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217-5 Rolling on the River: Experimental Exploration of Bone Transport and Burial in Fluvial Flow

Session: Paleontology, Paleoecology/Taphonomy

Presenting Author:

Michael Chiappone

Authors:

Chiappone, Michael¹, Guala, Michele², Paola, Chris³, Rogers, Raymond⁴, Makovicky, Peter⁵

(1) Department of Earth & Environmental Sciences, University of Minnesota, Minneapolis, MN, USA, (2) St. Anthony Falls Laboratory, Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, MN, USA, (3) St. Anthony Falls Laboratory, Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA, (4) Geology Department, Macalester College, St. Paul, MN, USA, (5) Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA,

Abstract:

Well supported interpretations of paleoecology and potential preservation biases rely on a thorough understanding of taphonomic processes in the fossil record. Bones preserved in fluvial and floodplain sediments make up a large portion of the terrestrial vertebrate record, and how skeletal material interacts with sediment in these dynamic systems can inform important taphonomic interpretations of fossil sites (sorting, allochthony vs autochthony, burial mechanisms, etc). Here we experimentally investigate transport and burial potentials of a suite of vertebrate bones across a variety of flow conditions.

In a 0.9 m wide and 14.6 m long experimental flume, bedforms frequently stalled and trapped bones during transport. Bones representing a variety of shapes and sizes often became caught between bedforms due to recirculation vortices, which can form on the lee side of a dune. Once trapped, two outcomes were observed. If a bone remained unstable, jostling about within a bedform trough without fully stopping, it could be ejected from the recirculation vortex, and transport would resume. If a bone was stalled and stabilized, bedforms could then migrate over it and bury it (at least temporarily). During this process, scouring of sediment from under the bone further assisted in burial. However, scouring tended to slow over the course of 9 hours of flow exposure, suggesting that while it may aid in restricting further transport, scour action alone may not be enough to lead to permanent burial. As a result, other factors, such as bedform migration and pulsed sediment delivery (such as in floods) may be required to complete the burial process. In terms of transport, both critical flow velocity and transport distance correlated with bone density and aspects of shape, such as centroid height, that influence a bone’s response to the kinetic energy of the flow. While the classic Voorhies Groups did capture some of the broad variation in critical mobility conditions among the bones we tested, transport groups significantly overlapped, and many bones exhibited behavior that would not be predicted based on their Voorhies Group identities alone. Arguably, more direct quantitative approaches are needed to evaluate transport and winnowing due to the varying characteristics of bones in the vertebrate skeleton and the diverse geological contexts that host the vertebrate fossil record.

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

doi: 10.1130/abs/2025AM-8110

Rolling on the River: Experimental Exploration of Bone Transport and Burial in Fluvial Flow

Description

Session Format: Oral

Presentation Date: 10/21/2025

Presentation Start Time: 02:30 PM

Presentation Room: HBGCC, 305

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