Pre-Tertiary volcanic rocks, undivided

Andesite and basalt flows, and greenstone; includes minor interbedded limestone, arkose, quartzite, and chert beds.
State Washington
Name Pre-Tertiary volcanic rocks, undivided
Geologic age Probably mostly Jurassic
Lithologic constituents
Major
Metamorphic > Metaigneous > Greenstone
Minor
Metamorphic > SchistIncludes greenschist, muscovite schist, quartz schist, and hornblende schist; relative abundances unknown.
Metamorphic > MetasedimentaryIncludes metaconglomerate, metasandstone, and any limestone or arkose mentioned in original description; relative abundances unknown.
Igneous > Plutonic > Dioritic > DioriteIncludes metadiorite and meta-quartz diorite.
Incidental
Metamorphic > Metasedimentary > Metaclastic > Argillite
Metamorphic > Metaigneous > Serpentinite
Igneous > Plutonic > Gabbroic > Gabbro (Flow)Includes metagabbro.
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Metamorphic > Metaigneous > MetavolcanicIncludes metadacite, metamorphosed basalt and any andesite, but no greenstone.
Sedimentary > Chemical > Chert (Bed)
Metamorphic > Amphibolite
Metamorphic > Metasedimentary > Metacarbonate > Marble
Igneous > Plutonic > Ultramafic
Comments Tabor and others, 1982, maps the outcrops in central Washington as diabase and gabbro with some recrystalization to amphibolite; they assign these rocks to the Ingalls Tectonic Complex and consider them to be Early Cretaceous to Late Jurassic in age. Dragovich and others, 2002, describes this central outcrop as metamorphosed diabase, gabbro, diorite, and basalt, locally mylonitic, with minor argillite and chert. Huntting and others, 1961, lists "Eagle Cliff porphyrite" among the stratigraphic units in this unit and indicates that it is found in the San Juan Islands; however, they do not map any outcrop of this unit in the San Juan Islands.
References

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.

Tabor, R.W., Waitt, R.B.,Jr., Frizzell, V.A.,Jr., Swanson, D.A., Byerly, G.R., Bentley, R.D., 1982, Geologic Map of the Wanatchee 1:100,000 Quadrangle, Central Washington: U. S. Geological Survey Miscellaneous Investigations Series Map I-1311, 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.

NGMDB product
Counties Chelan - Kittitas - Skagit - Snohomish