ORGANIC CARBON BURIAL

A schematic representation of the major inputs and feedbacks involved in the burial of organic carbon in marine sediments is shown in Figure 1 (from Sageman and Lyons, 2003). The major inputs include terrigenous detritus, such as material derived from weathering of continental crust or from volcanic sources, biogenic components (both organic matter and mineralized microskeletal remains) derived from primary photosynthetic production and heterotrophic processes on land and in the sea, and authigenic material precipitated at or near the sediment-water interface as a consequence of Eh-pH-controlled organic and inorganic reactions. Although these major inputs have been recognized for many years, the synthesis in Figure 1 is novel in that it integrates physical (sedimentologic and oceanographic) and biogeochemical processes, relates major inputs to proximate and broader paleoenvironmental controls, illustrates important linkages between causes and effects in the model (i.e., feedbacks), and, lastly, identifies and tracks key components of the major biogeochemical cycles (C, O, S, N, and P) involved in regulating conditions at the Earth's surface. Climate and plate tectonics are the master controlling factors for the system represented in Figure 1. Climate includes a complex set of phenomena (temperature, evaporation, precipitation, and wind) and interactions among the atmosphere, land surface, ocean surface, biosphere, and cryosphere that are driven largely by variations in the amount and distribution of incoming solar radiation. Tectonic processes, by contrast, can be simplified to two parameters. These are vertical uplift, which creates crustal source areas for weathering and erosion, and subsidence, which together with eustasy acts to control the accommodation space available for accumulation of sediments.