Interim Geologic Map of the West Part of - Utah Geological Survey

to be older, more likely of Bull Lake age; probably about 10 to 30 feet (3-10 m)thick.Qgtou Older glacial till and outwash, undivided (upper to middle? Pleistocene) –Similar to older glacial till of uncertain pre-Pinedale age, but forms broad, open,boulder-strewn and sage-brush-covered, eastward-sloping surfaces of the CastleCreek and Mammoth Creek areas; exposures just north of the junction of CrystalCreek and Mammoth Creek suggest that most of this surface is underlain by tillnow deeply incised at its eastern end; glacial outwash deposits, especially thosegraded to the Pinedale terminal moraines, are presumed to be present locally onthis till plain, but are not readily differentiated at this map scale; Mulvey andothers (1984) and Currey and others (1986) briefly reported on possible ice wedgepolygons as evidence for periglacial features on the southwest side of CastleValley; glacial till is as much as 60 feet (18 m) thick where exposed near theconfluence of Castle and Mammoth Creeks.Lacustrine and playa depositsQlg Coarse-grained lacustrine sediment (Holocene and upper Pleistocene) – Sandand gravel deposited at the east end of Navajo Lake, which formed behind a lavadam created by the Henrie Knolls lava flows; probably 10 to 15 feet (3-5 m) thick.QlpLittle Salt Lake playa deposits (Holocene) – Calcareous, saline, and gypsiferousgray clay, silt, and fine-grained sand deposited on the flat playa floor of Little SaltLake in the southwest part of Parowan Valley; locally includes small dunes ofeolian silt; playa formed in response to relative uplift of the Red Hills structuralblock (Threet, 1952; Maldonado and Williams, 1993a, b); the playa reflectsponded drainage and represents the latest stage in the history of antecedentdrainage through Parowan Gap; description modified from Maldonado andWilliams (1993b); we infer that a playa has occupied this area intermittentlythroughout the Pleistocene, but near-surface deposits are doubtless Holocene inage; at least 25 feet (8 m) thick.Qlm Little Salt Lake playa-margin deposits (Holocene and upper Pleistocene) –Calcareous, saline, and gypsiferous gray clay, silt, sand, and local volcanic andquartzite pebbles, deposited on gentle slopes around the margin of Little Salt Lakeplaya; periodically flooded during high lake levels; includes small alluvial fans,eolian sand and silt, and alluvium; less than 12 feet (4 m) thick.Mass-movement depositsQms, Qmsh, Qms?, Qms(Kd), Qms(Ti), Qms(Tql)Landslides (Historical? and upper? Pleistocene) − Very poorly sorted, locallyderived material deposited by rotational and translational movement; composed ofclay- to boulder-size debris as well as large, partly intact, bedrock blocks;characterized by hummocky topography, numerous internal scarps, chaoticbedding attitudes, and common small ponds, marshy depressions, and meadows;the largest landslide complexes involve tuffaceous strata of the Brian Head7