Climatically driven changes in sediment supply on the SW Iberian shelf since the Last Glacial Maximum.

Stumpf, Roland, Frank, Martin , Schönfeld, Joachim and Haley, Brian A. (2011) Climatically driven changes in sediment supply on the SW Iberian shelf since the Last Glacial Maximum. Earth and Planetary Science Letters, 312 (1-2). pp. 80-90. DOI 10.1016/j.epsl.2011.10.002.

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Abstract

The assemblages of marine sediments on the SW Iberian shelf have been controlled by contributions from distinct sources, which have varied in response to environmental changes since the Last Glacial Maximum (LGM). The rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. They are entrained into the suspended particulate matter (SPM) carried by Mediterranean Outflow Water (MOW), which enters the eastern North Atlantic through the Strait of Gibraltar and spreads at intermediate depths in the Gulf of Cadiz and along the Portuguese continental margin. Other major sediment sources that have contributed to the characteristics and budget of SPM along the flow path of MOW on the SW Iberian shelf are North African dust and river-transported particles from the Iberian Peninsula.

To reconstruct climate- and circulation-driven changes in the supply of sediments over the past ~ 23 000 cal yr B.P., radiogenic Nd, Sr and Pb isotope records of the clay-size sediment fraction were obtained from one gravity core in the Gulf of Cadiz (577 m water depth) and from two gravity cores on the Portuguese shelf (1745 m, 1974 m water depth). These records are supplemented by time series analyses of clay mineral abundances from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not accompanied by strong changes in sediment provenance or transport, whereas Heinrich Event 1 (H1) and the African Humid Period (AHP) were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the North American craton during H1 and diminished supply of Saharan dust during the AHP. The data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures.

Document Type: Article
Keywords: Sedimentology; Paleoceanography; Geochemistry; Iberian margin; Mediterranean Outflow Water; neodymium isotopes; lead isotopes; strontium isotopes; clay minerals
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2011.10.002
ISSN: 0012-821X
Projects: Future Ocean
Date Deposited: 16 Nov 2011 08:53
Last Modified: 23 Sep 2019 23:32
URI: http://oceanrep.geomar.de/id/eprint/12574

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