CHARACTERIZING AN INCISED VALLEY FILL IN THE ABERDEEN MEMBER, UPPER CRETACEOUS BLACKHAWK FORMATION, BOOK CLIFFS, UTAH
Measured sections taken at 8 locations in a west-east transect along the depositional dip of the valley, along with drone imagery taken of inaccessible cliff exposures, and LiDAR images from measured section localities, were used to characterize the transition between fluvially dominated strata updip, and tidally dominated strata downdip. In the updip extent, the incised valley erodes through a 12ft (3.7m) coal seam, and is identified in coal isopach maps. In the most updip exposures, the valley fill consists of thin (0.35-1m), amalgamated channel-fill sandstones with lateral accretion, thin, discontinuous coal seams, and rooted overbank intervals. Tidal indicators are absent in the updip exposures. When traced slightly down-dip, exposures contain thicker fluvial sandstones up to 2m, characterized by an upward decrease cross-bed thickness. Many of these channel-fill sandstones are laterally discontinuous and separated vertically by overbank fines. Exposures down depositional dip are tidally dominated, often containing tidal flat facies between 3-5m thick. Tidal indicators include flaser, wavy and lenticular bedding, interference ripples, and sigmoidal cross-stratifiied sandstone with tidal bundling. LiDAR data was collected and compared with drone imagery and outcrop data (measured sections) to evaluate the efficacy of each data collection method.