Pre-Tertiary sedimentary and metasedimentary rocks, undivided

Graywacke, argillite, phyllite, chert, talc, and graphite schist; some faulted-in blocks of serpentinite and greenstone. Includes minor limestone on San Juan Island.
State Washington
Name Pre-Tertiary sedimentary and metasedimentary rocks, undivided
Geologic age Mostly Early Cretaceous to Middle Jurassic, possibly includes minor Eocene rocks
Lithologic constituents
Sedimentary > Clastic > Sandstone > Graywacke (Bed, Tuffaceous)Includes volcaniclastic sandstone of Constitution Formation.
Metamorphic > Metasedimentary > Metaclastic > Argillite
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Metamorphic > Metaigneous > Greenstone
Metamorphic > Metaigneous > Serpentinite
Metamorphic > SchistIncludes greenschist.
Sedimentary > Chemical > Chert (Bed)
Sedimentary > Carbonate > Limestone
Igneous > Volcanic > Felsic-volcanic > Dacite (Flow, Flow-pillows)Includes dacitic pillows in Constitution Formation.
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow, Flow-pillows)Includes basaltic pillows in Constitution Formation.
Metamorphic > Metasedimentary > Metacarbonate > MarbleBelongs to Denny Formation.
Metamorphic > Granoblastic > HornfelsInterbedded with marble of Denny Formation.
Comments Huntting and others, 1961, originally listed "Leech River Group" in the stratigraphy of this unit; obsolete term and now considered part of the Lummi (see WAJK, WAJKs, and WAJKv) and Constitution Formations (see also WATR). Late Cretaceous metamorphic assemblages of prehnite, lawsonite, and aragonite are well developed in the Constitution and a prehnite isograd has been recognized (Brandon and others, 1988). Note that Brandon and others, 1988, does NOT mention limestone within the Constitution Formation and because of this, I do not include it in the lithology coding below. Also note that most of the Darrington Phyllite is in unit WApJph (rather than this one) with the exception of some outcrops in the western part of Whatcom and Skagit Counties (Lapen, 2000); similarly there appears to be a little Chuckanut Formation in this unit though most of it is within unit WAEPKc (Whetten and others, 1988). The Denny Formation consists of a few relatively small outcrops in Kittatas County adjacent to the Guye Formation (of which it was once thought to belong--see unit WAEPKc); the outcrops are primarily marble with interbedded hornfels (Foster, 1960). None of the referenced literature mentioned talc.
Stratigraphic units Denny Formation; Haystack terrane; Constitution Formation (in part: San Juan and Shaw Islands); Darrington Phyllite (in part); Chuckanut Formation (in small part)

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.

Foster, R.J., 1960, Tertiary Geology of a Portion of the Central Cascade Mountains, Washington: Geological Society of America Bulletin v. 71, no. 2, p. 99-126.

Tabor, R.W., Frizzell, V.A.,Jr., Booth, D.B., Waitt, R.B., Whetten, J.T., Zartman, R.E., 1993, Geologic Map of the Skykomish River 30- by 60-Minute Quadrangle, Washington: U. S. Geological Survey Miscellaneous Investigations Series Map I-1963, scale 1:100,000.

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.

Lapen, T.J., 2000, Geologic Map of the Bellingham 1:100,000 Quadrangle, Washington: Washington Division of Geology and Earth Resources Open File Report 2000-5, 36 p., 2 pl.

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.

Tabor, R.W., Frizzell, V.A., Jr., Booth, D.B.., Waitt, R.B., 2000, Geologic Map of the Snoqualmie Pass 30 x 60 Minute Quadrangle, Washington: U. S. Geological Survey Geologic Investigations Series I-2538, 57 p., 1 pl.

Tabor, R.W., Booth, D.B., Vance, J.A., Ford, A.B., Ort, M.H., 1988, Preliminary geologic map of the Sauk River 30 by 60 minute quadrangle, Washington: U. S. Geological Survey Open File Report 88-692, 51 p., 1 pl.

Whetten, J.T., Carroll, P.I., Gower, H.D., Brown, E.H., Pessl, F., Jr., 1988, Bedrock Geologic Map of the Port Townsend 30- by 60-Minute Quadrangle, Puget Sound Region, Washington: U. S. Geological Survey Miscellaneous Investigations Series Map I-1198-G, scale 1:100,000.

NGMDB product
Counties King - San Juan - Skagit - Snohomish - Whatcom