Marine Science Faculty Publications

High-Resolution Investigation of Event Driven Sedimentation: Northeastern Gulf of Mexico

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High-resolution stratigraphy, Short-lived radioisotopes, Geochronology, Event stratigraphy, Sedimentology, Gulf of Mexico

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A rapid sedimentation pulse in the northeast Gulf of Mexico, associated with the Deepwater Horizon blowout in 2010, provided a unique opportunity to investigate a depositional event in real time and at very high resolution. Sediment cores were collected annually (2010-2016) from four sites and sub-sampled at 2 mm resolution to identify and characterize the sedimentary signature, as well as geochronology and accumulation rates using excess Lead-210 (210Pbxs) and excess Thorium-234 (234Thxs). The “time-series” collection of sediment cores on an annual basis allowed for the identification of changes in sedimentation on monthly to annual time-scales, which define the depositional pulse (2010-2011), initial post-event sedimentary impact and response (2011-2012), and post-event stabilization and preservation (2013-2016). The 2010 depositional pulse was short-lived ( < 1 year) with 234Thxs inventories and mass accumulation rates (MARs) indicating higher sedimentation rates and an absence of bioturbation as compared to subsequent years. The initial post-event impact/response (2011-2012) exhibited lower 234Thxs inventories and MARs indicating lower sedimentation rates. The stabilization in sedimentation (2013-2016) was indicated by site-specific apparent increases in MARs that are not supported by increased 234Thxs inventories, reflecting the re-establishment of bioturbation. Initially, 210Pbxs was unable to detect the sedimentation pulse, but with subsequent sedimentation and burial, it begins to resolve the event after 3-5 years. The ability to resolve the sedimentation pulse and the following short-term response was possible due to the high-resolution sampling and analysis, unconventional methodologies, and utilization of high sedimentation rates.

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Anthropocene, v. 24, p. 40-50