New Mexico Geological Society Annual Spring Meeting — Abstracts

At Clayton Lake in Union County, northeastern New Mexico, an extensive dinosaur tracksite is exposed in the dam spillway. Tracks are present at four stratigraphic levels across the contact of the Lower Cretaceous (upper Albian) Mesa Rica and Pajarito formations. The main track level is on the top sandstone bedding surface of the Mesa Rica Formation. Previous studies have counted 260 to as many as 500 dinosaur tracks at this level that are mostly of ornithopods (Caririchnium), but that also include two kinds of theropod tracks (Magnoavipes, cf. Irenesauripus) and a single quadrupedal trackway of an ankylosaur? (Deltapodus). The associated invertebrate ichnoassemblage is shallow burrows assigned to Arenicolites, Planolites, Taenidium and Thalassinoides, representative of the Scoyenia ichnofacies. The paleoenvironment of the tracksite is broadly interpreted as a sandflat at or very near the shoreline of the Western Interior seaway. Paleontological study of the Clayton Lake tracksite began in 1982, and Gillette and Thomas (1985) published a map of the tracks. This, the only published map of the tracks, was made by standard grid, tape and compass techniques, and identified nearly 500 dinosaur tracks at the site, mostly of ornithopods. Subsequent studies focused on some individual tracks, detailed the statigraphy and geological age of the tracksite or presented short summaries of the tracksite (e. g., Lucas et al., 1986; Gillette and Thomas, 1989; Bennett, 1992; Hunt and Lucas, 1998). Lucas and Dalman (2016) restudied the tracksite without cleaning it, so it was not mapped. They counted 260 dinosaur tracks at the site. Traditional photography, under low angle natural light, was used by Lucas and Dalman to document individual tracks, and some trackways were traced on acetate film to produce trackway maps. Our photogrammetric study in 2019 yields extensive data with which to more accurately interpret the geology and ichnology of the tracksite than was possible by previous studies using traditional field methods.

References

Bennett, S.C., 1992, Reinterpretation of problematic tracks at Clayton Lake State Park, New Mexico: Not one pterosaur, but several crocodiles: Ichnos, v. 2, p. 37-42.

Gillette, D.D. and Thomas, D.A., 1985, Dinosaur tracks in the Dakota Formation (Aptian- Albian) at Clayton Lake State Park, Union County, New Mexico: New Mexico Geological Society, Guidebook 36, p. 283-288.

Gillette, D.D. and Thomas, D.A., 1989, Problematical tracks and traces of late Albian (Early Cretaceous) age, Clayton Lake State Park, New Mexico, USA; in Gillette, D. D. and Lockley, M. G., eds., Dinosaur tracks and traces: Cambridge, Cambridge University Press, p. 337-342.

Hunt, A.P. and Lucas, S.G., 1998, Tetrapod ichnofaunas from the Lower Cretaceous of northeastern New Mexico, USA: New Mexico Museum of Natural History and Science, Bulletin 14, p. 163-167.

Lucas, S. G. and Dalman, S. G., 2016, The early Cretaceous Clayton Lake dinosaur tracksite, northeastern New Mexico: New Mexico Museum of Natural history and Science, Bulletin 74, p. 127-140.

Lucas, S.G., Hunt, A.P., Kietzke, K.K., and Wolberg, D.L., 1986, Cretaceous stratigraphy and biostratigraphy, Clayton Lake State Park, Union County, New Mexico: New Mexico Geology, v. 8, p. 60-64.