Planktonic O record and sedimentological characteristics near the Belgica Carbonate Mounds (Porcupine Seabight, SW off Ireland)
Blamart, D.; Van Rooij, D.; Labeyrie, L.; Kozachenko, M.; Wheeler, A.; Henriet, J.-P. (2001). Planktonic O record and sedimentological characteristics near the Belgica Carbonate Mounds (Porcupine Seabight, SW off Ireland). J. Conf. Abstr. 6(1): 748
In: Journal of Conference Abstracts. Cambridge Publications: Cambridge. ISSN 1362-0886, more
In the Porcupine Seabight (SW off Ireland) 3 provinces of numerous carbonate mounds have recently been discovered (Henriet et al., 1998). The mechanisms and the timing of the formation of these mounds, where deep-water corals have been found, is still in discussion mainly because this area is 1) located on a structured continental margin and 2) under the influence of two water masses, the Mediterranean Outflow Water (MOW) and the overlying European North Atlantic Water (ENAW). Until now only short gravity cores were taken in the vicinity or on of the carbonate mounds hence limiting the interpretations.During the last IMAGES-cruise a giant piston core has been collected in order to establish the chronological framework as well as the sedimentological characteristics a few kilometres east of the Belgica mound province, situated on a slope section in the Eastern part of the Seabight.The core MD 992327 (26.25 m long) is located at 51°23 N and 11°39 W (651 m water depth). Two major lithological facies have been observed. The first one which is very homogeneous, corresponds to the first 12 m. It is represented by silty clay with few sulphid streaks and rare biogenic components. The second facies (from 12 to 26.25 m) is characterised by an alternations of medium to coarse grained sand with shell fragments and biogenic-rich layers. The base of the core correspond to a dark grey muddy fine sand. The lithological difference indicates probably a major change in the hydrology and/or a change in the sedimentary input at this location.O-C isotopic analysis have been performed on N. pachyderma s. d18O and 13C data are respectively in the range of 4.0 to 2.9 and 0.5 to -1.0 ‰ (PDB). O isotopic values are similar to those obtained in this part of the North Atlantic Ocean for the last glacial period. However, the signal is very ‘flat’ and it is quiet impossible to establish a chronology only based on the O-isotopic curve. Nevertheless, O and C isotopic values for the 12 first m are respectively depleted by 0.5 and 1 per mil compared to the lower part of the core. These shifts coincide also with changes in the lithological facies and foraminifera fauna and abundance. This work is within early stage of investigation and need to be combined with other sedimentological and biostratigraphical studies.
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