Interplay of salt-influenced structural deformation and submarine channel evolution in the Campos Basin, offshore Brazil

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2017-08-10

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Ceyhan, Can

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The Campos Basin, located on the southeastern Brazil passive margin, is one of the most productive basins in the western South Atlantic. The development of many siliciclastic turbidite reservoirs in the southeastern Brazilian margin provided a great interest in submarine channel systems of the Campos Basin for hydrocarbon exploration purposes. Prior research highlights the variation of sediment supply, sea-level fluctuations and tectonic activity as the most critical controls on channel development within the Campos Basin. The Campos Basin is structurally complex as a result of salt movement, and it is an ideal setting in which to investigate the influences of structural deformation on channel evolution and architecture. I investigated the interaction between development of a post-Miocene submarine channel system and structural deformation related to salt tectonics by using structural and stratigraphic analysis of 3D seismic-reflection data, which covers an area of approximately 1750 km². I produced detailed maps and cross sections of the submarine channel system, and compared them to structural maps in order to interpret the control of structural deformation on evolution and architecture of the submarine channel system. I interpreted that a regionally mapped seismic-reflection horizon approximates the paleobathymetry at the time of channel formation and correlated with the trend of the channel system. The paleobathymetry mainly dictated the transport pathway of the submarine channel system, as channels within the system mainly stayed in salt-withdrawal basins and avoided salt-influenced structural highs. However, the submarine channel system was diverted to flow directly on the top of a salt diapir within the southeastern part of the study area, rather than staying within salt-withdrawal basins. I explained this anomaly by two uplift stages of the salt diapir. Aggradation smoothed out much of the paleobathymetry associated with the first growth stage of the salt diapir, and the salt-influenced structural high was not able to divert the submarine channel system. The basal surfaces of channels within the system are deformed as a result of the growth of the salt diapir, which suggests that the salt diapir became active again when the submarine channel system started to develop.

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