Carbonate recrystallisation and organic matter maturation in heat-affected sediments from the Shaban Deep, Red Sea

Reiner Botz*, Mark Schmidt, Jolanta Kus, Christian Ostertag-Henning, Axel Ehrhardt, Nazli Olgun, Dieter Garbe-Schönberg, Jan Scholten

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4 Atıf (Scopus)

Özet

Parasound profiles across the Shaban Deep in the Red Sea indicate turbiditic transport of surface sediments from the topographic height (basalt ridge) into the interior of the deep. This is supported by petrographical and (isotope-) geochemical evidence in the East Basin of the Shaban Deep where the presence of variable mixtures of authochtonous and allochthonous sediment compounds had been found.The uppermost 170cm of both sediment cores 17008-1 and 17009-3 reveal "normal" stable oxygen isotope values for the planktonic foraminifera Globigerinoides ruber near -1‰ which is indicative for carbonate formation in Red Sea surface water around 27°C. However, below 182cm in core 17008-1 highly variable δ 18O values for G. ruber between 0.26 and -10.68‰ occur which are not the result of temperature-controlled oxygen isotope fractionation between foraminiferal carbonate and Red Sea surface water. The lowest δ18O values of -10.68‰ measured for highly-altered foraminifera shells suggests carbonate precipitation higher than 90°C.Organic petrographical observations show a great diversity of marine-derived macerals and terrigenous organic particles. Based on petrographical investigations sediment core 17008-1 can be subdivided in intervals predominantly of authochtonous character (i.e. 1, 3, 5 corresponding to core depths 0-170cm, 370-415cm, 69-136cm), and allochthonous/thermally altered character (e.g. 2 and 4 corresponding to core depths 189-353cm and 515-671cm). Allochthonous/thermally altered material displays a wide to an extremely wide range of maturities (0.38-1.42% Rr) and also natural coke particles were found.Similarly, the organic geochemical and pyrolysis data indicate the predominance of well-preserved, immature algal and bacterial remains with a minor contribution of land plant material. Sediments below 170cm (core 17008-1) contain contributions of re-sedimented pre-heated material most likely from the area of the basaltic ridge. This is documented by individual coke particles reduced hydrogen indices and elevated Tmax values up to 440°C.An "oil-type" contribution (evidenced by mature biomarkers, hopene/hopane ratios, elevated background fluorescence, n-alkane distribution) is also present in the sediments which most likely originated at greater depth and impregnated the surface sediments.The heat source responsible for recrystallisation of foraminiferal carbonate and maturation of organic particles in Shaban Deep sediments most likely is attributed to modern basalt extrusions which now separate the Shaban Deep subbasins.

Orijinal dilİngilizce
Sayfa (başlangıç-bitiş)126-143
Sayfa sayısı18
DergiChemical Geology
Hacim280
Basın numarası1-2
DOI'lar
Yayın durumuYayınlandı - 7 Oca 2011
Harici olarak yayınlandıEvet

Finansman

Cruise leaders Peter Stoffers and Jürgen Pätzold are acknowledged for supporting the sampling campaigns during M31/2 and 52/3, respectively. Inge Dold is acknowledged for the sample preparation and coulometric measurements, and Ulrike Westernströer for help with ICPMS analyses. Peter Appel and Barbara Mader operated the electron microprobe. SEM was conducted in the laboratory of Priska Schäfer. Petra Fiedler performed XRD measurements. Nils Anders and Pieter Grootes are responsible for stable isotope and 14 C-measurements, respectively, at the Kiel Leibniz Laboratory. The International Atomic Energy Agency is grateful for the support provided to its Marine Laboratories by the Government of the Principality of Monaco . Financial support was mainly given by Peter Stoffers through DFG grants STO110/39-1 , and STO110/23-1 .

FinansörlerFinansör numarası
Government of the Principality of Monaco
Deutsche ForschungsgemeinschaftSTO110/39-1, STO110/23-1

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