New High-Resolution Seismic Lines Across ODP 155 Sites and First Images and Coring of the Amazon Distal Lobes (Lobestory Project)

Bruno Savoye¹, Droz Laurence², Babonneau Nathalie², Bonnel Cédric¹, Jegou Isabelle¹, Cremer Michel³, Estrada Ferran⁴, and Carlos Pirmez^5
1 IFREMER, 29280 Plouzané, France
² Brest University,
³ Bordeaux1 University, France
⁴ Instituto de Ciencias del Mar, Spain
⁵ Shell International E&P Inc,

The surface of the Amazon fan is covered by a distributary network of meandering channels that has been mapped with GLORIA side-scan sonar (Damuth et al., 1988). They are bounded by high natural levees and are perched atop their own overbank deposits (Pirmez and Flood, 1995). In 1994, during ODP Leg 155, 17 sites were drilled. At several sites, the uppermost ~100 m of the succession was cored several times with the advanced piston corer to ensure sufficient sediment for detailed sedimentary studies. However, seismic lines across across the ODP sites were average in quality. Their resolution was not sufficient for a detailed correlation with ODP cores.

In mud-dominated submarine fans, the nature and distribution of sandy deposits are critical for oil companies and also to understanding the sedimentary dynamics of fan development, in particular the initiation, growth, and abandonment of channel-levee systems but also understanding the sediment spreading in distal lobes. Channel patterns similar to those of the Amazon Fan are seen on other mud-rich fans, which have been acoustically imaged to varying degrees of detail. However, sampling of the fan sediments generally has been limited to the upper 10 m, and the lithofacies and/or sedimentary processes associated with the acoustic units observed on seismic reflection data are mostly conjectural.

During the Lobestory cruise, we used a new multichannel HR seismic streamer to collect high resolution seismic lines across the ODP sites and explored the distal part of the most recent Amazon turbidite system, which was unmapped and unknown.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005