Upper Jurassic-Lower Cretaceous sedimentary and volcanic rocks

Predominantly sedimentary rocks. Graywacke, argillite, and siltstone with some slate and phyllite; includes graywacke breccia and ribbon chert with minor local limestone lenses and basalt flows.
State Washington
Name Upper Jurassic-Lower Cretaceous sedimentary and volcanic rocks
Geologic age Late Jurassic-Early Cretaceous
Lithologic constituents
Metamorphic > Metasedimentary > Metaclastic > Argillite
Sedimentary > Clastic > Sandstone > Graywacke (Bed)
Metamorphic > Metaigneous > Greenstone
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Sedimentary > Clastic > Sandstone > Arkose
Igneous > Plutonic > Dioritic > Diorite (Diabase)
Sedimentary > Chemical > Chert (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Comments Dragovich and others, 2002, maps this unit as metamorphosed sandstone, argillite, mudstone, and conglomerate with localized semischist, phyllite, chert, limestone, siltstone, greenstone, diabase, and gabbro. Huntting and others, 1961, originally listed"Leech River Group" in the stratigraphy of this unit; obsolete term and now considered part of Lummi Group (Brandon and others, 1988). Also includes "semischist" (Tabor and others, 1988, Dragovich and others, 2002). Misch, 1966, describes the Nooksack group as phylllitic but composed of graywackes, siltstone, and minor conglomerate.
Stratigraphic units Lummi Group (in part); Nooksack group (in part); Trafton melange

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.

Easterbrook, D.J., 1976b, Geologic Map of Western Whatcom County, Washington: U.S. Geological Survey Miscellaneous Investigations Series Map I-854-B, scale 1:62,500.


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.

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., Haugerud, R.A., Booth, D.B., Brown, E.H., 1994, Preliminary Geologic Map of the Mount Baker 30- by 60-Minute Quadrangle, Washington: U. S. Geological Survey Open File Report 94-403, 55p., 2 pls.

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.

Misch, P., 1966, Tectonic evolution of the northern Cascades of Washington--A west-cordilleran case history. In Canadian Institute of Mining and Metallurgy; and others, A symposium on the tectonic history and mineral deposits of the western Cordillera in British Columbia and neighboring parts of the United States, Vancouver, 1964: Canadian Institute of Mining and Metallurgy Special Volume 8, p. 101-148, 1 pl.

NGMDB product
Counties King - Skagit - Snohomish - Whatcom