Major dust events in Europe during the Marine Isotope Stage 5

Major dust storms are presently occurring at mid-latitudes in the Middle East and in Asia, and at low latitudes in Northern Africa and Australia. In contrast, Western Europe, except for some African dust originating from Sahara, does not experience such important and dramatic climatic events. This modern situation is particularly interesting as the present interglacial is usually interpreted as an analog of the Eemian interval. However, the penultimate interglacial and early glacial experienced, as evidenced in European terrestrial records, major dust events. They are clearly visible in loess sequences by their whitish color, overlying and underlying dark chernozem paleosols of MIS5 age. They are mostly recorded in Central Europe but their western limit, as such, appears to be the Rhine valley. We describe the base of the Dolni Vestonice (Czech Republic) loess sequence as the reference for this particular type of horizon. Such units were formed during intervals characterized by poor vegetation (high values in d13C, low magnetic susceptibility), and they show finer grain size values, for the fine sand and clay content, than the overlying pleniglacial loess deposits. Some of these dust horizons have been previously described as "Markers" by Kukla, and are dated at about 111-109 and 93-92 ka, a last one being slightly visible at about 75-73 ka. Others, described as eolian silts (ES) because corresponding to the loess material of Kukla's cycles, are observed in the same sequence and are dated at about 106-105, 88-86, and 78.5-77 ka. All these aeolian horizons correspond to short events of about 1 ka interval on average, and are synchronous to re-advances of the polar front over the North Atlantic as recorded by marine cores. They also correlate with abrupt changes observed in European vegetation. While ES appear to coeval significant dust peaks recorded in the Greenland ice cores, "Markers" do not show such relationships. This decoupling between the European and Greenland dust deposition during MIS 5 is an interesting phenomenon and differs from the glacial situation, where loess sedimentation mimics the Greenland dust record. Therefore, while the field observations support the previous interpretation of Markers as being formed by continental dust storms, different modes of the atmospheric circulation seem responsible for the two categories of dust events. In our presentation, we discuss the intense wind regimes responsible for these particular deposits.