WAVP - 2009

Petrified Forest National Park had the honor of hosting (along with Northland Pioneer College) the annual meeting of the Western Association of Vertebrate Paleontologists (WAVP) last weekend. For those of you who do not know about WAVP, it is essentially an unchartered group of paleontologists mainly from the western U.S. who meet yearly in February. The format is informal and it is a great forum for students to get experience presenting their research (indeed this is why the annual meeting was established). I gave my first talk at a WAVP meeting years ago.

This year we had over 60 attendees from a variety of institutions and 21 presentations (19 talks, 2 posters) ranging from Devonian to Pleistocene. We also had two field trips, one to some fossil localities at Petrified Forest National Park (which required some slogging through the mud due to a winter storm earlier in the week) and a later trip to the Cretaceous Moreno Hills Formation in the Zuni Basin of New Mexico (holotype locality of the dinosaurs Nothronychus and Zuniceratops).

Because it was held in the park we had a larger than usual Triassic contingent. Bill Mueller and Gretchen Gurtler (Texas Tech University) presented posters on the fauna of the Upper Triassic Dockum Group, focusing on basal phytosaurs. Max Langer (Universidade de São Paulo, Brazil), who was in the park doing research on early dinosaurs, gave a presentation on the Triassic faunal sequences in Brazil. Axel Hungerbuehler (Mesalands Community College) and students provided an update of new finds from the Redonda Formation of the Dockum Group. Jeff Martz and I presented the preliminary results of our recent stratigraphic and biostratigraphic revisions of the Chinle Formation at the Petrified Forest. Jeff has discussed this work in some detail at his blog Paleo Errata, and I am providing our WAVP meeting abstract below.

The WAVP meeting was a great time to catch up with a lot of friends and colleagues and check out some new research on a variety of vertebrate groups and time periods. At SVP meetings concurrent sessions and just the general busy atmosphere usually precludes me from seeing presentations outside of Mesozoic archosaurs, so these smaller meetings are very interesting. The location of next year's meeting is not established but hey that is WAVP. You can also read more about this years meeting here.

Revisions to the Lithostratigraphy and Vertebrate Biostratigraphy of the Chinle Formation (Upper Triassic) of Petrified Forest National Park

Jeffrey W. Martz and William G. Parker, Petrified Forest National Park, Petrified Forest, AZ, USA.

THE GEOLOGY and paleontology of the Upper Triassic Chinle Formation in Petrified Forest National Park and the surrounding region of northern Arizona has been extensively studied for over a century. Over this period, the broad lithostratigraphic framework of the park was generally agreed upon by most workers, and extensive vertebrate remains were collected and described. These studies led to the landmark 1985 study by Rob Long and Karen Ballew, which made critical contributions to phytosaur and aetosaur taxonomy, and recognized an important faunal turnover occurring at about the level of the Sonsela sandstone bed, between what were later called the “Adamanian and Revueltian land vertebrate faunachrons.” Further advances have been made in recent years to improve the stratigraphic resolution of this faunal transition, and to clarify the systematics of Upper Triassic vertebrate taxa.

Lithostratigraphic revisions made in recent years by some workers have identified a package in the middle of the Chinle Formation dominated by sandstone with lesser interbedded conglomerate and mudstone, which has been named the Sonsela Member. This recent work has also presented a novel correlation between two of the most prominent sandstone units within this member: the traditional Sonsela sandstone bed (here called the Jasper Forest Bed) and Flattops sandstone number one. The correlation of these two units has had important ramifications for vertebrate biostratigraphy and biochronology by resulting in an apparent overlap in the ranges of the taxa defining and characterizing the Adamanian and Revueltian.

Over the past year, the careful walking out of contacts between various lithologic bodies has falsified the recent revisions, and re-established the stratigraphic separation between the Sonsela sandstone bed and Flattops sandstone number one, as well as supporting the stratigraphic equivalence of the Jasper Forest Bed and Rainbow Forest Bed. This eliminates the apparent overlap between the faunas of the Adamanian and Revueltian. Moreover, our work establishing the precise stratigraphic position of both old and new fossil localities within this lithostratigraphic framework has allowed plotting the biostratigraphic ranges of taxa with a greater degree of precision than previously known, and allows precise stratigraphic placement of the Adamanian-Revueltian boundary. The available biostratigraphic information indicates that this faunal transition occurs just above the Jasper Forest Bed, during important shifts in the depositional pattern of the Chinle Formation.