This proposal aims to determine the nature of the environmental perturbation at the end-Triassic mass extinction by comparing lipid biomarker and bulk carbon isotopic records from mid-ocean and more restricted marine rift basins. This extinction, at 201.5 million years ago, is one of the "big five" mass extinctions in Earth history, and is associated with multiple, massive increases in CO2 and global warming linked with eruptive pulses of the voluminous Central Atlantic Magmatic Province basalts. PIs' study will be the first to examine in detail a mid-ocean record (Panthalassic basaltic plateau of the Queen Charlotte Islands, Canada) and contrast that with records from shallower sections in restricted marine basins in the United Kingdom that have dominated the discussions of the mass extinction. This proposed analysis is of critical importance for understanding this singular moment in Earth history, as well as unraveling the specific cause and effect mechanisms of extinction events in general, by remedying the dearth of studies that utilize taxonomically and environmentally diagnostic compounds that can test specific hypotheses regarding environmental change and extinction mechanisms. In an effort to support emerging scientists from underrepresented groups, this proposal will support one high school summer intern from School District 50 (encompassing the Queen Charlotte archipelago) to assist with lab work and hone geologic skills. Furthermore, PIs will co-lead a summer field trip for tenth grade students of School District 50, and their discoveries will be incorporated into the science curricula and educational programs for 2nd, 4th, 7th, and 10th grades, exposing science to hundreds of students belonging predominantly (65%) to the Haida Nation and other First Nations tribes, highly underrepresented groups in the sciences. New research will be incorporated into the curricula of Brown University and MIT and will be incorporated into K-12 educational outreach programs at schools local to PI institutions, in which multiple undergraduate and graduate students participate.
The end-Triassic mass extinction 200 million years ago was one of the most destructive in the history of life. It led to the development of the modern ecosystem and paved the way for the dominance of dinosaurs. This study focused on extracting fossil molecules from rocks deposited on the bottom of ancient Triassic and Jurassic oceans as preserved in rocks at Haida Gwaii, British Columbia, Canada. These rocks were geologically tilted from their original positions and are thus preserved as slanted layers in the intertidal zone on the beach (please see A and B in the attached figure). The lead up to and effects of the extinction are tracked through the analysis of fossils of various shelled animals, including various species of clams (see C in the attached figure) and ammonites (see D in the attached figure), and the chemical and isotopic analysis of biomarkers (organic compounds derived from the molecular remains of microorganisms that lived in the water column and seabed). Our research is aimed particularly at using these biomarkers to address the specific effects of global climate change that are the ultimate cause of destructive events like the end-Triassic mass extinction. For example, the lack of oxygen or lack of nitrogen in large portions of the ocean can disrupt the organisms that are at the base of the food chain. Because these organisms are so crucial to any ecosystem, major shifts in species can have dramatic effects all the way up the food chain. One specific phenomenon at the base of the food chain that has driven our research is referred to as "photic zone euxinia." Many organisms deep in the ocean, where there is little or no oxygen, essentially "breathe" using various forms of the element sulphur. The byproduct of this activity is hydrogen sulphide, which is extremely toxic to most forms of life. If there is an extreme lack of oxygen in a given water body, hydrogen sulphide can expand away from the deep waters and move up to the surface. Photic zone euxinia occurs when this hydrogen sulphide reaches the portion of the water column that receives light from the sun. This is an extreme condition (it occurs in the present-day Black Sea and the west coast of Africa, for example) and only a very specific class of organisms can survive in it. Our research measuring the biomarkers for these organisms demonstrates that photic zone euxinia was pervasive and widespread during this interval of time. Since expansion of oxygen minimum zones is a measurable consequence of current and projected trends in atmospheric CO2 and global warming, our work serves as a cautionary tale for scenarios forecasted for the next century.
