Cretaceous sedimentary rocks, mostly marine

Lower Cretaceous greenish-gray massive arkosic sandstone and light-gray sandy shale in western Okanogan County. Includes phyllite in eastern Whatcom County.
State Washington
Name Cretaceous sedimentary rocks, mostly marine
Geologic age Cretaceous
Lithologic constituents
Sedimentary > Clastic > Sandstone > Arkose (Bed)
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Sedimentary > Clastic > Conglomerate (Bed)
Comments Huntting and others, 1961, (source map) references a 1958 unpublished map by Barksdale when including the Virginian Ridge Formation in this unit but more recent mapping by Barksdale (1975) shows that most of the Virginian Ridge Formation is actually in Huntting's WAKu unit (Winthrop Sandstone). Goat Creek Formation is 5120 ft thick, mostly arkose (80%), black shale (20%) and incidental conglomerate; Panther Creek Formation is 5200 ft thick, mostly black shale (90%), conglomerate (6%), and arkose (4%); Harts Pass Formation is 7900 ft thick, mostly arkose (70%) and black shale (30%) (Barksdale, 1975--NOTE: uses black shale interchangeably with argillite).
Stratigraphic units Virginian Ridge Formation (in part); Harts Pass Formation; Panther Creek Formation; Goat Creek Formation; Jack Mountain Phyllite

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.

Misch, P., 1977, Bedrock Geology of the North Cascades, in Brown, E. H. and Ellis, R. C. (eds.), Geological Excursions in the Pacific Northwest, Geological Society of America 1977 Annual Meeting, Seattle: Western Washington University, p. 1-62.

Barksdale, J.D., 1975, Geology of the Methow Valley, Okanogan County, Washington: Washington Division of Geology and Earth Resources Bulletin no. 48, 72 p.

NGMDB product
Counties Okanogan - Skagit - Whatcom