Seismic Geomorphology and Evolution of Submarine Channels from the Angolan Continental Margin

Gee, M.J.R.; Gawthorpe, Rob L.; Bakke, Kristina; Friedmann, S. Julio

doi:10.2110/jsr.2007.042

Cited by 81 publications

(61 citation statements)

References 39 publications

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“…13a and b). Similar seismic facies have been previously documented and interpreted as slump and debris-flow deposits sourced from the valley walls (Mayall et al, 2006;Gee et al, 2007;Janocko et al, 2013). These slump deposits are observed in the first 8 km of Segment A.…”

Section: Variations In Valley Morphologysupporting

confidence: 82%

“…The valley is formed by lateral migration and vertical stacking of a single channel element (e.g. Samuel et al, 2003;Deptuck et al, 2003;Babonneau et al, 2004;Kolla, 2007;Janocko et al, 2013), and has a composite erosional surface consisting of a valley base and adjacent valley walls (erosional fairway sensu Deptuck et al, 2003;Catterall et al, 2010; master erosion/incision surface sensu Gee et al, 2007; channel-belt erosion surface sensu Kane and Hodgson, 2011; bounding erosion surface sensu Hansen et al, 2015) (Fig. 2e).…”

Section: Terminologymentioning

confidence: 99%

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Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Qin

Alves

Constantine

et al. 2016

Marine and Petroleum Geology

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Detailed morphological analyses of a Pleistocene-Holocene submarine channel system in terms of its hierarchical framework, were carried out using a 3D seismic volume from offshore Espírito Santo, SE Brazil. The channel morphology shows marked variations, with five segments (Segments a to e) being identified along its full length. For example, the cross-sectional area of the channel decreases by a factor of 70 from Segment a to Segment c, and is then followed by a nearly four-fold increase from Segment c to Segment d. The significant changes in channel morphology relate to temporal and spatial variations in flow volume within the channel. In the same channel system, the valley reveals three distinct segments (Segments A to C), with similar aspect ratios but marked variations in morphology along the valley distance. Valley morphological changes are chiefly affected by erosional processes. Segment B is characterised by the largest valley-base width, valley width, and cross-sectional area compared to the other two segments. Valley enlargement in Segment B results from relatively high degrees of lateral channel migration and associated cut bank erosion, leading to the widening of the valley, especially the valley base. In Segment C, the valley is characterised by inner bank erosion in the form of shallow-seated mass failures, which only enlarged the upper part of the valley wall. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. salt diapirs, tributaries, overbank collapse) in the development of channel systems. Hence, the morphological analyses developed in this work provide an effective tool for studying channels and valleys on continental slopes around the world.

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Section: Variations In Valley Morphologysupporting

confidence: 82%

Section: Terminologymentioning

confidence: 99%

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Qin

Alves

Constantine

et al. 2016

Marine and Petroleum Geology

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“…8B; Deptuck et al 2003Deptuck et al , 2008Gee et al 2007;Hodgson et al 2011;McHargue et al 2011;Sylvester et al 2011). The coarser-grained parts of these systems often form important hydrocarbon reservoirs.…”

Section: (D) Submarine Channels: Flow Dynamics and Deposit Architecturementioning

confidence: 99%

Key Future Directions For Research On Turbidity Currents and Their Deposits

Talling

Allin

Armitage

et al. 2015

Journal of Sedimentary Research

166

117

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Turbidity currents, and other types of submarine sediment density flow, redistribute more sediment across the surface of the Earth than any other sediment flow process, yet their sediment concentration has never been measured directly in the deep ocean. The deposits of these flows are of societal importance as imperfect records of past earthquakes and tsunamogenic landslides and as the reservoir rocks for many deep-water petroleum accumulations. Key future research directions on these flows and their deposits were identified at an informal workshop in September 2013. This contribution summarizes conclusions from that workshop, and engages the wider community in this debate. International efforts are needed for an initiative to monitor and understand a series of test sites where flows occur frequently, which needs coordination to optimize sharing of equipment and interpretation of data. Direct monitoring observations should be combined with cores and seismic data to link flow and deposit character, whilst experimental and numerical models play a key role in understanding field observations. Such an initiative may be timely and feasible, due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery. This is illustrated here by recently collected data from the Squamish River delta, Monterey Canyon, Congo Canyon, and offshore SE Taiwan. A series of other key topics are then highlighted. Theoretical considerations suggest that supercritical flows may often occur on gradients of greater than , 0.6u. Trains of up-slope-migrating bedforms have recently been mapped in a wide range of marine and freshwater settings. They may result from repeated hydraulic jumps in supercritical flows, and dense (greater than approximately 10% volume) near-bed layers may need to be invoked to explain transport of heavy (25 to 1,000 kg) blocks. Future work needs to understand how sediment is transported in these bedforms, the internal structure and preservation potential of their deposits, and their use in facies prediction. Turbulence damping may be widespread and commonplace in submarine sediment density flows, particularly as flows decelerate, because it can occur at low (, 0.1%) volume concentrations. This could have important implications for flow evolution and deposit geometries. Better quantitative constraints are needed on what controls flow capacity and competence, together with improved constraints on bed erosion and sediment resuspension. Recent advances in understanding dilute or mainly saline flows in submarine channels should be extended to explore how flow behavior changes as sediment concentrations increase. The petroleum industry requires predictive models of longer-term channel system behavior and resulting deposit architecture, and for these purposes it is important to distinguish between geomorphic and stratigraphic surfaces

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“…The presence of MTDs at the base of channel systems has been documented on both seismic (e.g., Deptuck et al 2003;Mayall et al 2006) and outcrop data (e.g., Macauley and Hubbard 2013;Bain and Hubbard 2016), leading some authors to suggest that seafloor roughness produced by mass-wasting processes can capture and accelerate turbidity flows, facilitating the formation of channels (e.g., Deptuck et al 2003;Gee et al 2007;Abdurrokhim and Ito 2013). In fact, flow-capture processes related to mass wastings have recently been documented in the Gulf of Mexico and the Nile Delta (e.g., Kertznus 2009;Kneller et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

Qin

Alves

Constantine

et al. 2017

Journal of Sedimentary Research

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ABSTRACT:A Pliocene-Quaternary submarine channel system, influenced by a localized mass wasting, is investigated in this work using high-resolution 3D seismic data from offshore Espírito Santo Basin, SE Brazil. Three abandoned channels, a channel belt and an mass-transport deposit (MTD) are recognized in the channel system within a confluence region confined by salt diapirs. In this confluence region, the cross-sectional area (CSA) of the channel system can be up to 1.2 km 2 , i.e., 4 to 10 times larger than CSA in other parts of the channel system. Such significant changes in the architecture and morphology of the channel system resulted from the interaction between mass-wasting processes and turbidity flows. We postulate that a basal erosional scar was created by mass-wasting processes and was filled with an MTD. This basal scar was then used as a preferential pathway for turbidity flows, which were captured by its headwall and lateral margins. The interpreted data shows that the captured turbidity flows greatly widened the basal scar, but caused only small modifications in scar height. Part of the MTD within the basal scar was removed downslope by turbidity flows, and was replaced by channel-fill deposits. This paper shows a flow-capture process occurred in a confluence region on continental slope. Basal scars can capture turbidity flows and facilitate flow channelization, which is a key process for submarine-channel initiation. The replacement of MTD by channel-fill deposits has profound implications for reservoir volumes and net-to-gross ratios in channel systems and partly depends on the turbidity-flows properties, such as their erosive ability and frequency. The more erosive and frequent flows are captured by the basal scar, the larger is the accommodation space created for succeeding sand-prone turbidites.

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Seismic Geomorphology and Evolution of Submarine Channels from the Angolan Continental Margin

Cited by 81 publications

References 39 publications

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): Scale comparison with other submarine channel systems

Key Future Directions For Research On Turbidity Currents and Their Deposits

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

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