Pre-Upper Jurassic gneiss (WApJgn;0)

State	Washington
Name	Pre-Upper Jurassic gneiss
Geologic age	Mostly Cretaceous
Original map label	pJgn
Comments	Skagit gneiss is primarily biotite gneiss with some hornblende gneiss; Methow gneiss is entirely biotite gneiss with some retrogression to schist at fault contacts (Barksdale, 1975). Skagit gneiss ranges from the staurolite-kyanite zone to sillimanite grade (Misch, 1977). Granitic plugs and dikes (of Skagit gneiss) are Tertiary in age (Stoffel and others, 1991); all metamorphic rocks are no younger than Cretaceous in age. This unit may also include paragneiss. The Chiwaukum Schist is a Barrovian sequence of metasedimentary rocks and some metavolcanic rocks (Duggan and Brown, 1994).
Primary rock type	biotite gneiss
Secondary rock type	orthogneiss
Other rock types	migmatite; schist; marble; amphibolite; quartzite; phyllite; greenschist; granite
Lithologic constituents	Major Metamorphic > Gneiss Incidental Igneous > Plutonic > Granitic (Dike or sill) Metamorphic > Schist (Greenschist) Metamorphic > Phyllite Metamorphic > Migmatite Metamorphic > Quartzite Metamorphic > Amphibolite Metamorphic > Marble Metamorphic > Schist
Map references	Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., Moen, W. S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.
Unit references	Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., Moen, W. S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000. 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. Cater, F. W. and Wright, T. L., 1967, Geologic Map of the Lucerne Quadrangle, Chelan County, Washington: U. S. Geological Survey Geologic Quadrangle Map GQ-647, scale 1:62,500. [http://pubs.er.usgs.gov/publication/gq647] Cater, F. W. and Crowder, D. F., 1967, Geologic Map of the Holden Quadrangle, Snohomish and Chelan Counties, Washington: U. S. Geological Survey Geologic Quadrangle Map GQ-646, scale 1:62,500. [http://pubs.er.usgs.gov/publication/gq646] 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. 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. [http://pubs.er.usgs.gov/publication/i1963] Tabor, R. W., Frizzell, V. A., Jr., Whetten, J. T., Waitt, R. B., Swanson, D. A., Byerly, G. R., Booth, D. B., Hetherington, M. J., Zartman, R. E., 1987, Geologic Map of the Chelan 30-Minute by 60-Minute Quadrangle, Washington: U. S. Geological Survey Miscellaneous Investigations Series Map I-1661, scale 1:100,000. [http://pubs.er.usgs.gov/publication/i1661] Adams, J. B., 1964, Origin of the Black Peak Quartz Diorite, Northern Cascades, Washington: American Journal of Science, v. 262, no. 3, p. 290-306. 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. Duggan, K. M. and Brown, E. H., 1994, Correlation of the Tonga Formation and Chiwaukum Schist, North Cascades, Washington: Implications for Late Cretaceous orogenic mechanisms: Tectonics, v. 13, no. 6, p. 1411-1424.
Geographic coverage	Chelan - Douglas - King - Kittitas - Okanogan - Skagit - Snohomish - Whatcom