One of the keynote speakers at the 2006 Creation Biology Study Group conference was Dr Art Chadwick of Southwestern Adventist University, Keene, Texas. He gave a fascinating talk about his ground-breaking work at the Hanson Ranch in eastern Wyoming which is shedding new light on how a rich bed of dinosaur bones was deposited.
The bone bed, which is part of the Upper Cretaceous Lance Formation (Spencer et al. 2001), has yielded large numbers of the crestless hadrosaur, Edmontosaurus, along with the remains of several other dinosaurs. In addition, the bed contains freshwater and brackish-water invertebrates and marine acritarchs and dinoflagellates (Chadwick 2006). The bone-rich layer covers an area of more than one square kilometre, although most of the bones are concentrated in an area of about 40 hectares (Chadwick et al. 2006). Based on the number of bones recovered from the site’s two main quarries and six test quarries, it is estimated that between 10,000 and 25,000 animals are interred in the bone bed (Chadwick et al. 2006).
High precision surveys using GPS and GIS technology have enabled Art and his colleagues to accurately reconstruct the position and distribution of the dinosaur bones in three dimensions (Chadwick et al. 2005). The bones are disarticulated or, more rarely, partially articulated and display little evidence of weathering or abrasion. They occur in a poorly consolidated claystone or mudstone, and are normally graded with the large limb bones at the base and the vertebrae and toe bones towards the top. Overlying the bone bed is a cross-bedded, glauconite-bearing sandstone that gives evidence of rapid deposition.
We can appreciate the significance of these discoveries when we consider the standard model for the origin of bone beds. Bone beds are typically thought to represent the episodic accumulation of carcasses in fluvial environments over a long period of time. However, based on the evidence gathered at the Hanson Ranch, Art and his colleagues favour the hypothesis of a catastrophic mass mortality event (Chadwick et al. 2006). They propose that a large number of hadrosaurs (probably more than a single herd) were catastrophically killed and that their remains then rotted for a time in a swampy, freshwater environment. Subsequently the bones were picked up by a catastrophic mudflow and transported into a deep water marine environment, where they were deposited as a graded bed.
Obviously this research is of great interest to those of us who favour catastrophist interpretations of the geological record, consistent with the global flood recorded in Scripture. You can read more on the Dinosaur Project website and there are even opportunities for participation in the dinosaur dig.
Chadwick A. V., Spencer L. A. and Turner L. E. 2005. Taphonomic windows into an Upper Cretaceous Edmontosaurus bonebed. Geological Society of America Abstracts with Programs 37(7):159.
Chadwick A., Spencer L., Turner L. 2006. Preliminary depositional model for an Upper Cretaceous Edmontosaurus bonebed. Journal of Vertebrate Paleontology 26:49A.
Chadwick A. V. 2006. What happened to the dinosaurs? Occasional Papers of the BSG 8:8-9.
Spencer L., Turner L. E. and Chadwick A. V. 2001. A remarkable vertebrate assemblage from the Lance Formation, Niobrara County, Wyoming. Geological Society of America Abstracts with Programs 33:A499.