Terrigenous and marine lipids in Amazon Fan sediments: implications for sedimentological reconstructions

Abstract

Preliminary lipid analyses of Amazon Fan sediments focused on the general characteristics of bitumen compn. Of particular interest was the identification of distinct sedimentary facies on a mol. level. We investigated sediments from different fan environments (pelagic and hemipelagic sediments as well as active channel-levee sediments). On a qual. mol. level (i.e., types of compds. detected), bitumen compns. of different fan environments are very similar to each other. Relative differences in bitumen distribution in terms of marine vs. terrigenous origin appear to be significantly correlated with the diln. of the autochthonous signal by terrigenous detritus. These differences distinguish normal hemipelagic sediment (Site 942) from active channel-levee sediment (Site 940) of the Amazon Channel, where marine compds. represent a background signal. The range of the ratio of two distinct groups of lipids (i.e., terrigenous wax alcs. over plankton-derived fatty acids) corresponds very well to rough sedimentol. ests. of sediment accumulation rates, which vary, depending on location and sea level, by more than 2 orders of magnitude. We suggest that this approach can be utilized for a rough est. of the diln. of the autochthonous signal by terrigenous detritus in environments such as the Amazon Fan. [on SciFinder(R)]