Lidar–Revised Geologic Map of the Olalla 7.5' Quadrangle, 

King, Kitsap, and Pierce Counties, Washington

Pamphlet to accompany

Scientific Investigations Map 3277

2013

U.S. Department of the Interior 

U.S. Geological Survey
ii

Contents

Contents...........................................................................................................................................................................................ii

Introduction to Revised Version of the Map .....................................................................................................................................1

Geologic Issues............................................................................................................................................................................1

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

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

Introduction ..................................................................................................................................................................................2

Previous Mapping ........................................................................................................................................................................2

Acknowledgments ........................................................................................................................................................................2

Stratigraphic Framework ..............................................................................................................................................................2

Deposits Predating the Vashon Stade of the Fraser Glaciation of Armstrong and Others (1965)............................................3

Deposits Of The Vashon Stade Of The Fraser Glaciation Of Armstrong And Other (1965).....................................................4

Structure .......................................................................................................................................................................................8

Description Of Map Units .................................................................................................................................................................8

Nonglacial Deposits .....................................................................................................................................................................8

Younger Glacial Deposits.............................................................................................................................................................9

Older Glacial And Nonglacial Deposits ......................................................................................................................................11

References.....................................................................................................................................................................................12
1

Lidar-Revised Geologic Map of the Olalla 7.5' Quadrangle, 

King, Kitsap, and Pierce Counties, Washington

By Rowland W. Tabor, Ralph A. Haugerud, Derek B. Booth, and Kathy Goetz Troost 

Introduction to Revised Version of the Map

Our map is an interpretation of a 6-ft resolution lidar-derived digital elevation model combined 

with the geology depicted on the "Geologic map of the Olalla 7.5' quadrangle, King, Kitsap, and Pierce 

Counties, Washington," by Booth and Troost (2005), which was described, interpreted, and located on 

the 1953 1:24,000-scale topographic map of the Olalla 7.5-minute quadrangle. The original topographic 

base map, derived from 1951 aerial photographs, has 20-ft contours, nominal horizontal resolution of 

circa 40 ft (12 m), and nominal mean vertical accuracy of circa 13 ft (4 m). Similar to many geologic 

maps, much of the Booth and Troost (2005) geology—especially the distribution of surficial deposits—

was interpreted from landforms portrayed on the topographic map, supplemented by field exposures 

where available. In 2001, the Puget Sound Lidar Consortium (see http://pugetsoundlidar.org/) obtained a 

lidar-derived digital elevation model (DEM) for Kitsap Peninsula and Vancouver Island. For a brief 

description of lidar (LIght Detection And Ranging) and this data acquisition program, see Haugerud and 

others (2003). This new DEM has a horizontal resolution of 6 ft (2 m) and mean vertical accuracy circa 

1 ft (0.3 m). The greater resolution and accuracy of the lidar DEM facilitated a much-improved 

interpretation of many aspects of the surficial geology, especially the distribution and relative age of 

landforms and the materials inferred to comprise them.

Geologic Issues

We have done no additional field work to make this map. Most of the text in the Description of 

Map Units and elsewhere is quoted directly from Booth and Troost (2005). We modified table 1 slightly 

and moved sample and structural data points to fit the lidar topography and maintain identification 

within the original units. The reader may also refer to Booth and Troost (2005) for useful bluff sketches 

of the west coast of Vashon Island and the east coast of the Kitsap Peninsula that display stratigraphic 

relations between various Pleistocene-age deposits—illustrations that we have not reproduced here. 

Base Map Issues

The positions of geographic features on the old contour base of the Olalla quadrangle, compared 

to the same features on the DEM, are displaced by as much as 1,000 ft (300 m). Many contacts are 

shown as approximately located, especially those copied directly from Booth and Troost (2005). 

There is no digital depiction of stream locations that adequately matches the lidar DEM. We 

have therefore newly digitized the location of streams, rivers, and water boundaries on the DEM. We 

selected rivers and streams to digitize based on drainage shown on the published Olalla 1:24,000-scale 

topographic map. Most of the roads displayed on the map were added from digital coverages available 

from Kitsap County (http://www.kitsapgov.com/gis/metadata/). South of Kitsap County we digitized 
2

additional roads from the DEM. We referred mostly to 1:100,000-scale road depictions and Google 

Earth to select roads that are shown on this map. 

Geologic Summary

Introduction

The Olalla 7.5' quadrangle, which lies almost in the center of the Puget Lowland, displays the 

broad range of geologic environments typical of the region. The upland plain is fluted by the passage of 

the great continental ice sheet that last covered the area about 17,000 (14,000 radiocarbon) years ago

(Porter and Swanson, 1998). The plain is cut by channel deposits, both late glacial and postglacial in 

age, and it is cleaved even more deeply by one of the major arms of Puget Sound, Colvos Passage, 

which here separates the west coast of Vashon Island from the Kitsap Peninsula. 

Beneath the deposits of the last ice sheet is a complex sequence of older Quaternary-age 

sediments that extends about 400 m below the modern ground surface (Jones, 1996). These older 

sediments are best exposed along the shorelines and beach cliffs of Puget Sound, where wave action and 

landslides maintain relatively fresh exposures. The older sediments typically are compact, having been 

loaded by ice during one or more episodes of glaciation subsequent to their deposition. Locally these 

sediments are also cemented by iron and manganese oxides and hydroxides, a consequence of many tens 

or hundreds of thousands of years of weathering and groundwater movement. 

Previous Mapping

On Vashon Island, Booth and Troost (2005) used preexisting map data of Booth (1991). 

Previously published geologic maps by Sceva (1957), Garling and others (1965), and Deeter (1979) 

included much or all of the quadrangle at smaller scales; although not used by Booth and Troost (2005) 

or on this map, their data represent significant contributions for their time and have been valuable 

resources for establishing the general geologic context. 

Along with much of the geology modified from Booth and Troost (2005), many geologic 

contacts within Kitsap County on this revised map have been adapted from Haugerud (2009). 

Acknowledgments 

We thank Trevor Contreas and Kevin Schmidt for extremely helpful reviews. The map is much 

improved due to their efforts. 

Stratigraphic Framework

Multiple invasions of glacial ice into the Puget Lowland have left a discontinuous record of 

Pleistocene glacial and nonglacial periods. Originating in the mountains of British Columbia, the ice was 

part of the Cordilleran ice sheet of northwestern North America. During each successive glaciation, ice 

advanced into the lowland as a broad tongue, first called the Puget lobe by Bretz (1913). Willis (1898) 

first presented evidence for multiple glaciations in the Puget Lowland. 

Past mapping in the Olalla quadrangle reflected many of the uncertainties that have accompanied 

regional efforts to identify and to correlate the various glacial and nonglacial deposits. Garling and 

others (1965) correlated the older glacial deposits exposed along the shores of Puget Sound with the 

Salmon Springs Drift (Crandell and others, 1958), and Deeter (1979) called these same deposits 

"Possession" by virtue of stratigraphic position and presumed correlation with the Possession Drift of 

Easterbrook and others (1967); none of these early workers, however, could support their correlation

with isotopic age determinations. Also problematic for making stratigraphic assignments are the fine-
3

grained lacustrine sediments that both overlie and underlie these older glacial deposits. Early mappers 

named them the Kitsap Formation, and subsequent mappers have used this name as well; however, 

Deeter (1979) correctly noted that the deposits assigned to the Kitsap Formation span multiple 

depositional periods that likely are separated by multiple glacial intervals. Indeed, the term as used does 

not refer unequivocally to strictly glacial or strictly nonglacial deposits. Because of these imprecisions, 

we do not use the name in the current mapping, even though both the original type locality (Sceva, 

1957) and its proposed redefinition (Garling and others, 1965) are located in the quadrangle, on the west 

side of Colvos Passage near the south map boundary. 

Deposits Predating the Vashon Stade of the Fraser Glaciation of Armstrong and Others (1965)

The oldest exposed sediment (unit Qrgf) in the quadrangle is reversely magnetized and, so, is 

probably more than 774,000 years old. Hagstrum and others (2002; Table 1) report reversed 

paleomagnetic measurements of lacustrine silt and clay at three localities on the north Kitsap Peninsula 

coastline: near the mouth of Fragaria Creek (sample T8200), south of View Park (sample T9058), and 

just north of Wilson Creek (sample T8197). At Sandford Point on Vashon Island (unit Qpof; sample 

T1321) and to the north, near Lisabuela (unit Qpo; sample T7280), texturally similar sediments have 

transitional polarities (Hagstrum and others, 2002; Table 1), suggesting a more precise 774-ka age. 

Where paleomagnetic determinations are mostly absent, deposits older than the Fraser glaciation 

of Armstrong and others (1965) (hereafter referred to as Fraser glaciation) are locally subdivided on the 

map (units Qpf and Qpo) by their inferred depositional environment. Where organic material or 

volcanic sediment is abundant, Booth and Troost (2005) inferred a likely nonglacial origin (units Qpfn

and Qpon). Deposits inferred to be of glacial origin (Mullineaux and others, 1965) display a suite of 

sand and (or) gravel lithologies indicative of southward transport from the North Cascades or British 

Columbia (presumably by a continental ice sheet) or sedimentary features characteristic of glacial or 

proglacial environments, and they are included in units Qpog and coarse, fine, and till sub-units (units

Qpogc, Qpogf, and Qpogt); note that all pre-Fraser glacial periods also precede the Olympia nonglacial 

interval. Booth and Troost (2005) did not assign stratigraphic names to these pre-Fraser glaciation-age 

deposits, however, because absolute age control was and still is very sparse. Normal-polarity sediments 

at scattered localities (samples T7001, T7004, T7007, T7010, T7277, and T8203) indicate that these 

mapped deposits are younger than 774 ka (Hagstrum and others, 2002; Table 1). 

In the eastern part of the quadrangle, Booth and Troost (2005) recognized two, and possibly 

three, separate pre-Fraser glaciation-age tills. The two younger tills overlie normally magnetized

sediment and so are younger than 774,000 years old; the age of the oldest pre-Fraser glaciation-age till is 

indeterminant. To the west, exposures are poorer, and Booth and Troost (2005) identified only one preFraser glaciation-age till. Diamictons of presumed glacial origin whose deposition predates the Fraser 

glaciation are shown as discrete units (Qpogt); layers or lenses within more generalized units are shown 

as a red line on the map. The absence of mapped diamictons elsewhere on the quadrangle reflects not 

only the likely discontinuity of these deposits but also the typically poor exposures across the map area, 

even under relatively favorable conditions of steep topography and sparse vegetation. 

The Olympia nonglacial interval of Armstrong and others (1965) (hereafter referred to as 

Olympia nonglacial interval) immediately preceded the most recent ice-sheet advance into the Puget 

Lowland (Mullineaux and others, 1965; Armstrong and others, 1965; Minard and Booth, 1988; Troost, 

1999). Booth and Troost (2005) identified deposits formed during this time (unit Qob) by radiocarbon 

dating at several localities in the Olalla quadrangle (table 1). Deposition of sediments may have been 

more widespread during Olympia time than is indicated by the distribution of unit Qob on the map, 

because some Olympia nonglacial interval-age sediments are probably lumped less precisely into the 

lithostratigraphic units Qpf or Qpfn. Conversely, deposits mapped as pre-Olympia nonglacial interval in 
4

age (and so assigned to unit Qpo) are separated from either Fraser glaciation-age or radiocarbon-dated 

Olympia nonglacial interval-age deposits by at least one pre-Fraser glaciation-age glacial unit. 

Deposits of the Vashon Stade of the Fraser Glaciation of Armstrong and Others (1965) 

Most deposits at or near the constructional land surface are assigned to the youngest glacial 

advance in the Puget Lowland, the Vashon stade of the Fraser glaciation (Armstrong and others, 1965). 

During this time an ice sheet advanced along the axis of the lowland from the north (Clague, 1981), 

reaching its maximum extent about 17,000 (14,000 radiocarbon) yr B.P. and covering the Puget 

Lowland to a maximum depth of about 5,000 ft (1,500 m) (Waitt and others, 1983; Booth, 1987; Porter 

and Swanson, 1998). As the ice first advanced, it blocked northward lowland drainage out of the Strait 

of Juan de Fuca, which now connects Puget Sound with the Pacific Ocean. In the impounded lakes that 

formed in the course of establishing southerly drainage out of the Puget Lowland, laminated silt and clay 

were deposited broadly across the Puget Lowland. Booth and Troost (2005) tentatively assigned such 

lacustrine deposits flanking Olalla Valley and Colvos Passage to the Lawton Clay Member of Vashon 

Drift (unit Qvlc) on the basis of their texture and their stratigraphic position relative to the underlying 

dated deposits of the Olympia nonglacial interval (unit Qob) and pre-Olympia nonglacial interval 

deposits. 

Advance outwash deposits (Qva) deposited by streams derived from the advancing ice sheet 

mark the subsequent depositional interval. Sandy advance outwash deposits at least a few tens of meters 

thick (and locally as thick as 100 m [300 ft]) underlie the broad uplands in the central part of the 

quadrangle. This deposit (Qva) inundated the pre-Vashon stade topography of the lowland and resulted 

in a gently south-sloping landform (Booth, 1994), whose upper surface is as high as 430 ft (125 m) in 

the center of the quadrangle. The base of the advance outwash deposits is exposed along most of the 

deep valleys and coastal bluffs; its elevation varies between about 30 and 200 ft (10 and 60 m). This unit 

has been mapped by earlier workers (Mullineaux and others, 1965; Garling and others, 1965) as the 

Colvos Sand Member of Vashon Drift or the Esperance Sand Member of the Vashon Drift. 
5

Table 1. 14C ages from the Olalla quadrangle.

[Site names from source publication]

Lab. No. Site name

Location

based on 

topo base

Location

based on 

lidar base

Approx.

elev. in ft 

Topo. base

(Lidar 

base)

Sample 

type Sample No. Pretreatment

Conventional

14C age, in

yr B.P.1

13C/12C 

Ratio 

(o/oo)

Calibrated

age, in

yr B.P.2

Map

Unit Reference

Beta-131069 Maplewood 

south

47.3940 N.

122.5531 W.

47.394 N.

122.554 W.

70

(64)

peat DB-212-98

KT-13-98

acid/alkali/

acid

>41,420 -25.03 >41,420 Qpon Troost 

(1999)

W-1515 Crescent

coast

47.3872 N.

122.5488 W.

47.386 N.

122.549 W.

80

(84)

peat unknown >38,000 Not 

avail.

>38,000 Qpon Deeter 

(1979)

W-2028 Crescent

coast

47.3872 N.

122.5488 W.

47.386 N.

122.549 W.

?80

?(84)

peaty silt unknown >42,000 Not 

avail.

>42,000 Qpon Deeter 

(1979)

Beta-128806 Fragaria

road

47.4617 N.

122.5372 W.

47.461 N.

122.539 W.

80

(77)

peat DB-235-97 acid/alkali/

acid

40,660±970 -25.03 42,950–

38,850

Qob Troost 

(1999)

Beta-131071 Crescent 

driveway 

(upper)

47.3870 N.

122.5489 W.

47.386 N.

122.551 W.

140

(154)

organic 

sediment

KT-170-

99, S-5 

acid/alkali/

acid

(low C 

required 

special 

handling)

38,790±790 -25.03 40,650–

37,250

Qob Troost 

(1999)

Beta-131072 Crescent 

driveway 

(lower)

47.3870 N.

122.5489 W.

47.386 N.

122.551 W.

133

(154)

peat KT-170-

99, S-7 

acid/alkali/

acid

>44,290 -25.03 >44,290 Qob Troost 

(1999)

UW-25 Maplewood 

coast

47.3989 N.

122.5533 W.

47.408 N.

122.552 W.

125

(128)

peat unknown --4 Not 

avail.

--4 Qob Dorn and 

others 

(1962)

W-1982 Maplewood 

coast

47.3989 N.

122.5533 W.

47.408 N.

122.552 W.

1255

(128)

peat unknown >42,000 Not 

avail.

>42,000 Qob Yount and 

others 

(1980)

Beta-128805 Olalla Creek 

quarry

47.4265 N.

122.5542 W.

47.426 N.

122.556 W.

70

(78)

peat KT-11-98

DB-78-98

acid/alkali/

acid

39,050±940 -25.03 41,250–

37,250

Qob Troost 

(1999)

1

B.P. (before present) is, by convention, years before 1950 A.D.

2

Calibrated radiocarbon age (2-sigma range) 

3

Estimated 13C/12C ratio

4

Originally reported finite date was tritium-contaminated (Fairhall and others, 1966); stratigraphic assignment based on field relations

5

Elevation based on presumed duplication of site UW-25 (Deeter, 1979, p. 62–63) 
6

Table 2. Infrared-stimulated luminescence (IRSL) ages from the Olalla quadrangle. 

[Dates from S. Mahan, U.S. Geological Survey, written commun. 2002; Mahan and others, 2003 Ages reflect average of 10-

minute bleach (minimum age) and 60-minute bleach (maximum age) using CS-3-67 orange filter]

Lab No. Location and year of 

collection

Elevation (ft) Material Average IRSL age,

in ka

Map unit

WA-25 Sandford Point 2002 20 fine sand 127±6 Qpoc

WA-26 Sandford Point 2002 25 silt 185±9 Qpof

As ice covered the region, till (Qvt) was deposited by the meltout and reworking of debris at the 

base of the glacier. This heterogeneous and generally compact sediment blankets the area to depths that 

are, at most, tens of feet, but more typically are only 3 to 10 ft (1 to 3 m). Over much of the quadrangle, 

the ground surface underlain by this deposit is strongly fluted to the south-southwest. Remnants of this 

fluted texture on till and ice-contact deposits (Qvi) at lower valley elevations and in lower Olalla Valley 

on probable advance outwash (Qva) indicates significant scour beneath the ice. 

Deposits on the west side of the quadrangle, formerly mapped by Booth and Troost (2005) as 

recessional outwash, appear in the lidar topography to be mostly ice-contact deposits (Qvi), an 

interpretation supported by a sinuous ridge interpreted to be an esker (Qvie), located north of SE Burley 

Olalla Road on the west edge of the quadrangle. 

Shortly after 17,000 (14,000 radiocarbon) years ago, the ice margin, which by this time had 

advanced about 44 mi (70 km) south of the quadrangle, began to melt back. Recession of the ice sheet 

was accompanied by both outwash streams and ice-dammed lakes, analogous to those formed during the 

ice advance. When the Olalla quadrangle was uncovered by the retreating glacier, a proglacial lake 

already had inundated much of the central and southern Puget Lowland because water was impounded 

by the ice that still filled the northern Lowland. This water body, glacial Lake Russell, drained out 

through Black Lake, south of Olympia. into the Chehalis River many tens of kilometers to the south of 

the quadrangle (Thorson, 1980). Although the elevation of the Black Lake spillway is now only about 

135 ft (42 m), the ancient level of glacial Lake Russell is now higher because the entire Puget Lowland 

has rebounded since the removal of the ice sheet. More rebound occurred in the north than in the south 

because the ice load was greater to the north. Rebound in the Olalla quadrangle, relative to the Black 

Lake spillway, ranges from about 130 ft in the south to 165 ft in the north (40 to 50 m), and so the level 

of glacial Lake Russell during earliest deposition of recessional outwash deposits (Qvr) was at about 

260 to 300 ft (80 to 90 m) above the present-day elevation. 

The lidar DEM reveals deposits whose morphology suggests deposition underwater. Typically, 

the topographic features of such deposits are more rounded and fluid-looking than their subaerial 

equivalents. We mapped sublacustrine alluvial fans (Qvrlf) and landslides (Qvrls). Some alluvial fans 

are included in the sub-lacustrine group, because they not only occur at elevations that would have been 

below lake level, but also they are built out from drainages that could have flourished only while fed by 

melting ice.

Most horizontal lake deposits (Qvrl) in valley bottoms are probably covered by Holocene 

alluvium, but, on a promontory northwest of Olalla Bay, probable lake deposits are perched above 

Holocene depositional environments. 

The shoreline of glacial Lake Bretz has a present-day elevation of about 35 to 65 ft (10 to 20 m) 

across the quadrangle, 230 ft (70 m) lower than that of glacial Lake Russell. Glacial Lake Bretz was 

impounded by a spillway at the south end of Chimacum Valley, 30 mi (50 km) northwest of the 

quadrangle on the northeastern Olympic Peninsula. Continued ice retreat ultimately opened Admiralty 

Inlet, drained glacial Lake Bretz, and connected Puget Sound to the world ocean. At the time glacial 
7

Lake Bretz drained, the ice margin appears to have been far to the north of the Olalla quadrangle, thus 

fluvial activity could have consisted of only small creeks draining the local uplands, similar to the 

present day. This history leaves no mechanism for fluvial erosion of the large, roughly north–south 

valleys that traverse the map area, thus Booth and Troost (2005) deduced that they were formed by 

subglacial erosion. This was almost certainly subglacial fluvial erosion, because these valleys partly 

crosscut the upland indicators of ice-flow direction (Booth, 1994). As such, these large valleys are the 

central lowland equivalents of the "channelways" previously mapped along the eastern margin of the 

Puget Lowland (Booth and Hallet, 1993). 

Recessional outwash deposits are scattered across the upland areas, notably south and west of 

Long Lake, above Wilson Creek and Fragaria Creek in the northeast corner of the map, east of Purdy 

Creek, and on the upland areas of Vashon Island. The elevation of these deposits indicates they were 

probably graded to Lake Russell (Haugerud, 2009). We have approximated their relative ages by 

visualizing the retreat of the ice front in a northeasterly direction across the quadrangle (see for instance, 

Thorson, 1989). The lidar topography reveals multiple terraces in some of these deposits, indicating a 

change in base level or local uplift during terrace formation. A terrace-like deposit southwest of Long 

Lake (Qvis) with a down-to-the-northeast gradient is likely to be subglacial outwash from pressurized 

water flow uphill to the southwest. It nests in extensive ice-contact deposits (Qvi), supporting a 

subglacial origin, but it could be the youngest outwash of associated outwash terraces (Qvrla1, Qvrla2), 

but draining northeast after ice in the Olalla Valley to the northeast melted back or down and was 

deposited by melt from stagnant ice in the surrounding area. 

Booth and Troost (2005) identified relatively low elevation outwash materials in major valleys 

that lie lower than the maximum levels of Lake Russell, which they ascribed to outwash graded to a 

lowering Lake Russell or Lake Bretz. We now show some of these deposits as post-glacial alluvium 

(Qa), notably in Olalla Valley, Crescent Valley, and the valley of lower Purdy Creek. Some of this 

alluvium may overlie outwash or lake deposits. In some valleys lacking terrace morphology and that, in 

the lidar DEM, show glacial grooving, we interpret the materials to be eroded advance outwash (unit 

Qva). Some terraces may only be a thin veneer of outwash gravels on eroded older materials, and these 

are similarly included in the older deposit unless the present-day landforms suggest significant lateglacial or postglacial reworking. Probable wave-cut notches (primarily adapted from Haugerud, 2009) 

indicate lake shorelines above sublacustrine features discussed previously. Multiple terrace deposits in 

Burley, Goodnough, Olalla, Purdy, and Salmonberry Creeks are all too low to have been cut by water 

from the melting ice sheet, although the materials of the terraces are most likely remnants of recessional 

outwash (Qvrw) that built up in the valleys at one time. These terrace levels, similar to the higher 

outwash terraces, may represent change in base levels due to glacial rebound or, for some, rebound and 

(or) lowering of glacial Lake Bretz. Although individual terraces may correlate from drainage to 

drainage, their number designations here do not imply correlation. 

We recognized most landslides from the lidar DEM by their arcuate headwalls and bulbous toes, 

although the toes are not always obvious. We have queried 53 of 187 mapped landslides, indicating 

uncertainty in their identification. Some subaerial landslides (unit Qls) are incised by creeks or 

otherwise eroded, indicating greater age. Some of these may have formed as stagnant ice melted away in 

terrane mapped as unit Qvi. Composite landslide masses may have a large age range. Sublacustrine 

landslides (unit Qvrls) are generally more subdued, look smoothed, occur on lower slopes, and are at an 

appropriate elevation to have been under Lake Russell. Although older landslides may be more stable 

than younger ones, no implication of stability is intended in this landslide classification. This map is not 

suitable for site-specific land-use decisions.
8

Structure

The Olalla quadrangle occupies a region of known Holocene seismicity, deformation, and 

surface faulting (Bucknam and others, 1992; Johnson and others, 1996; Barnett and others, 2010). Most 

apparent displacements and truncations within the quadrangle, however, likely are the result of 

Holocene landsliding, depositional unconformities, or glacial overriding rather than tectonic movement. 

One fault of likely tectonic origin is mapped in the beach cliff north of Sandford Point, where preFraser-glaciation-age silt (Qpof) abuts sand (Qpoc) along a vertical surface. Bedding is strongly 

distorted along this fault; the deformation extends about 2 m into the adjacent silt. In contrast, the 

relatively gentle deformation that is widespread throughout the quadrangle almost certainly reflects 

longterm folding during the Quaternary period. Pre-Vashon-stade-age deposits in and around the map 

area define a regional pattern of fold axes striking west to west-northwest (Johnson and others, 2004; 

Booth and others, 2004b); the axis of an anticline is expressed by opposing dips just north of Sandford 

Point on Vashon Island, and a syncline axis is suggested by dips just south of Fragaria Creek. No such 

folding has been observed in sediments of Vashon stade age, but deposits of Olympia nonglacial interval 

age and older are deformed here and throughout the southern Puget Sound region. 

DESCRIPTION OF MAP UNITS

NONGLACIAL DEPOSITS

af Artificial fill (Holocene)—Manmade deposits of gravel, silt, sand, and soil. Includes 

broken rock. Areas mapped include rearranged or graded native materials and 

some excavated surfaces

Qbtf Beach and tidal flat deposits (Holocene)—Shoreward side of deposit is mostly well 

sorted sand, pebbles, and shells, deposited or reworked by wave action. 

Includes upper-beach deposits above mean high water line and local thin 

veneer of modern beach sediment that overlies older deposits. At stream 

mouths, grades into unit Qa or Qf, Grades seaward to silt, sand, and organic 

sediment and detritus; exposed in broad coastal intertidal benches at low tide. 

Contact with water is approximate; at low tide exposed width of these deposits 

may be 2 to 3 times that shown here. Occurs along shores of Colvos Passage 

Qw Wetland deposits (Holocene)—Peat and alluvium; poorly drained and intermittently 

wet

Qmw Mass-wasting deposits (Holocene)—Colluvium, soil, and landslide debris that has 

indistinct morphology, both in the field and on lidar DEM. Mapped by Booth 

and Troost (2005) where sufficiently thick and continuous to obscure 

underlying material. Numerous unmapped areas of mass-wasting deposits are 

present along coastal bluffs. Deposits, both mapped and unmapped, may 

include discrete landslides 3 to 35 ft (1 to 10 m) in lateral extent. Largest 

mapped areas are in southwest part of quadrangle

Qa Alluvium (Holocene and Pleistocene)—Moderately well sorted deposits of cobble 

gravel, gravel, sand, gravelly sand, and sandy silt; found along floodplains of 

lowland streams. Unit is gradational with, and locally includes, sediment 

equivalent to units Qf and Qb. Locally mapped as terrace sequences

Terrace sequences—Terrace sequences are numbered oldest to youngest (unit 1 

to n); except for the youngest deposits associated with modern streams, unit 

numbers do not imply correlation between drainages
9

Terraces along Burley Creek

Qab3 Alluvium of Burley Creek, unit 3 (Holocene)

Qab2 Alluvium of Burley Creek, unit 2 (Holocene and Pleistocene)

Qab1 Alluvium of Burley Creek, unit 1 (Holocene and Pleistocene)

Terraces along Goodnough Creek

Qag3 Alluvium of Goodnough Creek, unit 3 (Holocene) 

Qag2 Alluvium of Goodnough Creek, unit 2(Holocene and Pleistocene)

Qag1 Alluvium of Goodnough Creek, unit 1 (Holocene and Pleistocene)

Terraces along Olalla Creek

Qao2 Alluvium of Olalla Creek, unit 2 (Holocene)

Qao1 Alluvium of Olalla Creek, unit 1 (Holocene and Pleistocene)

Terraces along lower Purdy Creek

Qap2 Alluvium of Purdy Creek, unit 2 (Holocene)

Qap1 Alluvium of Purdy Creek, unit 1 (Holocene and Pleistocene)

Terraces along Salmonberry Creek

Qasb2 Alluvium of Salmonberry Creek, unit 2 (Holocene)

Qasb1 Alluvium of Salmonberry Creek, unit 1 (Holocene and Pleistocene)

Qf Fan deposits (Holocene)—Boulders, cobbles, pebbles, and sand deposited in lobate 

form where streams emerge from confining valleys and where reduced 

gradients cause sediment loads to be deposited

Qoa Older alluvium (Holocene and Pleistocene)—Similar to unit Qa. Mapped from 

lidar DEM where modern drainage insufficient for transport

Qfo Fan deposits, older (Holocene and Pleistocene)—Similar to Qf. On southwest coast 

of Vashon Island near Paradise Cove, separated from younger materials by 

low scarp. In Qlalla Valley, mapped where modern drainage insufficient for 

amount of material in fan

Qls Landslide deposits (Holocene and Pleistocene)—Diamictons composed of broken 

to internally coherent surficial deposits that are derived from upslope. Origin 

uncertain where queried (Qls?). Largely mapped on basis of topographic 

expression. Numerous unmapped areas of both landslide and related masswasting deposits also are found elsewhere in quadrangle, particularly where 

coarse deposits (units Qva and Qpog) overlie fine deposits (particularly units 

Qvlc, Qpogf, and Qpfn) 

YOUNGER GLACIAL DEPOSITS

 Deposits of the Vashon stade of the Fraser glaciation of Armstrong and others 

(1965) (Pleistocene)

Qvrlf Sublacustrine alluvial fans—Alluvial fans built under recessional lakes. Mapped 

from lidar based on shape and elevation. Although these fans, as mapped, may 

include some post-glacial alluvial fans (Qf), they occur at canyon mouths with 

limited drainage

Qvrls Sublacustrine landslides—Mostly built under Lake Russell, but slides at 

elevation under about 250 ft may have been built under Lake Bretz. Mapped 

from lidar DEM on basis of elevation and subdued, fluid appearance. May 

include some subaerial landslides (Qls) 
10

Qvrl Sublacustrine deposits—Probable bedded sands and silts deposited in Lake 

Russell and (or) Lake Bretz on a promontory northwest of Olalla Bay. 

Mapped from lidar DEM and identified by surface texture and elevation

Qvrw Recessional outwash deposits graded to Lake Russell—Stratified sand and 

gravel, moderately well sorted to well sorted; less common silty sand and silt. 

Exposed primarily in narrow sinuous channels, locally cross-cutting glacial 

flutes, and as irregular upland bodies having no obvious channelized form. 

Recessional outwash rarely exposed on floors of broad south-southwesttrending valleys (for instance, Purdy and Salmonberry Creeks), where floor 

sediments are mostly topped by alluvium (unit Qa) as mapped here. Narrow 

channel deposits are probably subglacial. Deposits less than about 1 m thick 

commonly overlie till but are not mapped. In north-central part of map, may 

include outwash of Lake Bretz age

Outwash in the SE Mullenix Road area—Three terraces graded to Lake 

Russell via Burley Creek

Qvrm3 Outwash of SE Mullenix Road, unit 3

Qvrm2 Outwash of SE Mullenix Road, unit 2

Qvrm1 Outwash of SE Mullenix Road, unit 1

Outwash in Bethel area—Four terraces graded to Lake Russell via Burley 

Creek 

Qvrb4 Outwash of Bethel, unit 4 

Qvrb3 Outwash of Bethel, unit 3

Qvrb2 Outwash of Bethel, unit 2

Qvrb1 Outwash of Bethel, unit 1

Outwash southwest of Long Lake—Two terraces graded to Lake Russell via 

Purdy Creek 

Qvrla2 Outwash of Long Lake, unit 2

Qvrla1 Outwash of Long Lake, unit 1

Outwash terraces and channel fills west of Peacock Hill Road SE—Three 

terraces graded to Lake Russell via Purdy Creek

Qvrp3 Outwash of Peacock Hill Road, unit 3

Qvrp2 Outwash of Peacock Hill Road, unit 2

Qvrp1 Outwash of Peacock Hill Road, unit 1

Outwash terraces and channel fills southeast of 160th Sreet NW—Two 

terraces graded to Lake Russell via Goodnough Creek 

Qvro2 Outwash of 160th Steet, unit 2

Qvro1 Outwash of 160th Steet, unit 1

Qvi Ice-contact deposits—Deposits similar in texture to unit Qvr but locally 

containing much higher percentage of silt intermixed with granular sediments; 

also includes lenses and pods of till. Locally characterized by hummocky 

topography and (or) closed depressions. Distribution of unit depicted by 

Booth and Troost (2005) modified extensively using lidar topography 

Qvie Esker—Recognized by sinuous form and positive relief. Found at 

westernmost edge of quadrangle
11

Qvis Probable subglacial outwash—Southwest of Long Lake 

Qvt Till—Compact diamicton containing subrounded to well-rounded clasts is 

glacially transported and deposited. Generally forms undulating surface. Unit 

is 3 to 10 ft (1 to 3 m) thick. Also found sporadically within areas mapped as 

unit Qvi

Qva Advance outwash deposits—Well-bedded sand and gravel deposited by streams 

and rivers that issued from front of advancing ice sheet. Generally unoxidized; 

almost devoid of silt or clay, except near base of unit. Includes deposits 

previously mapped by others as Colvos Sand or Esperance Sand Members of 

the Vashon Drift

Qvlc Lawton Clay—Laminated to massive silt, clayey silt, and silty clay deposited in 

proglacial or lowland lakes. Unequivocal evidence for glacial or nonglacial 

origin rarely present. Mapped deposits are assigned to this unit primarily on 

the basis of stratigraphic position, but some localities have nearby absolute 

age control 

OLDER GLACIAL AND NONGLACIAL DEPOSITS

Qpf Sedimentary deposits of pre-Fraser glaciation age (Pleistocene)—Weakly to 

moderately well oxidized sand and gravel, lacustrine sediments containing 

local peat layers, and moderately well to strongly oxidized diamicton 

composed of silty matrix and rounded gravel clasts. Exposed on northern part 

of Vashon Island 

Qpfn Nonglacial deposits—Abundant organic debris or pumice indicating nonglacial 

origin. Exposed in southwest corner of map 

Qob Olympia beds of Minard and Booth (1988) (Pleistocene)—Sand and silt thinly 

interbedded with some gravel layers and, locally, with abundant organic 

material. Deposited during the Olympia nonglacial interval by lowland 

streams or in floodplain and (or) lacustrine environments. Crops out in 

isolated areas on west side of Colvos Passage

Qpo Deposits of pre-Olympia age (Pleistocene)—Interbedded sand, gravel, silt and 

diamict. Very dense and hard Unit Qpo and its subunits crop out 

predominantly along the Colvos Passage, in the lower Olalla Valley, and in 

the southwest Purdy Creek drainage 

Qpoc Coarse-grained deposits—Predominantly gravel and sand, exposed in one small 

stretch of beach cliff on the west side of Vashon Island 

Qpof Fine-grained deposits—Predominantly silt and clay

Qpog Glacial deposits—Weakly to strongly oxidized silt, sand, and rare gravel of 

glacial origin. Underlies Vashon Drift till or Vashon Drift advance outwash

deposits and, thus, must also predate the last interglacial period (be of preOlympia nonglacial interval age) 

Qpogc Coarse-grained deposits—Predominantly gravel and sand 

Qpogf Fine-grained deposits—Predominantly silt and clay

Qpogt Till deposits—Predominantly till or other diamict

Qpon Nonglacial deposits—Deposits with abundant organic debris or pumiceous 

material indicating nonglacial origin

Qponc Coarse-grained deposits—Predominantly gravel and sand 
12

Qponf Fine-grained deposits—Predominantly silt and clay

Reversely magnetized deposits (Pleistocene)—Mapped along west side of Colvos 

Passage 

Qrgf Fine-grained glacial deposits—Fine silt that contains dropstones, so likely has 

glacial origin. Reversely magnetized and thus presumably more than 774,000 

years old (Hagstrom and others, 2002) 

Qrn Nonglacial deposits—Interbedded silt, sand, and gravel with local pumice clasts. 

Likely of nonglacial origin. Reversely magnetized and thus probably more 

than 774,000 years old (Hagstrom and others, 2002) 

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