ELT COLLABORATIVE RESEARCH: Perturbation of the Marine Food Web and Extinction During the Oceanic Anoxic Event at the Cenomanian/Turonian Boundary

OVERVIEW The Cenomanian-Turonian boundary (CTB; 94 million years ago), a time interval marked by mass extinction, was also characterized by global oxygen deficiency and likely ocean acidification. Thus, the CTB is an excellent ancient model for the impact of anthropogenic activities on marine ecosystems. A superb opportunity exits to explore the impact of oxygen deficiency and ocean acidification during the CTB in highly expanded sections from the western and southern margins of the Western Interior Seaway. In Utah, sections of the Tropic Shale contain original ammonite aragonite as well as remains of large marine reptiles. In Texas, British Petroleum has made available a unique core of the Eagle Ford Shale and exclusive access to outcrop sections. Back-hoeing will unearth pristine fossil shells suitable for environmental proxy analyses, and additional coring will provide section that can be scanned to obtain orbital time control and sampled at sub-millennial resolution. Proxy measurements designed to unravel the nature of the environmental changes will be combined with biomarker and paleontological studies to determine the biological impacts on microbes to top carnivores. Modeling will explore the relationship between trophic levels and the nature of the environmental controls, both local and global. INTELLECTUAL MERIT The expansion of oxygen-deficient waters, as a result of warming and pollution, can affect all marine organisms through the loss of habitat, alteration of microbial processes, changes in predator-prey dynamics, and availability of nutrients for primary production. Ocean acidification is already impacting the ability of many organisms to grow shells. The geological record contains a series of natural experiments that allow us to address the biological response of the biota to ocean acidification and widespread hypoxia. However, to date, studies of such geological intervals have been hampered by diagenetic alteration of materials for proxy measurements and an inability to obtain sub-millennial resolution required to match the timing of modern ecological studies. The research described above overcomes these shortcomings and can thus be used to evaluate two fundamental hypotheses regarding the cause of food web upheaval during the CTB and of broader intellectual merit: (1) Introduction of greenhouse gasses from volcanism initiated a gradual sequence of perturbations to habitats that culminated in species extinction and turnover; and (2) Extinction and biotic turnover were systematic and can be directly related to the nature of habitat perturbation combined with the ecology of the taxa.