Sedimentology and Stratigraphy of the Amazon Continental Shelf

Abstract

THE GENERAL objective of this portion of AmasSeds (A Multidisciplinary Amazon Shelf SEDiment Study) is to understand how evidence of environmental processes influencing the Amazon shelf is preserved in the underlying sedimen-tary strata. Unfortunately, strata are imperfect recorders of environmental events. In oceanic settings near large sediment sources, net accumulation of sediment may occur; however, in a physically dynamic setting, the preserved strata may contain numerous breaks of non-deposition or erosion. A fundamental question concerns what environmental interpretations are possible from sedimentary sequences which are punctuated by missing strata. This question assumes additional importance when a setting, such as the Amazon shelf, records the history for much of a continent and an equatorial ocean. In order to meet the general objective and to build on existing knowledge, several specific objectives are being undertaken by this project. The first is to identify the dominant processes (e.g., tidal currents, fiver discharge, bioturbation) controlling strata formation on different time and vertical-length scales. These scales range from hours to millenia and from microns to tens of meters. Secondly, the project is attempting to determine how the oceanic processes operate on sediment (rework, sort, bury) to emplace char