BARBECUED DINOSAUR BONES: TRACES OF A PALEOWILDFIRE NEAR THE END OF THE CRETACEOUS

Paleowildfire deposits are identified in the Upper Cretaceous of Central Wyoming. The fire resulted in a catastrophic assemblage of both plant and vertebrate material. Reconnaissance studies result in identification of a thin stratigraphic interval occurring over a faulted geographic area of central Wyoming, in the Bighorn Basin. Paleowildfires occur during predictable climatic conditions within recognizable ecological requirements.

Burned bone occurs within a lithologically constrained interval of weakly indurated, paleowildfire influenced siliciclastic units. Taphonomically, there are at least three types of preservation identified during initial reconnaissance: 1) burned bone in association with burned tree stumps and ash in illite containing silty sandstone; 2) burned bone associated with ferruginous crusts in lithic sandstone; 3) burned bone contained in laminated, silty mudballs. Skeletal material varies in size from a few millimeters to tens of centimeters. Frequency of bone occurrence in the ash layer suggests that there could be a larger accumulation of bone than that evaluated during initial reconnaissance as spatial density of bone over geographic area is relatively high. Identification of a North American Upper Cretaceous "barbecued interval" provides a rare window of opportunity to study trophic relationships and the type of vegetation that was growing at the time, as well as potential climatic conditions. Increasing identification of paleowildfires provides a unique window in to the climatic condition of the past and raises the question as to the frequency of wildfires occurring during the Upper Cretaceous as well as other geologic times.