Abstract

The United States Bureau of Reclamation commissioned the Utah Geological Survey to do a field survey for paleontological resources along the shoreline of Flaming Gorge Reservoir in northeastern Utah in spring 2002. During that work, Kirkland identified a sauropod trackway on a vertical sandstone cliff of the uppermost Stump Formation. Closer investigation of the strata revealed not only the undertracks of small adult sauropods, but of a juvenile as well. In addition, well-preserved sandstone casts of sauropod manus and pes prints were identified weathering out from softer overlying horizons. Approximately 2.6 m above the sandstone preserving the sauropod trackway is a fluvial, channel sandstone unit typical of the Salt Wash Member of the Morrison Formation. The sauropod trackway is in a “dino-turbated,” light gray, fine-grained, littoral sandstone unit. It is interbedded with reddish-gray to greenish-gray mudstone beds, similar to the paleosol and supratidal deposits of the uppermost Windy Hill Member of the Stump Formation or the Tidwell Member of the Morrison Formation. Approximately 4 m below the sauropod tracks, a series of thin-bedded, ripple-marked sandstone units are present preserving several pterosaur trackways and stratigraphically slightly lower, a small quadrapedal, quadradactyl trackway. These units overlie thin, variegated, red to green mudstone units. Similar pterosaur trackways are present at this stratigraphic level throughout much of Wyoming and Utah.