| State | Washington |
|---|---|
| Name | Tertiary dunite intrusive rocks |
| Geologic age | Late Cretaceous |
| Lithologic constituents |
Major
Igneous > Plutonic > Ultramafic > Peridotite > Dunite
Minor
Metamorphic > Metaigneous > Serpentinite
Incidental
Igneous > Plutonic > Ultramafic > Pyroxenite
|
| Comments | May be referred to no more specifically that as peridotite; may also be reported as harzburgite. Occurs as pods, lenses, and "tectonically emplaced bodies" (Dragovich and others, 2002); Twin Sisters Dunite is a "plate-like body" (Tabor and others, 1994). Pyroxenite occurs very rarely. |
| Stratigraphic units | Twin Sisters dunite |
| 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.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., Haugerud, R.A., Booth, D.B., Brown, E.H., 1994, Preliminary Geologic Map of the Mount Baker 30- by 60-Minute Quadrangle, Washington: U. S. Geological Survey Open File Report 94-403, 55p., 2 pls.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 | |
| Counties | Skagit - Snohomish - Whatcom |