Camelin McKay
Pronouns: she/her
Research Mentor(s): Diana Velazquez
Research Mentor School/College/Department: Department of Earth and Environmental Science / SNRE
Program:
Authors:
Session: Session 6 3:40-4:30 p.m. Hussey Room
Poster:
Abstract
Ancient lacustrine sediments encode biogeochemical information pertinent to understanding the evolution of primary producers throughout Earth’s geological history. In particular, shifts in dominant primary producer communities following the onset of Earth’s oxygenation 2.45 billion years ago (Great Oxygenation Event) provide insight into the role of redox conditions on microbial evolution. As a first step to determining if and how oxygenation affected primary production in terrestrial environments, we aimed to identify the presence of porphyrins in sediments from the 1.1 Ga Nonesuch Formation. Porphyrins are the biomarkers of chlorophyll which are preserved in the geologic record and provide insight into ancient biogeochemical processes. The proxy used for determining photosynthetic communities are epor values, which record the isotopic offset between d15Nbulk and d15Nchloropigment. Cyanobacteria and eukaryotes display unique ranges of epor which can be used to distinguish between these photosynthetic communities. The Nonesuch Formation, located in the Keweenaw Peninsula of Michigan and extending to the Wisconsin shore of Lake Superior is a shale rich unit with exceptional microbial preservation. We analyzed sediment cores (n = 5) for total nitrogen. The samples with the highest percent nitrogen by weight included samples from cores DO6 (Wisconsin) and WPB4 (Michigan). We then conducted porphyrin extractions on these samples and verified the presence of porphyrins through high performance liquid chromatography (HPLC), an instrument capable of identifying sample components based on absorbance. Further analysis will include collection of d15Nbulk data in order to obtain epor values. To determine whether Earth’s oxygenation impacted terrestrial and marine environments uniformly, we plan to compare porphyrin nitrogen isotopes from the Nonesuch Formation to those of a similarly aged marine basin.
