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Titolo:
Changing sedimentation in tidal flat sediments of the southern North Sea from the Holocene to the present: a geochemical approach
Autore:
Dellwig, O; Hinrichs, J; Hild, A; Brumsack, HJ;
Indirizzi:
Univ Oldenburg, Inst Chem & Biol Marine Environm, D-26111 Oldenburg, Germany Univ Oldenburg Oldenburg Germany D-26111 onm, D-26111 Oldenburg, Germany
Titolo Testata:
JOURNAL OF SEA RESEARCH
fascicolo: 3-4, volume: 44, anno: 2000,
pagine: 195 - 208
SICI:
1385-1101(200012)44:3-4<195:CSITFS>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
MATTER; CARBON; EUROPE;
Keywords:
inorganic geochemistry; Holocene; present tidal rat sediments; SPM; Southern North Sea;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Brumsack, HJ Univ Oldenburg, Inst Chem & Biol Marine Environm, POB 2503, D-26111 Oldenburg, Germany Univ Oldenburg POB 2503 Oldenburg Germany D-26111 g, Germany
Citazione:
O. Dellwig et al., "Changing sedimentation in tidal flat sediments of the southern North Sea from the Holocene to the present: a geochemical approach", J SEA RES, 44(3-4), 2000, pp. 195-208

Abstract

This study presents geochemical evidence for a change in depositional energy conditions of tidal flat sediments (southern North Sea) from the Holocene, i.e. human unaffected, to present-day conditions. We investigated Holocene and present tidal flat sediments and suspended particulate matter (SPM) from the NW German coastal area (Spiekeroog Island back-barrier area and Jade Bay), as well as sediments from the Helgoland Island mud hole area. Samples were analysed for bulk parameters (TC, TIC), major (Al, Ca, Fe, Mg, K, P, Si, Ti), and trace elements (Ba, Pb, Rb, Sr, V, Zn, Zr). Enrichment factors versus average shale reveal four groups of elements forthe investigated Holocene and present sediments. Fe, Mg, K, Ba, Rb, and V show a shale-like behaviour and enrichments of Ca and Sr reflect the occurrence of carbonate, whereas higher levels of P, Pb, and Zn in the present samples are due to pollution. The fourth group consists of Si, Ti, and Zr, which may be used as indicators of depositional energy because these elementsare concentrated by particle sorting effects. The most pronounced geochemical difference between the Holocene and present tidal Rat sediments is an enrichment of Zr in the present samples. As Zr is commonly associated with heavy minerals, this enrichment indicates a higher depositional energy environment in the present sediments, which can be traced to modern dike building. The same effect, i.e. increasing current velocities, is responsible for a general depletion of fine-grained, Al-rich. material in the present sediments. The examination of SPM shows that large amounts of this fine-grained material are present in the water column and may be transported from the intertidal system into the open North Sea. The comparison of a calculated Holoceneclay accumulation rate with modern estimates of SPM deposition in the German Eight reveals about a two-fold higher deposition of fine material in theHolocene tidal flats. As the sediments from the Helgoland mud hole show a geochemical composition similar to Holocene tidal flat sediments, we assumethat the Helgoland mud hole may serve as a proximal depocentre in the southern North Sea for the SPM exported from the back-barrier systems. (C) 2000Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 31/03/20 alle ore 10:16:24