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

and limestone; red quartzite clasts are common; ranges from less than one foot(0.3 m) to about 10 feet (3 m) thick.Except for thin conglomerate ledge at base, weathers to generally poorlyexposed slopes covered with debris from the overlying Dakota Formation; uppercontact is poorly exposed and corresponds to a color and lithologic change, fromcomparatively brightly colored smectitic mudstone below to gray and lightyellowish-brownmudstone and fine-grained sandstone above (figures 7 and 8);regionally, the Cedar Mountain Formation is unconformably overlain by theDakota Formation (see, for example, Kirkland and others, 1997); volcanic ashfrom correlative strata on the Kolob Plateau yielded a single-crystal 40 Ar/ 39 Ar ageof 97.9 + 0.5 Ma on sanidine (Biek and Hylland, 2007), and pollen analysesindicate an Albian or older age (Doelling and Davis, 1989; Hylland, 2010);Dyman and others (2002) obtained an 40 Ar/ 39 Ar age of 101.7 + 0.42 Ma (latestAlbian) on equivalent strata near Gunlock; additionally, palynomorphs from athin mudstone interval, including rare occurrences of Trilobosporites humilis andpossibly Pseudoceratium regium, collected immediately to the west in the CedarCity quadrangle (NW1/4 NW1/4 SE1/4 section 17, T. 36 S., R. 10 W.) suggest alate Albian age for this horizon (Michael D. Hylland, unpublished data,November 9, 2001); deposited in floodplain environment of a broad coastal plain(Tschudy and others, 1984; Kirkland and others, 1997; Cifelli and others 1997;Kirkland and Madsen, 2007); previously mapped as the lower part of the DakotaFormation, but the lithology, age, and stratigraphic position of these beds suggestcorrelation to the Cedar Mountain Formation (Biek and others, 2009);specifically, the mudstone interval appears to be time-correlative with theMussentuchit Member of the Cedar Mountain Formation of central and easternUtah; ongoing detrital zircon studies may help resolve the provenance andcorrelation of the underlying conglomeratic unit; about 60 feet (18 m) thick inCedar Canyon.61