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

(figure 3); best exposed near the North View overlook, where it is 109 feet (33 m)(Schneider, 1967) of mudstone and siltstone capped by a thin calcareoussandstone and pebbly conglomerate; this capping bed is 1 to 10 feet (0.3-3 m)thick and has chert, quartzite, and Claron limestone clasts but apparently novolcanic clasts; the sandstone and pebbly conglomerate are overlain by graybentonitic mudstone of the Brian Head Formation (Tbhv); also exposedimmediately south of Panguitch Lake, where it is about 50 feet (15 m) thick, andin the upper reaches of Rock Canyon, but is apparently absent elsewhere on theMarkagunt Plateau; queried near Winn Gap at the south end of the Red Hills,where, based on similar four-part limestone-clastic-limestone-clastic sectionabove the red member, we infer that the white member may be present; alsoqueried near Mineral Canyon northeast of Paragonah, where as much as a fewhundred feet of Claron redbeds lie above what may be the upper limestoneinterval.Schneider (1967) reported biotite in some of these beds, and while somebeds exhibit slightly expansive soils, we found no biotite – even so, it is theapparent presence of biotite-bearing strata, and possible correlation to variegatedstrata on the southern Sevier Plateau (see Feist and others, 1997), that led Sableand Maldonado (1997b) to provisionally include these strata as part of their BrianHead Formation. However, these same exposures strongly suggest to us that thenontuffaceous sandstone and conglomerate as defined by Sable and Maldonado(1997b) is simply the uppermost facies of the Claron Formation; they reasonedthat because Brian Head volcaniclastic strata overlie different parts of the ClaronFormation on the Markagunt Plateau, a disconformity separates the twoformations; although we agree that an unconformity exists, we place theunconformity at the base of the thin sandstone and conglomerate (not at the top ofthe limestone ledge of the white member), thereby including the Claron-like redbeds as a new upper unit of the white member. Sable and Maldonado (1997b) andFeist and others (1997) reported on sparse late to middle Eocene vertebrate fossilsand charophytes in strata on the southern Sevier Plateau that may be equivalent tothis map unit.47