paige, Sidney, Roc~-Cqt sqrrac~s iq th~ d~~ert ran~es: Joqr. Geolosr. vol. 20, 

Pl'" 442-450, 19l~, • 
46 STUDIES OF BASIN-RANGE STRUCTURE 

the rock-cut plain at its base had been accompanied 

by aggradation in the valley. More recently Lawson 46 

has included the profiles of rock-cut piedmonts in a 

general analytic discussion of the profiles developed 

under desert conditions. His views are in accord with 

those of Paige, and he assigns only a minor part to the 

wind. 

0,-. _-'--_-'------''-----'-_--'~ MIL ES 

structure and mountain sculpture I think the eolian 

hypothesis will find application, but its application 

has not yet been shown by the reports of adequate 

studies. 

It is proper to observe that the association of a 

truncating escarpment with a rock piedmont does not 

necessarily indicate eolian erosion unless the rocks of 

the escarpnlent are continuous with those of 

the piedmont. The association may' be created by faulting and then the rocks are not 

continuous . • The production of an escarpment by sapping 

FIGURE 34.-0utlines of mountain escarpments where joined by rock-cut piedmont plains, 

Silver City quadrangle, N. Mex. (After Paige) 

implies the preexistence of a mountain front. 

The sapping does not create the differentia.-

tion of upland from lowland but modifies the 

form and position of the sloping face by which 

they are separated. The question considered 

in this section is not that of range origin but 

only that of the value of the truncating escarpment as' a character to be used, in the 

nition of fault-block ranges. 

In three of Paige's illustrations the outline of mountain base resulting from the development of the rockcut piedmont is charted, and I have reproduced these 

outlines ill Figure 34. It will be observed that the outlines have not the general appearance of the basal 

outline of the Wasatch escarpment but are relatively 

indentate. Examination of the contour map on which 

these outlines were drawn shows that their reentrants 

and salients, instead of being independent of the 

mountain sculpture, are in close accord, severally, with 

the drainage lines and ribs of the mountain. So t.he 

escarpments, whatever their relation to the structure, 

do not trunc'ate the sculptural features of the mountain. Moreover, the ends of salients have not such 

ail alinement as would be expected if their positions 

were determined through lateral' corrasion by currents parallel to the general trend of the escarpments. 

In a fourth illustration, which I reproduce in Fig- . 

ure 35, Paige gives the complete outline of the rock 

base of a range that is bounded on one side by a fault. 

On the side of the fault the outline is direct and simple, 

despite' complexity ,in the internal structure of the' 

range; structure and sculpture are truncate. On the 

opposite side the outline is tortuous. 

The question whether some escarpments of desert 

ranges are of eolian origin will be settled by future 

. field studies but appears for the present to be open. 

The observations of McGee, Keyes, and Paige agree in 

indicating that the fronts of certain desert ranges 

have been steepened by some erosive process or processes, with the concomitant development of a rockfloored piedmont. The inden ta te escarpmen ts described 

by Paige seem best explained as a product of erosion 

that is mainly aqueous. If it shall be found that some 

of the escarpments made by erosion truncate both 

.1 Lawson, A. C., The epigene profiles of the d~er~: C~ifQfP.~~ Vntv. Dept. 

Of}ology Bull., vol. 9, pp. ~3-i8, ~9~5. 

STREAM-MADE ESCARPMENTS 

Strike escarpments developed by streams from 

bodies of dipping beds, including cuesta escarpments 

and escarpments like those north of the Grand Canyon 

(p. 42), are not considered in the following paragraphs, 

but only escarpments that traverse the strike of strata, 

folds, and faults. 

A rapidly corrading stream in carving its gorge 

creates two escarpments. Tributary gorges divide 

each escarpment in to 

facets. The facets 

are parallel to the 

stream that establishes their base lines. 

Each e.scarpment 

truncates the tributary gorges and in tergorge ridges. If the 

course of the streanl 

is transverse or oblique to the strike of 

the structure, each 

escarpment truncates 

structural features. 0,-. -'---'----'-f ____ 1Miles 

N 

i 

Thus an 0 r din a r y FIGURE 35.-0utline of the Little Burro 

Mountains, N. Mex., stiow(ng the bound· 

canyon wall is a trun- sry between the bedrock of'the range and 

cating esca rpm en t , the surrounding alluvial apron. (After 

Paige) with Inany 0 f th e 

characters of the frontal escarpment of the Wasatch. 

It mayor may not have a simply curved· basal outline. It differs primarily by having a counterpart 

close by. The carving of a gor.ge may be regarded as 

thg initiation of a stream valley. Under stable con ... 

ditions of base-level downward corrasion first slackens 

and th~lQ ce~$es, and it is gradually repl~ced by lateral 
WASATCH RANGE, UTAH 47 

corrasion. Flood plains are developed, and the canyon walls recede. 

A conceivable method of producing the frontal 

escarpment of a Basin range begins with the carving 

of a canyon parallel to the range axis and continues 

with the broadening of the canyon until it becomes an 

intermont valley. Another conceivable method begins 

with a river meandering in a broad plain above the 

present site of an intermont valley and continues with 

a downward erosion by the river so slow as to involve 

no canyon phase. 

The river work, by either hypothetic lnethod, 

carries the valley floor below its present level and is 

followed by the work of minor streanls, which partly 

fill the eroded valley with deposits of waste from the 

bordering ranges. Before the disappearance of the 

hypothetic intermont river the mountain streams were 

tributary to it, and while the river was eroding the 

nlain valley the mountain streams were eroding canyons and narrow valleys. When a sloping alluvial 

deposit is afterward built up along each edge of the 

main valley it necessarily occupies also the lower parts 

of the lateral valleys and canyons. The resulting line 

of the rock base of each range is therefore a zigzag, and 

its reentrants and salients correspond severally to the 

canyons and ribs of the range. So a frontal escarpnlent created by an intermont river and modified, 

after the disappearance of the river, by partial burial 

does not truncate the sculptural features of the range. 

The erosive activity of a mountain strealn is conditioned by a base-level outside the mountain. When 

a change in the relation to base-level checks its downward corrasion the influence is first felt in the lower 

course, so that lateral corrasion goes on near the canyon mouth while vertical corrasion still persists farther 

up. The result is a flaring of the canyon mouth. By 

the widening of a series of canyon mouths the intervening ribs are pared away and the canyon floors are lnade 

to coalesce in a piednlont plain of rock. This process 

is an influential factor in the sculpture of mountain 

fronts in arid districts, as analyzed by Lawson, and is 

essentially the process to which Paige ascribes the 

rock-cut piedmonts of the Silver City area. The 

escarpment thus produced is indentate. 

SUMMARY AND CONCLUSIONS 

The truncation of canyons and intercanyon ridges, 

so that the lower part of a range front consists of a 

row of facets with bases well alined, may result, as on 

the west ffLce of the Wasatch, from faulting. Similar 

truncation may result from sapping by waves, but no 

available example shows the 'completed products. 

Because efficient waves inlply breadth of water surface, 

the power of the waves diminishes downward on the 

slopes of intermont valleys, becoming zero at the 

bottom. So waves can not create the range fronts 

bu t only modify them. Wind erosion is theoretically 

able to cause sirnila..r truncatiQn! Th.~ degree. of 

similarity is unknown, because exalnples either have 

not been found or have not been adequately described. 

The conditions for eolian truncation are that the 

climate shall be so arid that wind work dominates 

stream work and that the direction of the winds 

efficient for corrasion shall be parallel to the escarpment. Streanl erosion, if the streanl runs parallel t.o 

the range front and if its work is followed by deposition 

of alluvium from the range, lnay produce an escarpment with indentate base, the canyon lnouths being 

invaded by the alluvial apron. Strealn erosion by the 

streams draining the range may produce an indentate 

escarpnlent that rises from a piednl0nt of planed rock. 

The wave-made escarpment is distinguished from all 

others by the horizontality of its base line; the couleeedge escarpment is distinguished by the fact that it 

presents a single bed of lava. Escarpments made by 

erosion, whether the agent be wave, wind, or stream, 

are initially characterized by a planed-rock piedmont, 

but an eroded escarpment may acquire an alluvial piedmont after' the conditions under which it was made 

have ceased to exist. A fault-made escarpment is 

ordinarily accompanied by an alluvial apron, because 

base-level conditions rarely permit the entire body of 

waste from the lifted block to be washed from the adjacent part of the thrown block. For a truncating 

escarpment met at the base by an alluvial apron the 

presumptive origin is to be ascribed to faulting. 

Because the waves of intermont lakes do not create 

mountain fronts, because wind-made escarpments 

that truncate range sculpture are possible only under 

rare conditions of aridity and wind direction, because 

ice rivers have not occupied the intermont troughs of 

the Great Basin region, because the base line of an 

escarpment created by the streams draining a range is 

indentate, and because the base line of an escarpment 

created in a past age by a river traversing an interlllont valley and afterward partly buried by alluvium 

is also indent ate-therefore a range front that is an 

escarpment which truncates both structure and sculpture has presumably originated by faulting. The 

presumption is specially strong if the piedmont plain 

is alluvial. If the piedmont plain is of rock and the 

piedmont rocK is continuous_ with the rock of the range 

the escarpment was created or has been steepened by 

some erosive process. 

FACETS 

Davis 47 has shown deductively that truncate facets 

should be characteristic, as they are in reality, of 

youthful fronts of block mountains; and he has 

recognized also their occurrence in wave-made escarpments. As we have seen, they are found in canyon 

walls and belong theoretically to a type of wind-made 

escarpments. Plate 23 illustrates their origin by sapping where the agent of sapping is a stream and the 

. process is lateral corrasion. They are, in fact, featur~s 

of escarpments in general rather than of escarpments 

47 Davis, W, M'I Harvard CQIl. Mqs. Compo Zoolo~y Bull., vol. 42, p~. 143-160, 

l003, 
48 STUDIES OF BASIN-RANGE STRUCTURE 

of a particular type, and it is only through special 

characters that they become diagnostic of fault scarps. 

The alinement of facets has already received attention, but other characters also are illustrated by the 

Wasatch examples. 

The base line of a facet due to sapping, and the base 

line only, is determined by the sapping agent. The 

side lines are given by the hollows, usually trenches 

formed by erosion, between which it stands. If the 

walls of those trenches meet upward in a tentlike 

'crest the facet is triangular; otherwise the top line of 

the facet is determined by the form of the upland 

between the trenches. 

The slope and the texture of the facet result from 

wasting, and the wasting is conditioned by the nature 

of the material and by climate. An omnipresent 

agent in the process of wasting is gravity. If the 

material is clastic and uncemented, gravity at once 

determines a slope at the angle of rest, 30° to 35°. 

Coherent material stands in a cliff until disintegrated, 

and as disintegration proceeds it is graded to the angle 

of rest. Under an arid climate the dominant cause 

of disintegration is disruptive strain from changes of 

temperature. Under a moist temperate climate rending by frost is important and chemical weathering 

also takes place. 

The rate of disintegration is different for different 

rocks. If the terrane of the facet is heterogeneous the 

outcrops of its more stubborn rocks retain steep faces 

after the outcrops of more 'yielding rocks have been 

reduced to the angle of rest. Their positions may be 

marked, at least during the youth' of the facet, by cliff 

lines or by crags that interrupt a slope otherwise well 

graded. 

During the process of gravitational grading the 

facet may be washed by rains, but the rains accomplish 

little in the way of erosion. Their apparent impotence 

is specially noteworthy because the transporting and 

corrading power of flowing water increases rapidly 

with increase of slope, and the facet slope is steep. 

The explanation is probably to be found in absorption 

and retardation by porous talus and i~ conditions unfavorable to concentration of flow. The general uniformity of slope toward which gravitational grading 

tends does not encourage oblique flow· but guides the 

water along the dip of the surface; and such runnels 

as may be formed are likely to become clogged by 

talus. For most rocks gravitational wasting is relatively rapid and wasting by rainwash relatively slow. 

This is peculiarly true where the climat~ is arid. After 

the slope of rest has been attained, the work of weathering and rainwash may be said to begiri, and by these 

processes the slope is slowly reduced. Because the 

angle of rest is quickly acquired and slowly lost it has 

0; certain critical importance and is characteristic of 

many facets. When the veneer of talus is replaced 

by a veneer of regolith runnels are more easily formed, 

~nd competition of rlPlnels results eventually in cQncentration of drainage and the, development of dissecting ravines. Through dissection the distinctive features of the facet are finally destroyed. 

The facet produced by faulting has a somewhat 

different history. First, it has an initial slope-the 

dip of the fault. So far as we have definite knowledge 

frontal faults are normal and their dips range from 

19° to 70°. The lower initial slopes, which are less 

than the angle of rest, admit of no gravitational grading; from facets that have higher initial slopes the 

gravitational wasting is less than from those due to 

sapping. Second, a facet made by faulting, or the 

footwall from which it is shaped, does not emerge all 

at once but is formed by a series of small movements 

separated by intervals of time. It is older, therefore, 

at the top than at the base, and the slope at the top 

may have been materially reduced by weathering 

while that at the base is unchanged. If the slope 

near the base is that of the fault plane it may be joined 

to the slope at the top by a continuous curve. It is 

possible that the convex profiles of certain fault 

scarps-for example, that illustrated by Plate 1, Aare due to progressive wasting of the rising footwall. 

The same rising of a range block that develops 

frontal facets causes the deepening of dissecting canyons and thereby maintains steep canyon walls by 

sapping. Where frontal facets and canyon walls 

come together the types of scarp produced by faulting and by sapping are conveniently placed for comparison, and the scarps in juxtaposition usually contain the same formations. Plate 4, B, compares a 

sapped facet with a fault-made facet, shown in profile. The sapped facet is mainly graded to the talus 

slope, from which jut numerous crags. The faultmade facet is cragless, and its only cliff is a shore cliff 

of Lake Bonneville. The fault dip is here 29°, and 

the slope of the facet diminishes from 29° at the base 

to 23° at the top. As the entire slope of the facet is 

below the angle of rest there has been no gravitational 

wasting, and the curvature, if due to wasting, is a result 

of weathering. It is entirely possible, however, that 

the original fault surface is curved and that the wasting has been inappreciable. The profile of the next 

facet, faintly shown in the view, is nearly straight. 

Plate 21, B, compares two fault-made faoets with a 

large canyon-wall facet. The sapped facet betrays 

details of rock structure by ledges and crags, and is 

partly divided into minor facets. Its subdivision 

is probably due to bends in the course of the canyon 

stream, but other features of its sculpture are products of gravitational wasting. The faulted facet 

that adjoins it, of which the (unmeasured) slope 

differs little from the angle of rest, gives relatively 

little expression to elements of rock structure. The 

faulted facet on this side of the canyon reveals many 

details of structure. The weaker members of its 

steeply dipping sedimentary beds have segregated 

t4e draina~e and thus initiated dissection. 
WASATCH RANGE, UTAH 49 

The fault-made facets shown in Plate 20, A, which 

stand approxinlately at the angle of rest, have few 

crags at low levels and many at high levels but are 

smooth compared with adjacent canyon walls. 

In general the frontal facets of the Wasatch are 

srnoother than the parts of canyon walls immedifttely adjacent. Where they are not smoother they 

nrc oq ually smooth. The primary reason of the difference in surface character is that the frontal facets 

derived their slopes lnainly from faulting, whereas 

the slopes of the canyon walls are produced by gravitational wasting under the incitement of continual 

sapping. If the frontal fault had been vertical its 

gradual development would have produced frontal 

far-ets through the same process of gravitational 

wasting, and the facet surfaces would have agreed in 

character with those of the canyon walls, but the dip 

ot the fault corresponds so nearly with the angle of 

rest that adjustment to stability involves little or no 

wasting. The frontal facets have been initiated in a 

condition of approximate maturity, whereas the canyon walls are continually rejuvenated. ' 

The facets shown in Plate 19, B, are distinctly 

convex, but I am not confident that the curvature 

should be ascribed to weathering. As the structure 

is far from simple and as the mass includes. rocks of 

unequal strength, a more varied surface might be 

expected as a result of extensive wasting. 

Convexity is further illustrated by the configuration 

of the Lone Peak salient, as portrayed in Plates 19, A, 

and 11, A, and Figures 22' and 23. A part of the 

western face is seen in Plate 19, A, to be deeply dissected, so as to display clearly differentiq,ted basal 

facets, but farther south the pattern is less, definite, 

and not all the intergorge facets are basal. High on 

the salient are bits of sloping plain that together with 

certftin snlooth rib crests indicate the surface of a convex nlass from which the gorges have been carved. 

The simple sh.:y line in Plate 19, A, is a composite of 

such elements, and so is the smooth profile from a to j 

in Figure 23. The highest of the detached facets is 

at j, about 4,400 feet above the rock base. The harmonious alinement of high facets and high ridge crests 

supports the inference from the stranded channels of 

Corner Creek (p. 28) that the original form of the granite 

body is fairly represented by the surviving outer 

slopes, so that its restoration requires only a moderate 

allowance for waste by normal weathering. Even 

with a large allowance for weathering the indicated 

forJu is strongly convex. 

The general convexity of the facet profiles where 

sllch profiles are best preserved suggests that the fault 

surface as a whole is convex toward the west and that 

the rising movement of the Wasatch block was combined with a notable rotation toward the east. The 

tLlternative view is that the convexity of the profiles is 

~ue chiefly to the deeper weathering of the upper parts 

of th~ f~cets bec~us~ of their longer expo~u:r~. The 

evidence at the Lone Peak salient might be regarded 

as decisive but for its association with an immense 

lump of granite, which retained its integrity despite 

the shearing stress to which it was subjected in common with the inclosing rock bodies. The convexity 

at the salient is essentially that of the oburate lump 

and should not be regarded as typical of the footwall. 

The question of the rotation of blocks will eventually 

be approached from another side, and for the present 

it is well to hold ill abeyance the interpretation of 

the convexity of facets. 

The frontal facets to which attention has thus far 

been'directed are all, in a topographic sense, young. 

Because the Wasatch block is actively rising they 

have not been long exposed to wasting agencies, and 

because their rocks are strong they have wasted little. 

The Wasatch facets in weak rocks are comparatively 

worn and indefinite, and the original facets of block 

mountains now old and stagnant have been worn out 

and replaced by rib ends of a different type. The 

most decadent of the Wasatch facets are blunted and 

well-rounded rib ends, retaining of the typical characters only the simple base line, b';lt these I am not able 

FIGURE 36.-Viewof west face of Wasatch Range, Utah, 

north of City Creek spur, illustrating the evenly graded 

crests of interfiuve ridges. (From a photograph) 

to illustrate by views. Facets of intermediate character appear in Plates 22, A, 24, A, and 25, A, 

which represent localities where the faceted rock is a 

gneiss that weathers more readily than the overlying 

quartzite. OLD GRADED SLOPES 

In a division of the range between Salt Lake City 

and the canyon of Weber River, which may for brevity 

be called the Farmington division, lie remnants of 

graded plains at high levels. They head at or near 

the crest and slope westward. The best-defined group 

occurs a short distance south of Weber Canyon, and 

a second group occurs opposite and south of the village 

of. Farmington. Associated with them are somewhat 

evenly dressed rib crests with similar westward slopes, 

and these run from points near the summit of the rang~ 

to the tops of frontal facets. The graded plains near 

Weber Canyon are imperfectly shown in Plate 24, B. 

Two of the rib crests appear in Plate 25, A, but these 

examples are not so evenly dressed as some others of 

the series. Figure 36, based on a photograph made 

frOln the City Creek spur, is a general view of the rib 

crests ~nd shows the definite chBtnge of slope from 
50 STUDIES OF BASIN-RANGE STRUCTURE 

crest line to frontal facet. The general relations are 

further indicated by the diagram in Figure 37. The 

slopes of the facets are about 30°; those of the rib 

crests and high graded plains 11 ° 'to 15°. The steep 

slope just east of the crest is due to Pleistocene glaciation. In this part of the range the summit region 

and western face are composed of Archean gneisses, 

and on the eastern face the grreisses are overlain by 

eastward-dipping Eocene conglomerates. 

The broad plain indicated by these features projects 

Itself into the air in both directions. If it was piedmont to a range, the range has disappeared. Its extent 

suggests a peneplain, but its present slope is steeper 

than that of a peneplain in the making. Slopes of 

11 ° to 15° are found in canyon beds. They are also 

found on some alluvial aprons for short distances near 

their heads but are not, to my knowledge, continued 

for miles. The great alluvial apron of the Sierra 

Nevada bordering Owens Valley has a slope near the 

top of 6° and a general slope of more than 4°. Tongues 

of alluvium that invade the I vanpah Range have 

slopes as steep as 5°. 

Lawson 48 ba.s sho~ that the wasting of a range in 

an arid region may produce a planed rock slope 

E. 

wr----' ---:-::'"/~ FIGURE 37.-Diagrammatic profile of west face of Wasatch Range, 

Utah, between City Creek spur and Weber Canyon 

steeper than the slope of overlying alluvium, provided 

the waste is retained by a closed basin so that the 

base-level may rise as the work of grading progresses, 

and it is perhaps possible to produce in this way a 

graded rock slope as steep as that on the Wasatch. 

Such a result, however, could be attained only under 

exceptional conditions-for example, those afforded by 

a small closed basin that was being rapidly aggraded 

by the waste from a large upland-and it is much more 

probable that the features observed on the Wasatch 

are vestiges of an old peneplain, originally of gentle 

slope, which acquired its present attitude when it was 

uplifted. This interpretation implies that the Wasatch block, or at least a minor block of the Wasatch 

uplift, was· tilted westward as it rose. The portion to 

which the inference is directly applicable is about 

20 miles long, from Weber Canyon southward to the 

City Creek spur, and includes the western face and 

main crest line. In the latitude of Farmington there 

is a subsidiary crest line farther east, which appears 

to have been determined by the presence there of a 

distinct crustal block. 

Graded plain remnants high on the range opposite 

the City Creek spur have already been mentioned. 

Their relation to those farther north was -not deter18 Lawson, A.. C., The epigene profiles of the desert: California Univ. Dept. 

Geology Bull., vol. 9, pp. 34-38, 1915. 

mined, bu t presumably they belong to the same 

system; and if so, they promise considerable aid to 

future investigators, for they are associated with an 

aggraded plain on the spur. 

In the same Farmington division of the range rockfloored terraces lie witbin the canyons.· One of these 

terraces, dissected transversely by drainage from the 

canyon wall, is shown in Figure 17. A remnant. that 

has escaped dissection and appe~rs to retain its 

alluvial cover appears at the right in Plate 25, B. A 

closely related grade plain, dissected longitudinally, 

is shown in Figure 16. All these stand at lower levels 

than the rib-crest system and are necessarily younger. 

They record a period of orogenic rest, preceded and 

followed by periods of orogenic activity. The period 

of rest was long enough to enable the canyon streams 

to establish stable profiles and to begin the enla.rgement of their gorges by lateral corrasion. 

There may have been more than one interval of 

rest. The possibility of a second is suggested by features at and near the City Creek spur, but the data 

are too fragmentary for profitable discussion. 

The Farmington division appears to stand alone in 

its record of a high-level grade plain with marked 

westward slope. In some places the crest line of the 

range shows sucn evenness as to suggest that it has 

wasted by only a moderate amount from an earlier 

plain condition, and similar suggestion has come from 

photographs that show profiles of ribs, but if these 

obscure indications are of real significance they tell 

of peneplains with gentle slopes, and they are all 

associated with relatively high westward-facing escarpments. 

THROW OF THE FRONTAL FAULT 

The throw of a fault is the vertical element of the 

displacement between the dissevered bodies, provided 

the fault movement is translatory only. If th<' 

movement involves rotation, the throw is not the same 

for all parts of the bodies. For any pair of points, 

on opposite sides of the fault surface, that were in 

contact before the movement the right-line distance 

after the movement is' the slip, and the vertical 

component of the slip is the throw. The horizontal 

component of the slip in the direction of the strike of 

the falilt surface is the strike slip, and the horizontal 

component normal to the strike is the heave.49 

Where the corresponding points are visible and identifiable, the measurement of throw is simple. Accurate 

computation of the throw is possible also where 

corresponding structure lines are recognized on opposite sides of the fault and the direction of the slip is 

shown by striation of the fault walls. There are 

other special relations that admit of definite determination. But where, as in the Wasatch frontal fault, 

only one of the dislocated blocks is visible, the throw 

4g Report of the committee on the nomenclature of faults: Geol. Soc. AmeriQ& 

Bull., vol. 24, pp. 170-181, 1913: 
WASATCH RANGE, UTAH 51 

enn not be measured but only estinlated. In some 

places, perhaps in most, it is possible to determine that 

the throw is not less than a certain amount. 

Figure 38 gives a section of the Wasatch Range in the 

Cottonwood region and is extended to include Jordan 

Valley and the Oquirrh Range. AC represents the 

plane of the frontal fault, the attitude of which is 

known only at the rock base. Its profile is probably a 

curve and has been drawn as a straight line only 

because the nature of the curve is unknown. When 

the fault movenlent began the point A of the footwall 

and the point B of the hanging wall were in contact 

and at the surface. The distance AB is the slip of the 

fault, coincident here with the dip slip, and DB is the 

throw. Beca,use the crest of the lifted block has 

disappeared through erosion, the position of A is 

unlmown, and so is the true direction of the profile 

of the old land surface, but that profile should 

surely be drawn above the profile of Twin Peak, 

and it is highly prohable that the true position of A is 

higher than Twin Peak. B is concealed by valley 

deposits. The throw of the fault is equal to the height 

of Twin Peak above the rock base, 7,000 feet, plus an 

of the fault only a moderate allowance should be made 

for the reduction 'of Twin Peak by erosion-probably 

1,000 or 2,000 feet is sufficient. 

Jordan Valley, here 17 miles wide, is occupied to an 

unknown depth by alluvium from the two ranges and 

by lake beds. Borings near the river have explor,ed 

the deposits for 1,300 feet without reaching their base. 

On the line of the section the ~urface deposits are 

alluvial, graded downward from the range bases to the 

river. The flood plain of the river is narrow, and the 

position of the river in the valley is determined by the 

alluvial aprons. It follows the line along which the 

aprons meet. That line is nearer to the Wasatch 

Range than to the Oquirrh. For a distance of 18 

miles, from the Traverse spur to the head of the Jordan 

delta, the average width of the Wasatch apron is 6 

miles and that of the Oquirrh apron is 10.5 miles. 

This relation is abnormal, for the streams from the 

greater range are much larger and carry the greater 

load of waste. Because of the greater annual volume 

of waste from the Wasatch its apron should be not 

only wider but much wider than the Oquirrh apron, 

and the position normally appropriate for the river 

w, E. "'" ~ .~ £ c 

. g ~ { Wasatch Range t 

OqUirrh l5. Range _1:1 0 r 16 r~g50 u ~ i--~ - I~OOO 

~"···························"'··"'···················~7 . . :,. -----------------:O-----:5::----~-I:-:-O~MI:-:LE-:-S ----------_----L-&.ooo ~, ~I~I~'~'~I ____ ~I 

FIOURE 38.-Profile of Wasatch Range and Jordan Valley, Utab, illustrating data on throw of Wasatch frontal fault 

nmount representing erosion of the lifted block, plus 

an amount representing depth of valley deposits on the 

edge of the depressed block. It may be said with 

confideuce that the throw is greater than 7,000 feet. 

Tho canyons of the range front head in the neighborhood of Clayton Peale Twin Peak is the culminating 

point of a residual ridge between canyons. It is 

sharply crested and gives no suggestion of the prefault 

surface. It is, however, one of a series of ridge culminations that suggest to Hintze 50 the probable position 

of the high edge of a tilted fault block, and the curved 

facets of the Lone Peak salient indicate that that peak, 

which is in line with the rib culminations, reaches 

nearly to the plane of the old surface. (See fig. 23.) 

Clayton Peak (fig. 38) is part of a relatively broad 

summit, a table of resistant diorite that has been 

reduced to a skeleton by the development of glacial 

cirques. With reference to its immediate surroundings 

the table is a monadnock,51 and the tabular elements of 

its top may well have been graded as part of the prefault 

land surface. From these suggestions that the summit 

region retains details of form inherited from the old 

land surface I infer that in an estimate of the throw - ------.---------------------- 60 HIntze, F. F., A contribution to the geology of the Wasatch Mountains, Utah: 

New York Acad. Sci. Annals, vol. 23, pp. 88-91, 1913. 

61 Boutwell, J. M., Geology and ore deposits of the Park City district, Utab: 

V. S. Geol. Sqrvey PrOf. Paper 77, pIs. 2 and 4, B, 1912. 

course is near' the .base of the Oquirrh Range. The 

probable explanation of the river's abnormal position 

is that the bedrock support of the Wasatch apron 

is going down. The piedmont scarps sho'w its 

descent· in relation to the W asatc~ block, and the 

narrowness of the apron shows that it is descending 

as compared with the bedrock support of the Oquirrh 

apron. Whether the rock floor of Jordan Valley consists of one tectonic block or of many, it is being tilted 

eastward; and as the piedmont plain- of the Wasatch 

is built up by the addition of waste from the range, it 

is being lowered by the subsidence of its foundation, 

so that its position represents a balance between 

antagonistic influences. It is therefore probable that 

the valley fill is deeper on the east side than on the west. 

This consideration tends toward a large allowance for 

depth of valley deposits in estimating the throw of the 

fault. 

If all the waste from the range were lodged in the 

piedmont deposit a computation based on the volume of excavation involved in the sculpture of the 

range would yield an estimate-or at least a minimum estimate-of the depth of the piedmont deposit, but as an unknown fraction of the waste 

escapes down Jordan River to Great Salt Lake, 

the data are too indefinite for profitable discussion. 
52 STUDIES OF BASIN-RANGE STRUCTURE 

Such attention as I have given to the question has 

left the impression that unless Twin Peak is far 

below the original surface of the Wasatch block 

the proper allowance for thickness of the apron may 

be 2,000 or 3,000 feet. The greater the original 

height of the point A in Figure 38, or the greater 

the volume of erosion, the greater the allowance 

for thickness of apron and the lower the depression 

of B. 

In accepting 7,000 feet as an absolute Ininimum 

for estimates of the throw of the fault, I am disposed 

to regard 10,000 feet as a moderate and not improbable estimate of the throw. With the assumption that the fault surface has a uniform inclination 

of 34 0 , this yields a slip of 17,900 feet and a heave 

of 14,800 feet. 

The only other estimate of the throw with which 

I am acquainted was made by King and is 40,000 

feet. It applies to the same part of the range. His 

statement indicates a point of view so different 

from my own that I do not venture to paraphrase 

it but quote entire the paragraph in which it occurs: 

Fortunately, in the case of the Wahsatch fault we have, 

in the Cottonwood region of the Wahsatch, a magnificent 

exposure of folded stratified rocks through which the plane 

, has cut, and jrom the direct, evident reading of the section 

it is clear that the fissure which traced itself throughout the 

axis of fold of the Wahsatch in 'this particular neighborhood 

caused the westward member to sink fully 40,000 feet. A 

relic of the eastern half of the great arch of Paleozoic and 

Mesozoic rocks still remains in position, its summit members 

deeply worn away by post-Cretaceous erosion, but all the 

details of the sequence of rocks are so clear and so perfectly 

exposed that there can be no doubt of the quantitative correctness of my reading of this tremendous dislocation. In 

passing northward we have less direct evidence of the amount 

of the fault, but through the northern part of the range it can 

not have have dropped less than 2 miles. The action is simply 

a vertical one by which the western half of the Wahsatch and 

the country lying west for some miles was, relatively to the 

eastern part of the range, dropped, and the dislocation took 

place on the axial line which cut th~ region of the extreme 

topographical heights of the Cottonwood group, where the 

maximum downfall was, as announced, 40,000 feet. 52 

In the Farmington region, 30 miles farther north, 

where the range is both lower and narrower than 

in the Cottonwood region, the high-level grade 

plains and graded ribs already described (p. 49) 

aid the estimate of throw by giving fairly definite 

indication of the position of the prefault surface 

of the lifted block. The generalized profile of grade 

plains and escarpment in Figure 37 may serve for 

the consideration of the throw. Neither the height 

of the escarpment nor the local dip of the fault has 

been measured. The height above the rock base 

of the rib ends, points corresponding to Twin Peak 

in the Cottonwood profile, ~s estimated at 1,500 

feet, and the height of the range crest is about 4,000 

feet. A point that corresponds to A in Figure 38 

is about 1,500 feet above the rock base; and an 

,J l{in~, Clarc~cc, U. S. OeoI. ExpI. 40tb far. Rcpt .• vol. 1, pp. 745-746, 187$, 

estimate of the throw would add to this an allowance for the thickness of deposits resting on the 

valley block. 

The frontal apron is here narrow, being only 2 

or 3 miles wide in a tract at the south, where its 

development is not lnodified by deposits from Weber 

River. It does not meet, as in Jordan Valley, the 

frontal apron of another range, but its lower edge 

Illerges with a plain composed of lake sediments. 

As the level of Great Salt Lake rises and falls the 

boundary between areas of lacustrine and alluvial 

deposition shifts toward and from the range, and 

the two deposits are t.hus interleaved. The annual 

output of waste from the range is here much less 

than in the Cottonwood region, and so is the total 

volume, per unit of fr'Ontage, that has been excavated in the dissection of the range. These considerations tend toward a low estimate for the depth 

of burial of the valley block. On the other hand, 

the present width of the zone of alluvial deposition 

is small, and it has been still smaller whenever the 

lake has stood at higher levels. Bonneville sedirrients 

are interlarded with the alluvial deposits, and there 

is also a question of Pliocene lake beds. 

Here also there is reason to believe that the depth 

of deposition on the valley block has been affected by 

subsidence, but the most significant evidence of subsidence pertains to a tract much broader than Jordan 

Valley. 53 Great Salt Lake does not lie in a bowl but is 

spread over a plain. Its mean depth is less than 15 feet. 

The plain extends from the base of the Wasatch 

Range westward for 120 miles to the base of the 

Gosiute Range. West of the lake it is the Salt Lake 

Desert and is so nearly level that the flow of water on 

its surface does not wash the salt from its soil. The 

plain has been produced by deposition, not by erosion, as is shown by its relation to the Great Basin 

corrugation. It lies within the province of corrugation, but its ridges are low and discontinuous. They 

are crests and peaks of mountain ranges whose bases 

are deeply buried by sediments. Toward the north 

and toward the south the corrugated system rises, 

until at the limits of the plain the ranges have normal' 

heights and the valley troughs are of normal type. 

The plain occupies an epeirogenic hollow in a region 

of orogenic corrugati0n. 

The principal rivers that bring detritus for the building of the plain are the Jordan, Weber, and Bear, all 

rising in the uplands east of the Wasatch Range. 

Their contribution of debris must be several times 

greater than that brought to the plain by all other 

streams. All the coarser part of their debris is deposited 

near their mouths, and at all times they must have 

deposited more debris, coarse and fine, on the eastern 

part of the plain than on the western part. Neverthe61 r:r:he discussion contained in this paragraph is in part the restatement of an 

earlier d,iscussiol\. S~e (HIlbert, G. 1\:., U. S, Geol. S\lrvey l\1op. 1, pp. 384-386, 

pI. 48, l89Q. 
WASATCH RANGE, UTAH 53 

less the position of the lake shows that the plain is 

lower at the east than at the west. The western shore 

of the lake is 75 lniles from the western edge of the plain. 

The eastern shore in two of its bays lies close to the 

base of the Wasatch Range. At the south edge of the 

Weber River delta the strip of land between lake and 

mountain is 2 miles wide, and at the north edge it is 

only 1 mile wide. Had the rock foundation of the 

region been stahle during the building of the plain the 

surface would now slope westward and Great Salt 

Lake would lie along the base of the Gosiute Range. 

The actual position of the lake testifies to subsidence 

of the eastern part of the plain. Because the total 

volume of debris accumulated in building the plain is 

large, and because the contribution from the east has 

been relatively large during at least the later part of 

the period of plain building, and because during the 

same later part of the period the greater part of the 

debris from the east has been deposited near the eastern edge of the plain, it is inferred that the depth of 

the deposit close to the Wasatch fault is large. Because 

the epeirogenic sag, as indicated by the relation of the 

aggraded plain to orogenic corrugation, is greater 

where the lake lies than toward the north or south, 

it is inferred that the depth of deposit is specially 

great under that part of the Wasatch foreland that is 

opposite the lake. Therefore, for the Farmington 

division, the portion of the range between Weber 

Canyon and Salt Lake City, the estimate of the throw 

of the fault should include a very large allowance for 

depth of deposit on the concealed block, a much larger 

allowance than should be made for the Cottonwood 

division. A quantitative statement of the difference is 

not warranted by the facts at command, but it is 

evident that a mistake would be made if great disparity of fault magnitude between the two localities 

were inferred becam;e at one locality the fault scarp 

is 7,000 feet high and at the other only 1,500 feet. 

The preceding discussion leads to two suggestions 

for the explanation of apparent anomalies. As 

already noted (p. 50), the attitude of high-level grade 

plains of the Farmington region indicates that the 

great fault block of the range is there tilted westward 

through an angle of more than 10°. Evidence of 

similar tilting has not been discovered in other parts 

of the range, but for the Cottonwood division of the 

Wasatch Range Hintze has plausibly suggested tilting 

in the opposite direction, and many range blocks in the 

Great Basin have been thought to be tilted away from 

their bolder escarpments. It is now suggested that 

the apparently exceptional tilting of the Farmington 

division of the Wasatch Range is connected with its 

relation to the epeirogenic sag that is marked by the 

position of Great Salt Lake, that the steepest slope 

toward that depression is not from the north or south 

but from the east, and that the attitude of the range 

block is due less to its own rotation than to epeirogenic warping. 

In no other part of the range have well-preserved 

high-level grade plains been found. The exceptionally good indication in this tract of the attitude of the 

fault block has occasioned surprise, because the 

Archean rocks on which the grade plains are preserved 

are neither homogeneous nor highly durable. For the 

preservation of fault facets along the escarpment they 

are inferior to the quartzites and granites. At one 

time I suspected that this part of the range was relatively young, but it now seems to me more probable 

that its dissection has been retarded by its peculiar 

attitude and its moderate altitude. Because the 

fault scarp is here relatively low the canyons that 

dissect the range block are relatively shallow and narrow and their development has not wholly obliterated 

the original profiles of the intercanyon ridges. Also 

because the range crest is here less lofty than in some 

other divisions it has been less consumed by Pleistocene glaciers. In the Cottonwood region, where neve 

buried the whole crest tract and ice tongues reached 

the western base of the range, the upper reaches of the 

canyons were enlarged and remodeled by glacial head 

erosion. In the Farmington region, where the summit 

tract is' 3,000 feet lower, moSi of the accumulation of 

neve was on the east side-the lee side-of the crest, 

and, although the east side shows to distant view a complete cornice of high cirques, the west side betrays 

little evidence of glaciation. 

CROSS DRAINAGE AND BACK VALLEYS 

CROSS DRAINAGE 

A tract of country east of the range is drained by 

streams that cross the range to the lowlands at the west, 

their waters ultimately reaching Great Salt Lake. It 

is characteristic of this system of cross drainage that it 

follows many lines instead of one or two. Its streams 

are Box Elder Creek, Ogden River, Weber River, 

Provo River, Hobble Creek, Spanish Fork, and Santaquin Creek, and the list should perhaps include also 

Payson Creek. Bear River, which runs westward 

past the north end of the range, cuts through a low, 

uplifted ridge that may properly be called a continuation of the Wasatch, and a similar statement 

would apply to Salt Creek at the south. Were the 

canyons of cross drainage to be filled up, the basins 

of Box Elder Creek, Ogden River, and Weber River 

would drain northward to Bear River in Cache Valley, 

and those of Provo River, Hobble Creek, and Spanish 

Fork would drain southward through San Pete Valley 

to SAvier River and Sevier Lake. 

The main crest line of the range is in part the summit of a continuous ridge and in part a line through 

high points separated by canyons, and there are several subordinate crest lines. At points where the eastern face is most definitely shown its base is bordered 

by small valleys sunk in the general upland. These 

valleys, which are described in the next section, I 
54 STUDIES OF BASIN-RANGE STRUCTURE 

find it convenient to speak of as back valleys. As 

defined by them and by the courses of certain creeks, 

the range has an average width of 8 or 9 miles, but 

the width runs from about 2 miles opposite Mantua 

Valley to 15 or 20 miles in the region of the Lone Peak 

and Clayton Peak granite bodies. 

The uplifting of a mountain ridge tends to create a 

water parting. If the uplift of the Wasatch ridge 

had been the only factor in the development of Wasatch drainage no streams would cross 'the axis of 

uplift. The cross drainage has been caused by some 

other factor, and the determination of its mode of 

origin should contribute to our knowledge of the history of the range. The first writer to consider this r 

subject was Howell, whose observations included the I 

southern part of the range as well as adjacent regions 

on the east, west, and ·south. In common with the 

geologists of the Fortieth Parallel Survey he recognized 

that the Great Basin had been a dry-land area at a 

time when Tertiary lakes covered much country on 

the east and regarded it as a source of material for 

Cottonwood district the divide is nQw near the eastern 

edge of the range and its earlier position is indicated 

by a line of high points on intercanyon ridges farther 

west. To illustrate these relations Hintze constructed 

a bird's-eye view, which I reproduce in Figure.39. We 

now know that the dip of the frontal fault is fi\uch less 

than his diagram indicates, and it may be noted also 

that the vertical dimensions of the diagram are unduly 

large in relation to the horizontal, but the truthfulness 

of the construction as a general expression of the local 

structure and topography is not vitiated by these minor 

defects. I see no reason to question his conclusion 

that the water parting has migrated eastward and 

that the migration has been determined by the superior 

vigor of westward-flowing streams. In a tentative 

way Hintze extends this explanation to other parts 

of the range, suggesting that Weber and Provo Rivers 

began their careers as streams of the fault face and, 

having eaten headward across the range, succeeded in 

capturing other drainage and thus acquired their 

present broad development. 

A contribution to the same general theory 

of the development of the river basins by 

head erosion has been made by Anderson,56 

who points out that one of the principal 

branches of Weber River. has recently been 

diverted to the Provo drainage basin, ascribes 

the diversion to headwater erosion by the 

Provo, and states with confidence that the 

Weber drainage was fully developed before 

FIGURE 39.-Stereogram of a portion of the central Wasatch Mountains, Utah. The main Provo River pierced the range. Two of the 

gorges are Big Cottonwood and Little Cottonwood Canyons. (After Hintze) back valleys he ascribes to lateral erosion by 

Tertiary lake beds. The general direction of the local 

drainage was at that time eastward, and it was afterward reversed. Howell's idea was that the notches 

in the Wasatch ridge were made before the reversal 

of the drainage and that these notches controlled the 

courses of streams when the elevation of the area occupied by the Tertiary lakes turned the drainage 

toward the Great Basin.54 It is implied that a ridge 

existed on the present site of the Wasatch before the 

great change in relative altitudes of the districts 

east and west of it. The positions of crossing streams 

having been thus determined, the present canyons were 

developed during the uplift of the range. 

Hintze,55 whose treatment of the subject is comparatively full, made his principal studies in the Cottonwood district, where the range is exceptionally high 

and broad. It·is his idea that as the range block rose 

its western face was relatively steep and high, that 

the relative power thus given to westward-flowing 

mountain streams enabled them to lengthen their 

courses by headwater erosion, and that the water parting was thereby made to migrate eastward. In the 

Ie Howell, E.E., Report on the geology of portions of Utah, Nevada, Arizona, and 

New Mexico examined in the years 1872 and 1873: U. S. Geog. and Geol. Surveys W. 

100th Mer., vol. 3, pp. 227-301, 1875. (See especially pp. 251-252.) 

55 Hintze, F. F., A contribution to the geology of the Wasatch Mountains, Utah: 

New York Acad. Sci. Annals, vol. 23, pp. 88-91,1913. 

the rivers-Rhodes Valley, which was carved Gut by 

Weber River while the deepening of its channel was 

delayed by a strong sill a few miles below, and Heber 

Valley, which was similarly opened by Provo River 

in consequence of resistance in its near-by canyon 

through the range. I shall have occasion to consider 

these conclusions in discussing the back valleys. 

In describing the geology of the belt of country 

traversed by the Union Pacific Railroad Lee 57 mentions the cross drainage of Weber and Ogden Rivers 

and briefly considers its cause. He states that the 

river courses were established in Tertiary time on an 

aggraded plain and held these courses during the 

growth of the range. As the rivers sank their channels into terranes of complicated structure beneath 

the original plain they produced canyons in the 

stronger rocks and valleys in the weaker. His view is 

perhaps consistent with Howell's but not with the 

views of Hintze and Anderson. 

The primary question as to which opinions differ is 

that. of the antiquity of the range-crossing watercourses. Were they established before the growth 

of the range, or were they developed by headwater 

6& Anderson, G. E., Stream piracy of the Provo and Weber Rivers, Utah: Am .. 

Jour. Sci., 4th ser., vol. 40, pp. 314-316, 1915. 

67 Lee, W. T., Guidebook of the western United States, Part B, The Overland 

Route: U. S. Geol. Survey Bull. 612, footnotes to pp. 97 and 102, 1915. 
WASATCH RANGE, UTAIl' 55 

erosion from short courses on the western flank? 

With reference to the movements that created the 

range, are they antecedent or subsequent? 

Howell notes that two streams cross the range on 

lines of structural weakness. He says: "Provo River 

marks the axis of a synclinal, and at Spanish Fork 

there is probably a fault," but he adds that "this 

only illustrates the tendency of eroding water to 

attack the weakest points, and while it serves to explain the selection of these particular lines for crossing, it leaves untouched the question why the streams 

crossed the range at all instead of escaping eastward 

over the lower barriers which in that direction limit 

their basins." It is true also that Box Elder Creek 

crosses at a point where the structure of the range 

changes, where the line of the front makes a sudden 

tiurn, and where the range is exceptionally narrow 

fLnd exceptionally low. 

On the other hand, I know' no reason to infer gUIdance by structural weakness at the canyons of Weber 

River and :Hobble Creek, and there is no cross drainage opposite Salt Lake City, where a great syncline 

not only brings weak rocks to the surface but arranges 

their outcrops in lines athwart the range. On the 

axis of the syncline the divide is forced far to the east 

of the main crest line but not farther than in the 

neighboring Cottonwood district (fig. 39), where the 

rocks are exceptionally strong. 

Ogden Canyon is near a cross fault of pre-Tertiary 

date, but it is not probable that this occasioned weakness at the time when the range was lifted. Little 

light is thrown by these facts of position on the origin 

of the drainage. Because headwater extension is 

promoted by weak rocks the fact that some of the 

courses follow faults is favorable to the theory of 

subsequent drainage, but its influence seems to be 

offset by the failure of cross drainage to occupy the 

outcrop of weakest strata near Salt Lake City. Because a rising ridge tends to pond the cross drainage 

and thereby divert it to low passes, the positions of 

two courses on sags of the range favor the theory of 

antecedent drainage. Such other evidence as is 

available is connected with the phenomena of the 

back valleys, and the consideration of cross drainage 

will be resumed after the back valleys have been 

described. 

BACK VALLEYS 

HEBER VALLEY 

'"1"'he southernmost of the back valleys, Heber, has 

no pronounced trend; its main part is 8 or 10 miles 

across in any direction. Provo River enters it from 

the north and leaves it toward the southwest, passing 

quickly into Provo Canyon, by which the river crosses 

the Wasatch Range. Several creeks that rise in the 

surrounding hins join the river within the valley. The 

valley surface is a smooth alluvial plain, evidently 

built by the streams that traverse it. The stream 

channels are little below the plain, and the de~pest 

incision is that made by the river near its point of 

exit. The boundaries of the plain are irregular in 

outline and in places are indefinite. There is no alinement of hill fronts to suggest faulting. The hill slopes 

meet the plain in such a way as to suggest that their 

sculpture is related to a base-level lower than the 

present and that the alluvial fill is deep in the lower 

part of the valley. As illustrated by Plate 26, A, the 

aspect is that of a "drowned" valley, except that the 

invading flood is alluvial instead of aqueous. The 

surrounding uplands are hilly rather than mountainous 

except on the side toward the Wasatch Range, and 

there the valley and mountain are separated by irregular foothills. 

Confluent with Heber Valley is a smaller pocket 

among the bills called Round Valley. A narrow arm 

of Heher Valley follows down Provo River and is 

joined by a narrow arm of Round Valley just above 

the head of Provo Canyon. At the point of junction 

is.a graded plain of local origin (pI. 27, B), coordinate 

with the plains of the two valleys but standing about 

75 feet above the flood plain of the river. The condition that determined aggradation in the valley 

system has ceased to exist, and the erosion of the deposits is in progress. The terrace that isso 'conspicuous at the junction of the valleys is not traceable downstream. The upper part of Provo Canyon, although 

carved in the weak rocks of the eastern foothills, js a 

narrow V gorge, as shown by Plate 27, A. 

The probable history of Heber and Round Valleys 

is as follows: A period of rest in the growth of the 

range permitted Provo Canyon to be cut so deeply 

and maintained with low grade for so long a time that 

Heber and Round Valleys were excavated, their siteR 

having been occupied by weak rocks. Renewed or 

accelerated uplift of the range then raised the local base.;. 

level and caused the valleys to be aggraded. Finally, 

slackening uplift has permitted the river, by deepening 

its canyon, to lower the sill that is base-level for the 

valleys, and the filling of alluvium has now begun to 

be trenched by the river. 

Consideration was given to two alternative explanations of the deposition and trenching of alluvium in the 

valley. The lower part of Provo' Canyon contains 

elevated grade plains that are supposed to be related 

to temporary base-levels created by Lake Bonneville. 

None were seen in the upper part of the canyon. As 

the river bed at the head of the canyon is about 300 

feet higher than the Bonneville shore line, it is thought 

that the Bonneville high water did not appreciably 

affect gradation in Heber Valley. 

When Provo River captured the south branch of 

Weber River (see p. 56), a body of alluvium was swept 

down the Provo from Rhodes Valley. This alluvium 

would tend toward temporary aggradation in Heber 

Valley but is thought not to have caused the principal 

changes there-first, because it is inferior in volume 
56 STUDIES OF BASIN -RANGE STRUCTURE 

to the deposit in Heber Valley and, second, because the 

time of its movement, as judged from the phenomena 

in Rhodes Valley, is later than the time of maximum 

deposition in Heber Valley. Provo River was probably able, after enlargement by the discharge of the 

captured branch; to transport its enlarged load without 

noteworthy temporary lodgment in Heber Valley. It 

is possible, however, that the debris from Rhodes 

Valley is responsible for the fact that the Provo 

channel, although well incised just abov; the head 

of Provo Canyon, shows little incision in the \lpper 

part of Heber Valley. 

RHODES VALLEY 

The Uinta Range, which trends westward, approaches the Wasatch Range at the point where the 

Wasatch is widest. Between them lies a belt of 

trachyte that obscures the structural relations of the 

ranges. Between the trachyte and the core rocks of 

the Uinta lies Rhodes Valley-formerly known as 

Kamas Prairie-which has a length north and south 

of 11 miles and a width of 2 to 4 miles. The general 

structure of the Uinta Range is anticlinal, with westerly strike, and the rocks near Rhodes Valley' are 

Paleozoic. The drainage from the western 20 miles 

of the crest -region is caught by Provo River at the 

south and Weber River at the north, and these streams 

flow westward, in the general direction of the strike. 

The Provo crosses the south end of Rhodes Valley on 

its way to Heber Valley, Provo Canyon, and Utah 

Lake. The Weber crosses the north end of Rhodes 

Valley on its way to Morgan Valley, Weber Canyon, 

and Great Salt Lake. Thus two streams that rise in 

the Uinta Range cross the same little hill-girt open 

valley and eventually cut through the Wasatch Range 

at points 56 miles apart. 

The floor of the valley is alluvial and smooth, with 

gentle slopes toward the north and west. Except for 

a narrow strip along Provo River it is drained by 

Weber River, and, as pointed out by Anderson,68 the 

floor was evidently shaped in chief part by the south 

branch of the Weber before that branch was captured 

by the Provo. Since the capture the Provo has 

intrenched itself to a depth of about 150 feet and in 

so doing has exposed a partial section of the floor 

material, showing that it is river gravel and sand with 

stratification parallel to the surface. The present 

plain is not a veneered rock floor but has been built 

up by alluvial deposition in a preexistent valley. The 

principal depos~ting s'tream was the south fork of the 

Weber, and its work of deposition was probably continued up to the time of its diversion to the Provo 

Basin, after which it began to erode what it had 

before deposited. The moderate width of the excavated trench indicates that the date of the diversion 

was not remote. 

68 Anderson, G. E., Stream piracy of the Provo and Weber Rivers, Utah: Am. 

Jour. ScL, 4th ser., vol. 40, pp. 314-316, 1915. 

My only visit to the locality was made in 1877, and 

I gave only casual attention to the drainage system. 

My notes ascribe the diversion to the upbuilding of 

the alluvial plain until it reached the level of a col 

between the Weber and Provo drainag~ basins. Anderson has since ascribed_ it, as already mentioned, to 

headwater erosion by a branch of the early Provo. 

. At the time of my visit only !econnaissance maps 

were available, but the region has now been more 

accurately delineated, so that many details of relief 

are expressed by contours. A study of the contours 

has led to the suggestion that n'either of the two proposed explanations of the diversion is adequate without modification and has indicated the desirability of 

additional field study. 

There is need also of further investigation to determine the origin of the valley. Anderson notes the 

existence of a strong rock sill over which the Weber 

runs after leaving the valley and thinks the resistance 

at that point so delayed vertical corrasion that the 

river was enabled to carve out the valley by lateral 

corrasion; but this hypothesis does not account for the 

excavation of the valley below the surface of its present 

'alluvial plain. As an alternative hypothesis I suggest 

a fault, with westward throw, along the eastern edge 

of the valley. The Fortieth Parallel Survey geologic 

map indicates truncation of structural features by the 

escarpment on that side of the valley, and the contours 

of the Coalville topographic map suggest truncation of 

sculpture. 

MORGAN VALLEY 

From Rhodes Valley to Morgan Valley Weber River 

runs for 35 miles through an upland of varied rock, 

and the width of the passage it has opened is everywhere adjusted to the erosibility of the rocks. Close 

to Morgan Valley there is a small opening, one of the 

many to receive the title of Round Valley, which well 

illustrates the adjustment. Above it the river is held 

in a close canyon by walls of strong Paleozoic limestone. Below it lies a narrow passage across a spur of 

similar limestone. Between the two is a circular 

opening in weaker rocks, which are in part arenaceous 

shales of Carboniferous age and in part Eocene sands. 

Morgan Valley, which is much broader than the 

other openings, is plausibly interpreted by Lee 59 

as equally a product of erosion, its width being correlated with the weakness of a local Pliocene formation. 

It differs from the others, however, in that its recent 

development by erosion has been but the clearing out 

of a preexistent structural valley, and there is also the 

possibility of rep.ewed movement on an old line of dislocation. The Paleozoic rocks about Round Valley 

are part of a large mass tHat projects through and 

rises above the prevalent Eocene terrane, culminating 

in Morgan Peak, 4,000 feet above Morgan Valley. 

6D Lee, W. T., Guidebook of the western United States, Part B, The Overland 

Route: U. S. Geol. Survey Bull. 612, p. 89, 1915. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PI.ATE 25 

The crests of jnlcrcanyon ridges have inherited evenness of profJlc from Ull old peneplain, of which fragments arc shown ill Plate 24. B. The truncate ends of lhe ridges arc face ts of the frontal escarpment. Across them run horizontal terrace' shaped by Lake Bonneville 

B . MOUTH OF WEBER CANYON 

The walls consist of Archean gneiss. The walls of the smaller canyon a t the right arc relatively mature in sculpture, a nd so is the alluv ium- capped b ench between the canyons. The end of tha t bench is notched (at the extreme right) hy the Bonnev ille sbore line 

VIEWS IN WASATCH RANGE. UTAH 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 26 

A. MARGIN OF HEBEl'l VALLEY, NEAR CHARLESTON 

The valley, once deeper, h as received a fl ood of alluvium. The level surface of the alluvium is here contrasted with slopes of the older 

lopography 

B. SOUTH E D OF MORGAN VALLEY 

The view is southward from a point near Morgan. The smooth plain has been produced by alluvial deposition in a valley previously deep 

BACK VALLEYS OF THE WASATCH RANGE, UTAH 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 27 

A. THE CANYON NEAR ITS HEAD 

Provo H..ivcr Crosses Lhe Wasatch Range from east. t.o west by this cauyon. The view is downstream . In t.his part the canyon is narrOw and without. a flood plain 

B. AN OPENI TG ABOVE THE CANYON 

The opening is a back valley, commuuicating with Heber Valley and Circle Valley, and was aggraded at the same time with those valleys. (See pI. 26, A.) The aggradation is ascribed to an uplift of the range. The subsequent deepening of the canyon has enabled the river to scour a channel through this part of the deposit 

PROVO CANYON, UTAH 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 28 

Tbe pass is seen at the left. 

EAST FACE OF WASATCH RANGE NEAR EDEN PASS, UTAH 

The lowland is part of Ogden Valley. now drained by Ogden River, which crosses the range farther south. The pass is interpreled as the channel of a stream that once drained part of the Ogden Valley area but was finally decapitated hy a branch of Ogden Hiver 
WASATCH RANGE, UTAH 57 

This body of olde.r rock appears to belong to an orogenic 

block distinct from the Wasatch and coordinate with 

if not continuous with the block that constitutes the 

Bear River Range east of Cache Valley. The sanle 

tentative correlation makes Morgan Valley a structural trough, like Cache Valley, and separates the Morgan block frOl11 the Morgan Peak block by a fault. 

The Pliocene formation is not known to extend 

beyond Morgan Valley but appears to have been 

deposited in a lake, or perhaps a bay, bounded by the 

valley walls. 60 Since deposition it has been broken 

into blocks, the blocks have been tilted, and the 

resulting disturbed surface has been graded, but this 

history, so far as known, has been enacted within the 

MorgtLll trough and has not affected its topographic or 

tectonic unity. . 

The present Morgan Valley has a flat alluvial 

floor abo\lt 13 nliles long and fr01n 2 to 3 nliles wide. 

Its trend is west of north and is not quite parallel 

to that of the adjacent part of the Wasatch Range, 

being l110re westerly. Weber. River does not run 

through the entire l~ngth of the floor but enters it a 

few miles north of the south end. 

For severall11iles alo~g the western side of the plain 

the steep fronts of the bounding hills, which are composed of Tertiary rocks, form a nearly straight escarplllent and have been modified by recent slumping. 

The scarps made by the slunlping fall nearly in line, 

and it is possible that they constitute a fault scarp, 

indicating a very recent movement on the plane of 

the old fault at the edge of the structural trough. 

The walls of the valley bear terraces at several 

levels, and the study of these can not fail to throw 

light on' the valley's later history, but such scattered 

observations as I have been able to make have opened 

l110re questions than they have ·answered. At about 

1,000 feet above the Bonneville plain is a grade plain, 

now dissected, that truncates the inclined Pliocene 

strata. It was most clearly seen at the north end of 

the valley and probably corresponds to the upper of 

two undissected terraces east of the north end. Less 

definite high terraces appear farther south on the 

east . side and in Round Valley. The fact that corresponding terraces were not discove:r:ed on the west 

side of the valley suggests the possibility of an extensive late Pliocene deformation or dislocation that 

involved the adjacent part of the Wasatch Range. 

The principal part of the alluvial floor of the valley 

was laid during the Provo stage of Lake Bonneville. 

At that time a large delta was built by Weber River 

against the west face of the Wasatch Range, and the 

floor of the valley was graded in relation to the delta 

as a base-level. The material was brought not only 

eo By the geologists of the Fortieth Parallel Survey the Pliocene beds of Morgan and 

Cacbe Valleys were called Humboldt, but this name implies a correlation and classi· 

Ooatlon that have since been questioned. Until the Morgan Valley Pliocene beds 

shall be restudied it seems bcst to leave them without a formation nume. 

62436-28-5 

by the river but by III any of its local tributaries, and 

a large contribution was furnished by East Canyon 

Creek, which traverses' the south end of the valley 

beyond' the point at which the river enters. (See 

pI. 26, B.) At the earlier and higher stage of the 

Pleistocene lake the valley contained a bay, the shore 

lines of which are readily recognized at a number of 

points. Since the fall of the lake waters from the 

Provo level the Weber and some of its tributaries 

have intrenched themselves in the Provo plain, but 

the amount of erosion has been small. The depth of 

the incised channels is greatest at the outlet of the 

valley and diminishes upstrealll until it ceases to be 

appreciable at Morgan, where the Weber enters the 

valley. East Canyon Cre'ek still flows at the level of 

the plain it built in the Provo epoch. 

PARLEYS PARK 

Rhodes Valley, which lies against the end of the 

Uinta Range, is' not so closely related to the Wasatch 

Range as Morgan and Heber Valleys. Between 

Rhodes Valley and the Wasatch crest is a snlaller 

opening known as Parleys Parle As this park lies 

at the base of the range and falls in line with Heber, 

Morgan, and Ogden Valleys, it is topographically one 

of the back valleys of the Wasatch, but I am not able 

to describe it from direct observation. It is the highest of the series, lying 2,200 feet above Heber Valley, 

1,300 feet above Rhodes Valley, and 2,800 feet above 

Morgan Valley, to which its drainage is carried by 

East Canyon Creek. 

OGDEN VALLEY AND EDEN PASS 

The valley in which the branches of Ogden River 

unite before crossing the range has the general form of 

an acute triangle with one side at the base of the 

range and the greater width at the south. In several 

features it resembles Morgan Valley. It contained a 

bay of Lake Bonneville and retains some of the higher 

shore traces. Its lower part was aggraded during the 

Provo epoch of the lake, and the grade plain was 

continuous with that of a delta built against the west 

face of the range. Since the Provo epoch the streams 

have opened narrow, terraced valleys in the alluviunl 

of the' plain. Hague 61 has recorded Pliocene lake 

beds in the valley, and though I have not visited their 

outcrops I have noted from a distance that they 

exhibit such dips as to indicate dislocation since their 

formation and that the dislocated blocks have been 

truncated by grade plains of more recent construction. 

On the eastern margin of the valley there is a fault 

with throw to the southwest, and the northwesterly 

strike of this fault is not parallel to the local trend of 

the Wasatch Range, but if projected the fault would 

meet the range at the north. . 

61 Hague, Arnold, and Emmons, S. F., Descriptive geology: U. S. Geo!. Expl. 

40th Par. Rept., vo!. 2, p. 418, 1877. 
58 STUDIES OF BASIN-RANGE STRUCTURE 

The fault is indicated by a straight boundary 

iJetween rock hills on the east (mapped by Blackwelder as "Algonkian?") mid the alluvium of the 

valley. In part the hill face is steep and the alluvium 

at its base has a gentle slope, but farther north the 

hill slope is low, differing little from that of the alluvium, which is banked high against it. In the lastmentioned tract the alluvium has slumped toward the 

valley in great waves, leaving a scarp that is well 

defined for about 2 miles. These features are best 

shown a short distance south of Wolf Creek. 

The portion of the Wasatch Range oppo'site Ogden 

Valley has two members distinguished by their physiographic habit. The western member has rugged summits, with many crags of resistant rock. The eastern 

lnember has rounded summits, ,and its entire sculpture is of a mature or subdued type. At the south, 

near Ogden Canyon, and again at the extreme north 

the western member is much the higher and the eastern ranks as a belt of large foothills, the relations 

being as indicated in Figure 40 and the diagram on 

Plate 28, A. A little north of Ogden Canyon the 

eastern member climbs high on the western, and it 

is there evident that the plane which separates the 

two rock bodies inclines toward the east. Farther 

FIGURE 40.-Diagram of two members of Wasatch Range, Utab, opposite Ogden Valley. Compare with diagram on Plate 28, A 

north, beyond the village of Liberty, a break occurs 

in the eastern member and the face of the western 

has a slope of 30° or 35°. In a general way the eastern member corresponds to the Algonkian body 

described by Blackwelder 62 and the western to the 

body of Paleozoic rocks over which the Algonkian has 

been thrust by a reverse fault, the Willard overthrust, 

but north of Liberty the correlation breaks down. 

From, that p.oint the' outcrop of the overthrust surface turns westward and crosses the range obliquely, 

but the line between the two members distinguished by 

physiographic characters continues northward, parallel to> the main axis of the range. The working 

hypothesis. yielded by the physiographic relations is 

that a normal fault separates the eastern body from 

the western, the plane of the fault dipping eastward 

at about 35° and probably coinciding in part with 

the plane of the much older overthrust, which lS 

undulatory. . 

Five miles north of Ogden Canyon the range IS 

deeply grooved by a cross valley, Eden Pass. The 

summit of the pass is about 800 feet above the eastern base, 1,500 feet above the western, and 2,000 feet 

below neighboring parts of the range crest.63 The 

63 Blackwelder, Eliot, New light on the geology of the Wasatch Mountains, Utah: 

Geol. Soc. America Bull., vol. 21, pp. 520-526, 533-536, 1910. 

63Accuracy is not claimed for the figures here given and the dimensions implied 

by the diagrams. The available maps are crude, and I undertook no measuremen ts. 

pioneer trail and the first wagon road from the Salt 

Lake plain to Ogden Valley followed this route. The 

summit lies close to the eastern face of the range, as 

illustrated by Figures 41 and 42, and the pass, as 

seen from the east (pI. 28, A), has the appearance of 

a hanging valley. The material at the summit (see 

pI. 28, B) is hill wash with smooth slopes, and this 

occupies a space of about 1,500 feet between rock 

, walls at the north and south. The eastward descent 

from the summit is steeper than the westward. The 

branches of the main draining streams are adjusted 

in direction to the position of the divide, as indicated 

diagrammatically in Figure 42. All these characters 

w.~. 

FIGURE 41.-Diagrammatic profiles of Wasatch Range at Eden Pass, 

Utah. The middle line is the profile in the pass. s, s, Shoulders 011 

side wall of pass 

indicate that the pass is ail "air gap" which lnarks 

the course of a streanl that once crossed the range 

from east to west. The alternative hypothesisthat the pass has been created through headwater 

erosion by the stream flowing westward from the 

summit-is negatived by the relative steepness of the 

westward descent from the pass and by the trends of 

the subordinate drainage. It is further negatived by 

the fact that the rocks traversed by the westward-flowing stream are stronger than those traversed by the 

eastward-flowing stream. Acceptance of the air-gap 

hypothesis makes it possible to utilize also certain 

details of sculpture that might otherwise be regarded 

w. E. 

FIGURE 42.-Diagram to illustrate directions of drainage 

lines at Eden Pass, Utah 

as accidental. On the south side of the cross trench 

and west of the pass there are several shoulders on 

side spurs (see fig. 41) that suggest an ancient terrace 

of gentle slope, descending westward from the summit. 

They are not sufficiently definite to be independently 

demonstrative, but in connection with an accepted 

air-gap hypothesis they indicate - the direction of 

slope of the ancient cross channel. 

To put the accepted hypothesis in other words: 

At a stage in the history of the range when the difference in height between the range block and the valley 

block was 1,000 to 1,500 feet less than now a part of 

the tract that now drains westward through Ogden 
WASATCH RANGE, UTAH 59 

Canyon was drained in the sanle direction through 

Eden Pass, and afterward the EdEm Pass drainage was 

diverted to Ogden River. The diversion presumably 

occurred by capture, although the capture may have 

been induced by warping or faulting. Whatever the 

circmnstances of capture, the channel of Ogden River 

must have been lower than a corresponding part of 

the channel of the Eden Pass stream; and thus the 

interpretation of the air gap leads to the conclusion 

that Ogden Canyon was in existence long before the 

completion of the uplift of the range. 

MANTUA VALLEY AND DRY LAKE TROUGH 

The small settleInent long known as Copenhagen 

has been rechristened Mantua, and its post office, once 

styled Geneva, is now known as Mantua. This 

name is therefore selected to designate the little back 

vnlley that contains it. The valley floor, about 2 miles 

wide and nearly twice as long, is surrounded by hills 

that rise rather abruptly. On the west is the Wasatch 

H.ange, a definite high wall that extends visibly beyond 

the valley in both directions. It is flanked by a narrow belt of foothills, which in part have the character 

of a sloping terrace. On the east stands a bold, un disoected, and rather even escarpment, 1,500 ·feet high, 

the steep face of a ridge that falls off more gradually 

on the opposite side. This escarpment is parallel to 

that of the range, and the two serve to give to the valley an appearance of definite trend a little west of 

north. In the eastern ridge there are rock croppings 

that show strike and dip, and it is evident that the 

rock structure is not parallel to the trend of the ridge. 

The escarpment truncates the structure and is presumttbly the fault face of an orogenic block that is tilted 

eastward. The valley thus reseInbles 'Morgan and 

Ogden Valleys in that its eastern edge coincides with a 

normal fault so recent that its topographic expression 

has not been effaced. The fault and fault block are 

evidently features of the post-Eocene diastrophIsm, 

tmd the discordant dips of strata within the block are 

ILssU'med to be features of pre-Eocene diastrophism. 

The floor of the valley is alluvial and smooth. 

Streanls that reach it from the south and north run 

near the western edge and unite midway to constitute 

Box Elder Creek, which immediately enters the canyon 

by which it crosses the range. The floor is graded in 

slopes that converge toward the canyon, and a related 

gradation is indicated by terraces in the canyon. My 

observations did not suffice to establish a general cor-

. relation, but presumably the slopes are adjusted to 

those of a delta that was built at the mouth of Box 

Elder Canyon during the Provo stage of Lake Bonneville. The stronger streams of the valley have sunk 

their channels below the general floor, exposing its 

constitution of gravel and sand, and the trench of the 

main or south branch of Box Elder Creek is about 100 

feet deep where it turns to enter the canyon. Just 

beyond the point where rock appears in its banks it is 

joined by a brancl~ frolll the north, and between them 

at the fork stands a little rock hill that does not rise 

so high as the ,valley plain. It is inferred from the 

local details that at SOlne earlier time the canyon was 

single at its head, then it was flooded by alluvium to 

the terrace level, and when deposition was followed by 

erosion the stream courses were superposed on the 

bedrock of the range in such a way as to isolate a 

small tract of rock. 

Hague 64 mentions Pliocene beds in the valley, local 

gravel of pale color, but says nothing of their structure. I did not examine them and have only noted 

that outcrops of suggestive pale color appear at a 

number of points within 300 feet of the alluvial floor. 

On the northwest Mantua Valley is joined by a 

higher valley which may conveniently be called the 

Dry Lake trough. On the line along which they meet 

the trough is 300 to 400 feet higher than Mantua 

Valley. The upper floor is not so even as the lower' 

and is dissected by its drainage. The escarpment that 

separates the .two valleys is irregular in outline but 

may nevertheless be due to faulting; the presence of a 

fault is suggested by copious springs along its base. 

For the greater part of the Wasatch Range the only 

available maps are of reconnaissance grade, but the 

Dry Lake trough and the northern half of Mantua 

Valley, which are included in the Loga,n quadrangle, 

have been surveyed with the accuracy appropriate to 

publication on a scale of 1: 125,000. Contours from 

the Logan map are reproduced in Plate 29, to which 

the reader's attention is directed iri :connection with 

the following description. 

The Dry Lake trough follows the eastern base of 

the Wasatch Range for 16 miles. northward from 

Mantua Valley. At the south it is nearly 4. miles wide, 

at the north less than 2 miles, and its outlines, though 

they indicate a general trend, are somewhat irregular. 

On the east it is separated from Cache Valley by a 

ridge to which the same descriptive ,terms apply. 

Although this ridge has a well-marked' general trend 

it is irregular in details of outline and form. As its 

culminating point bears the name Mount Pisgah, 

the name Pisgah may conveniently be applied to the 

ent.ire ridge. At the south the Pisgah Ridge overlaps 

the ridge east of Mantua Valley; and the two constitute a compound upland that separates the Dry 

Lake-Mantua compound trough from the Cache Valley 

trough. The rocks of the ridge are Paleozoic, they are 

inclined at high angles, and their directions of strike 

are independent of the general trend of the ridge. 

A few strikes measured by E. H. Finch 65 are northwesterly and make angles of 300 to 40 0 with the general trend. The ridge evidently owes much of its 

irregularity to structural features, but its eastern slope 

is also diversified by erosion, being deeply scored 

. along lines of easterly drainage. 

6f Hague, Arnold, op. cit., p. 418, 1877. 

65 Mr. Finch's data were communicated by letter and at the time of writing are 

unpublished. 
60 STUDIES OF BASIN-RANGE STRUCTURE 

The drainage system of the Dry -Lake trough has 

three divisions. The southern third is drained along 

two lines southward to Mantua Valley and thence 

westward across the Wasatch uplift. The northern 

two-fifths is drained -eastward to Cache VaUey by a 

stream that crosses the Pisgah Ridge in Wellsville 

Canyon. An intermediate division drains to Dry 

Lake, which has no outlet. The southern boundary 

of the Dry Lake Basin is a low rock ridge; the northern 

boundary an alluvial fan from the Wasatch. 

The Pisgah Ridge, which is cleft to its base by 

Wellsville Canyon, is also cleft within a few hundred 

feet of the floor of Dry Lake trough by three other 

canyons. The Wasatch Range, which is cleft to its 

base by Box Elder Canyon, is deeply cleft also at two 

other points, one 2 miles north of Box Elder Canyon,' 

the other so related to the canyon as to partly merge 

with it. 

The floor of the trough is diversified by a system of 

small ridges, all of which make wide angles with the 

general trend of the trough. The trough trends about 

N. 20° W., the ridges about N. 40° E. A conspicuous 

character of the ridges is that the Paleozoic strata 

which compose them do not strike with their trend. 

In some ridges the dominan t strike is at rightangles 

to the trend. Because of this peculiarity of structure, 

and as a result of weathering, some ridges and parts 

of ridges are cross-ribbed, and' the crests of all the 

ridges show a series, of humps. 

The Wasatch face that overlooks the trough is composed, either:~polly or in chief part, of Paleozoic 

strata, and it is evident to distant inspection that 

their structufe, .i.nsteadof determining the trend of 

the face, is trunc'ated by the face. So both side walls 

of the trough, as well as its floor, have forms that are 

independent of that element of structure which is 

represented by the strike of inclined sedimentary 

rocks. - The trough is not a strike valley, developed 

by erosion along the· outcrop of a weak formation. 

Its situation as a sort of shelf on the slope from the 

range,crest,to Cache Valley precludes the suggestion 

that it originated as a stream valley. The only alternative hypothesis worthy of consideration is that it 

is a graben and that its floor has gone down between 

fault-determined walls at so recent a date that the 

disturbed drainage has not yet been fully readjusted. 

If 'there shall be no further tectonic changes the 

closed basin of ,pry Lake will eventually be filled by 

waste from the range and its waters will find ,outlet 

to the north or east. 

The cro ss ridges of the trough floor may be the 

crests of interstream ridges produced by erosion before 

the faulting that created the eastern waU, but their 

parallelism and their close order suggest rather that 

they, are edges of minor tectonic blocks that were 

dislocated with reference to one another at the same 

time that collectively they were dislocated with reference to the range and the Pisgah Ridge. 

The interpretation that correlates the floor of the 

Dry Lake trough with the rock floor of Mantua Valley 

and ascribes their present difference in height to a 

fault serves to explain a feature of the Mantua Valley 

that was not mentioned in the general description. 

The smooth alluvial blanket by which' the rock floor 

of the valley is concealed is interrupted at two points 

by short rock ridges, which run parallel to the ridges 

, of the Dry Lake trough and have the same peculiar 

topographic habit. They are on opposite sides of the 

valley and appear on the map (pI. 29) close to its lower 

edge. It is easy to surmise that when their rocks 

shall be examined the strikes will be found to diverge 

widely from the trends of the ridges. 

The deep clefts in the Pisgah Ridge are all of one 

type. They may be described as canyons leading 

from Cache Valley up to low saddles that are close to 

the west face of the ridge. In each cleft the contours 

represent the descent from the saddle as steeper on 

the' eastern side than on the western. So unless the 

difference in slope is determined by rock texture, the 

indication is that the divides are migrating westward 

and the canyons are lengthening at the head. This 

condition favors the view that the clefts have been 

developed' by headwater erosion. It is not, however, 

necessarily inconsistent with the view that the erosion 

of the canyons was begun before the dislocation of the 

ridge and graben and that the development of the 

clefts kept pace with the rising, or rising and tilting, 

of the ridge. 

The deep clefts of the ridge west of the Dry Lake 

trough open similar questions of interpretation, and 

these can not be fully answered without localexaminations, which have not been made, but approximate 

answers are indicated by the contours of the map. In 

the cleft 2 "miles north of Box Elder Canyon (see fig. 

43) the saddle lies a little east of the crest line of the 

range, and the passage at the saddle is wide. Eastward from the saddle the passage is also wide and the 

descent is gradual; westward the descent is accomplished by a steep, na.rrow canyon. The steeper 

descent, as well as the narrower way, indicates more 

rapid corrasion, and it is probable that the canyon 

of the western slope is being lengthened by headward erosion, that the divide is migrating eastward, 

and that a continuance of the process will move the 

divide beyond the eastern base of the range and thus 

establish a new line of cross drainage. But it is not 

to be assumed that headward erosion has developed 

the entire cleft. The broad passage from the summit 

eastward requires a different explanation. Two explanations may be suggested-first, that the passage is an 

air gap, a disused valley of cross drainage; second, 

that it was occupied by a local body of weak rock 

that has been washed out. 

The other stre'amless cleft in the ridge west of the 

Dry Lake trough does not ,cross the entire ridge but 

runs obliquely from Mantua Valley to the cross can-
WASATCH RANGE, UTAH 61 

yon of Box Elder Creek. This cleft is narrow throughout. On the north wall of the canyon it appears as a 

hanging valley 500 feet above the base, and the saddle 

within the cleft is not far back from the canyon wall. 

The hypothesis that the cleft is determined by a zone 

of weakness is not tenable here, because the presence 

of the zone is not indicated by the contours of the 

canyon wall. It seems clear that the cleft existed 

before the development of the canyon and was truncated by that development; and the probable history 

involves the hypothesis that the cleft was eroded by a 

branch of Box Elder Creek when the nlaID creek ran 

at the same level. ,Afterward the headwaters of the 

north branch were captured by the south branch, and 

then, with the growth of the range, the south branch 

and trunk stream deepened the canyon, and the notch 

in the mountain car'ved by the north branch was left 

as an air gap. 

As the clefts 8,re but 2 miles apart and have similar 

relations to Mantua Valley, it is probable that their 

general histories are similar. So the exclusion at one 

locality of the hypothesis of headward erosion along a 

zone of weak rock practically negatives that hypothesis 

for the other locality and leads to the acceptance of 

the air-ga,p explanation for both. 

DISCUSS! ON OF BACK V ALLEYS 

The evidence that the eastern margins of Mantua 

Valley and the Dry Lake trough are deterlllined by 

faults is strong; evidence of similar tenor as to the 

eastern lllargin of Ogden Valley is perhaps less cogent, 

and evidence as to Morgan Valley iR relatively weak. 

In view of the fact that the three valleys are similarly 

rela.ted to the 'Vasatch Range it seems proper to consider the data collectively instead of in three independent parcels, and the mutual support that COlnes 

with collec'tive consideration makes a strong case for 

determination by faults. With recognition of the, 

lines of dislocation comes the recognition of an additional character of similarity-each of the three lines 

is oblique to the Wasatch axis, trending more to the 

west than the adjacent part of the range. 

The westward canting of old grade plains on the 

Wasatch Range opposite Morgan Valley suggests, by 

indicating rotation of the range block, that the eastern 

face was determined by a fault, but the suggestion has 

not yet been tested by a study of structure on the 

eastern slope. Opposite Ogden Valley the physiographic evidence of a fault between the main range and 

the eastern foothill belt appeals strongly to the eye. 

It is possibly supplemented by the observation of an 

oxtensive shear zone on th~ plane of' the inferred 

normal fault, but at the point of observation, near 

Eden Pass, the plane of that fault either coincides with 

or approaches closely the plane of the Willard overthrust, so that the crushing of rock nlight be referred, 

with perhaps equal propriety, to the more ancient 

dislocation. The floor of the Dry Lake trench is a 

feature so distinct in attitude and type from the 

adjacent lofty range face as to suggest separation by 

dislocation. Despite the knobs by which its surface 

is diversified, that part of the floor south of Dry Lake 

is essentially horizontal in its east-west profile, and 

north of the lake the rock floor is concealed by a'great 

bank of alluvium that has been washed from the steep 

face of the range. Once more it appears proper to 

consider data for the three valleys collectively instead 

of separately, and if taken all together the evidence 

of dislocation on the west side is strong. 

It is probable, therefore, that the range is bordered 

on the east, for at least 40 miles, by a series of grabens-that the depressions just east of the range, 

instead of repres~nting the lower edge of a broad 

range block tilted eastward, really represent local 

subsidence between faults. 

It is worthy of remark that the structural classification, which coordinates Morgan and Ogden Valleys 

with the Mantua-Dry Lake depression, is not the 

classification of the geographer. The Pisgah Ridge is 

so small and lies so near the main Wasatch crest that 

it has properly been regarded as a subsidiary feature 

,of the Wasatch Range. The upland east of Ogden 

Valley is both high and broad; and its front, although 

much broken by dissecting s'treams, falls in line with 

the fronts of Morgan Peak at the south and the Bear 

River Range at the north. Parallel to the -line of' 

fronts, and overlooked by them, lie Morgan, Ogden, 

and Cache Valleys, also in line and separated· by hilly 

tracts of moderate height, and these mark the eastern 

boundary, albeit indefinite, of the northern part of the 

Wasatch upland. The upland east of the valleys has 

not yet been satisfactorily named, and the settlelnent 

of its nomenclature, now confused, lllay perhaps await 

the completion of adequate Inaps. In a vague way 

it has been called the Bear River Plateau; its western 

part has been included under the title Wasatch 

Mountains; a crested portion opposite Cache Valley 

has been nanled the Bear River Range, and the same 

title has been applied also to the Morgan Peak.'mass. 

Pliocene lake beds have been found in Morgan, 

Ogden, and Mantua Valleys as well as in Cache Valley, 

bu t not in the Dry Lake trough. As the beds show 

many outcrops at low levels but are not known to 

occur high on the valley, sides, it is· inferred that the 

valleys were already in existence' in that -lacustrine 

epoch. Because the beds show strong dips, with other 

evidences of dislocation, in at least two of the valleys, 

it is inferred not only that the sunken tract has suffered 

diastrophic change since the lake epoch but also that 

the rock floors of the valleys are composed, like that 

of the Dry Lake trough, of groups of minor blocks 

instead of single large blocks. 

The same three back valleys received bays of Lake 

Bonneville and were aggraded to the condition of 

smooth plains during t.he Provo stage of that lake. 

Subsequent trenching of the Provo plains has not un-
62 STUDIES OF BASIN-RANGE STRUCTURE 

tovered the base of the alluvial deposits. Slopes of 

bordering uplands that appear to be erosional meet 

:the aggraded plains in such way as to indicate that the 

base-level to, which they were adjusted lay not only 

below the present stream channels but below 'the rock 

sills across which the valleys drain westward; and this 

inference is sustained in Ogden Valley by borings that 

penetrate below the level of the rock sill without reaching the base of the alluvial fill. It is inferred that at 

some late epoch in the history of the valleys the erosion 

of their floors was checked and aggradation was determined by a diastrophic cha,nge that increased the 

anlount of displacement between the range and the 

valleys. 

This particular differential movement occurred in 

pre-Bonneville time, and it was subsequent to the 

principal disturbance and principal erosion of the Pliocene lake beds. It may be assumed to have been but 

one of many movements involved in the growth of the 

range and the subsidence of the back-valley grabens. 

An earlier movement of similar character may have 

determined the capture of the Eden Pass stream by 

Ogden River. ' 

There is a certain analogy of position between the 

back-valley grabens and the little grabens of earth in 

the zone of the piedmont scarps; and this analogy 

suggests that the back-valley grabens may be subsidiary features of a fault by which the Wasatch Range 

rose in relation to the crust blocks east of it--that 

the movements connected with the formation of the 

eastern Wasatch fault tended toward the creation of 

a crevasse, and that the potential crevasse was filled 

by the subsidence of wedging crust fragments. 

Parleys Park lies at the eastern base of the range at 

a place where the range is exceptionally broad. Investigation may perhaps find it to be a site of local subsidence. The deep alluvial deposit in Rhodes Valley 

tells of a preexistent hollow, and local subsidence is _ 

a. possible cause of the hollow. A southward extension 

of the disturbed belt that includes the recognized 

back-valley grabens is thus suggested. 

Heber Valley, although outside the influence of the 

Bonneville changes of base-level, has a broad alluvial 

floor, the result of aggradation in a preexistent hollow. 

The sill of the outflowing stream appears to have 'been 

raised by an upward movement of the range that was 

not shared by the crust block beneath the valley. 

To that extent its history resembles the history of the 

northern back valleys. 

THE WASATCH A HORST 

The study of the back valleys has served to lllodify 

considerably my conception of the dislocations involved in the production of the Wasatch Range. The 

eastern fault and associated grabens evidently belong 

to the later or post-Eocene period of diastrophism and 

are companions in origin with the western or frontal 

fault. The range, instead of being the higher edge 

of a tilted fault block, is essentially a horst. The 

western fault has much the greater throw, and it is 

probable also that the two faults, although both normal, differ notably in type. Fragments broken from 

the descending block on the west side have lodged on 

the slope of the horst, where they constitute spurs of 

the range. Fragments broken from the descending 

block on the east side have dropped below the level 

of the block, as if slipping into a crevasse. These 

characters are doubtless significant of the nature and 

directions of subterranean forces, and they constitute 

data for the use of the future student of the dynaniics 

of the Great Basin corrugation. , 

In this connection it is to be noted that the Wasatch 

Range is on the common border of two tectonic units 

or provinces whose areas are large as conlpared to 

those of individual mountain ranges. The eastern 

province once stood lower than the western, so as to 

receive waste from it, and these relations were afterward reversed. In a general way the period during 

which the eastern province was lifted corresponds to 

the period of range creation, although exact correlation can not, from present knowledge, be asserted. 

So the uplift of the Wasatch, occurring at the edge 

of the rising broad province, may owe to that fact the 

peculiar asymlnetry of its development. 

, THE THROUGH CANYONS 

Four of the canyons of cross drainage have received 

critical attention, and as these have comnlon characters they may be assunled to be representative. 

Their walls are steep and consist in 'considerable part 

of cliffs. They are narrow at the bottom; in places 

the stream channels occupy the entire space, but 

elsewhere they are bordered by strips of flood plain. 

Bedrock is. not visible in the channels; the streams 

flow over beds of boulders. The side slopes indicate 

that the deposit of boulders is not deep. Outside 

each canyon mouth is a large body of gravel and sand 

accumulated as a delta in Lake Bonneville'during the 

Provo epoch, and through this material the modern 

stream has opened a valley. Scattered alluvial tel''' 

races within the canyon show that during the making 

of the delta it was filled with similar lnaterial up to a 

grade plane conformable with tha~ of the delta. 

Each canyon holds its characters to the mouth. 

There is no flaring, but the stream passes abruptly 

from its narrow strait between rock walls to its wide 

terraced valley through the delta. As shown in Plate 

8, B" the canyon is sharply truncated by the plane of 

the frontal fault. 

Ogden Canyon is exceptional in that it contains a 

flood plain of some width, a plain that affords space 

for a group of summer cottages, and for, this special 

feature there is a special explanation. Some of tho 

gravel that occupied the -canyon during the Provo 

epoch was cemented by a calcareous deposit from 

thermal springs, and the resulting conglOlnerate has 
WASATCH RANGE, UTAH 63 

resisted erosion and retarded the river in its work of 

clearing out the acculllulation of detritus. 

r:rhere is ftn exception also to the rule that the canyon streanlS flow over boulder beds instead of solid 

rock, and the exceptional locality has special features 

that serve to explain the anomaly. Brief mention of 

these features has been made by Lee,66 but a fullf'r 

account is warranted by the v~lue of the locality as 

a.n object lesson in superhnposed drainage. Midway 

ill its canyon Weber River is joined by a mount.ain 

cteek COIning fro III the south, and that strealll delivers 

a. large load of coarse debris. While Lake Bonnevillf' 

stood at its highest level the canyon was occ:upied by a 

strait, and into this strait the creek dumped its debris, 

building a steep conical delta that projected as a 

~ape and approached the opposite shore. Afterward, 

when the water fell to the Provo level and the strait 

Was replaced by a narrow river valley with gravelly 

flood plain, the creek cut away most of its earlier 

delta but shaped another at a lower level, and the new 

delta was ext(:juded so fal' as to crowd the river against 

the north side of its valley. The river attacked the 

valley wall and carved a notch in it, so that later, 

when the lake fell and the river began its final work of 

erosion, the river rested at this one point on a shelf of 

rock. So soon as it had corraded a channel in the 

tock shelf its course becallle fixed, and the old course 

Was nevel' resumed. On this bit of new course the 

river has cut a nal'row gorge. FrOln other parts of 

the canyon the greater part of the deposit of the Provo' 

stage has been washed away, but here a large body or 

it renlains, and opposite the body of gravel is the narrow defile-the Devil's Gate-in which both walls 

!1nd bed are of solid gneiss. The Union Pacific Railroad follows the line of the old channel, and its grade 

11lakes a deep cut through the gravel deposit. 

The n10uths of three of the canyons are crossed by 

piedmont scarps which demonstrate fault lnovenlents 

since the Lake Bonneville epoch. The steep and 

rugged canyon walls (see pI. 25, B) testify to recent 

active corrasion of the beds and support the view that 

the block is rising and is being sawed into sections by 

the streams as it rises. Nevertheless the streams are 

now separated from the rock of the canyon beds by 

layers of boulders. This incongruity is probably a 

result of the Bonneville episode. Time is needed for 

the reJl10val of the Bonneville detrital deposits, and 

thu,t work is still unfinished. 

DISCUSSION OF CROSS DRAIN AGE 

]~den Pass and the air gaps at and near Box Elder 

Cn,nyoll testify to the fonner existence of streanlS crossing the Vi.,Tasatch Range where now the waters are 

parted by the range. Those streams were decapitated 

by Ogden River and Box Elder Creek, which there-

, fore must have been their contemporaries. Thus lines 

66 Loo, W. '1'., Guidobook of tho westorn United States, Part B, The Overlanrl 

, Houto: U. S. 0001. Survoy Bull. ()12, p. 91, 11l.5. ' 

of drainage are shown to have crossed the northern:. 

part of the range at a time when the range was less 

developed than now. As indicated by the present 

heights of the passes, the subsequent uplift of the 

range in their vicinity has been 800 to 1,200 feet. In 

this way the history of cross drainage is carried back 

through a fraction; probably a minor fraction, of the 

life of the range. 

The air gap associated with Box Elder Canyon 

shows a bifurcation of cross drainage that is peculiarly 

significant. In Figure 43 the shaded area represents 

the bedrock of the range, separating the alluvium of 

Mantua Valley at the east from the alluvium of the 

Salt Lake plain at the west. Box Elder Creek, which 

runs from B to F;, crosses the range in a canyon, the 

bed of which is about 1,800 feet below peaks on either 

side. At D it is joined by a minor branch, FD, and 

in the fork is a small triangle of rock. As explained 

on page 59, the Y -form plan of the drainage was superimposed during the Lake Bonneville epoch by an 

alluvial fill that spread over Mantua Valley and extended through the canyon. The gravel of that fill 

F 

FIGURE 43.-Plan of drainage across Wasatch Range, Utah, at and ncar 

Box Elder Canyon 

still rests on and against the triangle of rock in the 

fork. With future lifting of the range and deepening 

of the canyon and the upstream channels, the basin 

of the stronger branch will gro)V larger at the expense 

of the weaker, and when the s111aller branch is at last 

decapitated its course in the rock will be stranded as 

an air gap. 

The air gap that exists at the present time has the 

position indicated at A. The summit within the gap 

is 800 feet above the canyon bed. The approximate 

course of the stream that .once flowed through, it is 

represented in the figure by a broken line. That 

stream joined the Box Elder Creek of its time at 

some point, C, in the heart of the range and west of 

the axis. The Y -form plan of the ancient 'drainage 

may have originated, like the smaller Y of the modern 

drainage, by superilnposition, but it is also possible 

that the streams of the Y had acquired their courses 

before the uplift of the range and. were strictly antecedent. The triangular tract of rock embraced by the 

arms of the ancient Y is much wider than that of -the 

modern Y, and its crest presumably rode higher above 

the stream beds. Much of its volume has been eaten 

aw.ay in the development of the 'mo.derncanyon, aJ;ld 
64 STUDIES OF BASIN-RANGE STRUCTURE 

the crest of the remnant stands now only about 100 

feet above the saddle at A, but when the main branch 

of the creek ran at the same level with the A branch, 

the intervening crest line was probably 500 feet above 

either channel. The hypothesis of superimposition 

thus seems to imply a deep buri~l of the range after 

the growth of the range had begun, and it thereby encounters difficulties that are escaped by the hypothesis 

of antecedence. More probably the branching cross 

drainage was established before the uplift of the range. 

Unfortunately this air gap was not discovered during my field examination, so that inferences from it 

depend wholly on the form features expressed by the 

'contours on the map, but the evidence as it stands 

poin ts decidedly toward an tecedence as the explanation of the cross drainage. 

If the tract drained by streams crossing the range 

acquired its present drainage system through retrogressive development by st~eams that began 0:Q. the 

western face of the range, then during the early history 

of the range the tract was drained in other directions. 

And if the tendency to form grabens along the east 

base of the range was early manifested, the sag valleys 

would be likely to assemble the water falling on the 

adjacent face of the range and guide it northward and 

southward to the ends of the range. Such a drainage 

systenl, if once established, would not be easily broken 

up. This suggestion is not regarded as of special inlportance, for the reason that the graben development 

most clearly determined is associated with the later 

history of the range. It is worthy of note, hO'Yever, 

that the dislocations which produce grabens have not 

diverted either Weber River or Ogden River. Both 

streams rise far east of the graben belt and cross the 

tectonic sags as independently as they cross the tectonic ridge. 

Whenever the problem of Wasatch cross drainage 

shall be comprehensively investigated its study will 

necessarily include a study of the drairlage problems 

of the western part of the Uinta Range. The fact that 

the upper Weber and upper Provo, which rise near the 

summit of the broad Uinta anticline, flow for many 

miles with the strike instead of the dip requires explanation, and the explanation, when attained, will 

contribute to an understanding of the history of the 

two ranges in the region of their near approach. 

The history of the Wasatch drainage interlocks also 

with the history of the Pliocen~ lakes. Despite the 

dislocations that the lake beds have suffered, they are 

still confined to rather low parts of the three lowest 

back valleys, and their general relations are identical 

with those of the Pliocene lake beds iIi Cache Valley. 

The present passes from valley to valley are so high 

that the valley lakes can not be supposed to have been 

directly connected as a chain, but their association is 

readily explained on the assumption that preexistent 

canyons' through the 'Wasatch joined their waters to 

those of a lake west of the range. It is true that the 

vestiges of the western lake have not been identified 

along the ~est front of the range in the vicinity of the 

through canyons, but they were noted farther north by 

Hague,67 and their southward extension may fairly be 

assumed. The belt of country in which they should 

exist was occupied by Lake Bonneville, whose sediments bury the' sediments of earlier lakes and whose 

littoral records make difficult the recognition of 

earlier littoral records. If the Pliocene lake waters 

were connected across the range the cross canyons 

antedate them, and some of the main lines of cross 

drainage must have been established before that lake 

epoch. 

At some time between the deposition periods of the 

Eocene conglomerates and the Pliocene lake beds the 

uplift of a broad region east of the Wasatch changed 

the general direction of descent in the Wasatch district from eastward to westward. Between the same 

time limits began the uprising of the Wasatch Range. 

With the data now available the sequence of these 

events is not evident. Probably neither of the changes 

was of simple character, and through their diverse 

factors the local drainage may have been rearranged 

more than once. It may never be possible to determine whether the present cross drainage antedates the 

entire life of the range or was consequent on some stage 

of its growth-such a question is perhaps academic-

.but with reference to the Pliocene and later growth of 

the range there need be little doubt that the cross 

drainage is mainly antecedent. 

FAULTS WITHIN THE RANGE 

Periods of diastrophisnl are usually distinguished 

by means of unconformities, but in considering the 

disturbances of the Wasatch region I find it more 

convenient to use the frontal fault of the range as a 

basis of classification. So far as we know, the growth 

of the range has been coincident with the development 

of the frontal fault. The frontal fault transects folds 

and faults older than itself. The diastrophism that 

produced those folds and faults will here be spoken of 

as the earlier and the diastrophism contemporaneous 

with the frontal fault as the later. 

The normal fault that borders the range, for at 

least a part of its length, on the east may be referred 

with confidence to the later period, and so may the 

associated grabens. The grabens are not simple 

blocks but composites. On the west side of the range 

are the fault-block spurs and also the fault-block 

ridges near Santaquin, both indicating that the crust 

block that went down on that side did not go down 

as a simple unit. Thus the crustal members that 

fell away from the two sides of the Wasatch horst 

were each more or less broken as they descended; and 

it is of interest to inquire whether the horst itself was 

broken at the same time. As the horst contains the 

67 Hague, Arnold, and Emmons, S. F., l)l}Scriptiv9 geQ1o~y: V, l:l. QOQl. Expl. 

~th Par. Rept., vol. 2, p. 406, 1877. . 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 29 

R .I W. 

MAP OF DRY LAKE TROUGH AND PART 01<' MANTUA VALLEY, UTAH 

Scale gooo 

EE"3~==E=~~~E=======~c=======~~======~C======== ========~5 ~es 

Contour interval 100 feet. 
U. S. GEOLOGICAL SUHVEY PHOFESSIO ' AL PAPEH 153 PLATE 30 

A. NOH.TH WALL OF PROVO CANYON 

orth of the canyon is the Till"lpanogos ridge, trending northward. Part of its western face, a falLit scarp, appears in the view at the leCt of the central crag. The ravine at. the right of the crag follows the line of a minor fault. The sLrala are Paleozoic aod chiefly limestones 

At the left is Cambrian quartzite. Beyond Ogden Valley is the Bear River H.ange 

VIEWS IN WASATCH RANGE, UrAH 
WASATCH RANGE, UTAH 65 

ancient structural features that have been truncated 

by the western and eastern faults, it is evident that 

the inquiry involves the discrimination of products of 

the later from products of the earlier diastrophism. 

An evident criterion for discrimination pertains 

to form. Just as lnarginal faults of the later period 

are expressed in the present topography, so may 

be interior faults of the same period; but the initial topographic expression of the older faults has 

been lost, and such expression as they now have 

has been wrought by erosion and depends wholly 

on the distribution they gave to strong and weak 

rocks. 

A second criterion involving form is connected 

with grade plains and may conveniently be stated 

in terms of the features observed in the Farmington 

region. The Farmington grade plain, which was 

carved in a period of rest that preceded the formation of the frontal fault, transects the structural 

features of the earlier diastrophism. Whatever dislocation or deformation it exhibits-for example, 

it.s tilting-is referable to the later diastrophism. 

A third criterion pertains to deformation and 

depth. One of the conditions that determines foldIt will be seen by reference to the map that the general shape 

of the western slope of the ridge is that of a pair of steps, the 

first rise being of about 3,000 feet to an outlying shoulder, 

from which the main ridge rises, about 2 miles farther back, 

in a steep, almost perpendicular wall. Here again, as so frequently in the Rocky Mountain region, the physical structure 

gives the clue to the geological. Timpanogos Peak is fbrmed of 

horizontally bedded limestones having at the most an inclination of 30 east and 10 or 20 to the south. * * * The 

topography suggests that the line of junction of this lower 

shoulder with the face of the upper wall is that of a line of (ault, 

and this idea is confirmed, as will be seen later, by the finding 

of faultings in the canyons of the Provo and American Fork, 

at either end of the ridge, in corresponding position. 

In the ridge of Provo Peaks the continuance of this line of 

fault is shown also in the topography, as well as rendered 

necessa~y by the thickness of the strata observed. 

Plate 21, A, shows the lower and upper escarpments 

of Mount Timpanogos, with suggestion of the shoulder 

between them; and an oblique view of the upper 

escarpment appears in Plate 30. The faulting is 

here connected with the later period by the fact that 

the dislocation between the shoulder and the high 

crest still finds direct expression in. the topography. 

Plate 30 shows also that the upper block is itself 

divided into two parts, the strata of which dip toward 

their common boundary, and that the boundary is a 

N. Mount Timpanogos Provo Peak5 s. 

~---::::::::-.~-:=;;: : 

American 

fhrk 

\ 

Bailie 

Crt:t:k 

Provo 

River 

Rock 

Canyon 

Slate 

Cal!)'on 

FIGURE 44.-Profile elevation of a portion of the Wasatch Range near Utah Lake, showing the main crest and a shoulder or terrace of the 

western face 

ing, instead of fracture, as a result of strain is superincmnbent load. Because this is not the sole condition its application is sOlllewhat indefinite, but 

it is true in a general way that folds are not made 

in strong rocks near the surface. Because denudation occurred between the two periods of diastrophism it is evident that the rocks now visible at 

the surface were in general lnore deeply buried and 

more heavily loaded during the earlier diastrophism 

than during the later, and the folds of strong rocks 

are therefore as a rule to be referred to the earlier 

period. 

A fourth criterion is connected with cementation. 

Those parts of the earlier shear zones that are now 

visible have become visible through denudation, 

and before they were exhumed they were in general in 

the zone of cementation and there acquired continuity 

and strength. Some of the shear zones of the later 

diastrophism have probably escaped cementationin their visible parts-and are for that reason easily 

eroded. Therefore faults of the later period are more 

likely than faults of the earlier period to receive 

through erosion the topographic expression of weak 

forlnations. 

In a description of the Timpanogos and Provo divisions of the range Emmons 68 says: 

.. Hague, Arnold, and Emmons, S. F., op. cit., p. 345. 

groove or ravine which runs parallel to the upper 

escarpment and is traceable upward to the sky line. 

The fault thus indicated has not been investigated, 

and the direction of its throw is unknown, but the 

topography indicates that its outcrop has proved a 

line of weakness to which the local drainage is adjusted 

and thus suggests an uncemented shear zone of the 

later diastrophism. Just outside the field of view, 

at the right, is a second ravine which separates blocks 

that do not agree in the direction of dips. Thus the 

section of the range shown in the north wall of Provo 

Canyon includes at least three internal faults that 

were probably made during the uplift of the range. 

All dip more steeply than the frontal fault. One 

is known to involve a downthrow, on the west side, 

of several thousand feet. 

The last-mentioned fault, the one described by 

Emmons, is at least 20 miles long and is parallel to 

the frontal fault. Its throw is probably greatest near 

Provo Canyon but diminishes slowly northward and 

more rapidly southward. The two blocks separated 

by it are shown in longitudinal profile in Figure 44, 

which is not a perspective view but a right projection, 

plotted from data of maps and photographs. The 

lower and nearer block, gashed at a few points by 

cross drainage, is otherwise so little eroded that its 

topographic profile indicates clearly the original form . 
66 S'fUDIES OF BASIN-RANGE STRUC'rURlU 

of the block. The higher block, wasted from the 

opposite side as well as frOlll the nearer, ~as lost its 

original form and acquired an acute, serrate crest. 

The general dips in both are eastward and gentle, but 

to this rule there are notable exceptions. The lower 

block contains north of American Fork Canyon the 

steep dips shown in Plate 21, B, and includes in the 

neighborhood of Rock and Slate Canyons the anticline illustrated by Figures 4 and 5. Those defori1lations dearly belong to the earlier diastrophism; for 

they have no expression in the profile and are truncated 

by the. frontal fault. 

Between Battle and Provo Canyons are two. large, 

steep-sided. hills that seem; as seen from Utah Valley, 

to stand on the shoulder or terrace of the lower fault 

block. Their position, which is imperfectly shown in 

Plate 20, B, is well back from the front of the terrace 

and hear the escarpment of the higher fault block. 

They are composed of strata that dip at a high angle 

to the north and are thereby .contrasted with neighboring parts of the two greater blocks of the range, 

where only gentle dips are shown. They are tentatively explained as corners of two minor blocks, separated by faults from the greater blocks and rotated 

northward-or, perhaps more properly, as huge 

horses held in the fault zone between the greater 

blocks. If the suggested explanation is correct, their 

dislocation is a product of the later diastrophism. It 

is surmised that the curved ridges seen in the foreground of Plate 30 are in some way :r;elated to them. 

The fault scarp above the terrace, best shown in 

Plate 30, differs notably from the scarp below the 

terrace, shown in Plates 19, B, 20, A, and 21. It 

has no smooth facets but is a rugged cliff buried at 

the base by talus. As the slope of the terrace corresponds in angle to the dip of the frontal fault, whereas 

the cliff is steeper, it is evident that the fault which 

produced the cliff has a dip steeper than the angle of 

rest. This steepness permits gravitational wasting 

and probably suffices to explain the ruggedness of the 

cliff. 

The evenness of profile of the terrace constituted by 

the long western' block may have been somewhat 

exaggerated in drawing Figure 44 but is nevertheless 

a strongly marked character. It indicates that a 

portion of the prefault surface is here preserved with 

little loss from postfault wasting and thus gives support to the inference from grade plains of the Farmington district that the Wasatch region was reduced 

to a condition of low relief before the period of range 

development. The fact that the drainage of the 

upper surface of the block issues through a small 

number of canyons shows that the surface slopes eastward (see also pI. 21, A) and thus indicates that the 

uplifting of the block was accompanied by a tilting 

toward the east. 

In the Cottonwood region the later studies of structure, studies more or less connected with the mining 

industry, have discovered nlany faults, but nearly all 

of them have been referred to the earlier diastrophislIl, 

and those that might possibly have later origin are. 

all of small displacement.69 The interior faults in the 

Ogden .. Willard region, described by Blackwelder, are 

regarded by him as older than the range. The small 

cross fault observed at the reservoir locality (p.t'!) is 

a contemporary of the frontal fauit. two othet interior faults; known to me only {rom distant views; rt1ay 

ptove on investigation to belong to the later pei'iod. 

One of them; seen in the face of the range betweetl 

North Ogden Canyon and Pleasant View; has a high 

dip with a throw to the west. The other, near the 

crest of the range opposite Richville, has a throw to 

the east. 

This review of interior fauits of the later pel'iod 

covers, very imperfectiy, iess than haH the area of the 

range. lt leaves the impression that the rising block 

of the range was less subject to interIor fracture ·than 

the adjoining descending biocks; though at the same 

time it shows that the horst is not to be regarded as 

an immovable mass from which other masses siumped 

away but rather as a free ctustal unit strained along 

with its neighbors by the orogenic forces; 

REVIEW OF RANGE STRUCTURE AND RANGE HiSTORY 

The subjects treated in this chapter are so interlocked that an orderly presentation was found impracticable, and the results of the inquiry are conseqllently 

scattered through the preceding pages. In the following paragraphs the more significant results are asselllbled and rearranged. ' 

The range is a structural ridge, uplifted between 

two faults. The western or frontal fault is the greater. 

It is' determined as a fault by structural and physio~ 

graphic evidence. The structural evidence consists 

of products of friction observed on and in the footwall, 

including fault gouge, breccias, horses, and' slickensides. The physiographic evidence includes (1) an 

escarpment, with alined base and alined facets, w' ich 

truncates the sculpture· and antecedent structure of 

the range and which is bordered by a wide alluvial 

plain, and (2) piedmont scarps. 

The ground plan of the fault is neither straight nor 

approximately straight but includes notable flexures 

stnd some angular turns. I ts bends are explained as 

features of the original fracture determined by preexisting structure. Some, but not all, of the controlling structural 'features are visible. The greatest of 

the visible controlling structural features is a body of 

granite, in passing which the fault is deflected several 

miles. The average dip of the fault is 340 • The 

direction of slip was with the dip. A conservative 

estimate of the throw, made in the region of Cottonwood Creek and Jordan Valley, is 10,000 feet. 

69 See especially Butler, B·. S., and Loughlin, G. F., A reconnaissance of the Cottonwood-American Fork mining region, Utah: U. S. Geol. Survey Bull. 620, pp. 

178-182, 1915. 
WASATCH RANGE, UTAH 67 

The east-side fault was determined wholly from 

physiographic chnracters, but the determination may 

be checked by study of structural characters, for the 

thrown block is not everywhere concealed by alluvium, as is the t~ll'own block on the west side. One 

physiographic character is an escarpment, well alined 

for about one-fourth of the length of the range. This 

escarpnlent truncates the internal structure of the 

range and is in part buttressed by hills of contrasted 

constitution. In another place differential movenlent 

at the supp'osed position of the fault is shown by the 

aggradation of a valley (Heber Valley) that had previously been excavated by a stream that flowed fronl 

the valley westward across the range. The line of 

the fault was examined at a few localities only. 

In the northern third of the range the eastern fault 

is characterized by large grabens, and the dropped 

blocks are theInselves broken by cross faults. The 

frontal fault scarp is buttressed by several spurs, each 

consisting of a fault block separated from the descending valley block and lodged at an intermediate height. 

The range block is locally divided by faults made 

during the period of uplift. These structural features 

created during the growth of the range are superposed. 

on structural features of earlier origin. 

Before the range arose its site-or at least a part 

of its site-was a tract of land of low relief, as is 

shown by reInnants and other vestiges of a peneplain. 

The record is spread over a large area of the range 

between Salt Lake City and Weber Canyon and 

includes the top of a long, narrow subsidiary block of 

the range opposite Utah Lake. At the north the 

peneplain was developed on Archean and Paleozoic 

rocks; at the south, on Carboniferous rocks. Between 

the two localities lies a great syncline which brings 

Jurassic rocks below the general level of the peneplain, and by inference the period of peneplanation is 

later than post-Jurassic diastrophism. On the eastern 

borders of the range Emmons found the older rocks, 

Archean to Jurassic, overlain by a fresh-water formation-now regarded as largely terrestrial-referred to 

the Eocene, but the relation of the peneplain to the 

Eocene has not yet been established. One of the 

fault-block spurs on the west side of the range, the 

City Creek spur, is composed of Tertiary conglomerate 

resting unconformably on deformed Paleozoic strata. 

This conglomerate, which Emmons tentatively and 

plausibly correlated with the Eocene formation of the 

eastern flank, has been itself warped and faulted, and 

after its dislocation a plain was graded above it. The 

relation of that graded plain to the peneplain on the' 

range has not been established; it may be of the same 

age or it may be n10re recent. "" 

These inlperfectly correlated data, although the'y 

fail to fix the date of the birth of the range, serve to 

show that the period of ~iastrophism to which its 

growth belongs is distinct from the period of the great 

post-Jurassic revolution, being separated by the period 

of quiet in which the peneplain was developed. The 

period of the peneplain, which ilnmediately preceded 

the birth of the range, may have coincided with that 

of Eocene deposition a few miles farther east, or it Inay 

have followed not only Eocene deposition but the 

dislocation of the Eocene strata. 

After the range had achieved the greater part of its 

growth a row of valleys along its eastern base was 

occupied for a time by lakes; and the lake beds, which 

are correlated with similar beds in Cache Valley that 

carry fossils, have been referred to the Pliocene. Still 

later the flanks of the range were washed by the waters 

of the Pleistocene Lake Bonneville, and the beaches of 

that lake were afterward dislocated by moven1ents on 

the frontal fault. The same moven1ents made piedmont scarps in Pleistocene lnoraines. By these 

phenomena the period of range growth, begun at some 

earlier Tertiary date, is shown to incl~de Pliocene, 

Pleistocene, and Recent time. 

The land east of the range is higher than the land 

west of it. At the tilne of the Eocene deposition the 

western region was the higher. The change in relative 

altitude affected large areas and should be classed as 

epeirogenic. Its period and the tilne of its beginning 

are only indefinitely known. One effect of the change 

was the reversal of the general direction of drainage in 

the Wasatch region. At the present time a number of 

streams from the eastern upland to the western lowland cross the Wass,tch axis. The canyons by which 

they cross were already in existence at the tilne of the 

Pliocene lakes. The relations of an air gap to one of 

the canyons seeln most easily explained by assmning 

that the lines of cross drainage were established before 

the beginning of the range uplift. There is need, however, of further investigation, and it is probable that 

when the questions as to the origin of the cross drainage shall have received full attention light will be 

thrown on the relation between epeirogenic and oro~ 

genic changes in the Wasatch region. 

REVIEW OF PHYSIOGRAPHIC CHARACTERS OF MAR .. 

GINAL FAULTS 

The great fault of the Wasatch was originally recognized by the escarpment it has created. Afterward 

the piedmont scarps were discovered, and their evi: 

dence was regarded as confirmatory. Further confirmation has now been found in the structure created by 

fault friction. Because the physiographic characters 

of the Wasatch escarpment did not prove misleading, 

it seems proper to infer that similar characters may 

be used as criteria for the recognition of faults at the 

margins of other ranges.' Among the characters of the 

Wasatch escarpment are these: (1) Its base line, 

although making many turns, follows a course that is 

independent of the sculptural features (canyons and 

ribs) of the range; (2) wherever the rock of the range 

is strong the ends of the ribs are faceted; (3) the 

facets are alined as if parts of the same warped surface; 
68 STUDIES OF BASIN-RANGE STRUCTURE 

(4) the base line, although somewhat adjusted to thE; 

distribution of strong and weak rocks, is largely independent of that distribution and is wholly independent 

of the strike of strata" folds, and faults within the range. 

The more noteworthy of these characters are summarized by saying that the escarpment truncf!,tes the 

sculpture and structure of the range. 

If a truncating escarpment can be produced only 

by faulting its presence on the face of a range is demon~ 

strative of a marginal fault; if it can be produced in 

other ways its presence is less than demonstrative. 

The other possible agencies of production are all 

erosive-ice erosion, wave erosion, wind erosion, 

stream erosion. Ice erosion need not be discussed, for 

the intermont valleys have not been occupied by 

glaciers. Wave erosion may be dismissed with a word, 

for the conditions require its application at the bottoms 

of intermont valleys, where efficient waves can not be 

generated. 

Theoretically, in a land so arid that the wind is the 

dominant agent of erosion, a range that borders a 

plain and that is attacked by prevailing winds parallel 

to i,ts base may be sapped at the base by eolian lateral 

corrasion and may thus acquire a truncating escarpment. Because I have not seen such a wind-made 

escarpment!and have looked in vain for pnotographs ' 

or contour maps representing one, I am skeptical as to 

their existence in the United States, but the possibility 

remains that they will yet be discovered. An earmark for the recognition of a wind-made truncating 

escarpment is the presence at its base of a piedmont 

plain of rock, continuous with the rock of the escarpment, but this mark of identification might fail in 

consequence.'cof a conceivable climatic change. Should 

the extreme aridity necessary to give the wind dominance in the piedmont belt be followed by moderate 

aridity, the rock platform might be buried by alluvium. 

Stream erosion unquestionably produces -truncating 

escarpmen ts, for a pair of them are made by every 

mountain creek that digs a canyon athwart the strike 

of formations and faults; but canyon-wall escarpments 

are not marginal to ranges. It is true also that as the 

down cutting of a canyon bed approaches base-level, 

. side cutting begins to sap the walls and thereby makes 

them retreat; and the question thus arises whether 

intermont valleys of the Great Basin may have been 

developed from medial canyons by the retreat of the 

canyon walls and thus have come to be bordered by 

escarpments that truncate sculpture and structure. 

The question can be treated only in a deductive way, 

because no streams through intermont valleys are now 

sapping the side walls. It is necessary to postulate a 

humid period with large rivers, followed by a less 

humid period in which have grown the alluvial aprons 

that now keep the intermont streams away from the 

valley walls. We may here ignore the difficulty of 

providing competent rivers for all the valleys that 

would need them and restrict attention to the type of 

mountain front that would result from such a process 

of valley formation. During the long time required 

for the development of one of the valleys through 

lateral corraf?ion by its trunk stream, the streams 

rising in the bordering uplands would not only adjust 

their grades to base-level but near their mouths would 

develoll flood plains. They. 'Yould, moreover, work 

selectively, opening wider flood plains in weak rocks 

than in strong. Then when changes of climate, by 

inducing deposition in the main valley, led to the building of alluvial aprons along its sides, those aprons 

would extend up every tributary valley and give to the 

rock base of each bordering upland an indentate outline. 

If the face of the upland retained such a slope that it 

might be called an escarpment, the escarpment would 

not truncate the sculpture of the upland but would be 

adjusted to it. It would still traverse the structure, 

but in an irregular manner, with much adjustment of 

its basal outline to the distribution of strong and 

weak rocks. 

Thus it appears that a wind-made truncating escarpment rising above an alluvial apron, although conceivable, depends on an improbable combination of 

climatic sequences and local direction of wind, and 

. that a stream-made escarpment that faces a wide valley may truncate structure but not sculpture. An 

escarpment that truncates both sculpture and structure and that overlooks a wide alluvial valley floor 

may therefore be assumed to have originated by 

faulting. 

The Wasatch escarpment is characterized by topographic youth. The fault that has produced it is an 

active fault, and the fault's activity is vigorous. 

With every recurrent slip on the fault plane the facets 

of the escarpment are freshly extended at the base, 

and each slip gives fresh stimulus to the sculpturing 

streams of the range. The youth and strength of the 

escarpment give it special distinction as the representativ.e of a type, but it represents a high development o~ the type rather than the average development. If the activity of the Wasatch fault should 

cease the processes of erosion would gradually mutilate 

and eventually obliterate the characteristic features of 

the escarpment . 

The sequence of changes by which a fault scarp 

passes from youth to senility has received some attention from Davis/o and his discussion might be amplified by taking account of the control of this sequence 

by base-level and climate, but in the present connection 

it will suffice to point out certain general tendencies. 

The mountain streams, stimulated no longer by progressive uplift, lose power to corrade downward near 

the mouths of their canyons, and their energy is 

diverted to the wjdening of the canyon floors. The 

intercanyon ridges, or ribs, of the range are thus 

narrowed near their ends, and the terminal parts are 

70 Davis, W. M., An excursion to the plateau province of Utah and Arizona: 

HarvBro. CoIl. Mus. Compo Zoology Bull., vol. 42, pp. 151-152, 1903; Nomenclature 

of surface form:; on faulted structure: Geol. Soc. Atl1eflc~ ll~l.\ vQl. 241 r>p. 198-204, 

1913. 
WASATCH RANGE, UTAH 69 

at last wholly removed. As the grades of the canyon 

floors are continuous with those of. the alluvial plain 

outside the fault, the change may be otherwise expressed by saying that the piedmont plain invades the 

range, extending tongues up the canyon and gradually 

consuming the ribs. In this process the larger streams 

work more rapidly than the smaller, the narrower ribs 

lose their terminal facets sooner than the wider, and 

the weaker rocks yield more readily tha~ the strongerwith the result that the alinement of rib ends is 

destroyed. The line of the rock base, which was 

originally simple in form and independent of structure 

and sculpture, is now complex in form, and its complexity is a function of the distribution of strong and 

weak rocks, dependent on structure, and of the drainage systenl that conditioned sculpture. The escarpment, if it still deserves the title, no longer indicates the 

position of the fault, and the fault-block mountain is 

no longer distinguished by details of sculpture from 

mountains of other origin. If the 14te of the fault is 

still traceable its recognition depends on other characters. 

The piedmont scarps of the Wasatch Range resemble landslide scarps in that they mark dislocations of 

unconsolidated fonnations. They are distinguished 

by their greater length and their simpler inflections 

and by the fact that they run parallel to the rock 

base. Landslide scarps are comparatively irregular, 

with a tendency toward lunate outlines. The simplicity of the outlines of the piedmont scarps is ascribed 

to the smoothness of the fault surfaces on which the 

slumping took place, and the irregularity of many 

landslide scarps is ascribed to the unevenness of the 

associated rock surfaces. In some localities the 

relations of the Wasatch piedmont scarps to other 

features demonstrate that they were caused by recent 

movements on the frontal fault. In some localities, 

also, they are associated with hummocky corrugations, 

such as are caused by strong earthquake shocks, and 

it is inferred that the corrugations are secondary products of the same fault movements. It is possible 

that a piedmont scarp might be caused by the passage 

of earthquake waves from a distant focus, but such a 

cause is in most places improbable because waves that 

, arrive from a distance are weaker than waves of local 

origin, and waves of local origin imply a local fault 

movement competent for the direct production of the 

scarp. It is, however, conceivable that the alluvium 

resting against the smooth footwall of a range-margin 

fault that has been inactive for a long period might be 

caused to slump by a passing earthquake, which 

would thereby create a piedmont scarp with characteristic form; and any such piedmont scarp, although 

it resulted from no recent movement on the local fault, 

would nevertheless depend for its existence on the 

presence of that fault. Therefore, wherever a piedmont scarp is found, the presence of a fault may be 

inferred with confidence. 
CHAPTER III. FISH SPRINGS AND I-IOUSE RANGES, UTAH 

GENERAL FEATUR'ES 

The Fish Springs and House Ranges stand 80 miles 

west of the south end of the Wasatch Range. Other 

ranges intervene, and a geographic order of treatment 

would give thenl prior attention, but it happens that 

of them I have but a passing knowledge, whereas the 

remoter ranges have received some weeks of study, 

and for present purposes the preferable order gives 

first place to the better known. In 1872, while traveling with topographic parties of the Wheeler Survey, 

I twice touched the ranges and was able to give about 

three days to their examination. The information 

thus gained 1 was supplemented in the winter of 

1879-80 by a few observations made during the 

A w. 

brian stratigraphy and faunas In the vicinity of 

Antelope and Marjum Passes. 

What is now called the Fish Springs Range was 

earlier mapped and described as part of the House 

Range. Either usage is defensible, for the two ridges, 

although separated by a pass and not standing absolutely in line, are bounded on the east and west by 

intermont plains that serve to differentiate them from 

other mountain ridges. Structurally they present a 

notable contrast in that the Fish Springs Range, which 

is composed of westward-dipping strata, presents a 

steep scarp toward the east, whereas the House Range, 

which is built of eastward-dipping strata, is steeply 

scarped on the west. Figure 45, which illustrates 

sorne of these features, is copied, with 

. E. change of title, from the report of 

~~~~~~~~~~~sp~,..~=== nly reconnaissance of 1872.5 

w. B E. 

c 

w. 

..... ~lEb~."." ... ,:, 

D 

FISH SPRINGS RANGE 

The Fish Springs Range is nearly 

20 miles long and from 3 to 4 miles 

wide, as shown in Plate 31. Its trend 

is with the meridian and is nearly 

straight but has a slight westward 

convexity. The higher parts of its 

db ~ ~~e:!~~~t::; ~:: 2'~~e t~~i~~O :~:! borders it on the east is broad and 

fiat and merges northward with the 

saline plain of the Great Salt Lake 

Desert. On the west and southwest 

FIGURE 45.-The broad structural features of the Fish Springs and House Ranges, Utah. A, B, C, Sectio.ns 

of the House Range at Fish Springs, 2 miles south of Fish Springs, and at Dome Canyon; scale 1:98,000; base 

line level of Great Salt Lake. D, Section of House Range as seen from the west: a, Fish Springs; b, Dry 

Pass; c, Dome Canyon and Antelope Spring; d, Notch Mountain; l, Silurian limestone; q, Silurian quartzite 

mapping of shore lines of Lake Bonneville,2 and in 

1901 the ranges were the subject of systematic study 

for eight weeks. In 1901 I was accompanied by 

Mr. W. D. Johnson, who covered the field of geologic 

work with a topographic survey. Unfortunately his 

map was never completed, I the field notes being 

destroyed by fire, but before that accident he had 

compiled a draft representing the middle portion of 

the House Range, and that has been published by 

Walcott. The Fish Springs quadrangle has since been 

Inapped by the United States Geological Survey. 

The House Range was visited in 1904 by Davis,3 

who devoted a week to its study, with special attention 

to physiographic features, and in the following year 

by Walcott,4 who made an elaborate study of CamI Gilbert, G. K., U. S. Geog. and Geol. Surveys W. 100th Mer. Rept., vol. 3, 

pp. 27-28, 167, 1876. 

2 Gilbert, G. K., U. S. Geol. Survey Mon. 1, p. 353, 1890. 

S Davis, W. M., Harvard ColI. Mus. Compo Zoology BulL, vol. 49, pp. 34-56, 1905. 

4 Walcott, C. D., Cambrian sections of the Cordilleran area: Smithsonian Misc· 

ColI., vol. 53, pp. 168, 173-185, 1908. 

70 

the range is separated from a range of hills by a narrower valley which drains both northward and SOllthward. The lake plain of the desert wraps about its 

north end, concealing all but a nar:r:ow Qelt of its alluvial piedmont. 

The eastern face is the steeper and is at most p0ints· 

strikingly bold. Because of its boldness it was early 

ascribed to faulting, and the diagnosis has since been 

verified by the discovery of a piedmont scarp and by 

the recognition of truncation. The outline of the rock 

base is by no means simple,· but there is reason to 

believe that its principal bendings follow the courses of 

faults. From the north end of the range to a point 

beyond Cane Spring (see fig. 46) the course of the rock 

base is direct, except in one place, and through the 

greater part of this distance the base is paralleled 

by a piedmont scarp. The exceptional place is just 

south of Fish Springs, where a broad salient projects 

a Gilbert, G. K., U. S. Geog. and Geol. Surveys W. 100th Mer. Rept., vol. 3, p. 27, 

1876. 
FISH SPRINGS AND HOUSE RANGES, UTAH 71 

eastward. The base of the salient is followed by 

the piedmont scarp for more than half its circuit. 

The principal body of strata in the salient dips 

gently toward the north and is separated by a 

fault fr01n a greater body at the west in which the dip 

is strongly westward, but I am not able to say whether 

the entire block is coextensive with the salient. 

Where I crossed the fault (e, fig. 46) its position is 

represented by a shear zone, and the downthrow is to 

the west. The attitude of the fault plane was not 

determined. On the whole it is probable that the fault 

belongs wholly to an older period of diastrophism, and 

that there has been no separate movement of the 

salient block in connection with the uplift of the range. 

South of Cane Spring is a broad compound salient, 

the principal points of which are both topographically 

and structurally distinct. Each of the parts indicated 

by Figure 46 is separated from its neighbors by such 

stratigraphic discontinuity as to demonstrate the existence of faults, although the faults themselves were 

seen at a few points only and were not traced out. 

The indicated east-west faults could be placed SOlllewhat definitely because they coincide approximately 

with lines of drainage, but they are by no means the 

only faults of the tract. In the study of the stratigraphy many other breaks were found, and shear zones 

were seen at several points. The fault that falls in 

line with the frontal escarpment farther north is of 

greater throw than the east-west faults and is evidently 

a master fault of the system. At the point where I 

crossed it (a, fig. 46) the displacement is about 4,000 

feet, with downthrow to the east, and its plane dips 

eastward at an angle that approaches 45°. Its course 

is readily traceable because marked by a distinct sulcus 

which falls and rises in crossing lines of eastward 

drainage. As shown on Plate 31 it is overlooked on the 

west by a fairly continuous escarpment, which is continuous with the frontal escarpment of the range farther 

north. At a (fig. 46) it is characterized by a wide 

shear zone, which is specially remarkable because uncelnented. That part of the fault has not been within 

the subterranean zone of cementation since the occurrence of a large part of the fault movement; and this 

fact accords with the preservation of the footwall 

escarpment in indicating recency. On the other hand 

the shear zone includes at that point a large block of 

sandstone, a rock not now represented in adjacent 

parts of either wall. The probable stratigraphic position of the block is in the fonnation next above the 

adj acent fonnation of the hanging wall, and I infer 

that the hanging wall has been somewhat degraded 

since its detachment. 

A still greater fault runs from d to e. (See fig. 46.) 

The block east of it shows only fornlations high in the 

Silurian, whereas the western block or blocks contain 

lilnestones near the base of the Cambrian rocks of 

the range. The estimated throw is 5,000 to 6,000 feet. 

The outer edge of the eastern block carries a small ridge 

that tapers southward, and a broad, low saddle separates this ridge from the high fronts of the western 

blocks. Those fronts fall in line as a discontinuous 

escarpment, the breaks being occupied by lines of eastward drainage. The same eastward drainage interrupts both the saddle and the eastern ridge. 

At no point were two piedmont scarps seen on the 

same slope. The highest scarps seen, between Cane 

Spring and the Fish Springs salient, were estimated 

at 6 to 8 feet. At the apex of the salient the height 

is 1 foot; and in the northern division, between Fish 

Springs and Big Spring, the height is little greatel'. 

In a tract south of the Fish Springs salient the scarp 

appears only in the spaces between alluvial fans, 

having apparently been obliterated on the fans by fresh ,Ifot Sprz:ngs 

alluvial deposits. Here, as --..... -)~ .. , ... ~, .... ,.~ BigSpring 

elsewhere, the scarp interrupts "'1 

a slope that had been exposed 

to efficient waves of Lake ~ ~ FishSprings 

Bonneville, so that its preservation proves a post-Bonne- Ul 

ville origin. ::u 

1) 

At b (fig. 46) the piedmont z 

scarp that for miles has fol- Gl 

lowed the mountain base south- Ul b 

ward is deflected and instead 

of continuing toward c takes ;0 

a direction toward d-e, the ~ 

escarpment of the salient. It (j) c {'I 

then ceases to be traceable, 

but its turning helps to connect 

I 

, 

I 

, 

I -,: '~ ,~ 

I 

I 

the fault d-e with the marginal 

fault of the range. The marginal fault north of b appar- s~(\o '~&Ss 

., Cane Spring 

ently represents the confluence 0,-, --'---'----'----'--~~M'LE.s 

of faults b-e and b-e; and the FIGURE 46.-Fault system or the 

group of fault blocks between eastern base oCthe Fish Springs 

Rang(l, Utah those two lines are related to 

the body of the range in somewhat the same way as 

the blocks that constitute spurs of the Wasatch Range 

are related to the body of that range. There is, however" a noteworthy difference. The spurs of the 

Wasatch are distinctly outside the frontal fault and 

are masses plucked from the valley block as it descended, but the compound unit between the two 

great faults of the Cane Spring salient is better 

described as intermediate between the mountain block 

and the valley block, belonging to neither but coordinate, except in size, with both. 

N ear Fish Springs is a compound landslide, a feature 

of magnitude compared with the piedmont scarp and 

so different in configuration that the two can not be 

confused. The landslide also is of post-Bonneville 

origin, for the plane of its slipping is in a Lake Bonneville deposit, and its mass is composed of a Lake 
72 STUDIES OF BASIN-RANGE STRUCTURE 

Bonneville shore formation. It is possibly an exact 

contemporary of the piedmont scarp. 

No thoroughly satisfactory record was found of the 

dip of the frontal fault. The escarpment has no rock, 

sufficiently durable to preserve a tract of foo~wall with 

slickensides. Opposite Cane Spring, at a height of 

150 feet above the rock base, a fragment of a shear 

zone was seen, and the average slope from that to 

the rock base and piedmont scarp was measured. As 

there is much evidence of step faulting in some parts 

of the face, I was not sure that the sheared rock belongs 

to the main frontal fault. If it does, the local dip 

of the fault is 45°; otherwise the dip is steeper The 

general slope of the escarpment' at points where its 

rocks are fairly resistant is 30° to 35° and may be 

ascribed to gravitational grading. It is safe to say 

that the general dip of the fault plane is not less steep. 

The truncation of sculpture is less striking than on 

some parts of the Wasatch escarpment but is comparable with the face north of Pleasant View (pI. 9, A) 

and with the upper face of the Timpanogos front 

(pI. 30, A). The limestone of the stronger beds is 

5. Cane Spring salient 

the combination of these irregularities with the dips 

of strata that the upward and downward flexures in 

the diagram are produced, and not by anticlines and 

synclines of the mountain structure. 

The springs of the Fish Springs group are thermal. 

Their temperatures were noted December 15, 1879, as 

follows: 

Spring walled in for house use at the old stage station, 78° F. 

Associated springs, 74°-77°. First spring south with large basin, 

74°. Three springs, three-quarters of a mile south of station, 

84.5°, 84.5°, 83°. Two springs with a common pond, 1.5 miles 

south of station, 80.2°, 81°. 

The highest temperature, 84.5°, is 32° above the 

mean aruiual temperature at Salt Lake City. As no 

igneous rocks are associated with the range it is probable that the water comes in part from a deep source, 

but the points of issue are more than 1 mile from the 

frontal fault. ' 

North of the end of the range hot springs rise on the 

plain within a mile of the rock base. I transcribe my 

notes, written December 17, 187.9. The springs were 

approached from the east. 

Fish $prings salient 

:"-J. 

o 1 2 3 4 8' MILE S ~, L'L'L'L' __ -L' __ -L' __ ~' ______________ -J' 

FIGURE 47.-Diagram illustrating :;runcation of structure by the eastern escarpment of' the Fish Springs Range, Utah. Horizontal Urie shows 

rock base. Vertical lines show faults. Curve shows position and distance of summit of Cambrian above or below the formation at the 

rock base. Vertical and horizontal scales the same 

a less durable rock than those that preserve the remarkable facets of the Wasatch; the ~tronger limestones are interlarded with sectilelimestones and shales; 

and the relatively slow rate of uplift, revealed by the 

scant piedmont scarps, gives time for much weathering. 

The truncation of structure is comparable with that 

shown in the Wasatch Range but is not equally illustrated by available photographic views. One who 

follows the rock base for a few miles finds his geologic 

horizon gradually rising or falling' as the dip carries 

one formation after another below or above the base 

line, and here and there, as he passes a fault, the 

sequence is abruptly broken. The changes are expressed diagrammatically by Figure 47, in which the 

changing stratigraphic interval between the bed at 

the rock base and a reference horizon is plotted as a 

curve. The reference horizon is the top' of the Cambrian. The stratigraphic range of rocks that occur at 

the eastern rock base is about 7,000 feet and includes 

nearly all the formations recognized in the mountain. 

Although the line thus plotted involves elements of 

deformation, it is not a profile of deformati<;m. The 

line of the rock base in relation to which the Cambrian 

horizon is plotted is not straight iri nature but has a 

vertical range of about 1,000 feet and a still greater 

horizontal range, as illustrated by Figure 47. It is by 

The first has a temperature of 104.5° F. It has built a mound 

probably 12 feet high. The basin at the top is 12 feet across. 

Within it are stalagmites, built from the bottom nearly to the 

surface. Most of the deposit is yellow with iron, but some is 

white. I taste salt in the water. 

The next has a lower mound, flat-topped and lying at the base 

of the first. Its pool is 8 feet across and lined with green; 136.5°. 

Bubbles rise continually. Deposit soft at surface, red. 

The third has a mound higher and broader than the first. 

Too miry to approach. 

The fourth has a mound 20 feet high and with a base of an 

acre; 139°. Basin 20 feet across; green lining; red or orange 

deposit. On the flank of the fourth is a smaH spring, nearly 

extinct. 

The fifth has a temperature of 99°. Basin 6 feet. Outflow 

small. 

The sixth is 4 rods southeast of the fifth and a little lower. 

Pool 18 feet, green-lined; 137°. 

There are two more. One I could not approach. It has a 

small basin, but a large mound. The other has no mound and 

receives water from the sixth. ' 

The group have common character!?; all are brackish. All 

have red to orange deposits where the water is hot and white 

where it is cool. The orange deposit is largely on Confervae, 

which grow in all the springs. The white deposits (salt and 

calcium carbonate?) form partly on Salicornia and salt grass 

and partly in fungoid forms. Gas rises in several springs, but 

I did not detect its odor. 

I was told in 1901 that a spring of this group, then 

used for bathing, was at times unbearably hot and at 

other times cool. These facts indicate that water 
30' 

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 31 

o 2 I H H 8 

~ 

10 

BM X4390 

I 

Cf) 

Conlour interva I 500 feet 

TOPOGRAPHIC MAP OF FISH SPRINGS AND HOUSE RANGES, UTAH 

--'1 

'% 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 32 

A. WEST FRONT OF THE RANGE, NORTH OF THE FISH SPRINGS MINES 

B. FAULT CLIFF AND SHEAR ZONE ON THE WEST FRONT OF THE RANGE,5 MILES SOUTH OF THE F ISH 

SPRINGS MINES 

VIEWS IN,FISH SPRINGS RANGE, UTAH 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 33 

. 1. WEST FRONT OF HOUSE nANGE, UTAH, I'ROM A SUMMIT AT THE SOUT H 

The prominent point is Tatow Knob. Fish Springs Range in I he distance 

13. GENERAL VIEW LOOKING ORTH 

Photograph by John P. Buwalda 

C. VIEW NOH MAL TO TIlE FACE, SHOWI G VERTICAL 

STRIAE AND TEXTURE OF FAULT ROCK 

B, C. SLICKENSIDES ASSOCIATED WITH FAULT SCARPS IN PLUM RIDGE, NEAR ALGOMA, OREG. 

The exposure is in a road cut, about Hi miles south of Algoma and 100 feet above the base of the scarp. The material bearing tbe polish is 

crushed rock, without cement and very friable. A thin layer of this veneers the footwall of tbe fault, which consists of basalt. The hanging 

wall, so far as visible, consists of basaltic talus. Dip of fault plane 49° 
FISH SPRINGS AND HOUSE RANGES, UTAH 73 

rising from a deep source, with a temperature higher 

than 139° F., mingles near the surface with water 

circulating in saliferous deposists of the lake plain. 

Taken in connection with the absence of volcanic 

rocks they indicate a deep fault; and the position of 

the springs suggests an east-west fault that limits the 

range at the end just as it is limited by another fault 

at the side. The suggestion finds support in the fact 

that in the north end of the range the strata dip toward 

the north instead of in the prevailing westerly direction. 

It is worthy of note, in this connection, that four other 

ranges-the Dugway, Simpson, Stansbury, and 

Oquirrh-somewhat similarly related to the Great 

Salt Lake plain, are also characterized by northerly 

dips at their northern ends. In the Oquirrh Range 

the northerly dip is steep and is strongly contrasted 

with the dips in the adjoining part of the mountains. 

'rhe rocks of the Fish Springs Range are sedimentary, and their dominant dip is westward, at angles 

that probably average 30° or 35°. The early characterization of the range as essentially a faulted monocline might with present fuller knowledge be repeated 

as a generalization. The internal structure, however, 

is by no means simple, and the generalization as to 

external structure admits of qualification. 

The western face, although in detail quite as complicated as the eastern, received less attention in the 

field and can not be described in a comprehensive 

way. In preparing the following account of special 

features I have found much occasion to regret the 

incompleteness of my examination. 

About 2 miles from the north end the face is bold 

and high, as shown in Plate 32, A, and there is probably a fault with downthrow to the west, between the 

cliff and a rocky foothill at the left in the view. The 

dip in the foothill is westward. The stratigraphic 

position of the foothill rock was not learned, and for 

that reason the demonstration of faulting is for the 

particular locality incomplete. Farther south, however, and for several miles the front presents a similarly bold face, overlooking similar foothills, where 

certain beds were correlated with beds that occur high 

in the cliff. The throw was roughly estimated at 

1,000 to 2,000 feet. 

South of this point and farther west rises a second 

scarp which contains fault features of a different type. 

The scarp bounds a rock-cut piedmont plain or peneplain, in which the general dip of strata is westerly. 

At the scarp the strata end against a wide and complicated shear zone, in which are included large blocks 

of similar strata. 

Planes of shearing have dips that range from 50° 

to 70°, and a sheet of limestone so broad that its attitude is presumably that of the footwall of the fault 

dips westward at 50°. With a height of several hundred feet the scarp trends east of south for half a mile 

62436-28--6 

or more, and the base gradually rises. Its trend then 

changes to southeast and afterward to south. In the 

southeasterly portion the scarp base continues to as .. 

cend the piedmont slope,. but the height of the scarp 

diminishes. Beyond the turn toward the south the 

base becomes level and coincides with the Bonneville 

shore line. At the same place the material of the scarp 

surface changes from sheared rock and bedrock to 

alluvium. Where the scarp is highest it marks the 

lower edge of a rock-cut piedmont plain, and this relation continues to the southward turn. Beyond that 

turn the piedmont plain has two parts-the upper 

cut in rock, the lower alluvial-and the surface grade 

passes from one to the other with interruption. The 

shear zone for a space marks the limit between rock 

and alluvium and then disappears in post-Bonneville 

arroyos that cross the piedmont slope. As I interpret 

them these features were thus developed: Long after 

the beginning of range growth a fault occurred with 

throw to the west. The fault was marginal and created a westward-facing escarpment, against which 

was gathered detritus from the rising block. Afterward, in a long period of diastrophic rest the escarpment retreated by erosion, with the development of 

a piedmont slope that was partly carved from rock 

and partly built up by alluvial deposition. There 

has been no later faulting on this plane, but the existing scarp has been created by erosion, the chief or 

only agent of erosion being the Bonneville waves, 

which have cleared away the alluvium and thus 

exhumed the ancient fault scarp. 

Near the middle of the western face lies a tract 

several miles long in which the range rises rather 

steeply from a well-graded and somewhat definitely 

limited piedmont slope. The appearance of the pied~ 

mont as seen from a peak led me to suspect that it 

was a graded rock slope with a veneer of alluvium, 

but the suspicion was not confirmed by an inspection 

of one of the arroyos of the slope. 

Farther south the head of the piedmont slope lies 

farther from the axis of the range, and the lower parts 

of the intercanyon ribs have a certain regularity of 

crest height that suggested the· former existence of a 

rock-cut piedmont plain, about 300 feet above the 

grades of present canyons. The ends of the same ribs 

show an alinement that is partly independent of the 

internal structure and thus suggest the existence of a 

fault scarp. The evidence is· vague and incomplete, 

but so far as it goes it indicates that a minor faultbounded block, after resting so long as to have become 

graded to the piedmont slope, had been lifted a few 

hundred feet, with resulting dissection. The fragments of tectonic history gathered along the western 

front and base serve to qualify the simple conception 

of the range as a tilted fault block by showing that the 

process of its growth has included minor faulting on 
, 

74 STUDIES OF BASIN-RANGE STRUCTURE 

the side toward which the block inclines. At least a 

part of the range, like a part of the Wasatch, might 

properly be characterized as an unsymmetric horst. 

The formations that constitute the range are Paleozoic and so far as known are conformable. More than 

half the section is Cambrian; the highest member is 

possibly Devonian, but its age was not learned. The 

section was studied only as a means of investigating 

the structure. Special attention was given to peculiarities of formations by means of which they could 

be recognized without close inspection, and paleontologic correlation was 'not attempted. 

The following tabular statement shows the general 

seqiIence of formations and gives rough estimates of 

thickness; its notation will serve to correlate the 

menlbers represented in structure sections. 

Stratigraphic column of the Fish Springs Range 

Symbol Roek Period 

L ' Limestone __________ '_ __ _ __ (?) 

K _____ do___________________ (?) J _____ do _____ .__ _ __ _ _ _ _ _ _ _ _ _ Silurian _____ _ I Sandstone ______________________ do ______ _ 

,H Limestone and sliale________ (?) 

G Massive limestolle __ .,.':' _ _ _ _ __ Cambrian (?)_ F Limestone and shale:.. ____________ do ______ _ . E Limestone _____________ :.. _______ do ____ :.. __ D _____ do ________________________ do ______ _ 

C Shale, with limestone ____________ do ______ _ B Shale, with sandstone ____ ..: ______ do ______ _ A Sandstone, with conglomer- _____ do ______ _ 

ate. 

'l'biekness 

Feet 

600 

600 

1,000 

100 

1,000 

1,000 

300 

200 

1, ,200 

800 

500 

200 

7,500 

, With minor exceptions the beds dip toward the 

. west, and with some exceptions the angle of westerly 

dip falls between 20° and "40°. At the extreme north 

the dips are: northerly, and less steep. In the Fish 

Springs salient is a block that is nearly level but is 

thought to dip northward. The only recognized fold 

is a local syncline west of the axis and within a few 

miles of the'north end. . In the main body of the range 

there is',' a- general slow. descent of the formations 

toward the '~orth, so that younger members predominate in northern districts and older in southern. 

The'range contains a number of strike faults. At 

3 miles from the north end the position of a notable 

cross fault is marked by a pass. The throw of this 

cross fault i~ not the same in all parts, but the average 

throw is perh!).ps 2,000 feet and on the north side. 

Farther south occurs a cross fault that has a northward throw of about 5.00 feet. 

The range is fairly riddled by minor faults. There 

are surely hundreds of them and probably thousands. 

They ,have many directions, but the strike faults 

appear to be most numerous. Some are seen in cliff 

faces as simple lines of division; others are marked by 

shear zones. They served to confuse every stratigraphic section of more than 100 feet that I attempted 

to measure, and my field notes characterize them as 

"disconcerting" and" exasperating." They are partly 

responsible for the fact that the thickness of the 

formation is indicated in the table only in round 

numbers. 

In the axial region and along the eastern face the 

great majority of minor strike faults are normal and 

cut the bedding approximately at right angles. On 

the western face they are more nearly vertical. In 

both regions they cause both duplication and widening of outcrops. 

Some of the faults belong to the lllovements that 

created the range. They may be styled "later," to 

distinguish them from faults" earlier" than the beginning of the present range. The fault of the eastmTI 

escarpment and all the faults of the Cane Spring salient may be classed with little question as later, and 

so, too, may those normal faults of the western face 

that are associated with the uplift of the axial horst. 

To the earlier class may be assigned with some confidence a fault that crosses the Fish Springs salient 

and a strike fault farther north. These faults are 

out of harmony with their neighbors on both sides 

and have a throw to the west. The strike fault contains a quartzose or quartzitic sheet which weathers 

into prominence and marks its course for some distance • 

The minor faults are thought to belong largely to the 

later class, because they are similar in dip and In 

direction of throw to the greater marginal faults .. 

HOUSE RANGE 

The House Range is about 40 miles long and is fronl 

5 to 10 miles wide. Its axis, which has a general 

trend a little west of south, is slightly concave toward 

the west. The west face is an escarpment that rises 

3,000 to 4,000 feet from the rock base. The eastward 

slope descends to a base of irregular outline and is 

diversified by acute dissection. The rocks are almost 

wholly sedimentary, and their general dip is eastward 

at low angles. The attitude of the strata and the 

character of the westward-facing escarpment are 

illustrated by the foreground of Plate 33, A. The 

Fish Springs Range, with its westward-dipping rocks 

and steeper east face, appears in the distance in that 

view. Between are hills and table-lands less readily 

characterized and in some sense intermediate In 

structure. 

The principal divisions of the range, nanled in 

order from north to south, are the Tatow Plateau, 

Antelope Mountain, Howell Peak, and Notch Peak. 

The plateau character of the Tatow upland is nlost 

marked at the south, where a broad tabular surface is 

determined by a resistant limestone. The surface 

has ap. average slope eastward of about 6° but undulates gently and is also modified by a few faults of 

moderate throw. Above the plateau project a few 

knobs, remnants of a higher bed of limestone, and 
FISH SPRINGS AND HOUSE RANGES, UTAH 75 

below it are carved steep-walled canyons that drain 

eastward. Northward the upland loses height gradually and its structure changes, becoming less simple. , 

Toward its north end it is separated by a wide hollow 

into two ridges, of which the western is the narrower 

and steeper. The western ridge is composed of sandstone including the lowest locallnember of the Cambrian systCln, and the eastern is capped by Cambrian 

linlestones, the stratigraphic position of which is several thousand feet higher. The formations have been 

brought to nearly the same level by a system of faults 

with downthrow toward the east. Some of the faults 

strike with the nleridian, and others strike more 

nearly northwest. There is also a northward descent 

of the strata, partly through dips and partly through 

faulting, so that the formation which constitutes 

Tatow Knob (see pI. 33, A) at an altitude of 8,400 

feet occurs also at 6,000 feet 5 nliles farther north and 

in the northern part of the east ridge has reached a 

level 1110re than 1,000 feet below the surface. 

The structure of the north end of the House Range 

l'csc,mbles that of the south end of the Fish Springs 

Range in that the dislocations have lifted the western 

blocks in relation to the eastern, but the resemblance 

goes no farther. The faults of the Fish Springs Range 

are associated with westward dips, those of the Tatow 

Plateau with 'eastward dips. The internal faults of 

the Fish Springs Range are harmonious with the great 

III arginal fault, along which the range was lifted; 

those of the Tatow Plateau are not of the type that 

1llight create the westward-facing escarpment. The 

1l1mOr blocks along the Tatow escarpment, instead of 

being dropped below their neighbors in the range, like 

the blocks of the Wasatch frontal sp'urs, stand higher 

thl1n their neighbors in the range. If the western 

escarpment of the House Range is a fault scarp-and 

there is independent evidence that it has that character-then the nlinor blocks along the face of the 

cTatow Plateau are not products of the diastrophism 

that created the range but are of independent origin. 

Presumably they belong to an earlier diastrophism. 

The Sand Pass Ridge is in some sense a connecting 

link between the Fish Springs and House Ranges but is 

more closely related to the House Range. For the 

greater part of its length it parallels the west face of 

Tatow Ridge at a distance of a mile, but the interval 

is bridged by rocky spurs. There is no pronounced 

general dip in the rocks of the ridge, and 11l0st of the 

dips observed in it are gentle. It is divided by numeFous minor faults. So far as noted the throw of the 

east-west faults is toward the north and that of the 

north-south faults to the east. In the principal spur 

that joins it to Tatow Ridge north-south faults of 

noteworthy displacenlent occur, and all these' throw 

toward the east. They constitute a step-fault systell1 

by which the Sand Pass Ridge block has been lifted 

high above the Tatow Ridge block. Because of 

northward dip in the Tatow it is probable that the 

dislocation is greater at the north than at' the south. 

Its amount was not measured but is probably not 

less than 5,000 feet and may be as great as 7,000 

feet. 

As shown by the map (pI. 31), the valley along the 

eastern base of the ridge is drained mamly northward ~ 

and southward, but a middle part drains westward, 

its outlet dividing the'ridge by a canyon. A line of 

drainage that heads in the western face of Tatow 

Ridge crosses without deflection the hollow eroded in 

weak rocks and continues its course across a ridge of 

stronger rock. 

, . 
CHAPTER IV. KLAMATH"LAKE REGION, OREGON 

GENERAL FEATURES 

For the profit and pleasure of a visit to the region 

of the Klamath Lakes, in Oregon, I am indebted 

primarily to Prof. D. W . Johnson and Mr . John P. 

Buwalda. Professor Johnson, while passing through 

the region by automobile and railway trains, noted 

that the basin of Upper Klamath Lake is probably a 

graben, that the fault scarps bounding the basin on 

the east are peculiarly fine illustrations of their type, 

and that one of them affords a remarkable exhibition 

of slickensides. These observations he communicated 

to me, and they excited an interest which led me to 

plan a visit. The visit was made in September, 1916, 

and its fruitfulness was greatly promoted by the 

cooperation of Mr. Buwalda, who was my companion. 

The observations here recorded were a joint work, and 

E. 

FIGURE 48.-Diagrammatic profile and section across the Plum Ridge 

fault scarp, Klamath County, Oreg. The broken line indicates 

the portion of the uplifted block which has fallen away since the 

beginning of the dislocation and has furnished the material of the 

talus 

as many of the inferences here presented were developed 

by discussion in the field they also are a joint product. 

But as some of the inferences were afterthoughts, and 

as the afterthoughts and the writing have been mine, 

I can not avoid responsibility for such errors as may 

have been entertained. 

Upper Klamath Lake (pI. 34) is a sprawling body 

of water with an extreme length, north and south, of 

25 miles. It is bordered by marshes almost as extensive as the lake itself, and the marshes are bordered 

by plains of gentle slope. These flat elements of the 

landscape are in strong contrast with the mountains 

and the hills that- adjoin them on the west and east. 

On the west the Cascade Mountains present a bold 

and rather lofty front, and on the east are three 

cliffs, less lofty but bolder, which overlap in such way 

that each for a distance walls in the tract of plain and 

lake. The northernmost cliff, which may be called 

the Fort Klamath escarpment, has a general course 

76 

that trends a little west of north and is 16 miles long. 

From Klamath Indian Agency to Fort Klamath its 

general height is 400 to 600 feet, and this height continues for 4 miles farther. Then it rises in a short 

distance to a height twice as great and holds this till 

its identity is lost on the southward slope from the 

rim of Crater Lake. The north end of the Modoc 

escarpment stands 5 miles east of the disappearing 

south end of the Fort Klamath escarpment. Its 

course is southward for 12 miles to Modoc Point and 

then south--southeastward for 18 miles to a sudden 

ending in the plain traversed by Lost River. Its 

general height is 600 to 1,200 feet. The Plum Ridge 

escarpment is parallel to the southern division of the 

Modoc escarpment and stands 2 miles farther west. 

It is 8 miles long, and its general height is 1,000 feet. 

It is on this escarpment that the slickensided surfaces 

are displayed. 

PLUM RIDGE AND VICINITY 

At its north end the base of the Plum Ridge scarp 

approaches Upper Klamath Lake, from which it is 

separated only by a narrow alluvial apron. A carriage road formerly traversed this apron, but a railway has recently displaced it, and now the carriage 

road is accommodated on the-steep scarp by means of a 

sidehill cut. The fresh excavations for railway and 

roadway have revealed a fault plane-the plane of the 

fault which' created the· scarp. The general profile 

and section of the scarp are shown in Figure 48. ·Its 

slope is 34° except at the very base, where it passes 

into that of the apron. The fault plane meets this 

slope as drawn, its inclination being about 49°. To 

be specific, measurements at four points gave 47°, 

48°, 50°, and 52°. Above the meeting of the fault 

plane and the external profile the visible material of 

the slope is rock in place, veneered in part by sliding 

talus; below the meeting only talus is seen. The line 

of meeting, traced along the face of the scarp, is 

relatively high at the south, although nearer the base 

of the scarp than the crest, and descends northward. 

It finally reaches the apron and then passes below the 

level of the lake. In its descent it crosses the two 

lines of excavation, first that for the carriage road and 

then that for the railway, and it is at these crossings 

that slickensides are seen. 

The exposure of polished surface at the carriage 

road is 110 feet long and has a ma.ximum height of 43 

feet. Upward and on the north the surface terminates 

because the rock bearing it has been removed by 

erosion; downward and toward the south it passes 
KLAMATH LAKE REGION, OREGON 77 

behind talus. As shown in Plate 33, B, 0, it has been 

utilized for billboards. The scratches upon it show 

a slight variation in direction, and some of them intersect at small angles, but collectively they indicate that 

the relative motion of the rock masses had no horizontal component within the fault plane. The 

tI plane" is not a plane in the mathematical sense but, 

like other fault planes, is a warped surface. The more 

pronounced curvature here is that shown by contours, 

and the contours swing, within the field of this exposure, through an arc of about 10°. 

'1'he exposures near the railway track (pI. 35) occur 

iu several patehes, distributed through a space of 

several hundred feet, and they are similar to the one 

.i ust described. The striae are vertical, and the flexures of the fault surface fire of the nature of a broad 

fluting parallel to the striation. Readings of N. 58° 

\¥. and N. 22° W. indicate a local swing of the fault 

strike through an arc of 36°. The broader curves of 

the fault plane are in accord with the local curvature 

of the contours of the fault scarp, and when this fact 

is considered in connection with the way in which the 

N 

beds which have an arrangement that suggests the 

quaquaversal dip of a' cinder Cone. 

The throw of the fault can not be stated, but a 

rough estimate is possible. The quantity of material 

eroded from the raised block is definitely represented 

in section (fig. 48) by the triangle between the existing 

profile of the block and its restored profile. Much of 

that material was separated in blocks and is lodged as 

talus directly beneath its source; some of it doubtless 

traveled farther and has joined the fine sediments of 

the valley. So the section of talus may be somewhat 

less but is not greater than the section of removed 

Imaterial. The slope assumed by the talus is nowhere 

steeper than that of the rock face above but is in some 

places a little less steep. On the other hand, it can 

not be assumed that the visible slope of the talus is 

continued without modification below the level of the 

vaUey deposits (as it would be if the talus had been 

complet,ed before deposition in the valley began), for 

the growth of those deposits has probably been contemporaneous with the progress of the faulting and 

the growth of the talus. The combination of these 

s. 

p' 

f<:O~s s __ -----~-----A~ ~> t_I,OOO A------ o 2 MILES 

~, ~~--~--~--~------------~I 

P'lOURE 49.-Longitudlnal profile of northern part of Plum Ridge, Klamath County, Oreg., with profiles of lower hills adjoining on the west. 

LL',leveloflake surface. PP', Profile of Plum Ridge; AA',lnferred profile of down thrown block adjoining Plum Ridge block; BB', proflle 

of hili adjoining PlUm Ridge, crest line of lower fault block, possibly continuous with AA'; CC', profile of hill adjOining BB'; 8,8, localities 

of exposed slickensides; 88t, trace of fault plane on Plum Ridge scarp 

fault line is traced on the face of the scarp it is easy to 

understand that deviations of the fault plane from 

flatness find topographic expression in variations of 

the trend of the scarp. 

The Inaterial that bears the polish and striae is a 

soft ffiult rock, a powdery breccia of the local country 

rock, which is mainly basalt.. It is so feebly coherent 

that a block of it falls apart in the hand, and the 

slickensides will probably be effaced by the weather 

in a few decades. Its observed thickness is only a 

few inches. In a number of places it is divided by 

oblique polished surfaces, which incline' more steeply 

than the fault plane. The lines in which these oblique 

surfaces meet the fault plane, though irregular, are 

approximately horizontal. 

The dominant material in the compositio)l of Plum 

Ridge is basalt, which occurs in beds. So far as known 

basalt is everywhere the capping rock. Some intercalated sandstone was seen; and a railway ballast 

quarry at the base of the ridge, close to the north end, 

exposes tuffs and sands that have a complex structure. 

At a point 2 or 3 miles farther south the face of the 

scarp shows. a small body of highly inclined clastic 

beds. Still farther south and at midheight on the 

face of the scarp there is ~p. e~PQsure of highly :inclined 

considerations yields the compromise conclusion that 

the total height of the talus is about the same as the 

vertical distance from the outcrop of the fault plane to 

the top of the cliff, or that the last-mentioned distance 

is about half the vertical throw. As eomputed on this 

basis, the throw of the fault is nearly 2,000 feet at the 

north end of the ridge and diminishes rapidly southward. At 2 miles from the end it is about 1,200 feet. 

The inferred position of the top of the downthrown 

block is shown in Figure 49_ 

The northern part of the face, about 3 miles in 

linear extent, was seen at short range and examined 

critically. A remarkable feature is its uniformity of 

slope. The uniformity from top to bottom is illustrated by the profile~ in Plate 35, B. The uniformity from point to point is illustrated by the fact that 

measurements at five different places show a range of 

only 3°-from 330 to 36°. As the creation of the 

slope has been mainly a work of degradation, and as 

the angle of slope is approximately the angle of rest 

for angular waste, it is not difficult to infer the processes involved. Disintegration of the basalt, which 

is the dominant resistant rock, has occurred chiefly 

through cracking into blocks and chips, and transporta.tion ha,s occurred chiefly through the direct 
78 STUDIES OF BASIN-RANGE STRUCTURE 

action of gravity. As fragments have been broken 

away, because the rock was strained by rapid changes 

of surface temperature or by frost, they have rolled 

down the slope to form talus below. This action may 

have promptly followed each movement on the fault 

plane, or it may have lagged behind the development 

of the scarp, but in any event it found its limit when 

the angle of rest was reached. Thereafter the degradation of the face must depend on the slower processes of chemical disintegration and aqueous transportation; and the face is still too young to show evidence of sculpture by these processes. In the course 

of time, if movement is not renewed on the fault plane 

the scarp will come to be diversified by ravines and 

spurs, and the details of its slopes will come to express 

inequalities in the resistances offered by the underlying rocks. As compared with many high fault 

scarps of the Great Basin this one is youthful. 

The absence of dissecting ravines ,indicates, in the 

first place, that the escarpment is not crossed by 

drainage from the upper surface of the ridge. If the 

prefaulting drainage ran westward it was turned back 

by eastward tilting at, the time of the uplift. We did 

not visit the top of the ridge, and no direct evidence 

was obtained as to direction of slope, but beds of basalt 

exposed in the north face were seen to dip eastward. 

The absence of ravines indicates further that there 

is little tendency toward the concentration of drainage, 

and I infer from that fact that water descending the 

slope has little power to erode, for it is through the 

deepening of a slightly favored channel that it is able 

to divert to itself additional drainage. This line of 

thought leads again to the idea that transportation 

of waste by the direct action of gravity is still dominant 

on the face and transportation by water is still subordinate. Triangular facets, which depend on segregation of drainage, belong to a later stage of topographic development. 

No evidence was found of recent movement on the 

fault plane. If such a movement had occurred, and 

if the entire body of talus had moved down with the 

descending block, there would have been created at 

the rock base (h, fig. 48) a little cliff having the steepness of the fault plane. If such a cliff existed it would 

mark the rock base by a conspicuous line across the 

face of the escarpment; but the position of the rock 

base is not thus marked. If less than the whole body' 

of talus moved downward an earth scarp would be 

created at some lower level, and it could be preserved 

only by traversing a slope gentler than that of the 

talus. The alluvial slope below this talus was scrutinized in search ,of such an occurrence, but none W$S 

discovered. 

The ridge ends at the north hi a face which is approximately plane, although not so even as the western 

face. Its contours make a right angle with those on 

the west. Its slope is about 20°, and it is not dis-, 

sected. It is obscurely terraced, and the terracing is 

apparently connected with outcrops of eastward-dipping beds of basalt. Suggestions as to the origin of 

the face are (1) that it belongs to the prefaulting 

topography, in which case it is a product of postlava 

erosion, (2) that its inclination was given by t~lting 

during the epoch of faulting, (3) that it is a fault-scarp. 

Evidence as to the first suggestion is purely negative. 

The little that I saw of the prefaulting topography 

and the greater amount which is suggested by the 

mapped contours of a neighboring upland do not 

indicate the probable existence of an eroded valley or 

canyon of which this sloping face might be the wall. 

The second suggestion appears to be negatived by the 

, fact that ledges of basalt cross the face. Examination 

of the ledges was too cursory to warrant a definite 

statement about them, but the impression was obtained that they conform in structure with those 

exposed in neighboring parts of the western face. 

The third suggestion is countenanced by the fact that 

many features in the immediate neighborhood are 

due to faulting and is thought to be the most probable. 

If the face is in fact a fault scarp then the horizontal 

displacement involved in the faulting was about three 

times as great as the vertical, and its 'extent exceeded 

half a mile. If the downthrown block lies as far b'elow 

the lake surface as that on the west side of the ridge 

the horizontal displacement was about 1 mile. 

The central and southern parts of Plum Ridge are 

flanked on the west by a lower ridge, which is less 

regular in form. The bases of the two ridges join, or 

perhaps the relation might better be expressed by 

saying that a narrow sag, or high valley, separates 

their crests. The indication of the contours on the 

map that this valley is everywhere walled on the east 

by the' Plum Ridge scarp was borne out by such 

distant views as we obtained. The slopes of the lower 

ridge are in general less steep than those of the higher, 

its smoother curves gave less information as to its 

structure, and as it was seen ,only from the road along 

its western base, there would be small advantage in 

describing such features as attracted attention. It 

was thought to contain a number of minor fault 

blocks, and two ,of these are indicated in profile 5 of 

Figure 50. 

Plum Ridge is about 1 mile wide at the base. A 

valley 1 mile wide separates it from the'Modoc escarpment. For about'half its length this valley has a flat 

alluvial bottom, but in its north end stand two small 

ridges, and its southern part is occupied by a multitude 

of small ridges and hills. The ridges at the north are 

designated in Figure 50 by the letters a and h. 

Ridge a lies parallel to its larger neighbors and 

is perhaps a mile in length. From a middle width 

of one-third mile and a height of about 200 feet 

it tapers and slopes toward each end. On the east 

its middle part is joined to the lower slope of the 

Modoc escarpment. It is a monocline, with gentle 

eastward dip and a relatively steep face toward the 
KLAMATH LAKE REGION, OREGON 79 

west. The .north end of ridge b, which lies between 

ridge a and Plum Ridge, is also monoclinal, and 

the 'relations of the three parallel ridges, all controlled 

by bedded basalt dipping east and all presenting 

scarps to the west, are strongly indicative of faulted 

Rtructure. The relations are shown in profiles 1 

u,nd 2 of Figure 50. The noi,th end of ridge a appeu,rs at the right in Plate 36, O. 

Ridge b is 2 lniles long. Near its north end it 

is joined to Plum Ridge at the base and farther 

south it becomes a shoulder of that ridge. In its 

llliddle course it is relatively low, but toward the 

south it rises again. Its northern part, as already 

Inentioned, shows a dip' to the east, but farther 

south there appears to be no dip in the transverse 

direction, although there lllay be a longitudinal 

inclination toward the north. On the assumption 

that these attitudes of its basalt beds have resulted 

from deformation, the ridge c01nprises not less than 

two minor fault blocks. In Figure 50 profiles 1 

and 2 show features of the northern part, and profiles 

3 and 4 of the southern part. These four profiles 

are separated by subequal intervals of about half a 

mile. The interval between profiles 4 and 5 is three 

tUlles as great, and profile 5 shows new features. 

PIU1H Ridge is here higher and narrower and bears 

on its flank a ridge, c, which is i~dependent of ridge 

b. The structure of ridge c was not seen, and its 

description is based la~gely on the contours shown 

on tho lllap. It appears first at the base of Plum 

Ridge and rises southward along the flank of that 

ridge, and its crest bec01nes at last the main crest 

of Plum Ridge and stands next to the nlain fault 

scarp. So the body of Pluln Ridge probably contains 11lore than one faulted block. 

South of the middle of Plunl Ridge the entire 

interval between PIUDl Ridge and the Modoc escarp1l1ent is occupied by sIn all ridges. They are forested, and I saw thOln only fr0111 the road which 

winds and climbs alnong theln. So far as observed, 

thoir prevailing trend is parallel to that of the greater 

features, they are of moderate length, and they resemble ill general arrangement the sliced country 

or rift belt of the San Andreas fault in California. 

At one place they inclose a drainless hollow a third 

of a Inile long that has a flat alluvial floor. Their 

material appears to be basalt, but their structure 

was not made out. A continuation of the sallle group 

south of the end of Plum Ridge conta~ns hills of sandstone on which no basalt was seen. 

In general, Plum Ridge and the associated hills 

owe thou' forms chiefly to faulting. The terrane, 

which has been dislocated, had a c01llplicated structure that recorded an earlier geologic history. A 

lato event of that history was the spreading of 

basalt in broad sheets. Earlier events were the 

fOl"lnation and th~ deforrnation of clastic sedirnentary beds and the eruption of tuff and volcanic sand. 

As the basalt beds near by everywhere overlie the 

other members it is possible that the prefaulting 

surface was a lava plane, but such a condition is not 

proved by the data gathered. 

There are two major faults (the Pluln Ridge and 

Modoc), and these are parallel, as well as similar' 

in magnitude and in direction of throw. They are 

marked in the topography by similar bold, sharply 

cut scarps and are associated with the most striking 

features of the relief. Minor faults are nunlerous. 

The terrane is broken into many blocks, and these 

have many attitudes. In general the longer ;axes 

of the blocks are parallel or subparallel to the major 

faults, which strike N. 25° W. The ordinary ratio 

of longer axis to shorter is a small number. It IS 

SW. HE. 

MS 

~ 

~ / 

I 

R b MS. 

L~ ~ 7 

r----- 2 ~ 

MS 

R 

Plain ~ ,----'-.:..:~-

S 

~ 

MS 

R 

Plllin 

,------ ~ 

4 PR MS 

~----,~ 0L..I ...... '-.r...' .... ,---'-, _5POL..' O ___ I ...... O.?OO "EET 

FIGURE 50.-C1'oSS profiles of northern part of Plum Ridge and of 

associated ridges and valleys, Klamath County, Oreg. PR, Plum 

Ridge, MS, Modoc scarp; i, I, I, approximate positions of faults; 

a, b, c, smallor ridges 

probably true that many more blocks incline eastward than westward, but the evidence on this point 

is obscure. 

Many of the ridges and hills are softened in outline. 

No lllinor scarps were seen which preserve the sharp 

definition of the major scarps. This difference suggested the possibility that much of the minor faulting 

had preceded the faulting which produced the.. major 

scarps; and that view was for a time entertained. 

The explanation, however, was unsatisfactory. Because any deformation of large pattern develop~ local 

stresses which produce deformation of smaller pattern 

(for example, crumpling inside a large fold and breccia 

along a fault plane), it seems easier to explain minor 

faulting as ancillary to major faulti;n.g than as independent and antecedept. I sought, therefore, a. 

different explanation of the comparative indefiniteness of the topographic expression of minor faults and 

have the following to propose. The prefaulting surface was weathered, and its rocks were seamed and 

disjointed. When faulting began, the resulting scarps 

. . ~ .. 
80 STUDIES OF BASIN-RANGE STRUCTURE 

were not sharply cut, because the incoherent rocks 

yielded to transporting agencies. With the continuance of faulting, unweathered rocks became exposed 

in the scarps, and their resistance tended toward the 

preservation of steep slopes. Thus the greater dislocations acquired a strong expression, whereas the 

smaller did not. 

The incoherence of the crushed rock bearing the 

slickensides is a noteworthy feature, although its 

interpretation is not clear to me. The localities at 

which it was observed are on the face of the uplifted 

block ~Hl;<!'1~out 1,200 feet below its top. The places 

. wePB tiierefore 1,200 feet below the surface when the 

fau]ting began. The creation of a fissure occupied by 

crushed rock was the creation of a conduit for the 

circulation of underground water, and SOIne of the 

conditions essential to cementation were evidently 

present. The fact that no cementation took place 

shows that an essential condition was absent but does 

not specify the absent condition. 

MODOC ESCARPMENT 

As already mentioned, the strike of the Modoc 

escarpment changes abruptly at Modoc Point. In 

a 

fully good overlapping block or fault splinter (south of Modoc 

Point).! 

The "fault splinter," which his phrase aptly characterizes, is shown in Plate 36, B, and its cross profile 

and section in Figure 51. It is a narrow block fro In 

the original terrane, separated from the hanging wall 

and footwall by subdivisions of the fault fracture and 

lodged on the face of the footwall. It has been rotated 

in such a way that its top slants southward. Its cap 

rock retains an eastward dip, which gives the terrace a 

backward slope, so that the terrace constitutes an 

inclined gutter and intercepts storm waters that flow 

down the scarp. A similar slab, smaller and less 

tilted, buttresses the scarp' opposite ridge a, and its 

profile appears in the upper diagrams of Figure 50. 

Such splinters, which are known only as details of 

fault scarps, are related genetically to the intermediate 

blocks of a step-fault system and also to the" horses" 

of fissure veins. The only topographic features with 

which they are likely to be confused are landslides, 

and there are in fact instances in which the discrimination has been found difficult.2 In this locality, however, there is little room fo~' question. If the detached 

mass In Figure 51 had broken loose and slid down 

FIGURE 51.-Fault splinter 011 :Modoc scarp, ncar Naylox, Oreg. a, Cross profile; b, hypothetic section 

the space of a mile it swings through an arc of about 

40°. The southeastern division starts from Modoc 

Point with a course which, except for minor undulations, is due southeast. After curving slowly south~· 

ward for about 5 miles, it acquires a general direction 

S. 27° E., which it holds for 13 miles. In its curved 

course it borders Upper Klamath Lake, then for, 2 

miles it borders a tract of marsh land, and beyond that 

it' borders the trough which separates it from Plum 

Ridge. 

Through the entire distance it has the bold habit of 

the Plum Ridge scarp, and its average height is somewhat greater. Such excavations as have been made for 

railway .and roadway have not revealed the plane of a 

determining fault, but the existence of such a fault is 

shown by independent evidence. 

While Professor Johnson's train stood at the village 

of Algoma in 1915 he wrote in his notebook: 

From the northern end of Plum Hills one looks northward 

against the finest scarp of an undissected fault block I have 

ever seen. Scarcely a particle of dissection; smooth, steep 

~carp with ~ven-to.p.ped crest! apparently aU l~va. Wonderafter the formation of the escarpment its lower part 

would protrude, instead of conforming, as it does} to 

the normal grade of the escarpment. 

The escarpment bears also a number of thinner dislocated slabs, which I think must likewise be classed 

as fault splinters, although their characters are less 

demonstrative. They occur in the space between the 

two well-marked splinters, and their arrangement is 

shown in Plate 36, Band O. Their upper edges have 

arrested slide rock from above, and as the coarser talus 

material, where free from soil and vegetation, has a 

dark color, the positions of the edges are marked in the 

views by contact lines between dark patches above 

and paler patches below. The marking is approximate only, because in some places the vegetation that 

borders the coarse talus is also dark, but it serves to 

bring out the fact that there is a general alinement of 

the upper edges, their positions being progressively 

higher from left to right. The first and second dia .. 

1 Communicated in letter. 

2 For a discussion of certain criteria sec Lawson. A... C., in California Unlv. Pc{>t. 

Geology BllU., vol. 4, pp. 331-343, 1906. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 34 

121 0 45' 

L A 

.. 270 

VALLEY 

t 21 0 45' 

MAP OF REGION ABOUT UPPER KLAMATH LAKE, OREGON 

Contour Interval 200 feet. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 35 

A. VIEW ORMAL TO THE STRIKE OF THE FAULT 

B. OBLIQUE VIEW FROM THE SAME POINT 

The smoot.hed fooLwall , which dillS abouL 50° W ., is here vertically fluted. The nearest exposure a nd the one next beyoud are on oppo ite sides of a groove (of Lhe iluLing) from which Lhe overlying talus has not been fully cleared 

SLICKENSIDED FACES ON FOOTWALL OF PLUM RIDGE FAULT, 1 MILE SOUTH OF ALGOMA, OREG. 

The locality is at lhe base of the ridge, wruch here lrends S. 25° E. Tile exposures of Lhe planed surface have beeu made by 

excavations along a railway. PhoLographs by John P. Buwalda 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 153 PLATE 36 

11 

B 

C 

THE MODOC FAULT SCARP, EAR ALGOMA, OREG. 

The views overlap and were laken from the same point, a school yard in the village of Algoma. 'l'he scarp here faces wesl-south- west, overlooking UPl)er Klamath Lake and the bordering marshes. In A at the right is Modoc Point, a salient angle of the scarp. which there assumes a more northerly COurse. Two notches in the sky liDe of the scarp mark structural valleys truncated by the fault. In B a t the left of the center is shown a large inclined fault splinter, the north end near the top of Lhe scarp and the south cod Dca r lhe basco From the cenler of the v iew to the right edge are thinner fault splinters, with less deHuile boundaries. In C Lhe train of lhinncr spLiuters continues. At the right. is the north end of a short ridge, the Lilted fault hlock m arked a ill Figure 50 
u. S . GEOLOGICAL SUnVEY PROFESSIONAL PAPER 153 PLATE 37 

A. LENTiCULAR BUTTRESS ON MODOC FAULT SCARP, A LITTLE SOUTH OF MODOC POINT 

B. HILLS SOUTH OF LAKE, FROM THE EAST 

The forms of the hills are ascribed to block faulting. In the distance are volcanic mountains of the Cascade system 

TOPOGRAPHIC DETAILS NEAR UPPER KLAMATH LAKE, OREG. 
U. S. GEOLOGICAL SURVEY PRO~'ESSIONAL PAPER 153 PLATE 38 

A 

B 

FAULT SCARP AT MOUTH OF LOWER CANYO OF KEHN lUVER. CALIF. 

}'rom photographs hy W . C. Mendenhall. The scarp trends northwest. The two views were taken from the sume point. A toward the north and B toward the nOl·theast. The lifted hlock is granite (granod iorite), a baLholiul of the Sierra evada. Against this rest Miocene beds, whieh constitute the hills of the lowland. The facets of the scarp have a slope of 40°. The footwall of the fault, exposed at several 

points, dips 55°-60° 
U. S. GEOLOGICAL SURVE Y 

A. FOOTWALL OF FAULT ABOUT 1,000 FEET NORTH OF THI.!: 

RIVER, LOOKING SOUTHEAST 

PROFESSION AL P APER 1.03 PLATE 39 

B. VIEW SOUTHEASTWARD ACROSS THE MOUTH OF THE 

CANYON 

The profile of theJra. ite body at the lef t (lifted block) shows two slopes. Where prol ecle by talus and other material its slope is t.he dip of the fault pla ne. Above the talus it has bee n graded to a slope li LLI e st.p.eper than t.hat of the talus 

DETAIl.S OJ<' FAULT SCARP AT MOUTH ' OF ,CANYON OF KERN RIVER, CALIF. 
U. S. GEOLOGlCA ~ SURVEY PROFESSIONAL PAPER 153 PLATE 40 

.1. SLUMP TElUlACE UNDEIl SCAH!' 

B. UNSLUMPED SCARP 

DETAILS OF FAULT SCARP AT MOUTH OF CANYON OF KERN RIVER , CALIF. 
.. 

KLAMATH LAKE REGION, OREGON 81 

grams of Figure 52 show two types of cross profile, 

with associated surface material, displayed by the 

slabs, and the third gives a hypothetic section. The 

upper parts of all these slabs resemble the higher part 

of the escarpment and appear to consist of bedded 

lavas. In most places their lower slopes are of talus, 

but in one place outcrops of bedrock occur close to 

the lower edge. 

The hypothetic section assumes that these slabs are 

fault splinters, or parts of a single splinter, and that 

the dip of the fault is about the same as the measured 

dip of the Plum Ridge fault. As to the second 

assumption there may be much question. The surface featur~s would 1)e substantially the same whatever the dip, unless it were at a lower angle than the 

angle of rest. The assumption under which the sides 

of the splinter are drawn as parallel is likewise gratuitous. It is also improbable, for the fact that several 

splinters have been inclined by rotation suggests that 

they do not extend indefinitely downward but wedge 

out. 

habit of a fault scarp and the western rising more gradually. According to the contours on the map neither 

side is of simple form, but the slope of each is interrupted by a trench parallel to the main valley and draining northward. One of these trenches, running south 

to the Modoc scarp, makes a small notch in the scarp 

crest, a notch recorded by the camera in Plate 36, A. 

It appears to me legitimate to interpret these features, which are known only through map contours 

and imperfect distant views, in terms of the physiographic types of the region to which they belong. 

If the region were one of Appalachian structure and 

Appalachian sculpture we should infer that these ridges 

and hollows mark severally the outcrops of resistant 

and yielding strata. If the general expression of the 

landscape had been given by glaciers we might surmise that the ridges are morainic. And so, because 

all the great features, as well as many minor features, 

of the environment have their origin in dislocation, 

h c 

Close to Modoc Point is 

a rounded buttress of lllcertain origin. Its cont9urs as 

well as its profile are convex, 

and its visible part may be 

described as lenticular. No 

evidence was obtained as to FIGURE 52.-Thinner fault splinters of Modoc scarp, near Naylox, Oreg. a and b, Cross profiles, with observed elements 

its internal structure. As we 

drove past it I classed it with the thin splinters, but 

later study of its photograph (see pI. 37, A) inclines 

me to the view that it is a landslide. If it is a splinter 

its type is distinct frolll that of its neighbors. 

The dominant material of the escarpment is basalt, 

and this is disposed in beds which in the scarp section 

nppen,r horizon tal. They may be assumed to incline 

northeastward, parallel to the slope of the upland, 

and to their inclination Inay be ascribed the backward 

slope of the fault-splinter terrace shown in Figure 5l. 

Different rocks and a different structure were seen 

only at a point east of the Iniddle of Plum Ridge, where 

high on the scarp lie rocks distinguished from the 

basalt by color and weathering and showing high dips 

in two or Inore directions. This portion of the Modoc 

scarp is not creased by streams from the upland above 

it. The contours on the map indicate that the slope 

of the upland is eastward from the very crest. The 

notch seen in the crest line near Modoc Point (pI. 36, A) 

does not mark a valley of erosion an teceden t to the 

Modoc fault but a dia~trophic valley, presumably contemporaneous in origin. The trend of the valley is 

a little east of north, as indicated by the map, and 

its main drainage is northward. The divide is close 

to the Modoc scarp. Its sides, so far as visible from 

Plum Ridge, are of unequal slope, the eastern having the 

of structure; c, ideal section . 

I am confident that dislocation is responsible for these 

also-that the fault block of which the Modoc scarp 

is the southwestern is here locally sliced by a group of 

north-south faults with down throw to the west and 

that the intervening blocks are tilted to the east. 

I note in passing that the lenticular buttress above 

described lies immediately below the smaller notch in 

the crest of the Modoc scarp. 

For 7 miles north of Modoc Point the escarpment 

faces an open plain, and in following the road across 

the plain we had an unobstructed view of it, although 

mostly at a distance. Farther north the country is 

timbered, and our route through the timber afforded 

only here and there glimpses of the escarpment. In 

the portion best seen the face resembles that of Plum 

Ridge. There are no fault splinters. The slope is 

approximately at the angle of rest. Outcrops of rock 

appear to be of bedded lava, and these are visible 

from the crest downward. On the average their 

lower limit is at midheight, but at one place they 

leave only the lower fifth of the profile to talus. Thp. 

profile of the' detritus does not clearly distinguish a 

talus portion from a flatter basal apron but shows a 

continuous curve ,from the top of the talus to the 

alluvial plain. There is no furrowing of the face by 

erosion1 but it is divided by four sharply cut canyons. 
82 STUDIES OF BASIN-RANGE STRUCTURE 

The upland slopes backward from the crest of the 

scarp, and the back slope meets within a few nliles 

the fore slope of another less regular ridge, thus 

defining an upland valley. The. canyons carry the 

drainage from this valley. At the mouth of each 

canyon lies an alluvial fan, whose slope is adjusted to 

the slope of the canyon bed. Two of the fans are 

small and steep, and the ravines above them look 

youthful. The other fans are broad and flat, and the 

associated canyons are shown by the map to drain 

larger areas. 

The valley with four outlets is the structural valley 

that forms the notch in the sky line near Modoc Point 

(p. 81 and pI. 36, A). The fact that its drainage 

escapes at four points instead of one indicates that 

before the uplift and eastward tilting the tract was 

divided by eastward-trending ridges, and its drainage 

ran either eastward or westward. It is therefore prob- . 

able that the present lines of westward drainage are 

antecedent to the uplift. A few miles farther north 

Sprague River crosses the upland in a youthful canyon that is clearly antecedent. The fact that the 

river was not diverted to an easier route around the 

north end of the uplift and the further fact that the 

small streams retained their courses give assurance 

that the rising of the fault block was gradual. 

At the mouth of its canyon Sprague River is bordered by volcanic agglomerate, and the same material 

occurs in a hill that stands west of the main fault 

scarp. At several points west of the scarp sedimentary 

strata, chiefly sandstone, are exposed, and at one 

point these are overlain by agglomerate. In a railway cut north of Chiloquin station the sedimentary 

beds show folds that have steep dips. 

Most of the general statements concerning the Plum 

Ridge scarp apply also to the Modoc. The terrane 

dislocated in the creation of the Modoc scarp included 

sedimentary beds, clastic volcanic rocks, and bedded 

lavas, of which the lavas are the latest wherever 

sequence was noted. The· prefaulting topography 

was of moderate relief. Faulting was accompanied by 

tilting. The blocks east of the fault were tilted 

eastward. 

Except at the extreme north the dominant rock in 

the scarp face is basalt, and the associated scarp profile approximates the slope of angular talus. At the 

extreme north other rocks are exposed, and the scarp 

is less regular and less youthful in appearance. 

Through· a middle· tract .the fracture was compound 

and the scarp face shows many slablike splinters. 

South of Modoc Point the drainage of the uplifted 

block is conseq uen t, and the higher edge of the block 

parts the waters. North of Modoc Point the principal drainage is antecedent, five streams having persisted and cut trenches through the ridge. 

The sharpness of these trenches and the fact that 

the scarp face is in general unfurrowed testify to the 

youth of the scarp. The persistence of antecedent 

streams speaks of gradual growth, but no evidence was 

found that growth has continued to the present time. 

FORT KLAMATH ESCARPMENT 

.The scarp running north from Klalnath Agency was 

seen only from carriage roads. Our route lay parallel to the bluff as far as Fort Klamath and then 

turned westward. The scarp seemed in general less 

bold than its companions, except at one place, and 

there it presents a basaltic cliff so steep that only a few 

trees find foothold. N ear Klamath Agency copious 

springs rise at its base. 

Midway between Fort IGamath and. the Indian 

Agency the level sky line of the scarp is interrupted 

by a notch in the form of a broad U, whose width 

across the top is about four times its depth. The 

bluff is here perhaps 300 feet high, and the sill of the 

notch is halfway up. This hanging valley was noted 

by Professor Johnson, and his interpretation that it 

is the valley of an eastward-flowing stream, which was 

beheaded by the uplift, seems to me well grounded. 

The remnant of the drainage line which is tributary 

to Williamson River is shown on the map. Where it 

crosses the scarp the valley i~ a sharply delimited 

groove, but it has developed somewhat beyond the 

ravine phase. It records rejuvenation, and the stinlulation of the stream's local activity lnay plausibly be 

ascribed to the uplift that created the scarp. The 

edge of the uplifting block may be pictured as an 

obstruction to the stream,. through which it erodes a 

ravine, and the stream has time to begin the broadening of its narrow way before the continuance of dislocation opens another outlet for its water. 

About a mile north of the hanging valley a fault 

splinter was noted. 

I did not visit the region ilnmediately south of 

the Klamath Agency, but certain details of the map 

indicate that the scarp, instead of ending at the 

agency, continues southward with lessened height for 

about 7 miles. There is a suggestive contour: the 

east shore of the north arm of the lake is nearly 

straight and is not bordered by marsh, and a road 

deviates to follow the lake shore instead of taking a 

more direct course. If the scarp has the extent thus 

indicated its entire length is 23 miles. It is possible 

that the fault continues still farther and curves eastward, to join the Modoc fault of Modoc Point, its 

topographic expression being concealed by the valley 

deposits. 

THE FACE OF THE CASCADE RANGE 

The Fort Klamath scarp springs abruptly from a 

plain of peculiar evenness, which in that part is 6 to 8 

miles wide, and west of the plain rise mountains of the 

Cascade system. (See map, pI. 34.) F&rther south 

the plain is wider and is in p&rt flooded by the w&ter~ 
L 

KLAMATH LAKE REGION, OREGON 83 

of Upper Itlamath Lake. Beyond the end of the Fort 

ICla.math scarp it is walled on the east by the 1\10doc 

scarp. South of the latitude of Modoc Point it is 

divided by a chain of hills. 

The 1nountains that stand next to the plain on the 

west side have the appearance of volcanoes long extinct and, for the 1l10St part, maturely dissected. 

Their principal peaks, from 2 to 3 11liles back from the 

cdge of the plain, rise fronl 2,000 to 4,000 feet above it. 

FroIn the north end of the plain to Pelicnn Bay, a distance of 20 ll1iles, the ll10lmtain ll1ass is continuous, 

and a broad but isolated mountain stands south of 

Pelican Bay. 

The nlountains are forested to their base, but the 

plain is open. Our observations included distant 

views fronl the plain and such inspection of the base 

as could be made by following a carriage road through 

the forest. As inferred fr0111 the distant views, and 

especially from the contours on the map, the character 

of the topography changes at this line of front. 

Parallel ridges and linear escarpments, which are 

characteristic features on the east side, occur on the 

west only as spurs between gorges of erosion and as the 

walls of canyons. The ll10untain front is rather bold 

and exhibits a notable al110unt of alinement, features 

which in their combination are strongly suggestive of a 

line of dislocation. The exanlination of the mountain 

base failed to discover evidence or' faulting coordinate 

with that of the scarps east of the. plain. The rock 

base is definitely lnarked, and its outline is simple 

except where it is crossed by large streanls, but the 

slope does not approach the talus angle. The rock 

base is fringed by an apron of alluvium, and large 

low-grade fans have been spread by the larger of the 

crccks that issue fr0111 the range. Opposite Pelican 

Bn,y, where the chain of volcanoes is interrupted by a 

transverse valley, both apron and fan are submerged 

beneath lake waters and 111arshes. 

From these data I infer, as probable, that the eastcrn face of the Cascade Moun tains was here determined 

by a fault with throw to the east; that the dislocation 

occurred after the principal eruptions by which the 

rn,nge was built but before the excavation of the great 

canyon valleys by which the mountains have been 

dissected; and that the valley which is occupied in 

part by Upper IClamath Lake was created afterward 

by the uplift of tracts along its eastern and southern 

111argins. The scarps described on earlier pages perttLill to the later epoch of dislocation. 

RIDGES WEST OF UPPER KLAMATH LAKE 

Mention has been made (p. 79) of a group of snlall 

ridges about the south end of Plum Ridge. This 

group may be thought of as the eastern end of a 

barrier which runs west-southwest to Klamath River 

and separates the basins of Upper Klamath and Lower 

IClamath Lakes. The outlet of the upper lake crosses 

the barrier at Klamath Falls. The barrier is irregular 

in form and is COlllposed of many hills or small ridges 

which individually trend parallel to Plum Ridge, or at 

right angles to the general line of the barrier. North 

of the barrier are scatter~d small ridges with the same 

general trend, and a chain of somewhat larger ridges 

runs northward for 15 miles, separating Long Lake 

Valley from W ocus Marsh and Aspen Lake from 

Upper Klamath Lake. 

I had a near view of ridges about Long Lake Valley 

and distant views of many others, so that I was able 

to extend an observation Inade by Professor Johnson 

that the fault-block system west of Plum Ridge is 

antithetic or complement~ry to the PIUl11 RidgeNlodoc systenl in that the prevailing throw of the 

faults is on the east side and the prevailing tilt of'the 

blocks is to the west. 

The number of distinguishable ridges is large, and 

the nUlnber of component fault blocks is larger. 

From data in my n'otes and photographs I could enumerate about 15 blocks, and the actual number must be 

several times as great. It is a region of minute 

slicing of the preexistent terrane. 

Plate 37, B, shows a group of westward-dipping 

ridges, as seen from the southeast. 

FIGURE 53.-North end of Long Lake Valley, Klamath County, Oreg. 

A few scarps have such height and length that they 

lllay be distinguished as major, although they are not 

comparable with the major scarps of the eastern system. Perhaps the most prominent of these is the scarp 

that borders W ocus Marsh, but this I know chiefly 

from the map. Another borders Upper Klamath Lake 

from Squaw Point to Porcupine Point and is strongly 

expressed by the con tours. The bedding of the associated ridge, as seen from the east, appears to lie nearly 

level. 

A third major scarp walls Long Lake Valley on the 

west and }- as the sharp definition of the Modoc scarp. 

It is about 8 miles long and 300 to 400 feet high. At 

the north end of the valley it is intersected by a southward-facing scarp, and the topography suggests that 

two faults here cross. Figure 53, although based on a 

photograph, is in part sketched, for the distant hills, 

of which the camera recorded only the sky line, have 

been interpreted by the aid of a notebook diagram. 

At the right are shown profiles of the east wall of the 

valley, a dip slope. At the left is shown t\. st\.lient of the 
84 STUDIES OF BASIN-RANGE STRUCTURE 

west-side scarp, here less steep than elsewhere. Beyond the salient the scarp reappears in the distance 

with its normal facies and then abruptly ascends, as if 

climbing 'over the intersecting scarp and ridge. 

If the tentative interpretation of these features is 

correct, and one fault is here crossed by another, the 

occurrence is exceptional rather than typical. Ordinarily in this region the meeting of two faults is by 

the ending of one against the plane of the other. 

THE VALLEYS 

The only valleys of the district which can be ascribed 

to erosion are narrow and youthful, the canyons of the 

uplands. Although the surface rocks are chiefly volcanic, none of the lake basins of the district have 

originated through the obstruction of drainage .by lava 

flows. All the lowland valleys and most of the upland 

valleys, except in the Cascade Mountains, are tectonic. 

The valley of Upper Klamath Lake, which was 

created by uplift on the east and south, has received 

large deposits and is conspicuously flat-so far as its 

bed is visible. Its flatness is evidently due to deposition. The largest of its plains, built by outwash from 

the slopes of the Crater Lake mass" is composed of 

pumice, and that material is presumably the chief 

factor in the filling of the valley. From the edge of 

this plain to the main body of the lake the valley for 

10 miles is occupied by marsh, and there are many 

other marshy tracts about the shore. The presence of 

these marshes suggests that the gentle slopes of the 

visible parts of the valley floor are continued beneath 

the water. 

As already mentioned, the fault-block hills which 

diversify a part of the valley all lie south of Modoc 

. Point. If such hills were formed in the northern tract 

they have been buried by the flood of pumice. 

Southwest of Pelican Bay a carriage road follows for 

some distance a beach ridge which is adjusted in height 

to the present level of the lake but is no longer washed 

by the lake waves. Between the beach and the open 

water lie 2 miles of marsh, and the age of the beach 

is measured by the time necessary for the development of the marsh. The fact that the local lake 

level has not changed in that time indicates stability 

not only of this part of the coast but of the sill at Klamath Falls and accords with the physiographic evidence that the fault scarps have not grown in very 

recent time. Of the same tenor is the statement, by 

a resident for 30 years, that no earthquakes have 

visited the region. 

Long Lake Valley, the valley east of Plum Ridge, 

and, in less degree, the valley of Aspen Lake are notable for the flatness of their floors, and the same remark 

applies to the broader valleys of Upper and Lower 

Klamath Lakes. The sharp change in slope at the 

base of a scarp is commonly due in large part to the 

burial of its base by the flat-topped valley deposit. 

Hills that rise from the floors of the larger basins have 

inconspicuous alluvial aprons and appear as islands in 

a sea of alluvium. It has occurred to me that the association of mature gradation of valley floors with the 

youthful topography of fault scarps may be connected 

with an abundance of volcanic ash. Pumiceous sand 

such as was seen near Fort Klamath is so little 

heavier than water that it can be redistributed by 

streams with great rapidity. Its available quantity, 

LAKE. 

VALLEY 

9L-_l---l-_l---l-----I1 MILES 

FIGURE M.-Map of Swan Lake Valley and vicinity, Oregon. 

From the Klamath topographic map. Contour interval, 200 

feet 

unlike that of other easily moved debris, is independent 

of the slow processes of rock decay. The sheet spread 

over the land by an explosion may be quickly gathered 

in the hollows and graded to gentle slopes. 

THE PREFAULTING TOPOGRAPHY 

The occurrence of parallel beds of basalt in the upper 

parts of the principal scarp fa~es suggests the existence of a broad lava plain before the period of disloca-
L 

KLAMATH LAKE REGION, OREGON 85 

tion in which the scarps originated, but there is also 

evidence that the lava plain was neither omnipresent 

nor uniformly leViel. 

N ear the north end of the Modoc scarp lie tracts 

that are occupied by sedimentary rocks and agglomerates, the former older than the latter. N ear the 

south end of Plum Ridge stand hills of sandstone 

without lava caps, and not far away there is an exposure of sandstone beneath a lava bed, It is not to be 

supposed that the sedimentary rocks were wholly 

covered by lavas at the time of the dislocations that 

produced the Modoc and Plum Ridge scarps, for 

a period of erosion sufficient for the removal of the lava 

caps would not have left the scarps unfurrowed. It 

is possible that the sedimentary rocks were not everywhere buried, and it is also possible that, after having 

been buried, they were locally denuded in consequence 

of uplifts which preceded the dislocations associated 

with the existing scarps. My data are too meager for 

the discussion of such suggestions. 

Although the long scarps are in many respects 

renlarkably uniform, their crest lines, or the upland 

strips immediately adjacent to them., are somewhat 

uneven. The forms of a few inequalities are such as 

to indicate origin by erosion, and the forms of a few 

others indicate dislocation, but there are yet others 

which are more plausibly explained as features of the 

prefaulting topography. They are smooth hills of 

moderate slope, except as affected by faulting, and 

may be the worn remnants of small volcanoes. They 

were not visited, and the suggestion as to their nature 

comes in part from their association with the widespread lava flows and in part from Russell's description of an unfaulted lava field in central Oregon.3 

a Russoll, I. 0., U. S. Gool. Survoy Bull. 252, 1905. 

The hypothesis that before the period of dislocation " 

the general features of the region were a lava plain and 

volcanic hills to mark points of eruption is in accord 

with the shapes of hills and small mountains a little 

farther south, as interpreted from distant views and 

from the windows of railway trains. The Laki Peak 

group, as seen from the northwest, has unmistakable 

block-fault characters; its southwest face, straight 

and cliff-like (see fig. 54), which springs abruptly 

from a plain that inclines toward it, is clearly a fault 

scarp, and a strong spur farther east is bounded on 

the southwest by a fault scarp; but the summit forms, 

except at the extreme west, are of a distinct type. A 

group of hills that trend southwestward and border 

Lower Klamath Lake on the northeast appear from 

the north to be bounded on both sides by fault scarps, 

and their tops include plain elements that have a gentle 

tilt toward the east, but above the plain elements are 

also rounded summits. A line of southeastwardtrendfug hills, which is crossed by the railroad near 

Dorris, shows tabular summits with moderate inclination, as if faulted up from an even lava plain, but 

the forms of the group of larger hills south of Dorris, 

though equally characteristic of block faulting, suggest 

a less even antecedent surface. 

These neighboring uplands, which offer for study 

distrnct phases of fault-born relief, aroused longings 

for close acquaintance that could not be gratified. 

I commend them to students of mountain structure 

and add as a special attraction that close at hand is 

a fault splinter of magnificent proportions. One may 

read from Mr. Ricksecker's faithful contours in Figure 

54 that the northeast wall of Swan Lake Valley is a 

fault scarp that is comparable with the Modoc, and 

that a splinter more than half a mile in width slopes 

southward along its face. 
CHAPTER V. FAULT SCARP NEAR BAKERSFIELD, CALIFORNIA 

GENERAL FEATURES 

The photographs reproduced in Plate 38 were made 

by my colleague Mr. W. C. Mendenhall and gave me 

my first intimation that the western base of the Sierra 

Nevada is in part defined by a fault. The fact was 

well known, however, to others and has been recorded 

in the literature of the range. Mention of faults in 

this particular locality is made by Anderson. 1 The 

scarp as pictured has a strong family resemblance to 

the western faces of the Wasatch and Logan Ranges 

and is a fine example of a youthful fault scarp in 

nearly homogeneous material. I availed myself of the 

first opportunity to visit the locality (in October, 

1914) and was so fortunate as to have the companionship and guidance of Mr. C. L. Moody, of the University of California, who, as a student of the Miocene 

fornlations of the district, had acquired an intimate 

acquaintance with the local geography and geology: 

At a point about 15 miles by road east of Bakersfield, Kern River leaves the great granite body of the 

Sierra and enters a district occupied by easily eroded 

rocks of Miocene age. It is possible that but for the 

work of the river the contact of the two formations 

would not have a strong topographic expression at 

this point, but the river, while carving only a narrow 

passage for itself through the granite, has developed 

a terraced valley just beyond. Through that development and through the activity of small tributary 

streams the face of the granite has been exposed. 

My primary motive in visiting the locality was to 

learn whether the photograph's testinlony to the 

existence of a fault is supported by other evidence. 

The picture shows a mountain block dissected by 

youthful canyons and bounded by a nearly straight 

face. The face is divided by the canyons into facets, 

which are· triangular where narrowest and trapeziform where broader. The general slope of the face 

seems to be about as steep as that which has been 

acquired through gradation by scarps in the Klamath 

Lake region, but at the left of the river canyon the 

lower part of the face is steeper and smoother-just 

as the fault face on Plum Ridge, in the Klamath region, 

is steeper and smoother than the graded part of the 

scarp. So one of the questions to be answered by 

close inspection was whether the steeper wall bears 

the polish and striae of the footwall of a fault. Other 

questions pertained to the character and attitude of 

the Miocene beds at and near the contact. If the 

granitic batholith were younger than the strata 

1 Anderson, F. M., The Neocene deposits of Kern River, Calif., and the Temblor 

Busin: Cali~ornia Acad. Sci. Proe., 4th ser., vol. 3, p. 82, pI. 6, 1911. 

86 

(a relation for various reasons highly improbable) 

there might be metamorphism. If the granite face 

were a sea cliff created or steepened by the waves of 

the Miocene ocean, the waste from cliff erosion should 

appear in the adjacent sediments, whereas if the present relation were brought about by the upfaulting of 

the granite the sediments would not have characters 

indicative of the immediate presence of a granite cliff. 

VERTICAL GROOVING AND JOINTS 

N ear-by inspection of the steeper face found no 

well-defined slickensides, which the surface of the 

granite is evidently too weather-worn to preserve, 

and no fault rock. There is, however, a vertical 

grooving, or coarse striation, which is best seen at a 

FIGURE 55.-Ideal segment of the granite body near mouth of Kern 

River Canyon, Calif., showing graded and ungraded portions of 

scarp and the relations of terraces to joint systems 

little distance, and there are many small patches of 

thin quartz vein which are vertically fluted in harmony 

with the grooving. These features tell of differential 

movement along the exposed plane-or rather planes, 

for the face is made up of several plane elements, 

which are parallel and separated by narrow terraces. 

A portion of the lowest plane element is pictured from 

a photograph in Plate 39, A, and the relation of the 

elements to the terraces is shown diagrammatically in 

Figure 55. The terraces are llarrow, they are occupi,ed 

by soil and other loose waste, they are parallel, and the 

lines they trace across the face are oblique, rising from 

left to right. 

Both the plane elements and the terraces are 

associated with joints. Among the many joints by 

which the granite is riven it is possible to distinguish 

three sets as relatively notable. One of these coincides 
.1-

FAULT SCARP N1!lAR BAKERSFIELD; CALiF. 87 

in strike (southeast) and dip (59°) with the plane elements of the rock face. The joints of the second set 

dip obliquely into the mountain at about 25°, in such 

a way that the lines in which they nleet the rock face 

are parallel to the terraces. Those of the third set 

dip 80° SE. and strike at right angles to the rock face. 

Only the first and second sets are indicated in Figure 

55. The plane elements of the rock face are either 

joint surfaces of the first set or dislocated parts of a 

single joint surface. The terraces are in some way 

determined by joints of the second set. It appears to 

rne nlost probable that the plane elements were once 

united as parts of a single joint surface and that after 

the differential nlovement which produced the vertical striation they were separated by small moveInents of the nature of step faulting, which took place 

on joints of the second set. 

The 'evidences of differential movement were seen 

only on rock surfaces belonging to the system of joints 

first Hlentioned. They were well observed only on the 

outer surfaces associated with the terraces, but patches 

of white ascribed to vein quartz were seen far up the 

slope on inner joint surfaces which have been exposed 

by erosion (that is, on the "graded rock slope" of 

fig. 55), and if such occurrences are similar to those on 

the outer surfaces it would appear that the differential 

mov.ement was not restricted to a single plane but was 

more or less diffused through a zone.2 

The steep face partly shown in Plate 39, .A, and diagl'anlmatically represented in Figure 55, is about 400 

feet high. There is no suggestion as to the vertical 

extent of the rock surface to which it belongs, except 

that the visible part is a part only. Above the upper 

limit of the exposure the surface has been destroyed 

by erosion; below the lower limit it is covered by a 

Inantle of talus. No other large exposure occurs, but 

a series of minor exposures (see pI. 40, .A) show that 

the surface continues northeastward for at least 2 

Illiles, and its presence southeast of the river is clearly 

indicated by Plate 39, B. In taking that photograph 

the Call1era was placed approximately in the plane of 

the steep rock surface, with the result that the lines 

of the view bring out the essential relations. The 

granite above the head of the talus has been graded 

to a slope little st.eeper than that given by the talus 

profile, and the slope of the granite where protected by 

talus and associated formations IS about the same ~s 

thttt of the exposed wall north of the river. The body 

of protecting nlaterial is composed superficially of talus 

and near the river of coarse alluvium, but its prirl.-

cipal constituent is doubtless a remnant of a Miocene 

formation, which occurs in neighboring hills at the 

sanle level. 

Tho steep granite face revealed by the exposures 

and by the quasi section, which stands at an angle 

B Beckor, G. F., Geology or the Comstock lode and the Washoe district; U. S. 

0001. Survoy Mon. 3, ch. 4, 1882. 

greater than the angle of rest, is a cliff and as such is 

a feature to be explained. Cliffs have many modes of 

. origin, but the only ones that need be considered here 

are those by wave attack and by faulting. The association of the cliff with marine deposits may properly 

raise the question whether the waves of the Tertiary 

sea created it as a shore cliff by sapping at its basco 

H such were its origin the accordance of the cliff with a. 

joint plane, or with ~ few joint planes, must be ascribed 

to coincidence; but the difficulty thus suggested is 

perhaps less serious than the difficulty of accounting for the burial of the cliff by marine sediments. 

In order that the sediments might be deposited after 

the creation of the cliff the land must have been submerged, and during the submergence the waves would 

attack the cliff at levels above its base and remodel itunless, indeed, the submergence were catastrophic. 

It is evident that the hypothesis of origin by faulting 

does not encounter these difficulties. 

CHARACTER AND RELATIONS OF THE MIOCENE BEDS 

I turn now to the evidence which may be afforded by 

the character of the Miocene beds and by their relation 

to the granite. The beds are in general so soft and they 

weather so readily into a condition of incoherence that 

their sequence and structure are not apparent. Outcrops that show dips are rare and discontinuous, and 

there has been so much slumping of hillsides that many 

observable dips are of doubtful significance. Several 

miles north of the river the formation includes a thin 

limestone, and 1 or 2 miles south of the river it includes 

a conglomerate, but these exceptional strata are of 

slight extent, and their order of sequence has not been 

established by stratigraphic evidence. 

At the river the granite upland stands 2,500 feet 

above the Tertiary lowland. Toward the northwest 

the upland loses in height and the Tertiary hills gain 

in height, until at a distance of 3 miles no noteworthy 

difference remains. The line of contact between the 

two formations, which for that distance is direct and 

distinct, then becomes sinuous and indefinite and 

swings' toward the northeast. It ceases to be the 

boundary of a Tertiary formation resting against the 

granite face and becomes that of a Tertiary formation 

overlying the granite. In the region in which the 

Tertiary overlies <the granite the limestone bed crops 

out on the side of Pyramid Hill, at an altitude of 

2,000 feet above sea level. Where the Tertiary beds 

rest against the granite face 2 miles farther south 

there is an outcrop of the same bed at about 1,400 

feet above sea level. The difference in height is not 

accounted for by such observations of dip as are available and may plausibly be ascribed to dislocation. 

At the lower locality the outcrop is sO close to the 

granite as to give significance to the testimony afforded 

by the limestone on conditions of deposition. The slope 

of the granite face is there about 40°, and a narrow 
88 STUDIES OF BASIN-RANGE STRUCTURE 

spurlike hill of the Tertiary formation rests against 

it, essentially in the manner represented by Figure 

56, which is a diagrammatic sketch from memory. 

The limestone bed appears in the side of the hill, 40 . 

feet from the granite, and dips away from the granite 

at 19°. The stratum consists largely of unbroken 

shells of Pecten, Dosinia, Chione, Natica, Dentalium, 

Bullia, and other forms and tells of deposition in quiet 

water. It· is manifestly out of place in its present 

relation to a granite cliff if that cliff was carved out 

by the waves of the Tertiary sea, but its position and 

attitude are in accord with the hypothesis that the 

cliff was created by faulting. 

FIGUltE 56.-Ideal sketch to show the relation of an observed 

outcrop oC limestone (I) on a hill oC Miocene beds to the 

granite face (g) against which the hill rests, Sierra Nevada, 

CaliCo 

The bed of conglomerate is not closely associated 

with the granite face. Its outcrop is 2,000 feet from 

the contact, and the plane of its dip is such that when 

projected upward from the outcrop it passes above 

the granite. 

SUMMARY AND CONCLUSIONS 

To recapitulate: The granite escarpment is nearly 

straight for about 5 miles, except that where it is graded 

by recent weathering it has the steepness of a cliff, 

and it is faceted. These features indicate that the 

mass has been truncated. The possibility of truncation by fluvial or glacial erosion need not be considered, 

because no companion wall faces the escarpment. 

The hypothesis of the formation of the cliff by wave 

action is discountenanced by the smoothness of those 

parts .of the cliff which are well preserved, by the 

difficulty of explaining its preservation during burial 

by marine sediments, and by the fact that the character 

of the sediments does not indicate the near presence 

of a granite shore cliff. Truncation by faulting is 

indicated by the coincidence of smooth cliff faces with 

join t planes and by the evidence on those planes of 

differential movement but lacks the confirmation 

which would be afforded by the presence of fault rock. 

The local exposure of 400 feet of the fault wall 

(see pI. 38) is a noteworthy feature. The locality is 

not far from a low terrace made by the river, but no 

evidence was found that the river in the swinging of 

its meanders actually washed the base of the cliff. 

The local details indicate rather that the approach of 

the~ river caused a landslide, and that the slid body 

of Miocene beds, after moving into the track of the 

river, was washed away, with the exception of a smal1 

remnant. Since that event the river has shifted to a 

new position and has sunk its channel to a lower level. 

The time that has elapsed since the- occurrence of the 

landslide is the time during which the fault wall has 

been exposed to agencies of weathering. 

The remnant of the slid mass, which may be seen 

in Plate 38 and which appears at a in Figure 57, is 

sheathed by large angular blocks of granite, quite distinct from the worn boulders of the river terrace. 

These blocks must have come from the upper slope of 

the granite, h, but could not make the journey under 

present conditions. It may be assumed that they once 

rested on a graded slope of Miocene beds, became more 

or less mingled with the material that composed those 

beds during the sliding, and have been concentrated on 

the present surface by the washing out of finer material. 

The talus at c has been built since the slide, and so has 

the sloping plain of alluvium betweelJ c and a. 

A series of peculiar terraces associated with smaller 

exposures of the fault wall admit of a similar explanation. Their type is illustrated by Plate 40, A, where 

numerous angular blocks (at the left) are separated 

from the parent body of granite (at the right) by an 

alluvial plain of gentle slope which is the platform of a 

terrace. The outer face of the terrace is outside the 

field of view but may be seen in Plate 38. Here also 

the phenomena are ascribed to sliding. A large body 

of ·Miocene deposits has moved forward from the 

NE. 

FIGURE 57.-Profile of fault scarp at principal exposure of footwall 

north of Kern River, Calif. 

granite and has at the same time either rotated toward 

it or else slumped along its upper edge, with the result 

that its crest stands at some distance from the granite. 

The interspace has since been aggraded by waste, 

fine and coarse, from the upper slope of the granite, 

but degradation of the crest has been arrested by the 

coarse waste there lodged. The outer faces of such 

terraces bear many large angular blocks, and so do 

certain terraces and outlying hills at lower levels. It 

is evident that the history of sliding has not been 
:f 

1 

• 

FAULT SCARP NEAR BAKERSFIELD, CALIF. 89 

simple, but it can not now be read in full because much 

of its record has been effaced by subsequent erosion. 

I discovered no evidence of recent renewal of faulting. Because the jar of an earthquake is often the 

ilnmediate cause of a landslide, such sliding.,as has here 

taken place would have been a natural accompaniment 

of renewed faulting, but if the baring of the fault wall 

were due to renewed faulting it would be more general 

62436-28--7 

, 

in its distribution than is actually the case. South of 

the river the yielding formations in contac,t with the 

fault wall are undisturbed, and north of the river 

tracts without disturbance (see pI. 40, B) alternate 

with tracts affected by sliding. The sliding appears to 

have occurred only where the stability of the Temblor 

Hills was impaired by the sapping work of the river 

and its tributaries. 
r 
INDEX 

Page Pap 

Acknowledgments for aid __________________________________________________ • 76 Faults, locations oL _________________________________________________________ 14-19 

Alpine, Utah, fault-block spur near ___________________________________ 27-29,31-33 marginal, summary of development oL _________________________________ 67-69 

fnult phenomena north oL______________________________________________ 15 nomenclature of _________________________________________________________ 11-12 

American Fork, facets ncar, plate showing_ _ _ _ _ _____________________________ 40 products of friction in, kinds of. ______________________________________ 12-13,21 

Anderson, G. E., work or, on tho drainago or tho Wasatch Range____________ 64 within the Wasatch Range ______________________________________________ 64-66 

Appalllchb'in Mountains, development oL__________________________________ 1 Fish Springs Range, faults adjoining __________________________________ 70-72,73,74 

Apron, alluvial, definition oL _____________________________________________ •• 1l general features of. _ __ __ _ __ _ ____ __ _ _ _ __ _ _ _ _ _ _ __ _ ___ ___ _ __ _ ______ _ ___ _ ____ 70 

Back valleys, use of term ___________________ • ________________________________ 53-54 hot springs near __________________ ~ ______________________________________ 72-73 

landslide on ___ • ____________________________________________ • ____________ 71-72 Baker, C. L., cited _____________________________________ .____________________ 8 map of _. _ ________ _ _ _ ____ __ _ _ __ _ __ __ __ _ __ _ _ ___ _ ______ _ __ _ _ __ _ _____ _ __ __ __ 72 

Bakersfield, Calif., fault scarp ncar ___________________________________ • _____ • 86-89 

Basin Range structure, use of term _____________ ._. _____________ .____________ 1 

piedmont scarps adjoining ___________________________________________ ._ __ 71 

rocks constituting _ _ ___ _ __ __ _ _ __ __ _ _ ___ _ _ ___ ___ __ _ ____ __ _ _ _ _ _ __ ____ __ _ _ _ _ 74 

Battle Creek, Utah, fncets ncar, plato showing_. ___________________________ • 40 western face of, plates showing _ _ _ __ _ ___ _ ____ __ _ ____ ___ _ _ _ __ _ _ _ _____ _ _ ___ 72 faulting noar _________________________________________________ • _______ •• _ 66 structure ot. __ _______________________________________________________ 73-74 

, Beck's Spring, Utah, fault phenomena near ______________________________ ._. 16 

Bonneville, JJako, effect of waves in, on the Wasatch escarpment ___________ • 43-44 

FlOW, production of, by faulting__ __ ____ _ _ __ _ __ ___ _ _ ___ ___ _ __ _ _ _ _ ____ _ _ _ _ _ _ _ _ 12 

Fort Canyon, Utah, fault phenomena near __________________________________ 15 

modification of the frontal fault by _______ • ___ • _________________________ • 12 

shore line oL ___ •• __ ____ __ _____ __ _ __ __ ________________ _____ ___ ___________ 12 

platos showing ___________________________________________________ 16,24,40 Grade plains, high-level, plate showing______________________________________ 40 

Grand Canyon of the Colorado, topography of the region north oL__________ 42 Boxolder Creek,.Utah, crossing of tho Wasatch Range by __________________ • 63-64 

California earthquake, fault cracks associated with _ _ ________________________ 13 

landslides started by _____________________________________________ , _____ • 35 

ridges produced by ____________________________________________________ •• 36 

Canyons of the Wasatch Range, truncation oL _____________________________ • 41 

through, development oL __ ~ _________________ • ___ • ______________________ 62-63 

Cascado Hange, features of cast face oL __________________________ • __________ 82-83 

City Creek spur, description of __ • ___________________________________________ 22-24 

Hague, Arnold, cited_ ___ __ _ __ ___ ___ ___ __ __ ____ __ __ ___ _ __ _ _ ____ __ ____ _ ____ _ __ 26 

Heber Valley, description and history oL ___________________________________ 55-56 

plate showing __________________________________________________________ • 56 

Hintze, F. F., work of, on cross drainage____________________________________ 54 

Honeyville, Utah, spur, description oL _____________________________________ 29-30 

scarp opposite, plate showing~___________________________________________ 24 House Range, map ot. _________________________________________________ ~__ ___ 72 

structure oL _____________________________________________________________ 74-75 

origin oL ____ •• _________________ • _____________ • _______ • __________________ 31-33 

plato showing _. _________________________________________________________ 16 

Clayton Peak, features oL _ _ _ _ _________________________________________ _____ 51 

west front of, plate showing_ _ _ _ _______________________________________ __ 72 

Howell, E. E., work of, on cross drainage ____________________________________ 54-55 

Corner Creek, ancient channel of, plate showing ____________________________ • 24 Jordan Valley, features oL __________________________________________________ 51-52 

groin followed by, plate showing________________________________________ 24 Jump-off Canyon, Utah, fault phenomena at _____________________________ 16,17-18 

Davis, W. M., study by ____ ._______________________________________________ 5-6 plates showing ____________ .--------- ______ ___________________ ___________ 16 

Detritus in faults, forms and sizes oL_______________________________________ 12 

Diastrophism, criterions for discriminating between earlier and later_________ 65 Drainage, cross, in tho Wasatch Range ________________________________ 53-55,63-64 

Draper, Utah, fault phenomena at. _______________________________________ ._ 15 

Dry Lako trough, description and origin oL ______________________________ ... 59-62 

map oL __________________________________________________ ----------._ ___ 64 

Dutton, C. ]~., cited _____ • ____ ._____________________________________________ 3 

Kamas Prairie. See Rhodes Valley. 

Kern River, Calif., escarpments on, plates showing ___________ • _____________ • 40,80 

Keyes, C. R., cited__________________________________________________________ 7-8 

- King, Clarence, cited _____________________________________________ ~ _________ 2-3,52 

-.'Klamath Lake Region, Oreg., description of elements oL ___________________ 76-85 prefaulting topography oL ______________________________________________ 84-85 

valleys oL _________________________________________ • ________ • ________ ._.. 84 

Eden Pass, description and history oL ___________ • ___________________ ._ ••• __ 58-59 Knoff, Adolph, cited ________ • ____________ •• ____________ • ___ • __ • ____________ • 15 

.I plate showing ____________ • _______________ • _____ • _________________ • __ •• _. 64 

Emmons, S. F., cited ____________________________________ ~ _____________ .____ 65 

Escarpments, conclusions as to production ot. __________________ . ______ .______ 47 

fault, senilizing oL ______________________________________________________ 68-69 

in alluvium, plates showing __________________________________ • ________ •• 32 

In moraine, plates showing______________________________________________ 32 

In volcanic rock, production oL ________________________________________ • 43 

plates showing _ _ _ _____________ ___ ___ _____ __ ______________ ________ _______ 40 

production of, by ice ___________________________________________________ • 43 

• 

Lakes, deposition in__ _ _ ___ _ _ _ _ _ ___ ___ _ __ ________ _ ____ _ ____ ___ ___ ____ ____ _ __ _ 44 

Landslides, piedmont scarps caused by ______________________________________ 34-35 

plates showing __________________________________________________________ 24,32 

Lee, W. T., on cross drainage _____________________________ ._________________ 54 

Lone Peak, saddle between salient of, and Traverse spur, plate showing_____ 24 

salient of, plate showing ______________________________________ ~-----.--__ 40 

Louderback, George D., cited_______________________________________________ 14 study by _____________________________________ • __________ • _______ • ______ • 6-7 

by streams _______________________ • ___________ • ______________________ 46-47 

plates showing _______ • _____________________________________ eo_e. 40 

by waves ________ ~ _________________________________ --- __ -___________ 43-45 

by wind _______________________ • ____________________________________ 45-46 

related to piedmont scarps, features oL __________ • ___________________ • __ 39-40 

truncating, means of producing ____ • _________________________________ ._. 68 

See also Piedmont scarps. 

Madsen spur, description ot. _____________________________________________ • __ 30-31 

origin oL ____________________________________________________ •• ______ •••• 31-33 

plate showing _________________________________________________ ••• ______ • 24 

Mantua Valley, description and origin oL ________________________________ •• 59-62 

map of part oL __________________________________ • _____ •••••• _______ ••••• 64 

Mill Creek, Utah, fault phenomena on ____________________________ ••••• ___ •• 15-16 

Paleozoic strata on, plate showing _______________________ . ______ ._________ 16 

Facets, plates showing _____________ •• ________ ••• __________________ ._________ 40 shear zone on, plates showing____________________________________________ 16 

produced by faulting, development and decay oL _____________ • ______ 47,48-49 slickensides on, plate showing___________________________________________ 16 

produced by sapping, development and decay oL ____ • __________________ 47-48 Modoc fault scarp, lenticular buttress on, plate showlng __________________ .__ SO· 

Farmington division of the Wasatch Range, old graded slopes in ____________ 49-50 plate showing ________________________________ ._. _______ • ______ •••• _____ • SO 

throw of the frontal fault in ______________________________________________ 52-53 structure of ___________________________________________________ • ___ • ______ 80-82 

Fault, frontal, discussion of evidence of_. ____________________________________ 19-20 Morgan Valley, origin oL _____ ._-. _________________ • ___ • ___ • ___ • ______ 56-57,61-62 

Fault·block spurs, description 01. ___ • ________ · _________ • ______________ · •• _____ 22-31 plate showing ________________ • _. _____________ •• ____ ._ •• ______ • ___ ._ •• __ • 56 

origin of _____ • ________________ • __ • _______________________________________ 31-33 Mountains, processes producing_· _____ • __ ._ •• _ •• _ •••••• _. __ •• __ •••••• _....... 1 Fault·block structure, use of term _________________________________ • ________ • 1 

Fault rock, plates showing. __ • __ •••• ____________________ ._ _ ___ _______________ 16 North Ogden, Utah, fault-block spur near __ • ______ •• _. ___ • ______ ••• _ •• 24-27,31-33 

sources of _~_ ••• ____ •• __ • ___ ••• _ .••• __ •••• ___ ••• _. __ •• _. ______ ••••••••• _. 13 west face of Wasatch Range near, plate showing_ ••••••••• __ ._ ••••••••• _. 16 

Fsqlt Boarp, use of ~rm •••• ---, •••••• -•• -•••••••••••••• -••• _.- __ •••••••••• _. 33-34 North Ogden Canyon, !aqlt phenomena near_ ••••••••• _ ••••••••• _........... 19 

91 

I 
92 INDEX 

Pall Page 

Ogden Canyon, special features or. __________________________________________ 62-63 Slopes, old graded, production oL _________ ~ _________________________________ 49-50 

Ogden Reservoir, Utah, fault phenomena near _______________________________ 16-17 Smith, George Otis, Preface_ ____ _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ __ _ _ _ VII 

Ogden River, South Fork of, plate showing escarpment on__________________ 40 Splinters, Cault, occurrence of, on the Modoc escarpment ____________________ 80-82 

Ogden Valley, description and origin oL ______________________________ 57-59,61-62 Springs, thermal, association of, with fault-block spurs ______________________ 32-33 

Owens Valley, scarps in alluvium oL_______________________________________ 40 Spurr, J. E., cited___________________ _____ _____ ________ ________________ __ _ ___ 4-5 

Parleys Park, location of. _ _ ___ _ ____ __ _ _ _ _ _ _ _ __ _ __ _ _ _ _____ _ __ __ __ _ __ __ __ _ ___ _ 57,62 

Piedmont plain, definition oL______________________________________________ 11 

Piedmont plain, drainage on _ _ _ __ _ _ _ ___ _ _ _ _ __ _ __ _ _ __ _ __ __ _ ____ ___ _ ___ _ __ _ __ _ 39 

Piedmont scarps, definition oL______________________________________________ 12 

Spurs, features of, plates showing____________________________________________ 24 

Streams, erosion by _ _ _ _________________________________ _____ ________ ________ 68 

escarpments produced by, plates showing_______________________________ 40 

Striation of Cault walls, forms oL____________________________________________ 12 

description and cause oC ________________________________________________ 33-39 Taylor Canyon, structure at mouth of, plate showing________________________ 24 plates showing _ _ _ _ _ ___ _ _ __ _ __ _ _ __ _ _ ___ _ _ __ _ __ ___ _ ___ __ ____ __ _ _ _ __ _ _ __ __ _ 32 Tatow Knob, plate showing___ _ _ _ _ __ __ _ _ _ _ _ __ _ __ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ ____ __ _ ___ __ 72 

production oC__ __ __ __ __ _ _ __ _ _ ___ __ _ ___ _ __ _______ ___ _ __ _ __ ___ _ _ __ __ __ ___ _ 69 .Tatow Plateau, features 01. __________________________________________________ 74-75 

effect of slumping in _________________________________________________ 37-38 Timpanogos, Mount, facets in front of, plates showing_______________________ 40 relative ages of. _ _ _ __ __ __ _ __ _ ___ _ __ _ ___ _ ___ __ _ __ __ __ _____ __ ______ _ __ __ _ __ 39 faulting near _ _ _ _ ___ _ __ _ _ _ _ _ _ _ _ __________ _ _ _ _ ___ _ __ _ __ _ __ _ _ _ _ _ _ _ _ _ _ ___ ___ 65 

surface undulations near _________________________ ~_______________________ 36 Traverse spur, description of. _______________________________________________ 27-29 

See also Escarpments. origin of _________________________________________________________________ 31-33 

Pisgah Ridge, description oL _______________________________________________ 59-60 piedmont scarp at ________________________ ~ ______________________________ 35-36 

Pleasant View spur, description oL __________________________ ~ ______________ 24-27 Twin Peak, features of. _ __ _ _ __ __ _ _ __ ____ ____ ___ _ _ _ __ _ _ _ _ ___ _ _ _ _ _ __ ___ _ _ __ _ _ _ 51 

escarpment opposite, plate showing______________________________________ 40 origin oL ________________________________________________________________ 31-33 

piedmont scarp at. ______________________________________________________ 35,36 

plate showing_ _ _________________________________________________________ 24 

Plum Ridge, Oreg., slickensides on, plate showing___________________________ 72 

Upper Klamath Lake, cliffs bordering_______________________________________ 76 

hills south of, plate showing_ ________ _ _ _ __ _ __ _ _ _ _ __ _ _ _ _ _ __ _ __ _ _ _ _ _ _ _ _ __ __ 80 

map of region about. ___ _ __ ___ _____ ___ _ _ __ _ __ _ _ _ _ ___ _ __ _ _ __ _ _ ___ _ _ _ _ _ __ _ _ 80 

ridges west oL __________________________________________________________ 83-84 

structure oC _____________________________________________________________ 76-80 Valleys, back, plates showing___________ __ _ __ __ __ _ _ ___ __ _ __ _ _ _ _ _ __ _ _ _ _ _ _ ___ _ _ 56 

Provo, Utah,.facets near, plates showing_____________________________________ 40 

fault phenomena near ___________________________________________________ 14-15 

piedmont scarps near______________________ ______________________________ 38 

Provo Canyon, faulting near ________________________________________________ 65-66 

plates showing _________ • ___________________ ~ ____________________________ 56,64 

Provo epoch, definition of. ________________________________ ,_ _ _ _ _ __ ___________ 12 

Provo shore line, plates showing _____________________________________________ 16,24 

Pseudo-anticline in Cambrian quartzite, plate showing______________________ 1'6 

processes producing ____________________________________________________ _ 

Wasatch Range, development oL ___________________________________________ 10-11 

east face of, plate showing ______________________________________ ' _ _ _ __ _ _ _ _ 56 

frontal fault of, dip oL__________________________________________________ 22 

nomenclature oL ____________________________________________________ 11-12 

outline oL ___________________________________________________________ 20-22 

physiographic evidence concerning __________________________________ 33-39 

throw oL ____________________________________________________________ 50-53 

f 

Rhodes Valley, description and origin oL___________________________________ 56 horst form of. _ ___ _ __ ___ _ _ _ _ _ __ _ __ __ ___ ____ __ _ ___ _ _ _ _ __ _ _ __ _ _ __ _ _ _ _ ___ _ __ 62 

Ribs of the Wasatch Range, truncation of. __________________________________ 40-41 location oL___ _ _ _ __ _ ___ __ _ _ _ _ _ ___ _ ___ _ _ _ _ _ __ __ _ _ _ _ _ _ _ ___ _ _ _ _ _ __ ___ _ __ _ _ __ 10 

Rock Canyon, Utah, details oC Cacet at, plate showing_______________________ 40 review of marginal faults in ______________________________________________ 67-69 

fault phenomena in _____________________________ ~ ________________________ 14-15 review of structure and history oL ______________________________________ 66-67 

Round Valley, Utah, history oL____________________________________________ 55 structure oC_____ ___ _ _ _ __ __ _ ____ _ _ _ __ _ _ _ _ _ __ _ _ __ _ _ __ _ _ _ __ _ _ __ _ __ _ ___ _ _ _ _ _ 10 

Russell, I. C" observationsoC, on lavas oC Oregon____________________________ 3 truncation of topographic and structural features oL ____________________ 40-41 

Salt Lake City, Utah, fault-block spur near ___________________________ 22-24,31-33 

Cault phenomena near ___________________________________________________ 15-16 

Sand Pass Ridge, features'oL_______________________________________________ 75 

Scarps. See Escarpments and Piedmont scarps. 

Shear zone, use of term _____ --_ -_ ------ __ ---- ---_ -_ ------ __ - _____ -__ ___ ______ 13 plates showing ________________________________ • _ ___ ___ __ ____ __ ___ ___ ____ 16 

interpretation oL ___________________________________________________ 41-47 

west face of, plates showing ______________________________________________ 16,56 

Weber Canyon, mouth of, plate showing____________________________________ 56 

Wheeler Survey report, cited_____ _ _ __ __ _ _ _ _ _ _ __ __ _ __ _ _ ___ _ _ _ _ _ __ _ __ _ _ __ _ _ _ _ _ 1-2 

Willard, Utah, fault phenomena near _____________________________________ 16,18-19 

fault phenomena near, plates showing___________________________________ 16 

Slickensides, indications from_ _ _ ____________________________________________ 13 Wasatch escarpment, opposite, plate showing___________________________ 40 plates showing _______________________________________________________ 16,72,80 Wind, erosive action oL_____________________________________________________ 68 

types of_ _ _______ __ _ __ __ _ __ ___ _ __ ____ _ _ ___ __ _ __ _ ____ _ ___ _ __ ___ __ _ _ ______ _ 13 Worthington Mountain, origin oL _________________________________________ _ 

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