216 / 2022-03-09 00:27:24

Geomorphic variability of a submarine channel system located in a topographically complex area

submarine channel,mini-basins,mud-diapirs,geomorphological measurements,Niger Delta

Interpretation of seismic reflections collected mainly for hydrocarbon exploration over the past decades, provides new insights about turbidity channels driven by gravity-tectonic. Understanding the evolution of submarine channel systems on tectonically influenced slopes is challenging as these channels can illustrate wide ranges of responses to structures from setting to setting. Besides, the potential influence of depocenters’ pounded sediments remains poorly constrained. A detailed framework for interaction of submarine channel system with mud diapirs in the Niger Delta Offshore is presented. Integrated cross-sections and mapped seismic surfaces from a c. 1200 ms TWT thick interval imaged in 3D seismic reflections data are emerged about a channel segment that we informally named ‘Amaku Channel Levee System’ (ACLS). Detailed geomorphological measurements were done along c. 37 km along-channel including depth, incision depth, width, sinuosity, and sidewall reliefs for deciphering the temporal and spatial evolution of channel running at a topographically complex area. The results provide a direct measures of channel reliefs configuration and the subsequent variability of channel architecture, provide insight into the prospective influence of structural reliefs versus pre-channel depositional processes. The channel western sidewall reliefs (WSRs) are broadly higher along the setting, flanked by the fold expressions of mud-diapirs, drove a discrete channel internal migrations that seem to do not influence the development of width and sinuosity of the whole channel system. The channel eastern sidewall reliefs (ESRs), although having lower positions, supported the major channel migrations with width and sinuosity increases. Channel depths correlate with the WSR and seem to evolve under the influence of structural features such as folds, faults and pockmarks. One of the most important insight of this work concerns the evolution of the ACLS that shows a particular response to structural reliefs, as multiple channel-fold interaction types occur at the same place of the same system. Channel diversion at the contact with fold (Stage 1) is followed by channel blocking resulting prominent sand dispersions. Sand-rich channel crossing the reliefs with slight deflections ends southerly by a terminal lobe (Stage 2), and then a mud-rich channel by-pass upon structural relief dimmed at the downstream limb of the fold (Stage 3). There are some indications that the pre-channel sediment barriers are likely to have the primary order control of channel migration at the early stage of evolution. Since the channel flow hits on the levees of the neighbouring system (AMS), it is diverted in upward direction across the fold strike. Contrary to other submarine channels recorded in mini-basins being fully conditioned by the fringes of structural deformations, in the study area, the geomorphological evolution and migration patterns of channel are likely to be conditioned by the interplay of structural and depositional controls.