Early sedimentation and deformation in the <scp>K</scp>umano forearc basin linked with <scp>N</scp>ankai accretionary prism evolution, southwest <scp>J</scp>apan

Ramirez, S.G.; Gulick, Sean P. S.; Hayman, Nicholas W.

doi:10.1002/2014gc005643

Cited by 31 publications

(53 citation statements)

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“…Recently, Ramirez et al . [] pointed out for the Nankai wedge that stabilization due to the formation of the KFB could have led to deactivation of the ancient OOST underneath the KFB [ Tsuji et al ., , ; Boston et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…Reflection seismic and borehole data from accretionary margins have provided precise position and timing of internal deformation structures inside the accretionary wedges. For instance, seismic stratigraphy and borehole data from Nankai Trough, SW Japan, have revealed the existence of prominent OOST adjacent Kumano forearc basin (KFB) (referred to as the Megasplay Fault [ Park et al ., ]) and its temporal variation in fault activity [ Strasser et al ., ; Gulick et al ., ; Kimura et al ., ; Ramirez et al ., ; Boston et al ., ]. Recent attempts to reconstruct deformation history of the accretionary wedge adjacent to the KFB, using the stratigraphy of wedge‐top basins, have strongly corroborated control of sedimentation on wedge stabilization and temporal variation of the Megasplay Fault activity [ Hayman et al ., ; Moore et al ., ; Ramirez et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Impact of sedimentation on evolution of accretionary wedges: Insights from high-resolution thermomechanical modeling

et al. 2016

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Syntectonic sedimentation history is a potential cause of differentiated accretionary wedge structures along the subduction margin. Recent efforts to model the role of sedimentation on wedge evolution have highlighted the importance of spatiotemporal history of sedimentation on the evolution of the wedge. Moreover, reconstruction of deformation history of the accretionary wedges using reflection seismic and borehole data has further substantiated the impact of sedimentation on wedge evolution. We conduct several numerical experiments using a high‐resolution dynamic 2‐D thermomechanical plate subduction model to systematically investigate and quantify different effects of sedimentation on accretionary wedge evolution. Models with sedimentation suggest migration of deformation to parts of the wedge lying outside the sedimentation zone leading to emergence/reactivation of out‐of‐sequence thrusts (OOSTs). Frequency and length of new thrust sheets are correlated with sedimentation in the trench. Models undergo a transition period of ~1.5 Myr following the onset of sedimentation, after which they continue to grow under a new steady state. Stabilization of the wedge and increased load on the oceanic plate due to sedimentation create conditions in which smaller wedge‐top basins combine to form a large and flat forearc basin. Last but not the least, emergence of OOST in models of accretionary wedges undergoing sedimentation provides important insights in to evolution of potentially tsunamigenic OOSTs like the Megasplay Fault seaward of the Kumano forearc basin.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of sedimentation on evolution of accretionary wedges: Insights from high-resolution thermomechanical modeling

et al. 2016

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“…3), cores from gas-hydrate exploration wells document significant accumulation of sandy turbidites in braided channels and fans with ages as old as 2.4 Ma within the slope sediment section (Noguchi et al, 2011;Takano et al, 2013). Further details of the origin and evolution of the slope sediment unit are addressed by Ramirez et al (2015), who subdivided SS into three subunits.…”

Section: Tectono-stratigraphic Units Of Kumano Forearc Basinmentioning

confidence: 99%

Evolution of tectono-sedimentary systems in the Kumano Basin, Nankai Trough forearc

Moore

Boston

Strasser

et al. 2015

Marine and Petroleum Geology

135

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a b s t r a c tSedimentary deposits in the distal Kumano forearc basin of the Nankai accretionary margin off Kii Peninsula, Japan, have been imaged using three-dimensional (3D) seismic data. The seismic data, along with logging and core data from the Integrated Ocean Drilling Program (IODP) show that the unconformity between the accretionary prism and overlying forearc sediments is time-transgressive. The unconformity at Site C0002 separates 5 Ma prism rocks from 3.65 Ma basin deposits; at Site C0009 it separates 5.6 Ma prism from 3.8 Ma basin sediments. Acoustic reflections in the basal deposits are subparallel to the underlying accretionary prism; the acoustic facies varies in thickness from 50 to 750 m. The mudstone deposits and laterally equivalent turbidites are interpreted as lower trench-slope deposits. The condensed slope sediment (SS) section decreases in age from 3.5 to 1.5 Ma at Site C0002 to 1.5 e0.9 Ma at C0009.Acoustic sequences within the lower forearc basin (LFB) contain higher proportions of silt and sand turbidites and progressively onlap the SS unit along a low-angle discontinuity (KL) in a landward direction. Because of the landward onlap of the LFB unit, the oldest LFB strata at C0002 are older than 1.67 Ma, whereas those at C0009 are younger than~0.9 Ma. Thus, the amount of time missing or characterized by condensed sedimentation across the KL unconformity decreases in duration in the landward direction. The landward-onlapping sequences tilt progressively landward in response to regional uplift along an out-of-sequence thrust (OOST; mega-splay) fault. Regional tilting shifted the basin's depocenter progressively landward, expanding that part of the basin from~10 km in width to >30 km. The onset of sand-silt turbidite deposition in the distal basin began after more accommodation space was created by the uplift of the outer ridge along the splay fault at~1.9 Ma. Conversely, turbidites of the Upper Forearc Basin (UFB) progressively onlap LFB in a seaward direction. Furthermore, the respective thicknesses of the LFB and UFB units switch from the seaward side of the basin (C0002) farther landward (C0009): the LFB unit is > 800 m thick in the seaward region, whereas it is only 200e300 m thick in the landward region; the UFB unit is < 50 m thick in the seaward region, and up to 600 m thick in the landward region. Thus, Kumano Basin responded in both space and time to a complex interplay between tectonics and sedimentation. The stratigraphy records a balance between the effects of prism uplift along the basin's distal edge with the rerouting of channels and canyons along the basin's proximal edge.

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“…There have been significant fluctuations of sediment provenance and shifts in delivery pathways and rerouting since the basin's initiation [35][36][37][38]. A margin-wide assessment has shown that the submarine fans have transformed over time from a braided channel-dominated system to a small fan dominated system with shrinking, separated, small basins; to a trough fill turbidite system; to a channel-levee system [39][40][41]. These changes in depositional processes over time affect the spatio-temporal delivery of organic matter necessary for methane production as well as the distribution of potential reservoirs given that turbidites, ash layers, and channel fill sediments are most likely to host high concentrations of GH and free gas [42].…”

Section: Kumano Basin Evolutionmentioning

confidence: 99%

“…Gas-charged fluids are at least partially confined in stratigraphic traps under the cap of the anticlinal-shaped accreted sediments ( Figure 10) and within the intercalated synclinal-shaped sediments which corresponds to the ponded slope basins in the early stages of prism growth (Figures 4, 6 and 7) [41].…”

Section: Seismic Evidence For Gas and Gh Trapsmentioning

confidence: 99%

Gas-In-Place Estimate for Potential Gas Hydrate Concentrated Zone in the Kumano Basin, Nankai Trough Forearc, Japan

2017

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Methane hydrate concentrated zones (MHCZs) have become targets for energy exploration along continental margins worldwide. In 2013, exploratory drilling in the eastern Nankai Trough at Daini Atsumi Knoll confirmed that MHCZs tens of meters thick occur directly above bottom simulating reflections imaged in seismic data. This study uses 3-dimensional (3D) seismic and borehole data collected from the Kumano Basin offshore Japan to identify analogous MHCZs. Our survey region is located~100 km southwest of the Daini Atsumi Knoll, site of the first offshore gas hydrate production trial. Here we provide a detailed analysis of the gas hydrate system within our survey area of the Kumano forearc including: (1) the 3D spatial distribution of bottom simulating reflections; (2) a thickness map of potential MHCZs; and (3) a volumetric gas-in-place estimate for these MHCZs using constraints from our seismic interpretations as well as previously collected borehole data. There is evidence for two distinct zones of concentrated gas hydrate 10-90 m thick, and we estimate that the amount of gas-in-place potentially locked up in these MHCZs is 1.9-46.3 trillion cubic feet with a preferred estimate of 15.8 trillion cubic feet. Keywords: gas hydrates; Kumano Basin; bottom simulating reflections; methane hydrate exploration; 3D seismic interpretation; Nankai Trough IntroductionNatural gas hydrates (GH) are crystalline inclusion compounds that form within the pore space of marine sediments along continental margins worldwide. These hydrate deposits are stable at specific pressure-temperature relationships, host highly compressed gas molecules (most commonly methane), and are proposed to be the largest dynamic reservoir of organic carbon on this planet [1][2][3]. GHs have enticed global interest for several reasons including climate change and potential slope stability hazards, but primarily because these deposits could prove to be an unconventional energy resource [3,4]. At the exploration stage, it is important to develop systematic GH exploration methods that consider gas source, migration mechanisms into the hydrate stability field, zones of free gas, indicators of gas hydrate accumulation, and at least a first order volumetric gas-in-place estimate for apparent zones of concentrated hydrates [5,6].Seismic imaging is an important tool for identifying GH because both GH and free gas alter the physical properties of marine sediments, which will in turn affect the travel path and attenuation of the seismic wavelet [7][8][9]. Concentrated hydrate deposits tend to form at and just above the base of gas hydrate stability (BGHS). This results in a sharp contrast in mechanical properties at the phase boundary between GH saturated layers overlying a zone where free gas, water, and potentially non-cementing hydrate occupy the pore space [10]. This contrast in physical properties is expressed in seismic data as bottom simulating reflections (BSRs), and BSRs remain our strongest remotely sensed indicator to infer the presence of GH [11...

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Early sedimentation and deformation in the Kumano forearc basin linked with Nankai accretionary prism evolution, southwest Japan

Cited by 31 publications

References 55 publications

Impact of sedimentation on evolution of accretionary wedges: Insights from high-resolution thermomechanical modeling

Impact of sedimentation on evolution of accretionary wedges: Insights from high-resolution thermomechanical modeling

Evolution of tectono-sedimentary systems in the Kumano Basin, Nankai Trough forearc

Gas-In-Place Estimate for Potential Gas Hydrate Concentrated Zone in the Kumano Basin, Nankai Trough Forearc, Japan

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