The Active Margin Carbon Cycle: Influences of Climate and Tectonics in Variable Spatial and Temporal Records.

摘要

Active margins, found at the junction between continental and marine tectonic plates, are characterized by high sediment transport rates and a close proximity between terrestrial sediment source and marine burial. These factors allow active margins to be particularly effective in the burial of organic carbon, resulting in high fidelity records of the terrestrial and marine environment spanning millions of years. Differences through time in the quantity and type of organic carbon preserved provide information on the effect of climate changes and tectonic processes in active margins. Two active margin sites, the Waipaoa Sedimentary System in New Zealand and the Gulf of Alaska (Southern Margin) are used to investigate the impacts of sea level rise, glaciation, and tectonic uplift and transport over 10 ka and 10 Ma time spans. Biogeochemical measurements of stable isotope, lignin, n-alkane, and PAH content, as well as Rock-Eval 6 analysis, reveal that in active margin systems OC preservation is dominated by variability in climate and subsequent physical changes in the erosional and depositional history. The impact of long- and short-term climate variability is apparent in OC preservation and offshore transport contributes recalcitrant organic matter to subducting sediments. During subduction of organic carbon, specifically kerogen, pressure acts to counterbalance thermal degradation leading to interactions with the mantle and global carbon cycle.