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Geologic units containing olistostrome

Rhode Island

Newport Group - Fort Adams Formation (Late Proterozoic? or older?)

Newport Group - Fort Adams Formation - Large clasts of dolostone and quartz arenite (olistoliths) enclosed within a matrix of tuff, siltstone, slate, and conglomerate; interpreted as an olistostrome.

Washington

Lower upper Eocene marine and nonmarine rocks (Eocene)

Predominantly massive to well-bedded tuffaceous marine siltstone with interbedded arkosic and basaltic sandstone. Includes conglomerate in King County and along north side of Olympic Peninsula. Minor lava flows and breccia in western Lewis County and eastern Grays Harbor County. Coal seams in central Lewis County and north-central Pierce County.

Oligocene-Miocene marine rocks (Oligocene)

Massive to thin-bedded, coarse-grained sandstone, conglomerate, conglomeratic sandstone, shale, and sandy shale.

Upper upper Eocene nonmarine and marine rocks (Middle Eocene)

Massive to thin-bedded, feldspathic to arkosic sandstone, siltstone, shale, and carbonaceous shale; becomes mostly marine in the western foothills of Cascade Mountains where coal beds are abundant. Basaltic sandstone and siltstone in northern Olympic Peninsula.