Assessing the effects of fluvial abrasion on bone surface modifications using high-resolution 3-D scanning

Gumrukcu, Merve, author
Pante, Michael, advisor
Glantz, Michelle, committee member
Lacy, Michael, committee member
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Cut marks and carnivore tooth marks on fossil bones are important traces of the behavior and ecology of our ancestors. However, these traces are often obscured by other taphonomic processes such as fluvial abrasion. Previous studies on the effect of fluvial abrasion on cut marks suggest that sediment abrasion in fluvial environments can change the overall morphology of cut marks. Thus, analyzing the effects of fluvial abrasion on cut mark and tooth mark morphology is crucial to interpreting archaeological bone assemblages accurately. The objective of this research is to understand the effects of fluvial abrasion on cut marks and mammalian carnivore tooth marks using high-resolution 3-D data. An experimental study was undertaken by tumbling cattle and deer bones in a rock tumbler filled with sand and water. Bones were abraded in a rock tumbler with a sand and water mixture for 152 hours. The 3-D data from cut marks and carnivore tooth marks was collected and analyzed using a white-light confocal profilometer. Qualitative macroscopic analysis shows that bone surfaces became smoother and polished after tumbling. Most cut marks and tooth marks were still visible. Results indicate that 57.1 percent of the cut marks lost their characteristic internal parallel striations and 18.4 percent of the cut marks were highly abraded and reduced to rounded indentations after tumbling. However, 65.3 percent of the cut marks preserved at least one diagnostic feature. Most of the tooth marks (78.3%) preserved all characteristic features, such as crushed internal surfaces, high breadth: depth ratios, and U-shaped cross-sections and 100 percent of the tooth marks carried at least one diagnostic feature after tumbling. Only 21.7 percent of the tooth marks lost one diagnostic feature (crushed internal surface). Quantitative analysis based on the 3-D data also indicates that fluvial abrasion has a greater effect on cut marks than tooth marks. Measurements obtained from 3-D analysis of the cut marks and tooth marks show that some measurements of the micromorphology of cut marks changed significantly after tumbling, while tooth marks were not significantly altered by tumbling. Additionally, multivariate analysis using the measurements of the micromorphology allowed discrimination between cut marks and tooth marks with 100% accuracy before and after tumbling.
2017 Spring.
Includes bibliographical references.
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