Triassic and Jurassic vertebrate-dominated trace fossil assemblages of the Cimarron Valley region--Implications for paleoecology and biostratigraphy
Kelly Conrad, Martin G. Lockley, and Nancy K. Prince
Upper Triassic and Jurassic rocks of the Cimarron valley region of northeastern New Mexico and adjacent parts of Colorado and Oklahoma exhibit abundant, well-preserved ichnofaunas dominated by the tracks of reptiles.
The Late Triassic Dockum Group ichnofaunas, particularly those of the Sloan Canyon Formation, are the most diverse, and include the vertebrate ichnogenera Apatopus, Brachychirotherium, Chirotherium, Coelurosaurichnus and Rhynchosauroides, at least three invertebrate ichnotaxa including Scoyenia, and other distinctive but unnamed traces. The overlying Sheep Pen Sandstone exhibits three trace-bearing horizons that collectively exhibit only three named ichnotaxa, namely Brachychirotherium, Grallator and Scoyenia.
Whereas the Triassic ichnofaunas are exposed in the main Cimarron valley and its tributaries, Jurassic ichnofaunas in the Morrison Formation occur both in this valley and in the Purgatoire valley to the north. Preliminary stratigraphic correlations of Morrison Formation sections suggest that tracks probably occur in the lower part of the formation in both areas.
Because of the scarcity of biostratigraphically useful body fossils in these rocks, the ichnofaunas and associated stratigraphic and sedimentological information enhance our understanding of the paleoecology and probable biostratigraphic correlation of these units.
- Conrad, Kelly; Lockley, Martin G.; Prince, Nancy K., 1987, Triassic and Jurassic vertebrate-dominated trace fossil assemblages of the Cimarron Valley region--Implications for paleoecology and biostratigraphy, in: Northeastern New Mexico, Lucas, S. G.; Hunt, A. P., New Mexico Geological Society, Guidebook, 38th Field Conference, pp. 127-138.