Geologic setting and geomorphic analysis of quaternary fault scarps along the Deep Creek fault, Upper
Yellowstone Valley, south-central Montana
by Stephen Francis Personius
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Earth Sciences
Montana State University
© Copyright by Stephen Francis Personius (1982)
Abstract:
The Deep Creek fault represents the eastern-most major Basin and Range faulting in Montana. This
high angle normal fault forms the western flank of the Beartooth uplift and the eastern margin of the
upper Yellowstone (Paradise) Valley in southern Park County, Montana. Initiation of movement along
the Deep Creek fault may have begun as early as the Paleocene, in conjunction with uplift of the
Beartooth block. A northeast-trending mylonite shear zone along the eastern margin of the Yellowstone
Valley appears to have strongly controlled the geometry of the Deep Creek fault.
The fault trace is generally straight, but has several small bends and en echelon breaks.
The western flank of the Beartooth uplift exhibits the great relief common to other normal-fault bound
ranges in the western United States, but tectonic landforms (triangular facets in particular) common to
many of these ranges are poorly expressed along the mountain front. This relationship may best be
explained by the complex glacial history which has strongly affected the northern Yellowstone region,
and the resistant nature of the Precambrian crystalline rocks exposed in the footwall of the fault.
Geomorphic and statistical analysis of Quaternary fault scarps revealed three major periods of faulting
still preserved in the Yellowstone Valley. A well preserved group of scarps formed 10,000 to 12,000
years BP was preceded by two earlier periods of faulting; these scarps were formed approximately
30,000 to 50,000 years BP, and 100,000 to 200,000 years BP. The oldest scarps are preserved only in
the northern part of the valley, beyond the reach of late Pleistocene piedmont ice sheets. Fault scarps in
the upper Yellowstone Valley appear to. be the products of single fault movements, or closely spaced
multiple movements, separated by quiescent periods of much longer duration. Rate of displacement has
been approximately 200-300 m/million years since the early Pleistocene. GEOLOGIC SETTING AND GEOMORPHIC ANALYSIS OF QUATERNARY
FAULT SCARPS ALONG THE DEEP CREEK FAULT, UPPER
YELLOWSTONE VALLEY, SOUTH-CENTRAL MONTANA
by
Stephen Francis Personius
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Master of Science
V
'
in
Earth Sciences ■
MONTANA STATE UNIVERSITY
Bozeman, Montana
December 198.2
MAUN ufc-
M3 ^
PW 99
6cp" ^
ii
APPROVAL
of a thesis submitted by
Stephen Francis Personius
This thesis has been read by each member of the thesis
committee and has been found to be satisfactory regarding
content, English usage, format, citations, bibliographic
style, and consistency, and is ready for submission to the
College of Graduate Studies.
Date
Approved for thq Major Department
Hdad, Majbr Department
Date
Approved for the College of Graduate Studies
/2 - / 7
Date
f
G r a d u a t e Dean
i l l
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the
requirements for a master's degree at Montana State Univer­
sity, I agree that the Library shall make it available to
borrowers under rules of the Library. . Brief quotations.from
this thesis are allowable without special permission, pro­
vided that accurate acknowledgment of source is made.
Permission for extensive quotation from or reproduction
of this thesis may be granted by my major professor, or in
his/her absence, by the Director of Libraries when, in the
opinion of either, the proposed use of the material is for
scholarly purposes.
Any copying or use of the material in
this thesis for financial gain shall not be allowed without
my written permission.
Date
IV
V
ACKNOWLEDGMENTS
Great appreciation is extended to Dr. John Montagne
(Committee Chairman)
for sharing a part of his knowledge of
the Yellowstone Valley, Dr. Stephan G. Custer for critical
review of the thesis, and Dr. David R. Lageson for thesis
review and for initially suggesting the project to the
author.
Appreciation is, also extended to Dr. Kenneth L . Pierce
of the United States Geological Survey for his helpful sug­
gestions; Dave Redgrave for assistance in the field; Greg
Mohl and Dan Daugherty for help with drafting and photog­
raphy; Bruce Tremper for assistance with the statistical
analysis;'Eileen O'Rourke for ably handling the pilot duties
during the aerial photography flight; Louise Greene for
typing the final draft of the thesis; numerous landowners
for allowing access to their land in the Yellowstone Valley.
vi
TABLE OF CONTENTS
Page
1.
LIST OF ■TABLES. , . . ,.............................
2.
LIST OF FIGURES.................................. •
3.
LIST OF PLATES..... . ............................ .
%
4.
ABSTRACT....................................... . .
xii
5.
INTRODUCTION...... ................ '.............
I
Location. ...................................
.Purpose..................
Previous Investigations......................
I
I
3
6.
8.
5
5
5
7
STRUCTURAL SETTING..............................
8
Regional Structure...........................
Yellowstone Valley Structure................
Precambrian Structures..................
Laramide Structures.. ......... -..........
Basin and Range Structures..............
8
10
10
11
13
CENOZOIC HISTORY...................
16
Age of the Valley............. ■............ . .
Glaciation...................................
Pre-Bull Lake Glaciations...............
Bull Lake Glaciation.....................
Pinedale Glaciation......................
9.
ix
ROCK TYPES AND DISTRIBUTION..........
Precambrian Rocks.......................... . .
Paleozoic and Mesozoic Rocks................
Tertiary Igneous Rocks.............
7.
vii
FAULT GEOMORPHOLOGY..............
Fault
Range
Fault
Fault
16
19
19
21
22
. . . ;.........
24
Geometry................................
Front Geomorphology................
Scarp Distribution....................
Scarp Formation and Modification.....
24
25
28
29
vii
TABLE OF CONTENTS— Continued
Page
10.
FAULT SCARP ANALYSIS..........................
Field Relationships............
Methods.................................
Relative-Age Relationships............
Youngest Event..........
Intermediate Event......
Oldest Event............
Scarp Profile Analysis..................... •
Profile Measurement Techniques . .......
Analysis Methods...........
Deep Creek Results...................... .
Technique Limitations........... ■......
Regression Analysis Results...........
History of Movement.........
Nature of Movement.....................
Rates of Movement......................
Distribution. ...........................
35
35
35
35
35
43
46
46
46
48
50
: 50
51
n56
56
57
57
11.
SUMMARY AND CONCLUSIONS.......................
59
12.
REFERENCES CITED............. '................
61
13.
APPENDICES. ...... . :........- ...... .......
.69
..
Appendix A
Fault Scarp Profile Dat a ..........
Appendix B
Location Maps of Measured Profiles....
70
74
viii
LIST OF TABLES
Table
I.
Statistical analysis of Deep Creek fault
scarp profile da t a ....................
ix '
LIST OF FIGURES
Figure
1.
2.
Page
Map showing the outline of the Upper Yellow­
stone Valley, trace of the Deep Creek and
Luccock Park, faults, a n d .locations of Quater­
nary fault scarps.....................
2
General geologic map of the upper Yellowstone
Valley, south-central Montana.................
.6
3.
Regional structure map of south-central Montana
4.
Photographs of basal grabens preserved along
the Deep Creek fault...........................
31
Diagram illustrating the erosional modifica­
tion of a normal fault scarp..................
34
Photograph of G r a y 1s Ranch scarp, view looking
north.........•.................................
37
Diagrams describing details of the G r a y 1s
Ranch scarp graben............................
40
Photograph of several scarps in Barney Creek
area............................................
41
Oblique aerial photograph of Barney Creek
scarps, view looking northeast...............
41
10.
Photographs.of the Pool Creek scarp. .........
44
11.
Photograph of Strong’s Ranch scarp, exposed
.in center of photo............................
47
12.
Diagram of a typical normal fault scarp.....
49
13.
Histograms of principal slope angles of
selected Deep Creek fault scarps...........
52
Regression data from principal slope angle and
scarp height measurements of Deep Creek fault
scarps
54
5.
6.
7.
8.
9.
14.
9
X
LIST OF PLATES
Plate
I.
t
Page
Surficial geologic map of east side of
upper Yellowstone Valley, Montana.......... (in pocket)
xi
ABSTRACT
The Deep Creek fault represents the eastern-most major
Basin and Range faulting in Montana.
This high angle normal
fault forms the western flank of the Beartooth uplift and
the eastern margin of the upper Yellowstone (Paradise) Val­
ley in southern Park County, Montana. Initiation of move­
ment along the Deep Creek fault may have begun as early as
the Paleogene, in conjunction with uplift of the Beartooth
block.
A northeast-trending myIonite shear zone along the
eastern margin of the Yellowstone Valley.appears to have
strongly controlled the geometry of the Deep Creek fault.
The fault trace is generally straight, but has several small
bends and en echelon breaks.
The western flank of the Beartooth uplift exhibits the
great relief common to other normal-fault bound ranges in
the western United States, but tectonic landforms (triangu­
lar facets in particular) common to many of these ranges are
poorly expressed along the mountain front. This relationship
may best be explained by the complex glacial history which
has strongly affected the northern Yellowstone region, and
the resistant nature of the Precambrian crystalline rocks
exposed in the footwall of the fault.
Geomorphic and statistical analysis of Quaternary fault
scarps revealed three major periods of faulting still pre­
served in the Yellowstone Valley.
A well preserved group of
scarps formed 10,000 to 12,000 yearh BP was preceded by two
earlier periods of faulting; these scarps were formed approx­
imately 30,000 to 50,000 years BP, and 100,000 to 200,000
years BP.
The oldest scarps are preserved only in the north­
ern part of the valley, beyond the reach of late Pleistocene
piedmont ice sheets.
Fault scarps in the upper Yellowstone
Valley appear to. be the products of single fault movements,
or closely spaced multiple movements, separated by quiescent
periods of much longer duration.
Rate of displacement has
been approximately 200-300 m/million years since the early
Pleistocene.
I
INTRODUCTION
Location
The Deep Creek fault bounds the western edge of the
Beartooth uplift and forms the eastern margin of the upper
Yellowstone
I)..
(Paradise) Valley in south-central Montana (Fig.
This high-angle normal fault trends northeast for
approximately 55 km and structurally separates the Gallatin
and Beartooth Laramide foreland uplifts.
The fault trace is
characterized by sporadic Quaternary fault scarps, and is .
elsewhere buried by surficial debris or inferred by the
presence of faceted spurs and other tectonic landforms.
Purpose
The topography of south-central and southwest Montana
is dominated by mountain ranges which are commonly bound by
steeply-dipping normal faults.
These northwest-to northeast
trending structures characterize the extensional Basin and
Range deformation which has occurred in this region since
Middle
(and possibly earlier) Tertiary time.
faults
(including the Deep Creek)
day (Reynolds, 1979).
Many of these
are considered active to­
The purpose of this study is to de­
scribe the tectonic geomorphology of the eastern margin of
the upper Yellowstone Valley, and in particular, the
2
LIVINGSTON
MONTANA
Bozeman*
Livingston
^-upper Yellowstone V
IDAHO
SCARPS REFERRED TO
IN T E X T :
0
Strongs Ranch
0
Pool C reek
0 Borney Creek
@ Counfs Ranch
LUCCOCK PARK
FAULT
(S)Groys Ranch
(S)EIbow C re e k
HOT SPRINGS
W HITE
C L IF F S
FAULT
EMIGRANT
a PEAK
MILES
LEG END
DOME MOUNTAIN
N orm al fa u lt, dashed
where in fe rr e d . Bor an
boll on downthrown side.
Q uaternary
fault scarp.
Figure I. Map showing the outline of the Upper Yellowstone
Valley, trace of the Deep Creek and Luccock Park faults, and
locations of Quaternary fault scarps.
Compiled from Reid
and others (1975, Fig. I), Montagne and Chadwick (1982, Fig.
2), and mapping by the author.
3
geomorphic expression of the Quarternary fault scarps found
along the trace of the Deep Creek fault.
This data will
then be applied to an interpretation of the history of Quat­
ernary movement along the fault.
This interpretation will
include the age of fault scarps present in the Yellowstone
Valley, recurrence intervals of major faulting, and rate of
fault displacement during the Pleistocene.
The regional
geological setting will initially be developed to explain
the relationship between Quaternary features and the struc­
tural setting of south-central and southwest Montana.
Previous Investigations
Geologic investigations in the upper Yellowstone Valley
date to the late 1800's, when the Hayden Survey followed, the
Yellowstone River into what is now Yellowstone National Park.
.Publications from this era (Hayden, 1872a, 1872b; Weed, 1893;
Iddings and Weed, 1894) are remarkable, especially consider­
ing the reconnaissance nature of these investigations.
<
'
'
The 1930's and 1940's marked a resurgence of investiga­
tions in the area, principally by geology students from
Princeton University.
geology
Excellent studies of the structural
(Wilson, C.W., 1934, 1936; Wilson, J.T.,
mers, 1937; Skeels, 1939) and geomorphology
1936; ham­
(fiorberg, 1940)
of the region were published during this period.
. From the post-war period to the present, investigations
of the surrounding Beartooth and Gallatin Ranges were
4
published
(Foose and others, 1961; McMannis and Chadwick,
1964; Chadwick,
1969; Reid and others,
1975).
The U .S .
Geological Survey was active throughout this period, with
major studies conducted on the general geology of the region
(Richards, 1957; Roberts,
Ruppel, 1972).
1972; Fraser and others,
Bonini and others
1969;
(1972) conducted a gravity
survey of the region, which has given major insight into the
surface configuration of the Yellowstone Valley.
Several
Masters and Ph.D. theses have also made contributions to the
geology of the region
(Van Voast,• 1964; Easier, 1965; Bush,
1967; Struhsacker, 1976; Erslev, 1981).
The author has
recently published a shorter version of this thesis
(Per-
sonius, 1982).
The most comprehensive investigations of the glacial
and geomorphic aspects of the valley have been conducted by
John Montagne of Montana State University
Chadwick,
(Montagne and
1982) and Kenneth Pierce of the U .S . Geological
Survey (Pierce, 1979).
These works represent the "state of
the geologic art" in the upper Yellowstone Valley.
5
ROCK TYPES AND DISTRIBUTION
Precambrian Rocks
Both the Gallatin and Beartooth Ranges are Precambriancored foreland uplifts, characterized by highly metamor­
phosed crystalline rocks of Archean age
1961; McMannis and Chadwick,
(Foose and others,
1964; Reid and others,
1975).
Movement along the Deep Creek fault has elevated the Beartooth Range structurally higher than the Gallatin Range, and
subsequently more Precambrian rocks have been exposed there
by erosion
(Fig. 2.) .
The Precambrian rocks are very heter­
ogeneous, and represent metamorphosed equivalents of sedi­
mentary rocks deposited very early in the history of the
earth
(Reid and others,
1975).
Paleozoic and Mesozoic Rocks
The Paleozoic-Mesozoic sedimentary package representing
shelf sedimentation is preserved in several remnants atop
the Beartooth and Gallatin Ranges
(Fig. 2).
The narrow por­
tal forming the northern entrance to the Yellowstone Valley
south of Livingston, Montana, is cut through a complex of
these rocks ramped onto the northern flanks of the Beartooth
and Gallatin Ranges by the Suce Creek thrust system.
These
represent the best exposures of t h e .section in the valley..
6
?
LEGEND
S 3
--
High angle F a ult, bar and ball on
u
—
downthrow n sid e , daehed
where Interred
Q u a te rn a ry fa u lt scarp
Thruet F a u lt,te e th on upthrow n
- -
s tr ik e - a llp F a ult, dashed where
aide,dashed w here Inferred
In fe rre d
-
A nticlin e fo ld a x is ,w ith d ire ctio n
o f plunge
Cenozolc sed im enta ry rocks
E S 3
T e rtia ry Igneous ro cks
R a le o z o lc -M e e o z o lc ro cks
FV*V*«’V * ^ •*••<"••
t/g€ J
r . X:/'\:"
_____
P recam brlan ro c k s
Figure 2. General geologic map of the upper Yellowstone
Valley, soiith-central Montana.
Compiled from Foose and
others (1961, Plate I), Reid and others (1975, Fig. I).
Montagne and Chadwick (1982, Fig. 2), and mapping by the
author.
I
Other small outcrops are found in the low hills between Suce
and Deep Creeks, in the area just south of Mill Creek, and
as small scattered remnants on the valley floor.
Tertiary Igneous Rocks
Eocene volcanic rocks were erupted in two northwesttrending belts across the southern portion of the Yellow­
stone Valley area
(Chadwick,
1970).
Based on their regional
extent, these belts probably represent zones of weakness
within the basement ,(Chadwick, 19 81; Garihan and others,
1982) , and appear to be continuous with the. Squaw Creek
fault to the north and the Spanish Peaks fault to the south
(Fig. 2).
intermediate compositions dominate within this
sequence; the dominant andesitic lava flows and breccias
have been locally intruded by dacitic to rhyodacitic plugs,
stocks, and dikes.
Two principal sequences are evident.
The older, more restricted sequence is known as the Golmeyer
Creek Volcanics; it is overlain by the more widespread Hya­
lite Peak Volcanics
(Montagne and Chadwick, 1982) .
These
rocks range in age from 48 to 53 MY, and apparently corre­
late with the Washburn Group of the Absaroka Volcanic Super­
group
(Smedes and Prostka, 1972) .
8
STRUCTURAL SETTING
■
'
.
Regional Structure
The Deep Creek fault represents the easternmost expres­
sion of the Basin and Range structural province in Montana
(Fig. 3).
Although at least one author disagrees
(RuppeI ,
1982), most workers-believe that normal faults formed by
east-west directed crustal extension were superimposed on.a
structural terrane formed during the Sevier and Laramide
orogenies
(Reynolds, 1979) .
This pre-existing landscape was
characterized by broad uplifts and basins of low relief
(Thompson and others,
1981).
North-northeast and north-northwest trending range
front faults dominate the Basin and Range structural defor­
mation in western Montana.
These trends may reflect struc­
tural anisotropies in the underlying Precambrian basement,
upon which the east-west extensional stress regime has been
superimposed.
A major exception is the east-west trending
Centennial fault (Fig. 3) which may be controlled by norths
south extension associated with the Snake River Plain (Hamil­
ton and Meyers,
1966; Trimble and Smith,
19 75)' .
Laramide structures generally trend west to northwest,
which implies compressional stress aligned in a northeastsouthwest direction.
The bounding reverse faults of the
___Montana _
Wyoming
LEGEND
N orm al F a u lt, b a r and b a ll on d o w n th ro w n aide
R o vera e F a u lt, te e th
YELLOWSTONE
NATIONAL
PARK
SfiNIfNNIi
~~h~
r^Ssiena— ,
1
Figure 3.
Plate 3).
Idaho
on upth ro w n aide
S tr lk e - e llp Fault
SyocUne fo ld axle
,
r-
N
Regional structure map of south-central Montana.
After Roberts
(1975
10
Beartooth uplift, and the trend of the Crazy Mountains Basin
also display this pattern.
As with Basin and Range deforma­
tion, pre-existing basement weaknesses may have had a major
influence on the geometry of these structures.
One such
weakness is the Nye-Bowler lineament, which traverses eastwest along the northern front of the Beartooth uplift.
Wilson
C.W.
(1936) postulated left-lateral strike-slip movement
on this fault zone to explain the en echelon patterns of
northwest-striking folds and northeast-striking normal faults
found along this structure.
Certainly more work needs to be
done to explain the relationship between these basement
weaknesses and later deformation.
Yellowstone Valley Structure
The strong relationship that appears to exist between
structures of Laramide and Basin and Range style with weak­
nesses in the Precambrian basement elsewhere in Montana is
also evident in the upper Yellowstone Valley.
Therefore a~~l
discussion of known Precambrian structures is important to (•
understanding the local structural setting.
Precambrian Structures
The Precambrian geology of the west flank of the Beartooth uplift has been studied in some detail
others, 1975; Burnham,
19.82; Erslev,
(Reid and
1982) ; these studies
have revealed several dominant structural trends
(Fig. 2):
11
I) a northeast-striking foliation trend, 2) major west-to
northwest-trending strike-slip faults, 3) several northnortheast- trending strike-slip faults, and 4) a major northeast- trending mylonite shear zone coincident with the trace
of the Deep Creek fault.
Laramide Structures
The previously discussed Precambrian weaknesses appear
to have controlled much of the structural deformation asso­
ciated with the Laramide orogeny, especially within the
Beartooth block itself
others, 1975) .
(Foose and others,
1961; Reid and
West-northwest-trending folds and low-to
high-angle reverse faults characterize the. Laramide struc­
tural features in the upper Yellowstone Valley area
(Fig. 2).
To the south, the Gardiner fault forms the southwestern
flank of the Beartooth uplift, and may project westward
across the southern portion of the valley (Fig. 2)
and Chadwick,
1982) .
(Montagne
This north-dipping high-angle reverse
fault is believed to be part of the Spanish Peaks-North
Meadow Creek-Bismark fault system which trends to the north­
west as far as the Tobacco Root Mountains
wick, 1970; Schmidt and Hendrix,
1982).
Several authors
(Johnson,
(Reid, 1957; Chad­
1981; Garihan and others,
1934; Foose and others,
1961) have speculated that the Gardiner fault plunges be­
neath the Tertiary volcanic cover to the southeast and even­
tual Iy emerges as the Rattlesnake Mountain fault near Cody,
I
12
Wyoming.
Another hypothesis is that the Gardiner fault con­
nects with the north-trending Buffalo Fork thrust in central
Yellowstone National Park (RuppeI , 1972).
Little subsurface
evidence exists to prove or disprove these hypotheses.
The Mill Creek and Elbow Creek fault zones of J.T. Wil­
son (1936) enter the east side of the upper Yellowstone
Valley near the mouths of Mill and Elbow Creeks
(Fig. 2).
These north-dipping, high-angle faults show reverse movement
(both down to the south) and have b e e n .superimposed on pre­
existing strike-slip fa'ults of Precambrian ancestry (Reid
and others, 1975).
J.T. Wilson
(1936) believed.these faults
extend to the northeast as the Stillwater-Bluebird faults,
although the eastward termination is subject to conjecture
(Foose and others, 1961; Reid and others, 1975).
A complex group of Laramide structures forms the north­
ern margin of the upper Yellowstone Valley
(Fig. 2).
The
Yellowstone River has cut a gorge through the hanging wall
of the Suce Creek thrust, one of several north-dipping re­
verse and thrust faults which displace Precambrian, Paleozoic,
and Mesozoic rocks onto the northern flanks of the Gallatin;
and Beartooth Ranges.
Associated with these faults are an
en echelon series of northwest-plunging folds that continue
northward to the Bozeman area.
The trend of these folds
parallels the fold trend of the Nye Bowler lineament to the
east, and may represent a northwest continuation of this
fault zone
(Wilson, C.W., 1936; Roberts,
1972).
This thrust
13
complex may be an example of "out of the basin" crowding,
associated with downwarping of the Crazy Mountains Basin to
the north.
A series of klippen consisting of Paleozoic rocks rest­
ing on Mesozoic strata are located just, south of the Suce
Creek thrust trace on the west side of the valley
1964).
(Roberts,
These features may have been emplaced by gravity
sliding off the topographic and structural high created by
the Suce Creek thrust
(Skeels, 1939; Foose and others, 1961).
Several of these smaller blocks are found out on the valley?
floor, and have been partially buried by alluvium.
Basin and Range Structures
The Deep Creek fault is the dominant Basin and Range
structure in the Yellowstone Valley region.
Directly to the
east, the northeast-trending Luccock Park fault constitutes
a sympathetic step fault between the Deep Creek fault and
the uplifted Beartooth block
(Fig. 2).
These faults bound ■
an uplifted block of Precambrian rock known as the Short
Hills; relief between the present valley floor and the top
of the Short Hills block is approximately 500 m.
A minor
step fault within the Short Hills block is exposed within
the canyon of Cascade Creek, 0.5 km east of the Deep Creek
fault trace
(Fig. I, Plate I).
A small remnant of Miocene
(?) sedimentary rock is preserved in the hanging wall of
this fault (Montagne and C h a d w i c k , 1982).
The Short Hills
14
block is probably broken by other smaI!-displacement fault
slivers of this type.
Tertiary dip-slip displacement is apparent on the Luccock Park fault; the trace is marked by a prominent break
in slope, and remnants of Miocene (?) sedimentary rocks are .
preserved on the Short Hills block, but not on the footwall
of the Luccock Park fault.
The author found no evidence of
near-recent movement along the trace of this fault.
The general northeast trend expressed by all the normal
faults along the eastern side of the upper Yellowstone Val­
ley appears to continue northward beyond the confines of the
valley in a series of short, en echelon normal faults shown
on Roberts’ (1972) tectonic map of the Crazy Mountains Basin
region.
Sufficient evidence exists to suggest that the Deep .
Creek and associated faults have been superimposed on pre­
existing structural features.
Reid and others
(1975) mapped
the Luccock Park fault as a normal fault superimposed on a
strike-slip fault of Precambrian ancestry.
mylonite shear zone mapped by Erslev
Certainly the ■■
(1982) and Burnham
(1982) in this region had an influence on later normal fault
ing.
This northeast-trending, northwest-dipping shear zone
of probable Proterozoic age was mapped discontinuousIy along
the eastern side of the upper Yellowstone Valley.
The Deep
Creek fault trend directly follows this shear zone wherever
it is exposed.
Erslev suggested that foliation planes of
15
the mylonite zone were exploited by the Deep Creek fault,
and that the change in trend
(from northeast to north-north­
east) of the mylonite zone in the Mill Creek area can be
attributed to left-lateral strike-slip movement on the Mill
Creek fault
(Fig. 2).
As with the previously described
Laramide structural features, pre-existing weaknesses appear
to have strongly controlled the distribution of Basin and
Range structures in the upper Yellowstone Valley.
The lack of any clear linear trends, springs or faceted
spurs suggests that there is no major bounding fault on the
west side of the valley.
Therefore the upper Yellowstone
Valley is considered a half graben../Structures on the west
side of the valley generally plunge eastward in response to
movement along the Deep Creek fault *
Other north and northeast-trending normal faults extend
northward from the Yellowstone Plateau area into the southern
margin of the Beartooth uplift
pel, 1972; Struhsacker, 1976).
(Foose and others,
1961; Rup-
They appear to truncate the.
the Laramide structural features in the area.
■ •
CENOZOIC HISTORY
Age of the Valley
The exact timing of movement along the Deep Creek fault
and subsequent formation of the Yellowstone Valley, is open
to conjecture.
Uplift of the Beartooth block occurred in
Paleocene time, although the topographic relief of the area
was created by regional uplift and subsequent erosion since
I
the Miocene (Foose and others, 1961).
The apparent trunca­
tion of the Deep Creek fault by th,e Suce Creek thrust led
Richards
(1957) to infer that tensional forces pre-dated the
final compressional events during uplift of the Beartooth
block.
Most published maps of the area
1961; Roberts,
1964; Reid and others,
(Foose and others,
1975) agree that the
Deep Creek fault is truncated by the Suce Creek thrust.
Studies of the Eocene volcanic rocks in the Gallatin
Range by McMannis and Chadwick
(1964) and Chadwick
(1969)
have also given indications of an early Tertiary date for
initiation of faulting.
-The earliest Eocene volcanic rocks
(Golmeyer Creek Volcanics) dip 10° eastward toward the Yel­
lowstone Valley, whereas the upper units of this same
sequence are nearly horizontal.
This relationship implies
that the region was tilted to the east at the time of vol­
canic activity, possibly in response to movement oh the Deep
17
Creek fault.
Detailed examination of the fluvial and mud­
flow facies of these volcanics also indicated that prevolcanic drainage was to the east.
These observations at
least point to a topographic low to the east in the vicinity
of the upper Yellowstone Valley.
The main phase of Basin and Range extensional deforma­
tion is believed to have begun during the middle Miocene, as
evidenced by the presence of the middle Miocene unconformity
in t h e ■intermontane basins of southwest Montana
(Rasmussen,
1973; Reynolds, 1979; Thompson and others, 1981).
In most
basins, late Miocene and younger sedimentary rocks rest unconformably on Oligocene and early Miocene sedimentary rocks;
middle Miocene age rocks are rare or missing.
The best Tertiary sedimentary rock exposures in the
upper Yellowstone Valley can be seen in the White Cliffs,
area in the southern part of the valley (Fig. I) .
Here a
flat-lying 5.4 MY basalt overlies a flat-lying Late Miocene
gravel, which contains fragments of an 8.4 MY basalt. ' This
graveI in turn overlies a middle Miocene
1980)
(17.1 MY) (Hughes,
sequence of tuffaceous sandstone, siltstone, and clay-
stone which is dipping to the east at 8-10° in response to
movement on the Deep Creek fault.
The base of this exposure
is covered, so the underlying rocks cannot be identified.
No Oligocene rocks have been identified in the valley.
The
existence of this middle and late Miocene sequence implies
that initiation of movement along the Deep.Creek fault
18
occurred at least in pre-Miocene time, in order for these
fluvial and lacustrine sediments to be trapped in the valley.
Other tuffaceous sediments very similar to the White
Cliffs rocks have been identified on top of the Short Hills
block
(Montagne and Chadwick, 1982) over 300 m above the
present valley floor..
If these rocks are also middle Mio­
cene in age, then either a very thick sequence of Miocene
rocks was deposited and subsequently eroded in the valley,
or uplift along the Deep Creek and Luccock Park faults has
carried these rocks to a position much higher than at the
time of deposition
(Montagne and Chadwick,
1982).
The lack
of thick Miocene exposures elsewhere in the valley, and
evidence to be discussed in a later section on the glacia­
tion of the valley, point to uplift as the reason for the
high level occurrence of Miocene rocks on the Short Hills
block.
The previously presented evidence from the sedimentary
record in the Yellowstone Valley again points to tensional
movements along the Deep Creek fault which pre-date the mid­
dle Miocene date assigned to most Basin and Range faults in
southwestern Montana.
From evidence to date, an early Ter­
tiary initiation, perhaps in the late Paleocene, seems rea­
sonable.
The presence of a northeast-trending mylonite
shear zone coincident with the trend of the Deep Creek fault
(Erslev, 1982) may help explain tensional faulting during or
closely following the compressional stresses which
19
characterized the Laramide orogeny.
Therefore the Deep
Creek fault appears to have undergone a very long period of
tensio.nal, dip-slip displacement, which has continued inter­
mittently to near-recent time.
Glaciation
The upper Yellowstone Valley has undergone a complex
history of glaciation during the Pleistocene.
Deposits cor­
related with Pinedale, Bull L a k e , and Pre-Bull Lake glacia­
tions have been identified in the valley
1979; Montagne and Chadwick,
1982).
(Plate I ) (Pierce,
Dating of near-recent
movements of the Deep Creek fault are greatly aided by
cross-cutting relationships with these deposits.
Pre-Bull Lake Glaciations
Sheet-like till deposits which do not show morainal
form were first observed in.the Yellowstone Valley by Horberg
(1940) .
John Montagne
(Montagne and Chadwick,
1982)
has studied these deposits extensively, and believes they
represent deposits from one or more pre-Bull Lake piedmont
ice sheets that flowed down the Yellowstone Valley off the.
Yellowstone Plateau.
These ice sheets are believed to have
been much larger than the Pinedale piedmont ice sheet.
reasoning is based on the following evidence:
His
I) the de­
posits are found well beyond.the terminal position of the
Pinedale trimline in several places in. the valley, 2) the
deposits do not show morainal morphology, and 3) volcanic
erratics have been found as far north as Pine Creek, which
must have originated south of Mill Creek, implying downvalley ice movement.
Large, early Pleistocene glaciers similar to the Yel­
lowstone Valley sheet have been postulated for other local
areas; the Madison Range to the west has clear evidence for
a huge sheet
(Hall, 1960a; Walsh,
Hole area in Wyoming
Love, 1968) .
1975) as does the Jackson
(Blackwelder, 1915; Fryxell, 1930;
One of the Madison Range tills lies beneath
the 1.9 MY old Huckleberry Ridge. Tuff, and therefore hasbeen assigned a very early Pleistocene date
Chadwick,
(Montagne and
1982).
Some of the pre-Bull Lake erratics have been found on
top of the Short Hills block, 500 m above the valley floor
(Horberg,
1940; Montagne and Chadwick,
1982).
This relation­
ship is complicated by the lack of unequivocal, correspond­
ing deposits at that level on the west side of the valley.
Unless drastic changes in ice thickness are called upon, it
seems likely that these deposits have been carried up to
their present position by faulting along the Deep Creek and
Luccock Park faults.
If true, this may represent as much as
200-300 m of displacement along these faults since the early
Pleistocene.
21
Bull Lake Glaciation
Many valley-glacier moraine sequences in the Rocky
Mountains have been correlated with Blackwelder's (1915)
original descriptions of Bull Lake and Pinedale glacial de­
posits.
These correlations are based on:
I) relative posi­
tion- Bull Lake moraines are usually outside of or downvalley from Pinedale moraines, and 2). Bull Lake moraines
usually show a much subdued topographic expression when com­
pared to Pinedale moraines.
These conditions fit fairly
well for. the Bull Lake deposits identified in the upper Yel­
lowstone Valley, which are restricted to canyon-mouth posi­
tions at Elbow, Strawberry, Pine, and Deep Creeks
1979; Montagne and Chadwick, 1982).
(Pierce,
No piedmont Bull Lake
moraines have been identified on.the valley floor; this
relationship is opposite that in the West Yelllowstone basin
to the southwest.
Here the Bull Lake piedmont deposits are
very large, and occur down-valley from the much smaller
Pinedale deposits
(Richmond, 1964; Pierce,
1979).
Pierce
(1979) proposed that the escape route used by the Bull Lake •
ice sheet off the Yellowstone Plateau was later blocked by
deposition of rhyolite flows, and that the subsequent Pinedale ice sheet was deflected to the north and down the Yel­
lowstone Valley.
were
Any Bull Lake deposits on the valley floor
then overridden and obliterated by the much larger
Pinedale piedmont sheet.
22
It is generally believed that the Bull Lake glaciation
occurred between 127,000 and 170,000 years BP.
hydration techniques
Obsidian
(Pierce and others, 1976) have been
used to obtain a date of the Bull Lake moraines near West
Yellowstone of about 140,000 years BP, with ages ranging
from 130,000 to 155,000 years BP.
These dates correlate
with a late Illinoian age in the midcontinent.
Although no
age dates on the Yellowstone.Valley moraines have been ob­
tained, the author believes these moraines correlate closely
with those in the West Yellowstone area.
Pinedale Glaciation
Pinedale-age deposits are extensively preserved in the
upper Yellowstone Valley, both at canyon-mouth positions and
on the valley floor as deposits of the northern Yellowstone
piedmont sheet.
At least two still-stands during Pinedale
time are represented by the Chico and Eightmile piedmont
terminal moraines on the floor of the Yellowstone Valley
west of Mill Creek
1982).
(Pierce, 1979; Montagne and Chadwick,
This relationship is not clearly seen in the canyon-
mouth moraines, which may reflect the differences in source
areas of these two distinct types of glaciers that invaded
the Yellowstone Valley.
Canyon-mouth moraines are preserved
only beyond the piedmont ice limit north of Mill Creek; all
other glacial debris was. swept down-glacier by the piedmont
sheet.
Apparently the valley glaciers melted faster than
23
the piedmont sheet, because glacial lake sediments of Pinedale age are found in the canyons of Sixmile and Emigrant
creeks
(Plate I)(Montagne and Chadwick,
Miner Basin
(Pierce, 1979).
1982) and in Tom
The piedmont ice must have
acted as an ice dam at the mouths of these valleys, behind
which lakes were impounded.
The Pinedale Glaciation is usually dated from approxi­
mately 75,000 to 15,000 years BP, with deglaciation essen­
tially complete by 11,000 years BP.
Obsidian-hydration dat­
ing of the West Yellowstone Pinedale moraines yielded dates
of about 30,000 years BP, with ages ranging from 20,000 to
35,000 years BP
(Pierce and others,
1976).
The author again
believes these moraine dates can be used with some confid­
ence in the upper Yellowstone Valley, although the valley
glacier deposits.(especially those related to deglaciation)
are probably somewhat older than the piedmont deposits.
The
Pinedale Glaciation correlates with most of the Wisconsinan
of the midcontinent.
24
FAULT GEOMORPHOLOGY
Fault Geometry
The trace of the Deep Creek fault is generally quite
straight, but close examination reveals that the fault shows
several small-scale changes in geometry along its trace.
echelon breaks', bends, and splits or steps are present
En
(Fig.
I, 2, Plate I), which are elements commonly expressed by
other normal faults in the Basin and Range Province
son, 1977).
(Ander­
Most other normal faults in southwest Montana
have geometries similar to the-Deep Creek fault, although
the. various styles vary widely in scale.
For instance, the
faults bounding the Bridger and.Madison ranges in southwest.
Montana have larger
Deep Creek trace.
scale bends than those seen along the
As mentioned previously, the Precambrian ■
basement rocks probably exert strong controls on the geom- .
etry of all these Basin and Range faults.
The dip of the Deep Creek fault is open to some specu­
lation.
Pardee
(1950) described an excavated portion of the
fault near Yankee Jim Canyon, in which a 50° dip was meas­
ured.
Bonini and others
(1972) used a vertical dip to arrive
at a best fit for their gravity data.
The author has used a
Brunton compass to measure a 60° west dip, using the atti­
tude of the trace of a fault scarp exposed in an incised
25
canyon 4 km northeast of Sixmile Creek.
Recent Basin and
Range structural studies such' as that of, Proffett
(1977)
have determined that many range front normal faults are
actually listric in shape; these faults are at high angles
(60° or greater)
depth.
at the surface, but flatten gradually with
Seismic or deep drilling data will be required to
accurately determine the subsurface geometry of the Deep
Creek fault.
The gravity survey of Bonini and others
(1972) gives
the best indication of the magnitude of throw on the Deep
Creek fault.
Maximum displacement appears to be in the
Chico area, with as much as 6,000 m of possible offset.
presence of an outcrop of Flathead Sandstone
The
(Cambrian) near
Pine Creek on the hanging wall of the fault suggests a miniI
.
mum of 1,500 m of throw.
The general trend appears to be a
decrease in displacement both north and south of the maximum
in the Chico area.
Range Front Geomorphology
The west flank of the Beartooth uplift exhibits the
rugged topography, great relief, and other geomorphic char-?
acteristics common to normal-fault bound ranges in 'the wes­
tern United States.
Streams draining from this highland
into the Yellowstone Valley are deeply incised and have steep
gradients, even where modified by glaciation.
Foothills are
absent, except where step faulting has created intermediate
blocks between, the valley bottom and the range, front.
How­
ever, very few examples of faceted spurs are present In the ■
upper Yellowstone Valley.
This is unusual, because these
landforms are one of the most common features found along
normal-fault bound range fronts.
Detailed studies of the
development of faceted spurs, and associated remnant pedi­
ments have been conducted in other parts of the Basin and
Range Province, in particular along the Wasatch fault zone
in northern and central Utah (Hamblin, 1976; Anderson, 1977;
Osborne,
1978).
These landforms are the geomorphic expres­
sion of recurrent uplift; it is widely believed that dis­
placement on most normal faults occurs intermittently, with
active periods of displacement separated by periods of quies­
cence of varying duration.
Fault scarps and the faceted
spurs developed from them are the result of active displace­
ment and minor erosion between events.
Remnant pediments
are narrow erosion surfaces formed by backwasting of the
mountain front during quiescent periods, with subsequent
erosion and modification during the next phase of uplift.
These relationships are not well expressed along the
Deep Creek fault.
Faceted spurs are preserved locally, but
remnant pediments cannot be identified with any certainty
along the mountain front.
There are several possible explanations for the absence
or poor development of faceted spurs and pediments along the
Deep Creek fault.
I) Glaciation has greatly modified the
27
mountain front in many places.
huge,
The probable existence of a
pre-IIIinoian• ice sheet in the upper Yellowstone Val­
ley (Montagne and Chadwick,
1982), may have severely altered
any tectonic features along the mountain front.
This dis-
1
ruption was compounded in the southern part of the valley
by the presence of a smaller Pinedale piedmont ice- lobe.
2) The Precambrian crystalline rocks exposed in the footwall
may be less susceptible to. spur and pediment formation than
the Paleozoic-Mesozoic sedimentary rocks exposed along other
range fronts, such as the Wasatch Front.
Osborne
(1978)
observed that spur and pediment development was very subdued
in areas where resistant units like the Tintic Quartzite
were exposed along the Wasatch fault; this may be analogous
to the resistant Precambrian rocks found in the Beartooth
uplift.
Lithologic resistance may also explain the lack of
development along the fault-bound Teton Range in northwest.
Wyoming, which is also characterized by resistant Precambrian crystalline rocks.
characterized by recurrent
3) The Deep Creek fault may not be
(intermittent)
uplift.
If fault
displacement has been more or. less continuous, the resultant
range front geomorphology should be more uniform than that
expected from recurrent uplift.
A combination of glacial
erosion and lithologic resistance may best explain the lack
of spur and pediment development along the Deep Creek fault.
28
Fault Scarp Distribution
Some of the most interesting geomorphic expressions of
the Deep Creek fault are the Quaternary fault scarps that
occur at or near the base of the range front in several
places along.the fault trace.
As used in this report, these
features are surface scarps in which surface offset is still
evident.
They occur intermittently, and vary considerably
in distance from.the mountain front.
Scarps of similar age
vary from a position 600 m valleyward from the range front,
to being coincident with the range front.
Glacial erosion
of the mountain front hcis certainly occurred in those parts
of the valley affected by piedmont ice (Mohtagne and Chad­
wick, 1982), but the magnitude of this erosion is open to
question.
The mountain front along the foot of Dome Mountain
(Fig. I) in the southern part of the valley appears to have
been severely eroded by Pinedale and probably earlier pied­
mont ice sheets.
The most recent fault scarps located along
this area post-date the last glaciation and are located from
fifty to several hundred meters from the range front.
The
former figure may represent a minimum value of erosional re­
treat, if it is assumed that the fault zone and range front
were coincident prior to glaciation.
Glacial erosion appears
to have played a major role in forming the present relation­
ship between fault scarp distribution and location of the
mountain front.
Fault:scarp segment lengths range from several hundred
meters, to over six kilometers.
The shorter segments are
29
found either where the trace breaks en echelon, or where the
trace is curved.
The longest segments are found where the
fault trace is relatively straight.
Figures I, 2, and Plate
I show the distribution of Quaternary fault scarps in the
upper Yellowstone Valley.
Fault Scarp Formation and Modification
The formation and modification of fault, scarps in un­
consolidated materials have been studied in detail by Nash
(1980, 1981a, 1981b), Witkind
(1964) and Wallace
elsewhere in the Basin and Range Province.
(1977,1980)
Fault scarp mor­
phology is initially a product of the mechanics of faulting
and the behavior of the faulted materials.
Deep Creek fault
scarps cut three general types of surficial materials:
I)
glacial tills of various ages, 2) fanglomerates, and 3)
range front colluvium.
The texture of these materials is
similar; they are Very poorly sorted, with the coarse frac­
tions dominated by angular cobbles and boulders of Precambrian crystalline rocks.
The mechanical behavior of these materials appears to
be similar enough that material variability can be ignored
for scarp analysis.
An initial scarp slope angle of approxi­
mately 60° is assumed; this figure appears to be a reason­
able estimate based on theoretical and laboratory results,
although higher angles are often seen in the field.
Higher
scarp angles usually result from tensional fracturing of
30
unconsolidated materials, and not from direct movement on a
faulted surface
(Wallace, 1977).
Basal moats or grabens commonly form at the base of
normal fault, scarps.
These features represent subsidence
associated with secondary fracturing in the hanging wall
block
(Witkind, 1964) and may vary from a meter to tens of
meters in width, and a meter or two in depth
(Wallace, 1977).
The grabens will usually be rapidly filled in.and covered
(Nash, 1981b) but the larger ones may be quite persistent.
Several of the scarps along the Deep Creek fault have basal
grabens
(Fig. 4); these vary from 3 to 5 m in width, and 0.2
to 0.5 m in depth.
These grabens are most often found where
scarps traverse upslope; they are apparently being modified
as drainage channels, which may explain why they are still
visible.
In relatively flat areas, they may act as sag
ponds; these depressions usually contain more luxuriant
plant growth than their surroundings.
Because of these mod­
ifications, profiles of these scarp areas have been avoided
for geometric analysis.
However, the graben. may contain
datable sediments, if drainage modification hasn't progressed,
too far.
The graben in Figure 4B is an example of a sag-
pond graben on the Gray's Ranch property north of Yankee
Jim Canyon.
A soil profile described from a pit in this
graben will be discussed in a later section on scarp ages.
The relationship between actual location of bedrock
faults and fault scarps in overlying surficial materials is
31
Figure 4. Photographs of basal grabens preserved along the
Deep Creek fault. A, basal graben along the Counts' Ranch
scarp.
B , basal graben along the Gray's Ranch scarp.
Note
location of soil pit; see Figure 7 for a soil profile.
32
rarely well defined.
With the possible exception of the
excavated scarp previously described by Pardee
(1950)(which
is no longer exposed), the surface scarp/bedrock fault rela­
tionship is not well expressed along the Deep Creek fault.
Witkind
(1964), in his study of faults reactivated during
the 1959 Hebgen Lake, earthquake concluded that most surface
scarps there coincided closely with bedrock faulting.
Some
scarps occur upslope from the projected bedrock fault,
although they parallel the concealed fault trace.
The rela-
i
tionship is best expressed on the Deep Creek fault just
north of Elbow Creek, where an en echelon fault scarp coin­
cides with the Precambrian/Quaternary contact and a steep
break in slope.
This information at least tentatively points
to a close correlation between surface expression
scarps)
and bedrock faulting.
(fault
Shallow geophysical .Investii-
gations would be required to confirm this hypothesis.
Erosional modification of normal fault scarps must be
thoroughly understood before accurate dating can be attempted.
The initial scarp slope angle is usually 60° or greater,
which is generally higher than the angle of repose of most
surficial materials.
Debris sloughs off the scarp face,
causing the slope to retreat back.
The sloughed material
collects at the base of the scarp and forms a debris slope
at the angle of repose
(Fig. 5A).
"slope replacement" by Wallace
by Nash
(1981a).
This process was called
(1977), and "slope retreat"
The retreat or replacement phase may vary
33
from hundreds to .several thousand years
arid climates, to several decades
humid regions.
(Wallace, 1977) in
(Wallace,
1980) in m o r e .
At the end of this phase, the slope face of
the scarp will consist of a debris slope standing at the
angle of repose of the underlying material .(Nash, 1981b).
The final stage of scarp modification was referred to as
"slope decline" by Wallace
by Nash
(1981a).
(1977) and as "slope founding"
After completion of the slope retreat
phase, the gradient of the scarp slope decreases, and the
crest and toe sections of the scarp become progressively
more rounded
(Fig. SB) .■
Figure SC summarizes the complete
modification of a normal fault scarp.
All the scarps along
the Deep Creek fault have long since completed the slope
retreat phase, and are now undergoing slope rounding.
34
METERS
Figure 5. Diagram illustrating the erosional modification
of a normal fault scarp.
A, initial slope retreat phase;
scarp retreats, forming a debris slope at the angle of
repose (approximately 35° for the Deep Creek fault mate­
rials) . B , final slope rounding phase; crest and toe seg­
ments become progressively more rounded through time.
C,
summary diagram, showing slope retreat followed by slope
rounding.
After Nash (1981b, p. 8, 10, 11).
35
FAULT SCARP ANALYSIS
Field Relationships
Methods
All near-recent scarps along the Deep Creek fault were,
initially examined and mapped in the field using standard
geomorphic techniques,
including degree of dissection,
freshness of morphology, and cross-cutting relationships.
From this analysis, three groups or ages of scarp-forming
events were identified in the upper Yellowstone Valley.
Relative-Age Relationships
Youngest event.
Fault scarps in the Barney Creek, Elbow
Creek, Counts' Ranch, and Gray's Ranch areas
(Fig. I) all
cut Pinedale age or younger surficial materials
(Plate I)
and therefore must postdate the 30,000 year date obtained by
Pierce and others
Yellowstone basin.
(1976) for similar deposits in the West
Cross-cutting relationships along the
Gray's Ranch and Barney Creek scarps appear to indicate a
late Pleistocene/early Holocene date for scarp formation.
The Gray's Ranch scarp is over 6 km long, and repre­
sents the southernmost surface expression of the Deep Creek
fault.
The scarp cuts a large alluvial fan at the foot of
Dome Mountain, 3.6 km north of Yankee Jim Canyon, but is
36
i
buried by a similar fan 750 m to the south (Fig. 6).
This
"bracketing" relationship is significant because of the dis­
tinctive nature of these alluvial fans.
During the Pinedale
glaciation, this portion of the Yellowstone Valley was overlain by at least 750. m of piedmont glacial ice (Pierce,
1979).
Severe glacial erosion of the mountain front is
still evident here today
(Fig. 6), so it is highly unlikely
that these fans would have been preserved beneath the Pinedale ice sheet.
Therefore they must postdate removal of ice
from this part of the valley, which was probably completed
by 12,000 to 13,000 years BP (K.L. Pierce, pers. comm.,
1982).
Morphometric analysis of these distinctive fans indi­
cates that they may be examples of what Ryder
called "paraglacial alluvial fans".
deposited shortly
(1971) has
These are alluvial fans
after deglaciation in mountainous areas.
Ryder studied alluvial fans in southern British Columbia,
and determined several unique characteristics of these
features:
I) paraglacial fan gradients were usually much .
steeper than for arid-region alluvial fans, and 2) fan gradi
ents showed a much lower correlation to basin parameters
(such as basin.area and relief), than did arid-region fans.
These differences were attributed to a plentiful supply of
easily-eroded material
(tills draped on the landscape) and
the existence of at least a portion of the basin prior to
initiation of fan development, instead of basin development
37
Figure 6. Photograph of Gray's Ranch scarp, view looking
north. Scarp cuts upper portion of large fan in center of
photo, and is buried by smaller fan to south. Note the
glacially-eroded mountain front upslope from fans.
38
concurrent with fan development as with arid-region fans These fans can be completely formed in as little as 1,000
to 2,000 years
(Smith, 1975).
The Dome Mountain fans do have steep gradients
(90-15°
for the upper one-fourth of the fan, measured along a medial
profile), which are much higher than the S0-V0 average grad­
ients of arid-region fans
(Bull, 1962; Melton,
fortunately the low number of fans
1965).
Un­
(two) did not allow sta­
tistical correlation, so the fan and basin parameters could
not be compared with known paraglacial and arid-region allu­
vial fans.
Fan materials consist almost exclusively of glaciallyderived cobbles and boulders o f Precambrian and Tertiary
rocks in a muddy matrix.
The presence of flow units that
appear to be pulses or slugs of debris, suggests that they
were deposited by debris flows and mudflows, with little
if any fluvial deposition.
This suggests deposition during
climatic and hydrologic conditions very different from those
operating today, for fluvial activity completely,dominates,
along the modern tributaries to the Yellowstone River.
Both
'
fans have very similar surface characteristics (and there; '■
.
■
fore may be of similar age) and appear to have been inactive
for at least several thousand years.
These simple relationships suggest that the two Dome
Mountain fans are late Pleistocene/early Holocene in age; a
date of 10,000 to 12,000 years seems reasonable.
The fan-
39
bracketed Gray's Ranch scarp therefore must be considered
the same .age.
A late Pleistocene date for scarp formation is also
indicated by evidence found in a soil pit dug in a scarp
graben 3.8 km north of Yankee Jim Cany o n . ' Figure 7 is a .
diagrammatic sketch of the soil profile from this scarp
graben.
The most significant evidence is the occurrence of
unweathered loess directly lying on unweathered Pinedale
glacial till at the base of the profile.
This implies that
the graben was formed and subsequently filled with loess
before any significant surface weathering could occur.
The
author correlates the lower loess unit with late Pleistocene
deglaciation conditions; the upper loess unit may correlate
with a Holocene glacial resurgence
in the region.
(Neoglaciation)
elsewhere
Another important implication is that no
subsequent movement has taken place on the fault, because
the soil horizons in the graben are essentially horizontal
and undisturbed.
A late Pleistocene/earIy Holocene age is also indicated
for the Barney Creek scarps
(Fig. 8), where association with
paraglac.ial landforms is again evident.
The scarps cut Pine-
dale glacial deposits, and a large alluvial fan at the mouth
of Barney Creek.
To the south, the scarps are buried by
flood-boulder deposits in the bottoms of Cascade and McDonald
Creeks, as well as by a large mudflow south of Cascade Creek
f
(Fig. 9, Plate I).
40
EAST
WEST
Surface soil
(A) horizons
Loess
METERS
Pinedale glacial
l^ 1
till
jj£j Soil pit
METERS
^
DEPTH IN CM
0
Fault
HORIZON
SURFACE S O I L . Silt loam, very dark
gray
(10YR3/1), ver y weak fine
crumo s t r u cture.
T R A N S I T I O N . Silt loam, dark brown,
(10YR3/3 ), massive. Consists of
loess with translocated humus.
BURIED S O I L . Silt loam, v e r y dark
gray
(10YR3/1), very weak fine
crumb structure.
L O E S S . Silt, grayish brown ( 1 Q Y R 5 / 2 ),
massive.
GLACIAL T I L L . Unv/eathered, very
2 Cb
light gray brown (1 0 Y R 6 / 2 ), massive.
Figure 7. Diagrams describing details of the Gray's Ranch
scarp graben.
A, diagrammatic cross section across scarp
graben. B, soil profile of pit dug in graben.
Note lower
loess unit rests directly on unweathered Pinedale till.
Soil classified as Pachic Cryoboroll, no calcium carbonate
in the profile.
41
Figure 8. Photograph of several scarps in Barney Creek
area.
Scarps are cutting Pinedale glacial deposits and
late Pleistocene alluvium.
View looking east, note rela­
tively fresh appearance of scarps.
Figure 9. Oblique aerial photograph of Barney Creek scarps,
view looking northeast.
Note large, late Pleistocene mud­
flow which buries scarp to the south.
42
The lack of any active distributaries other than Barney
Creek itself indicates that the Barney Creek alluvial fan is
now inactive, although the fan does show evidence of rejuve­
nation and dissection of the upper portion of the fan, pre­
sumably from uplift along the fault.
The flood-boulder deposits are restricted to creek
bottoms; they are essentially matrix-free, and contain subangular cobbles and boulders from 20 cm to over a meter in
diameter.
Clearly these high energy deposits were formed
in a substantially different climate than today.
represent cloudburst activity
They may
(Montagne and Chadwick,
or perhaps are a result of slushflows
1982),
(Washburn and Gold-
thwait, 1958; Theakstone, 1982) related to ice or snow melt.
Whatever their origin, a late Pleistocene age seems likely.
A large mudflow buries the Barney Creek scarp between
Cascade and McDonald Creeks
(Fig. 9).
This feature consists
of Precambrian clasts ranging in size from gravels to boul- .
ders over a meter in diameter, suspended in a clay-rich
matrix
(Montagne and Chadwick,
1982) .
The large size of
this flow suggests a close association with glacial melt
conditions and ground saturation in late Pinedale time.
No
evidence of recent movement is visible anywhere on the flow.
Many other mass movements of this type have been correlated,
with late Pleistocene conditions in other parts of the. Yel­
lowstone Valley
(Waldrop and Hayden,
Gallatin Valley to the west
1963) and the upper
(Hall, 1960b).
43
C loseIy-spaced cross-cutting relationships of the
G r a y 1s Ranch and Barney Creek types are not associated with
the other young scarps in the upper Yellowstone Valley.
Both the Counts' ranch and Elbow Creek scarps have been
deeply dissected in the bottoms of. tributary streams, but
this erosion may have been associated with much younger
streamflow events.
Correlation of these scarps to the bet­
ter documented Gray's Ranch and Barney Creek scarps requires
additional data, which will be discussed in a later section
on scarp profile analysis.
Intermediate event.
The presence of several ages of glacial
tills in the Yellowstone Valley was particularly helpful in
defining the general age of the Pool Creek fault scarp.
At
the mouth of Pine Creek, this scarp apparently cuts Bull
Lake lateral moraine
(Montagne and Chadwick,
1982) and is
subsequently buried by Pinedale moraine directly to the south
(Fig. 10).
This relationship suggests.a date of movement
less than 140,000 years BP, and greater than 30,000 years
BP, based on obsidian-hydration dating of similar moraines
in the West Yellowstone basin
(Pierce and others,
1976).
Surface evidence which indicates an older age include the
increased degree of slumping, and poor preservation of the
scarp.
The differences in elevation of Bull Lake and Pinedale
moraines in the Pine Creek area may also suggest that
■
44
Figure 10.
Photographs of the Pool Creek scarp. A, scarp
exposed across the central portion of the photo.
View look­
ing east; note the generally subdued expression of the scarp.
B , oblique aerial photograph, view looking southeast. Note
the scarp cuts the timbered ridge (Bull Lake lateral moraine)
and is buried by the Pinedale moraine to the south.
— 45 —
faulting was active between these two glaciations.
Pierce
(1979) described offset five times greater for the Bull Lake
moraines than for the Pinedale moraines in the Pine Creek
area.
The Bull Lake terminal moraines are approximately 180
m lower with respect to corresponding Bull Lake lateral
moraines, whereas the Pinedale terminal moraines are 30-40 m
lower than corresponding Pinedale lateral moraines.
These
discrepancies may be related in part to fault offset, but the
magnitude of faulting is open to question.
In the upper
Yellowstone Valley, Pinedale moraines of valley glaciers are
almost always found relatively up-valley from Bull Lake
moraines
(Montagne and Chadwick,
19 8 2) .
tionships therefore may be explained by
The Pine Creek rela­
draping of the gla­
cial deposits over the front of the Short Hills block, across
the trace of the Deep Creek fault.
The Bull Lake moraines
extend further down-valley than the Pinedale moraines, and
therefore would be expected to have a greater elevation dif­
ference.
Unfortunately the Pine Creek Bull Lake terminal
moraines are the only examples still preserved on the hang­
ing wall of the Deep Creek fault; all others in the upper
Yellowstone Valley have been buried by surficial debris.
Regardless of the explanation for the Pine Creek moraines,
range front faulting should be examined as a possible cause .
of moraine elevation differences found elsewhere in areas
with a history of Quaternary faulting.
46
Oldest event.
The oldest faulting event still preserved in
the upper Yellowstone Valley is represented by the very sub­
dued scarp found on the Strong's Ranch property in the
northern part of the valley
(Fig. 11).
This scarp cuts
rangefront colluvium of unknown age, and has been extensively
dissected.
Slumping and soil creep have modified the scarp
along its entire length.
Although an older age is indicated,
these limited field relationships do not allow further dat- ■
ing of this scarp.
Additional data which helps substantiate
this older date will be discussed in the next section of
this report.
Scarp Profile Analysis
Profile Measurement Techniques
Other techniques for scarp dating were required for some
of the Deep Creek fault scarps.
One technique commonly used
in fault scarp analysis today is scarp profiling.
The topo­
graphic form of the scarp is quantified by measuring accurate
profiles across the scarp at selected intervals.
This in­
formation is then analyzed in various ways..
Although other
methods are available
1979)1, in this
(Bucknam and Anderson,
study a Brunton compass, Jacob's staff, and measuring tape
were used to measure variations in slope across the scarps.
The staff was placed on the scarp surface, parallel to the
slope, and segments with similar slope angle were measured
by placing the compass directly on the staff.
The profile
47
Figure 11.
Photograph of Strong's Ranch scarp, exposed in
center of photo.
View looking east-southeast; again note
the subdued expression of the scarp.
48
of a typical fault scarp, and the parameters used to define
it are shown in Figure 12.
Analysis Methods
Several recent studies have attempted to date fault
scarps through analysis of. scarp profiles.
Wallace
(1977)
examined fault scarps in north-central Nevada, and devised
several dating methods for dating scarp profiles.
The two
techniques that appeared most useful for analysis of the
Deep Creek profiles were:
I) comparison of the width of
break-in-slope at the qrest of the scarp, and 2) comparison
of the angle of the principal slope, or straight segment
which dominates On the face of the scarp.
Bucknam and Anderson
(1979) used statistical analysis
to define a strong relationship between scarp slope
cipal slope) angle,,scarp height and scarp age.
(prin­
This analy­
sis indicated that the scarp slope/scarp height relationship
could be approximated by a logarithmic curve, and that re­
gression lines and equations'fit to this data can be used
as relative-dating tools.
Scarps of comparable age should
have similar regression lines and equations;
lines of older
scarps should have lower slopes and plot relatively below
lines of younger scarps.
They concluded
(as did Wallace)
that scarp angles decrease through time, and that for scarps
with similar initial angle but dissimilar height, the lower
scarp will degrade faster.
49
CREST
SURFACE
OFFSET
PRINCIPAL
SLOPE
SCARP
HEIGHT
METERS
Figure 12. Diagram of a typical normal fault scarp.
Toe
and crest segments, principal slope and principal slope
angle ( Q ) , scarp height and surface offset are labeled.
Modified from Bucknam and Anderson (1979, p. 13).
50
Nash
(1980, 1981a,
1981b) has derived a quantitative
mode I for morphologic dating of fault scarps, in which the
erosional degradation of fault scarps was modeled with
several computer programs.
These models quantify the rela­
tionship between original and present scarp angles, scarp
height, an empirically derived■coefficient of diffusion .
(essentially an erosion factor), and the age of the scarp.
These techniques all
.have their own inherent limita­
tions, especially when an attempt is made to apply them to •
other geographic areas where hillslope processes and' climate
may be significantly different.
Deep Creek Results
Technique Limitations
An attempt was made to.apply the dating methods de­
scribed above to the profile data measured along the Deep
Creek fault.
This analysis met with only limited success,
because of problems of limited scarp preservation,
scarp
modification by slumping, soil creep and stream dissection,
and variations in original slope.
The comparison of crestal scarp widths proved inconclu­
sive; the wide variation in original slope and limited pres­
ervation of the older scarps invalidated this technique in
the upper Yellowstone Valley.
Comparison of principal slope
angles was also inconclusive, because slope angles were
clustered in the 250-28° range for all scarps measured
(Fig.
51
13).
This may be a result of small increments of displace­
ments
(less than a meter) which would tend to maintain a
relatively uniform slope
(R.E. Wallace, pers. comm., 1981)
or may represent some sort of quasi-stable slope for this
environment.
. The application of Nash's morphological model is ham­
pered by several problems:
I) the: coefficient of diffusion
is a constant, so that climatic variations during the Pleis­
tocene probably restrict use of the model to the Holocene;
2) the model is designed for analysis of scarps with hori­
zontal toe and crest segments
(unfortunately the Deep Creek
fault scarps all cut slopes ranging from 4° to over 15°);
a n d '3) the model is designed for analysis of scarps in cohe­
sionless materials, and may not adequately explain the be­
havior of surficial material along the Deep Creek fault.
Preliminary results indicate that these problems will give a
date substantially younger than that derived from other cri­
teria
(4000 years too young for the Gray's Ranch scarp, using
a coefficient of diffusion from the Hebgen Lake area).
The
model therefore needs to be modified to address these prob­
lems before accurate results can be obtained
(D.B. Nash,
pers. comm., 1982).
Regression Analysis Results
.
Regression analysis of the Deep Creek fault scarp data
proved to be the most useful of all the profiling techniques.
52
S
PRINCIPAL
SLOPE
ANGLE ( * )
2
PRINCIPAL
SLOPE
ANGLE 10)
Figure 13. Histograms of principal slope angles of selected
Deep Creek fault scarps. A, Gray's Ranch; B , Barney Creek;
C , Counts' Ranch; D, Strong's Ranch; E , Pool Creek.
'53
although the low R
2
values of some scarp data reduced the
usefulness of this technique as well.
The Counts' Ranch,
Gray's Ranch, Elbow Creek and Barney Creek data points,
regression lines and equations cluster quite closely (Fig. '
14, Table I), which helps to substantiate the conclusion
that.these scarps are of similar age.
Therefore an age date
of 10,000 to 12,000 year BP is thought to be reasonable for
this group of scarps.
Unfortunately the dissected nature of the Strong's
Ranch and Pool Creek scarps hindered acquisition of suffi­
cient profile data to conclusively fit regression lines
(Fig. 14).
The lack of a linear trend itself suggests an
older age, because the distal ends of the scarp generally
have less displacement,
eroded.
and are therefore more easily
The older the scarp, the less likely the lower por­
tions of the scarp will be preserved.
The position of the
Pool Creek data may indicate that this scarp is more closely
associated with the age of the younger group of scarps; per­
haps 30,000 to 50,000 years BP would be a more reasonable
age estimate than that defined by the field relationships.
An older trend is definitely indicated for the Strong's
Ranch data, as the points plot almost completely out of the
field of data for the youngest scarps
(Fig. 14).
The lower
position of the data also shows an older trend than the Pool
Creek scarp data, although an exact age is still open to
speculation.
Moraines older than the Bull Lake glaciation
54
0 ELBOW CK, BARNEY CK
GRAYS,COUNTS RANCH
[S POOL CREEK
Q STRONGS RANCH
SCARP HEIGHT (METERS)
(x) STRONGS RANCH
M P O O L CREEK
SCARP HEIGHT (METERS)
Figure 14.
Regression data from principal slope angle and
scarp height measurements of Deep Creek fault scarps.
A,
raw data plot; B , regression lines fit to profile data.
Note location of Strong's Ranch data in both diagrams.
See
Table I for regression equations of lines.
Table
I.
Statistical analysis of Deep Creek fault scarp profile data.
Note
close correlation of Gray's Ranch, Barney Creek, Counts' Ranch,
and Elbow Creek regression equations. See Figure 14 for graphic
presentation of regression lines.
Regression '
Equation
R2
(%)
SD
(o)
Number of
Measurements
G r a y 's Ranch
0 - 11.66 + 15.28 Log H
23
2.3
22
Barney Creek
0 =
8.60 + 21.59 Log H
70
4.6
22
Counts' Ranch
0 = 10.55 + 17.93 Log H
41
3.1
16
Elbow Creek
0 = 13.20 + 16.85 Log H
54
2.8
16
Pool Creek
——
1.0
9
Strong's Ranch
—
1.3
9
Scarp
Location
NOT E S :
REGRESSION EQUATION:
R^
- coefficient of determination
SD
- standard deviation of measured
H
- scarp height in meters
Y = Y-
0
- principal slope angle in degrees
B = slope of line
0 = Y + B Log H[
(0 )
where:
intercept: value
56
usually do not show any morphology, so it .is probable that
hil!slope processes
(particularly solifluction)
active in
the.Pleistocene would have destroyed any smaI!-displacement
fault scarps
Older than this glaciation.
Therefore a date
of 100,000 to 200,000 years BP seems reasonable for the
Strong's Ranch fault scarp.
■ ■
History of Movement
; '
■
■
Nature of Movement .
The nature of displacement which produces fault scarps
will have an effect on the results of geomorphic analysis
(particularly profile analysis) of the scarps.
If recurrent
movement produces multifaceted s.carps, erosiorial modifica­
tion will not be constant; this will essentially "reset"
the degradational sequence and modify the pre-existing
scarp.
No conclusive examples of multiple or composite
scarps have been observed by the author, in the Yellowstone
Valley; all of the scarps are remarkably uniform in slope
and height along their lengths, with notable changes only at
the preserved distal ends.
In addition, the previously de­
scribed undisturbed graben sediments
(Fig. 7) along the
Gray's Ranch scarp also imply that no additional movement
■has occurred since scarp formation.
scarps
The heights of some
(10-12 m) possibly point to several periods of move­
ment, although single-event displacements as great as 6.7 m
were measured from historic faulting in the Hebgen Lake area
57
(Witkind, 1964).
The Deep Creek fault scarps are therefore
thought to be formed from single events, or closeIy-spaced
multiple movements of the Deep Creek fault, which were sepa­
rated temporally by quiet periods of much longer duration.
Faulting periods may have lasted for a day or less, whereas
the quiet periods may have lasted tens of thousands of years.
Rates of Movement
Maximum scarp heights of approximately 10-12 m have ■
*
been measured for all three age groups of scarps in the up­
.
per Yellowstone Valley.
Therefore.a total displacement of
30-35 m can be determined for the last 100,000 to 200,000
years of history in the valley, based on dates obtained in
this study.
This will give a rate of movement of approxi­
mately 200-300 m/million years for the later part of the
Pleistocene.
Rates derived from analysis of possible uplift
of the Short Hills block previously discussed also were
approximately 200-300 m since the early Pleistocene, so
these rates are probably within reasonable limits.
The
duration of movement is still open to speculation, as is the
duration of these rates of displacement.
Distribution
The scarp-forming events have been distributed inter­
mittently along the trace of the Deep Creek fault, much like
the distribution of recent seismic.activity along the Wasatch
Fault Zone
(Smith and Sbar,, 1974) .
Areas without fault scarp
58
development along active normal faults may represent gaps
of unreleased strain between zones of active movement.
Therefore areas along the Deep. Creek fault that do not show
Quaternary faulting should be considered just as prone to
earthquake occurrence as the areas with scarp development,
and perhaps even more susceptible.
59
■ SUMMARY AND CONCLUSIONS
The Deep Creek fault is a high-angle normal fault bound
ing the western flank of the Beartooth uplift.
The fault
trace is generally straight, with several small-scale bends
and en echelon breaks.
Evidence points to initiation of
movement along the Deep Creek fault as early as -'Paleocene
or Eocene time, associated with uplift of the Beartooth
block.
-
Near-recent fault scarps exposed along the trace
express three major periods of recent faulting still pre­
served in the upper Yellowstone Valley.
A fairly well docu­
mented period 10,000 to 12,000 years BP was preceded by two
poorly preserved periods of faulting; the Pool Creek scarp
May have formed 30,000 to 50,000 years BP, and the Strong1s
Ranch scarp could be much older, perhaps 1.00,000 to 200,000
years in age.
Rate of displacement has been approximately '
200-300 m/million years since the early Pleistocene.
The results of this study have shown that the nearrecent paleoseismic history of an area may be reconstructed
through fault scarp analysis.
In a general way, this recon­
struction has documented the recurrence intervals of major
faulting events in the near-recent history of the upper
Yellowstone Valley.
Fault scarp analysis can also be
60
helpful in explaining complex mountain front glacial rela­
tionships , particularly where deposits of various ages are
present.
Readers should be cautioned against directly applying
the results of this study to other geographic areas, because
fault scarp morphology is strongly controlled by climate,
aspect, materials, and other local factors as well as ag e .
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. 62
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U.S. Geological Survey Professional Paper 435-F,
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°
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69
APPENDICES
70
APPENDIX A
FAULT SCARP PROFILE DATA
71
A P P E ND I X A
Profile
Slope Angle
(O)
Scarp Height
(iti)
Surface C
(m)
Strong's Ranch
Scarp
23
25
26
25
25.
SRl
SR2
SR3
SR4
SR5
SR6
SR?
SR8
SR9
25
24
24
.
26
11.6
12.2
8.7
9.8 .
9.1
11.3
10.0
■ 9.0 '
11.1
■5.8
7.9
3.5
4.7
4.6
4.7
6.2
4.0
’ 4.9
Pool Creek
Scarp
PCI
PC 2
27
27
PC 3
29
PC 4
PCS
PC 6
PC7
PC 8
PC 9
27
27
30 .
30
29
9.6
■ 8.7
9.1
9.5
11.6
10.8
11.2
11.1
10.0
28
'
4.3
3.8
5.5
4.6
5.8
5.2
5'.4
6.0
4.6
Barney Creek
Scarp
BCl
BC 2
BC3 •
BC 4
BC5
BC 6
BC 7
BC 8
BC 9
BClO
BCll
' B C 12
BCl 3
BC 1.4
■ B C 15
B C 16
..
14
17
17
18
18
20
. 21
27
24
25
30
29
29
24
26
25
.
.
3.4
3.4
2.7
2.1
2.1
2.9
3.5
5.8
5.6
8.2
10.1
9.0
6.1
5.2
6.1
7.2
'
1.2
1.8
1.2
0.9
1.1
• 1.5
1.8
4.6
4.3
5.5
8.5
7.0
4.4
' 4.0
4.9
5.3
72
Profile
Slope Angle
(°)
Scarp Height
(m)
Surface Offset
(m)
Barney Greek
Scarps (Con 11)
BCl 6 ■
BC17
B C 18
BCl 9
BC 2 0
BC 21
BC 2 2
7.2
5.3
29
8.4
5.9
■ 27 '
24
20
26'
27
6.2
7.0
4.3
3.1
1.2
4.7
6.1
4.9
24
4.0
2.4
2.4
1.2
4.0
4.3
2.4
1.4
1.8
4.0
25
. .
4.1
2.7
Elbow Creek
Scarps
ECl
EC2
EC3
EC4
■EC5
EC 6
EC7
EC 8
EC 9
EClO
ECU
ECl 2
E C 13
E C 14
ECl 5
E C 16
22
27
25
22
21
21
24
27
21
21
24
20
20
22
19
' 6.4
7.6
2.7
1.8
2.4
5,3
4.9
4.4
4.6
3.7
. 2.7
3.2
■•
3.4
4.1
'
2.7
2.1
2.4
2.6
1.5
1.8
2.1
2.1
Counts 1 Ranch
Scarps
CRl
CR2
CR 3
CR4
CR5
CR6
CR7
CR8
CR 9
CRlO
CRll
. CRl 2
CRl 3
CRl 4
CRl 5
' CRl 6
20
20
. 25
17
17
16
4.4
4.3
22
22
4.6
17
19
26
23
19
25
22
21
6.9
5.9
4.6
2.1
4.0
3.1
• 2.6
■ 7.1
5.3
3.5
5.6
6.9
2.8
3.5
2.4
4.9
3.4
2.4
1.1
2.0
2.7
2.2
2.0
4.7
3.2
2.6
3.8
4.2
2.0
73
Profile
Slope Angle
(°)
Scarp Height ' Surface Offset
(m)
(m)
Gray's Ranch
Scarps
GRl
GR2
GR3
GR 4
GR5
GR6
GR7
GR 8
GR9
GRlO
GRll
GRl 2
GRl 3
GRl 4
G R 15
G R 16 .
GRl 7
GRl 8
GRl 9 •
GR20
GR21
GR22
22
27
23
28
26
22
27
26
25
23
24
22
24
27
21
26
26
21
11
15
13
18
9.1
6.5
3.1
12.5
4.6
4.7
7.0
8.5.
7.8
5.6
6.1
6.2
6.9
11.0
8.1
8.2
7.3
4.9
1.8
2.2
2.0
3.4
6.1
3.7
1.5
6.1
2.6
2.1
4.9
5.8.
5.6
3.7
>3.8
4.2
5.2.
7.9
5.5
5.8
5.8
3.7
1.5
■ 1.8
1.2
2.4
74
APPENDIX B
LOCATION MAPS OF MEASURED PROFILES
7
5
APP EN DIX B
STRONGS
RANCH
S C A R P (SR)
TN
T
2000
j
meters
Ranch
Creek
POOL C R EEK
S C A R P (P C )
Ranch
2000
meters
76
AP PE N D IX B
BARNEY
CREEK
S C A R P S (BC)
Ranch
Barney
CreeF
,R onch
2000
meters
Mudflow
7
7
A P P E ND I X B
COUNTS RANCH SCARP (CR)
Ronch
2000
I
?0
meters
Spring
Spring
Spring
ELBOW
CREEK
S C A R P S (EC)
/
2000,
___ i
500
—j
feet
meters
/
/
/
/
7
8
AP PE N D I X B
GRAYS RANCH SCARP (GR)
2000
meters
Ronch
Soil Pit
/
14
Personius- Plate I
SURFlClAL GEOLOGIC MAP OF EAST SIDE
OF
UPPER YELLOWSTONE VALLEY MONTANA
Stephen F
personius,
1982
REFERENCES
Koose and others, 1961; Roberts, 1964; Van Voast1 1964;
Pierce, 1979; Montagne and Chadwick, 1962
GLACIAL DEPOSITS
ALLUVIUM
MASS MOVEMENTS
QUATERNARY
TERTIARY
Tig
X J.
MESOZOIC
PALEOZOIC
NORMAL
FAULT:
Dashed where inferred, dotted
buried, bar and ball on downthrown side. Ha c hu re s ore
, Quaternary fa ult scarps, dashed where indefinite.
/P-M^
THRUST
MASS
FAULT
Teeth
on u p th r o w n
MOVEMENT SCARP
PC
PRECAMBRIAN
SPRING
A------------------------- A'
LINE OF CROSS
SECTION
KAP UNIT DESCRIPTIONS
Qal 2
..o_„°
RECENT ALLUVIUM. Materials generally coarse, moderately sorted
gravels associated with modern tributary streams and the
Yellowstone River. Little or no soil development present.
LATE PLEISTOCENE ALLUVIUM, Materials include alluvial fan
deposits, glacial outwash, and slope wash deposits. Sorting
generally poorer than Qal2. Weak soil development present.
LATE PLEISTOCENE AND HOLOCENE MASS MOVEMENTS. Includes slump
and slump-earthflow deposits. Tearaway scarp mapped where
evident. Weak soil development usually present.
Q pp
PINEDALE (WISCONSINAN) PIEDMONT GLACIAL DRIFT. Includes moraine
deposits of northern Yellowstone outlet glacier, deposited on
floor and walls of southern part of upper Yellowstone Valley.
Weak soil development present.
Qpv
PINEDALE (WISCONSINAN) ALPINE GLACIAL DRIFT. Includes moraine
and lake deposits in glaciated tributaries to the upper Yellow­
stone Valley. Weak soil development present.
Miles
» o
Contour interval 2 0 0 feet
o e
Qbl
eOe O 0<7
'
'
BULL LAKE (LATE ILLINCIAN) ALPINE GLACIAL DRIFT. Deposits
preserved only at canyon-rtouth positions north of Mill Creek.
Moraine morphology subdued, but still present. Soil profiles
usually show more extensive weathering of cobbles than
Pinedale glacial drift.
GLACIAL DEPOSITS.UNDIFFERENTIATED. May include drift of
pre-Bull Lake, Bull Lake cr Pinedale age.
Tig
B
TERTIARY IGNEOUS ROCKS. UNDIFFERENTIATED. Deposits Include
mtrusives and extrusives of Eocene Absaroka Volcanics
(andesite and dacite), and also late Miocene basalts on the
floor of the Yellowstone Valley.
PALEOZOIC AND MESOZOIC SEDIMENTARY ROCKS. UNDIFFERENTIATED.
Erosional remnants of limestone, sandstone and shale preserved
on the Beartooth block, and on the floor of the Yellowstone Valley.
PRECAMBRIAN (ARCHEAN) METAMORPHIC ROCKS. UNDIFFERENTIATED.
Deposits consist of high grade gneiss, schist, quartzlteT
marble and amphibolite exposed in core of Beartooth uplift.
EAST
B'
WEST
B
Horizontal
and v e r t i c a l
axes
scaled in
WEST
A
meters
( 3X
EAST
th e
map
scale )
where
plate.
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