Geology of the Poverty Bay quadrangle, Washington

Geologic Map of the Poverty Bay 7.5' quadrangle, King and Pierce counties, Washington

“…The Booth and others (2004b) version of the geology of the Poverty Bay 7.5' quadrangle relied heavily on mapping by Waldron (1961). Booth and Troost used map data from that earlier work with little modification in the southeastern part of the quadrangle, where excellent exposures once visible in the 1950s were largely overgrown.…”

“…The coastal and valley-wall bluffs of the Poverty Bay quadrangle locally display very good exposures of glacial and nonglacial deposits, but their interpretation has been enigmatic to geologists for 100 years (for example, Willis and Smith, 1899). The beach-cliff and valley-wall deposits in the map area were subdivided by Waldron (1961) into older glacial ("Salmon Springs" and "Stuck") units and an intervening nonglacial ("Puyallup") unit, by analogy to deposits described in detail by Crandell (1963) along the east wall of the Puyallup River valley about 12 mi (20 km) southeast of the quadrangle. Continued study over the last three decades, however, has suggested that the sequence of older sediments is more complex than originally recognized.…”

“…North of Peasley Canyon, exposures are largely restricted to small gullies, largely choked with landslides and other mass-wastage debris, that, although too small to show at map scale, nonetheless obscure stratigraphic relations. Southeast of Lake Fenwick, however, Waldron (1961) reported an outcrop displaying about 35 ft (10 m) of mudflow-alluvial complex beneath Vashon Drift, exposed in a small ravine; this complex (mapped here as unit Qpfn) consists of interbedded fine-to medium-grained volcanic sand, locally containing pumice fragments and clay lenses, and fine-grained slurry-like mudflows.…”

“…At the base of the Green River valley wall in the southeast corner of the quadrangle, a thin discontinuous band of older glacial deposits was mapped by Waldron (1961): north of Algona, Waldron defined it as an undifferentiated glacial deposit; south of Algona, he assigned it to his (oldest) "Stuck glaciation." Since 1961, most of these exposures have disappeared beneath slide debris and vegetation; what remains are isolated outcrops of sand, pebbly silt, and diamict of both glacial and nonglacial origin, including a valley-wall exposure of the 1 Ma Lake Tapps tephra of Crandell (1963) at Algona, identified by Westgate and others (1987).…”

Geology of the Renton, Auburn, and Black Diamond quadrangles, King County, Washington

“…2). Geologic maps have been published separately for several of the quadrangles: Buckley ; Poverty Bay, Des Moines, and Duwamish Head (Waldron, 1961(Waldron, ,1962(Waldron, ,1967; and Renton, Auburn, and Black Diamond (Mullineaux, 1965a, b, c). Final reports on the Lake Tapps 15-minute quadrangle (Crandell, 1963;Gard, 1968) include geologic maps of the Sumner, Buckley, Orting, and Wilkeson T^-minute quadrangles.…”