William G. Dickson1,
D. Bradford Macurda2
(1) Dickson International Geosciences (DIGs), Houston, TX
(2) The Energists, Houston, TX
Abstract: Recognition and analysis of a major tributary of the recent Congo Fan: Some Gully!
New data on the middle and outer Congo Fan provide instructive examples of the interplay between recent channel-levee sedimentation and restrictions and redirection caused by basinward migration of salt-induced gravity-glide folds. These folds have successively shifted the levee systems seaward. The competing factors of tectonic redirection, massive slides, lateral aggradation and bypass resulted in a complex of both restricted and unrestricted sedimentation for the fan deposits. The shallow depth, within 500 msec or 450m of the mudline, allows clear imaging, providing a Late Miocene-Holocene analogue for the newly discovered Oligo-Miocene reservoirs just to the south.
We describe a classic channel system connected to Gully "F" (of Droz et al, 1996), a northwest-trending branch of the main Congo Canyon. This "F" system is illuminated in a new, non-exclusive 2D seismic survey recorded for the Gabon Ultra-Deep Round. Most lines which are spaced roughly every 8 - 16km, exhibit gull-winged channel-levee complexes and one area has massive contourites. Several stacked cycles show extremes of reflectivity and dip patterns demonstrating a range of grain size and depositional environment over at least 2500 km2. The main channel systems have downcut into and reworked the previous channels as in the Indus Fan, but the thin distal wedges are clearly vertically separated. This previously unknown area provides several clues to help unravel the reservoir story in one of the world's great fan systems.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana