PALEOENVIRONMENTAL RECONSTRUCTION OF LOWER CRETACEOUS DINOSAUR TRACKWAYS CENTRAL TEXAS

Sauropod and theropod trackways are common occurrences in the marginal marine deposits of the Albian (Early Cretaceous) Glen Rose Formation of Texas. Although numerous dinosaur tracks and trackways have been documented in detail across the state, little is known about the environment in which these tracks were made and preserved. Our project aims at developing stratigraphic correlations to inform on processes that influenced track preservation.

Seven track site locations are considered to reconstruct paleoenvironments using multiple techniques: the Blanco River in Blanco County, the South Fork San Gabriel River in Travis County, the VFW and Heritage Museum in Comal County, the Mayan Ranch in Bandera County, the Davenport Ranch in Medina County, and Government CanyonState Natural Area in Bexar County.

Field observations and petrography are used to determine how the depositional environment and diagenetic processes influenced track preservation. To support the interpretation of depositional environments from petrography, whole-rock samples are analyzed for elemental geochemical composition using x-ray diffraction spectrometry. The stratigraphic evolution of a selection of geochemical proxies for detrital (e.g., Ti, Zr) and nutrient (e.g., P, Cu) inputs below and above the track layers provides specific information about the paleoclimate and paleoenvironment before and after the impression was created. Chemical index of alteration (CIA) profiles and ternary diagrams are used to show proportions of Al₂O₃, Na₂O, and K₂O. Of interest is a slight increase of detrital input above the track layers at each site that may have facilitated its burial and preservation. Future work includes the development of stratigraphic correlations with additional track sites from central Texas. In addition, benthic foraminifera biostratigraphy and spectral gamma ray curves will help determine the paleoenvironmental significance of dinosaur tracks within a refined stratigraphic framework.