32. RECORD OF TERRESTRIAL ORGANIC MATTER COMPOSITION IN AMAZON FAN SEDIMENTS1Miguel A. Goņi2 |
ABSTRACTElemental, stable carbon isotope, and lignin analyses were carried out to characterize the organic matter in sediments from Site 932 on the Amazon Fan. The lignin compositions of sedimentary organic matter in Subunits IIA and IIB at this site resembled those of fine- and coarse-suspended particles from the present-day Amazon River. The lignin concentrations and isotopic composition of organic carbon suggest that the organic matter in Subunit IIA sediments is composed of varying amounts of marine (85% to 20%) and terrestrial (15% to 80%) contributions, whereas in Subunit IIB, it is exclusively terrestrial in origin. The compositions of lignin phenols indicate that the vegetation of the Amazon Basin did not change appreciably during the period represented by the sediments in Site 932. The data also illustrate the depositional differences that were responsible for the formation of the various lithologic units at the site. |
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