AN INVENTORY OF PALEONTOLOGICAL RESOURCES IN THE LOWER WAHWEAP FORMATION (LOWER CAMPANIAN), SOUTHERN KAIPAROWITS PLATEAU, GRAND STAIRCASE – ESCALANTE NATIONAL MONUMENT, UTAH

Most published research on the paleontological resources of the Wahweap Formation has focused on the results of wet screenwashing for microvertebrate remains and no attempt has been made to excavate larger vertebrate remains from the formation. From 2001 until the present, the Utah Geological Survey, with funding from the Bureau of Land Management, has been conducting a field inventory of all paleontological localities in the Wahweap Formation along the south side of its outcrop belt. The lower Wahweap Formation is readily accessible by road in this area and our survey focused on outcrops within one mile of these roads. In addition providing access for scientific research, the roads also facilitate the potential for illegal casual collection and vandalism. We observed evidence of vandalism consisting of a number of large trenches resulting from the theft of petrified logs. The results from this inventory using GIS will provide a baseline for the management of these fossil resources.

Plant localities are common and plant remains have been encountered whenever any significant excavations were conducted; we recorded 10 compressional plant sites and 63 petrified logs. Although invertebrate traces are abundant, freshwater shell beds (18 sites) are most abundant in the middle mudstone member. Large fossil crab (hermit crabs?) claws are characteristic of most mollusk and some vertebrate sites. We recorded a total of 310 vertebrate sites. Microvertebrate accumulations are abundant (93 sites) as sandstone channel lags commonly preserving abraded bones, isolated bones, and teeth. We found only a few microvertebrate sites in mudstones, where delicate jaws and other significant fossils may be recovered by screen washing. Channel lags also preserve isolated turtles and large dinosaur remains such as ceratopsian skulls, a pachycephalosaur dome, and a hadrosaurine jugal. Large bones from mudstones are typically isolated and only a few significant bonebeds were recognized in either mudstone or sandstone. We also recorded 13 dinosaur track sites. We attribute the absence of articulated skeletal remains to a lack of overbank deposits in the Wahweap Formation.