Date of Award
Campus Access Dissertation
Doctor of Philosophy (PhD)
Environmental Sciences/Environmental, Earth & Ocean Sciences
One method to gain perspective on the consequences of modern climate change and future projections is to study, or reconstruct, climate change events in Earth’s past (paleoclimate reconstruction). Recorded in the geologic rock record are the paleoenvironmental conditions prior to, during, and after past climate change events. One of the most important events in Earth's past was the end-Permian mass extinction, the largest extinction event in Earth's history. Similar to modern climate change scenarios, the Permian-Triassic transition, at around 252 million years ago, was a period of increasing temperatures, rising sea level, and ocean acidification. However, a more complete understanding of climate conditions leading up to, during, and after the end-Permian extinction event is required. The sulfur cycle records important paleoenvironmental conditions as it is linked to proposed drivers of the end-Permian extinction such as volcanic, continental weathering, and oceanic redox processes.
This dissertation consists of three separate projects which are connected by location or time interval and methods. The overarching goal of this work is to provide a clearer understanding of the Permian-Triassic world by analyzing the marine sulfur cycle from two understudied paleoceanic regions (southern Neo-Tethys and eastern Panthalassa) using local and global paleoenvironmental proxies. I investigated local environmental conditions of the southern Neo-Tethys Ocean millions of years prior to and following the end-Permian mass extinction. In addition, I reconstructed global changes to the marine sulfur cycle, as recorded in the southern Neo-Tethys and eastern Panthalassa, during the initial ~1.5-2 million years of Early Triassic recovery.
From this work, I determined that: (1) environmental instability and deterioration developed in the southern Neo-Tethys well prior to the end-Permian mass extinction; (2) three eutrophic intervals occurred within the southern Neo-Tethys during cooling stages of the Early Triassic; (3) different regions show the same secular trend in seawater sulfate isotope values for the Early Triassic but different absolute values as a consequence of low seawater sulfate concentrations; (4) seawater sulfate concentrations increased gradually from a Permian-Triassic boundary minimum to higher values by the early Spathian; and (5) the marine sulfur cycle experienced a transient perturbation at the Smithian-Spathian boundary (late Early Triassic) owing to rapid cooling and invigorated oceanic circulation.
Stebbins, Alan Gates, "Understanding the Permian-Triassic Extinction and Recovery through the Sulfur Cycle: A Multiproxy Approach Using Pyrite and Carbonate-Associated Sulfate" (2018). Graduate Doctoral Dissertations. 395.
Available for download on Friday, November 30, 2018