176-7 Antlers Abound: Assessing the Rates of Weathering Across a Latitudinal Gradient

Session: Laws of the Grave: Advances in Taphonomy Across the Paleontologic Record

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Abstract:

Comparing the biological information recorded in time-averaged fossil assemblages requires an understanding of the amount of time across which those deposits accumulated. Without such context, it becomes increasingly difficult to compare biological metrics (e.g., species richness) among multiple deposits that are sensitive to both temporal sampling and other taphonomic and sedimentary variables. For terrestrial vertebrate settings, the weathering stages of bones have long been used to estimate the time (number of years) over which a bone accumulation had formed. The most widely used system for assessing bone weathering was established and calibrated in a semi-arid, equatorial setting (Amboseli, Kenya), where bones persist on landscape surfaces for between 15 and ca. 30+ years. However, bones in temperate and arctic systems can persist (weathering) on landscape surfaces for centuries and millennia, respectively. These order-of-magnitude differences in weathering duration across latitudes highlights the complexities of inferring time from weathering state alone and calls for more refined understanding of how bone weathering rates change as a function of environmental setting. Here, we use shed antlers collected from across North America (Texas, MAT 19ºC; Utah, MAT 13ºC; South Dakota, MAT 9ºC; Arctic Alaska, MAT -7ºC), to test for differences in the rates of taphonomic decay. Antlers are a useful system for studying bone weathering because they are readily available on landscape surfaces and are morphologically constrained, minimizing the potential influences of shape or bone thickness on weathering rate. Antlers (Odocoileus hemionus, n = 25; O. virginianus, n = 6; Rangifer tarandus, n = 49) were recovered through taphonomic surveys and contributions by wildlife biologists, shed antler sellers, and taxidermists. These antlers, representing a range of taphonomic conditions, were radiocarbon dated to determine each specimen’s weathering duration. Prior to dating, specimens were sorted by size class and evaluated for their weathering stage. Results demonstrate that bone weathering is demonstrably slower in colder settings. For example, bones in weathering stage 4 from UT are (on average) 16 years younger than similarly weathered bones in TX. While weathering stages provide useful insight into relative weathering duration of bones within a setting, estimates of subaerial exposure based on those same characteristics can be dramatically different among environmental settings.

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

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