135-9 Assessing Terrestrial Community Response to Aridification: Analysis of Vertebrate Tracks of the Lower Jurassic of Zion National Park (Moenave Fm, Kayenta Fm, Navajo Sandstone), UT, USA

Session: Science and Stewardship of U.S. National Park Service Paleontological Resources

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Abstract:

Zion National Park (ZION) is host to significant paleontological resources which hold rich data concerning the history of life on our planet, particularly during the Early Mesozoic. Unfortunately, ZION is also host to one of the highest erosional rates in the National Park Service (NPS), at roughly 400 m (1,300 ft) per million years. As a result, new fossils become rapidly exposed and weather at high rates. In order to mitigate this rapid turnover of fossils, ZION is utilizing photogrammetry to help monitor site conditions over time and to quickly preserve site data in a digital repository. This project aims to use the abundant fossil tetrapod tracks identified within the Moenave, Kayenta, and Navajo Sandstone formations to better understand how the terrestrial vertebrate fauna of the Lower Jurassic responded to increased aridification and resulting environmental changes. Through the Lower Jurassic ZION section, depositional environments shifted from fluvio-lacustrine within the Moenave Formation, fluvial in the Kayenta Formation, to extensive eolian dune complexes in the Navajo Sandstone. Due to a relatively poor body fossil record within ZION, trace fossils serve as the primary proxies of biodiversity. Approximately 150 fossil tracks were described from 15 sites within ZION. The tracks were preserved both in situ and on float blocks that could be tied to specific stratigraphic horizons. Photogrammetric software (RealityCapture, version 1.5.1) was used to create 3D models of the fossil tracks. From these models detailed measurements of digit divarication angles, digit lengths, and overall track length and width could be made to better identify them taxonomically as well as to assess potential tracemakers and behavioral significance. Tridactyl fossil track models were additionally analyzed using machine-learning algorithms to aid in the differentiation between ornithopod and therapod track morphologies. Distinctions between fossil track morphologies and ichnotaxa identification were used to measure faunal composition and diversity during the three depositional phases of the studied section. As current aridification continues to impact ecosystems around the world, understanding how terrestrial communities are affected by these changes is essential to our response.

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

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