New Mexico Geological Society Annual Spring Meeting — Abstracts

The Peterson site NMMNH locality 3282 is the most extensive Jurassic dinosaur locality yet discovered in New Mexico. Located in Bernalillo County near Canoncito, it is a mass burial assemblage of dinosaur bones in the Brushy Basin Member of the Morrison Formation. The bone-bearing horizon at the site is a 1.1-to 3-m-trlick, trough-cross bedded sandstone approximately 25 m below the base of the Jackpile Member of the Morrison Formation. Discovered in 1963, the site has been regularly excavated since 1989, and has yielded more than 100 dinosaur bones, but is far from completely excavated. Dinosaur taxa from the site include a large allosaurid theropod, a diplodocid sauropod and other(?) sauropods.

The dinosaur bones at the Peterson site are mostly disarticulated and partially articulated limb bones, vertebrae and ribs with a general NW-SE alignment that parallels the paleocurrent as indicated by SE-dipping trough crossbed axes. This provides strong prima facie evidence of fluvial transport and hydraulic concentration of the bones. However, clay balls associated with the bones, the large size of the bones and their evident lack of abrasion suggest that transport distances were relatively short. Some bones at the site are tilted on bedding planes with a dip of about 8 degrees down to the NW, suggesting they may have been mired on a bar or levee margin.

The Peterson site thus is a fluvially transported and winnowed lag deposit of large dinosaur bones, mostly of sauropods. It thereby resembles taphonomically most of the large dinosaur bone quarries known from the Morrison Formation in the western United States. The Peterson site also supports recognition that deposition of the Brushy Basin Member took place on I riverine floodplains, not in a large, shallow lake.