Master's Theses

Department

Geosciences

Degree Name

Master of Science (MS)

Abstract

Stable isotope geochemistry provides a way of examining both modern and ancient ecosystems. One important use of stable carbon isotopes is to determine the amount of C3 versus C4 plant biomass in the diet of herbivorous mammals. C3 plants have a more negative stable carbon isotope ratio (δ13C) than C4 plants because of the different photosynthetic pathways each type uses. These different δ13C values are preserved in the hydroxyapatite of herbivores upon consumption of the different plant types. The purpose of this study it to use δ13C values from serial samples of tooth enamel from six isolated permanent molars of Teleoceras fossiger, an extinct North American rhinoceros from the Early Hemphillian, to determine what type of vegetation was consumed by these animals and if the diet reflects the amount of C4 biomass present in the ecosystem. The δ13C values from the T. fossiger samples show a range between -11.2‰ and -7.2‰ (all vs. VPDB, same below). These δ13C values indicate the diet of T. fossiger contained little to no C4 biomass. Using an ecosystem model developed for the Late Neogene of Nebraska, all of these data, except for two points, fall within an open canopy ecosystem (-12.1‰ to -7.7‰), an open grassland consisting of little to no C4 vegetation. The two data points (-7.6‰ and -7.2‰) that do not fall within an open canopy ecosystem, fall within the mixed C3/C4 ecosystem (-7.7‰ to 2.1‰). Paleobotanical and paleosol carbonate data collected from the Minimum Quarry, which is the quarry where the sampled T. fossiger teeth were collected, shows approximately 20% C4 biomass in the ii ecosystem. The difference between the diet of T. fossiger and the percentage of C4 biomass in the ecosystem demonstrates that although there are C4 grasses present, these rhinoceroses did not incorporate a major C4 component into their diet.

Keywords

C3, C4, Hemphillian, Minimum, Isotope

Advisor

Dr. Chunfu Zhang

Date of Award

Spring 2017

Document Type

Thesis

Rights

© The Author(s)

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