Environmental Impacts of Caribbean Plateau Volcanism: Timing and Composition of Magmatic Activity Related to Ocean Anoxic Event 2

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Intellectual MeritOceanic plateaus are anomalously thick oceanic crust, believed to have formed rapidly by enhanced partial melting of the mantle. A natural consequence of such massive submarine volcanism is the release of extraordinary amounts of heat and metal-rich fluids to the ocean over geologically brief intervals, which are likely to have produced changes in ocean chemistry that lead to ocean anoxic events (OAEs) and selective extinctions of marine organisms. The Cretaceous was a period of extreme climatic conditions accompanied by major perturbations in ocean-atmosphere biogeochemical cycles. One of the most intriguing features is the sporadic interruption of normal marine pelagic sediment deposition by organic-rich sediments deposited during oxygen-deficient conditions (OAEs). A current model for the abrupt onset and conclusion of these events relates delivery of biolimiting trace metals (nutrients) to the surface ocean during massive volcanic activity associated with ocean plateau construction, that increased phytoplankton production and lead to the eventual depletion of oxygen in the deep ocean and deposition of organic-rich sediments. It is proposed that the trace metals were releasedin degassed magmatic fluids plus hydrothermal effluents dominated by water/rock exchange. This study will specifically evaluate the proposed link between metal release associated with the construction of the Caribbean plateau and OAE2 at the Cenomanian-Turonian (C/T) boundary (~93.5 Ma). This will be done by (1) establishing a firmer time scale for the initial,volumetrically dominant phase of Caribbean plateau magmatic activity from thick crustal sections exposed on the northern and southern margins of the intact central plateau (in Haiti and Curaçao/Aruba), and by (2) determining the abundances of select trace metals in parental magmas for submarine lavas through analysis of melt inclusions in olivines and pyroxenes, for comparison with elemental abundances in glassy pillow margins of the same rocks. Trace metal abundance anomalies, as well as isotopic excursions in Pb, Os and Nd, have already been identified in near-field and far-field marine sedimentary sections that record OAE2. These findings are consistent with release from Caribbean plateau lavas.Broader ImpactsWe will support and mentor a graduate student, including training in field sampling, in radiometric dating and micro-analytical methods. Undergraduate students will be recruited from our cooperative program with the University Honors College that requires a senior thesis for graduation http://oregonstate.edu/dept/honors/research/coasreu). This program is also a feeder for a new 5-yr honors B.S. + M.S. in Earth System science, offered jointly by COAS and Geosciences (EarthSystem5). Funding for these students will be leveraged through University research office support for undergraduate research. We also participate in an NSF-funded COAS summer site REU, and with undergraduate-oriented colleges with limited analytical facilities (Redlands and Pomona). Duncan and Kent will supervise students in research methods andwriting of senior theses/project reports at OSU. Findings will be conveyed to broader audiences through ongoing outreach activities, such as the Smithsonian Institution?s Ocean Hall, where Duncan?s work on LIPs is included as a video ?interview?, and in popular journals such as Oceanography [Coffin et al., 2007].