The efficacy of kinematic indicators in a complexly deformed Mass Transport Deposit: Insights from the deepwater Taranaki Basin, New Zealand

AbstractThree-dimensional (3D) seismic data reveal the complex interplay between the surface topography of a c. 4405 km3 mass transport deposit (MTD) and overlying sedimentary packages over approximately the last two million years. The data image part of the Pleistocene to recent shelf to slope to basin-floor Giant Foresets Formation in offshore western New Zealand. The MTD created substantive topographic relief and rugosity at the contemporaneous seabed, formed by the presence of a shallow basal detachment surface, and very large (up to 200 m high) intact slide blocks, respectively. Sediments were initially deflected away from high-relief MTD topography and confined in low areas. With time, the MTD was progressively healed by a series of broadly offset-stacked and increasingly unconfined packages comprised of many channel bodies and their distributary complexes. Positive topography formed by the channels and their distributary complexes further modified the seafloor and influenced the location of subsequent sediment deposition. Channel sinuosity increased over time, interpreted as the result of topographic healing and reduced seafloor gradients. The rate of sediment supply is likely to have been non-uniform, reflecting tectonic pulses across the region. Sediments were routed into deep water via slope-confined channels that originated shortly before emplacement of the MTD.

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Tectonic and geomorphic controls on the distribution of submarine landslides across active and passive margins, eastern New Zealand

10.5194/egusphere-egu2020-3194 ◽

2020 ◽

Author(s):

Sally Watson ◽

Joshu Mountjoy ◽

Gareth Crutchley

Keyword(s):

New Zealand ◽

Mass Transport ◽

Submarine Landslide ◽

Sediment Supply ◽

Submarine Landslides ◽

Mass Wasting ◽

Active Margin ◽

Eastern Margin ◽

Marine Habitats ◽

Mass Transport Deposits

Submarine landslides occur on continental margins globally and can have devastating consequences for marine habitats, offshore infrastructure and coastal communities due to potential tsunamigenic consequences. Evaluation of the magnitude and distribution of submarine landslides is central to marine and coastal hazard planning. Despite this, there are few studies that comprehensively quantify the occurrence of submarine landslides on a margin-wide scale.&#160;We present the first margin-wide submarine landslide database along the eastern margin of New Zealand comprising >2200 landslide scars and associated mass-transport deposits. Analysis of submarine landslide distribution reveals 1) locations prone to mass-failure, 2) spatial patterns of landslide scale and occurrence, and 3) the potential preconditioning factors and triggers of mass wasting across different geologic settings.&#160;Submarine landslides are widespread on the eastern margin of New Zealand, occurring in water depths from ~300 m to ~4,000 m. Landslide scars and mass transport deposits are more prevalent, and on average larger, on the active margin, compared the passive margin. We attribute higher concentrations of landslides on the active margin to the prevalence of deforming thrust ridges, related to active margin processes including oversteepening, faulting and seamount subduction. Higher sediment supply on the northernmost active margin is also likely to be a key preconditioning factor resulting in the concentration of large landslides in this region.&#160;In general, submarine landslide scars are concentrated around canyon systems and close to canyon thalwegs. This suggests that not only does mass wasting play a major role in canyon evolution, but also that slope undercutting in canyons may be a fundamental preconditioning factor for slope failure.&#160;Results of this study offer unique insights into the spatial distribution, magnitude and morphology of submarine landslides across different geologic settings, providing a better understanding of the causative factors for mass wasting in New Zealand and around the world.&#160;

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Mass Transport Deposit (MTD) or Complex Channel System? A case study of the 3D Nimitz Seismic Survey, Taranaki Basin, New Zealand

Interpretation ◽

10.1190/int-2020-0034.1 ◽

2020 ◽

pp. 1-21

Author(s):

Roberto Clairmont ◽

Heather Bedle

Keyword(s):

New Zealand ◽

Mass Transport ◽

Large Scale ◽

Seismic Survey ◽

Mass Wasting ◽

Channel System ◽

System A ◽

Stratigraphic Architecture ◽

Complex Channel

The Taranaki Basin is well known for studies examining the seismic stratigraphy, depositional and erosional features, and tectonic frameworks linked to the New Zealand (NZ) continent. This particular study examines a “funny looking thing” (FLT) which we associate to be consistent with that of a braided channelized system. We observe this feature within the 3D Nimitz Survey (See Figure 1), located in the Northern Taranaki Basin (NTB) off the western continental coast of North Island, NZ. The FLT occurs within Quaternary deposits of the Whenuakura Formation which are interpreted to reflect shelfal topset sediments (O’Leary et al., 2010). It is underlain by the Giant Foresets Formation (GFF) of Pliocene to Pleistocene age, which are described as large-scale progradational and aggradational continental successions that migrated west to northwest in basinward direction (Anell and Midtkandal, 2017; Clairmont et al., 2020; Hansen and Kamp, 2002; Shumaker et al., 2017) (Figure 2). It comprises a shelf-to-slope succession of claystone to siltstone with argillaceous sandstone intervals defining an overall coarsening upward succession (O’Leary et al., 2010). The FLT within the Whenuakura Formation is characterized by chaotic facies in cross section, which shares characteristics with potential mass wasting events (Figure 3a). However, further analysis using seismic attributes improved the spatial and stratigraphic architecture of the FLT, which favored a complex channelized system interpretation over a mass transport deposit complex.

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