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| Titel |
Geochemical comparison of the Eemian and Holocene interglacial marine ingression into the Black Sea |
| VerfasserIn |
Sebastian Eckert, Bernhard Schnetger, Carolina Montoya-Pino, Stefan Weyer, Helge Arz, Hans-Jürgen Brumsack |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035090
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| Zusammenfassung |
| During R/V Meteor expedition M72/5 in 2007, two gravity cores (22-GC-7/3) were recovered
which contain a second sapropel 7Â m beneath the recent (Holocene) one. Both sapropels
were sub-sampled on millimeter scale and analyzed by XRF, ICP-OES and HR-ICP-MS for
major and trace elements. Additionally, samples of the second sapropel were analyzed
for U and Mo isotopes by MC-ICP-MS. The estimated age of the older sapropel
fits with the Eemian interglacial. The trends in total organic and inorganic carbon
(TOC, TIC) in the Eemian sapropel compare well with the Holocene one. This fact
allows to create a lithological classification analogous to the acknowledged unit
classification of the Holocene sapropel. Comparable enrichments of redox-sensitive
elements (e.g. Co, Cr, Cu, Fe, Mo, Ni, Re, U and V) indicate that both sapropels were
deposited in anoxic and/or euxinic environments. These trace metal enrichments
suggest a similar formation mechanism, but a slightly different paleoenvironment
during the different time periods (units), which may be differentiated by δ238U and
δ97Mo. Both isotope proxies show an anoxic but non-euxinic environment during
the Eemian interglacial, while in the Holocene an euxinic water column was fully
established. The enrichment of major and trace elements of the Eemian sapropel shows
similarities with the Holocene sapropel from the same location, as well as with the
age-equivalent S5 sapropel from the Mediterranean. The geochemical data also fit
quite well to the bulk sample from DSDP Leg 42B Site 379A core 11 (Ross et al.
1978), the only record that recovered the Eemian sapropel in the Black Sea until
now. The bulk Srxs/Caxs ratio shows at least two marine events during the Eemian
interglacial, while in the recent sapropel only one marine ingression is documented. Caxs,
Mgxs/Caxs and Ti/Ca ratios show the alternating warm and cold events during the
glacial period and the transition to the Holocene interglacial in the region of the
southern Black Sea. Paleoproductivity proxies (e.g. TOC, P, Ba, Cu and Ni) document
increased deposition/preservation of organic matter during the warmer periods in the
Black Sea. Our study implies that repeated marine sapropel formations are linked to
interglacial periods and reflect the global sea level rise and flooding of the Bosporus
sill.
References:
Ross, D. A., 1978. Initial reports of the Deep-Sea Drilling Project Vol. XLII. U.S.
Government Printing office, Washington D.C. |
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