Sediment drifts and contourites on the continental margin off northwest Britain

Stoker, Martyn S.; Akhurst, Maxine; Howe, John; Stow, Dorrik

doi:10.1016/s0037-0738(97)00086-9

Cited by 116 publications

(63 citation statements)

References 21 publications

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“…The sediment drift complex at the base of the WTR is described in detail by Howe et al (1994), Stoker et al (1998) and Masson et al (2002). It consists of three sediment drift types: an elongated drift of ca.…”

Section: Geologymentioning

confidence: 99%

Sediment dynamics of a sandy contourite: the sedimentary context of the Darwin cold-water coral mounds, Northern Rockall Trough

Huvenne

Masson

Wheeler

2008

Int J Earth Sci (Geol Rundsch)

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Grainsize, mineralogy and current-meter data from the Northern Rockall Trough are presented in order to characterise the sandy contourite that forms the sedimentary environment of the Darwin cold-water coral mounds, and to investigate the impact of this environment on the mound build-up. Large clusters of small cold-water coral mounds, 75 m across and 5 m high, have been found southwest of the Wyville Thomson Ridge, at 900-1,100 m water depth. Their present-day sedimentary environment consists of a subtly sorted sandy contourite, elongated NE-SW, roughly parallel to the contours. Critical erosional and depositional current speeds were calculated, and trends in both the quartz/feldspar and foraminifera fractions of the sands show a bi-directional fining from bedload/erosiondominated sands in the NE to suspension/depositiondominated sediments in the SW and towards the S (downslope). This is caused by a gradual reduction in governing current speed, linked to a reduction in slope gradient, and by the increasing distance from the current core in the downslope direction. No specific characteristics were found distinguishing the mound sediments from the surrounding sands: they fit in the overall spatial pattern. Some mound cores show hints of a fining-upward trend. Overall the mound build-up process is interpreted as a result of sediment baffling.

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Section: Geologymentioning

confidence: 99%

Sediment dynamics of a sandy contourite: the sedimentary context of the Darwin cold-water coral mounds, Northern Rockall Trough

Huvenne

Masson

Wheeler

2008

Int J Earth Sci (Geol Rundsch)

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“…Stoker et al (1998) estimates that in the FSC 8-16 % of the seabed is composed of of muddy sand facies. Assuming a similar fraction is present in the suspend matter with a lower density of ρ = 2350 kg m −3 (Sumner et al, 2009) gives us an error of 2 % in our result which is well below level of error we estimated for reflection coefficient.…”

Section: Discussionmentioning

confidence: 99%

“…Direct measurements at 1000 m depth on the Shetland side of the FSC show a variable current speed with a mean of 0.25 m s −1 with an M 2 period with occasional peaks in speed of over 0.5 m s −1 (Bonnin et al, 2002). These bottom currents have sufficient strength to mould and rework the seafloor sediments within the FSC (Stoker et al, 1998;Bonnin et al, 2002).…”

Section: E a Vsemirnova Et Al: Mapping Turbidity Layers 13mentioning

confidence: 97%

Mapping turbidity layers using seismic oceanography methods

2012

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Abstract. Using a combination of seismic oceanographic and physical oceanographic data acquired across the FaroeShetland Channel we present evidence of a turbidity layer that transports suspended sediment along the western boundary of the Channel. We focus on reflections observed on seismic data close to the sea-bed on the Faroese side of the Channel below 900 m. Forward modelling based on independent physical oceanographic data show that thermohaline structure does not explain these near sea-bed reflections but they are consistent with optical backscatter data, dry matter concentrations from water samples and from seabed sediment traps. Hence we conclude that an impedance contrast in water column caused by turbidity layers is strong enough to be seen in seismic sections and this provides a new way to visualise this type of current and its lateral structure. By inverting the seismic data we estimate a sediment concentration in the turbidity layers, present at the time of the survey, of 45 ± 25 mg l −1 . We believe this is the first direct observation of a turbidity current using Seismic Oceanography.

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“…The sediment input to the northern Rockall Trough has been minimal since the last glaciation. The Holocene sedimentary regime has been controlled by strong bottom currents redistributing older sediments (Kenyon 1986;Stoker et al 1998;Masson et al 2002Masson et al , 2003. Regionally, the upper few metres of sediment on the lower slopes and basin floor of the northern Rockall Trough typically consist of a thin (< 20 cm) surface layer of coarse, sandy Holocene sediment overlying thick glaciogenic mud containing sparse coarse- (Ryan et al 2009) grained horizons (Howe 1995(Howe , 1996.…”

Section: Sediment Materialsmentioning

confidence: 99%

An Empirical Assessment of Variable Water Content and Grain-Size on X-Ray Fluorescence Core-Scanning Measurements of Deep Sea Sediments

Maclachlan

Hunt

Croudace

2015

Developments in Paleoenvironmental Research

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Deciphering the signal within X-ray fluorescence (XRF) core scanner data can be complex in comparison to conventional laboratory XRF analysis where samples are milled and pelleted or beaded. One complicating factor is that the down-core variability in water content and grain-size can affect element count rates thereby potentially leading to inaccurate interpretations. Experiences using an Itrax XRF core scanner data highlight some of the pitfalls that can occur when the sediment is inhomogeneous. We show that over a threshold of 25 wt.% coarse grained material ( > 63 µm) within the sediment there is a potential for causing significant variability in certain elements. It is also shown that water content variability has a major effect above 40 %.

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Sediment drifts and contourites on the continental margin off northwest Britain

Cited by 116 publications

References 21 publications

Sediment dynamics of a sandy contourite: the sedimentary context of the Darwin cold-water coral mounds, Northern Rockall Trough

Sediment dynamics of a sandy contourite: the sedimentary context of the Darwin cold-water coral mounds, Northern Rockall Trough

Mapping turbidity layers using seismic oceanography methods

An Empirical Assessment of Variable Water Content and Grain-Size on X-Ray Fluorescence Core-Scanning Measurements of Deep Sea Sediments

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