Robinson, Amelia C.1, Isabel P. Montanez1, Peter J.
(1) University of California-Davis, Davis, CA
ABSTRACT: The Role of Organic Matter-Clay Mineral Assemblages on the Transportation and Sequestration of Organic Matter from Source to Marine Sink
Ocean anoxia events have been attributed to abrupt conditions where there is burial of organic-and clay-rich sediments during periods of water column anoxia. This, however, may not be the only environmental parameter required for preservation. Recent studies document the role clay minerals play in sequestration and long-term stability of organic matter. If OM is sorbed onto mineral surfaces, accessibility of the OM for remineralization by microbes may be limited. Sorption mechanisms, distinguished by relative bond strengths, factor into the reactivity, partitioning and stability of organic matter-clay mineral assemblages (OMCM). Nanoscale surface area relationships may control the availability of organic compounds for microbial degradation, timing of desorption of organic matter from clay surfaces, and reaction kinetics of hydrocarbon release and diagenetic transformations in the subsurface.
A three-fold empirical and experimental approach addresses the importance of different surface characteristics and loading conditions conducive to sorption in continental margins. Deep sea sediments, representing a range in mineral surface reactivity, are used to characterize OMCM. Sorption-desorption experiments, using amino acids, lignin and amino- or carboxyl-functionalized quantum dots (fluorescent tags) with clay mineral mixtures, provide insight into OMCM stability, surface coverage, loading capacity, and specifically the location, abundance and distribution of clay reactive sites responsible for sequestering amino- and carboxyl group-bearing organic compounds over a range of ambient fluid conditions. The results of these sorption studies at the nano-scale can be scaled up to issues of OM sequestration in continental margin deposits, and should ultimately provide constraints on the fate and transport of OC from source to sink.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.