Consolidation patterns during initiation and evolution of a plate-boundary decollement zone: Northern Barbados accretionary prism

Moore, J. Casey; Klaus, A.; Bangs, N. L.; Bekins, Barbara A.; Bücker, C.; Brückmann, Warner; Erickson, Sierra; Hansen, O.; Horton, T. W.; Ireland, Peter; Major, Candace O.; Moore, G. F.; Peacock, Sheila; Saito, Saneatsu; Screaton, E.; Shimeld, John; Stauffer, Philip H.; Taymaz, Tuncay; Teas, Philip A.; Tokunaga, Tomochika

doi:10.1130/0091-7613(1998)026<0811:cpdiae>2.3.co;2

Cited by 76 publications

(9 citation statements)

References 20 publications

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“…[35] Assuming 100% water saturation the model predicts a range of porosity increase from 8.5-9% to 15.5-16.8% (i.e., depending on the degree of compaction for an average clay content of 0.33) to explain a Vp decrease from 4.3 km/s (background) to 3.6 km/s (within LVZ1) in sediments at 8 kmbsf and 2.5 km water depth (Figures 3c and 8c). The predicted magnitude of porosity increase is comparable to reported porosity increases for other margins (i.e., 30-60% porosity increases), inferred to be caused by undercompaction of subducting sediments (e.g., Barbados [Bangs et al, 1990;Westbrook, 1991;Moore et al, 1998;Hayward et al, 2003], Nankai [Hyndman et al, 1993;Screaton et al, 2002;Bangs et al, 2009;Tobin and Saffer, 2009], Ecuador [Calahorrano et al, 2008]).…”

Section: Low Velocity Zones-lvz1 and Lvz2supporting

confidence: 77%

“…Similar deep rooted vertical zones of seismic blanking associated with tectonically driven sediment deformation have been observed farther north along the Hikurangi margin and suggested to be preferred paths for focused fluid escape [Crutchley et al, 2011]. [41] We hypothesize that normal faults, underlying the stack of protothrusts at the base of the anticline and fractures at its flanks (Figure 6b), have facilitated depletion not only of pore water during compaction [Hyndman et al, 1993;Moore et al, 1998;Bangs et al, 1999;Screaton et al, 2002] but also gas from potential thermogenic accumulations in Cretaceous subducting sediments (section 5.4). These fluids have been accumulating at the crest of the anticline beneath the BSR (Figure 5).…”

Section: Fluid Migration Pathsmentioning

confidence: 56%

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Evolution of fluid expulsion and concentrated hydrate zones across the southern Hikurangi subduction margin, New Zealand: An analysis from depth migrated seismic data

Plaza‐Faverola¹,

Klaeschen²,

Barnes³

et al. 2012

Geochem Geophys Geosyst

111

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[1] Identification of methane sources controlling hydrate distribution and concentrations in continental margins remains a major challenge in gas hydrate research. Lack of deep fluid samples and high quality regional scale seismic reflection data may lead to underestimation of the significance of fluid escape from subducting and compacting sediments in the global inventory of methane reaching the hydrate zone, the water column and the atmosphere. The distribution of concentrated hydrate zones in relation to focused fluid flow across the southern Hikurangi subduction margin was investigated using high quality, long offset (10 km streamer), pre-stack depth migrated multichannel seismic data. Analysis of low P wave velocity zones, bright-reverse polarity reflections and dim-amplitude anomalies reveals pathways for gas escape and zones of gas accumulation. The study shows the structural and stratigraphic settings of three main areas of concentrated hydrates: (1) the Opouawe Bank, dominated by focused periodic fluid input along thrust faults sustaining dynamic hydrate concentrations and gas chimneys development; (2) the frontal anticline, with a basal set of protothrusts controlling permeability for fluids from deeply buried and subducted sediments sustaining hydrate concentrations at the crest of the anticline; and (3) the Hikurangi Channel, with buried sand dominated channels hosting significant amounts of gas beneath the base of the hydrate zone. In sand dominated channels gas injection into the hydrate zone favors highly concentrated hydrate accumulations. The evolution of fluid expulsion controlling hydrate formation offshore southern Hikurangi is described in stages during which different methane sources (in situ, buried and thermogenic) have been dominant.

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Section: Low Velocity Zones-lvz1 and Lvz2supporting

confidence: 77%

Section: Fluid Migration Pathsmentioning

confidence: 56%

Evolution of fluid expulsion and concentrated hydrate zones across the southern Hikurangi subduction margin, New Zealand: An analysis from depth migrated seismic data

Plaza‐Faverola¹,

Klaeschen²,

Barnes³

et al. 2012

Geochem Geophys Geosyst

111

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“…Décollement position is also influenced by the physical properties and lithologies of the trench sediments. Across the Barbados Ridge and Sumatra, seismic surveys and drilling deformation front show lithologic and physical property characteristics that lead to overpressures along weak layers within the incoming sediment conducive to seaward propagation of a continuous décollement (Dean et al, 2010; Deng & Underwood, 2001; Hüpers et al, 2017; Moore et al, 1998). In the Nankai trough, the décollement forms within with the deeper continuous sequences deposited seaward of the trench wedge and may be influenced more by lithology than high pore pressure (Kopf, 2013).…”

Section: Discussionmentioning

confidence: 99%

Basal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes

et al. 2020

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The south central Chilean margin regularly produces many of the world's largest earthquakes and tsunami, including the 2010 Mw 8.8 Maule and 1960 Mw 9.5 Valdivia events. In 2017, we acquired seismic reflection data along~1,000 km of the margin using the R/V Langseth's 15 km long receiver array and 108.2 l (6,600 in 3) seismic source to image structures associated with these ruptures. We focus on the Valdivia segment with the largest coseismic slip (~40 m). The outer 40 km of the forearc is an accretionary wedge constructed primarily of stacked sedimentary packages with irregular lengths and thicknesses and little along-strike continuity. Forearc structures indicate that the accretionary wedge grows primarily through basal accretion of the downgoing trench fill. The décollement propagates along a weak boundary near the top of the trench fill but occasionally branches downward into the underthrust sediment along bedding horizons, peeling off slices that are underplated to the forearc. The shallow décollement level and the rarity of underplating events allow most of the trench sediment to subduct. As a result, only~30% of the incoming sediment has been accreted since the Early Pliocene. This implies that, on average,~1 km of sediment must subduct beyond the outer forearc, an inference that is supported by our seismic images. We propose that the thickness and great downdip and along-strike extent of the underthrust layer, which separates the megathrust from the underlying roughness of the igneous ocean crust, ensures a smooth broad zone of strong coupling that generates the world's largest earthquakes and tsunami.

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“…The lower part of Unit IV (seismic Unit 8, Figure 2a), Unit V, and the top of Unit VI show similar characteristics to that developed at the locus for the formation of the future décollement at other subduction zones. In subduction zones, the décollement generally forms in overpressured fluid‐rich and highly porous clay‐rich zones correlated to high‐amplitude negative polarity seismic reflection (Bangs et al, 1999, 2004; Cochrane et al, 1994; Dean et al, 2010; Mikada et al, 2005; Moore et al, 1998; Moore & Shipley, 1993; Shipley et al, 1994) and/or freshening anomalies associated with bound water release (e.g., Bekins et al, 1995; Dutilleul et al, 2020; Henry, 1997; Henry & Bourlange, 2004; Spinelli et al, 2006). At Site U1520, geophysical and geochemical signatures including local elevated bound water content related to high smectite, zeolite, and opal content, high amplitude‐negative polarity seismic reflections (seismic Unit 9, Figure 2a) and freshening anomalies suggest that volcaniclastic Units V and VI are fluid‐rich.…”

Section: Discussionmentioning

confidence: 99%

Porosity, Pore Structure, and Fluid Distribution in the Sediments Entering the Northern Hikurangi Margin, New Zealand

et al. 2020

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Hosting both tsunami earthquakes and slow slip events at shallow depth, the northern Hikurangi margin has motivated strong research efforts over the last two decades to better understand the relation between fluid pressure and fault mechanical behavior. Recently, IODP Expeditions 372 and 375 drilled, cored, and logged the basin entering this subduction zone providing a unique opportunity to characterize initial hydrogeological and petrophysical properties that drive seismic hazards along the margin. We inventory bound and interstitial fluid contents and assess the compaction state of the heterogeneous incoming sequence by correcting shipboard total connected porosity from the bound water content that typically characterizes clay-rich sediments. By combining mercury injection capillary pressure, nuclear magnetic resonance, and nitrogen gas adsorption, we further document the evolution of pore structure with increasing depth. We also compare porosity data at the logging and sample scales. Both logging and laboratory data evidence contrasted porosity, pore structure, and fluid distribution across the entering section. Shallow macroporous siliciclastic units show very low bound water content and undergo compaction-induced dewatering as they are normally consolidated during burial. In contrast, mesoporous volcaniclastic Hikurangi Plateau facies are characterized by high potential for bound water release from smectite, zeolite, and opal dehydration at greater depths. They mostly exhibit very low permeability except potentially in uncemented highly porous intervals where the décollement may initiate. Macroporous to mesoporous pelagic carbonates sandwiched in between exhibit mixed behavior and may also host the future décollement, similarly to the southern part of the margin.

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Consolidation patterns during initiation and evolution of a plate-boundary decollement zone: Northern Barbados accretionary prism

Cited by 76 publications

References 20 publications

Evolution of fluid expulsion and concentrated hydrate zones across the southern Hikurangi subduction margin, New Zealand: An analysis from depth migrated seismic data

Evolution of fluid expulsion and concentrated hydrate zones across the southern Hikurangi subduction margin, New Zealand: An analysis from depth migrated seismic data

Basal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes

Porosity, Pore Structure, and Fluid Distribution in the Sediments Entering the Northern Hikurangi Margin, New Zealand

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