2011

U.S. Department of the Interior

U.S. Geological Survey

Lidar-Revised Geologic Map of the Wildcat Lake 7.5’

Quadrangle, Kitsap and Mason Counties, Washington

By Rowland W. Tabor, Ralph A. Haugerud, Peter J. Haeussler, and Kenneth P. Clark

Pamphlet to accompany

Scientific Investigations Map 3187
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Viginia: 2011

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Suggested citation:

Tabor, R.W., Haugerud, R.A., Haeussler, P.J., and Clark, K.P., 2011, Lidar-revised geologic map of the Wildcat 

Lake 7.5’ quadrangle, Kitsap and Mason Counties, Washington: U.S. Geological Survey Scientific Investigations Map 3187, scale 1:24,000, 12 p., and GIS data, available at http://pubs.usgs.gov/sim/3187/.

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i

Contents

Introduction ....................................................................................................................................................1

Base Map Issues .................................................................................................................................1

Lineaments ............................................................................................................................................1

Geologic Units ......................................................................................................................................1

Cross Section ........................................................................................................................................1

Previous Work ......................................................................................................................................1

Acknowledgments ...............................................................................................................................1

Geologic Summary ........................................................................................................................................2

Regional Geologic Setting ..................................................................................................................2

Location of the Seattle Fault ..............................................................................................................2

Stratigraphy ..........................................................................................................................................2

Tertiary Bedrock...........................................................................................................................2

Unconsolidated Deposits ..........................................................................................................3

Glacial and Interglacial Deposits ....................................................................................3

Post-glacial Deposits ........................................................................................................6

Structural History .................................................................................................................................6

Description of Map Units .............................................................................................................................7

Unconsolidated Deposits ...................................................................................................................7

Postglacial Deposits ...................................................................................................................7

Glacial and Interglacial Deposits .............................................................................................8

Bedrock .................................................................................................................................................9

Stratified Rocks ...........................................................................................................................9

Intrusive Rocks .....................................................................................................................................9

References Cited .........................................................................................................................................10

Figures

1. Map showing positions of Puget Lobe termini during deposition of terraces graded to 

Pleistocene Lake Russell. ..............................................................................................................4

2. Profiles of deformed outwash terraces (Qvrt1–7) along Tahuya River and Big Beef Creek. ....5

3. Kamb-contoured plot of poles to dikes of diabase and basalt. ........................................................6
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1

Introduction

This map is an interpretation of a 6-ft-resolution (2-m-resolution) lidar (light detection and ranging) digital elevation 

model combined with the geology depicted on the Geologic 

Map of the Wildcat Lake 7.5′ quadrangle, Kitsap and Mason 

Counties, Washington (Haeussler and Clark, 2000). Haeussler 

and Clark described, interpreted, and located the geology on 

the 1:24,000-scale topographic map of the Wildcat Lake 7.5′ 

quadrangle. This map, derived from 1951 aerial photographs, 

has 20-ft contours, nominal horizontal resolution of approximately 40 ft (12 m), and nominal mean vertical accuracy of 

approximately 10 ft (3 m). Similar to many geologic maps, 

much of the geology in the Haeussler and Clark (2000) map—

especially the distribution of surficial deposits—was interpreted 

from landforms portrayed on the topographic map. In 2001, the 

Puget Sound lidar Consortium obtained a lidar-derived digital 

elevation model (DEM) for Kitsap Peninsula including all of the 

Wildcat Lake 7.5′ quadrangle. This new DEM has a horizontal 

resolution of 6 ft (2 m) and a mean vertical accuracy of about 

1 ft (0.3 m). The greater resolution and accuracy of the lidar 

DEM compared to topography constructed from air photo stereo 

models have much improved the interpretation of geology in 

this heavily vegetated landscape, especially the distribution and 

relative age of some surficial deposits. Many contacts of surficial deposits are adapted unmodified or slightly modified from 

Haugerud (2009). For a brief description of lidar and this data 

acquisition program, see Haugerud and others (2003).

Base Map Issues

The positions of geographic features on the old contour 

base of the Wildcat Lake quadrangle compared to the same 

features on the DEM are displaced by as much as 1,000 ft (300 

m). For this reason, contacts adopted directly from Haeussler 

and Clark (2000) are shown as approximately located. We 

reproduced structural data and locations of dikes directly from 

Haeussler and Clark (2000) but moved a few locations slightly 

to accommodate the revised base map. 

No digital depiction of stream or road locations that 

adequately matches the DEM exists, so we digitized both from 

the DEM. Many logging roads that are visible on the DEM may 

not be maintained and are not shown on other large-scale road 

maps. Consequently, we primarily referred to 1:100,000-scale 

road depictions and Google Earth to select roads that are shown 

on this map. We selected rivers and streams to digitize based on 

drainage shown on the Wildcat Lake 1:24,000 topographic map.

Lineaments

We have shown several conspicuous northeast-trending 

topographic lineaments on Gold Mountain, mostly in massive 

Eocene subaerial basalt flows (Tcb) with moderate southwest 

dips. The westernmost of these lineaments is, in part, coincident 

with an originally mapped contact between the subaerial basalt 

(Tcb) and submarine basalt (Tcbs). We have shown this lineament to be a probable fault.

Geologic Units

We did no additional field work to make this revised map. 

We revised the extent of bedrock outcrops based on geomorphic 

interpretation of the DEM. We accepted most of the original 

interpretations of the bedrock geology. We refined locations 

for a few lengthy buried faults and moved them slightly to 

accommodate changes in the bedrock extent. Based on recently 

aquired geophysical data (A.P. Lamb, written commun., 2010), 

we relocated the buried Seattle Fault.

We extensively reinterpreted contacts, stratigraphy, and age 

(geologic time scale of Gradstein and others, 2004) of unconsolidated deposits. Our additional mapping is explained in the 

Description of Map Units and in the discussion in the Surficial 

Geology section. Much of the text is adapted from Haeussler 

and Clark (2000).

Cross Section

The topographic profile for the cross section A–A′, as 

well as contacts of revised units, has been redrawn to match 

the DEM. We copied the interpretation of subsurface bedrock 

directly from Haeussler and Clark (2000), except on the north 

end where the shift in position of the Seattle Fault required 

interpretive changes.

Previous Work

Geologic mapping within and adjacent to the quadrangle 

began with Willis (1898) and Willis and Smith (1899), who 

described glacial deposits in Puget Sound. Weaver (1937) correlated volcanic rocks in the quadrangle to the Eocene Metchosin Volcanics on Vancouver Island. Sceva (1957), Garling and 

others (1965), and Deeter (1978) all focused on mapping and 

understanding the Quaternary stratigraphy of the Kitsap Peninsula, but they also examined bedrock in the quadrangle. Reeve 

(1979) was the first to examine the igneous rocks on Green 

and Gold Mountains in some detail. Clark (1989) mapped soon 

after extensive logging on the mountains and, with greater rock 

exposure, significantly improved Reeve’s work.

Yount and Gower (1991) published a bedrock geologic 

map of the Seattle quadrangle, which includes the Wildcat Lake 

7.5′ quadrangle. Yount and others (1993) published a surficial 

geologic map of the Seattle 30′ by 60′ quadrangle.

Haeussler mapped the surficial geology in the spring and 

summer of 1998 and in the winter of 1999. Haeussler and Clark 

(2000) combines Haeussler’s mapping and Clark’s (1989) 

essentially unchanged mapping. Haugerud (2009) mapped 

geomorphic units of about 90 percent of the Wildcat Lake quadrangle as part of a regional geomorphic map of Kitsap County; 

much of his mapping is incorporated here.

Acknowledgments

We thank Derek Booth and Elizabeth Barnett for very helpful reviews, and we gained much from discussion with Trevor 

Contreras, Andy Lamb, Jeff Tepper, and Ray Wells.
2

Geologic Summary

Regional Geologic Setting

The Wildcat Lake quadrangle lies in the forearc of the Cascadia Subduction Zone, about 15 mi (20 km) east of the Cascadia accretionary complex exposed in the Olympic Mountains 

(Tabor and Cady, 1978b) and about 60 mi (100 km) west of the 

axis of the Cascades Volcanic Arc. The quadrangle lies near the 

middle of the Puget Lowland, which typically has elevations 

less than 600 ft (180 m), but on Gold Mountain, in the center of 

the quadrangle, elevation rises to 1,761 ft (537 m).

Rocks of the Coast Range basalt terrane that extends from 

southern Oregon to southern Vancouver Island are exposed on 

Green and Gold Mountains. This terrane consists of Eocene 

submarine and subaerial tholeiitic basalt of the Crescent 

Formation, which probably accreted to the continental margin 

in Eocene time (Snavely and others, 1968). The Coast Range 

basalt terrane may have originated as an oceanic plateau or 

extruded during oblique marginal rifting (Babcock and others, 

1992), but its subsequent emplacement history is complex. In 

southern Oregon, onlapping strata require accretion to have 

occurred by 50 Ma (Wells and others, 1984). However, studies 

on southern Vancouver Island suggest that accretion to North 

America occurred sometime between 42 and 24 Ma (Brandon 

and Vance, 1992).

After emplacement of the Coast Range basalt terrane, the 

Cascadia accretionary complex, exposed in the Olympic Mountains west of the quadrangle, developed when younger marine 

sedimentary rocks were thrust beneath the older basalt terrane 

(Tabor and Cady, 1978b; Clowes and others, 1987). Domal 

uplift of the accretionary complex beneath the Olympic Mountains initiated after ~18 m.y. (Brandon and others, 1998).

The Seattle Basin, part of which lies to the north of Green 

Mountain, may have begun to develop in late Eocene time due 

to flexural subsidence forced by displacement along the Seattle 

Fault Zone (Johnson and others, 1994); however, ten Brink and 

others (2002) suggest motion on the Seattle Fault, and flexural 

subsidence of the Seattle Basin did not begin until mid-Miocene 

time.

The Puget Lobe of the Cordilleran Ice Sheet covered the 

quadrangle during the Vashon stade of the Fraser Glaciation of 

Armstrong and others (1965). Two-thirds of the quadrangle is 

underlain by deposits of this glaciation, which lasted from about 

15 ka to 13 ka.

Location of the Seattle Fault

Geophysical studies and regional mapping indicate that the 

Seattle Fault lies north of Green Mountain. This fault produced 

a large earthquake about 1,100 years ago and may pose a 

significant earthquake hazard to the Seattle-Tacoma urban area 

(Bucknam and others, 1992; Atwater and Moore, 1992; Karlin 

and Abella, 1992; Schuster and others, 1992; Jacoby and others, 

1992; Pratt and others, 1997; Blakely and others, 2002; A.P. 

Lamb, written commun., 2010).

The field mapping by Haeussler and Clark (2000), however, revealed no evidence of Holocene faulting in the Wildcat 

Lake quadrangle. Projection from known surface ruptures east 

of the quadrangle, geophysical data (Blakely and others, 2002), 

and seismic reflection profiles (A.P. Lamb, written commun., 

2010) allow the likely position of the Seattle Fault within the 

Wildcat Lake quadrangle to be defined fairly closely. The lidar 

DEM shows no fault scarps in the vicinity of the fault. A broad 

warp of a Vashon-age glacial outwash terrace south of the projected fault location suggests that the Seattle Fault is active at 

depth but does not reach the surface. See the discussions in the 

sections on Unconsolidated Deposits and Structural History.

Stratigraphy

Tertiary Bedrock

Lithology, chemistry, and age led Clark (1989) and Haeussler and Clark (2000) to assign the volcanic and volcaniclastic 

rocks of Green and Gold Mountains to the Crescent Formation 

exposed on the Olympic Peninsula to the northwest, west, and 

southwest (Arnold, 1906; Tabor and Cady, 1978a). Clark (1989) 

compared subaerial volcanic rocks of the Crescent Formation 

on Green and Gold Mountains (unit Tcb) to the lower and upper 

Crescent Formation on the Olympic Peninsula. The average 

subaerial flow thickness of about 30 ft (9 m) at Green and Gold 

Mountains is thinner than in measured sections of the Crescent 

Formation on the flanks of the Olympic Mountains, where flows 

measure 100–200 ft (30–50 m) thick. Vesicles in basalt in the 

Green and Gold Mountains area are much larger (3 in [7 cm]) 

than the largest vesicles (<2 in [4 cm]) in the Crescent Formation in the measured sections. Both rock units are subalkaline 

and tholeiitic, and both have minor and trace elements that plot 

in the same fields on discriminant diagrams.

The rock column exposed on Green and Gold Mountains, 

referred to as the “Bremerton rocks” by Clark (1989), is simlar 

to an ophiolite sequence: from bottom to top, basal gabbro, a 

locally sheeted dike complex, submarine basalts and volcaniclastic rocks, and subaerial basalt flows. Clark (1989) found 

more than 200 ft (60 m) of basal leucogabbro and pegmatoid 

(unit Teg). The upper part of this unit is intruded by numerous diabase and basaltic dikes, which Clark (1989) mapped 

separately (unit Tegd). The overlying sheeted dike complex 

is approximately 500 ft (150 m) thick and entirely consists of 

dikes of diabase and basalt (unit Ted). The submarine volcanic 

unit (Tcbs) consists of basalt flows interbedded with basaltic 

sandstone, siltstone, tuffs, and basaltic breccia. Overlying the 

submarine volcanic unit, subaerial basalt flows (unit Tcb) are 

more than 600 ft (180 m) thick. Trace-element data from these 

intrusive and extrusive rocks are similar, which suggests that 

they are related (Clark, 1989).

Clark (1989) indicated that the sequence differs from an 

idealized ophiolite stratigraphy in several important ways: (1) it 

lacks a basal ultramafic complex, (2) the Green and Gold Mountain dike complex has a thickness of about 500 ft (150 m) in 

contrast to more than 0.5 mi (~1 km) of sheeted dikes in typical 

oceanic crust, (3) the dikes are not ubiquitously sheeted, and (4) 

the Green and Gold Mountain sequence is capped by subaerial 

basalt, whereas most ophiolites are overlain by deep marine 
3

sediments. Clark (1989) found that the geochemistry of the 

gabbro and basalts is transitional between normal mid-oceanridge basalt (MORB) and enriched oceanic island basalt.

Preliminary modeling of aeromagnetic and gravity data 

over Green and Gold Mountains (Haeussler and others, 2000) 

indicates highly magnetic, dense rocks within a few kilometers 

of the surface beneath Green and Gold Mountains. A basal ultramafic complex may lie beneath Clark’s (1989) Bremerton rocks. 

Despite the differences between the Green and Gold Mountains 

rocks and ophiolites, the presence of the dike section on Green 

and Gold Mountains and the overall similarity to ophiolite layering indicate that this quasi-ophiolite formed in an extensional 

environment.

Duncan (1982) dated samples from three basalt flows 

along the northwest shore of Sinclair Inlet, southeast of Bremerton and east of the Wildcat Lake quadrangle. Whole-rock K-Ar 

ages range between 43.3±0.5 and 49.2±0.6 Ma. However, 

two of the samples, re-analyzed with the 40Ar/39Ar method, 

yielded whole-rock total-fusion ages of 51.7±2.4 and 55.3±3.1 

Ma. Duncan (1982) also step-heated a whole-rock split that 

produced a 55.4±3.2 Ma age. Two 40Ar/39Ar total-fusion ages 

on one sample of leucogabbro are 50.4±0.6 Ma and 49.2±0.8 

Ma (Clark, 1989). Zircon from leucogabbro (unit Teg) at the 

base of Green Mountain has a 206Pb/238 U age of 50.5±0.6 Ma 

(early Eocene; Haeussler and others, 2000). This precise zircon 

age provides a useful younger limit for the age of the Crescent 

Formation in this area.

These geochronologic results are consistent with fossil 

ages from elsewhere in northwestern Washington, which 

indicates that the Crescent Formation is as old as 53 Ma and is 

unlikely to be younger than 46 Ma. Calcareous nannoplankton 

from sedimentary rocks interbedded with submarine basalt at 

Bon Jon Pass, 33 km northwest of the Wildcat Lake quadrangle, 

were referred to zone CP11 (about 53 Ma, see Gradstein and 

others, 2004) by D. Bukry (written commun., 1998; in Tabor 

and others, 2011). In the Uncas 7.5′ quadrangle, east of Bon Jon 

Pass, subaerial basalts of the Crescent Formation are overlain 

by Aldwell Formation that contains benthic foraminifera and 

mollusks of upper Ulatisian to lower Narizian ages (Spencer, 

1984). East of the Uncas quadrangle, submarine deposits of the 

Crescent Formation have Ulatisian-age foraminifera (Yount and 

Gower, 1991). Prothero (2001) reports that the base of the Ulatisian may be as old as 51 Ma and that the top of the Ulatisian 

may be as young as 46 Ma. Gradstein and others (2004) place 

the early to middle Eocene (Ypresian-Lutetian) boundary at 

48.6 Ma.

Dacite dikes (unit Tad, purple dike symbol on map) are 

the youngest bedrock unit. These dikes cut all other rock units. 

Clark (1989) reported geochemical data from one sample that 

has extremely low Ti, low P, high Zr relative to Nb, and very 

low Cr. This trace-element signature is consistent with a high 

degree of partial melting. Clark (1989) concluded, based on 

this chemistry and crosscutting relations, that the dikes are not 

related to the other rock types on Green and Gold Mountains. 

More recent work (Tepper and others, 2004) confirms Clark’s 

conclusions. The dikes are adakites (hornblende dacites) that 

are evidently associated with a subduction regime that preceded 

establishment of the modern Cascade Volcanic Arc. 40Ar/39Ar 

dating of dike samples by the New Mexico Geochronology 

Research Laboratory (Esser, 2003) produced ages of 47.8±0.4 

and 46.6±1.4 Ma.

Unconsolidated Deposits

Glacial and Interglacial Deposits

Pre-Vashon stade deposits are not shown on this map, but 

geologic mapping in the Holly 7.5′ quadrangle to the west, by 

Trevor Contreras (written commun., 2011) of the Washington Department of Natural Resources, Division of Geology 

and Earth Resources, indicates that older glacial deposits are 

exposed in Stavis Creek valley in the northwest corner of the 

Wildcat Lake quadrangle. Similar pre-Vashon stade deposits are 

probably exposed in the canyon of Big Beef Creek, northeast of 

Lake William Symington.

Deposits of the last glaciation—the Vashon stade of the 

Fraser glaciation of Armstrong and others (1965)—surround 

the Tertiary bedrock highs of Green and Gold Mountains. The 

Vashon ice sheet first covered the study area about 17,400 cal 

yr B.P., reached its maximum extent around 16,950 cal yr B.P. 

(Porter and Swanson, 1998), and covered the area with as much 

as 3,000 ft (900 m) of ice (Booth, 1987).

As the ice sheet advanced south of Port Townsend, it 

blocked northward drainage from the Puget Lowland and 

formed proglacial lakes that drained southward into the Chehalis River and then to the Pacific Ocean. There are no outcrops of 

the sediments deposited in these advance lakes within the quadrangle, even among the lowest exposures along Big Beef and 

Stavis Creeks. However, we infer that clay that was encountered 

in boreholes at the Olympic View Sanitary Landfill, south of 

Barney White Ranch along the southeast edge of the quadrangle, was deposited as proglacial lake sediments of early Vashon 

age. This clay lies approximately at sea level and is overlain 

by sandy and gravelly advance outwash (unit Qva) deposited 

by streams issuing from the front of the advancing ice sheet. 

Excellent exposures of advance outwash can be seen along a 

road leading down to Big Beef Creek northwest of Wildcat 

Lake. A foreset-topset transition is visible several meters above 

the level of the creek. Farther up the section, sand and gravel 

was deposited as debris flows that show poor to no sorting but 

a weak alignment of clasts. The percentage of cobbles in the 

debris flows appears to generally increase up section.

Till (unit Qvt) mantles most upland surfaces and marks 

the presence of the ice sheet in the study area. Till on Green 

Mountain reaches elevations up to 1,350 ft (410 m). Ice overrode both Green and Gold Mountains, rounding the mountain 

tops and scouring deep grooves. Green and Gold Mountains 

also deflected the ice sheet. Linear ridges and grooves on the 

till plain north and northwest of the mountains trend southwest, 

but farther east they tend to fan eastward. These trends are more 

obvious on a regional scale than on the Wildcat Lake quadrangle (see Haugerud, 2009). South of the mountains, the glacial 

grooves fan east and west, demonstrating the diversion of ice 

flow around the massif. Granitic clasts within the till attest to a 

source at least 95 mi (150 km) north in the Coast Mountains of 

British Columbia.
4

The Puget lobe rapidly retreated from its maximum extent, 

leaving the Wildcat Lake quadrangle ice free by about 16,500 

cal yr B.P. (Porter and Swanson, 1998). Consideration of likely 

ice-surface slopes and the distribution of outwash and icecontact features allow us to outline successive margins of the 

receding ice (fig. 1). During ice retreat, a series of recessional 

proglacial lakes formed. The largest of these, ancient glacial 

Lake Russell (Bretz, 1913), drained south to the Chehalis River 

(Thorson 1979, 1980; Waitt and Thorson, 1983). Silt and clay 

(unit Qvrl) near the Union River was deposited in Lake Russell. At least 20 large deltas were built out into Lake Russell 

(Thorson, 1980), and one of these deltas is located in the southeastern part of the map area. A foreset-topset transition within 

these recessional outwash sands and gravels (unit Qvru1) at a 

Qvrw1-Qvrw 2 

and Qvrs1-Qvrs 3

Qvrt1-Qvrt4 

Qvrt5-Qvrt7

and Qvru1-Qvru2

Qvrb1-Qvrb3

Sinclair Inlet

OUTWASH DEPOSITS

Qvr1-Qvr3

Qvrc1-Qvrc2

Bremerton

National

Airport

Union

River

River

East

Fork

Union

Bear

Creek

Creek

Creek

Creek

Seabeck

Big

Beef

Creek

Big

Tin

Mine

Creek

Creek Lost

Panther

 Lake

Union

River Reservoir

Wildcat Lake

William

 Symington Lake

Tahuya Lake

Camp Union

Green

Mountain

M o u n t a i n

G o l d

McKenna Falls

Gold

Creek

Beef

Creek

Dyes Inlet

Chico Bay

Ostrich Bay

Chico

Creek

Kitsap Lake

Tahuya

River

Mission

Stavis

Bay

Seabeck

Bay

Stavis

mountainous bedrock terrane

Hood Canal

Mission L.

Tiger Lake

Hazel Creek

Qvrt1-Qvrt4 

Early

Bear Cr.

 Qvrc1-Qvrc2

Qvrb1-Qvrb3

tributary

and Qvr1-Qvr3 (subglacial)

Qvrw1-Qvrw2 and Qvrs1-Qvrs3

Qvrt1-Qvrt4 

Qvt5-Qvrt7 and Qvru1-Qvru2

STAGNANT

ICE

AREA

Figure 1. Map showing positions of Puget Lobe termini (heavy colored lines) during deposition of terraces 

graded to Pleistocene Lake Russell. Dotted lines outline areas of ice-contact features indicating stagnant 

ice. Terraces and stagnant ice shown beyond the Wildcat quadrangle boundary (solid black outline) are 

generalized from Haugerud (2009). Qvrw1–Qvrw2, west, probably subglacial, outwash units 1–2; Qvrs1–

Qvrs3, southwest, possibly subglacial, outwash units 1–3; Qvrt1–Qvrt4, recessional outwash in higher 

terraces of Tahuya River and Big Beef and Mission Creeks, Big Beef-Tahuya-Mission outwash units 1–4; 

Qvrt5–Qvrt7, recessional outwash in lower terraces of Tahuya River and Big Beef Creek, Tahuya River 

outwash units 5–7; Qvru1–Qvru2, recessional outwash terraces in Union River area, Union River outwash units 1–2; Qvrb1–Qvrb3, recessional outwash terraces above lower Big Beef Creek, Big Beef Creek 

outwash units 1–3; Qvr1–Qvr3,recessional, probably subglacial, outwash deposits south of Wildcat Creek, 

outwash units 1–3; Qvrc1–Qvrc2, recessional outwash deposits along Chico Creek, Chico Creek outwash 

units 1–2.
5

quarry near McKenna Falls indicates that the shoreline elevation of Lake Russell at the time of deposition was 314 ft (95.7 

m) (Thorson, 1989). Because of subsequent glacioisostatic 

rebound, the former shoreline is probably at higher elevations 

farther north. Haeussler and Clark (2000) indicate that the 

contact between the recessional lake deposits (unit Qvrl) and 

the deltaic sand and gravel deposits (units Qvru1, Qvru2) is 

gradational.

We mapped subdued landslide-like features near the East 

Fork Union River at elevations below the shoreline elevation of 

Lake Russell as sublacustrine landslides (unit Qvls). Similarly, 

we interpreted a fan-shaped deposit east of the East Fork to be 

a sublacustrine fan (unit Qvlf). Topography suggests that most 

material mapped as lake deposits in Haeussler and Clark (2000) 

is overlain by alluvium, and we show it on this map as unit Qa.

Interpretation of the DEM reveals scattered alluvial surfaces throughout the quadrangle that mostly form terraces, and 

these are cut into or mantled by Vashon-age recessional outwash 

graded to Lake Russell. Combining the sequences and locations 

of the terraces with probable drainage paths during ice retreat 

allows reconstruction of probable ice-front locations across the 

quadrangle (fig. 1). We assigned ages to the recessional terraces 

on the basis of their elevation: the highest recessional terraces 

in any one drainage must be the oldest in that drainage. We 

assumed that the coeval ice front was not too far east or north of 

any particular group of terraces; in other words, if none of this 

particular group of terraces can be identified farther upstream, 

then they were not formed there. If some of the mapped recessional outwash were deposited subglacially—though the flat top 

surfaces and adjacent cutbanks on many terraces argue against 

this—then the ice front could have been farther downstream 

than we have shown it.

The oldest recessional outwash graded to Lake Russell 

on this map occurs on a ridge above the Tahuya River on the 

west edge of the quadrangle (units Qvrw1, Qvrw2). West of the 

quadrangle, these deposits fill a sinuous channel that crosscuts 

the regional ice striations (fig. 1; Haugerud, 2009). This channel 

is a typical landform produced by subglacial erosion (Booth and 

Hallet, 1993). Outwash units Qvrw1 and Qvrw2 were deposited subglacially or shortly after the glacier retreated from the 

channel. Southeast of the Tahuya River, units Qvrs1, Qvrs2, 

and Qvrs3 also fill a sinuous channel, but one that parallels the 

regional ice striations. The glacier margin must have been very 

close to the channel’s head or, more likely, this channel also is 

of subglacial origin. Units Qvrs1, Qvrs2, and Qvrs3 are truncated by younger outwash in the Tahuya River valley. 

The most extensive terraces graded to Lake Russell (units 

Qvrt1–Qvrt7) are in and along Tahuya River and upper Big 

Beef Creek. Projecting terrace elevations onto a north-south 

vertical plane (fig. 2) facilitates separation and correlation of 

terrace levels. The almost continuous surface of Qvrt7 rises 

northward from the southwest border of the quadrangle to reach 

a broad divide at the head of the Tahuya River, at an elevation 

of about 490 ft (150 m), where it continues down along Big 

Beef Creek to a minimum elevation of about 400 ft (132 m). 

Older terraces (units Qvrt1–Qvrt6) show this same pattern at 

a higher level, albeit not continuously. These terraces appear 

to have been formed by meltwater draining south from the ice 

front near Sprague Pond and subsequently folded. Formation 

of the upper Big Beef Creek terraces by north-flowing drainage 

seems unlikely, because the ice front was far to the northeast 

and unable to supply meltwater to this area by the time upper 

Big Beef Creek was ice free. If the upper Big Beef Creek terraces were formed subglacially, their northward slope could be 

primary, but we expect subglacial channels to be undulating in 

profile and to lack distinct breaks in slope at the channel margins, unlike the smoothly sloped, sharply bounded surfaces of 

unit Qvrt7 and some of the older terraces (units Qvrt1–Qvrt4). 

10 5

Black Lake datum - 1m/km

Kilometers north

Meters NAVD88

Tahuya River Big Beef Creek

23 m

Minimum

differential

uplift

APPROXIMATE

PROJECTION OF

THE SEATTLE FAULT

160

120

80

160

140

Qvrt7

Qvrt6

A

B

C

S N

Qvrt1 Qvrt1

160

120

Qvrt6

Figure 2. Profiles of deformed outwash terraces (Qvrt1–7) along Tahuya River and Big Beef Creek. Terrace DEM elevation points projected onto a north-south vertical plane. Frequency of elevation points are 

color coded: red, highest frequency. The spread of points vertically represents irregularities in terrace surface, inaccurate lidar data, and misidentification of terraces. A, composite plot of all Qvrt terrace surfaces 

(Qvrt1 labeled); B = Qvrt6; C = Qvrt7.
6

We discuss the significance of this young fold in the section on 

Structural History.

As the ice front retreated, it cleared the drainage of Bear 

Creek before the upper reaches of Union River and Hazel Creek 

were free of ice or a recessional lake. One prominent northeast 

tributary of Bear Creek grew to include upper Hazel Creek. 

Lower Hazel Creek was still ice covered, but after further 

retreat, lower Hazel Creek developed and was able to capture 

the upper headwaters of the Bear Creek tributary (fig. 1). 

The exact origins of outwash terraces associated with 

lower Big Beef and Wildcat Creeks in the northeastern part of 

the quadrangle are somewhat problematic. After the ice receded 

from lower Big Beef Creek, the outwash drained through it to 

Hood Canal, depositing units such as Qvrb1–Qvrb3 (fig. 1). 

The outwash deposits of units Qvr1–Qvr3 could have formed 

subglacially as suggested by the sinuous channel draining into 

Lost Creek. When Chico Creek was free of ice, terraces Qvrc1–

Qvrc2 could have been built.

Near McKenna Falls, on the southeast flank of Gold 

Mountain, recessional sediments (units Qvru1–Qvru2) form 

a delta that was built out into Lake Russell. Thorson (1989) 

calculated postglacial isostatic rebound at McKenna Falls to be 

about 161 ft (49 m) by subtracting the elevation of the Black 

Lake spillway (153 ft [46.7 m]) from the current elevation of 

the topset-foreset transition (314 ft [95.7 m]).

Post-glacial Deposits

Alluvial deposits mapped as Holocene and Pleistocene 

(unit Qoa) are scattered across the quadrangle. A sequence of 

terraces (units Qoa1–Qoa6) in Stavis Creek appears to have 

been graded to Pleistocene Lake Bretz. Small terraces in the 

canyon of Big Beef Creek may also have been graded to Lake 

Bretz. Note that terrace deposits are numbered sequentially 

within each drainage, thus Qoa1 in Stavis Creek may not be the 

same age as Qoa1 in Big Beef Creek.

The modern depositional environment includes alluvium 

(unit Qa), wetland deposits (unit Qw), and landslides (unit 

Qls). Holocene alluvium is clearly related to the modern drainage, but in some drainages mapped Holocene alluvium (unit 

Qa) may include some older alluvium (unit Qoa). Holocene 

alluvium is most extensive along the Union River and probably 

overlies lake deposits of Lake Russell. Many of the wetland 

deposits are perched on till, indicating that the till has poor 

drainage. Other wetlands, such as those surrounded by recessional outwash sand and gravel southwest of Tahuya Lake, 

appear to be filled with kettles that developed in contact with 

ice. A large alluvial fan (unit Qf1) built into Wildcat Lake on 

the southwest is traversed by a small scarp above a younger fan 

(unit Qf2), perhaps representing a change in lake level. Human 

modification of the topography is mostly seen as artificial fill 

(unit af) at the Olympic View Sanitary Landfill, near Barney 

White Ranch, and in road fill over low-lying areas.

Structural History

Sheeted dikes in the Green and Gold Mountains massif 

hint at structural conditions during their emplacement. Clark 

(1989) found that most dikes had north-northeast strikes and 

considerable variation in dike orientations (fig. 3). Paleomagnetic data from the Coast Range basalt terrain on the Olympic 

Peninsula indicates little rotation of the terrain in this latitude 

since emplacement of the dikes (Beck and Engebretson, 1982). 

Thus, their orientation suggests east-southeast to west-northwest 

extension during their emplacement, but perhaps the scatter in 

dike orientations indicates emplacement during a transtensional 

strain regime where σ1 or σ2 rotated about a vertical axis. A 

north-northeast-trending magnetic high in the aeromagnetic 

data (Blakely and others, 1999) parallels the trend of the most 

common dike orientation, suggesting that the dikes may contribute significantly to the aeromagnetic signature.

The most significant fault in the quadrangle is the Seattle 

Fault, which extends along the south edge of the Seattle Basin 

from the east side of Lake Sammamish (east of Seattle) across 

Puget Sound to the Green and Gold Mountains area. On a 

regional scale, the sharpness of the gravity anomaly at the 

south side of the Seattle Basin, the presence of bedrock uplifts 

south of the Seattle Fault, such as Green and Gold Mountains, 

and the interpretation of seismic reflection and refraction data 

indicate that the Seattle Fault is a north-verging thrust (Johnson 

and others, 1994; Ten Brink and others, 2002). Johnson and 

others (1994) inferred that the Seattle Fault became active in 

late Eocene time. Ten Brink and others (2002) suggested that 

significant displacement on the Seattle Fault did not begin until 

Miocene time. An apatite fission-track date of 32±5 Ma from 

leucogabbro (Haeussler and others, 2000, also dated by U-Pb 

isotopes) is perhaps more consistent with initiation of movement on the Seattle Fault in early Oligocene time.

Prominent east-west valleys and offsets in quasi-ophiolitic 

layering led Clark (1989) to infer existence of the Tin Mine 

Lake Fault, which lies between the two lobes of Green Mountain, and the Gold Creek Fault, which lies between Green and 

Gold Mountains. Another roughly east-west-striking fault, 

which Haeussler and Clark (2000) refer to as the Holly Road 

Fault, is located along northwest Holly Road, just north of 

Green Mountain. The juxtaposition of submarine basaltic 

Equal Area

N = 100 C.I. = 2.0 sigma 

Figure 3. Kamb-contoured plot of poles to 

dikes of diabase and basalt. Black dots are poles 

to dikes. Data from Clark (1989).
7

sediments (unit Tcbs) along the road with leucogabbro (unit 

Teg) on the north side of Green Mountain at its lowest elevations supports the placement of this fault. Similar strikes of the 

Seattle Fault, the Tin Mine Lake Fault, the Gold Creek Fault, 

the fault near the Union River Reservoir, and the Holly Road 

Fault suggest that these faults are related. Because the Seattle 

Fault is contractional, Clark (1989) inferred that the other eastwest faults probably also are reverse faults. He inferred that the 

three northern faults are south dipping and that the Gold Creek 

Fault and fault near the Union River Reservoir are north dipping, but, with the exception of the Seattle Fault, the dip angles 

of all these faults are unconstrained.

Clark (1989) mapped three additional faults with northeast 

or north-northeast strikes. The Green Mountain Fault is a leftlateral oblique fault that bisects Green Mountain. Clark (1989) 

observed left-lateral slickensides on fault surfaces in outcrop. 

Offset of the quasi-ophiolitic layering indicates a northwestside-down sense of dip-slip motion on the fault. On slickensided 

surfaces, the dip-slip slickensides are the youngest. A fault 

along Lost Creek, southeast of Green Mountain, has a strike 

and sense of separation similar to the Green Mountain Fault 

and is principally indicated by a geomorphic lineament and 

offset in the quasi-ophiolitic layering. A fault along the Union 

River, located north of the Union River Reservoir, follows a 

north-northeast-trending topographic lineament. West-side-up 

movement along this fault is indicated by offset of the quasiophiolitic layering.

Haeussler and Clark (2000) were uncertain how these 

northeast-striking faults relate to the east-west-striking faults. 

Clark (1989) concluded that the northeast-striking faults formed 

in the late stages of the same extensional event that produced 

the mafic dikes, on the basis of his inference that the dip-slip 

motion was normal and of the fault orientation. If these faults 

were normal, then the extension direction of the most common 

dike orientation is similar to the extension direction inferred by 

the faults. If the northeast-striking faults were related to dike 

intrusion, Heussler and Clark (2000) suggested that there should 

be faults that cut the lower, but not the entire, quasi-ophiolitic 

layering. Because they did not find such faults, they suggested 

that the northeast-striking faults could be related to contraction 

and (or) oblique motion on the Seattle Fault and related faults.

The overall structural pattern suggests north-south shortening after Crescent Formation time, a conclusion consistent with 

underthrusting of the Crescent Formation beneath Vancouver 

Island and with continued northward migration of the Coast 

Range in response to oblique subduction (Clowes and others, 

1987; Wells and others, 1998).

Above, we discussed the evidence for folding of recessional outwash terraces (terrace Qvrt7) in the Tahuya River and 

Big Beef Creek valleys. This folding is younger than the ~16 

ka age of the terraces. Projection of alluvial-plane elevations 

onto a north-south cross section and correction for 0.1 percent 

up-to-the north tilting by postglacial isostatic rebound (Thorson, 1989) closely defines a smooth fold with a 23-m-elevation 

difference between the low at Lake William Symington and 

the high at the Big Beef Creek-Tahuya River divide about 3 

mi (5 km) to the southwest (fig. 2). Inclusion of the (unknown) 

paleogradient of the outwash stream increases the elevation 

difference.

We infer that this young fold is growing above the buried 

Seattle Fault (Haugerud and Tabor, 2008). The ~10-km width 

of the anticline is similar to the extent of uplift during the A.D. 

~900 Seattle Fault earthquake farther east (ten Brink and others, 

2006). The analysis of ten Brink and others (2006) suggests 

~15 m of shortening during the A.D. 900 event that developed 

structural relief of ~9 m; scaling to the observed ≥23 m of relief 

observed in the Wildcat Lake quadrangle suggests ≥38 m of 

shortening in the last 16 ka, or ≥2 mm/yr. Booth and others 

(2004) estimated 0.5 mm/yr shortening on the Seattle Fault over 

the last several hundred thousand years.

DESCRIPTION OF MAP UNITS

UNCONSOLIDATED DEPOSITS

POSTGLACIAL DEPOSITS

af Artificial fill (Holocene)—Gravel, sand, soil, and broken rock. Includes concrete in dam at 

northeast end of Lake William Symington, fill along railroad near Twin Lakes and Leisureland Airpark, sanitary landfill near Barney White Ranch, and modified recessional outwash 

gravels and lake deposits

Qba Alluvium (Holocene)—Moderately sorted deposits of cobble gravel, pebbly sand, and floodplain 

sandy silt mostly along Stavis Creek, Big Beef Creek, and the Union River

Qls Landslide deposits (Holocene)—Diamicton of angular clasts of bedrock and surficial deposits derived from upslope commonly includes trees. Includes areas of irregular, hummocky 

topography. Poorly consolidated. Interpreted from the DEM

Qf Alluvial fan deposits (Holocene and Pleistocene)—Boulders, cobbles, and soft sand deposited 

in lobate form, where streams emerge from confining valleys and reduced gradients cause 

sediment loads to be deposited. Interpreted from the DEM. Locally divided by age
8

Qfy Younger alluvial fan (Holocene)

Qfo Older alluvial fan (Holocene and Pleistocene)

Qoa Older alluvium (Holocene and Pleistocene)—Moderately sorted deposits of cobble gravel, 

pebbly sand, and floodplain sandy silt. Located in several major drainages such as Union 

River and Stavis and Big Beaver Creeks. Divided from youngest to oldest

Qoa6 Older alluvium, unit 6

Qoa5 Older alluvium, unit 5

Qoa4 Older alluvium, unit 4

Qoa3 Older alluvium, unit 3

Qoa2 Older alluvium, unit 2

Qoa1 Older alluvium, unit 1

Qw Wetland deposits (Holocene and late Pleistocene)—Peat deposits with some intermixed sand, 

silt, and clay. Unit commonly occupies shallow depressions in till (unit Qvt) or low-lying 

areas of outwash (units Qvr, Qva)

GLACIAL AND INTERGLACIAL DEPOSITS

Deposits of Vashon stade of Fraser Glaciation of Armstrong and others (1965) (late Pleistocene)

Proglacial lake deposits

Qvrl Recessional lacustrine deposits

Qvlf Recessional sublacustrine alluvial fan deposits

Qvls Recessional sublacustrine landslide deposits

Qvro Recessional outwash deposits—Stratified and unconsolidated buff-colored sand and gravel 

deposits graded mostly to Lake Russell or, rarely, Lake Bretz. These deposits mostly form 

terraces mapped from youngest to oldest

Chico Creek outwash deposits—Two terraces graded to Lake Russell via Chico Creek

Qvrc2 Chico outwash, unit 2

Qvrc1 Chico outwash, unit 1

Big Beef Creek outwash deposits—Three terraces in a tributary to Big Beef Creek graded 

to Lake Bretz or Lake Russel via Big Beef Creek

Qvrb3 Big Beef outwash, unit 3

Qvrb2 Big Beef outwash, unit 2

Qvrb1 Big Beef outwash, unit 1

Outwash deposits south of Wildcat Creek—Three high terraces, which may have formed 

subglacially, graded to Lake Russell via Lost Creek

Qvr3 Outwash, unit 3

Qvr2 Outwash, unit 2

Qvr1 Outwash, unit 1

Tahuya River outwash deposits—In lower terraces in upper Big Beef Creek and Tahuya 

River, graded to Lake Russell via the Tahuya River

Qvrt7 Tahuya outwash, unit 7

Qvrt6 Tahuya outwash, unit 6

Qvrt5 Tahuya outwash, unit 5

Union Creek area outwash deposits—Graded to Lake Russell in Union Creek area, including a delta near Franklin Falls built into the lake

Qvru2 Union Creek outwash, unit 2

Qvru1 Union Creek outwash, unit 1

Big Beef-Tahuya-Mission outwash deposits—In higher terraces above upper Big Beef 

Creek, Tahuya River, and Mission Creek, graded to Lake Russell via south-draining creeks 

and rivers

Qvrt4 Tahuya outwash, unit 4

Qvrt3 Tahuya outwash, unit 3

Qvrt2 Tahuya outwash, unit 2

Qvrt1 Tahuya outwash, unit 1

Lower Tahuya River outwash deposits—Near west and southwest edge of quadrangle, 

graded to Lake Russell via lower Tahuya River

Qvrs3 Southwest outwash, unit 3

Qvrs2 Southwest outwash, unit 2
9

Qvrs1 Southwest outwash, unit 1

Qvrw2 West outwash, unit 2

Qvrw1 West outwash, unit 1

Qvri Ice-contact deposits—Stratified and unconsolidated buff-colored sand and gravel deposits with 

pitted outwash topography in southeastern part of map area. Sediments locally show deformation as a result of sag, slump, or collapse

Qvt Till—Compact light- to dark-gray, nonstratified diamict containing subangular to well-rounded 

clasts, glacially transported and deposited. Abundant granitic clasts were derived from 

Canada. Commonly overlies advance outwash deposits (unit Qva) and bedrock on Green 

and Gold Mountains. Forms undulating surface, with sediment less than 10 ft (3 m) to about 

65 ft (20 m) thick (Deeter, 1978)

Qva Advance outwash deposits—Stratified to nonstratified gravel deposits. Locally consolidated and 

hard. Upper meter may be weathered buff to brown. Clasts are usually moderately to well 

rounded and <16 inches (<40 cm) across. Some deposits are diamicts that were deposited as 

debris flows issuing from front of advancing ice sheet. Debris-flow deposits in this unit are 

differentiated from till by (1) lack of clasts >16 in (>40 cm), (2) large cobbles commonly 

touching rather than matrix supported, (3) high proportion (roughly 40% or more) of large 

clasts, and (4) less compaction than till. As mapped, includes pre-Vashon-age deposits in 

Stavis Creek and probably in Big Beef Creek

Qpvu Pre-Vashon-age deposits (Pleistocene)—Glacial and interglacial sediments inferred to underlie 

oldest Vashon-age deposits. Shown on cross section only

BEDROCK

STRATIFIED ROCKS

Tb Blakeley Formation (upper Eocene and Oligocene)—Appears only in cross section, where it is 

inferred north of the Seattle Fault

Tcfv Felsic volcanic(?) rock (middle Eocene)—Fine-grained, pinkish-orange- to brown-weathering 

amygdaloidal quartz latite. Forms tabular bodies that could be either conformable interbeds 

or younger sills in submarine basalt. Probable high-level or extrusive equivalent of felsic 

intrusive rock, unit Tefv. Intergranular porphyritic or intergranular glomeroporphyritic; 

alteration minerals form about 50% of rock

Crescent Formation (middle Eocene)

Tcb Massive basaltic lava flows—Lavas contain pyroxene phenocrysts and calcite- or zeolitefilled amygdules. Texture in thin section is intergranular, with rock consisting of 45% 

labradoritic plagioclase, 35% augitic clinopyroxene, 15% opaques, and minor olivine and 

orthopyroxene. Individual flows are typically 10 m thick. Inferred to be subaerial because 

of a lack of interbedded sedimentary rocks. Exposed thickness is at least 590 ft (180 m) but 

may be more than 0.6 mi (1 km) (Clark, 1989)

Tcbs Submarine basalt and related volcaniclastic rocks—Dominantly greenish weathering 

submarine basalt flows interbedded with tuffs, tuff breccias, basaltic breccias, graded lithic 

and tuffaceous sandstones, basaltic siltstones, and conglomerates. No pillows recognized; 

vesicles are generally filled with calcite. In thin section, plagioclase typically composes 

about 50% of the rock, clinopyroxene 35%, and opaques about 10%. Sedimentary interbeds 

usually <1 m thick and as much as 10 m thick. These volcaniclastic rocks include altered 

lithic tuffs, volcanic breccias, aquagene crystal-lithic tuffs, graded basaltic sandstones and 

siltstones, and welded tuffs. Approximately 590 ft (180 m) thick. Intruded by dikes of basalt 

and diabase of unit Ted

INTRUSIVE ROCKS

Tad Porphyritic and aphanitic dacite dikes (Eocene)—Medium to light grey. Dikes cut all other 

bedrock units. In thin section, consists of about 50% plagioclase, 5–20% quartz, 10–15% 

amphibole, and about 15% other mafic minerals. Textures are, in decreasing abundance, 

pilotaxitic porphyritic, glomeroporphyritic with a felty groundmass, and hyalopilitic. Individual dikes shown on cross section only

Tefv Felsic intrusive rocks (Eocene?)—Quartz monzonite, quartz diorite, tonalite. Texture in thin section is intergranular granophyric. Intrudes basalts that appear to cut leucogabbro of unit Teg
10

References Cited

Armstrong, J.E., Crandell, D.R., Easterbrook, D.J., and Noble, 

J.B., 1965, Late Pleistocene stratigraphy and chronology in 

southwestern British Columbia and northwestern Washington: Geological Society of America Bulletin, v. 76, p. 

321–330.

Arnold, Ralph, 1906, Geological reconnaissance of the coast of 

the Olympic Peninsula, Washington: Geological Society of 

America Bulletin, p. 451–468.

Atwater, B.F., and Moore, A.L., 1992, A tsunami about 1,000 

years ago in Puget Sound, Washington: Science, v. 258, p. 

1614–1617.

Babcock, R.S., Burmester, R.F., Engebretson, D.C., Warnock, 

A., and Clark, K.P., 1992, A rifted margin origin for the 

Crescent basalts and related rocks in the northern Coast 

Range volcanic province, Washington and British Columbia: Journal of Geophysical Research, v. 97, p. 6799–6821.

Beck, M.E., and Engebretson, D.C., 1982, Paleomagnetism 

of small basalt exposures in the west Puget Sound area, 

Washington, and speculation on the accretionary origin of 

the Olympic Moutains: Journal of Geophysical Research, 

v. 87, no. B5, p. 3755–3760.

Blakely, R.J., Wells, R.E., and Weaver, C.S., 1999, Puget Sound 

aeromagnetic maps and data: U.S. Geological Survey 

Open-File Report 99–514 (http://geopubs.wr.usgs.gov/

open-file/of99-514).

Blakely, R.J., Wells, R.E., Weaver, C.S., and Johnson, S.Y., 

2002, Location, structure, and seismicity of the Seattle 

fault zone, Washington—Evidence from aeromagnetic 

anomalies, geologic mapping, and seismic reflection data: 

Geological Society of America Bulletin, v. 114, no. 2, 

169–177.

Booth, D.B., 1987, Timing and processes of deglaciation along 

the southern margin of the Cordilleran ice sheet, in Ruddiman, W.F., and Wright, H.E., Jr., eds., North America 

and adjacent oceans during the last deglaciation: Boulder, 

Colo., Geological Society of America, The geology of 

North America, v. K–3, p. 71–90.

Booth, D.B., and Hallet, B., 1993, Channel networks carved by 

subglacial water—Observations and reconstruction in the 

eastern Puget Lowland of Washington: Geological Society 

of America Bulletin, v. 105, p. 671–683.

Booth, D.B., Troost, K.G., and Hagstrum, J.T., 2004, Deformation of Quaternary strata and its relationship to crustal 

folds and faults, south-central Puget Lowland, Washington 

State: Geology, v. 32, no. 6, p. 505–508.

Brandon, M.T., Roden-Tice, M.K., Garver, J.I., 1998, Late 

Ted Sheeted dikes of basalt and diabase (Eocene)—Sheeted dikes are dark greyish black on fresh 

surfaces and weather bluish to greenish grey. Dikes are a few inches to 30 ft (10 m) thick 

but are most commonly about 3 ft (1 m) thick. Dike margins are chilled on either one or 

both sides. Textures range from very fine grained to diabasic and microgabbroic. Augite is 

dominant pyroxene in thin section. Dikes are amygdaloidal where they intrude the overlying 

submarine basalts and sediments. Zone consisting entirely of dikes is about 500 ft (150 m) 

thick. Individual dikes shown diagramatically on cross section only

Tegd Leucogabbro and pegmatite intruded by dikes of basalt and diabase (Eocene)—Leucogabbro 

and pegmatite, described in unit Teg, either fine or coarse grained, occur as screens between 

dikes of basalt and diabase. Dikes, of unit Ted, are as much as 30 ft (10 m) thick but are 

commonly about 3 ft (1 m) thick. Medium grey on fresh surfaces; weathers light gray to 

orange gray

Teg Leucogabbro and pegmatite (Eocene)—Massive leucogabbro, either fine or coarse grained. 

Medium grey on fresh surfaces; weathers light gray to orange gray. Texture in thin section 

is intergranular and glomeroporphyritic with phenocrysts of plagioclase and less commonly 

augitic pyroxene. Plagioclase ranges in composition from labradorite to bytownite. Overall 

rock composition is approximately 45% plagioclase, 40% clinopyroxene, as much as 5% 

brown hornblende, and 5% opaques. The brown hornblende is interstitial to other mineral phases. “Pegmatoid” denotes very coarse grained intrusive rocks associated with the 

leucogabbro. End members of the pegmatoid rocks are gabbroic and granophyric. Gabbroic 

pegmatoid rock has intergranular texture with ophitic to subophitic plagioclase grains to 1.5 

in (3–4 cm) across. Rock composition is approximately 45% plagioclase, 40% clinopyroxene, and 5–10% magnetite. Granophyric pegmatoid rock is intergranular granophyric with 

grains to several centimeters across and an overall composition of 40% oligoclase, 10–20% 

pyroxene, 25% quartz, 10% micrographic regions, as much as 10% magnetite, and minor 

epidote and microcline

Teum	 Ultramafic rocks (Eocene)—Utramafic rocks beneath Green and Gold Mountains inferred from 

modeling aeromagnetic and gravity data. Rocks must be dense and magnetic. Shown only on 

cross section
11

Cenozoic exhumation of the Cascadia accretionary wedge 

in the Olympic Mountains, northwest Washington State: 

Geological Society of America Bulletin, v. 110, p. 985–

1009.

Brandon, M.T., and Vance, J.A., 1992, Tectonic evolution of 

the Cenozoic Olympic Subduction Complex, Washington 

State, as deduced from fission track ages for detrital zircons: American Journal of Science, v. 292, p. 565–636.

Bretz, J. Harlen., 1913, Glaciation of the Puget Sound region: 

Washington Geological Survey (State of Washington), Bulletin no. 8, 244 p.

Bucknam, R.C., Hemphill-Haley, Eileen, and Leopold, E.B., 

1992, Abrupt uplift within the past 1700 years at southern 

Puget Sound, Washington: Science, v. 258, p. 1611–1614.

Clark, K.P., 1989, The stratigraphy and geochemistry of the 

Crescent Formation basalts and the bedrock geology of 

associated igneous rocks near Bremerton, Washington: 

Bellingham, Western Washington University, unpublished 

M.S. thesis, 171 p.

Clowes, R.M., Brandon, M.T., Green, A.G., Yorath, C.J., 

Sutherland Brown, A., Kanasewich, E.R., and Spencer, C., 

1987, LITHOPROBE, southern Vancouver Island—Cenozoic subduction complex imaged by deep seismic reflections: Canadian Journal of Earth Sciences, v. 24, p. 31–51.

Deeter, J.D., 1978, Quaternary geology and stratigraphy of 

Kitsap County: Bellingham, Western Washington University, M.S. thesis, 175 p. 

Dragovich, J.D, Logan, R.L., Schasse, H.W., Walsch, T.J., Lingley, W.S., Jr., Norman, D.K., Gerstel, W.J., Lapen, T.J., 

Schuster, J.E., and Meyers, K.D., 2002, Geologic Map of 

Washington—Northwest Quadrant: Washington Division 

of Geology and Earth Resources Geologic Map GM–50.

Duncan, R.A., 1982, A captured island chain in the Coast 

Range of Oregon and Washington: Journal of Geophysical 

Research, v. 87, p. 10,827–10,837.

Esser, R.P., 2003, 40Ar/39Ar Geochronology Results from two 

(Adakite) dikes from the Bremerton area of Washington: 

New Mexico Geochronology Research Laboratory Internal 

Report prepared for Dr. Jeff Tepper, Number NMGRLIR-313, 7 p. 

Garling, M.E., Molenaar, Dee, Bailey, E.G., VanDenburgh, A.S., 

Fiedler, G.H., 1965, Water resources and geology of the 

Kitsap Peninsula and certain adjacent islands: Washington 

Department of Water Resources, Water Supply Bulletin, p. 

309.

Geomatrix Consultants, 1997, Conceptual hydrogeologic model 

report, Olympic View sanitary landfill: USA Waste Services, Inc., Kitsap County, Washington, Project No. 3946.

Gradstein, F.M., Ogg, J.G., and Smith, A.G., eds., 2004, A geologic time scale, 2004: Cambridge University Press, 585 p.

Haeussler, P.J., and Clark, K.P., 2000, Geologic Map of the 

Wildcat Lake 7.5′ quadrangle, Kitsap and Mason Counties, 

Washington: U.S. Geological Survey Open File Report 

00-356, v. 1.0, scale 1:24,000.

Haeussler, P.J., Wells, R.E., Blakely, R.J., Murphy, John, and 

Wooden, Joe, 2000, Constraints on structure and timing 

of movement of the Seattle fault from structural geology, 

geophysics, and geochronology of the Green Mountain and 

Gold Mountain igneous complex, Washington: Geological Society of America Abstracts with Programs, v. 32, p. 

A–16.

Haugerud, R.A., 2009, Preliminary geomorphic map of the 

Kitsap Peninsula, Washington: U.S. Geological Survey, 

Open-File Report 2009–1033, 2 sheets, scale 1:36,000 

(http://pubs.usgs.gov/of/2009/1033/).

Haugerud, R.A., Harding, D.J., Johnson, S.Y., Harless, J.L., 

Weaver, C.S., and B.L. Sherrod, 2003, High-resolution 

lidar topography of the Puget Lowland, Washington—A 

bonanza for earth science: GSA Today, v. 13, no. 6, p. 

4–10.

Haugerud, R.A., and Tabor, R.W., 2008, Geomorphic evidence 

for multiple large post-glacial earthquakes on the Western 

Seattle Fault: American Geophysical Union, Fall Meeting 

2008, abstract #T23E-05.

Jacoby, G.C., Williams, P.L., and Buckley, B.M., 1992, Tree 

ring correlation between prehistoric landslides and abrupt 

tectonic events in Seattle, Washington: Science, v. 258, p. 

1621–1623.

Johnson, S.Y., Potter, C.J., and Armentrout, J.M., 1994, Origin 

and evolution of the Seattle fault and Seattle basin, Washington: Geology, v. 22, p. 71–74.

Karlin, R.E., and Abella, S.E.B., 1992, Paleoearthquakes in 

the Puget Sound region recorded in sediments from Lake 

Washington, U.S.A.: Science, v. 258, p. 1617–1620.

Porter, S.C., and Swanson, T.W., 1998, Radiocarbon age constraints on rate of advance and retreat of the Puget Lobe of 

the Cordilleran ice sheet during the last glaciation: Quaternary Research, v. 50, p. 205–213.

Pratt, T.L., Johnson, S.Y., Potter, C.J., Stephenson, W.J., Finn, 

C.A., 1997, Seismic reflection images beneath Puget 

Sound, western Washington State—the Puget Lowland 

thrust sheet hypothesis: Journal of Geophysical Research, 

v. 102, no. B12, p. 27,469–27,489.

Prothero, D.R., 2001, Magnetic stratigraphy of the middle 

Eocene Point of Rocks Sandstone (Ulatisian and type 

Narizian stages), western San Joaquin Basin, California, 

in Prothero, D.R., ed., Magnetic stratigraphy of the Pacific 

Coast Cenozoic: Society of Economic Paleontologists and 

Mineralogists, Pacific Section, v. 91, p. 65–74. 

Reeve, William, 1979, Bedrock geology of the Blue Hills, 

Kitsap County, Washington: Golden, Colorado School of 

Mines, M.S. thesis, 58 p.

Sceva, J.E., 1957, Geology and groundwater resources of Kitsap 

County, Washington: U.S. Geological Survey Water Supply 

Paper 1413, 178 p. 

Schuster, R.L., Logan, R.L., Pringle, P.T., 1992, Prehistoric rock 

avalanches in the Olympic Mountains, Washington: Science, v. 258, p. 1620–1621.

Snavely, P.D., Jr., MacLeod, N.S., and Wagner, H.C., 1968, 

Tholeiitic and alkalic basalts of the Eocene Siletz River 

Volcanics, Oregon Coast Range: American Journal of Science, v. 266, p. 454–481.

Spencer, P.K., 1984, Lower Tertiary biostratigraphy and paleoecology of the Quilcene-Discovery Bay area, northeast 

Olympic Peninsula, Washington: Seattle, University of 

Washington, Ph.D. dissertation, 173 p.
12

Tabor, R.W., and Cady, W.M., 1978a, Geologic map of the 

Olympic Peninsula, Washington: U.S. Geological Survey 

Miscellaneous Investigations Map I–994, scale 1:125,000, 

2 sheets.

Tabor, R.W., and Cady, W.M., 1978b, The structure of the 

Olympic Mountains, Washington—Analysis of a subduction zone: U.S. Geological Survey Professional Paper 

1033, 38 p.

Tabor, R.W., Haeussler, P.J., Haugerud, R.A., and Wells, R.E., 

2011, lidar-revised geologic map of the Uncas 7.5′ quadrangle, Clallam and Jefferson Counties, Washington: U.S. 

Geological Survey Scientific Investigations Map 3160, 2 

sheets, scale 1:24,000, pamphlet, 9 p., and GIS data.

ten Brink, U.S., Molzer, P.C., Fisher, M.A., Blakely, R.J., 

Bucknam, R.C., Parsons, T., Crosson, R.S., and Creager, 

K.S., 2002, Subsurface geometry and evolution of the 

Seattle fault zone and the Seattle basin, Washington: Bulletin of the Seismological Society of America, v. 92, p. 

1737–1753. 

ten Brink, U.S., Song, J., and Bucknam, R.C., 2006, Rupture 

models for the A.D. 900–930 Seattle fault earthquake from 

uplifted shorelines: Geology, v. 34, p. 585–588.

Tepper, J.H., Clark, K.P., Asmerom, Y., and McIntosh, W., 2004, 

Eocene adakites in the Cascadia Forearc—Implications for 

the position of the Kula-Farallon Ridge: Geological Society of America Abstract #72271, Rocky Mountain (56th 

Annual) and Cordilleran (100th Annual) Joint Meeting 

(May 3–5, 2004).

Thorson, R.M., 1979, Isostatic effects of the last glaciation in 

the Puget Lowland: Seattle, University of Washington, 

Ph.D. dissertation, 154 p. 

Thorson, R.M., 1980, Ice-sheet glaciation of the Puget Lowland, 

Washington, during the Vashon Stade (late Pleistocene): 

Quaternary Research, v. 13, p. 303–321.

Thorson, R.M., 1989, Glacio-isostatic response of the Puget 

Sound area, Washington: Geological Society of America 

Bulletin, v. 101, p. 1163–1174.

Waitt, R.B., Jr., and Thorson, R.M., 1983, The Cordilleran ice 

sheet in Washington, Idaho, and Montana, in Porter, S.C., 

and Wright, H.E., Jr., eds., Late-Quaternary environments 

of the United States: University of Minnesota Press, v. 1, 

p. 53–70.

Weaver, C.E., 1937, Tertiary stratigraphy of western Washington and northwestern Oregon: University of Washington 

Publication in Geology, v. 4, 266 p.

Wells, R.E., Engebretson, D.C., Snavely, P.D., Jr., and Coe, 

R.S., 1984, Cenozoic plate motions and the volcanotectonic evolution of western Oregon and Washington: 

Tectonics, v. 3, p. 275–294.

Wells, R.E., Weaver, C.S., and Blakely, R.J., 1998, Fore-arc 

migration in Cascadia and its neotectonic significance: 

Geology, v. 26, p. 759–762.

Willis, B., 1898, Drift phenomena of the Puget Sound: Geological Society of America Bulletin, v. 9, p. 111–162. 

Willis, B., and Smith, G.O., 1899, Description of the Tacoma 

quadrangle, Washington: U.S. Geological Survey, Geological Atlas Folio, scale 1:125,000. 

Yount, J.C., and Gower, H.D., 1991, Bedrock geologic map of 

the Seattle 30′ by 60′ quadrangle, Washington: U.S. Geological Survey Open-File Report 91–147, scale 1:100,000.

Yount, J.C., Minard, J.P., and Dembroff, G.R., 1993, Geologic 

map of surficial deposits in the Seattle 30′ by 60′ quadrangle, Washington: U.S. Geological Survey Open-File Report 

93–233, scale 1:100,000.