Diploma Programme Geography, Leibniz University Hannover: 104 p. (second reviewer)

Tephral layers are of great importance as isochronous conductive horizons, especially for Late Quaternary stratigraphy. Ash layers can be used to correlate and precisely date widely separated sites. The classification of ash finds used to be based on stratigraphic position and petrographic criteria. Today, a found ash layer is usually identified on the basis of the chemical composition of its volcanic glasses using electron beam microprobe analysis.

This paper provides an overview of the volcanic areas of Europe that were active during the late Quaternary. Many of the volcanoes or volcanic areas have shown no activity for several hundred or even a few thousand years and are therefore considered extinct. From a geological point of view, this very short period of inactivity is more likely to be seen as a temporary dormant phase of a volcanic system that is often still active. Another eruption could easily occur even after a pause of several 100,000 years. For this reason, the Eifel and Massif Central volcanic regions - which are currently inactive - are also included in this study. The geographical location of the explosive European eruption centres in relation to the study area and the large regional climatic conditions result in some probable supply areas for volcanic ash.

In the course of the work it was shown that the following areas are relevant sources of widespread Holocene ash deposits for north-west Europe: the Massif Central (Chaine de Puys), the Volcanic Eifel (Laacher See) and the two volcanic islands of Iceland and Jan Mayen in the northern Atlantic. Most of the ash horizons found can be attributed to Icelandic volcanism and only a few to Lake Laach or Jan Mayen. Deposits of French volcanism are not documented in the analysed region. On the basis of an extensive literature search, data on the distribution of the ash plumes of these well-known European eruptions were compiled and compared with each other. The current picture of the distribution of some tephral layers was then reviewed and partially supplemented or refuted.

It was shown that the deposition areas can be correlated with the eruption type and size on the one hand, and with the prevailing wind systems on the other. The deposits of the eruptions investigated can usually be well explained on the basis of today's climatic circulation in the northern hemisphere. For some of the ash layers, it is difficult to create a plausible depositional picture because they have been detected at very few locations. Others show large gaps in their distribution. In both cases, further finds are necessary to clarify the actual course of the ash plumes. Overall, however, the distribution areas for most of the eruptions analysed could be easily assigned to the sites, taking into account the eruption dynamics and knowledge of the prevailing wind systems.

In the practical part of the work, microprobe analyses were carried out on samples of Laacher See tephra (LST) from three sites in the southern Baltic Sea region. The three Laacher See eruption phases present in the analysed samples could be identified by their chemism. The results of the analyses were used to draw conclusions about the distribution of individual eruption phases of the Laacher See eruption.

All the basic principles required for the analyses carried out and for the identification of tephra, such as various preparation and detection methods or the function of the microprobe used, are explained in detail in a theoretical section. The quality of the analyses, detection limits and possible sources of error are also discussed.