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STATE OF WASHINGTON

DEPARTMENT OF NATURAL RESOURCES

BERT l. COLE, Commissioner of Public lands

DON LEE FRASER, Supervisor

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DIVISION OF GEOLOGY AND EARTH RESOURCES

VAUGHN E. LIVINGSTON, JR., State Geologist

GEOLOGIC MAP GM-20

PRELIMINARY SURFICIAL GEOLOGIC MAP OF THE

MUKILTEO AND EVERETT QUADRANGLES,

SNOHOMISH COUNTY, WASHINGTON

By

MACKEY SMITH

Prepared in cooperation with

UNITED STA TES GEOLOGIC.Al SURVEY

1976 For sale by Department of Natural Resources. O!vmoi

WASHINGTON DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGY AND EARTH RESOURCES

PREPARED IN COOPERATION WlfH fHE U.S. GEOLOGICAL SURVEY

PRELIMINARY SURFICIAL GEOLOGIC MAP of the MUKILTEO and EVERETT QUADRANGLES, SNOHOMISH COUNTY, WASHINGTON

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~ Alluv ium

Mostly sand ond grovel deposited by streams. Moy con­tain some silt, cloy, and organic material

~ Older alluvium

Mostly sand and gravel with some silt and cloy . Occurs as alluvial fons at the foot of steep volley sides. Processes that specifically deposited older alluvium ore no longer active

EJ Old landslides

Lorge slumps that occurred during the oblation of the Puget Lobe of the Vashon ice sheet by lowering of water- table level, Slides may have been active since original movement; locks evidence of recent movement

Vashon recessional outwosh

Light- brown loosely compacted sand and gravel . Dry grovel seeks angle of repose of 35°; wet gravel will stand in near-vertical cliff. Sorting varies; part icle size varies from medium sand to cobbles. Stones ore usually covered with o light-brown dusty coating and ore well rounded from stream transportation . Contains some ice contact deposits

~ Vashon till

Poorly sorted, nonstrotified lodgment till deposited as ground moraine. Mixture of clay, silt, sand, peb­bles, and cobbles with occas iona l large boulders. Appears gray to blue on fresh surface; may weather to brown or yel low, Extreme ly compact, will stand in near- vertical cliffs; generally locks surficial cracks or ioin ts . Stones are subongulor to rounded. Some larger closts show striations and faceting. Vertical faces sometimes spoil off in large blocks . Some areas of Ovt ore covered by a thin veneer of loose ly consolidated , nonsorted oblation till and(or) thin outwosh

Voshon advance autwash

Fresh, light- gray , stratified, compact sand and grovel. Will stand in near- verHcal cliff. Sorting varies; particle size varies from fine sand to coarse pebbles

Esperance Sand

Thinly bedded (from 2 to 6 inches), fresh, light- gray sand layers. Particle size varies from medium to coarse sand (with lO percent pebbles); small peb­bles often occupy the base of each individual bed or lens. Occasional lenses of coarse grovel occur. Usua ll y sloughs ta angle of repose on exposed slope~

Possession Drift

Sil~, cloys, and pebbly glociolocustrine silts; deformed by ice thrusting

Whidbey Formation

Generally medium-bedded (2 to 4 feet) sand, silt, and clay. Color varies from light brown to gray. Par­ticle siz e varies from cloy to coarse sand with a few lenses of small pebbles. Sorting is generally good within each individual bed. Clay and silt beds can be as thin as 2 inches. Nonglacial river flood - plain deposits . May show tectonic deforma­tion

~ Double SluH Drift

Contains: (1) iron-oxide cemented grave l, consisting of small to medium pebbles well cemented in a grit matrix; (2) pebbly glociolacustrine silts; and (3) massive si It and lesser beds of sand and grove l. Well compacted and will stand in a near- vertica l cliff. Pebbly sifts display des iccation crocks at the surface . Moy show tecton ic deformation

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Modified land

Original topography disturbed by removal of some Pleistocene deposits, grading, and artifici a l fil I of unknown quality

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By Mackey Smith

1976

EXPLANATION

~ Beach depasits

Mostly medium to coarse sand with some pebbles and cobbles; light gray, lacks compaction . May contain shell fragments and organic debris

}ti SCALE l24,000 l MILE

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Geology by Mackey Smith 19741 1975

Bose mop from U.S. Geologica l Survey

Mukilteo and Everett

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Deposi ts of ac ti ve slumps, slides, and a reas of flowoge. Accumulations of organ ic material. May\Contoin smal 1 "'mounts of sand silt, clay, and-VOicanic ash , 1'10101 ~

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May include some deposits of old landslides. Shows evidence of recent movement

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GEOLOGIC MAP GM-20

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