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| Titel |
Marine influx hits Caspian Sea at the Pleistocene transition |
| VerfasserIn |
Iuliana Vasiliev, Christiaan Van Baak, Gert-Jan Reichart, Thomas Hoyle, Wout Krijgsman, Andreas Mulch |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149224
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| Publikation (Nr.) |
 EGU/EGU2017-13557.pdf |
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| Zusammenfassung |
| Landlocked basins like the Caspian Sea are highly sensitive to changes in their hydrological
budget, especially at times of disconnection from the global oceans. Modifications to the
balance of river runoff, evaporation and precipitation are hence transferred quickly to
changes in water lever while subsequent reconnection to open marine conditions may
result in complete environmental turnover. Here we reconstruct hydrological and
environmental changes in the Caspian Sea basin, using compound-specific hydrogen
isotope (δD) data on excellently preserved long chain n-alkanes and alkenones. These
biomarkers were extracted from Pliocene to Pleistocene successions, including the
Productive Series, Akchagylian and Apsheronian (as in the regional Caspian Basin
nomenclature). Terrestrial plant wax long chain n-alkanes δDvalues reflect continental
hydrological changes in the region surrounding the Caspian Sea. δDvalues of long chain
alkenones, in contrast, are derived from haptophyte algae within the basinal water
column and typically reflect changes in δD of Caspian Sea water. The δD valuesof the
terrestrial long chain n-alkanes show a variation of 55‰ from as high as -120 ‰ at the
base of the sampled section (at ∼ 3.55 Ma) to as low as -175 ‰ in the youngest
part (at ∼ 2.2 Ma). The change towards constant δDn−alkane values around -175
‰ appears to be correlated with the occurrence of alkenones in the sampled section
suggesting a newly installed connection of the Caspian Sea with a marine basin
at that time. This observation is supported by δDalkenone values of around -190
‰ being similar to age-equivalent δDalkenone values recorded in the marine realm.
Based on the appearance of alkenones in the Caspian Basin sections and on their δD
values we conclude that during Akchagylian, at ∼2.5 Ma, the Caspian Sea became
connected to the open ocean, permitting the influx of marine biota into the basin. |
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