A dynamic explanation for the origin of the western Mediterranean organic-rich layers

Type Article
Date 2008-07
Language English
Author(s) Rogerson M.1, Cacho I.2, Jimenez-Espejo F.3, 4, Reguera M. I.5, Sierro F. J.5, Martinez-Ruiz F.3, Frigola J.2, Canals M.2
Affiliation(s) 1 : Univ Hull, Dept Geog, Kingston Upon Hull HU17 0JF, N Humberside, England.
2 : Univ Barcelona, GRC Geociencies Marines, Dept Estratig & Paleontol & Geociencies Marines, Fac Geol, E-08028 Barcelona, Spain.
3 : UGR, CSIC, Inst Andaluz Ciencias Tierra, Fac Ciencias, E-18002 Granada, Spain.
4 : Japan Agcy Marine Earth Sci & Technol, Inst Res Earth Evolut, Yokosuka, Kanagawa 2370061, Japan.
5 : Univ Salamanca, Dept Geol, Fac Ciencias, E-37008 Salamanca, Spain.
Source Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2008-07 , Vol. 9 , N. 7 / Q07U01 , P. 1-20
DOI 10.1029/2007GC001936
WOS© Times Cited 37
Keyword(s) sapropel, Mediterranean, sea level, paleoceanography, circulation
Abstract The eastern Mediterranean sapropels are among the most intensively investigated phenomena in the paleoceanographic record, but relatively little has been written regarding the origin of the equivalent of the sapropels in the western Mediterranean, the organic-rich layers (ORLs). ORLs are recognized as sediment layers containing enhanced total organic carbon that extend throughout the deep basins of the western Mediterranean and are associated with enhanced total barium concentration and a reduced diversity (dysoxic but not anoxic) benthic foraminiferal assemblage. Consequently, it has been suggested that ORLs represent periods of enhanced productivity coupled with reduced deep ventilation, presumably related to increased continental runoff, in close analogy to the sapropels. We demonstrate that despite their superficial similarity, the timing of the deposition of the most recent ORL in the Alboran Sea is different than that of the approximately coincident sapropel, indicating that there are important differences between their modes of formation. We go on to demonstrate, through physical arguments, that a likely explanation for the origin of the Alboran ORLs lies in the response of the western Mediterranean basin to a strong reduction in surface water density and a shoaling of the interface between intermediate and deep water during the deglacial period. Furthermore, we provide evidence that deep convection had already slowed by the time of Heinrich Event 1 and explore this event as a potential agent for preconditioning deep convection collapse. Important differences between Heinrich-like and deglacial-like influences are highlighted, giving new insights into the response of the western Mediterranean system to external forcing.
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Rogerson M., Cacho I., Jimenez-Espejo F., Reguera M. I., Sierro F. J., Martinez-Ruiz F., Frigola J., Canals M. (2008). A dynamic explanation for the origin of the western Mediterranean organic-rich layers. Geochemistry Geophysics Geosystems, 9(7 / Q07U01), 1-20. Publisher's official version : https://doi.org/10.1029/2007GC001936 , Open Access version : https://archimer.ifremer.fr/doc/00237/34825/