Data/hora: 12/06/2024 17:19:00

Provedor de dados: | 5
País: | France
Título: | Lithologie des délestages glaciaires (niveaux de Heinrich) de l'Eperon de Goban (Atlantique Nord-Est)
Autores: | Van Rooij, David.
Data: | 1999-06
Ano: | 1999
Palavras-chave: | Goban Spur; Quaternaire; Sédiments; Délestages glaciaires; IRD; Turbidites; Niveau de Heinrich; Calotte glaciaire.; Goban Spur; Quaternary; Sediments; IRD; Turbidites; Heinrich Layer; Heinrich Event; Ice Sheet.
Resumo: | Goban Spur is a marginal plateau, 250 km SW of Ireland, with the Celtic Margin on its eastern side and Porcupine Seabight Basin on its northern side. A set of NNE-SSW trending escarpments separate the upper part of Goban Spur from the Porcupine Abyssal Plain. We have studied a transect of Kullenberg cores taken during the 1984 Norestlante 2 campaign. Biostratigraphical and sedimentological (carbonate content) analyses were carried out by Müller [1986] and Foucault [1987]. All cores were accurately cleaned and described before digital photographs were taken in order to obtain grey level profiles and an estimate of the coarse grain size fraction (&gt; 150 µm). Magnetic susceptibility and gamma density measurements were obtained using a GEOTEK Multi Sensor Core Logger. These analyses allowed us identify the presence Heinrich levels 1 to 6. A laser microgranulometre was used to obtain grain size distribution in order to discriminate Heinrich layers from turbidites. The latter are considered containing better sorted material than in Heinrich levels. The cores were correlated using stratigraphic markers as the Heinrich layers, the Vedde Ash I and the onset of the isotopic stage 1. Because core KS12 seemed containing the longest sedimentary record and the best resolution, it was selected for a more detailed study. 70 samples were taken and analysed on dry density, porosity and its fraction superior than 150 µm. Abundance of foraminifers and lithic grains were examined using binocular microscope. Also smear slides taken at the same level were investigated. One sample was analysed using scanning electron microscope and semi-quantitative chemical micro-analysis, trying to identify the origin of the magnetic signal and the composition of the IRD. A preliminary age model was constructed using the Heinrich levels and the supposed transitions of isotopic stages as reference points. All cores showed presence of the IRD levels described by Heinrich in 1988. Lithological and biostratigraphical results of nearby DSDP Hole 548 suggest the presence of IRD levels up to 400 kyr on Goban Spur. However, recently the presence of European IRD has been proven on the Portuguese Margin and in the Bay of Biscay [Snoeckx et al., 1999]. The physical properties, biostratigraphical and lithological analyses indicate the presence of European IRD within all Goban Spur cores. Moreover, one can suggest that the 'Canadian' IRD levels (HL s.s.) are intercalated between European IRD levels, constituting the 'Eurolayers' [Auffret et al., 1999c]. Although the age model is preliminary it seems the Heinrich levels (s.s.) might be deposited approximately 1000 years after the deposition of the European IRD. This might suggest European Ice Sheet instabilities lie at the origin the Heinrich Events. The impact of the European Iceberg release on the glacial paleoceanographic and climatic conditions could have contributed to the instability of the Laurentide Ice Sheet. The sedimentary record within the transect appears dependent of the morphology on Goban Spur. The marginal plateau NE of Pendragon escarpment shows a hemipelagic sedimentation with a decreasing sedimentation rate from NE to SW. From 14 to 35 kyr BP sedimentation rates are considered elevated. A second marginal plateau SW of Pendragon shows a sedimentation rate that is considerably higher than the preceding plateau. The sedimentation on the foot of the slope is proven to be very complex through the interaction of mass wasting and bottom currents.
Tipo: | Text
Idioma: | Francês

Identificador:

http://archimer.ifremer.fr/doc/00412/52317/53096.pdf

http://archimer.ifremer.fr/doc/00412/52317/

Formato: | application/pdf

Fonte:

1999 UBO, IFREMER

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