COMPILING A DATABASE FOR OLD AND NEW MESOZOIC TRACKSITE DISCOVERIES FROM THE LAKE POWELL AREA (UTAH AND ARIZONA)

Vertebrate footprint sites are known from dozens of sites in the Glen Canyon National Recreation Area (GLCA) also known as Lake Powell. A preliminary, 1998 survey reported 36 Permian through Upper Jurassic sites, found by tourists, NPS employees and geologists before the widespread use of GPS systems. In the present study the site count has increased to more than 50, and the probability of ,many more discoveries in the vast GLCA area, and adjoining BLM and Navajo Nation lands, is very high.

Beginning in 2004 the National Park Service (NPS) funded a “rescue” survey aimed at compiling an updated GPS database for known sites, newly discovered and previously submerged sites. This objective has been aided by low water levels (more than 30 m below maximum) due to recent drought conditions.

New sites from the Lower Jurassic Glen Canyon Group include the Choal Canyon Sites in the Kayenta-Navajo transition zone with parallel trackways of theropods with metatarsal impressions, and a Eubrontes trackway indicating an estimated speed of about 22.4 km/hour. In the Slick Rock Canyon area, a high density of tracksites in this transition zone includes four mapped sites with a total of 150 tracks of Anomoepus, Grallator and Eubrontes.

Other important discoveries include an Otozoum trackway progressing up a dune foreset in the Navajo Formation, and theropod tracks, now assigned to the Entrada Formation, that were previously incorrectly assigned to the Navajo Formation.