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

TKgc Grand Castle Formation, undivided (Paleocene? to Upper Cretaceous) – In itstype area of Parowan Canyon, divided into an upper light-gray and light-red,massive, cliff-forming conglomerate, a middle light-gray to white slope-formingsandstone, and a lower, cliff-forming, light-gray conglomerate that weathers toform hoodoos (commonly shaped like old-fashioned beehives [bee skeps]);undivided along the northwest flank of the Markagunt Plateau between Red Creekand Little Creek where the three members are too thin to map separately at thisscale; about 200 feet (60 m) thick.TKgcu Upper conglomerate of the Grand Castle Formation (Paleocene? to UpperCretaceous) – Light-gray and light-red, massive, cliff-forming conglomerate;clasts are well-rounded, pebble- to boulder-size quartzite, limestone, sandstone,and chert; like the lower conglomerate member (Kgcl), locally weathers to formhoodoos (commonly shaped like old-fashioned beehives [bee skeps]); uppercontact with strata here mapped as TKu on the Markagunt Plateau, and as basalred member of the Claron Formation in the Red Hills and northwesternMarkagunt Plateau, appears gradational; on the Markagunt Plateau south ofParowan, the upper contact corresponds to the base of ledge- and cliff-forming,tabular bedded sandstone stained dark-reddish-brown from overlying Claronstrata (figure 4); elsewhere, upper contact generally corresponds to the top of thecliff-forming conglomerate, above which is interbedded reddish-brown siltstone,sandstone, mudstone, and sandy limestone of the Claron Formation; deposited ina braided fluvial environment with paleoflow direction principally to the east tosouth-southeast, suggesting source areas in the Wah Wah, Blue Mountain, andIron Springs thrust sheets of southwest Utah (Goldstrand and Mullett, 1997); asmuch as about 200 feet (60 m) (Threet, 1952, 1963) to 300 feet (90 m)(Maldonado and Williams, 1993a) thick near Parowan Gap; on the MarkaguntPlateau, thins abruptly to the south from 183 feet (56 m) thick at the type area inFirst Left Hand Canyon southeast of Parowan (Goldstrand and Mullet, 1997) andthe conglomerate may locally be absent south of Navajo Ridge (where it was notrecognized in the measured sections of Goldstrand, 1991), but this interval istypically mantled in talus and colluvium that may obscure its presence; however,based on mapping of Upper Cretaceous strata between Parowan and CedarCanyons, we believe it is present at Sugarloaf Mountain, in the upper reaches ofSpring Creek Canyon, west of Blowhard Mountain, and west of Navajo Lakewhere it is no more than a few feet thick, and in Last Chance Canyon where it isabout 25 feet (8 m) thick; mapped as the conglomerate of Parowan Gap byMaldonado and Williams (1993a) but, following Goldstrand and Mullet (1997)inferred to be the upper conglomerate of the Grand Castle Formation because it isgradationally overlain by the red member of the Claron Formation and theunderlying middle Grand Castle sandstone is absent; a debris-flow deposit withinthe upper part of the unit in its type section yielded Late Cretaceous (Santonian?)pollen that Goldstrand and Mullett (1997) interpreted as recycled from olderstrata; however, Nichols (1997) reported Late Cretaceous (Santonian?) pollenfrom beds here mapped as TKu west and south of Blowhard Mountain, suggesting52