Middle Cretaceous dinosaur tracks at Cerro de Cristo Rey, Sunland Park, New Mexico and a comparison with other paleocoastal tracksites of the southwestern US
Dinosaur tracksites at Cerro de Cristo Rey and in the surrounding Paso del Norte region warrant detailed study and comparison with other tracksites of similar age. Located in Sunland Park, Doña Ana County, New Mexico, El Paso, Texas, and Chihuahua, Mexico, the "Cristo Rey tracksite assemblage" is an important piece of paleoecological information for the mid-Cretaceous period (Albian-Cenomanian). ^ In the United States, the tracks are preserved at 8 localities in several sandstone units of the Middle Cretaceous Anapra Sandstone, also known as the Sarten Member of the Mojado Formation. This unit is exposed around a hypabyssal trachy-andesite intrusion, Cerro de Cristo Rey, and also along the Western Boundary Fault zone in the Franklin Mountains. Sarten sandstone beds are hematized and highly fractured in many areas, hence preservation and exposure of the tracks is quite variable. In Ciudad Juarez, Chihuahua, Mexico tracks are also preserved in the Sarten Member on the south side of the Cristo Rey uplift, and also in the Sierra de Juarez. Preservational styles of tracks vary greatly, including convex epi- and hyporelief, concave epirelief, in cross section, and as hematite staining (undertracks). ^ Track types identified are Caririchnium leonardii, Magnoavipes sp., Ankylosaur tracks, Hadrosaur-like Caririchnium sp., and swimming traces. Caririchnum sp. is the most common track type found. ^ The purpose of this study is to document the Cristo Rey tracksite assemblage, analyze the stratigraphy, ichnotaxonomy, and track anatomies and compare these with several other late Albian-early Cenomanian tracksites located in Northern New Mexico and Southern Colorado. The Cristo Rey tracksite assemblage correlates stratigraphically and ichnotaxonomically with the Dakota Megatracksite (Dinosaur Freeway) of New Mexico, Colorado, and Oklahoma. ^ Ichnogenera and stratigraphy of three additional tracksites from the Dinosaur Freeway were compared to the Cristo Rey tracksites. These are the Dakota Formation, at Dinosaur Ridge, Denver, Colorado; the Dakota Formation, Clayton Lake, New Mexico, and the Mesa Rica Formation at Mosquero Creek, New Mexico. Studies of each of these tracksites reveal that they have similar ichnogenera and stratigraphy to the Cristo Rey site. Thus, the ichnotaxa at Cristo Rey may provide more compelling evidence for the "ichnofacies concept." Stratigraphic correlation of the track-bearing beds provides information about paleoenvironment and evidence for whether or not tracks preserved in the Dinosaur Freeway are all from the same environment, and if this is an effect of paleoenvironmental preservation or behavior. ^ Stratigraphy of the Sarten Member at Cristo Rey shows evidence of a transgression, most likely the onset of the Greenhorn cyclothem. Channels eroded in the underlying Mesilla Valley shale are filled in by the transgressive Sarten Member, with interbedded marine shales and cross bedded sands this unit records evidence of a tidal/estuarian environment, evidenced sedimentary structures, as well as abundant vegetative matter in the shales. ^ Further, a comparison of internal and external track structures herein focuses on track illustration techniques and symbols. The purpose of this component of the study is to further evolve the language with which paleotrackers describe internal and external track structures. Two structures are mentioned and compared, the "wave" and the "dish." The dish apparently shows more effort in motion than the wave.^
Kappus, Eric J, "Middle Cretaceous dinosaur tracks at Cerro de Cristo Rey, Sunland Park, New Mexico and a comparison with other paleocoastal tracksites of the southwestern US" (2007). ETD Collection for University of Texas, El Paso. AAI1444114.