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

Eolian depositsQed Eolian dune sand (Holocene) − Grayish-pink to pale-red, well-sorted silt andfine-grained sand largely stabilized by vegetation; most of the sand consists oftiny clay pellets eroded from the Claron Formation and carried eastward by strongwinds and updrafts where it was deposited in the lee of the Cedar Breaksescarpment; typically less than 15 feet (5 m) thick.QesEolian sand (Holocene) − Yellowish-brown to reddish-brown, moderately wellsorted sand and silt derived from deflation of Little Salt Lake playa depositslocated to the south and west; forms thin sheets and poorly developed dunespartly covered by sparse vegetation; generally more saline than underlyingalluvium and so allows greasewood to flourish at the expense of sagebrush;description modified from Maldonado and Williams (1993b); typically less than 6feet (2 m) thick.Glacial depositsGlacial till and outwash are present east of Brian Head peak in the Castle Creek andLowder Creek drainages and in the greater Castle Valley area. These deposits are of thePinedale alpine glacial advance and an older glaciation of unknown Quaternary age(possibly the Bull Lake alpine glacial advance). Pinedale deposits in their type area inthe Wind River Range of Wyoming are about 12 to 24 ka (Imbrie and others, 1984) (withglacial maxima about 16 to 23 ka based on cosmogenic 26 Al and 10 Be dating; Gosse andothers, 1995), and are roughly coeval with the late Wisconsin glaciation, Last GlacialMaximum (LGM), and marine oxygen isotope stage 2 (MIS 2). Early Wisconsin glacialmoraines (MIS 4, about 59 to 71 ka; Imbrie and others, 1984) are not known in Utah(Laabs and Carson, 2005). Deposits of the Bull Lake alpine glacial advance in their typearea in the Wind River Range of Wyoming are about 128 to 186 ka (Imbrie and others,1984) (with glacial maxima about 140 to 160 ka; Gosse and Phillips, 2001; Sharp andothers, 2003), and are roughly coeval with the Illinoian glaciation or MIS 6.Qgtp Glacial till of Pinedale age (upper Pleistocene) – Non-stratified, poorly sorted,sandy pebble to boulder gravel in a matrix of sand, silt, and minor clay; clasts arematrix supported, subangular to subrounded, and were derived from the LeachCanyon, Isom, and Brian Head Formations and the Markagunt megabrecciaexposed in the headwaters of the Castle Creek and Lowder Creek drainage basins;terminal moraine at the west end of Castle Valley is at an elevation of about 9750feet (2973 m), whereas the terminal moraine of the smaller Lowder Creek basin isat Long Flat at an elevation of about 10,100 feet (3080 m); recessional and lateralmoraines and hummocky, stagnant ice topography are locally well developed, butsculpted bedrock is absent or inconspicuous, probably owing to the relativelysmall size and suspected short duration of the glaciers (Mulvey and others, 1984);well-developed terminal and recessional moraines are as much as 120 feet (37 m)thick, but till is much thinner elsewhere and locally consists only of scatteredboulders or a veneer of meltout till on bedrock.The Brian Head-Sidney Peaks area marks the southernmost occurrence oflate Pleistocene glaciation in Utah (Mulvey and others, 1984), which was firstbriefly described by Gregory (1950); Agenbroad and others (1996) interpreted5