Smith Lecture - Eliel Anttila
Constraining the drivers of organic carbon burial in margin-proximal marine strata: a case study from the Miocene Monterey Formation, CA.
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Organic carbon burial is one of the principal pathways by which carbon is removed from the ocean-atmosphere system. On geological timescales, a majority of the global organic carbon burial flux is accommodated within margin-proximal marine basins. However, the factors that control the timing and tempo of organic carbon burial in marginal marine strata through time remain uncertain, and the dominant mechanisms of organic carbon preservation in ancient marine sediments are the subject of ongoing scientific debate. I use the Miocene Monterey Formation of central California as a natural laboratory to characterize and constrain the dominant drivers of organic carbon preservation and burial in ancient marginal marine strata. In this talk, I will present a radiometrically-constrained test of hypotheses linking organic carbon burial in circum-Pacific basins to Miocene climate change. Organic-rich intervals of the Monterey Formation have been previously proposed to be contemporaneous with globally-observed positive shifts in the stable carbon isotopic composition of mid-Miocene marine carbonates (the “Monterey Event”), motivating the hypothesis that the burial of isotopically-depleted organic carbon in the Monterey Formation and elsewhere in the Pacific drove global cooling during the Middle Miocene Climate Transition. A new age model for the Monterey Formation, constrained by U-Pb ages on zircons derived from volcanic ash beds intercalated within stratigraphic sections in the Santa Barbara Basin, reveals that peaks in organic carbon burial rate in the Monterey Formation do not coincide with the Monterey Event. Furthermore, total organic carbon content in Miocene strata of the Santa Barbara Basin is inversely covariant with sedimentation rate, while geochemical proxies for bulk sediment surface area exhibit a sedimentation-rate-dependent positive covariance with organic carbon abundance. Together, these data suggest that organic carbon burial in the Monterey Formation was controlled by sedimentation rate, which was in turn modulated by a combination of local tectonic drivers and eustasy. Thus, organic carbon burial in the Monterey Formation is better described as a response to, rather than a driver of, global climate.
Building: | 1100 North University Building |
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Event Type: | Lecture / Discussion |
Tags: | Lecture |
Source: | Happening @ Michigan from Earth and Environmental Sciences |