Lower Tertiary volcanic rocks, undivided (WAlTv;0)

State	Washington
Name	Lower Tertiary volcanic rocks, undivided
Geologic age	Eocene
Original map label	lTv
Comments	More recent maps show that this unit is predominantly basalt and rhyolite with subordinate andesite and dacite (including Silver Pass volcanic) (Luedke, 1998, Tabor and others, 1988, 1993, Dragovich and others, 2002). Barlow Pass volcanics mostly altered to "dense mat" of chlorite, epidote, calcite, and sericite (Tabor and others, 1988, 1993).
Primary rock type	basalt
Secondary rock type	rhyolite
Other rock types	andesite; dacite; sandstone; conglomerate; shale; argillite
Lithologic constituents	Major Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow) Igneous > Volcanic > Mafic-volcanic > Basalt (Flow) Minor Igneous > Volcanic > Felsic-volcanic > Dacite (Flow) Igneous > Volcanic > Mafic-volcanic > Andesite (Flow) Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic, tuff)Possibly only incidental in rank (estimated rank based proportion of rhyolite, regardless of form, being major). Igneous > Volcanic > Mafic-volcanic > Basalt (Volcaniclastic, volcanic breccia)Possibly only incidental in rank (estimated rank based on rank of basalt, regardless of form, being major). Incidental Metamorphic > Argillite Sedimentary > Clastic > Mudstone > Shale (Bed) Sedimentary > Clastic > Conglomerate (Bed)Tuffaceous and feldspathic. Sedimentary > Clastic > Sandstone (Bed)Tuffaceous and feldspathic. Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic, tuff) Igneous > Volcanic > Felsic-volcanic > Dacite (Volcaniclastic, volcanic breccia) Igneous > Volcanic > Mafic-volcanic > Andesite (Pyroclastic, tuff) Igneous > Volcanic > Mafic-volcanic > Andesite (Volcaniclastic, volcanic breccia) Igneous > Volcanic > Mafic-volcanic > Basalt (Pyroclastic, tuff)Possibly minor in rank (estimated rank based on rank of basalt, regardless of form, being major).
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. Luedke, Robert G., 1998, Maps showing distribution, composition, and age of Early and Middle Cenozoic volcanic centers in Oregon and Washington: U.S. Geological Survey Miscellaneous Investigations Series Map I-2291-D, scale 1:1,000,000. [http://pubs.er.usgs.gov/publication/i2291D] 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] 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. 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. [http://pubs.er.usgs.gov/publication/ofr88692]
Geographic coverage	King - Kittitas - Snohomish