217-4 Towards the quantification of bone weathering: new insights from 3D surface profilometry

Session: Paleontology, Paleoecology/Taphonomy

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Abstract:

Surface textures of bones have long been used to estimate the amount of time that skeletal elements have been exposed and weathered prior to burial. The most common method for assessing these patterns uses semi-quantitative “weathering stages,” which use broad visual differences in bone surface textures to categorize bones based on their most-weathered surfaces. While weathering stages are quick to evaluate and can broadly differentiate the taphonomic states of bones, this and other semi-quantitative systems are limited in their capacity to describe the full gradient of bone weathering (including intermediate weathering stages). Further, differential rates of weathering among different anatomical regions on the same bone (e.g., articulation surfaces vs. muscle attachments) can be obscured when characterizing bone weathering based on the most-weathered surface. Such differences in bone weathering rates may even lead to spurious paleobiological interpretations when comparing the time-averaging of deposits composed of mostly complete bones from those composed or more fragmentary remains. Additionally, bone weathering in different environments may not be fully captured by a single suite of weathering stages, complicating taphonomic comparisons of bones and bone accumulations from different settings. Establishing more fully quantitative metrics of bone weathering has potential to minimize these issues and provide a next-level understanding of bone weathering processes, and the environmental and temporal histories of bone accumulations from both extant and extinct ecosystems. Here, we use 24 elk humeri from Yellowstone National Park (Wyoming) to test the capacity of quantitative surface roughness parameters (evaluated using 3D optical profilometry) to quantify bone weathering and to evaluate differences in weathering among different classes of bone anatomy (articular surfaces, muscle attachments, and more generically smooth bone surfaces). We found that surface roughness generally increased as weathering intensified and that bones in different weathering stages had significantly different roughness values. These differences were maximized when we summarized a single bone’s surface roughness by integrating multiple parameters of surface roughness and multiple surfaces. We also found that weathering trajectories of different classes of bone anatomy are not uniform, with muscle attachments generally weathering faster than other bone surfaces, particularly during the initial periods of weathering. Characterizing bone weathering using quantitative metrics of 3D surface roughness can expand our understanding of bone weathering process and time-averaging of fossil and modern bone accumulations.

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

doi: 10.1130/abs/2025AM-8734

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