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Studying the past of Mediterranean outflow based on 230th excess inventories and contourites

dc.contributor.authorVeiga-Pires, C.
dc.contributor.authorGhaleb, Bassam
dc.contributor.authorVoelker, Antje
dc.contributor.authorAbrantes, Fatima
dc.date.accessioned2013-07-24T10:16:18Z
dc.date.available2013-07-24T10:16:18Z
dc.date.issued2004
dc.date.updated2013-07-19T15:14:59Z
dc.description.abstractThe Mediterranean Outflow water (MOW) comes out from the Mediterranean Sea and then contours the northern slope of the Cadiz Gulf. Along its way to the southern Portuguese Margin, it divides itself into three levels flowing at different depths, 400 m, 800 m and 1200 m, respectively. These different pathways induce a series of contourites along the Cadiz slope as well as some sedimentary drifts, such as the Faro Drift. Based on the assumption that the sedimentologic characteristics of these contourites should give some light on the history of MOW velocity and intensity variability, two long sedimentary cores collected during the Marion Dufresnes 114/Images cruise in 1999 have been studied. The sampling sites of these two cores, MD99-2336 and MD99-2339, located in the Cadiz Gulf at 690 and 1177 m water column depths respectively, are thus, actually, below the first level and in the main core of the MOW third level. Along time, variations in these current levels, parallel to the slope, should then influence the existence and characteristics of contourites in both sedimentary records. For this purpose, thorium-230 (230Th) as well as granulometric and micropaleontologic analysis have been undergone at high resolution on the 4 uppermost meters spanning MIS1 to LGM times. The referred current prints can be detected by analysing surface and down core sediment for its 230Th content. This radioisotope is produced by the radioactive decay of uranium-234 which content in oceanic waters is known. Therefore, its production rate in the water column can be estimated as a linear function of the water depth (~ 2.6 dpm/cm2.ka for 1 km water depth). As 230Th is almost insoluble, it will sink to the oceanic floor together with the settling particles. This vertical flux to the underlying sediment is considered, in a first order approximation, equal to its production rate in the water column. On this basis, the 230Th excess in the sediment becomes a proxy for sedimentation versus erosion processes accordingly to the sign of the difference between the total and the vertical 230Th flux, i.e. if it is, respectively, positive or negative. With this method it is then possible to extrapolate on the location of the high velocity core area and whether its intensity changed or not looking at the inventory of excess 230Th in the contourite units. We acknowledge FEDER and OE that financed this study through the Portuguese Foundation for Science and Technology (PDCTM/PP/MAR/15297/1999).por
dc.identifier.citationVeiga-Pires, Cristina Carvalho; Ghaleb, Bassam; Voelker, Antje; Abrantes, Fátima. STUDYING THE PAST OF MEDITERRANEAN OUTFLOW BASED ON 230TH EXCESS INVENTORIES AND CONTOURITES, Trabalho apresentado em 32nd IGC- Florence, In 32nd IGC- Florence, Florence, Italy, 2004.por
dc.identifier.otherAUT: CVP01371;
dc.identifier.urihttp://hdl.handle.net/10400.1/2807
dc.language.isoengpor
dc.peerreviewedyespor
dc.subjectThorium 230por
dc.subjectContouritespor
dc.subjectPaleoceanographypor
dc.subjectMowpor
dc.titleStudying the past of Mediterranean outflow based on 230th excess inventories and contouritespor
dc.typeconference object
dspace.entity.typePublication
oaire.citation.conferencePlaceFlorence, Italypor
oaire.citation.title32nd IGCpor
person.familyNameVeiga-Pires
person.familyNameAbrantes
person.givenNameCristina
person.givenNameFatima
person.identifier113325
person.identifier.ciencia-id4A1F-CEDA-E66C
person.identifier.ciencia-id021D-CA76-20D2
person.identifier.orcid0000-0002-9323-0723
person.identifier.orcid0000-0002-9110-0212
person.identifier.ridB-5144-2008
person.identifier.ridB-5985-2013
person.identifier.scopus-author-id7801372905
person.identifier.scopus-author-id16030759200
rcaap.rightsopenAccesspor
rcaap.typeconferenceObjectpor
relation.isAuthorOfPublicationd1541efa-0eaa-48dc-aea3-a1e64aa0065a
relation.isAuthorOfPublication45b2d36a-1a11-4b6c-81b3-47f657904207
relation.isAuthorOfPublication.latestForDiscovery45b2d36a-1a11-4b6c-81b3-47f657904207

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