This project histologically examined weathering on faunal bones. The sample consisted of a mixture of faunal remains, assessed and assigned to weathering stages (WS) 0-2 from Behrensmeyer’s (1978) scoring method. A total of 77 bones sections were observed for histological analysis. A portion were obtained, partially fleshed, commercially and were placed at the Outdoor Research Facility (ORF) in Holliston, MA. After deposition, bones were collected at specific time intervals allowing for 2, 4, 6, 8, 12, and 18-month exposure times. Bones were also collected from several outdoor locations in Ohio, having been exposed for an unknown period, and ranging from WS 0-2. Following histological preparation of the sample, the microstructure of each weathering stage was observed using the image analysis software Fiji from the National Institutes of Health (NIH).
Data recorded included the number of cracks present per unit area and the depth of cracking. The number of cracks per unit area for each section of bone was calculated by dividing the number of cracks per section by the total section area resulting in number of cracks per mm2. Depth of cracking was analyzed through maximum crack length and average crack length. This data was compiled and one-way ANOVA tests were applied to determine where weathering stage and exposure time were statistically significant. This was followed by Bonferroni post-hoc analyses which were utilized to analyze the interactions within the WS and exposure time variables; to allow for analysis of statistical significance of WS to one another and exposure time intervals to one another. It was hypothesized that different weathering states would be statistically significant from one another, and microscopically identifiable through a histological examination, and that these would be able to be differentiated from other sources of microtaphonomic alteration including burial and thermal alteration. It was also hypothesized that exposure time would significantly impact the histological characteristics including the number of cracks per mm2 and the maximum and average crack depth.
One-way ANOVA analysis indicated that WS has a significant impact on the number of cracks per mm2 and the maximum crack length. No significance was observed for analysis of WS and average crack length. Post-hoc analysis involving the number of cracks per mm2 revealed statistical significance between WS 0 and WS 1, WS 0 and WS 2. Analysis involving maximum crack length indicated significance only between WS 0 and WS 1. Post-hoc analysis involving average crack length did not indicate any statistically significant relationships between the WS.
One-way ANOVA analysis of exposure time indicated that exposure time has a significant impact when on all three variables: number of cracks per mm2, average crack length, and maximum crack length. Post-hoc analysis involving the number of cracks per mm2 found that months 0, 2, 4, 6, and 8 were all statistically significant from 18 months. Analysis of average crack length revealed that months 0 and 2 were both statistically from 8 months of exposure. Post-hoc analysis involving maximum crack length reveals statistical significance between months 0 and 8, 0 and 12, and 2 and 8.
Histological characteristics of weathered bone were found to include delamination and cracking. Delamination was observed on several bones in WS 2 and one in WS 1, while cracking was observed in bones of all stages. Positive relationships were observed between WS and number of cracks per mm2, and between exposure time and cracks per mm2 indicating that as one increased so did the other. No trend was observed for the relationship between exposure time and either of the crack length variables; the same was observed for the relationship between WS and the two crack length variables.
Through comparison of the histological characteristics of weathered bone with other sources of microtaphonomic alterations, it was determined that weathering and its histological characteristics are different from other alteration sources, including burial and thermal alteration, to allow for determination of the microtaphonomic process affecting the bone.
Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/44008 |
Date | 10 March 2022 |
Creators | Liggett, Isabella A. |
Contributors | Pokines, James T. |
Source Sets | Boston University |
Language | en_US |
Detected Language | English |
Type | Thesis/Dissertation |
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