STRATIGRAPHY AND PALEONTOLOGY OF THE UPPER TRIASSIC CHINLE FORMATION AT GLEN CANYON NATIONAL RECREATION AREA

The Upper Triassic Chinle Formation is widespread throughout western North America, with deposits located in the states of Utah, Colorado, Arizona, New Mexico, and Nevada. The Chinle Formation is a terrestrial, fluvial depositional sequence that preserves a biotic environmental record throughout the Late Triassic period. Strata of the formation are composed of clastic mudstone, sandstone, and conglomerate, with lesser lacustrine limestone. These sediments were deposited under alternating fluvial, lacustrine, and paludal conditions throughout the Late Triassic Period in western North America. The Chinle Formation also preserves a paleontological record of the Late Triassic period, including vertebrate and invertebrate remains, ichnofossils, and plant fossils. Researchers have studied the Chinle Formation extensively in National Parks of North America, including Zion National Park (Utah), Petrified Forest National Park (Arizona), and Canyonlands National Park (Utah). However, northern Arizona and southern Utah have been studied in lesser detail. Glen Canyon National Recreation Area (GLCA), which encompasses over a million acres of National Park Service administered land in northern Arizona and southern Utah, offers the unique opportunity to fill in the gap of knowledge for this region, and to correlate the stratigraphy of this formation throughout the extent of its deposition. As part of an effort to complete the Chinle Formation depositional model, two Geoscientists-In-The-Park are creating several detailed stratigraphic sections of the Chinle Formation in GLCA and correlating these sections with previous studies. The timing of the deposition of the Chinle Formation offers a unique opportunity to study faunal transitions during the early evolution of dinosaurs, as well as to study a developing fluvial depositional system in a continental basin devoid of marine input. Study of the Chinle Formation at GLCA will contribute to the stratigraphic model of the Upper Triassic Chinle Formation throughout the western United States, thus allowing for better understanding of changing depositional settings and floral and faunal communities of western North America during this time.