As my longtime readers know one of my favorite aspects of paleontological research is redocumenting historic localities. It is important to exactly relocate these sites in order to place them in our modern stratigraphic framework, thus the fossils collected from these sites add more data to our local biostratigraphy. But I also just get the thrill of following in our predecessors footsteps, seeing the terrain as they saw it. It simply makes their data more relevant and in a way much more easier to understand when you take a walk in their shoes (or boots).
Last week it was off to the Blue Hills northeast of St. Johns, Arizona. In 1923 and 1924 Charles Camp of the UCMP made significant vertebrate fossil collections from these localities, including the type specimen of the phytosaur Machaeroprosopus zunii. The stratigraphic position of this specimen was in doubt because Camp had misinterpreted underlying Chinle Formation strata as belonging to the Moenkopi Formation. Jeff Martz and I had been interested in the stratigraphic position of this specimen for awhile so with old field notes and photos in hand, and with one of the main local landowners showing us the best way to access the badlands, we were on our way.
We were successful in relocating the M. zunii quarry almost immediately. The two photos directly below are one taken by Camp in 1923 of the M. zunii excavation (courtesy of the UCMP) and me at the same spot in 2010.
More difficult to find was Camp's "meal pots" locality, a greenish mudstone and fine sandstone horizon that produced numerous microvertebrates including plates of the diminuative aetosaur Acaenasuchus geoffreyi and some of the oldest recovered elements of the pseudosuchian Revueltosaurus. Camp's field notes were a little ambiguous regarding this site, but we were able to finally relocate it (see photo below).
Of course to round out our day, no trip to the Blue Hills would be complete without exploring "Calamites Hill", a site famous since the 1940s for producing upright specimens of Neocalamites (giant horsetails). The photo below is of a partially excavated specimen, and the ridge we were on contained numerous in-situ specimens.