Table 3

A. Luminescence age data from C

SamplenumberTrench on west trace of Clan Alpine fault, south wallCAW-TL1CAW-TL2CAW-TL3

Location

x/y (m)

11.85, 3.20

12.55, 3.00

12.60, 2.32

Unit

number

122

Datinga

method

TL-tb

IRSL

TL-tb

IRSL

TL-tb

IRSLIRSL

Temperatureb

data (°C)

124°/62 hrs124°/62 hrs124°/62 hrs124°/62 hrs

140°/7 hrs

124°/62 hrs

140°/7 hrs

Equivalentc

dose (grays)

39.69 ± 1.12%35.94 ± 1.19%63.10 ± 1.96%67.93 ± 0.92%

175.97 ± 3.68%

166.0 ± 1.80%

227.50 ± 0.44%

Dose ratef

(grays/ka)

7.323 ± 3.7%

do

7.057 ± 3.5%

do

6.202 ± 3.6%

dodo

Field & Sat.d

moistures

4.7 (41)

do

3.2 (39)

do

4.5 (43)

do

do

Modelede

moisture

10do10do20dodo

Luminescence

 ageg (ka)

5.42 ± 0.414.91 ± 0.378.94 ± 0.739.63 ± 0.72

28.37 ± 2.9626.77 ± 2.20

[36.68 ± 7.45]

2.0 4.0 6.0 8.0 

2.0

0.0

4.06.08.0

10.0

2.0 3.0 4.0 5.0 6.0 

1.00.02.03.04.05.06.0

Level lines (meters)

Figure 6. Trench log for Clan Alpine fault, west trench (CA

Mapped and described by M.N. Machette, K.M. Haller, C.A. Ruleman, K. Okumura, and S. Debray; September 9–17, 2001. Horizontal and vertical control by EDM theodolite (<1 cm accuracy). Trench location: UTM Zone 11S, 4372450 m N, 0427225 m E (NAD 27). Trench axis is 270° (E to W).

Described and mapped by M.N. Machette, K.M. Haller, C.A. Ruleman, K. Okumura, and S. Debray; September 10–17, 2001.Horizontal and vertical control by EDM theodolite (<1 cm accuracy).Trench location: UTM Zone 11S, 4372105 m N, 0428800 m E (NAD 27).Trench axis is 90° (W to E).

Figure 7. Trench log for Clan Alpine fault, east trench (CAE).

Level lines (meters)

EXPLANATION OF UNITS

EH1

DOWNDROPPED FAULT BLOCK

Unit 1—Younger alluvium and colluvium (Holocene to latest Pleistocene) Subunit 1-1—Distal piedmont alluvium Subunit 1-2—Fault-scarp colluviumUnit 2—Middle alluvium and colluvium (latest Pleistocene) Subunit 2-1—Distal piedmont alluvium Subunit 2-2—Fault-scarp colluviumUnit 3—Subangular gravel (late Pleistocene)Unit 4—Angular gravel (late Pleistocene)Unit 5—Clayey pebble gravel (late Pleistocene)Unit 6—Sandy pebble alluvium (late Pleistocene)Unit 7—Graben-fill sediment (late Pleistocene) Subunit 7-1—Pebbly sand Subunit 7-2—Sandy gravel Subunit 7-3—Pebbly sandUnit 9—Shear zone. Mainly composed of units 8 and 10 between F6 and F7Unit 10—Fluvial boulder gravel (early late Pleistocene or late middle Pleistocene). Degree of shading indicates carbonate accumulation in calcic horizonsUnit 8—Older fault-scarp colluvium (late Pleistocene)

1

2

4

3

3-1

3-2

AvB1tB2tB3t2B3

AvB1tB2tB32B3B

Soil profile

CAW-3:

Av

AB

B2tB3t

2Btb

 2Cn 

1-1 

2-1

AvBw

EH1

Highest possible position for downdropped units 6-8 

UTM grid declination: 0°31' W

UTM grid declination: 0°31' W

428,700 m E 428,800 m E 428,900 m E

 Profile CAE-3

 Profile 

CAE-1

Profile 

CAE-2

Soil pit

(CAE-1)

FlorenceCanyon Road

CAEtrench

Canal

Clan Alpine Ranch Road

l l l l l l l l l l l l l l l l l l l l

Figure 2. Surficial geologic map of the Clan Alpine fault, west trench site (CAW), showing locations of 

trench, scarp profiles, and soil pits.

Artificial fill or disturbed ground

Young (Holocene to latest Pleistocene) alluvial-fan deposits 

Middle (late to late-middle Pleistocene) alluvial-fan deposits 

Old (middle Pleistocene) alluvial-fan deposits 

Fault, main splay (red) and minor splay (black)—Dotted where concealed. 

 Bar and ball on downdropped side

Crest of fault scarp at trench sites

Location and height (m) of scarps at trench sites

EXPLANATION

2.9

3.1

Qfy

Qfm

Qfy

Qfm

Qpd

Qpd

2.2

Artificial fill or disturbed ground

Holocene ponded deposits (loess and playa sediment)

Young (Holocene to latest Pleistocene) alluvial-fan deposits 

Middle (late to late-middle Pleistocene) alluvial-fan deposits 

Fault, main splay—Dotted where concealed. Bar and ball on downdropped side

Crest of fault scarp at trench sites

Location and height (m) of scarps at trench sites

EXPLANATION

Figure 4. Surficial geologic map of the Clan Alpine fault, east trench site (CAE), showing locations of 

trench, scarp profiles, and soil pits.

0 50 100 METERS

0 50 100 METERS

4,372,100 m N 4,372,200 m N

359°29'

af/dQfyQfmQfo

af/dQpdQfyQfm

3

3

0

20 m

0

20 m

0

10 m

0

10 m

0

10 m

0 50 100 150 200

0 50 100 150 200 m

250 300 m

Profile CAW-1, azimuth: 97°53'

Profile CAW-2, azimuth: 95°21'

Profile CAE-3, azimuth: 98°46'

Profile CAE-2, azimuth: 96°23'

Profile CAE-1, azimuth: 98°21'

WEST EAST

WEST EASTWEST EASTWEST EAST

0 20 40 60 80 100 m

0 20 40 60 80 100 120 140 160 180 m

0 20 40 60 80 100 m

WEST EAST

Figure 3. Topographic profiles across scarps of the Clan Alpine fault, west trench site (CAW). Horizontal scale not the 

same as on figure 2.

Figure 5. Topographic profiles across scarps of the Clan Alpine fault, east trench site (CAE). Horizontal scale not the same as on figure 4.

359°29'

4,372,400 m N 4,372,600 m N

427,000 m E 427,200 m E 427,400 m E

Topographic profile CAW-1

Topographic profile CAW-2

Soil pit(CAW-4)

Florence Canyon Road

Soil pit(CAW-1)

Buried water pipeline

Qfm

Qfy

Qfm

Qfy 

Qfo

Qfo

Qfy

af/d

CAW Qfm

trench

0.6

4.8–5.5

4.5

2.5

 7.3

1.2

6-8

Standpipe

l l l l l l l l l l

l l l l l l l

l l l l l l l l l l l

l

l

l l l l l l

l l

l l l l l l l l l l l l l l l l l l

l l l l l

l l l l

Figure 1. Topographic base map for Clan Alpine fault trenching study, west-central Nevada.

Base map from U.S. Geological Survey,Camp Creek Canyon, Clan Alpine Ranch, Cold Springs, and Mt. Augusta 1 .5 0 1 KILOMETER

SCALE 1:24 000

1 1/ 2 0 1 MILE

SC site

Mt. Augusta 7.5' quadrangle

Camp Creek Canyon 7.5' quadrangle Cold Springs 7.5' quadrangle

Cold Springs 7.5' quadrangle

39°30' N.

117°52'30" W.

Area of

figure 2

Area of

figure 4

CLAN ALPINE 

FAULT 

STUDY AREA

Desatoya 

fault

Clan Alpine fault

EDWARDS CREEK VAL LEY

CLAN ALPINE MOUNTA INS

(SOUTH ERN PART)

Clan Alpine fault

noyna

r

C

Star

Lake Edwards

shoreline

(5,280 ft, 1,61

0 m)

Lake Edwards shoreline

(5,280 ft, 1,610 m)

DESATOYA

MOUNTAINS

80

50

Fallon

Austin

Winnemucca

EXPLANATION

Clan Alpine and Desatoya faults

—

 Bar and ball on downdropped side.  Dotted where concealedMinor or other faults—Bar and ball  on downdropped side. Dashed  where discontinuous; dotted where  concealedShoreline of Lake Edwards (5,280 ft, 1,610 m)—Dotted  where concealedStarr Canyon profile of Pearthree  (1990)

Cedar Mtns

STUDY AREA

Central Nevada Seismic Belt

NEVADA

INTRODUCTION

As part of regional studies of paleoseismology in the northern Great Basin, we 

are studying selected major extensional Quaternary faults in a traverse from Reno, 

Nev., to Salt Lake City, Utah, between latitudes 39° and 41° N. In 2001, we 

trenched the southern part of the Clan Alpine fault (CAF) about 2 km northwest of 

the Alpine Ranch (see fig. 1). The fault separates the Edwards Creek Valley (on 

the east) from the impressive front of the uplifted Clan Alpine Mountains (on the 

west); faceted spurs along the front suggest substantial Quaternary movement 

along the CAF (dePolo, 1998). Based on the tectonic geomorphology of the 

mountain front, dePolo (1998) estimated a long-term slip rate of 0.15 mm/yr for 

the CAF. Conversely, conspicuous fault scarps exist along only part of the range 

front, suggesting that little movement has occurred on the CAF in late Quaternary 

time. 

The purpose of this map product is to present stratigraphic, geomorphic, and 

structural evidence for interpreting the late Quaternary movement history of the 

CAF. The interpretive data will be presented elsewhere, pending results of further 

dating studies. Nevertheless, the stratigraphic relations shown on this map 

demonstrate two latest Quaternary surface-faulting earthquakes in the past 30 k.y., 

and suggest that latest Quaternary slip rates near the southern end of the fault 

zone are slower than previously suggested for the whole fault zone.

THE CLAN ALPINE FAULT

The Clan Alpine fault lies just to the east of the Central Nevada Seismic 

Belt—a zone of historically active faulting and seismicity that extends from 

Winnemucca, on the north, to Cedar Mountains, on the south (fig. 1). The most 

recent surface faulting in the vicinity was associated with the Ms 7.2 Fairview Peak 

and Ms 6.8 Dixie Valley earthquakes, which occurred about 4 minutes apart on 

December 16, 1954 (Caskey and others, 1996) about 30 km west of our study 

area. During these large earthquakes, minor surface ruptures also formed along 

the Gold King and Middlegate faults, the latter of which is a west-dipping normal 

fault at the southwestern margin of the Clan Alpine Mountains, about 12 km to 

the west-southwest of our study area. 

The CAF is a major north- to northeast-striking, relatively narrow range-front 

fault zone that bounds the eastern flank of the Clan Alpine Mountains and the 

western flank of the Edwards Creek Valley. The Edwards Creek basin is probably 

a structural half-graben that deepens to the west. Faulting on the eastern side of 

the basin seems rather minor, and low bedrock knobs extend well out from the 

Desatoya Range, which bounds the eastern side of the Edwards Creek Valley. 

Near its southern end, the west-dipping Desatoya (DF) and Eastgate (EGF) faults 

become the major range-bounding faults of an eastward-deepening series of halfgrabens. This north-to-south transition from a west-dipping half-graben to 

multiple east-dipping half-grabens is along a diffuse west-northwest transverse 

accommodation zone(?) that roughly defines the southern end of the CAF and the 

northern ends of the DF and EGF. Stewart and others (1999) mapped a westnorthwest-trending fault that cuts across the southern part of the Clan Alpine 

Mountains and adjacent Miocene basin sediments; this fault may represent the 

surface manifestation of the suggested accommodation zone.

The Clan Alpine Mountains and Desatoya Range straddle the Edwards Creek 

Valley, which is presently a closed basin with a floor elevation of about 5,115 ft 

(1,560 m). [Elevations are shown in feet on the USGS topographic base map (fig. 

1).] Lake Edwards has occupied this basin intermittently through the middle 

Pleistocene (750–130 ka) and late Pleistocene (130–10 ka). The latest 

Pleistocene lake was rather shallow (<50 m deep), rising to a maximum elevation 

of about 5,280 ft (1,610 m) (Mifflin and Wheat, 1979), well below all traces of the 

CAF. Most of the stratigraphic and geomorphic evidence for the lake are 

preserved at its northeastern end, where it formed a set of prominent bars, spits, 

and gravelly shorelines. Prior deep stages of the lake may have risen well above 

the 5,280-ft (1,610-m) shoreline, especially if overflow occurred from Lake 

Desatoya (Snyder and others, 1964) in the Smith Creek Valley. This connecting 

channelway has an overflow threshold at 6,230 ft (1,899 m), 8 m above the latest 

Pleistocene sill of Smith Creek Valley (Reheis, 1999).

The CAF extends about 35 km along the eastern front of the Clan Alpine 

Mountains. Along most of the range front, the fault shows down-to-the-southeast 

displacement of Quaternary piedmont-slope deposits against Tertiary bedrock 

(Dohrenwend and others, 1992). Scarps are relatively sparse and poorly 

preserved but consistently face east (Pearthree, 1990; Dohrenwend and others, 

1992), except at the southern end where antithetic faults form about one-fourth of 

the young throw on the CAF. South of Starr Canyon (see fig. 1), the fault 

bifurcates into multiple subparallel traces that form a horsetail pattern. The largest 

and most continuous strand crosses Florence Canyon Road (fig. 2), and forms 

scarps that are as much as 8 m high. Smaller scarps (see fig. 3, scarp profile 

CAW-1) are formed on an alluvial-fan deposit (unit Qfm, fig. 2) that is believed to 

be either mid-Wisconsin (marine isotope stage IV) or pre-Wisconsin and related to 

the Bull Lake glaciation (marine isotope stage VI) of the Rocky Mountains. The 

large scarp that we trenched (fig. 6, west trench, CAW) is formed on a clearly 

older alluvial-fan deposit (unit Qfo), which we believe is pre-Wisconsin (marine 

isotope stage VI) and either related to the Bull Lake glaciation of the Rocky 

Mountains or to an older (marine isotope stage VIII?) glaciation of the Rocky 

Mountains. These deposits have not yet been dated by cosmogenic-nuclide 

methods; thus our correlations to geo-climatic events remain uncertain. We 

consider units Qfm and Qfo to be as young as 75–60 ka and 150–130 ka, 

respectively (younger interpretation), or to be as old as 150–130 ka and 250–230 

ka, respectively (older interpretation). The estimated ages of these deposits are 

based on the soils developed on their relict alluvial-fan surfaces (see table 4, soil 

field properties). Unit Qfm is also present in the east trench (CAE, fig. 7).

Although most traces of the CAF are in a BLM Wilderness Study Area (WSA), 

we were able to trench a 7- to 8-m-high, partly buried scarp on the main fault in a 

narrow exclusion in the WSA (fig. 2) and a partly buried (<3 m high) antithetic 

fault scarp (fig. 4) 1.6 km downslope, east of the WSA. Exposures of the main 

fault (see fig. 6, CAW trench log) revealed two classic colluvial wedges (units 1 and 

2, table 1) above a thicker wedge-like body of gravel (unit 3) and alluvial-fan 

deposits (unit 4). Unit 3 is interpreted as a combination of scarp colluvium and 

fluvial gravel that were deposited against the scarp from the third faulting event. 

The underlying and lowest unit on the hangingwall block is unit 4, a well-sorted 

sandy pebble to boulder gravel that was laid in against a preexisting fault scarp 

formed on units 6–8 of the upthrown fault block. Unit 4 is considered to be part 

of the fan-forming Qfm, which came from Florence Canyon and was deposited in 

a southerly direction (as indicated by pebble imbrication measurements). The two 

most recent surface-faulting earthquakes produced about 4 m of displacement in 

the trench and a 5- to 6-m-high scarp on the surface, about 100 m north of 

Florence Canyon Road. Fault-scarp colluvium units 1 and 2 gave preliminary 

luminescence ages of about 9

±1 ka and 28

±3 ka, respectively (see table 3

A), 

which suggests that the most recent earthquake occurred at about 10 ka and the 

penultimate earthquake occurred at about 30 ka. Indirect evidence of older 

faulting (pre-unit 4) is recorded by more than 7 m of surface displacement in the 

older sequence of alluvial-fan deposits (units 6–8, about 250–130 ka).

The antithetic fault is about 1.7 km to the east, and its scarps are poorly 

preserved east of the road north from Alpine Ranch owing to its uphill (westfacing) aspect (fig. 5). Trenching here (see fig. 7, CAE trench log) shows direct 

evidence for three faulting earthquakes (about 6 m of vertical displacement). The 

fault-scarp colluvium (units 1 and 2, table 2) gave preliminary luminescence ages of 

about 10

±1 ka and 28

±2 ka, respectively (see table 3

B), which suggests that the 

most recent event occurred at about 10 ka and the penultimate event occurred at 

about 30 ka—timing that is identical to that recorded in the CAW trench. The 

upthrown block is mantled by a relict Bt/Bk soil (see table 4, soil field properties) 

formed in coarse debris-flow deposits (about 100–50 k.y.?) that directly overlie 

distal alluvial-fan deposits, which we estimate to be about 130–60 ka. The 

antithetic fault records at least 6 m of displacement (since units can’t be matched 

across entire fault zone) and has more earthquakes that affect unit Qfm than the 

main fault. Thus, the antithetic fault may be a transitional, intravalley link that 

moves along with the east-dipping CAF and the east-dipping DF to the southeast.

Based on reconnaissance photogeologic mapping, Dohrenwend and others 

(1992) assigned a latest Pleistocene to Holocene age to a faulted Quaternary 

deposit at one locality along the CAF. On the basis of morphologic analyses, 

Pearthree (1990) calculated a mean age of 16.9 ka (22.6–11.2 ka) for small 

scarps along the southern part of the fault zone and thought that middle Holocene 

alluvial surfaces were unfaulted. dePolo (1998) assigned a preferred age of 130 ka 

(220–74 ka) to the alluvial-fan surface that is displaced 19.4 m on the southern 

side of Starr Canyon (SC site, see fig. 1), farther north along the southern part of 

the CAF. From these data, dePolo (1998) calculated a preferred vertical slip rate 

of 0.15 mm/yr for this site. The 130-ka age for the surface was based on relative 

position, surface morphology, and the presence of soils that have characteristics 

similar to those on Donner Lake outwash (dePolo, 1998). Conversely, we suspect 

that the alluvial-fan surface could be 250 ka (that is, unit Qfo) or older and that the 

slip rate could be substantially less. 

Although cosmogenic-nuclide dating will help determine the age of the faulted 

landforms, the existing luminescence dating and stratigraphic relations seen in 

trench CAW suggest that the CAF where we studied it has a low slip rate 

(0.025–0.08 mm/yr) and long recurrence intervals (

≥20,000 yrs). The range 

front’s seemingly young expression may be an artifact of the bedrock lithology and 

(or) faster slip rates earlier in the Quaternary or Pliocene. If the two to five times 

lower-than-reported slip rate on the CAF suggested from our preliminary work 

applies to the entire fault, it has important implications for the general activity rate 

of many of the major normal faults in the Basin and Range Province.

REFERENCES CITED

Birkeland, P.W., 1999, Soils and geomorphology, 3rd edition: New York, Oxford 

University Press, 430 p.

Caskey, S.J., Wesnousky, S.G., Zhang, P., and Slemmons, D.B., 1996, Surface 

faulting of the 1954 Fairview Peak (Ms 7.2) and Dixie Valley (Ms 6.8) 

earthquakes, central Nevada: Bulletin of the Seismological Society of 

America, v. 86, no. 3, p. 761–787. 

dePolo, C.M., 1998, A reconnaissance technique for estimating the slip rate of 

normal-slip faults in the Great Basin, and application to faults in Nevada, 

U.S.A.: Reno, Nev., University of Nevada Ph.D. dissertation, 199 p.

Dohrenwend, J.C., Schell, B.A., and Moring, B.C., 1992, Reconnaissance 

photogeologic map of young faults in the Millett 1° by 2° quadrangle, Nevada: 

U.S. Geological Survey Miscellaneous Field Studies Map MF–2176, 1 sheet, 

scale 1:250,000.

Mifflin, M.D., and Wheat, M.M., 1979, Pluvial lakes and estimated pluvial climates 

of Nevada: Bulletin of the Nevada Bureau of Mines and Geology, v. 94, 37 

p.

Pearthree, P.A., 1990, Geomorphic analysis of young faulting and fault behavior 

in central Nevada: Tucson, Ariz., University of Arizona Ph.D. dissertation, 

212 p.

Reheis, M., 1999, Extent of Pleistocene lakes in the western Great Basin: U.S. 

Geological Survey Miscellaneous Field Studies Map MF–2323, scale 

1:800,000. 

Soil Survey Staff, 1975, Soil taxonomy: U.S. Department of Agriculture 

Handbook No. 436, 754 p.

Snyder, C.T., Hardman, G., and Zdenek, F.F., 1964, Pleistocene lakes in the 

Great Basin: U.S. Geological Survey Miscellaneous Geologic Investigations 

Map I–416, scale 1:1,000,000.

Stewart, J.H., Sarna-Wojcicki, A., Meyer, C.E., Starratt, S.W., and Wan, E., 

1999, Stratigraphy, tephrochronology, and structural setting of Miocene 

sedimentary rocks in the Middlegate area, west-central Nevada: U.S. 

Geological Survey Open-File Report 99–350, 1 plate, scale 1:24,000.

EH1

GEOLOGIC EVIDENCE FOR 

TRENCH LOGS

Michael N

1U.S. Geologic

U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY