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

dark-yellowish-orange, grayish-pink, and similarly hued sandy and micriticlimestone, calcite-cemented sandstone, calcareous mudstone, and minor pebblyconglomerate that weathers to colluvium-covered slopes. Limestone is poorlybedded, microcrystalline, generally sandy with 2 to 20% fine-grained quartz sand,and is locally argillaceous; contains common calcite veinlets, calcite spar-filledvugs, calcite spar- and micrite-filled burrows, and stylolites; also contains sparsesmall bivalves and planispiral gastropods; many of these limestone beds may becalcic paleosols (Mullett and others, 1988a, b; Mullett, 1989; Mullett and Wells,1990). Sandstone is thick-bedded, fine- to coarse-grained, calcareous, locallycross-bedded quartz arenite that typically weathers to sculpted or fluted ledgesthat pinch out laterally; sandstone locally contains pebble stringers. Mudstone isgenerally moderate reddish orange, silty, calcareous, contains calcareous nodules,and weathers to earthy, steep slopes between ledges of sandstone and limestone.Pebbly conglomerate forms lenticular beds 5 to 15 feet (2-5 m) thick withrounded quartzite, limestone, and chert pebbles, cobbles, and, locally, smallboulders; conglomerate is uncommon on the Markagunt Plateau south of ParowanCanyon, but lower red member strata are abundantly conglomeratic in the RedHills and at the northwest edge of the Markagunt Plateau north of Parowan; atSugarloaf Mountain west of Brian Head, several tens of feet of conglomerate (orseveral thinner beds within this interval) overlie the basal Claron limestone.Upper, conformable contact corresponds to a pronounced color and lithologicchange from brightly colored reddish-orange mudstone and siltstone below to awhite to very pale orange micritic limestone above; mostly nonfossiliferous andits age is poorly constrained as Eocene to Paleocene(?) (Goldstrand, 1994), butNichols (1997) reported Late Cretaceous (Santonian?) pollen from gradationallyunderlying strata here mapped as TKu south and west of Blowhard Mountain,thus suggesting that the Claron Formation may be older than previously thought;measurements from the map suggest that the red member is about 1000 feet (300m) thick at Cedar Breaks National Monument, similar to the measured thicknessof Schneider (1967), who reported that the red member there was 993 feet (303m) thick (the lower 56 feet [17 m] of his section includes beds we assign to TKu,thus the red member there is 937 feet [286 m] thick), considerably less than the1300 feet (400 m) reported in Sable and Maldonado (1997b); strata that weinclude in the red member are likely of similar thickness in more structurallycomplicated outcrops of the Red Hills (Threet, 1952, 1963).TERTIARY-CRETACEOUSTKu Tertiary-Cretaceous strata, undivided (Paleocene? to Upper Cretaceous?) –Yellowish-brown, commonly stained dark-reddish-brown, fine-grained sandstoneand lesser interbedded, similarly colored mudstone and siltstone; bedding is thinto very thick and appears tabular from a distance; weathers to ledgy slope or cliff;outcrop habit and surficial color make it look like the red member of the ClaronFormation from a distance (figure 4); not yet mapped in Parowan Canyon andareas to the north, where basal Claron strata are conglomeratic and identificationof this interval, if present, is problematic; upper contact placed at the base of thefirst sandy limestone bed (calcic paleosol) of the red member of the Claron50