FN Archimer Export Format
PT J
TI The Ogooue Fan (offshore Gabon): a modern example of deep-sea fan on a complex slope profile
BT 
AF Mignard, Salomé
   Mulder, Thierry
   Martinez, Philippe
   Garlan, Thierry
AS 1:1;2:1;3:1;4:2;
FF 1:;2:;3:;4:;
C1 UMR CNRS 5805 EPOC, University of Bordeaux, 33615 Pessac, France
   SHOM, Service hydrographique et océanographique de la marine, 29228 Brest, France
C2 UNIV BORDEAUX, FRANCE
   SHOM, FRANCE
IF 2.921
TC 4
UR https://archimer.ifremer.fr/doc/00503/61435/65154.pdf
   https://archimer.ifremer.fr/doc/00503/61435/65155.pdf
LA English
DT Article
CR MOCOSED 2010
   OPTIC CONGO 2
BO Pourquoi pas ?
   Beautemps-Beaupré
AB The effects of changes in slope gradient on deposition processes and architecture have been investigated in different deep-sea systems both in modern and ancient environments. However, the impact of subtle gradient changes (< 0.3∘) on sedimentary processes along deep-sea fans still needs to be clarified. The Ogooue Fan, located in the northeastern part of the Gulf of Guinea, extends over more than 550 km westwards of the Gabonese shelf and passes through the Cameroon volcanic line. Here, we present the first study of acoustic data (multibeam echosounder and 3.5 kHz, very high-resolution seismic data) and piston cores covering the deep-sea part of this West African system. This study documents the architecture and sedimentary facies distribution along the fan. Detailed mapping of near-seafloor seismic-reflection data reveals the influence of subtle slope gradient changes (< 0.2∘) along the fan morphology. The overall system corresponds to a well-developed deep-sea fan, fed by the Ogooue River sedimentary load, with tributary canyons, distributary channel–levee complexes and lobe elements. However, variations in the slope gradient due to inherited salt-related structures and the presence of several seamounts, including volcanic islands, result in a topographically complex slope profile including several ramps and steps. In particular, turbidity currents derived from the Gabonese shelf deposit cross several interconnected intra-slope basins located on the low gradient segments of the margin (< 0.3∘). On a higher gradient segment of the slope (0.6∘), a large mid-system valley developed connecting an intermediate sedimentary basin to the more distal lobe area. Distribution and thickness of turbidite sands is highly variable along the system. However, turbidite sands are preferentially deposited on the floor of the channel and the most proximal depositional areas. Core description indicates that the upper parts of the turbidity flows, mainly composed of fine-grained sediments, are found in the most distal depocenters. 
PY 2019
PD JUL
SO Solid Earth
SN 1869-9510
PU Copernicus GmbH
VL 10
IS 3
UT 000471886300001
BP 851
EP 869
DI 10.5194/se-10-851-2019
ID 61435
ER

EF