Distribution and origin of hybrid beds in sand-rich submarine fans of the Tanqua depocentre, Karoo Basin, South Africa

Hodgson, David M.

doi:10.1016/j.marpetgeo.2009.02.011

Cited by 176 publications

(281 citation statements)

References 34 publications

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“…Hybrid event beds (Haughton et al, 2003(Haughton et al, , 2009) are most commonly identified toward the bases and fringes of lobe deposits (e.g., Hodgson, 2009;Talling, 2013). However, they can form in any environment where mud and mudstone clasts are entrained into the turbulent flow, damping turbulence, and developing high-concentration to pseudo-laminar flow conditions (e.g., Ito, 2008;Haughton et al, 2003;Talling et al, 2004;Baas et al, 2011;Pierce et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

et al. 2018

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The effects of abrupt changes in slope angle and orientation on turbidity current behavior have been investigated in numerous physical and numerical experiments and examined in outcrop, subsurface, and modern systems. However, the long-term impact of subtle and evolving seabed topography on the stratigraphic architecture of deep-water systems requires fine-scale observations and extensive 3-D constraints. This study focuses on the Permian Laingsburg and Fort Brown formations, where multiple large sand-rich systems (Units A-F) have been mapped from entrenched slope valleys, through channel-levee systems, to basin-floor lobe complexes over a 2500 km 2 area. Here, we investigate three thinner (typically <5 m in thickness) and less extensive sand-rich packages, Units A/B, B/C, and D/E, between the large-scale systems. Typically, these sand-rich units are sharp-based and topped, and contain scours and mudstone clast conglomerates that indicate deposition from high-energy turbidity currents. The mapped thickness and facies distribution suggest a lobate form. These distinctive units were deposited in similar spatial positions within the basin-fill and suggest similar accommodation patterns on the slope and basin floor prior to the larger systems (B, C, and E). Stratigraphically, these thin units represent the first sand deposition following major periods of shut-down in sediment supply, and are interpreted as marking a partial re-establishment of sand delivery pathways creating "disconnected lobes" that are fed mainly by flows sourced from failures on the shelf and upper slope rather than major feeder channel-levee systems.Thickness and facies patterns throughout the deep-water stratigraphy suggest seabed topography was present early in the basin formation and maintained persistently in a similar area to ultimately form a stepped slope profile. The stepped slope profile evolved through three key stages of development: Phase 1, where sediment supply exceeds deformation rate (likely caused by differential subsidence); Phase 2, where sediment supply is on average equal to deformation rate; and Phase 3, where deformation rate outpaces sediment supply. This study demonstrates that smaller systems are a sensitive record of evolving seabed topography and they can consequently be used to recreate more accurate paleotopographic profiles.

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Section: Discussionmentioning

confidence: 99%

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

et al. 2018

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“…Turbulence damping and subsequent collapse, and associated sediment settling into denser nonNewtonian near-bed layers within the flow (Fig. 7A), may explain the widespread occurrence of debris flow deposits in the relatively distal parts of hybrid beds (Ito 2008;Haughton et al 2009;Hodgson 2009;Talling 2013), although these debris flows can themselves sometimes be far travelled on low gradients.…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

Key Future Directions For Research On Turbidity Currents and Their Deposits

Talling

Allin

Armitage

et al. 2015

Journal of Sedimentary Research

165

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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“…Basin-floor lobes generally comprise three deposit types: turbidites, hybrid beds and debrites 45 (Talling et al, 2004;Hodgson, 2009;Etienne et al, 2012). Hybrid beds comprise a division 46 that was deposited by a turbulent flow and a division that was deposited by a debritic flow and have been recognized as an important part of the rock record in lobe deposits (e.g.…”

Section: Introduction 43 44mentioning

confidence: 99%

Autogenic controls on hybrid bed distribution in submarine lobe complexes

Spychala

Hodgson

Lee

2017

Marine and Petroleum Geology

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Distribution and origin of hybrid beds in sand-rich submarine fans of the Tanqua depocentre, Karoo Basin, South Africa

Cited by 176 publications

References 34 publications

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

Key Future Directions For Research On Turbidity Currents and Their Deposits

Autogenic controls on hybrid bed distribution in submarine lobe complexes

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