5th Swiss Geoscience Meeting, Geneva 2007
High resolution geochemical and mineralogical
signature of sapropel S1 (Cretan Ridge, Eastern
Mediterranean)
Gennari Giordana*, Tamburini Federica**, Ariztegui Daniel***, Hajdas Irka**** &
Spezzaferri Silvia*
* University of Fribourg, Department of Geosciences, Geology and Paleontology, Ch.
du Musée 6, CH-1700 Fribourg (silvia.spezzaferri@unifr.ch;
giordana.gennari@unifr.ch)
** Institute of Geology, ETH-Zentrum, Universitaetstrasse 16, CH-8092 Zurich
(federica.tamburini@erdw.ethz.ch)
*** University of Geneva, Section of Earth Sciences, Rue des Maraichers 13, CH-1205
Geneva (daniel.ariztegui@terre.unige.ch)
****Ion Beam Physics, SI and ETH Zurich, CH-8093, Zurich (hajdas@phys.ethz.ch)
The Pliocene and Quaternary sedimentary sequence from the Mediterranean
Sea is characterized by the presence of several dark-colored organic rich layer
(Sapropels) intercalated in normal pelagic sediments. Various hypotheses have
been proposed to explain sapropels formation: high surface water productivity,
increased organic matter preservation under anoxic bottom-water conditions, or
most likely a combination of the two (overview in Meyers P.A. & Negri A. (Eds.),
2003).
We present here the geochemical and mineralogical characterization of
Sapropel S1 from Core SIN97 01-GC retrieved on the Cretan Ridge (35°49’07”
N, 22°42’02” E), which contains a very thick S1 (about 15 cm) and will allow a
high-resolution study of this interval. Furthermore, since a link between the
youngest Sapropel S1 in the Eastern Mediterranean and a Black Sea out-flow
has been proposed by many Authors in the framework of new investigations on
the “Noah’s Flood” (e.g., Aksu et al., 2002), we aim to investigate sea-level
(regional and global) and climate variations in respect to the evolution of early
human civilization in the area.
Our multi-proxy approach consists of sedimentary phosphorus, major and trace
elements (using a Micro-XRF) and mineralogical composition (XRD) analysis of
the sediment samples to reconstruct the circulation patterns in the region from
15 ka to the present, therefore including the interval of Sapropel S1 deposition.
Concentration and distribution of phosphorus in the sediments can be used to
identify and characterize anoxic sediments, and it has been already used to
trace bottom water circulation during the deposition of Sapropel S1 in the
Mediterranean Sea (Slomp et al., 2002). In particular, the core interval
corresponding to the S1 is characterized by a high concentration of “detrital”
phosphorus, giving us a straightforward indication of increased detrital input
during the deposition. The ongoing XRD analysis will provide a mineralogical
characterization of this material.
5th Swiss Geoscience Meeting, Geneva 2007
The XRF geochemical signature of S1 is consistent with an active post
depositional oxidation due to transition between different bottom water
oxygenation levels at the end of the sapropel deposition (Thomson et al., 1999),
as shown by Mn peaks and Fe and minor elements enrichment at the top of the
non-oxidized sapropel layer.
Furthermore, Fourier analysis of our proxy records shows a 1000 years
cyclicity. The 1000 years cycle is so far not fully explained, although the most
likely origin is a solar forcing mechanism (Debret et al., 2007).
This study is funded by the Swiss National Foundation Ref. 20001-111694.
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