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Goldschmidt 2007 Excursion: A volcanic hike in the Tertiary Siebengebirge

Leaders : Melanie Moll and Holger Paulick (Mineralogisch-Petrologisches Institut, Universität Bonn)

The city of Cologne was a splendid location for an event such as the Goldschmidt conference with abundant opportunities for evening entertainment and bar hopping. Most delegates probably did not get a chance to appreciate that there are spectacular geological sites to be visited in the close proximity of the conference venue, in particular volcanologically speaking.

This field trip to the Miocene Siebengebirge (seven mountains) volcanic field provided a great opportunity to 35 geologists from all over the world to get to know a piece of German wilderness, geology, medieval history, and as a treat at the end of the day, a traditional dinner under the stars in a vineyard at the foot of the Drachenfels (dragons hill).

All of the transportation was by public trains and busses, probably making this trip one of the most CO2-friendly in Goldschmidt history. Everybody assembled at Cologne main train station for the ~30 km ride southward to the foot of the Siebengebirge national park located immediately at eastern banks of the river Rhine. After a short bus trip we reached the trail head of our hiking expedition. The Siebengebirge consists of numerous volcanic necks of basanite, alkaline basalt, latite and trachyte formed during intraplate volcanism between ~27 Ma and ~20 Ma. Also, there is an enigmatic volcaniclastic succession, locally referred to as „Trachyttuff“ and previously inferred to represent a succession of pyroclastic fall deposits and ignimbrites. However, new research demonstrates that at least a significant portion of the sequence was generated by sublacustrine volcanic eruptions and we engaged in lively discussions regarding the lithological evidence.

The Siebengebirge hills are covered by dense forests providing a natural reserve for many endangered plant and animal species. Due to conservation issues the group was limited to one hammer, which was absolutely sufficient to supply everybody with ample specimens to investigate.

During our 10 km hiking trip we enjoyed a full day of sunshine (the first of the entire Goldschmidt Meeting!), visited two ruins of medieval castles, passed scenic view of the Rhine valley, stopped for afternoon tea (and Kölsch...) at an Inn in the forest and finally reached our evening destination: The Drachenfels (dragons hill) vineyard. Here, an outdoor feast consisting of a local pork specialty (Spiessbraten) and several rounds of tasting of the local grape products provided the background for some lively entertainment and reflections. I remember that someone promised to organize a similar event for Vancouver 2008...