Older glacial drift

Till, outwash, and associated interglacial deposits; sorted and unsorted gravel, sand, silt, and clay. Includes peat beds and non-glacial sediments locally. Mostly pre-Wisconsin in age.
State Washington
Name Older glacial drift
Geologic age Pleistocene
Lithologic constituents
Unconsolidated > Fine-detrital (Glacial-till, Glacial-outwash)clay and silt
Unconsolidated > Coarse-detrital (Glacial-till, Glacial-outwash)gravel and sand
Unconsolidated > Peat
Comments Peat beds and non-glacial sediments are represented by Puyallup Sand/Formation, possibly by the Alderton Formation which is known only in the southern Puget Lowland (Easterbrook, 1986). This unit is difficult to distinguish from Qg1 by lithology; distinction is in age difference only. Some stratigraphic units may occur in both units, regardless of age. The Stuck Drift, Double Bluff Drift, and Alderton Formation (question marked) are tenatively included in this unit because they are pre-Wisconsin and because they have been mapped with other stratigraphic units in this unit. In general, these deposits are rare relative to younger deposits (see WAQg1, WAQg1o, WAQg1t, and WAQg) because most of the sediment was eroded or buried by subsequent glacial advances.
Stratigraphic units Admiralty clay, drift, till; Orting gravel/Drift; Puyallup Sand/Formation; Whidbey Formation; Possession Drift (in part); Stuck drift? Double Bluff Drift? Alderton Formation?

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.

Easterbrook, D.J., 1976a, Quaternary Geology of the Pacific Northwest, in Mahaney, W.C., ed., Quaternary Stratigraphy of North America: Stroudsberg, PA, Dowden, Hutchinson and Ross, p. 441-462.

Easterbrook, D.J., 1986, Stratigraphy and chronology of Quaternary deposits of the Puget Lowland and Olympic Mountains of Washington and the Cascade Mountains of Washington and Oregon: Quaternary Science Reviews, v. 5, p. 145-159.

Jones, M.A., 1999, Geologic Framework for the Puget Sound Aquifer System, Washington and British Columbia: U. S. Geological Survey Professional Paper 1424-C, 31 p., 18 pls.

NGMDB product
Counties Clallam - King - Kitsap - Mason - Pierce - Snohomish - Spokane - Stevens - Thurston - Whitman