X-Radiography of Unextruded Sediment Cores

Axelsson, Valter; Händel, S. K.

doi:10.1080/04353676.1972.11879854

Cited by 13 publications

(4 citation statements)

References 4 publications

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“…Axial tomography of intact sediment cores X-radiography of sediments was first performed several decades ago (e.g. Hamblin, 1962;Calvert and Veevers, 1962;Axelsson and Händel, 1972). Using this technique with thin aquaria, animal burrows have been studied (e.g.…”

Section: Sub-mm Life Positions Of Benthic Biota Using the Fluorescentmentioning

confidence: 99%

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Stockdale

Davison

Zhang

2009

Earth-Science Reviews

221

147

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The hypothesis that reducing conditions exist in localized zones of high organic matter, termed microniches, was first suggested over a century ago, but only relatively recently have high-resolution techniques been available to investigate them. In any sediment containing benthic fauna, bioturbation affects the distribution of a number of redox-sensitive components. Direct faecal deposition and the death of fauna may be expected to cause particles of labile organic matter (microniches) to be distributed heterogeneously within the sediment. This review discusses the significance and future direction of microniche studies by considering, exclusively, data obtained on a sub-mm scale that provide significant evidence for the existence and properties of microniches. Microelectrodes and planar optodes have shown the significant effect of burrowing organisms on localized O 2 distributions and revealed distinct depletions in O 2 due to microniches. Localized increases in pCO 2 and decreases in pH measured by optodes were attributed to elevated activity at microniches. Diffusive gradients in thin-films have shown isolated supersaturation of metals and sulphide, providing evidence for possible simultaneous oxidation of organic matter by sulphate and iron oxides. The stochastic nature of these data and the lack of information for the same precise location hinders interpretation in terms of sediment diagenesis. If microniches are known to account for a significant proportion of organic matter degradation, re-examination of the current understanding of sedimentary diagenesis may be needed. Further investigation on the distribution and frequency of microniches is required, including a wider range of analytes, in order to estimate their cumulative effect on element diagenesis, immobilisation/remobilisation processes and ultimately pollutant fate.

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Section: Sub-mm Life Positions Of Benthic Biota Using the Fluorescentmentioning

confidence: 99%

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Stockdale

Davison

Zhang

2009

Earth-Science Reviews

221

147

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“…Owing to the anticipated occurrence of varves in Icefall Lake, an Axelsson corer (Axelsson and HaÊ kanson, 1972) was also used to collect cores for X-ray photography (cf. Axelsson and HaÈ ndel, 1972). The Axelsson gravity corer uses rectangular core tubes of dimensions 5 .…”

Section: Lake Coringmentioning

confidence: 99%

Sedimentation in arctic proglacial lakes: Mittivakkat Glacier, south-east Greenland

2000

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Abstract:Several sediment cores were collected from two proglacial lakes in the vicinity of Mittivakkat Glacier, southeast Greenland, in order to determine sedimentation rates, estimate sediment yields and identify the dominant sources of the lacustrine sediment. The presence of varves in the ice-dammed Icefall Lake enabled sedimentation rates to be estimated using a combination of X-ray photography and down-core variations in 137 Cs activity. Sedimentation rates for individual cores ranged between 0 . 52 and 1 . 06 g cm À2 year À1 , and the average sedimentation rate was estimated to be 0 . 79 g cm À2 year À1 . Despite considerable down-core variability in annual sedimentation rates, there is no signi®cant trend over the period 1970 to 1994. After correcting for autochthonous organic matter content and trap eciency, the mean ®ne-grained minerogenic sediment yield from the 3 . 8 km 2 basin contributing to the lake was estimated to be 327 t km À2 year À1 . Cores were also collected from the topset beds of two small deltas in Icefall Lake. The deposition of coarse-grained sediment on the delta surface was estimated to total in excess of 15 cm over the last c. 40 years. In the larger Lake Kuutuaq, which is located about 5 km from the glacier front and for which the glacier represents a smaller proportion of the contributing catchment, sedimentation rates determined for six cores collected from the centre of the lake, based on their 137 Cs depth pro®les, were estimated to range between 0 . 05 and 0 . 11 g cm À2 year À1 , and the average was 0 . 08 g cm À2 year À1 . The longer-term (c. 100±150 years) average sedimentation rate for one of the cores, estimated from its unsupported 210 Pb pro®le, was 0 . 10±0 . 13 g cm À2 year À1 , suggesting that sedimentation rates in this lake have been essentially constant over the last c. 100±150 years. The average ®ne-grained sediment yield from the 32 . 4 km 2 catchment contributing to the lake was estimated to be 13 t km À2 year À1 . The 137 Cs depth pro®les for cores collected from the topset beds of the delta of Lake Kuutuaq indicate that in excess of 27 cm of coarse-grained sediment had accumulated on the delta surface over the last approximately 40 years. Caesium-137 concentrations associated with the most recently deposited (uppermost) ®ne-grained sediment in both Icefall Lake and Lake Kuutuaq were similar to those measured in ®ne-grained sediment collected from steep slopes in the immediate proglacial zone, suggesting that this material, rather than contemporary glacial debris, is the most likely source of the sediment deposited in the lakes. This ®nding is con®rmed by the 137 Cs concentrations associated with suspended sediment collected from the Mittivakkat stream, which are very similar to those for proglacial material.

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“…The low contrast between the silty clays and the trace fossils made it difficult to discern variations in bioturbation and individual trace fossils from the split core surfaces using optical inspection/photography alone. Therefore, to evaluate variations in bioturbation and trace fossil content, X-ray radiographs were taken following the method described by Bouma 97 . To do this, sediment sub-cores were taken from the 30 × 30 cm and up to 6 m long gravity core, using a 25 cm long and 6 mm thick plastic box pressed into the split core to produce ‘X-Ray sediment slabs’.…”

Section: Methodsmentioning

confidence: 99%

Exploring late Pleistocene bioturbation on Yermak Plateau to assess sea-ice conditions and primary productivity through the Ethological Ichno Quotient

Singh,

O’Regan,

Coxall

et al. 2023

Sci Rep

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Central Arctic, interglacial intervals have traditionally been associated with diverse and intense bioturbation, and abundant foraminifera, interpreted as indicating relatively low sea-ice concentrations and productive surface waters, while glacial intervals, typically barren, support the inverse. In this respect, the Yermak Plateau is anomalous. Biomarker studies suggest that glacial intervals were characterized by comparatively open water, while interglacials are marked by severe sea-ice conditions. Here we study downcore Ethological Ichno Quotient (EIQ) variations in trace fossils and bioturbation to test the hypothesis that different ethological classes vary in accordance with late Pleistocene changes in sea-ice extent, with deposit feeders increasing during reduced sea-ice cover and chemosymbiotic traces increasing during periods of thick perennial sea-ice conditions. Our results generally demonstrate that the abundance of traces like Planolites, Scolicia, and burrows produced by deposit feeders increase during episodes of seasonal sea-ice cover. In contrast, intervals with more severe sea-ice conditions are characterized by chemosymbiotic traces such as Chondrites and Trichichnus/Mycellia, suggesting lower food delivery and poorly ventilated bottom water conditions. The study thus confirms previous reconstructions of sea-ice conditions on the Yermak Plateau during interglacials, demonstrating that bioturbation variation provides insights into bentho-pelagic coupling under variable sea ice regimes in the Arctic Ocean.

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X-Radiography of Unextruded Sediment Cores

Cited by 13 publications

References 4 publications

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Sedimentation in arctic proglacial lakes: Mittivakkat Glacier, south-east Greenland

Exploring late Pleistocene bioturbation on Yermak Plateau to assess sea-ice conditions and primary productivity through the Ethological Ichno Quotient

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