Mineral Resources On-Line Spatial Data
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Geologic units in San Juan county, Washington
[Additional scientific data in this geographic area]
- Upper Jurassic-Lower Cretaceous sedimentary and volcanic rocks (Late Cretaceous-Jurassic) at surface, covers 4 % of this area
Sedimentary and volcanic rocks, undivided. Graywacke, argillite, siltstone, slate, volcanic rocks, phyllite, greenschist, and greenstone.
- Triassic sedimentary rocks, undivided (Triassic with Permian where impossible to differentiate) at surface, covers 10 % of this area
Predominantly limestone, marble, and dolomite near Riverside in Okanogan County. Conglomerate, shale, graywacke, gritstone, and limestone on San Juan Island. Siltstone with greenstone locally on Orcas Island. Graywacke conglomerate, cherty greenstone, and limestone in northern Ferry County.
- Permian rocks (Permian-Triassic) at surface, covers 6 % of this area
Conglomerate, graywacke, siltstone, argillite and interbedded fossiliferous limestone, greenstone, and minor angular conglomerate in northwestern Stevens and Ferry Counties. Impure quartzite, sandstone, graywacke, greenstone, ribbon chert, chert breccia, and limestone in Snohomish County and on San Juan Island. Lower Permian limestone on Black Mountain in northwestern Whatcom County. Middle Permian rocks in northeastern Washington.
- Pre-Tertiary sedimentary and metasedimentary rocks, undivided (Mostly Early Cretaceous to Middle Jurassic, possibly includes minor Eocene rocks) at surface, covers 13 % of this area
Graywacke, argillite, phyllite, chert, talc, and graphite schist; some faulted-in blocks of serpentinite and greenstone. Includes minor limestone on San Juan Island.
- Pre-Tertiary metamorphic rocks, undivided (Probably Permian) at surface, covers 0.2 % of this area
Schist, gneiss, marble, quartzite, amphibolite, greenstone, metaconglomerate, graywacke; includes metasedimentary, volcanic, and intrusive rocks. Some areas, as on San Juan Islands, show little if any metamorphism.
- Cretaceous sedimentary rocks, mostly marine (Late Cretaceous; possibly Eocene) at surface, covers 3 % of this area
Cretaceous conglomerate, sandstone, shale, breccia, limestone, and gritstone in San Juan Islands.
- Carboniferous rocks (Late Devonian to Mississippian) at surface, covers 2 % of this area
Thin-bedded graywacke, shale, argillite, slate, schist, volcanic breccia, gritstone, conglomerate, and limestone on northeast shore of Orcas Island. Limestone or dolomitic limestone, apparently interbedded with limy argillite and graywacke, forms belt of small separate outcrops between Springdale and Valley in southeastern Stevens County. Late Devonian to Early Pennsylvanian in age.
- Upper Jurassic-Lower Cretaceous volcanic rocks (Jurassic-Cretaceous on San Juan Islands; possibly Eocene in King County) at surface, covers 3 % of this area
Predominantly volcanic rocks, mostly metamorphosed to greenstone and greenschist; includes some sedimentary rocks
- Glacial drift, undivided (Pleistocene) at surface, covers 32 % of this area
Glacial and glaciofluvial sand, gravel, and till; includes alpine glacier outwash and till as well as some Recent alluvium.
- Pre-Carboniferous intrusive rocks (Paleozoic) at surface, covers 9 % of this area
Meta-quartz diorite, hypersthene diorite, and gneissose and directionless quartz diorite of eastern Skagit County. Quartz diorite and diorite in the San Juan Islands. Includes amphibolite and gneiss locally.
- Devonian rocks (Devonian to Permian) at surface, covers 2 % of this area
Thin alternating beds of cherty quartzite and argillite, occasional limestone lenses, volcanic rocks, sandstone, and graywacke on northwest shore of Orcas Island. Small outcrops of Devonian limestone included under Pzu in southeastern Stevens County and under PMPms in northwestern Whatcom County.