Earth and Planetary Sciences ETDs
Publication Date
Summer 5-31-2022
Abstract
Carbonate precipitation in perennially ice-covered Lake Fryxell, McMurdo Dry Valleys, Antarctica produces a modern analog for Antarctic paleolake carbonates. Lake Fryxell contains a steep oxycline in the photic zone, where dissolved oxygen falls from supersaturation to zero. In the lake’s benthic microbial mats, oxygen concentrations are higher than in the water column due to microbial photosynthesis. These mats contain carbonate cements that precipitated in a discrete episode from mat pore waters. Precipitation continued through seasonal fluctuations in oxygenation, demonstrated by variable concentrations of oxidized and reduced manganese and iron within carbonates. Carbonates precipitated out of isotopic equilibrium with the lake water column and are enriched in 18O relative to expected values. Carbonate δ18O varies by >20‰ across μm to mm; carbonate triple oxygen isotopes suggest mixing of a modified marine water with lake water as an explanation for both isotopic heterogeneity and a possible trigger for this episodic carbonate precipitation.
Degree Name
Earth and Planetary Sciences
Level of Degree
Masters
Department Name
Department of Earth and Planetary Sciences
First Committee Member (Chair)
Tyler Mackey
Second Committee Member
Laura Crossey
Third Committee Member
Corinne Myers
Fourth Committee Member
Cristina Takacs-Vesbach
Language
English
Keywords
Antarctic carbonates, McMurdo Dry Valleys, Lake Fryxell, carbonate oxygen isotopes, paleoclimate, carbonate redox
Document Type
Thesis
Recommended Citation
Clance, Jared. "Petrographic and Geochemical Records of Climate Perturbation in Carbonates from a Perennially Ice-Covered Antarctic Lake." (2022). https://digitalrepository.unm.edu/eps_etds/301
Comments
Second submission; corrected month of graduation on title page.