Paper No. 17-4
Presentation Time: 9:00 AM-6:30 PM
SEDIMENTOLOGY, STRATIGRAPHY, AND PETROGRAPHIC ANALYSIS OF THE CLARON FORMATION: IMPLICATION FOR EOCENE PALEOENVIRONMENTS ALONG THE SOUTHERN MARGIN OF AQUARIUS PLATEAU, UTAH
The Claron Formation is the cliff-forming unit responsible for the iconic scenery in Bryce Canyon National Park, Cedar Breaks National Monument, and much of the surrounding area of southwestern Utah. Along with the stunning scenery, the Claron Formation also holds information regarding the geologic evolution of the Colorado Plateau; however, surprisingly little is known about its depositional history. The Claron Formation in the Sweetwater Creek area of the Aquarius Plateau is cliff forming, with alternating layers of siltstone, sandstone, and limestone. The Sweetwater Creek section was chosen because of its excellent exposures, frequent occurrence of fossils and unusual lithologies. The underlying Paleocene Pine Hollow Formation consists of deep purple mudstones with interbedded fining upwards sequences of green-gray cobble conglomerates with Jurassic sandstone clasts. The base of the Eocene Claron Formation is defined by the first appearance of a tan-white siltstone that is overlain by interbedded limestones and orange quartz-rich sandstones with either a clay or calcite rich matrix. The sandstone units are dominantly ridge formers that display channels features, vague cross stratification, and abundant bioturbation. Sandstone beds locally fine upward into siltstones which vary from well-cemented to friable. Petrographic analysis indicates that the majority of the sandstones are quartz arenites with calcite cement. Sandstone variation arises from the amount of cement/matrix with the Pine Hollow Formation displaying a lack of both clay and cement; however that could be a digenetic feature. The Sweetwater Creek area contains calcite cement in the lower part of the section and more clay matrix in the uppermost samples. The sandstones in the Sweetwater Creek section revealed an abundance of monocrystalline quartz, polycrystalline quartz and black chert with occasional radiolarians present in carbonates. Carbonate inclusions were within both chert and quartz clast and calcite crystals were abundant around quartz crystals within the cement. Preliminary stratigraphic analysis indicates that the southern margin of the Claron Formation was deposited in an alternating fluvial and lacustrine environment.