Middlebury College, United States

Ocean Drilling Program Leg 155 drilled 34 holes at 17 sites on the Amazon deep-sea fan and recovered more than 4000 m of sediment from the various fan sub-environments. Eight sites focused on the sedimentary facies and depositional record of the most recently active channel-levee system from upper to lower fan. Three of these sites recovered continuous sections up to 100 m thick of aggrading sandy channel fills beneath the channel axis, as well as sandy lobe deposits from the lower fan. Seven sites penetrated as deep as 434 m and sampled older buried channel-levee systems and thick, interbedded muddy mass-transport units. Suites of wire-line logs, including FMS, run at eight sites reveal log motifs of various sedimentary facies and provide lithologies for intervals of non-recovery. Sites were located in well imaged channel, levee, mass flow environments both near-surface and subsurface, on the basis of multibeam bathymetry, GLORIA side-scan sonar imagery, and high-resolution 3.5 kHz, watergun and airgun records. The combined analysis of the sedimentary and log sequences with the acoustic profiles and site morphology allows for a detailed assessment of temporal and spatial changes in fan processes, and for the evolution of fan morphology, during the last 400,000 years.