Sedimentary processes in the middle Nazaré Canyon

Masson, Douglas G.; Huvenne, Veerle A.I.; Stigter, Henko de; Arzola, R.G.; LeBas, T. P.

doi:10.1016/j.dsr2.2011.04.003

Cited by 29 publications

(21 citation statements)

References 33 publications

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“…For these samples, only foraminifera retained on a 180 μ m sieve were included in the dated material, to try to ensure that all came from the pelagic component of the sediment, on the assumption that any sediment reworked from further up canyon and transported by nepheloid layers or weak turbidity currents would be exclusively fine grained. This approach has been tested in similar sediments from Nazaré Canyon and found to give reliable results [ Masson et al , 2010b, 2011]. The two samples yielded dates of 16,550 and 20,000 Cal yr BP, significantly older than the dates above the sequence boundary, indicating that the sequence boundary is a hiatus or erosion surface ( and Figures 4 and 5).…”

Section: Results and Interpretationmentioning

confidence: 98%

“…The terrace turbidite sequences consist of closely spaced, thin‐bedded sands/silts interbedded with fine‐grained sediment that appears to be a mixture of hemipelagic material and turbidite mud. Similar fine‐grained sediments in nearby Nazaré Canyon have been interpreted as the product of quasi‐continuous sedimentation from nepheloid layers mixed with background hemipelagic deposition [ Masson et al , 2011]. Planktonic foraminifera up to 250 μ m in size, too large to have been transported by gravity currents with the fine‐grained sediment, are distributed through the fine‐grained sediment and are the primary evidence for the hemipelagic input and thus the quasi‐continuous nature of the nepheloid layer deposition.…”

Section: Results and Interpretationmentioning

confidence: 99%

“…This ensured successful targeting of the intended terraces. Terraces between 10 and 170 m above the apparent canyon floor were sampled, although studies using a Remotely Operated Vehicle (ROV) suggest that the canyon axis depth is often underestimated in v‐shaped canyon sections when measured by shipborne multibeam systems [ Masson et al , 2011].…”

Section: Methodsmentioning

confidence: 99%

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Seismic triggering of landslides and turbidity currents offshore Portugal

Masson

Arzola

Wynn

et al. 2011

Geochem. Geophys. Geosyst.

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[1] Sediments in deep water basins often include turbidites that record sediment input from adjacent continental margins. In seismically active areas, where turbidity currents are triggered by earthquakes, the basinal turbidite sequence may thus contain a record of palaeoseismicity, which can be used to infer the frequency of earthquakes affecting the margins of the basin. This is particularly useful where large earthquakes have a recurrence interval than is greater than the historical record. However, turbidity currents can be triggered by several processes, and it is often difficult to trace individual turbidites to their precise source areas and to assign a definite trigger to a particular turbidite. Here, we demonstrate that turbidites emplaced at $6600 and $8300 Cal yr BP in the Tagus Abyssal Plain, off Portugal, correlate with erosional hiatuses in two submarine canyons on the continental margin. The turbidites are sourced from simultaneous landsliding in both canyons, requiring regional triggers interpreted as earthquakes. An earthquake recurrence interval for the continental margin of $4000 years is estimated by extrapolation to deeper turbidites in the basin sequence. However, the example of the 1755 earthquake, which caused widespread devastation in southwest Iberia, shows that palaeoseismic interpretations must be made with caution. The 1755 earthquake had a magnitude >8.5 and yet the associated turbidite in the abyssal plain is typically $5 cm thick, while older turbidites can be >1 m thick. Given the large 1755 earthquake magnitude, the difference in turbidite thickness is unlikely to be related to the relative size of triggering earthquakes. Instead, we suggest that the offshore location of the 1755 earthquake, coupled with low sedimentation rates during the Holocene, may have limited the size of the associated turbidite.

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Section: Results and Interpretationmentioning

confidence: 98%

Section: Results and Interpretationmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Seismic triggering of landslides and turbidity currents offshore Portugal

Masson

Arzola

Wynn

et al. 2011

Geochem. Geophys. Geosyst.

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“…The Setúbal Canyon cuts the continental shelf close to the Sado River Estuary, and also leads to the Tagus Abyssal Plain. Comparable sedimentation regimes have been observed for both the Cascais and Setúbal canyons, with accumulation of sediment in the upper parts and limited down-canyon transport (de Stigter et al, 2011). Current regimes seem variable in both canyons.…”

Section: Introductionmentioning

confidence: 87%

“…Hydrodynamic patterns in this area are mainly seasonal and are driven by seasonally varying winds which regulate the down-and upwelling regimes in winter and summer, respectively (Vitorino et al, 2002;Quaresma et al, 2007). The largest canyon, The Nazaré Canyon, intersects the entire continental shelf and acts as a temporary sediment trap with intermittent transport of sediments and organic matter to the abyssal plain (de Stigter et al, 2007;Masson et al, 2011). Samples were taken at ca.…”

Section: Introductionmentioning

confidence: 99%

The importance of different spatial scales in determining structural and functional characteristics of deep-sea infauna communities

Ingels

Vanreusel

2013

Biogeosciences

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The urge to understand spatial distributions of species and communities and their causative processes has continuously instigated the development and testing of conceptual models in spatial ecology. For the deep sea, there is evidence that structural and functional characteristics of benthic communities are regulated by a multitude of biotic and environmental processes that act in concert on different spatial scales, but the spatial patterns are poorly understood compared to those for terrestrial ecosystems. Deep-sea studies generally focus on very limited scale ranges, thereby impairing our understanding of which spatial scales and associated processes are most important in driving structural and functional diversity of communities. Here, we used an extensive integrated dataset of free-living nematodes from deep-sea sediments to unravel the importance of different spatial scales in determining benthic infauna communities. Multiple-factor multivariate permutational analyses were performed on different sets of community descriptors (structure, structural and functional diversity, standing stock). The different spatial scales investigated cover two margins in the northeast Atlantic, several submarine canyons/channel/slope areas, a bathymetrical range of 700–4300 m, different sampling locations at each station, and vertical sediment profiles. The results indicated that the most important spatial scale for structural and functional diversity and standing stock variability is the smallest one; infauna communities changed substantially more with differences between sediment depth layers than with differences associated to larger geographical or bathymetrical scales. Community structure differences were greatest between stations at both margins. Important regulating ecosystem processes and the scale on which they occur are discussed. The results imply that, if we are to improve our understanding of ecosystem patterns of deep-sea infauna and the relevant processes driving their structure, structural and functional diversity, and standing stock, we must pay particular attention to the small-scale heterogeneity or patchiness and the causative mechanisms acting on that scale

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