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Earth Systems and Cycles
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Trenches are natural places for sediment from continents or islands to collect. Additionally, by the time a plate enters a subduction zone, it may have as much as 500 to 1000 meters of sediment on top of it that accumulated as it drifted across the ocean basin. As subduction progresses, some sediment moves into the mantle with the subducting plate, along with subducted igneous and metamorphic rock of the oceanic lithosphere. Any sediment that does not subduct collects and forms a wedge of material, called an accretionary wedge, in the trench (Fig. 2.25).
Geodynamic map of Northeast Asia
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
A.I. Khanchuk, L.M. Parfenov, W.J. Nokleberg
The legend for the geodynamics map is subdivided into three groups: (1) terranes; (2) overlying and stitching formations; and (3) other notations. The terranes of Phanerozoic and Late Precambrian oregenic belts are subdivided into the following types: Cratonal terrane - a fragment of a craton formed by Early Precambrian crystalline rocks that may have a thin Late Precambrian and (or) Phanerozoic cover.Miogeocline terrane - a fragment of a miogeocline (passive continental margin), formed by thick shallow-water (shelf) sedimentary strata that formed on a thinned continental crust.Continental margin terrane - a fragment of continental slope and base, formed by distal turbidites and hemipelagic sediments that formed on a thinned continental or oceanic crust.Continental margin arc terrane - a fragment of a continental margin magmatic arc of Andean type, including calcareous-alkaline volcanic and (or) plutonic formations that lie unconformably on underlying folded strata or contained intrusions; it may also include forearc basin deposits of thick (kilometers), abyssal, shallow-water, and continental deposits that formed in front of a magmatic arc.Island arc terrane - a fragment of an island volcanic arc and possibly an adjacent forearc down-warp, containing volcanogenic, volcanogenic-sedimentary and intrusive rocks; various types of ophiolites may be present.Oceanic terrane - a fragment of MOR type oceanic crust obducted onto the continental crust; may also include fragments of submarine volcanic islands, guyots, etc.Accretionary wedge terrane A - a fragment of an accretionary wedge formed along a continental margin wedge or island magmatic arc; predominantly composed of turbidites, possibly with a small quantity of oceanic rocks.Accretionary wedge terrane B - a fragment of an accretionary wedge formed along continental margin or magmatic island arc; predominantly composed of oceanic rocks with subordinate turbidites.Continental margin turbidite terrane - a terrane made up of thick strata of flysch (turbidites) consisting of accumulations on a continental shelf or slope, or along a fan that formed along continental transform-plate boundary.
Understanding sedimentary systems and processes of the Hikurangi Subduction Margin; from Trench to Back-Arc. Volume 1
Published in New Zealand Journal of Geology and Geophysics, 2022
Lorna J. Strachan, Julien Bailleul, Kyle J. Bland, Alan R. Orpin, Adam D. McArthur
To the east of the sea-floor expression of the subduction deformation front, the Hikurangi Trough forms an elongate, trench-parallel depocentre infilled with gravity flow, contourite, and mass-wasting deposits (Lewis 1994; Lewis et al. 1998; Lewis and Barnes 1999; Lewis and Pantin 2002; Barnes et al. 2010; Bland et al. 2015; McArthur and Tek 2021; Tek et al. 2021, 2022; Figure 3). Moving westward, the upper (Australian) plate comprises a submerged subduction (accretionary) wedge (Lewis and Pettinga 1993), that incorporates (1) an outer accretionary prism close to the Hikurangi Trough, formed from accreted trench-fill sediments and overlain by Quaternary trench-slope basins (e.g. Davey et al. 1986; Lewis and Pettinga 1993; Collot et al. 1996; Barnes and Mercier de Lépinay 1997; Lewis et al. 1999), and (2) an inner imbricated wedge cored by pre-subduction rocks that have been deformed by Neogene–Quaternary folds and thrusts (Barnes et al. 2002; Bailleul et al. 2013; Barnes et al. 2010; Bland et al. 2015).
A multifaceted study of the offshore Titihaoa-1 drillhole and a Neogene accretionary slope basin, Hikurangi subduction margin
Published in New Zealand Journal of Geology and Geophysics, 2022
Angela G. Griffin, Kyle J. Bland, Hugh E. G. Morgans, Dominic P. Strogen
The active Hikurangi Subduction Margin, into which Titihaoa-1 was drilled, accommodates oblique convergence between oceanic crust of the Pacific Plate and continental crust of Australian Plate (Spörli 1980; Walcott 1984; Nicol et al. 2007). This oblique convergence is responsible for the Neogene–Quaternary growth of an accretionary wedge up to 200 km wide (Lewis and Pettinga 1993). We use the term ‘accretionary wedge’ sensu Lewis and Pettinga (1993) and Bailleul et al. (2007, 2013), who defined it as the entire deformed area located between the forearc basin to the west, and the subduction trench (Hikurangi trough) to the east. The accretionary wedge includes (1) an outer accretionary prism close to the trench (Figure 1), formed from accreted trench-fill sediments and overlain by active mainly Quaternary trench-slope basins (e.g. Davey et al. 1986; Lewis and Pettinga 1993; Collot et al. 1996; Barnes and Mercier de Lépinay 1997; Lewis et al. 1999), and (2) an inner imbricated wedge (Figures 1 and 2) cored by pre-subduction rocks that have been deformed by folds and thrusts (Barnes et al. 2002; Bailleul et al. 2007, 2013; Barnes et al. 2010; Bland et al. 2015). Small sedimentary basins within the inner imbricated wedge are often filled with thick successions of marine mudstone and flysch (e.g. Pettinga 1982; Lewis and Pettinga 1993; Bailleul et al. 2013; McArthur et al. 2019). Coastal and shelfal parts of the Wairarapa region – including the Titihaoa Sub-basin – overlie the uppermost parts of the inner subduction wedge (Figure 2), here composed primarily of a fining-upwards succession of late Early Cretaceous to Oligocene sedimentary rocks that predate the tectonism associated with the Hikurangi margin (Field et al. 1997; Lee and Begg 2002). These rocks are overlain by a series of variably deformed syn-subduction Miocene to Recent fault-controlled basins and shelfal strata. Whilst drilling the well, it was discovered that the late Neogene section was much thicker than prognosed, and therefore no strata older than middle Miocene were intersected (Biros et al. 1995).