Megaclasts within mass-transport deposits: their origin, characteristics and effect on substrates and succeeding flows

2020 ◽  
Vol 500 (1) ◽  
pp. 515-530 ◽  
Author(s):  
Jefferson Nwoko ◽  
Ian Kane ◽  
Mads Huuse
Keyword(s):  
Mass Transport ◽  
Seismic Reflection ◽  
Radial Flow ◽  
Submarine Landslide ◽  
Submarine Landslides ◽  
3D Seismic ◽  
Seafloor Topography ◽  
Basal Surface ◽  
Mass Transport Deposits ◽  
Substrate Influence

AbstractMegaclasts transported within submarine landslides can erode the substrate, influence the flow that transports them and, if they form seafloor topography, can influence subsequent flows and their deposits. We document grooves up to 40 km long formed by megaclasts carried in submarine landslides that scoured tens of metres deep into the contemporaneous substrate of the deep-water Taranaki Basin, New Zealand. A 1925 km2 3D seismic reflection survey records six mass transport deposits (MTDs) interbedded with turbidites. Here, we focus on three MTDs, labelled A (oldest), B and C (youngest). MTD-A features megaclasts that internally have coherent parallel strata, and formed striations 4–15 km long and 2–3 km wide, with protruding megaclasts that are onlapped by younger sediments. The seafloor expression of these megaclasts partially obstructed the submarine landslide that created MTD-B. MTD-B contains megaclasts that incised through the rugose topography of the underlying MTD-A, and formed divergent grooves on the basal surface of MTD-B (8–40 km long and 200–250 m wide), which suggest radial flow expansion where flows exited topographic confinement. MTD-C features grooves 2–6 km long and 100–200 m wide that terminate at megaclasts and which internally are characterized of highly deformed reflectors surrounded by a chaotic matrix. This study directly links megaclasts to the grooves they form, and demonstrates that markedly different styles of scouring and resultant grooves can occur in closely related MTDs.

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

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

<p>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.</p><p> </p><p>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.</p><p> </p><p>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.</p><p> </p><p>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.</p><p> </p><p>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.</p><p> </p>

Shear margin moraine, mass transport deposits and soft beds revealed by high-resolution P-Cable three-dimensional seismic data in the Hoop area, Barents Sea

2018 ◽  
Vol 477 (1) ◽  
pp. 537-548 ◽  
Author(s):  
Benjamin Bellwald ◽  
Sverre Planke
Keyword(s):  
High Resolution ◽  
Mass Transport ◽  
Seismic Data ◽  
Slope Failure ◽  
Barents Sea ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
Shallow Subsurface ◽  
Mass Transport Deposits ◽  
Amplitude Reflection

AbstractHigh-resolution seismic data are powerful tools that can help the offshore industries to better understand the nature of the shallow subsurface and plan the development of vulnerable infrastructure. Submarine mass movements and shallow gas are among the most significant geohazards in petroleum prospecting areas. A variety of high-resolution geophysical datasets collected in the Barents Sea have significantly improved our knowledge of the shallow subsurface in recent decades. Here we use a c. 200 km2 high-resolution P-Cable 3D seismic cube from the Hoop area, SW Barents Sea, to study a 20–65 m thick glacial package between the seabed and the Upper Regional Unconformity (URU) horizons. Intra-glacial reflections, not visible in conventional seismic reflection data, are well imaged. These reflections have been mapped in detail to better understand the glacial deposits and to assess their impact on seabed installations. A shear margin moraine, mass transport deposits and thin soft beds are examples of distinct units only resolvable in the P-Cable 3D seismic data. The top of the shear margin moraine is characterized by a positive amplitude reflection incised by glacial ploughmarks. Sedimentary slide wedges and shear bands are characteristic sedimentary features of the moraine. A soft reflection locally draping the URU is interpreted as a coarser grained turbidite bed related to slope failure along the moraine. The bed is possibly filled with gas. Alternatively, this negative amplitude reflection represents a thin, soft bed above the URU. This study shows that P-Cable 3D data can be used successfully to identify and map the external and internal structures of ice stream shear margin moraines and that this knowledge is useful for site-survey investigations.

scholarly journals Channel incision into a submarine landslide: an exhumed Carboniferous example from the Paganzo Basin, San Juan, Argentina

2021 ◽  
Author(s):  
David Hodgson ◽  
Jeff Peakall ◽  
Charlotte Allen ◽  
Luz Gomis Cartesio ◽  
Juan Pablo Milana
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Submarine Landslide ◽  
Geological Mapping ◽  
Transport Systems ◽  
Submarine Landslides ◽  
Dispersal Patterns ◽  
Paganzo Basin ◽  
Mass Transport Deposits ◽  
Erosion Surface

Emplacement of submarine landslides, or mass transport deposits, can radically reshape the physiography of continental margins, and strongly influence subsequent sedimentary processes and dispersal patterns. The irregular relief they generate creates obstacles that force reorganisation of sediment transport systems. Subsurface and seabed examples show that channels can incise directly into submarine landslides. Here, we use high-resolution sedimentological analysis, geological mapping and photogrammetric modelling to document the evolution of two adjacent, and partially contemporaneous, sandstone-rich submarine channel-fills (NSB and SSB) that incised deeply (>75 m) with steep lateral margins (up to 70°) into a 200 m thick debrite. The stepped erosion surface mantled by clasts, ranging from gravels to cobbles, points to a period of downcutting and sediment bypass. A change to aggradation is marked by laterally-migrating sandstone-rich channel bodies that is coincident with prominent steps in the large-scale erosion surface. Two types of depositional terrace are documented on these steps: one overlying an entrenchment surface, and another located in a bend cut-off. Above a younger erosion surface, mapped in both NSB and SSB, is an abrupt change to partially-confined tabular sandstones with graded caps, interpreted as confined lobes. The lobes are characterised by a lack of compensational stacking and increasingly thick hybrid bed deposits, suggesting progradation of a lobe complex confined by the main erosion surface. The incision of adjacent and partially coeval channels into a thick submarine landslide, and sand-rich infill including development of partially confined lobes, reflects the complicated relationships between evolving relief and changes in sediment gravity flow character, which can only be investigated at outcrop. The absence of channel-fills in bounding strata, and the abrupt and temporary presence of coarse sediment infilling the channels, indicates that the submarine landslide emplacement reshaped sediment transport systems, and established conditions that effectively separated sand- from mud-dominated deposits.

scholarly journals Review of Submarine Landslides in the Eastern Indonesia Region

2019 ◽  
Vol 34 (2) ◽  
Author(s):  
Hananto Kurnio ◽  
Tommy Naibaho ◽  
Catur Purwanto
Keyword(s):  
Seismic Reflection ◽  
Submarine Landslide ◽  
Submarine Landslides ◽  
Seismic Reflection Data ◽  
Bathymetric Data ◽  
Eastern Indonesia ◽  
Reflection Data ◽  
Common Process ◽  
Historical Times ◽  
Active Volcanoes

his paper reviews submarine landslide potential in the eastern Indonesia by analyzing published and recently acquired bathymetric data and interpreting seismic reflection data. This review aims to study and invent hazards that might affect seafloor infrastructure construction such as optic cables, especially in the eastern Indonesia Region. The hazards were also recognized as source of tsunamis such as Palu Bay 2018 and Babi Island north of Flores Island in 1992. On the other hand, submarine landslide is a common process of basin fill sedimentation in the region. As blessed with many active volcanoes, it has 130 of total the world 400, Indonesia should aware of tsunami induced by volcanoes especially the ones closed to the sea. There are five active volcanoes frequently produce tsunami in historical times: Anak Krakatau, Sunda Strait; Makian, Maluku Province; Sangihe, Sulawesi; Teon and Nila, Banda Sea; and Iliwerung, Lembata Island, east Lesser Sunda Islands.Key words: submarine landslide, volcanic tsunami, seafloor infrastructure, eastern Indonesia Makalah ini menelaah potensi langsoran dasar laut di wilayah Timur Indonesia melalui analisis publikasi dan data batimetri yang baru diambil serta penafsiran data seismic refleksi. Tinjauan longsoran dasar laut dimaksudkan untuk mempelajari dan menginventarisasi bencana yang mungkin bisa mempengaruhi pembangunan infrastruktur dasar laut seperti halnya kabel optic, terutama di wilayah Timur Indonesia. Bencana tersebut telah dikenal sebagai sumber beberapa tsunami seperti Teluk Palu 2018 dan Pulau Babi utara Lombok di tahun 1992. Sebaliknya, longsoran dasar laut merupakan proses sedimentasi pengisian cekungan yang biasa terjadi di wilayah tersebut. Dikarunia akan gunungapi terbanyak di dunia, sebab memiliki 130 dari 400 dunia, Indonesia harus menyadari bahaya tsunami yang ditimbulkan oleh aktivitas gunungapi terutama yang dekat laut. Terdapat lima gunungapi aktif yang sering menghasilkan tsunami dalam sejarah: Anak Krakatau, Selat Sunda; Makian, Provinsi Maluku; Sangihe, Sulawesi; Teon dan Nila, Laut Banda; dan Iliwerung, Pulau Lembata, Nusa Tenggara Timur.Kata kunci: longsoran dasar laut, tsunami gunungapi, infrastruktur dasar laut, Wilayah Indonesia Timur

Late Cenozoic architecture of the St. Pierre Slope

2005 ◽  
Vol 42 (11) ◽  
pp. 1987-2000 ◽  
Author(s):  
David JW Piper ◽  
Adam WA Macdonald ◽  
Stephen Ingram ◽  
Graham L Williams ◽  
Curtis McCall
Keyword(s):  
Mass Transport ◽  
Seismic Reflection ◽  
Failure Surface ◽  
Late Cenozoic ◽  
Grand Banks ◽  
Age Model ◽  
Seismic Reflection Profiles ◽  
Mass Transport Deposits ◽  
Bermuda Rise ◽  
Upper Slope

The late Cenozoic seismic stratigraphy of the continental slope south of western Newfoundland is interpreted using new seismic reflection profiles. New Miocene–Pliocene biostratigraphic (palynology) age determinations on the Hermine E-94 well on the northwestern Grand Banks of Newfoundland are correlated to the study area. The Quaternary section of St. Pierre Slope is disrupted by numerous failure scarps and mass-transport deposits, but correlation from the mid- slope to the continental rise is achieved using major mass-transport deposits as markers. On the upper slope, stacked downslope-thinning wedges of acoustically incoherent sediment are interpreted as till deposits of mid- to late Pleistocene age. Sedi mentation rates in the youngest part of the succession are estimated from a 30 ka radiocarbon date 25 m below the horizon of the youngest till tongue, which is exposed on a 60 m deep failure surface. Extrapolation of sedimentation rates and comparison with dated sections on the J-Anomaly Ridge and Bermuda Rise provides a consistent interpreted age model for the till tongues that corresponds to marine isotope stages 2, 4, 6, 8, 10, and 12.

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