189-12 Cretaceous Line Dance: Documenting the Formation and Deposition of a Theropod Dinosaur Trackway from the Upper Glen Rose Formation, Hamilton County, Central Texas, USA

Session: Paleontology, Paleoecology/Taphonomy (Posters)

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Abstract:

The Lower Cretaceous (Albian) Glen Rose Formation and other similarly aged stratigraphic formations exposed across much of Central Texas are world-renowned for yielding thousands of fossilized tracks of theropod, sauropod, and ornithopod dinosaurs. The sedimentary context of the Glen Rose reflects the initial transgression of a transgressive-regressive (T-R) sequence within the Lower Cretaceous Trinity Group (Aptian-Albian), highlighting sea-level fluctuations throughout Early Cretaceous North America. Typically, Glen Rose track sites are found on shallow marine carbonate deposits that formed during times of aerial exposure, known as sequence boundaries. The Shive Site assemblage, located in Hamilton County in Central Texas, represents a newly documented track site. The Shive Site consists of at least twenty-two three-toed (tridactyl) tracks exposed along an 18-meter-long limestone shelf, with three apparent trackways identified. Based on their size and shape, the tracks are interpreted to belong to the large theropod dinosaur Acrocanthosaurus atokensis. The tracks have varied preservation, ranging from complete preservation of the whole tridactyl track to incomplete preservation with only toe marks being observable. Most of the tracks show evidence of soft sediment deformation or mud-collapsing during their formation. The tracks head both northward and southward, but the vast majority (80%) head south-southeast. In one case, a south-heading track is overlain by a northward track, potentially suggesting gregarious behavior and that the trackmakers were moving back and forth along the local coastline. The track-bearing layer is a coarse grainstone riddled with Thalassinoides burrows (Cruziana ichnofacies), indicating that it was deposited in a shallow marine, lower shoreface setting. Overlying the track layer are interbedded, fine-grained shales that feature traces of carbonate wood and fossil leaf material. Heavily nodular grainstones featuring multiple genera of marine invertebrates, including the biostratigraphically informative echinoid Loriolia rosana, overlie these shale deposits, indicating a rapid transgression following the deposition of the dinosaur tracks. Taken together, our geological analyses and documentation of the tracks with variable preservation suggest that the tridactyl tracks at the Shive Site were formed in a short-lived single event along a shoreline during a marginal-marine sequence boundary in the Upper Glen Rose Formation, providing new insights into the paleoecology of theropod dinosaurs in Central Texas during the Albian.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4324

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