Litho- and biofacies analysis of postglacial marine mud using CT-Scanning

Gagnoud, Marie; Lajeunesse, Patrick; Desrosiers, Gaston; Long, Bernard; Dufour, Suzanne C.; Labrie, Jacques; Mermillod‐Blondin, Florian; Stora, Georges

doi:10.1016/j.enggeo.2008.06.010

Cited by 15 publications

(7 citation statements)

References 7 publications

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“…Pictures of longitudinal sections were obtained in dicom format to be later analyzed by image J ® software. We analyzed the sedimentary structure of each core by using a tomogram representing tomographic intensities (TI) expressed in Hounsfield units (HU) along a longitudinal plane for the entire length of the core (Gagnoud et al 2009;Michaud et al 2003). The calibration gave specific values for tomographic intensities according to analyzed materials (i.e., TI air = -1000; TI water = 0; TI calcite = 2500).…”

Section: Data Processingsmentioning

confidence: 99%

Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles

et al. 2013

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International audienceThis study aims to investigate the role of spatial and temporal physical, biological and biogeochemical gradients on sediment biogeochemistry along a macrotidal and Si-rich estuary. Scanning and biogeochemical analyses were performed in the inner, mid and outer Aulne Estuary (France) at four seasons. The inner estuary shows high diagenetic activity linked to fluid mud dynamics and river loads. The highest authigenic phosphorus (Aut-P) concentrations ever found in the literature are observed in the inner estuary (18 µmol g-1 PS sediment). This is explained by a combination of favorable factors, i.e. the high organic matter and nutrient loads, the reductive conditions, the freshwater properties (low pH, OH-, sulfate and Mg2+ concentrations), the increase of particle residence time by the upward convergence of particles due to residual currents, and allochthonous riverine Aut-P. We suggest that the high Si(OH)4 concentrations (> 400 µM) may even increase Aut-P precipitation through the increase of Fe-P formation in these low salinity conditions. In the mid estuary, erosion-deposition dynamics dominate in point bars and lead to the succession of poor and rich organic and authigenic phosphorus layers, recording thus the seasonality of matter loads and its seasonal translocation from the inner estuary. In the outer estuary, deposition rates are high and constant and biogeochemical properties are characteristic of marine environments. The precipitation of Aut-P from free phosphate (PO43-) is lower than in the inner estuary and might be limited by higher Mg2+ concentrations in saline waters. This study highlights that small macrotidal estuaries, and especially their freshwater sediments, may constitute an important phosphorus sink through the precipitation of Aut-P. This precipitation could even be enhanced in fresh or brackish environments, thus increasing long term phosphorus storage and altering benthic fluxes of PO43- to the pelagic ecosystem

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Section: Data Processingsmentioning

confidence: 99%

Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles

et al. 2013

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“…In recent years, medical computed tomography (CT) scanners have become common in the nondestructive analysis of sediment cores [St-Onge et al, 2007], including high-resolution reconstructions of relative or calibrated density for paleoenvironmental interpretation [Boespflug et al, 1995;Ashi, 1997;Lis e-Pronovost et al, 2009;St-Onge and Long, 2009;Støren et al, 2010;Davies et al, 2011;Dorfman et al, 2015], assessment of coring deformation [Ashi, 1997;Barletta et al, 2010;Walczak et al, 2017], and variations in sedimentological structures or components [Michaud et al, 2003;Gagnoud et al, 2009;Goldfinger et al, 2013;Mena et al, 2015;Patton et al, 2015]. Medical CT scanners measure the attenuation of X-rays, a function of density and atomic number, and store these values in pixels as relative gray scale values or Hounsfield units (HU), achieving resolution around 0.5 3 0.5 3 0.5 mm [Hounsfield, 1973].…”

Section: Introductionmentioning

confidence: 99%

SedCT: MATLAB™ tools for standardized and quantitative processing of sediment core computed tomography (CT) data collected using a medical CT scanner

Reilly

Stoner

Wiest

2017

Geochem Geophys Geosyst

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Computed tomography (CT) of sediment cores allows for high‐resolution images, three‐dimensional volumes, and down core profiles. These quantitative data are generated through the attenuation of X‐rays, which are sensitive to sediment density and atomic number, and are stored in pixels as relative gray scale values or Hounsfield units (HU). We present a suite of MATLAB™ tools specifically designed for routine sediment core analysis as a means to standardize and better quantify the products of CT data collected on medical CT scanners. SedCT uses a graphical interface to process Digital Imaging and Communications in Medicine (DICOM) files, stitch overlapping scanned intervals, and create down core HU profiles in a manner robust to normal coring imperfections. Utilizing a random sampling technique, SedCT reduces data size and allows for quick processing on typical laptop computers. SedCTimage uses a graphical interface to create quality tiff files of CT slices that are scaled to a user‐defined HU range, preserving the quantitative nature of CT images and easily allowing for comparison between sediment cores with different HU means and variance. These tools are presented along with examples from lacustrine and marine sediment cores to highlight the robustness and quantitative nature of this method.

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“…Grain size was more variable within the Paspébiac cores, and St-Siméon cores contained a greater proportion of mud and a higher organic matter content, suggesting that low energy conditions, vegetation and riverine input enhance sedimentation of finer particles at St-Siméon (Renaud, 2000). Site-specific differences in corer penetration (and resulting core length) were likely due to the relative position of a layer of dense, postglacial marine mud (Gagnoud et al , 2009), reflecting differences in the intensity and frequency of accretionary and erosionary (storm or ice-related) events in these intertidal areas. Dense postglacial mud limits the penetration of organisms of the Macoma balthica community such as Alitta virens (Gagnoud et al , 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Site-specific differences in corer penetration (and resulting core length) were likely due to the relative position of a layer of dense, postglacial marine mud (Gagnoud et al , 2009), reflecting differences in the intensity and frequency of accretionary and erosionary (storm or ice-related) events in these intertidal areas. Dense postglacial mud limits the penetration of organisms of the Macoma balthica community such as Alitta virens (Gagnoud et al , 2009). It appears, therefore, that the relative thickness of habitable space in the upper sediment was greater at the Paspébiac site.…”

Section: Discussionmentioning

confidence: 99%

Spatial distribution of Alitta virens burrows in intertidal sediments studied by axial tomodensitometry

et al. 2013

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Relationships between sediment characteristics and the spatial organization of biogenic structures remain poorly understood, albeit important for characterizing bioturbation impacts and small-scale ecological patterns. Using axial tomodensitometry (CT-scan) and core sectioning, we studied the spatial distribution of Alitta virens burrows in sediment cores from two mudflats with different degrees of exposure along the St Lawrence Estuary, Canada. A variety of burrow morphologies was observed at both sites, with most being I-shaped. Most values measured (organic matter content, mean tomographic intensity, the number and diameter of burrow shafts and the percentage of space they occupy per transverse section) covaried with depth. The more sheltered site had higher organic matter and mud contents, and lower average tomographic intensity values. The spatial distribution of burrow shafts also differed between sites, with the more sheltered site having a higher number of burrow shafts and percentage of biogenic space in the upper sediment column, as well as a greater volume of biogenic structures that were connected to the surface (although intra-site variability was great). Along the horizontal plane and at various depths within sediments, burrow shafts were more randomly distributed at the exposed site, compared to a more even, maximal spacing at the sheltered site. In addition to finding differences in burrow organization at two spatial scales, we found significant correlations between tomographic intensity and (1) the number of burrow shafts, (2) biogenic space and (3) organic matter content. CT-scan data, including tomographic intensity, are useful for examining and comparing biogenic structures in sediment cores.

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Litho- and biofacies analysis of postglacial marine mud using CT-Scanning

Cited by 15 publications

References 7 publications

Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles

Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles

SedCT: MATLAB™ tools for standardized and quantitative processing of sediment core computed tomography (CT) data collected using a medical CT scanner

Spatial distribution of Alitta virens burrows in intertidal sediments studied by axial tomodensitometry

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