Modern carbonate mounds: porcupine drilling

Henriet, Jean‐Pierre; Kano, Akihiro; Malone, M.J.

doi:10.2204/iodp.sp.307.2005

Cited by 5 publications

(3 citation statements)

References 13 publications

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“…These measurements provide percent weight values for the amount of calcite found at each sample location with instrument uncertainties of ±1%. The small uncertainty (±1%) in calcium carbonate measurements generates only a tiny change (generally ≪1%) in rock physics model velocity results, and we therefore neglect this uncertainty [e.g., Henriet et al ., ]. With porosity, sediment density, and pore water density also constrained by measurements, we converted weight percent of calcium carbonate into bulk percent calcite for each measurement.…”

Section: Method: Deriving Pore Pressure From Rock Physics Modelsmentioning

confidence: 99%

Permeability and pressure measurements in Lesser Antilles submarine slides: Evidence for pressure‐driven slow‐slip failure

et al. 2015

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Recent studies hypothesize that some submarine slides fail via pressure‐driven slow‐slip deformation. To test this hypothesis, this study derives pore pressures in failed and adjacent unfailed deep marine sediments by integrating rock physics models, physical property measurements on recovered sediment core, and wireline logs. Two drill sites (U1394 and U1399) drilled through interpreted slide debris; a third (U1395) drilled into normal marine sediment. Near‐hydrostatic fluid pressure exists in sediments at site U1395. In contrast, results at both sites U1394 and U1399 indicate elevated pore fluid pressures in some sediment. We suggest that high pore pressure at the base of a submarine slide deposit at site U1394 results from slide shearing. High pore pressure exists throughout much of site U1399, and Mohr circle analysis suggests that only slight changes in the stress regime will trigger motion. Consolidation tests and permeability measurements indicate moderately low (~10−16–10−17 m2) permeability and overconsolidation in fine‐grained slide debris, implying that these sediments act as seals. Three mechanisms, in isolation or in combination, may produce the observed elevated pore fluid pressures at site U1399: (1) rapid sedimentation, (2) lateral fluid flow, and (3) shearing that causes sediments to contract, increasing pore pressure. Our preferred hypothesis is this third mechanism because it explains both elevated fluid pressure and sediment overconsolidation without requiring high sedimentation rates. Our combined analysis of subsurface pore pressures, drilling data, and regional seismic images indicates that slope failure offshore Martinique is perhaps an ongoing, creep‐like process where small stress changes trigger motion.

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Section: Method: Deriving Pore Pressure From Rock Physics Modelsmentioning

confidence: 99%

Permeability and pressure measurements in Lesser Antilles submarine slides: Evidence for pressure‐driven slow‐slip failure

et al. 2015

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“…covered by dense coral growth) or geologically (e.g. composed of soft sediments as a result of fluid escape) more ''active'' and be a potential site to study the relation between fluid migration and coral bank development (Henriet et al 1999). Based on the initial interpretation, The´re`se Mound was selected as a special target site to study the present processes involved in mound development in the EU 5th framework projects GEOMOUND, ECOMOUND and ACES.…”

Section: Introductionmentioning

confidence: 99%

Thérèse Mound: a case study of coral bank development in the Belgica Mound Province, Porcupine Seabight

Mol

Kozachenko

Wheeler

et al. 2005

Int J Earth Sci (Geol Rundsch)

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High-resolution seismic profiles, swath bathymetry, side-scan sonar data and video imageries are analysed in this detailed study of five carbonate mounds from the Belgica mound province with special emphasis on the well-surveyed The´re`se Mound. The selected mounds are located in the deepest part of the Belgica mound province at water depths of 950 m. Seismic data illustrate that the underlying geology is characterised by drift sedimentation in a general northerly flowing current regime. Sigmoidal sediment bodies create local slope breaks on the most recent local erosional surface, which act as the mound base. No preferential mound substratum is observed, neither is there any indication for deep geological controls on coral bank development. Seismic evidence suggests that the start-up of the coral bank development was shortly after a major erosional event of Late Pliocene-Quaternary age. The coral bank geometry has been clearly affected by the local topography of this erosional base and the prevailing current regime. The summits of the coral banks are relatively flat and the flanks are steepest on their upper slopes. Deposition of the encased drift sequence has been influenced by the coral bank topography. Sediment waves are formed besides the coral banks and are the most pronounced bedforms. These seabed structures are probably induced by bottom current up to 1 m/s. Large sediment waves are colonised by living corals and might represent the initial phase of coral bank development. The biological facies distribution of the coral banks illustrate a living coral cap on the summit and upper slope and a decline of living coral populations toward the lower flanks. The data suggest that the development of the coral banks in this area is clearly an interaction between biological growth processes and drift deposition both influenced by the local topography and current regime.

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“…However, the Neogene mounds are dissimilar to Paleozoic carbonate mounds in that they are composed of coldwater coral in a matrix of mixed siliciclastic and carbonate sediments. They also lack stromatactis structures or any evidence of submarine car-bonate cementation as is common in Paleozoic carbonate mounds (De Mol et al, 2002;Henriet et al, 2005;Gregg et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Data report: dolomite in Neogene sediments of the Belgica carbonate mound province, Porcupine Seabight, North Atlantic

Gregg¹,

Frank²

2009

Proceedings of the IODP

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Dolomite was observed, using petrography, X-ray diffraction (XRD), and scanning electron microscopy (SEM), in cored Neogene sediments from the Porcupine Seabight in the north Atlantic Ocean, Integrated Ocean Drilling Program Expedition 307 Sites U1316, U1317, and U1318, ~100 km off the west coast of Ireland. Trace amounts (<10% of total carbonate component) of dolomite were observed in Challenger Mound, a deep coldwater mixed silicaclastic-carbonate mud mound located in the Porcupine Seabight. Significant dolomitization (>50% of total carbonate component) was observed primarily in Miocene strata in submound and off-mound sediments.Petrographic examination of smear slides indicates that dolomite is composed of micrometer-to decimicron-sized, limpid, rhombic crystals. XRD analysis indicates that the dolomite is calcium rich and poorly ordered. SEM confirms light petrographic analysis of size and morphology of dolomite crystals, and electron microprobe analysis indicates that the dolomite is ferroan and displays distinct compositional zoning. Microbes and associated microbial filamentous structures were observed associated with dolomite crystals.Saturation indexes of carbonate minerals calculated for interstitial waters collected from the three sites are consistent with the petrographic and XRD observation of dolomite.

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Modern carbonate mounds: porcupine drilling

Cited by 5 publications

References 13 publications

Permeability and pressure measurements in Lesser Antilles submarine slides: Evidence for pressure‐driven slow‐slip failure

Permeability and pressure measurements in Lesser Antilles submarine slides: Evidence for pressure‐driven slow‐slip failure

Thérèse Mound: a case study of coral bank development in the Belgica Mound Province, Porcupine Seabight

Data report: dolomite in Neogene sediments of the Belgica carbonate mound province, Porcupine Seabight, North Atlantic

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