4th International Submarine Canyon Symposium (INCISE2018)

5-7 November 2018, Shenzhen, CHINA

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This is the detail of Structural controls on Submarine channel evolution and Architecture, Offshore Western Niger Delta.

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Author
Ashiru Olusola Raheemat
Co-Author(s)
Wu Shiguo
Abstarct Title
Structural controls on Submarine channel evolution and Architecture, Offshore Western Niger Delta.
Abstarct Body
Axial channel deposits of low- high amplitude reflections were studied from 3D seismic profile from offshore Niger Delta. Four laterally offset channel forms were identified having U, V, and intermediate motifs. They are named BC1- BC4 respectively. BC3 channel was studied for the structural influence on channel form architecture. Four phases of channel evolution were recognized in BC3 H1, H2-H4. H4 has the highest sinuosity value of 1.9, H1 has the lowest sinuosity value of 1.06. 3 ridges with mud volcanoes (two actives, one dormant) were also identified and their influence on the evolution of BC3 showed a positive influence on the channel form architecture. Areas overlying ridge showed higher lateral offset and higher sinuosity than other parts. Seafloor gradient and channel thalweg profiles showed even distribution away from the ridges. Transform fault leading to a horst and graben structure as seen at UC11 horizon (about 1600 m/s, Upper Miocene) are locally responsible for avulsion of BC3, a development that influences BC3 evolution up till the Pliocene. Channel fill architecture for BC3 as compared with an adjacent channel (a different study) reveals close similarity with the exception of uneven inner levee growth, varying degree of inner levee amalgamation across the length of BC3. In addition, the thickness of the abandonment drape is nearly uniform in BC3 but thinly veils/ mimics channel fills in the adjacent channel. Localized growth fault is resultant of the mud diapirs. These faults influence channel gradient and channel thalweg profile. The presence of the mud diapir ridges influence localized channel floor gradient and invariably sinuosity. Other structures such as localized faulting have contributed to gradient changes along channel profile causing ponding in some parts and channel floor elevation in other areas. The mud volcanoes could have also contributed to the number of fines in the channel, increasing channel fill sediment and preserving leveed structures. This could have contributed to the abnormally thick channel abandonment drape as seen in BC3.
INCISE Theme
Session 1: Canyon processes in space and time (formation, evolution, circulation)
Presentation Type
Oral Presentation
Keywords
submarine channel, avulsion, Mud diapir, growth fault, offshore, Niger Delta.

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