Geological controls on the evolution of submarine channels in the Espírito Santo Basin, SE Brazil

• Main Author: Qin, Yongpeng
• Published: Cardiff University 2017
• Subjects: 551.46; QE Geology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723585

Submarine channels are conduits that transfer sediment from continental shelves to the deep sea. They can form important hydrocarbon reservoirs when filled with sand-prone deposits and are, consequently, one of the most important hydrocarbon prospects on continental margins around the world. In this thesis, a 3D seismic volume from offshore Espírito Santo (SE Brazil) was used to analyse submarine channel systems near the modern sea floor. The aim of the thesis was to investigate the key controlling factors on variations in the morphology and architecture of submarine channel systems, at the same time, providing an analogue for modern and ancient depositional systems on continental slopes around the world. This work shows significant variations in morphology and architectures along the investigated submarine channel systems. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. mass-wasting events, tributaries, substrate lithology and salt tectonics) in the development of channel systems. It also records in great detail the nature of the interaction between mass-transport deposits and turbidity currents at the early stages of channel evolution. Basal scars created by mass-wasting events can capture turbidity currents and facilitate flow channelisation, which is a key process for submarine-channel initiation. In addition, the replacement of MTDs by channel-fill deposits has profound implications for reservoir volumes and net-to-gross ratios in channel systems. Spatial variations in channel sinuosity observed in this work are interpreted as reflecting substrate erodibility beneath the channel system. Submarine channels will show higher sinuosity when encountering resistant substrates, and lower sinuosity when the substrate is more erodible. Temporal changes in channel sinuosity resulted from enhanced sediment discharge from tributaries. This work stresses the role of lateral channel migration as an important mechanism responding to factors such as sediment supply and ultimately, controlling the evolution of submarine channel systems.