5 Council on Undergraduate Research—Undergraduate Research (Posters)

Monday, 23 May 2005
8:00 AM - 4:00 PM

A NEW EARLY JURASSIC (HETTANGIAN) DINOSAUR TRACK-BEARING HORIZON FROM THE MOENAVE FORMATION, ST. GEORGE DINOSAUR DISCOVERY SITE AT JOHNSON FARM, WASHINGTON COUNTY, UTAH

Paper number: 5-1
Program: THEME SESSIONS
Time: 8:00 AM – 4:00 PM

Authors

Abstract

Abundant dinosaur bones are being collected in close association with dinosaur tracks and traces from the lacustrine Whitmore Point Member of the Early Jurassic Moenave Formation within St. George, Utah city limits. This abundant dinosaur fauna that displays a diverse array of dinosaur behaviors is preserved in mudflats and beaches surrounding ancient Lake Dixie, an oasis during deposition of the Wingate erg to the northeast. The dinosaur traces occur in a laterally extensive one foot thick fine-grained sandstone bed near ancient Lake Dixie. The unit is approximately 63 meters above the base of the Moenave Formation and has yielded more than 250 in situ theropod dinosaur tracks to date. Grallator tracks dominates, with only a single Eubrontes track recorded thus far. The tracked layer is mudcracked, heavily bioturbated by invertebrates, and contains isolated fish scales and bone fragments.

Track orientations dominantly trend southwest to southeast on this surface. Several areas of this tracked surface are heavily trampled and individual tracks are sometimes difficult to distinguish. This track-bearing layer represents a lacustrine regression where theropods were moving to and from the shoreline across a wide mudflat. This mudflat appears to be located to the south of ancient Lake Dixie.