Miocene-Pliocene marine rocks (WAMIPO;0)

State	Washington
Name	Miocene-Pliocene marine rocks
Geologic age	Miocene-Pliocene
Original map label	MPL
Comments	Montesano Formation overlies Astoria Formation and not always differentiated from it in the literature. Most of the Montesano Formation, however, maps within this unit, and most of the Astoria in the WAM unit (based primarily on Logan, 1987a,b, and Walsh and others, 1987).
Primary rock type	sandstone
Secondary rock type	siltstone
Other rock types	conglomerate; mudstone
Lithologic constituents	Major Sedimentary > Clastic > Siltstone (Bed) Sedimentary > Clastic > Sandstone (Bed)Mostly lithofeldspathic and feldspatholithic but locally tuffaceous or feldspathic. Minor Sedimentary > Clastic > Conglomerate (Bed) Incidental Sedimentary > Clastic > Mudstone (Bed)
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. Walsh, T. J., Korosec, M. A., Phillips, W. M., Logan, R. T., Schasse, H. W., 1987, Geologic Map of Washington-Southwest Quadrant: Washington Division of Geology and Earth Resources, Geologic Map GM-34, scale 1:250,000. Rau, W. W., 1967, Geology of the Wynoochee Valley Quadrangle, Grays Harbor County, Washington: Washington Division of Mines and Geology Bulletin no. 56, 51 p. Logan, R. L., 1987a, Geologic Map of the South Half of the Shelton and South Half of the Copalis Beach Quadrangles, Washington: Washington Division of Geology and Earth Resources Open File Report 87-9, 16 p., 1 pl. Logan, R. L., 1987b, Geologic Map of the Chehalis River and Westport Quadrangles, Washington: Washington Division of Geology and Earth Resources Open File Report 87-8, 18 p., 1 pl.
Geographic coverage	Grays Harbor - Mason