DESCRIPTION OF MAP UNITS

Nonglacial deposits

Artificial fill (Holocene)—Mud, sand, and gravel of varying proportions, possibly including foreign

debris such as concrete, logs, timbers, or brick. Used for highway roadbeds and other construction.

Thickness generally greater than 2 m. Mapped where fill substantially obscures or has altered original

geologic deposit.

Beach deposits (Holocene)—Soft sand, silt, and mud deposited or reworked by wave or tidal action

at head of Port Discovery. Contains logs and timbers at or above high tide. Deposits lie within 2 m

of high tide.

Alluvial fan deposits (Holocene)—Boulders, cobbles, and soft sand deposited in lobate form where

streams emerge from confining valleys and reduced gradients cause sediment loads to be deposited.

Alluvium (Holocene)—Moderately sorted soft deposits of cobble gravel, pebbly sand, and sandy silt

along the floodplain of Snow and Salmon Creeks south of Port Discovery, and along Snow Creek

in the northwest corner of the map. Gradational with and including sediment equivalent to unit Qb

Wetland deposits (Holocene and late Pleistocene)—Peat, marsh, and bog deposits, with some

intermixed sand, silt, and clay. Unit is very soft, water saturated, and occupies shallow depressions

in till (Qvt) or low-lying areas of recessional outwash sands (Qvrs).

Landslide deposits (Holocene and late Pleistocene)—Diamicton of angular clasts of bedrock and

surficial deposits derived from upslope and commonly includes trees. Includes areas of irregular,

hummocky topography. Poorly consolidated. Landslide four kilometers south of Port Discovery

consists of house-sized blocks of Lyre Formation conglomerate.

af

Qb

Qf

Qal

Qw

Qls

Qvv

Qvrf

CORRELATION OF MAP UNITS

Unconformity

Qci

Qval

Qvas Qvag

Qvt

af Qb Qf Qal Qw Qls

Qvrs Qvrg

Holocene

Pleistocene QUATERNARY

TERTIARY

Tems

T a Tebs

Tss

Tluc

Tlav

Tllc

Tl

Unconformity

Unconformity

Tcs

Tcb T Tcfb

middle Eocene

lower Eocene

upper Eocene
Glacial deposits

DEPOSITS OF VASHON STADE OF FRASER GLACIATION OF ARMSTRONG AND OTHERS (1965)

(PLEISTOCENE)—Consists of:

Sand-dominated recessional outwash deposits (late Pleistocene)—Stratified unconsolidated sanddominated sand and gravel deposits. Occupies lower parts of lower Snow Creek-Crocker LakeLeland Lake valley. May include interbeds of gravel-dominated recessional outwash deposits (Qvrg)

Gravel-dominated recessional outwash deposits (late Pleistocene)—Stratified unconsolidated graveldominated sand and gravel deposits. Occupies lower margins of lower Snow Creek-Crocker LakeLeland Lake valley, but lies higher than sand-dominated recessional outwash deposits (Qvrs). May

include interbeds of sand-dominated recessional outwash deposits (Qvrs)

Fine-grained recessional glaciomarine or glaciolacustrine deposits (late Pleistocene)—Stratified

firm fine silt with rounded dropstones of pebbles and cobbles along Highway 20, southeast of Port

Discovery. Coarse silt and sand are interbedded. Beds are greater than 3-10 cm thick. Some contacts

between beds are convoluted, and sand dikes and blobs are present and cross bedding. Overlies

probable till

Till (late Pleistocene)—Compact and firm light to dark gray non-stratified diamict containing subangular

to well-rounded clasts, glacially transported and deposited. Clasts are commonly granitic and were

derived from the Cascade Range or Canada. Often overlies advance outwash deposits (units Qval,

Qvas, Qvag) in the eastern part of the quadrangle and bedrock in the western part of the quadrangle.

Generally forms an undulating surface a few meters to a few tens of meters thick. However, west

of Crocker Lake more than 75 m of till is exposed

Valley-fill glacial and glaciofluvial deposits (late Pleistocene)—Bedded sandy-matrix clast-rich

compact diamict with angular clasts and a few large boulders, interbedded with firm fine to coarse

sand and silt, and clast-poor clayey matrix diamict, which we consider as till. Clasts are commonly

basaltic with probable local provenance. Occupies the headwaters of the Little Quilcene River

drainage in the southwestern part of the map area

Sand-dominated advance outwash deposits (late Pleistocene)—Well-bedded, sand-dominated compact

sand and gravel deposits. May have interbeds of silt or clay. Deposited by streams and rivers issuing

from front of advancing ice sheet

Gravel-dominated advance outwash deposits (late Pleistocene)—Well-bedded gravel-dominated

compact sand and gravel deposits. Almost devoid of silt or clay, except near base as discontinuous

beds. Deposited by streams and rivers issuing from front of advancing ice sheet

Advance outwash lake deposits (late Pleistocene)—Laminated to massive silt, clayey silt, and silty

clay deposited in a lowland lake south of Port Discovery. Sediment is firm. Inferred to be proglacial

because it is overlain by sand-dominated advance outwash sediments

Indurated colluvium (Pleistocene?)—Indurated unsorted iron-stained angular colluvium on flanks

of the Olympic Mountains in the southwestern part of map area. Inferred to predate Vashon stade,

because sediment is indurated and lying on bedrock

Bedrock

Micaceous sediments (Eocene?)—Massive buff brown micaceous siltstone and fine sandstone on the

north side of Big Skidder Hill. Bedding commonly indistinct or not present. May be correlative to

Scow Bay sandstone or the upper Eocene and lower Oligocene Makah Formation, the upper Oligocene

Pysht Formation, and the Miocene Clallam Formations at northwestern tip of Olympic Peninsula,

where these formations are described as micaceous by Snavely and others (1993) and Garver and

Brandon (1994)

Sandstone of Snow Creek—Sandstone and silty sandstone turbidites. Beds 5 cm to 1 m thick. Contains

channelized interbeds of pebble and granule conglomerate and siltstone up to 1 m thick. Clasts are

dominantly quartz and chert. Foraminifera indicate an upper Narizian age (Spencer, 1984)

Qvrs

Qvrg

Qvt

Qvas

Qvag

Qval

Qci

Tss

Tems

Qvv

Qvrf
LYRE FORMATION (MIDDLE EOCENE) divided into:

Upper conglomerate member—Pebble and cobble conglomerate in a matrix of medium to coarse

granule sand. Contains some sandstone interbeds. Dominantly chert, basalt, and conglomerate clasts

in decreasing order of abundance (Spencer, 1984). Clasts to 1 m

Andesite tuff and breccia—Andesite and hornblende andesite tuff and breccia, white to light gray.

Locally contains rare leaves and coalified wood. Commonly massive, but some tuffs are thin bedded

Lower conglomerate member—West of Cedar Flat unit is predominantly thick bedded to massive

conglomerate; to the south thin to thick bedded sandstone with minor conglomerate is most common.

Conglomerates are composed of well rounded pebbles and cobbles of chert with lesser amounts of

metasedimentary and igneous rocks, quartz, and graywacke. Lower part of unit south of Snow Creek

locally includes some angular to rounded basalt clasts. Sandstones are fine to coarse- grained and

commonly contain scattered pebbles. Siltstone is sandy and thinly to faintly bedded. Hornblende

separates from an andesite boulder in this unit collected just west of the quadrangle boundary, near

Mount Zion, yield K-Ar ages of 35.5 and 41.0 Ma (Yount and Gower, 1991). However, Spencer’s

(1984) biostratigraphic work indicates member is middle Eocene in age, and therefore it is likely

there was some argon loss in the samples analyzed

Lyre Formation, undifferentiated—Pebble and cobble conglomerate in a matrix of medium to coarse

granule sand. Contains some sandstone interbeds. Dominantly chert, basalt, and conglomerate clasts

in decreasing order of abundance. Clasts to 1 m. (data from Spencer, 1984). No direct fossil control

on age, but because it lies between the Narizian Aldwell Fm. and the upper Narizian sandstone of

Snow Creek, it is probably lower Narizian (Spencer, 1984)

Aldwell Formation (middle Eocene)—Massive to bedded slope mudstone and turbidite sandstone,

basaltic conglomerate, lithic sandstone, and siltstone. No fossils have been dated from within the

quadrangle, but along strike on the east side of Quilcene Bay foraminifera indicate an early Narizian

age (Spencer, 1984), where the section is almost 300-m thick. Coeval with Eocene basaltic sediments

(Tebs)

Basaltic sediments (middle Eocene)—Basaltic conglomerate and breccia, fine- to medium-grained,

dark gray to black massive sandstone, with thin local interbeds of dark siltstone. Lowermost few

meters is gray-green argillaceous limestone pods and basaltic sedimentary breccia. Total thickness

is approximately 230 m along Salmon Creek; benthic foraminifera and molluscs indicate age of

section ranges from upper Ulatisian to lower Narizian (Spencer, 1984)

Tluc

Tlav

Tllc

Tebs

T a

Tl
CRESCENT FORMATION (LOWER AND MIDDLE EOCENE) divided into:

Basalt flows—Massive basaltic lava flows. May contain calcite or zeolite-filled amygdules. Lava may

contain pyroxene phenocrysts. Tops of flows may have red oxidized zones indicating subaerial

eruption. May contain minor basaltic breccia (Tcb)

Basalt breccia—Rubbly, reddish weathering angular basaltic breccia. No silty or sandy matrix, indicating

subaerial eruption of lava. May contain minor basalt flows (Tcf)

Basalt flows and breccia—Rubbly, reddish weathering angular basaltic breccia, and massive basaltic

lava flows in roughly equal proportions. Breccia contains no silty or sandy matrix and lava flows

may have red oxidized zones

Basaltic submarine deposits—Pillow lava and pillow and lapilli breccia, amygdular lava flows, dark

gray calcareous mudstone, basaltic siltstone and sandstone. Intruded by basaltic sills. At head of

Quilcene River sandstone makes up approximately half of section. East of quadrangle at Olele Point,

Crescent Formation contains marine siltstone and sandstone with Ulatsian foraminifera (Yount and

Gower, 1991). At Bon Jon Pass, 1 km west of the southwest corner of the quadrangle, calcareous

nannoplankton from the top of this unit are referred to the CP 11 zone, or early Eocene (D. Bukry,

written communciation, 1998)

Tcf

Tcb

Tcfb

D

U

EXPLANATION

Contact — Dashed where approximately located; dotted where concealed

Fault — Sense of offset uncertain; dashed where approximately located;

dotted where concealed

Fault — U, upthrown side; D, downthrown side

Reverse fault —Dashed where approximately located; dotted where concealed

Fault — Showing relative horizontal movement; dashed where approximately

located; dotted where concealed

Syncline — Dashed where approximately located, dotted where covered

Anticline — Dashed where approximately located

Tcs