61-2 Digital outcrop ichnological and sedimentological analysis of R.T Bird’s historic herding sauropod site, Lower Cretaceous, Glen Rose Formation at the Davenport Ranch, Medina County Central Texas

Session: Advancing Geologic Analysis with Digital Outcrops and Close-Range Remote Sensing Data (Posters)

Poster Booth No.: 69

Presenting Author:

Wyatt Kenny

Authors:

Kenny, Wyatt O.¹, Loewenstine, Cody², Price, Dianna³, Tesauro, Josephine⁴, Adams, Thomas L.⁵, Godet, Alexis⁶, Locker, Megan⁷, Locker, Brooke⁸, Surpless, Benjamin E.⁹, Lehrmann, Daniel J.¹⁰

(1) Earth and Environmental Geosciences, Trinity University, San Antonio, Texas, USA, (2) Earth and Environmental Geosciences, Trinity University, San Antonio, Texas, USA, (3) Earth and Planetary Sciences, University of Texas at San Antonio, San Antonio, Texas, USA, (4) Earth and Environmental Geosciences, Trinity University, San Antonio, Texas, USA, (5) Witte Museum, San Antonio, Texas, USA, (6) Earth and Planetary Sciences, The University of Texas at San Antonio, San Antonio, Texas, USA, (7) Davenport Ranch, Stockdale, Texas, USA, (8) Davenport Ranch, Stockdale, Texas, USA, (9) Earth and Environmental Geosciences, Trinity University, San Antonio, Texas, USA, (10) Earth and Environmental Geosciences, Trinity University, San Antonio, Texas, USA,

Abstract:

The Davenport Ranch is a historically important dinosaur tracksite where, in 1940, R.T. Bird interpreted herding sauropods from the Lower Cretaceous Glen Rose Formation. Bird originally described the Davenport site from a single pavement surface. Over the years much of the surface has become buried under fluvial deposits. 

Our study documents three track surfaces including two horizons 0.4 and 0.7 m below the surface originally described by Bird. We used drone photogrammetry, digital outcrop mapping and field observations to document the track surfaces and petrography to interpret depositional environments. The lower track horizon contains numerous depressions interpreted to be poorly preserved tracks, as well as a few identifiable sauropod and theropod footprints. Only a single theropod trackway could be measured. Displacement rims permit to differentiate tracks from weathering and erosional features. The middle track surface is exposed in a bedding surface ~30 cm wide and contains poorly defined tracks with displacement rims.  The uppermost surface contains the best-preserved tracks including numerous well-defined sauropod and theropod tracks and trackways with claw marks and pad impressions, and displacement rims. 

Each track surface is composed of dolostone containing peloids and a low diversity biota of ostracodes indicating a hypersaline, restricted-marine shoreline environment. The uppermost track surface contains microbial laminate, fenestrae and autoclastic breccia indicating subaerial exposure on tidal flats. We interpret the difference in preservation of the track horizons to represent the varying sediment rheology upon which the dinosaurs walked and perhaps also the number of dinosaurs that crossed the surface. We interpret the poor preservation of tracks in the lower surface to have resulted from a wet and soft, “sloppy” rheology causing the tracks to slump and deform during and after the tracks were made. Further, the surface appears to be “dinoturbated” or complexly trampled such that it difficult to identify distinct trackways. The middle track surface appears similar to the lower surface, but its exposure is not adequate to fully evaluate. We interpret the much-better preserved tracks in the upper surface to have resulted from a soft but firm rheology due to the fact that it contains a microbial laminite (which would have had a leathery consistency by comparison to modern microbial mats) and due to partial  desiccation and lithification as evidenced by autoclastic breccia.

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

doi: 10.1130/abs/2025AM-5037

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