Horned Lizard

trench site

Hanford 

Site

Yakima Training

Center

Johnson Canyon Mountains

Boylston

Badger Pocket

A

YAKIMA

KITTITAS

BENTON

GRANT

Ellensburg

Yakima

Frenchman Hills 

Saddle Mountains 

Umtanum Ridge

Manastash Ridge

Yakima Ridge

Rattlesnake Hills

Ahtanum Ridge

Saddle Mountains 

Kittitas Valley

Wenas Valley scarp

WANAPUM DAM

PRIEST RAPIDS

DAM

ROZA

 DIVERSION

DAM

Frenchman Hills Wasteway

Columbia

River

Wenas Creek

Naches River

Park Creek

Lower Crab Creek

46°30’

47°

120°30’ 120° 119°30’

0 5 10 KILOMETERS

Seattle

Ellensburg

Yakima

WASHINGTON

Columbia River

Snake River

STUDY

AREA

Columbia River

EXPLANATION

Fault—Modified from Washington 

State Department of Natural 

Resources, Division of Geology 

and Earth Resources (2010). 

Dashed where inferred

Fold—Modified from Washington 

State Department of Natural 

Resources, Division of Geology 

and Earth Resources (2010). 

Dashed where inferred

Scarp

Boundary of study area

Horned Lizard trench

County boundary

Boundary of U.S. Government 

facility—U.S. Army Yakima 

Training Facility or U.S. Department of Energy Hanford Site

120°21’00’’

46°58’30’’

46°58’00’’

46°57’30’’

120°20’30’’ 120°20’00’’ 120°19’30’’

Unlogged

trench Horned

Lizard 

trench

Boylston scarp

INTERSTATE 90

Park 

Creek

Warped channel

Boylston scarp

B

Figure 1. Maps showing study area and vicinity. A, Regional shaded-relief map of the Ellensburg-Yakima area of central Washington showing faults, folds, and other features mapped in the Yakima fold-and-thrust belt. See Sherrod and 

others (2013) for a description of the Wenas Valley scarp. B, Shaded-relief map generated from a lidar survey of the Boylston Mountains showing a northeast-trending scarp, the location of the Horned Lizard trench (solid red star), and the 

potential fault-generated deformation (double-headed white arrow) of Park Creek and its flood plain. Lidar data provided by the U.S. Army Yakima Training Center (2009).

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary 

between electronic plotters and between X and Y directions on the same plotter, and paper may change size 

due to atmospheric conditions; therefore, scale and proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 

1–888–ASK–USGS

Suggested citation: Barnett, E.A., Sherrod, B.L., Norris, Robert, and Gibbons, Douglas, 2013, Paleoseismology 

of a newly discovered scarp in the Yakima fold-and-thrust belt, Kittitas County, Washington: U.S. Geological 

Survey Scientific Investigations Map 3212. (Available at http://pubs.usgs.gov/sim/3212.)

Paleoseismology of a Newly Discovered Scarp in the Yakima Fold-and-Thrust Belt, Kittitas County, Washington

By

Elizabeth A. Barnett,1 Brian L. Sherrod,1 Robert Norris,1 and Douglas Gibbons2

2013

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3212

1

U.S. Geological Survey, Seattle, Wash.

2

University of Washington, Seattle, Wash.

? ? ?

n7

n8

n9

n10

n11 n2

n3

n4

n5

n12

n13

n14

n15

n6

n16b

n16a

n1

Figure 6

Figure 7

Figure 3

Figure 4 Figure 5

1 2 3 4 5

Meters

1

0

2

3

0

Meters

Northwest

1

0

2

3

Meters

6 7 8

Southeast

A

B

1fx

1v

1vw 4A

2s

3p

1cw

1c

2a

2x1

2x 1vx 2

2h

F1

F2

F3

Fx1

F3

F3

n12

4A

2s

2x2

3p

2h

2x1

2a

1cw

1c

1vx

1vw

1v

1fx

EXPLANATION 

[See table 2 for information on color, texture, and other features] 

Modern soil

Colluvium—Undeformed, overlies scarp

Colluvium—Associated with most recent earthquake

Buried soil—Bears distinctive prismatic structure

Colluvium—Found only northwest of fault F1. Incorporates clasts of unit 1v 

and possibly of eroded unit 3p

Colluvium—Associated with earthquake that predates development of unit 

3p, either syn-or post-depositional to underlying unit 2a

Colluvium—Colluvium associated with earthquake that predates development of unit 3p.

Weathered top of unit 1c (or paleo C-horizon)

Basalt—Brecciated, blocky, nonvesicular. Mapped as part of Grande Ronde 

Formation

Weathered, fractured unit 1v—Found adjacent to fault F1. Fractures are 

subparallel to F1

Weathered top of unit 1v (or paleo C-horizon)

Basalt—Fractured, brecciated, blocky, vesicular. Mapped as part of Grande 

Ronde Formation

Basalt—Jointed, fractured. Possible colonnade section of Grande Ronde 

Formation

Location of important feature—See numbered items in table 1 for detailed 

information about location

Contact

Fault—Arrows indicate sense of movement. Dashed where inferred or 

uncertain

Joint or fracture

Scan line along which joints and fractures were measured

Ash layer inferred from Mount St. Helens eruption in 1980

Prismatic soil structure in unit 3p

Cobbles and blocks

Nonvesicular cobble of unit 1fx, transported within deposit

Nonvesicular block of unit 1fx, in place

Vesicular cobble of unit 1v, transported within deposit

Vesicular block of unit 1v, in place

Figure 2. The Horned Lizard trench in the Boylston Mountains. The location of the trench excavation is shown in 

figure 1. A, Profile of the Horned Lizard trench stratigraphy. B, Photomosaic of the Horned Lizard trench.

Fx1

Figure 6

Figure 5 

Figure 7 Figure 3

Figure 4

1fx

1v

1vw

4A

2s

3p

1cw

1c

2a

2x1

2x2 1vx

2h

? ? ?

F1

F2

F3

 EXPLANATION

Poles to planes of joints, fractures, and faults

Joints measured along scan line (see figure 2A

for location) 

Fracture Fx1

Splay fracture of fracture Fx1

Plane measurements of fault F1

Fractures within unit 1vx subparallel and adjacent 

to fault F1

Trend, plunge, and pitch of striations measured on 

fault F1 surface

Trend and plunge

Pitch

A

B

fault F1

B

est fit of joints

Figure 8. Equal-area lower-hemisphere stereograms 

depicting structure data collected at Horned Lizard trench. 

A, Measurements of joints and fractures in unit 1fx taken 

along a scan line (orange dashed line in figure 2A). The 

near-vertical fault plane, measured on the fault surface, is 

shown in red (poles and planes). The magenta curve is the 

best-fit plane derived from the poles of joints measured in 

unit 1fx. This gently north-dipping plane is the inferred 

flow-top surface of the basalt bedrock. B, Measurements of 

gently southwest-plunging striations measured on the F1 

fault. The green line represents the fault surface on which 

the pitch was measured. An example of the striations is 

shown in figure 6. These grooves are moderately expressed 

on the fault surface. Stereograms were generated using 

Stereonet 6.3.3X (Allmendinger, 2002).

5 cm

3p

Figure 7. Photograph showing detail of prismatic soil structure in unit 3p. White arrow shows approximate vertical extent of prism structure. cm, 

centimeters. 5 cm

Figure 6. Photograph of nonvesicular blocks weathering out of a 

resistant matrix of brecciated unit 1c. cm, centimeters.

Figure 5. Photograph showing gently southwest-plunging 

striations (white arrow) on the surface of fault F1. 

Measurements are shown in figure 8. cm, centimeters.

20 cm

Figure 4. Photograph of resistant, vesicular blocks or rubble within a 

crumbling, weathered matrix (unit 1v). The morphology suggests that 

unit 1v might be either (1) the brecciated top or bottom of a flow or (2) 

the top or bottom of a brecciated flow that grades into the top of a 

simple flow top as brecciation and rubble decrease upward. cm, 

centimeters.

2 m

Figure 3. Photograph of aphanitic, nonvesicular 

basalt showing blocky jointing and fractures that 

define poorly formed polygonal columns and are 

characteristic of unit 1fx. The morphology suggests 

that this part of unit 1fx is a colonnade section of a 

flow. The orientations of the joints and fractures are 

represented in the stereogram in figure 8A. 

Structure data suggest that the flow dips gently to 

the northwest. White arrow and pink flags (in 

photograph) indicate through-going fracture, Fx1. 

Field of view is a little over 1 meter.

DISCUSSION

The Boylston Mountains anticlinal ridge is one of several that are cored by rocks of the 

Columbia River Basalt Group and, with the interceding synclinal valleys, constitute the Yakima 

fold-and-thrust belt of central Washington (fig. 1A) (Schuster, 1994; Schuster and others, 1997). 

Lidar data acquired from the U.S. Army’s Yakima Training Center reveal a prominent, 

northwest-side-up, 65°- to 70°-trending, 3- to 4-meter-high scarp that cuts across the western end 

of the Boylston Mountains, perpendicular to the mapped anticline (fig. 1B) (Blakely and others, 

2011). The scarp continues to the northeast from the ridge on the southern side of Park Creek and 

across the low ridges for a total length of about 3 kilometers. A small stream deeply incises its 

flood plain where it projects across Johnson Canyon (fig. 1B). 

In September 2010, two trenches were excavated across this scarp. The most informative of 

the two, the Horned Lizard trench (46.959N., 120.347W.) was measured and described in detail 

using a 0.5-square-meter grid (fig. 2) The Horned Lizard trench exposed a shallow basalt unit that 

was previously mapped as one of several flows making up the Grande Ronde Basalt by Schuster 

(1994); laboratory paleomagnetic analyses of oriented hand samples collected from the trench 

correlate this basalt unit with the youngest flow of the Grande Ronde Basalt: the informally named 

Museum flow of the Sentinel Bluffs Member (Reidel, 2005; Ray Wells and Jonathan Hagstrum, U.S. 

Geological Survey, written. commun., 2011), which is about 15.5 million years old (mega-annum, or 

Ma) (Swanson and others, 1979; Reidel and others, 1989). This study subdivides the flow into 

several descriptive, informal units (units 1cw, 1c, 1vx, 1vw, 1v, 1fx) (figs. 3–6), which are covered by 

a thin layer of cobbly, silty surface deposits that are less than 1 meter thick across the scarp. The 

trench excavation within the basalt revealed a deep, wide crack that is coincident with the base of the 

scarp and filled with wedges of silty gravels that are interpreted to represent at least two generations of fault colluvium (fig. 2). The crack is located between 5 and 6.5 meters on the grid shown 

in figure 2. The dark-brown, silty clay with a distinctive prismatic structure (unit 3p) (fig. 7) is 

interpreted to be a buried soil that developed on the surface of the oldest colluvial wedges (units 2a, 

2x1

). 

Subsequent faults (F) F1 and F2 truncated the soil and generated another wedge of colluvium 

(unit 2x2); thus, at least two events produced the stratigraphy exposed in the trench. By inference, the 

reverse motion on faults F1 and F3 ruptured the bedrock, although it is also possible that the rupture 

was the result of oblique motion recorded by gently southwest-dipping striations on the surface of 

fault F1 (fig. 8). The two units that were not deformed by the faulting—scarp colluvium (2s) and 

modern soil (4a)—drape the basalt, the colluvium-filled crack in the basalt, and the buried soil. 

Evidence constraining the age of faulting is poor; there was no material in the trench to constrain the 

ages for each rupture event except for the Grande Ronde Basalt, which has a maximum age of 15.5 

Ma. Fault F1 is here referred to as the Johnson Canyon fault and movement along it is inferred to be 

late Quaternary in age given the presence of the scarp on the modern landscape and the incised 

flood-plain sediments in Johnson Canyon that were apparently warped by reverse motion along the 

fault.

REFERENCES CITED

Allmendinger, R.W., 2002, Stereonet for Macintosh; Stereonet for Windows: Ithaca, N.Y., Cornell 

University, Department of Earth and Atmospheric Sciences, 42 p., available only online at 

http://softwarelibrary.geol.ucsb.edu/OSX/Applications-freeware/EarthSci/. (Accessed March 

26, 2012.)

Blakely, R.J., Sherrod, B.L., Weaver, C.S., Wells, R.E., Rohay, A.C., Barnett, E.A., and Knepprath, 

N.E., 2011, Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, 

Washington: Journal of Geophysical Research, v. 116, no. B07105, 33 p., 

doi:10.1029/2010JB008091.

Munsell Color, Inc., 2009, Munsell Soil Color Book: Grand Rapids, Mich., Munsell Color, Inc., not 

paginated.

Reidel, S.P., 2005, A lava flow without a source; the Cohassett flow and its compositional components, Sentinel Bluffs Member, Columbia River Basalt Group: Journal of Geology, v. 113, no. 1, 

p. 1–21. (Also available online at http://www.jstor.org/stable/10.1086/425966.)

Reidel, S.P., Tolan, T.L., Hooper, P.R., Beeson, M.H., Fecht, K.R., Bentley, R.D., and Anderson, J.L., 

1989, The Grande Ronde Basalt, Columbia; Stratigraphic descriptions and correlations in 

Washington, Oregon, and Idaho: Geological Society of America Special Paper 239, p. 21–53, 

33 p.

Schoeneberger, P.J., Wysocki, D.A., Benham, E.C., and Broderson, W.D., eds., 2002, Field book for 

describing and sampling soils (version 2.0): Lincoln, Nebr., Natural Resource Conservation 

Service, National Soil Survey Center, 228 p., available only online at 

http://soils.usda.gov/technical/fieldbook/.

Schuster, J.E., comp., 1994, Geologic map of the east half of the Yakima 1:100,000 quadrangle, 

Washington: Washington Division of Geology and Earth Resources Open File Report 94–12, 1 

sheet, 1:100,000 scale, 1 pamphlet, 19 p. (Also available online at 

http://www.dnr.wa.gov/ResearchScience/Pages/Publications.aspx.)

Schuster, J.E., Gulick, C.W., Reidel, S.P., Fecht, K.R., and Zurenko, Stephanie, 1997, Geologic map 

of Washington—Southeast quadrant: Washington Division of Geology and Earth Resources 

Geologic Map GM–45, 2 sheets, 1:250,000 scale, 1 pamphlet, 20 p. (Also available online at 

http://www.dnr.wa.gov/ResearchScience/Pages/Publications.aspx.)

Sherrod, B.L., Barnett, E.A., Knepprath, Nichole, and Foit, F.F., Jr., 2013, Paleoseismology across a 

possible scarp in the Yakima fold-and-thrust belt, Wenas Valley, Kittatas County, Washington: 

U.S. Geological Survey Scientific Investigations Map 3212, 1 sheet, available only online at 

http://pubs.usgs.gov/sim/3212/.

Swanson, D.A., Wright, T.L., Hooper, P.R., and Bentley, R.D., 1979, Revisions in stratigraphic 

nomenclature of the Columbia River Basalt Group: U.S. Geological Survey Bulletin 1457–G, 

59 p. (Also available online at http://pubs.er.usgs.gov/publication/b1457G.)

Washington State Department of Natural Resources, Division of Geology and Earth Resources, 2010, 

Digital geology of Washington State at 1:100,000 scale (version 3.0): Washington State Department of Natural Resources database available online at 

http://www.dnr.wa.gov/ResearchScience/Topics/GeosciencesData/Pages/gis_data.aspx/. 

(Accessed March 21, 2012.) 

1

For units 4A and 2s, two types of roots were present.

4A Clay loam 10 YR 5/3 (10 YR 4/3) Fine and very 

coarse

Common 

and few

Throughout 10 0 80 20 Angular to subangular Matrix None Granular Fine Moderate Loose Abrupt to 

clear

2s Wavy Tablet None apparent NA Soil developed after most recent earthquake deformation.

2s Silty clay 10 YR 4/3 (10 YR 3/3) Fine and very 

coarse

Common 

and few

Throughout 25–35 0 40 60 Angular to subangular 

(cobbles)

Subrounded (pebbles)

Matrix None Subangular 

blocky

Fine Moderate Soft Abrupt 2h or 3p Wavy Tablet None apparent NA Colluvium deposited following earthquake that pre-dates development of unit 

3p. Mixture of soil and cobbles filled void along fault surface between faults 

F1 and F3. Later cut by fault that truncates unit 3p and fault F2.

2x2 Silty clay 10 YR 5/4 (10 YR 4/4) Fine Few Throughout 15–20 0 30 70 Subangular to subrounded

Matrix None Subangular 

blocky

Very fine Moderate Moderately 

hard

Clear 2x1 Smooth Wedge None apparent NA Colluvium deposited between faults F1 and F2 following last earthquake that 

offset unit 3p. Contains mixture of units 2h and 2x1 .

3p (Too indurated to 

describe)

7.5 YR 4/4 (7.5 YR 3/3) Very fine to 

fine

Common Throughout 15 0 60 40 Subangular Matrix None Prismatic Fine Moderate Extremely 

hard

Abrupt 2x1

, 2a, 1cw Wavy Tablet Cut by fault F2, not found on hanging wall. Unit warped between 

faults F2 and F4

Good Distinctive prismatic soil formed on colluvial units 2a and 2x1 and on unit 3c. 

Absent on hanging wall; may have eroded from uplifted surface of hanging 

wall, or may have been incorporated into unit 2h. Merges with modern soil 

east of 8 meters on grid.

2h Silty clay 10 YR 5/4 (10 YR 4/3) Fine Few Throughout 20 0 20 80 Subangular to subrounded

Matrix None Subangular 

blocky

Very fine Weak Soft Clear 1v or 1vw Wavy Wedge Faulted by fault F1 at 5 meters, then 

possibly collapsed into fault zone 

and integrated into 2x1

Moderate Might be either scarp colluvium from an earthquake that predates unit 3p or 

former BC-horizon (dominant clast type is unit 1v). Truncated by fault F1.

2x1 Sandy clay loam 10 YR 6/4 (10 YR 5/4) Fine Few Throughout 15–20 0 30 70 Matrix None Granular Fine Moderate Slightly hard Abrupt 2a Smooth Wedge Cut by fault F2 Moderate Colluvium that predates unit 3p, deposited on unit 2a, cut by fault F2, and appears to have been dragged along surface of fault F1 as a thin string of rubble.

2a Sandy clay loam 10 YR 6/6 (7.5 YR 4/6) Very fine to 

fine

Few Matted around rock 

fragments

35–40 < 1 40 60 Subangular Matrix None Subangular 

blocky

Fine Weak Very hard Abrupt 1c Smooth Wedge Deposited possibly syndepositionally with the rupture of fault F3Moderate to 

good

Deposited as colluvium following earthquake that predates development of unit 

3p.

1cw Regolith 10 YR 6/6 Fine Few Matted on surface 20 0 50 50 Subangular to subrounded

Matrix None Granular Fine Weak Moderately 

hard

Clear 1c Smooth Tablet Cut by fault F3 Good Weathered top of unit 1c.

1c Basalt 10 YR 7/3 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Faulted by faults F1 and F3, which 

are likely joined at depth

Good Basalt flow of Miocene Grande Ronde Formation.

1vx Basalt 10 YR 5/4 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Faulted by fault F1 Good Basalt flow of Miocene Grande Ronde Formation.

1vw Basalt 10 YR 4/3 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA None apparent NA Basalt flow of Miocene Grande Ronde Formation.

1v Basalt 10 YR 7/4 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Faulted by fault F1 and possibly by 

fault F4

NA Basalt flow of Miocene Grande Ronde Formation.

1fx Basalt 10 YR 7/4 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Possibly faulted by fault F4 NA Basalt flow of Miocene Grande Ronde Formation.

Unit (see

 figure 2A) Texture Color for dry surface  (moist surface)

Roots1 Clast descriptions

Stratification

Soil-horizon features Lower contacts Postdeposition deformation

Unit genesis and interpretation Size Quantity Location

Total 

area 

(percent)

Boulders 

(percent 

of unit)

Cobbles 

(percent 

of unit)

Pebbles 

(percent 

of unit)

Angularity Support Structure Size Distinctness

Rupture 

resistance 

(dry)

Distinctness Underlying 

unit(s)

Unit surface 

topography

Unit surface 

shape Type Distinctness

Matrix None 2s

Table 2. Description of units in trench.

[Color terminology is taken from Munsell Color, Inc. (2002). Terminology regarding texture, roots, clasts, soil-horizon features, and distictness of contacts is taken from 

Schoneberger and others (2002). NA, not available; <, less than]

Note

number

 (see

 fig. 2A)

Note

number

 (see

 fig. 2A)

Description Description

n1 Possible light-gray ash from 1980 Mount St. Helens eruption in unit 4A (see table 2 

for description).

n2 Clast count in unit 2s yielded 35 of 35 unit 1fx clasts and 0 of 35 unit 1v clasts.

n3 Contact between 2x weakly defined; primarily based on color and texture 2

 and 2x1

change.

n4 Soil prisms developed between clasts do not exceed 5 to 8 centimeters in height. 

Fresh surfaces are waxy, smooth, and slightly opalescent.

n5 Surface of unit 1c stained white by caliche.

n6 Units 

coordinates (observation point is below trench profile).

1v and 1c separated by fault F1 approximately located below the 5.25, 0 grid 

n7 Fracture extends from trench floor to base of unit Fx1 4A.

n8 Sharp contact between units 1fx and 1v along base of through-going fracture Fx1.

n9 Modern soil, 4A, thickens and colluvium starts downslope of fracture Fx1.

n10 Highly vesicular blocks weather out of unit 1v.

n11 Spatial density of basalt vesicles within blocks decreases upward.

n12 Nonvesicular blocks weather out of unit 1c, causing brecciated appearance of 

surface.

n13 Fault contact between units 3p and 2x2 is abrupt; distinct color, soil texture, and 

weakly defined, possibly due to unit

structure change (see table 2).

n14 Contact between units 2x2

 and 2h 2h material 

that was remobilized during faulting and redeposited as 2x2.

n15 Possible slickenlines on fault 

surface is weak to moderate. Orientations are shown in figure 8.

F1 surface. Quality of striation visibility on fault 

n16(a,b) Fractures in unit 1cx subparallel to fault F1. Measurements are shown in figure 8.

Table 1. Notes indicated on log (figure 2A). Table 1. —Continued