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| Titel |
Was Mediterranean region warmer during the Messinian Salinity Crisis? |
| VerfasserIn |
Iuliana Vasiliev, Stefano Lugli, Eva Niedermeyer, 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 |
250144714
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| Publikation (Nr.) |
 EGU/EGU2017-8575.pdf |
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| Zusammenfassung |
| Between 5.97-5.33 Ma kilometres-thick evaporite units were deposited in the Mediterranean
basin during an event known as the Messinian salinity crisis (MSC). It is generally accepted
that the MSC reflects a dry period, with rates of evaporation exceeding those of precipitation
and riverine runoff. However, contemporary changes in continental and marine
circum-Mediterranean temperature are less well constrained. Here we reconstruct mean
annual temperatures (MAT) on continental realm using the branched glycerol dialkyl glycerol
tetraether (GDGT). Additionally, sea surface temperatures (SSTs) of the Mediterranean Sea
between 5.55 and 5.33 Ma were estimated using isoprenoidal GDGT based TEX86 and
alkenone derived U37k proxies. These excellently preserved organic biomarkers
were extracted from the Eraclea Minoa section (Sicily) deposited during the ‘Upper
Gypsum’, stage 3 of the MSC (5. 55 to 5.33 Ma). The calculated MATs for the ‘Upper
Gypsum’ interval at Eraclea Minoa are 19 to 22 ºC, slightly higher than the present day
temperatures of 15 to 20 ºC on Sicily. For the samples where the branched and
isoprenoid tetraether (BIT) index was lower than the 0.4 threshold limit we could
calculate TEX86 derived SSTs as high as 32 ºC. Furthermore, we compared the
TEX86 derived SSTs with the alkenone based, U37k proxy derived SST estimates
from the same samples. These values are slightly higher than the U37k derived SST
of 20 to 28 ºC (the maximum of the available calibration range for U37k proxy).
These elevated temperature values are up to 10 ºC higher than temperatures recorded
in the past 10 kyr in the Mediterranean Sea using the same U37k proxy (Cacho
et al., 2002) and even up to 18 ºC higher than those estimated for the last glacial
period. Values up to 27 ºC were recorded during the latest Pleistocene (Herbert et
al., 2015) and between 13 and 8 Ma in the Mediterranean region (Tzanova et al.,
2015). For the interval between the 8.0 and 6.4 Ma the U37k derived SSTs vary
between 19 and 27 ºC, close to our calculation for Eraclea Minoa section (20 to 28
ºC). Independent of common pitfalls that may arise in using molecular biomarkers
as temperature proxies, both SST estimations independently hint towards much
warmer Mediterranean Sea water during the latest phase of the MSC. These elevated
temperatures further coincide with higher δD values measured on alkenones and long chain
n-alkanes (both records indicating for more arid and/or warmer conditions than
today for the ‘Upper Gypsum’ Eraclea Minoa, between 5.55 and 5.33 Ma). We
therefore conclude that the climate during stage 3 of MSC (5.55 to 5.33 Ma), at the
paleogeographic position of Sicily, was drier and warmer that present-day conditions. |
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