Deep-water geomorphology of the glaciated Irish margin from high-resolution marine geophysical data

Sacchetti, Fabio; Benetti, Sara; Georgiopoulou, Aggeliki; Shannon, Patrick M.; O’Reilly, B. M.; Dunlop, P; Quinn, Rory; Cofaigh, Colm Ó

doi:10.1016/j.margeo.2011.11.011

Cited by 28 publications

(19 citation statements)

References 53 publications

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“…Facies 4, which occupies mostly areas within the RBSC limits (scarps and lobes) near the surface and at depth, represents deformed slope sediments. The acoustic character demonstrated in this facies (transparent, chaotic reflections) is typical of slide deposits (e.g., Bull et al, 2009;Sacchetti, Benetti, Georgiopoulou, et al, 2012). The extent of this seismic facies suggests that slide deposits are present beyond the confines of the RBSC limits as seen on the seafloor, to the east (Figure 4).…”

Section: 1029/2018gc007674mentioning

confidence: 83%

On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

Georgiopoulou¹,

Krastel²,

Finch³

et al. 2018

Preprint

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One of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event, a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments. In this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the Rockall Bank Slide Complex, offshore western Ireland, is the composite of multiple slope collapse events and, if so, to differentiate them. We conclude that there have been at least three voluminous episodes of slope collapse separated by long periods of slope stability, a fourth, less voluminous event, and possibly a fifth more localized event. The oldest event, Slide A (200 km 3 ), is estimated to be several hundred thousand years old. The second event, Slide B (125 km 3 ), took place at the same location as slide A, reactivating the same scar, nearly 200 ka ago, possibly through retrogression of the scarp. Slide C (400 km 3 ) took place 22 ka ago and occurred further north from the other slides. Slide D was a much smaller event that happened 10 ka ago, while the most recent event, albeit very small scale, took place within the last 1,000 years. This study highlights the need to thoroughly investigate large slide complexes to evaluate event sequencing, as seismic studies may hide multiple small-scale events. This work also reveals that the same slide scarps can be reactivated and generate slides with different flow behaviors.Plain Language Summary When studying large underwater landslides, determining whether what we see in our data was created by one large landslide event or several smaller events is very difficult due to the inaccessibility of the deep sea. But, being able to distinguish between different events and their frequency allows for more accurate risk assessments. Forty years ago, a large landslide was discovered in the northeast Atlantic, on the flank of an underwater plateau offshore of western Ireland. Studies since its discovery have interpreted it as one large event. With present-day technology and a higher resolution data set, we have discovered that it is composed of several landslides. The most recent, but very small and localized event, happened in the last 1,000 years. The one before is happened 10,000 years ago, and it was the size of 680,000 Olympic-size swimming pools. Around 22,000 years ago, a landslide 250 times bigger slid down the slope. Two more similar size events happened more than 200,000 years ago, but the further back in time we go the data resolution gets poorer. We think that the sizes of large underwater landslides found in the world's oceans and lakes may have been significantly overestimated, but their frequency may have actually been underestimated.

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Section: 1029/2018gc007674mentioning

confidence: 83%

On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

Georgiopoulou¹,

Krastel²,

Finch³

et al. 2018

Preprint

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“…Cai et al, 1997). These are inferred to be associated with the eastward staged retreat of a grounded ice margin, as inferred for nested moraines at seabed on the north-west Irish shelf (Ó Cofaigh et al, 2012). The physical limit to glacial extent may have been formed by increasing water depths and concomitant increases in ice marginal buoyancy and calving (Howe, 1995).…”

Section: Accepted Manuscriptmentioning

confidence: 95%

“…Todd et al, 2007). On Irish National Seabed Survey high resolution multibeam bathymetric data (Cullen, 2003), iceberg scours are also observed on the contemporary seabed, occurring throughout the region in water depths of 180-575 m (Sacchetti et al, 2012;Thébaudeau et al, 2015) (Fig. 1).…”

Section: Accepted Manuscriptmentioning

confidence: 96%

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A Plio-Pleistocene sediment wedge on the continental shelf west of central Ireland: The Connemara Fan

et al. 2018

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Citation for published item:wgrronD tephen nd regD hniel nd gofighD golm ¡ yF nd wonteysD vier nd h¡ eudeuD fenjmin nd grvenD uiern nd qD wuhmmd wudsr nd govD endre @PHIVA 9e lioEleistoene sediment wedge on the ontinentl shelf west of entrl srelnd X the gonnemr pnF9D wrine geologyFD QWW F ppF WUEIIRF Further information on publisher's website: httpsXGGdoiForgGIHFIHITGjFmrgeoFPHIVFHPFHHW Publisher's copyright statement: c 2018 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract Glacigenic sediment fans recording shelf edge deposition from marineterminating ice sheets have previously been recognised along the NW European continental margin from Svalbard to as far south as Donegal, off north-west Ireland. Here we present evidence of a previously unrecognised partially glacially-fed Plio-Pleistocene sediment wedge on the continental shelf west of central Ireland using 2D and 3D seismic reflection data correlated to a commercial borehole. The 'Connemara Fan' covers a shelf area of approximately 9000 km 2 in water depths of 125 -310 m, extending westwards into the Porcupine Seabight from the Irish Mainland Shelf. The wedge comprises up to 160 m of sediment that culminates in a prominent moraininc ridge at seabed and contains two discordant reflection surfaces (R1 and 2) that subdivde it into three seismic units (SU1-3). Stratigraphic boreholes 27/24-2 and 2A located on the inner shelf show that the lower unit (SU1) is composed of Pliocene marine sediments, while SU2 and 3 comprise glacially influenced facies of Quaternary age. Extracts from a 3D seismic data volume within the central part of the fan show channels within the Pliocene succession, while iceberg scours are observed on the R1 and R2 reflectors. The Connemara Fan is inferred to record sediment supply from central western Ireland, with Quaternary units probably recording at least two glacial advance-retreat cycles with ice sheets repeatedly grounding across the inner (Irish Mainland) shelf. Our findings extend the range of glacially-influenced grounding line depocentres southwards along the NW European continental margin.

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“…Large-scale submarine channel systems also characterize some glaciated continental margins [92][93][94]. In the Labrador Sea, offshore of Hudson Strait, the continental slope is characterized by alternating high to moderate and low-relief imparted by the presence of canyons incising the slope [92].…”

Section: (B) Reconstruction Of Past Ice Sheets On High-and Mid-latitumentioning

confidence: 99%

Ice sheets viewed from the ocean: the contribution of marine science to understanding modern and past ice sheets

Cofaigh

2012

Phil. Trans. R. Soc. A.

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Over the last two decades, marine science, aided by technological advances in sediment coring, geophysical imaging and remotely operated submersibles, has played a major role in the investigation of contemporary and former ice sheets. Notable advances have been achieved with respect to reconstructing the extent and flow dynamics of the large polar ice sheets and their mid-latitude counterparts during the Quaternary from marine geophysical and geological records of landforms and sediments on glacierinfluenced continental margins. Investigations of the deep-sea ice-rafted debris record have demonstrated that catastrophic collapse of large (10 5 -10 6 km 2 ) ice-sheet drainage basins occurred on millennial and shorter time scales and had a major influence on oceanography. In the last few years, increasing emphasis has been placed on understanding physical processes at the ice-ocean interface, particularly at the grounding line, and on determining how these processes affect ice-sheet stability. This remains a major challenge, however, owing to the logistical constraints imposed by working in ice-infested polar waters and ice-shelf cavities. Furthermore, despite advances in reconstructing the Quaternary history of mid-and high-latitude ice sheets, major unanswered questions remain regarding West Antarctic ice-sheet stability, and the longterm offshore history of the East Antarctic and Greenland ice sheets remains poorly constrained. While these are major research frontiers in glaciology, and ones in which marine science has a pivotal role to play, realizing such future advances will require an integrated collaborative approach between oceanographers, glaciologists, marine geologists and numerical modellers.

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Deep-water geomorphology of the glaciated Irish margin from high-resolution marine geophysical data

Cited by 28 publications

References 53 publications

On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

A Plio-Pleistocene sediment wedge on the continental shelf west of central Ireland: The Connemara Fan

Ice sheets viewed from the ocean: the contribution of marine science to understanding modern and past ice sheets

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