Sedimentary Facies Recovered from Amazon Fan During ODP Leg 155: III. Site-Specific Interpretation of Sedimentary Patterns and Fan Processes

R. D. Flood, C. Pirmez, P. L. Manley, and J. E. Damuth

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.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California