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Alternative Models for the Hybrid Turbidite-Contourite Systems of the Tanzanian MarginNormal access

Author: P. Sansom
Event name: 81st EAGE Conference and Exhibition 2019
Session: Best of Petroleum Geoscience - Global Resource Development (In colloboration with the Geology Society of London)
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201900925
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 6.06Mb )
Price: € 20

Summary:
Seismically well-imaged hybrid turbidite-contourite deposits comprise the bulk of the Albian to Neogene slope succession on the East African margin offshore Tanzania. These systems are characterized by migrating channel-levee complexes, which have been interpreted to record, and be diagnostic of, the synchronous interaction of eastward, downslope flowing turbidity currents and northerly, along-slope flowing contour currents. This model proposed that flow stripping of the fine-grained suspended part of the turbulent flow by weak contour currents led to the formation of expanded levee-drifts on the northern (downstream) side of the channels, which prograded southwards (upstream), driving southwards migration of the turbidite channel axis. It was proposed that deposition of the deflected fine-grained suspended load by suspension fall-out onto the northern levee was the primary cause of southward levee progradation and dominated over tractional redistribution of sediment by bottom currents. However, other observations challenge this interpretation, and it is possible to envisage an alternative model where southward levee growth is attributed to dominant tractional sediment transport by southward flowing bottom currents. These conflicting models based on seismic observations and inferred depositional processes illustrate the need for better understanding of the dominant controls on these hybrid systems.


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