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Titolo:
Oxygen isotopes of marine diatoms and relations to opal-A maturation
Autore:
Schmidt, M; Botz, R; Rickert, D; Bohrmann, G; Hall, SR; Mann, S;
Indirizzi:
Univ Kiel, Inst Geosci, D-24118 Kiel, Germany Univ Kiel Kiel Germany D-24118 Kiel, Inst Geosci, D-24118 Kiel, Germany GEOMAR, Res Ctr Marine Geosci, D-24148 Kiel, Germany GEOMAR Kiel GermanyD-24148 Res Ctr Marine Geosci, D-24148 Kiel, Germany Univ Bristol, Sch Chem, Bristol BS8 1TS, Avon, England Univ Bristol Bristol Avon England BS8 1TS Bristol BS8 1TS, Avon, England
Titolo Testata:
GEOCHIMICA ET COSMOCHIMICA ACTA
fascicolo: 2, volume: 65, anno: 2001,
pagine: 201 - 211
SICI:
0016-7037(200101)65:2<201:OIOMDA>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
DEEP-SEA SEDIMENTS; BIOGENIC SILICA; CLIMATIC RECORD; HYDROUS SILICA; SOUTHERN-OCEAN; WATER; DISSOLUTION; TEMPERATURE; DIAGENESIS; FRACTIONATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
48
Recensione:
Indirizzi per estratti:
Indirizzo: Schmidt, M Univ Kiel, Inst Geosci, Olshaussenstr 40-60, D-24118 Kiel, Germany Univ Kiel Olshaussenstr 40-60 Kiel Germany D-24118 el, Germany
Citazione:
M. Schmidt et al., "Oxygen isotopes of marine diatoms and relations to opal-A maturation", GEOCH COS A, 65(2), 2001, pp. 201-211

Abstract

In order to develop the potential tool of diatom oxygen isotopes for paleoenvironmental studies we compared oxygen isotopes of natural marine diatomssampled from ocean surface water, sediment traps and surface sediments with oxygen isotopic fractionations determined for laboratory diatom cultures. Freshly grown natural diatoms (phytoplankton samples and sediment trap material) and cultured diatoms reveal similar oxygen isotope fractionation factors. The fresh diatoms have 3 to 10 parts per thousand lower isotope fractionation factors than fossil (sedimentary) diatoms. A temperature-related oxygen isotope fractionation could not be established for the laboratory cultures (and the natural phytoplankton samples), and there is evidence that diatom growth rate until reaching the stationary growth state also controls the measured silica-water oxygen isotope fractionation factor. It is possible, however, that slow diatom growth in sea surface water may well lead to a temperature-dependent silica-water oxygen isotope fractionation which is the prerequisite for a use of diatom oxygen isotopes in palco-surface waterstudies. FTIR-spectroscopic analyses of various diatomaceous materials revealed that the ratio of integrated peak intensities for Si-O-Si/Si-OH correlates with the 3 to 10 parts per thousand delta O-18(silica) increase from fresh to fossil diatoms. Open-system (flow-through) silica dissolution experiments suggest that the diatom frustules are isotopically homogenous and that the increase in O-18 is therefore not due to dissolution of isotopically light surficial Si-OH groups. It is concluded that slow internal condensation reactions during silica maturation in surface sediments cause both an increase in the intensity ratio of Si-O-Si/Si-OH and the O-18 content of framework oxygen. These findings also indicate that the oxygen isotope compositions ofmarine sediment diatoms do not indicate sea surface water temperature but rather reflect variable O-18 contents of surface sediments. Copyright (C) 2001 Elsevier Science Ltd.

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Documento generato il 30/11/20 alle ore 16:20:34