Climate change across the terrestrial Eocene-Oligocene boundary of the Great Plains is recorded by shifts in sediments, facies, paleosols, and isotopic records, and is interpreted as a shift to overall cooler and drier conditions. As an independent test of paleoenvironmental shifts caused by climatic change, I compared microwear on M2 molars of Leptomeryx from the White River Group (WR) at Toadstool Park, Nebraska (n = 9) and Flagstaff Rim, Wyoming (n = 11). Comparisons of microwear were made through time at each section. Various measurements of microwear were quantified on original, uncoated specimens using environmental scanning electron microscopy and Microware 4.0 software, and evaluated with ANOVA and Kruskal-Wallis statistical tests. Values of the scratch:pit ratio, scratch number, feature major:minor axis ratio, feature vector length, major axis standard deviation, major:minor axis standard deviation, and feature orientation standard deviation for Leptomeryx M2 molars are significantly different (p<0.05) between Wyoming and Nebraska. Microwear patterns suggest paleoecological differences between the two locations, possibly related to differences in Leptomeryx diet or in amount or character of sediment adhering to ingested vegetation. Little fossil evidence of vegetation type is preserved at either locality, other than clay-filled root traces or occasional rhizoliths or silicified fragments. However, sediments of the WR are a mixture of volcaniclastic enriched mudstone, siltstone, and sandstone, with generally coarser overall particle sizes in Wyoming that reflect proximity to siliciclastic sources. The degree of overall volcaniclastic enrichment and number of airfall tuffs is also higher at Flagstaff Rim. Paleosols suggest a shift from closed canopy forest to progressively open conditions at each locality and, although microwear differences could result from differences in vegetation or particle sizes of adhered sediments on plants, no or very low correlations between microwear features and stratigraphic level were detected at either locality, indicating that any changes in paleoecology over time did not significantly alter the diets of Leptomeryx, although diet may have been geographically different. / Geology
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/2348 |
| Date | January 2016 |
| Creators | Shackelton, Allison Lee |
| Contributors | Terry, Dennis O., 1965-, Tumarkin-Deratzian, Allison, Grandstaff, David E. |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Format | 80 pages |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/2330, Theses and Dissertations |
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