The Relief of the Oceanic Basement and the Structure of the Front of the Accretionary Complex in the Region of Sites 541, 542, and 543

Mauffret, A.; Westbrook, G. K.; Truchan, M.; Ladd, John W.

doi:10.2973/dsdp.proc.78a.104.1984

Cited by 9 publications

(14 citation statements)

References 11 publications

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“…Although no bottom simulating reflector (BSR) has been identified on the seismic profiles in this trench area (the closest identified BSR is situated about 40 km landward on the wedge [Mauffret et al, 1984]…”

Section: Presence Of Hydrates: Implications For the Temperature Of Thmentioning

confidence: 96%

“…The entire zone between the mud volcano field at 13ø50'N and the large isolated mud volcano surveyed by Langseth et al [1990] at 14ø20'N is a basement high , Mauffret et al, 1984 bounded by major fracture zones, Mercurus to the south and Marathon to the north (Figure 3) [Collette and Roest, 1992]. The details of the basement topography in the mud volcano area were obtained from unpublished single-channel profiles from R/V Robert D. Conrad cruise 2907 (M. Langseth and G. K. Westbrook, personal communication, 1988) and from seismic multichannel lines Discovery 6 and 7 [Speed et al, 1984].…”

Section: Basement Topography Diapiric Mobilization and Wedge Decollementioning

confidence: 99%

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Fluid flow in and around a mud volcano field seaward of the Barbados accretionary wedge: Results from Manon cruise

Henry¹,

Pichon²,

Lallemant³

et al. 1996

J. Geophys. Res.

143

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A field of mud diapirs and mud volcanoes situated in the Barbados trench at 13°50′N and extending along an old oceanic fracture zone (Mercurus) was investigated during the Manon cruise using both surface ship and Nautile submersible sampling and measurements. The entire zone from 13°50′N up to 14°20′N has an anomalously high heat flow which implies that fluids are drained into it from a segment of the accretionary wedge a few hundred kilometers wide. Two structures interpreted as diatremes, Atalante and Cyclops, expell large amounts of water and methane. We propose that they were formed from the release of a light fluid when gas hydrates were dissociated in the sediment as the result of the circulation of warm fluid in the area. However they expell only a small fraction of the incoming fluid, implying that disperse flow is the dominant mode of expulsion in this area. The chemoautotrophic communities on the surface of the structures rely mostly on sulfides. Submersible observations, temperature measurements in the sediment, and the chemistry of the pore fluid indicate that convection of seawater occurs within the first few meters of sediment through high‐permeability channels, such as cemented carbonate conduits. We propose that this convection is driven by the density difference between the pore fluid and seawater, but fresh water released by the dissolution of shallow hydrates may also contribute. This shallow convection may be a frequent process in cold seep environments.

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Section: Presence Of Hydrates: Implications For the Temperature Of Thmentioning

confidence: 96%

Section: Basement Topography Diapiric Mobilization and Wedge Decollementioning

confidence: 99%

Fluid flow in and around a mud volcano field seaward of the Barbados accretionary wedge: Results from Manon cruise

Henry¹,

Pichon²,

Lallemant³

et al. 1996

J. Geophys. Res.

143

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“…Trends are computed by gridding the data in a larger area than shown in Figure 8, and using a 400-1an median filter over the observed data grids to define the trend (Figure 8c 8a and 8e). The Barracuda Ridge has a clear topographic expression (Figure 8b and 8f); the Tiburon Ridge is not easily defined topographically because of its proximity to the Barbados accretionary complex but appears as a distinct structural high in seistnic reflection profiles [Mauffret et al, 1984].…”

Section: Of the Noam-soam Plate Boundarymentioning

confidence: 99%

Deformation of the oceanic crust between the North American and South American Plates

Müller¹,

Smith²

1993

J. Geophys. Res.

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Fracture zone trends and magnetic anomalies in the Atlantic Ocean indicate that the North American plate must have moved with respect to the South American plate during the opening of the Atlantic. A comparison of plate tectonic flow lines with fracture zones identified from Geosat and Seasat altimeter data suggests that the North American‐South American plate boundary migrated northward from die Guinea‐Demarara shear margin to the Vema Fracture Zone before chron 34 (84 Ma), to north of the Doldrums Fracture Zone before chron 22 (51.9 Ma), and to north of the Mercurius Fracture Zone between chron 32 (72.5 Ma) and chron 13 (35.5 Ma). The paleoridge offset through time identified from magnetic anomalies and the computed cumulative strike slip motion in the plate boundary area, indicate that the triple junction may have been located between the Mercurius and the Fifteen‐Twenty fracture zones after 67 Ma (chron 30). Plate reconstructions indicate a Late Cretaceous phase of transtension, followed by transpression in the Tertiary for the Tiburon/Barracuda Ridge area south of the Fifteen‐Twenty Fracture Zone. The ocean floor in this area is characterized by a series of ridges and troughs with large Bouguer gravity anomalies (up to ∼135 mGal). We use smoothing spline estimation to invert Bouguer anomalies for crustal layer structure. Our model results suggest that the Moho is uplifted 2–4 km over short wavelengths (∼70 km) at the Barracuda and Tiburon ridges and imply large anelastic strains. The severely thinned crust at the two ridges implies that crustal extension must have taken place before they were uplifted. We propose that the North‐South American plate boundary migrated to the latitude of the Tiburon Ridge, bounded by the Vema and Marathon fracture zones, before chron 34 (84 Ma). Post‐chron 34 crustal thinning during a transtensional tectonic regime may have been localized at preexisting structural weaknesses such as the Vema, Marathon, Mercurius, and Fifteen‐Twenty fracture zone troughs, but reaching the Fifteen‐Twenty Fracture Zone and future Barracuda Ridge area only after chron 32 (72.5 Ma). This interpretation concurs with our crustal structural model, which shows stronger crustal thinning underneath the Tiburon Ridge than at the Barracuda Ridge. Subsequent transpression may have continued along the existing zones of weakness in the Tertiary, creating the presently observed crustal deformation and uplift of the Moho, accompanied by anelastic failure of the crust. Middle‐Eocene‐Upper Oligocene turbidites on the slope of the Tiburon Ridge, now located 800 m above the abyssal plain, suggest that most of its uplift occurred at post‐Oligocene times. The unusually shallow Moho underneath the Tiburon and Barracuda ridges represents an unstable density distribution, which may indicate that compressive stresses are still present to maintain these anomalies, and that the North American‐South American plate boundary may still be located in this area.

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“…Influence of the incoming oceanic basement has been documented as an important controlling factor in prism evolution: (1) prism growth is basically controlled by the amount of offscraped sediments (Mauffret et al 1984); (2) bending-induced grabens on the subducting plate can be important in tectonic erosion (Karig 1974;Hilde 1983); and (3) seamounts may cause indentations and intense deformation at the base of the prism slope (Lallemand & Le Accepted for publication 11 March 1992.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Nankai accretionary prism as revealed from IZANAGI sidescan imagery and multichannel seismic reflection profiling

Ashi

Taira

1992

Island Arc

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The Nankai accretionary prism, off southwest Japan represents one of the best developed clastic prisms in the world. A combination of swath mapping including Sea Beam and 'IZANAGI' sidescan sonar and closely spaced seismic reflection data was used to investigate the relationship between the progressive landward change in surface morphology and the internal structural evolution of the prism. The prism surface is divided into three zones sub-parallel to the trough axis on the basis of the IZANAGI backscattering image. The frontal part of the prism is characterized by several continuous lineaments that are approximately perpendicular to the plate convergence direction. These lineaments correspond to anticlinal ridges caused by active imbricate thrusting. Landward, these anticlinal ridges become progressively masked by fine-grained hemipelagic slope sediments that are constantly supplied to the entire prism slope. However, these overlying sediments show little deformation. This implies a change in deformation style from frontal thrusting with fault-bend folds to internal refolding of thrust sheets. In the middle to upper prism slope, the IZANAGI image shows numerous landslide features and large fault scarps, suggesting that exposed sediments are lithified enough to fail in brittle mode compared with the wet sediment deformation at the prism toe. Prism evolution is strongly affected by the decolkment depth which may be indirectly controlled by oceanic basement relief; a topographic embayment coincides with a regional minimum of sediment offscraping where a basement high has been subducted. The small tapered prism observed in the embayment may be due to lateral supply of overpressured pore fluids from the adjacent prism. Strain caused by the differential rate of prism growth across the basement relief forms faults trending at high angles to the trough axis.

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The Relief of the Oceanic Basement and the Structure of the Front of the Accretionary Complex in the Region of Sites 541, 542, and 543

Cited by 9 publications

References 11 publications

Fluid flow in and around a mud volcano field seaward of the Barbados accretionary wedge: Results from Manon cruise

Fluid flow in and around a mud volcano field seaward of the Barbados accretionary wedge: Results from Manon cruise

Deformation of the oceanic crust between the North American and South American Plates

Structure of the Nankai accretionary prism as revealed from IZANAGI sidescan imagery and multichannel seismic reflection profiling

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