Lower Tertiary volcanic rocks, undivided (WAlTv;0)

State	Washington
Name	Lower Tertiary volcanic rocks, undivided
Geologic age	Eocene
Lithologic constituents	Major Igneous > Volcanic > Mafic-volcanic > Basalt (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia) Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow, Pyroclastic-tuff) Minor Igneous > Volcanic > Mafic-volcanic > Andesite (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia) Igneous > Volcanic > Felsic-volcanic > Dacite (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia) Incidental Sedimentary > Clastic > Conglomerate (Bed, Tuffaceous)Tuffaceous and feldspathic. Sedimentary > Clastic > Mudstone > Shale (Bed) Sedimentary > Clastic > Sandstone (Bed, Tuffaceous)Tuffaceous and feldspathic. Metamorphic > Metasedimentary > Metaclastic > Argillite
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).
Stratigraphic units	Barlow Pass volcanics; Swauk Formation (in part: Silver Pass volcanics); Naches Formation (in part, including Mt. Catherine rhyolite);
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. 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. https://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. 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.
NGMDB product	NGMDB product page for 30777
Counties	King - Kittitas - Snohomish

State

Washington

Name

Lower Tertiary volcanic rocks, undivided

Geologic age

Eocene

Lithologic constituents

Major

Igneous > Volcanic > Mafic-volcanic > Basalt (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)

Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow, Pyroclastic-tuff)

Minor

Igneous > Volcanic > Mafic-volcanic > Andesite (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)

Igneous > Volcanic > Felsic-volcanic > Dacite (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)

Incidental

Sedimentary > Clastic > Conglomerate (Bed, Tuffaceous)Tuffaceous and feldspathic.

Sedimentary > Clastic > Mudstone > Shale (Bed)

Sedimentary > Clastic > Sandstone (Bed, Tuffaceous)Tuffaceous and feldspathic.

Metamorphic > Metasedimentary > Metaclastic > Argillite

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).

Stratigraphic units

Barlow Pass volcanics; Swauk Formation (in part: Silver Pass volcanics); Naches Formation (in part, including Mt. Catherine rhyolite);

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.

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.

https://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.

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.

NGMDB product

NGMDB product page for 30777

Counties

King - Kittitas - Snohomish