SUBMARINE MORPHOLOGY OF THE EASTERN PART OF THE NIGER DELTA (GULF OF GUINEA)

The eastern part of the Niger delta and the Calabar valley were survey ed during the cruise GUINESS 1 on-board the N/O l'Atalante. A prelimin ary interpretation of the collected data (including Dual EM12 multibea m echo soundings, 3.5 Wiz and seismic profilings, and corings) indicat es strong differences between these two sedimentary systems: (1) the s urveyed part of the Niger delta shows a very irregular morphology cont rolled by active shale diapirism; (2) the Calabar valley is a broad an d smooth trough incised by a meandering channel that fed the Calabar d eep-sea fan; diapirism is absent in the valley. These two systems are separated by a high NE-STY trending scarp, representing the eastern fl ank of aligned diapirs. They result from distinct sedimentary processe s and evolved independently through time. The proximity of these two s ystems raises the question of the relationships that can link a sedime ntary body typically more representative of high sea-level stages (the Niger delta) and one generally attributed to low sea-level stages (th e Calabar valley).