Permian rocks

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.
State Washington
Name Permian rocks
Geologic age Permian-Triassic
Lithologic constituents
Metamorphic > MetasedimentaryIncludes metachert, meta-argillite, metaconglomerate, metawacke, and metasiltite.
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Metamorphic > Metaigneous > Greenstone
Sedimentary > Chemical > Chert (Bed)Possibly only incidental in rank.
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Metaigneous > Metavolcanic
Sedimentary > Clastic > Siltstone (Bed)
Igneous > Volcanic (Flow, Pyroclastic-tuff)
Metamorphic > Metasedimentary > Metacarbonate > Marble
Sedimentary > Clastic > Sandstone > Graywacke (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Igneous > Plutonic > Dioritic > DioriteMostly meta-diabase.
Metamorphic > Metasedimentary > Metaclastic > Argillite
Sedimentary > Clastic > Conglomerate (Bed)
Comments Stoffel and others, 1991, report that while the term "Mission argillite" was once widely used, it has since been abandoned. Many workers report that these rocks are at least partly metamorphosed.
Stratigraphic units Mission argillite; Orcas group (in part); Rossland volcanic group (in part); Mt. Roberts Formation

Huntting, M.T., Bennett, W.A.G., Livingston, V.E.Jr., and Moen, W.S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.

Weaver, C.E., 1920, The Mineral Resources of Stevens County: Washington Geological Society Bulletin No. 20, 350 p.

Stoffel, K.L., Joseph, N.L., Waggoner, S.Z., Gulick, C.W., Korosec, M.A., Bunning, B.B., 1991, Geologic Map of Washington--Northeast Quadrant: Washington Division of Geology and Earth Resources Geologic Map, GM-39, scale 1:250,000.

Yates, R.G., 1971, Geologic Map of the Northport Quadrangle, Washington: U. S. Geological Survey Miscellaneous Geologic Investigations Map I-603, scale 1:31,680.

Dragovich, J.D., Logan, R.L., Schasse, H.W., Walsh, T.J., Lingley, W.S., Jr., Norman, D.K., Gerstel, W.J., Lapen, T.J., Schuster, J.E., Meyers, K.D., 2002, Geologic Map of Washington-Northwest Quadrant: Washington Division of Geology and Earth Resources Geologic Map GM-50, scale 1:250,000.

Brandon, M.T., Cowan, D.S., Vance, J.A., 1988, The Late Cretaceous San Juan thrust system, San Juan Islands, Washington: Geological Society of America Special Paper 221, 81 p. 1 pl.

NGMDB product
Counties Ferry - San Juan - Skagit - Snohomish - Stevens - Whatcom