CLAY CONTENT, POROSITY AND VELOCITY OF AMAZON FAN SEDIMENTS DETERMINED FROM ODP-LEG-155 CORES AND WIRELINE LOGS

We characterize variations in velocity and porosity as a function of c lay content for different depositional units of the Amazon Fan (levees , sand-rich High-Amplitude Reflection Packets, or HARPs and mass-trans port deposits, or MTDs) using core and log data. Younger fan sediments , including both HARP and levee turbidites, show an increase in porosi ty and a decrease in velocity with increased clay content, a relations hip indicative of a matrix-supported regime. In contrast, older, more deeply buried overbank turbidites and MTDs, show opposite physical-pro perty trends, which are indicative of a framework-supported regime. Th e changing behavior of physical properties within various fan units re sults from a combination of the nature of clay distribution within the sediment caused by different depositional processes, and to changes i n sediment structure during early burial and diagenesis.