A Multi-Disciplinary Amazon Shelf Sediment Study (AmasSeds)

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This project is a continuation of an earlier project that investigated the accumulation of fine-grained sediment on the continental shelf near the mouth of the Amazon River. The earliest research proved that sediment was actively accumulating, and later research identified the sedimentary processes controlling accumulation. This project will examine in detail the operation of the processes and how they affect the formation of sedimentary strata. This new research will be done as the Sedimentology and Stratigraphy portion of AmasSeds (A Multi-disciplinary Amazon Shelf SEDiment Study), which is a cooperative project between US and Brazilian scientists. The project involves collaboration of Physical, Chemical, Biological, and Geological Sciences. %%% The project will examine mechanisms of Holocene strata formation over a range of time and vertical-length scales. Time scales will be evaluated using several radiochemical techniques (Th-234,Pb-210, Cs-137, C-14) and length scales will be examined using a range of coring (box cores, kasten cores, piston cores, borings) and high-resolution seismic techniques (3.5-kHz system, lower-frequency system). Cooperation with the other groups of AmasSeds will provide much information about the sedimentary processes controlling strata formation, and the resulting stratigraphy will be characterized by a range of observational techniques (SEM, optical microscopy, x- radiography, seismic stratigraphy). The research derives importance from its evaluation of a major subaqueous delta, which is typical of the largest dispersal systems for fluvial sediment in the world. These large systems have a profound influence on modern oceans, and have a good potential for reaching the geological record. The study area is the continental shelf near the mouth of the Amazon River, where the previous research associated with this grant allows establishment and testing of advanced hypotheses regarding strata formation.