Composition of fine‐grained sediment in the Hikurangi Trough: Evidence for intermingling among axial gravity flows, transverse gravity flows and margin‐parallel ocean currents

Underwood, Michael B.

doi:10.1111/sed.13067

Cited by 3 publications

(1 citation statement)

References 305 publications

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“…1B). Most of the sediments lling the trench are <3.5 Ma 16 and comprise pelagic, turbidite, mass-transport, and contourite deposits 17 .…”

Section: Hikurangi Channel-levee Systemmentioning

confidence: 99%

When the levee breaks: the largest channel-wall collapse ever described

McArthur,

Tek,

Poyatos-Moré

et al. 2023

Preprint

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3D seismic reflection data from the Hikurangi trench-axial channel-levee system, offshore New Zealand, reveal the largest channel-wall failure yet described. Wholesale collapse of both channel banks along a 68 km stretch created a mass transport deposit (MTD) containing blocks up to 4 km long, with a preserved volume of 19 km3. Subsequent deposits have erosional contacts into the MTD, confirming that its original volume was even larger. Channel-walls typically collapse locally, yet synchronous failure of both channel flanks is documented here, implying a catastrophic external trigger. For most of its length, the MTD overlies deposits imaged as high-amplitude reflectors, representing the pre-failure channel floor. Locally these older channel deposits were excavated, transported across and down channel, and then deposited in imbricated stacks, such that the volume of displaced materials exceeded that of the initial failure. Metadata studies of other channel-wall derived MTDs confirm this to be the largest channel-wall collapse documented. MTDs initiated by large-scale levee-collapse like that documented here pose an under-appreciated risk to seafloor infrastructure both within channels and over regions extending at least twice the channel width into their overbank areas.

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“…1B). Most of the sediments lling the trench are <3.5 Ma 16 and comprise pelagic, turbidite, mass-transport, and contourite deposits 17 .…”

Section: Hikurangi Channel-levee Systemmentioning

confidence: 99%

When the levee breaks: the largest channel-wall collapse ever described

McArthur,

Tek,

Poyatos-Moré

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

Deep-ocean channel-wall collapse order of magnitude larger than any other documented

McArthur,

Tek,

Poyatos-Moré

et al. 2024

Commun Earth Environ

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Submarine channels are the largest conveyors of sediment on Earth, yet little is known about their stability in the deep-ocean. Here, 3D seismic data from the deep-ocean Hikurangi channel-levee system, offshore New Zealand, reveal the largest channel-wall failure yet documented. Collapse of both channel-walls along a 68 km stretch created a mass-transport deposit of 19 km3, containing 4 km long blocks. Channel-walls typically collapse piecemeal, but here synchronous failure of both channel-walls and landslide erosion of the seafloor is documented, requiring a new process model for channel-wall failure. Mass-failure on this scale poses an under-appreciated risk to seafloor infrastructure both within channels and over regions extending twice the channel width into their overbank. Hitherto, channel-wall failures of this size are unrecognised in abyssal plains; its scale changes our understanding of how channel-levee systems are constructed and how they conduct sediment, carbon and pollutants into the deep-ocean.

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Testing turbidite conceptual models with the Kaikōura Earthquake co-seismic event bed, Aotearoa New Zealand

Maier,

Strachan,

Tickle

et al. 2024

Journal of Sedimentary Research

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The 2016 Mw7.8 Kaikōura Earthquake in Aotearoa New Zealand provides an opportunity to test widely applied turbidite sedimentation models because it triggered a co-seismic turbidity current. The resultant Kaikōura event bed (KEB), interpreted as a turbidite, is sampled for approx. 1300-km down-flow along the depositional system. Sediment core lithologies, computed tomography (CT), and particle-size data are used to test event-bed thickness, silt content, facies distribution and stacking patterns against the foundations of the turbidite conceptual model of Bouma (1962). KEB thickness is variable to approx. 100 km down-flow distance and attains a maximum thickness at approx. 700 km down-flow distance before thinning distally, similar to the predicted bell-shaped proximal to distal trend. Silt content is high throughout the KEB from canyon to fan. The KEB is dominated by laminated Td facies and Te facies that evolve down-system from laminated, then graded, to homogenous muds. CT and granulometry data ar e key to differentiating subtle density and textural variations within fine-grained deposits and reveal that KEB Td and Te facies in the KEB that are often not preserved or readily observed in older deposits. The KEB highlights a fine-grained sedimentary system that contrasts with more widely studied sandy turbidite basins. In particular, the KEB example reveals that Td and Te facies are ubiquitous in this fine-grained, silt-rich system. A varied conceptual model developed from the KEB may be applicable to many modern deep-sea turbidite systems and crucial for understanding present-day particulate transport to the deep sea and interpreting evidence from the stratigraphic record.

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Composition of fine‐grained sediment in the Hikurangi Trough: Evidence for intermingling among axial gravity flows, transverse gravity flows and margin‐parallel ocean currents

Cited by 3 publications

References 305 publications

When the levee breaks: the largest channel-wall collapse ever described

When the levee breaks: the largest channel-wall collapse ever described

Deep-ocean channel-wall collapse order of magnitude larger than any other documented

Testing turbidite conceptual models with the Kaikōura Earthquake co-seismic event bed, Aotearoa New Zealand

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