Mechanisms and Rates of Preservation of Biogenic Remains in Continental Shelf and Slope Environments

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Mechanisms and Rates of Preservation of Biogenic Remains in Continental Shelf and Slope EnvironmentsKarla M. Parsons-HubbardOberlin CollegeEAR-0345618ABSTRACTThe Shelf and Slope Experimental Taphonomy Initiative (SSETI) is a long-term experiment studying the fate of organism remains on the sea floor. The fossilization potential of organisms that die at the sediment-water interface is poorly understood, particularly in deep offshore shelf and slope environments. The modern shelf and slope setting is a reasonable proxy for ancient epicontinental sea deposits and has only rarely been studied with respect to its fossilization potential. The SSETI experiment began in 1993 when molluscan remains, crustaceans, echinoids, and woody plant debris were deployed in mesh bags in 21 different EODs at 10 major sites on the continental shelf and slope of the Gulf of Mexico and Caribbean. Each site has multiple replicates for repeated sampling over the ensuing years to decades. The project proposed here is to recover experimental arrays that have been on the sea floor for 12 years. Collections of samples have been taken at targeted intervals (1 year, 2 years, 8 years) to document taphonomic rates and processes, and to determine whether different types of shell, wood, test, or cuticle respond differently to processes in the taphonomically active zone (TAZ) in different environments and over time. To answer these questions, repeated sampling of the remains must be accompanied by a detailed characterization of the TAZ. This is accomplished through porewater geochemical analysis using in situ micro-electrode sampling and through measurements of sediment oxygen demand. The goal of this work is to link the instantaneous chemical conditions in the TAZ to the long-term effects on shells residing at, or just below, the sediment-water interface. Results through year eight show a very tight correlation between the porewater geochemistry and dissolution of molluscan material. These findings are greatly advancing knowledge about the cycling of carbonate on the sea floor and has important applications to paleontology, paleoecology, and has direct implications for carbon budgets and climate modeling. In particular, the results of this work are critical to planners seeking to use the sea floor as a carbon sink.