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Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): sediment accumulation rates, trawling and winnowing effects.

Karageorgis, A. P. and Kaberi, H. and Price, N. B. and Muir, G. K. P. and Pates, J. M. and Lykousis, V. (2005) Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): sediment accumulation rates, trawling and winnowing effects. Continental Shelf Research, 25 (19-20). pp. 2456-2475. ISSN 0278-4343

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Abstract

Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from 210Pb and 137Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm−2 yr−1 (Axios and Aliakmon Rivers) and 0.414 g cm−2 yr−1 (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess 210Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from 1 cm in inshore stations to 2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or ‘excess’ metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.

Item Type: Article
Journal or Publication Title: Continental Shelf Research
Uncontrolled Keywords: Sediment accumulation rates ; Geochemistry ; Winnowing ; Trawling ; Thermaikos Gulf ; Aegean Sea
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 21261
Deposited By: ep_ss_importer
Deposited On: 07 Jan 2009 16:58
Refereed?: No
Published?: Published
Last Modified: 26 Jul 2012 15:44
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21261

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