| Preservation of organic matter in marine sediments is an important component of the global carbon cycle by being a sink of carbon over geological time scales. Organic matter buried in marine sediments is also directly proportional to the concentration of oxygen in the atmosphere. The factors controlling the preservation are poorly understood. The primary goal of this dissertation is to develop and apply a new approach to investigate preservation of organic matter in marine sediments.; The main findings are that there are multiple preservation mechanisms involved and their relative importance varies depending on depositional regime. Physical protection of organic matter in aggregates of organic matter and mineral particles and by sorption to mineral grains dominate on the continental shelf and upper slope where the majority of all organic matter is preserved in the ocean. Organic debris, preserved due to inherent resistance or encapsulation within organic matrices, dominates in oxygen deficient sediments where approximately 5% of organic matter is preserved. At deep sites (>2000 m), where another ∼5% of organic matter is preserved, most of the organic matter is physically protected by sorption to mineral surfaces or within diatom debris. Laboratory incubations of particulate phytoplankton-derived organic matter and clay particles demonstrate that organic-mineral aggregation can physically protect organic materials from degradation. |
