PRELIMINARY SURFICIAL GEOLOGIC MAP OF THE PRELIMINARY SURFICIAL GEOLOGIC MAP OF THE MUKILTEO AND EVERETT

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  • 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 con- tain 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 Processes that specifically deposited older alluvium ore no longer active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, peb- bles, 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 peb- bles 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. Par- ticle 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 deforma- tion

    ~ 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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    GEOLOGIC MAP GM-20

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