Abstract U-Pb dating of detrital zircons in fluvial sandstones provides a method for reconstruction of drainage basin and sediment routing systems for ancient sedimentary basins. This paper summarizes a detrital-zircon record of Cenomanian paleodrainage and sediment routing for the Gulf of Mexico and U.S. midcontinent. Detrital zircon data from Cenomanian fluvial deposits of the Gulf of Mexico coastal plain (Tuscaloosa and Woodbine formations), the Central Plains (Dakota Group), and the Colorado Front Range (Dakota Formation) show the Appalachian-Ouachita orogen represented a continental divide between south-draining rivers that delivered sediment to the Gulf of Mexico, and west- and north-draining rivers that delivered sediment to the eastern margins of the Western Interior seaway. Moreover, Cenomanian fluvial deposits of the present-day Colorado Front Range were derived from the Western Cordillera, flowed generally west to east, and discharged to the western margin of the seaway. Western Cordillera-derived fluvial systems are distinctive because of the presence of Mesozoic-age zircons from the Cordilleran magmatic arc: the lack of arc zircons in Cenomanian fluvial deposits that dis-charged to the Gulf of Mexico indicates no connection to the Western Cordillera. Detrital zircon data facilitate reconstruction of contributing drainage area and sediment routing. From these data, the dominant system for the Cenomanian Gulf of Mexico was an ancestral Tennessee River (Tuscaloosa Formation), which flowed axially through the Appalachians, had an estimated channel length of 1200-1600 km, and discharged sediment to the east-central Gulf of Mexico. Smaller rivers drained the Ouachita Mountains of Arkansas and Oklahoma (Woodbine Formation), had length scales of <300 km, and entered the Gulf through the East Texas Basin. From empirical scaling relationships between drainage-basin length and the length of basin-floor fans, these results predict significant basin-floor fans related to the paleo-Tennessee River system and very small fans from the east Texas fluvial systems. This predictive model is consistent with mapped deep-water systems, as the largest fan system was derived from rivers that entered the Gulf of Mexico through the southern Mississippi embayment.

Abstract The Cretaceous Western Interior Seaway experienced several transgressive/regressive cycles during its existence. The Greenhorn Cyclothem, the sixth such cycle, is significant because of the symmetry of deposition, and because of the expression of cyclical climatically influenced deposits within. This field trip will illustrate evidence of both of these cycles.

Abstract Digital photography is an important tool to depict geologic features at all scales. Roxborough State Park offers an excellent laboratory to practice the skills and art of geo-photography. Three regionally significant Paleozoic through Early Cretaceous sedimentary formations (Fountain Formation, Lyons Formation, and Dakota Sandstone) offer important textural details, outcrop patterns, and structural relationships that provide photographic challenges and opportunities. In photographing these features, basic principles of composition apply, including the rule of thirds and the use of leading lines, foreground, and depth of field. To engage these, geo-photographers need to use important in-camera tools that include aperture, shutter speed and appropriate ISO (an adopted standard from the International Standardization Organization), as well as a tripod, and suitable lens focal length. Choice of file format (RAW or jpg) has important consequences for final image quality. Post-processing is essential to ensure that images accurately depict the features intended, and may include adjustment of levels, color temperature, and sharpening. GigaPan images offer an additional tool for examining geologic features at multiple scales using up to several hundred stitched images. Photographs are an important venue for communicating geologic information to both professionals and the general public, and the more the compelling the images, the more effective the communication will be.

Abstract The Kaiparowits Basin, located mostly within Grand Staircase–Escalante National Monument, preserves an outstanding record of Late Cretaceous sedimentation in a foreland basin setting. Hosted in these rocks is one of the most continuous and complete records of this period’s ecosystems known from any one geographic area in the world. Recent work in the basin has emphasized macrovertebrate remains and documented many new sites of high scientific value. Recent stratigraphic studies have further refined our knowledge of the depositional systems and chronostratigraphic relationships. Provided is an overview of some of these recent advances, along with the necessary background to provide context .