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| Titel |
Ostracod stable isotope ratios indicate marine incursions in the Dacian
Basin during the Upper Miocene and Pliocene |
| VerfasserIn |
Alina Floroiu, Iuliana Vasiliev, Marius Stoica, Christiaan Van Baak, Arjan de Leeuw, 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 |
250144920
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| Publikation (Nr.) |
 EGU/EGU2017-8801.pdf |
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| Zusammenfassung |
| The Dacian Basin (Romania) was part of the former Paratethys Sea that stretched over
Eurasia during the Miocene to Pliocene. During that time connection of the Paratethys to the
open ocean was highly variable which hampers the correlation of regional and global
climatic and biotic events. Additionally, the high degree of endemism typically limits
the possibility for oxygen and carbon isotope comparisons on foraminifera. Here,
we present the first stable ostracod isotope (δ18O and δ13C) data of the Dacian
Basin covering the latest Miocene to Pliocene. Next to mollusks, ostracods currently
provide the only continuous biogenic carbonate record in the Dacian Basin. The
high-resolution ostracod δ18O and δ13C data were obtained from the well-dated,
thick Slanicul de Buzau section (e.g. van Baak, et al., 2015) and compared to the
strontium isotope data from the same section (Grothe et al., 2016). To minimize
the effects of species-dependent biosynthetic fractionation on the δ18O and δ13C
values we target single specimen measurements, preferentially on Cyprideis sp.,and
Tyrrhenocythere sp. Collectively, these data provide a first-order reconstruction
of the most significant changes affecting the basin during the 6.3 to 3.3 Ma time
interval. The δ18O and δ13C records from Slanicul de Buzau show both very large
variations attaining up to 13‰ (from around -11‰ to 2) over the sampled 3 Myr
interval. Such large changes cannot be explained only by interspecies dependent
variations in the biosynthetic fractionation. More likely, they indicate important
changes in δ18O of Dacian Basin water and carbon cycling. In particular, two intervals
have much higher δ18O values (attaining up to 0 and +2 ) when compared to the
rest of the record. The first occurs at ∼5.4 Ma and coincides with the ‘Bosphorian
Flood’, an interval that is also marked by elevated 87Sr/86Sr values close to those
recorded in the oceanic waters at that time (Grothe et al., 2016). We interpret this
interval as a time when an influx of saltier, possibly also warmer water, affected the
Dacian Basin. The second one, at around 3.4-3.3 Ma, is also marked by somehow
higher 87Sr/86Sr. Because the timing of this younger interval with higher δ18O
values coincides with the Mid Pliocene Warm period we speculate that an influx of
warmer, possibly also saltier water, affected the Dacian Basin at that time. The δ13C
data do not follow the δ18O record. At 5.5 Ma (during the ‘Bosphorian Flood’) the
highest δ13C values are recorded (+2 ). After this interval, until the end of our record
at 3.3 Ma we observe a consistent decrease in the δ13C values (up to -11 ). We
interpret this δ13C decrease as a steady change in the environmental conditions of the
Dacian Basin, from more eutrophic at 5.5 Ma to more oligotrophic towards 3.3 Ma. |
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