Element enrichment and provenance of the detrital component in Holocene sediments from the western Black Sea

Type Article
Date 2020-04
Language English
Author(s) Dekov Vesselin M.1, 2, Darakchieva Valentina Y.3, Billström Kjell4, Garbe-Schönberg C-Dieter5, Kamenov George D.6, Gallinari Morgane7, Dimitrov Lyubo8, Ragueneau Olivier9, Kooijman Ellen4
Affiliation(s) 1 : Tokyo University of Marine Science and Technology, Konan, Minato-ku, Tokyo, Japan
2 : Department of Marine Geosciences, IFREMER, Plouzané, France
3 : Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Sofia, Bulgaria
4 : Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
5 : Institute of Geosciences, Marine Climate Research, University of Kiel, Kiel, Germany
6 : Department of Geological Sciences, University of Florida, Gainesville, FL, USA
7 : UMR CNRS/UBO 6539 LEMAR, European Institute for Marine Studies, Technopôle Brest-Iroise, Plouzané, France
8 : Institute of Oceanology, Bulgarian Academy of Sciences, Varna, Bulgaria
9 : UMR CNRS/UBO 6539 LEMAR, European Institute for Marine Studies, Technopôle Brest-Iroise, Plouzané, France
Source Oceanologia (0078-3234) (Elsevier BV), 2020-04 , Vol. 62 , N. 2 , P. 139-163
DOI 10.1016/j.oceano.2019.10.001
WOS© Times Cited 2
Keyword(s) Anoxic, Black Sea, Element enrichment, Sr-Nd-Pb-isotopes, Holocene
Abstract

Concentrations of a large set of major and trace elements, and Sr, Nd and Pb isotope ratios were measured in Holocene sediments cored in the western deep Black Sea in order to unravel: (1) the controls of element enrichment, and (2) sources of the detrital component. The transition of the basin from oxic to euxinic resulted in enrichment or depletion in a number of elements in the deep-sea sediments. Authigenic Fe enrichment appears to depend on the amount of Fe mobilized from the sediment through the benthic redox shuttle mechanism and free H2S in the water column (degree of “euxinization”). Manganese enrichment is controlled by diagenetic reactions within the sediment: the dissolution of Mn minerals, Mn2+ diffusion upward and reprecipitation. Barium enrichment is also controlled by diagenetic reactions, sulfate reduction and methanogenesis, that take place above and below the sulfate-methane transition, respectively. The major part of V, Co, Ni, Cu, Zn, Cr, Mo, Cd and Sb is inferred to have co-precipitated with Fe in the euxinic deep waters and to have been incorporated into authigenic Fe-sulfides. Basin reservoir effect additionally influences the Mo enrichment. The U enrichment is interpreted to have a different origin in the two organic-rich stratigraphic units (II and I). It is inferred to be: (i) at the expense of the U inventory of the deepwater pool and a result of inorganic reduction of U at euxinic conditions in the lower Unit II; and (ii) at the expense of the U inventory of the surface water pool and a result of biogenic uptake and transfer to the sediment by the plankton in the upper Unit I. The high field strength elements are closely linked to the detrital component and their depletion in the organic-rich sediments reflects a dilution of the detrital component by the biogenic one. The enrichments of REE, Sn and Th are likely controlled by adsorption on clay minerals. Sr-Nd-Pb isotope compositions of the alumino-silicate component of the studied sediments are relatively uniform. They are most likely controlled by riverine suspended matter supplied mainly in the NW Black Sea (Danube Delta) and transported southward by marine currents, and to a lesser degree by suspended matter from the small rivers draining SE Bulgaria and NW Turkey. Wind-blown dust from the Sahara Desert appears to have a minor contribution to the alumino-silicate component of the sediments. The slight shift in the Pb isotopes in Unit I upper layers is possibly caused by the addition of anthropogenic Pb.

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Dekov Vesselin M., Darakchieva Valentina Y., Billström Kjell, Garbe-Schönberg C-Dieter, Kamenov George D., Gallinari Morgane, Dimitrov Lyubo, Ragueneau Olivier, Kooijman Ellen (2020). Element enrichment and provenance of the detrital component in Holocene sediments from the western Black Sea. Oceanologia, 62(2), 139-163. Publisher's official version : https://doi.org/10.1016/j.oceano.2019.10.001 , Open Access version : https://archimer.ifremer.fr/doc/00590/70164/