Reappraisal of the volcanic source of the Rocourt Tephra, a widespread chronostratigraphic marker aged ca. 78–80 ka in Western Europe

The Rocourt Tephra (RT) is a widespread stratigraphic marker distributed in Germany, Belgium, and the Netherlands, where it is used for stratigraphic correlations, dating of host sediments and of Middle Palaeolithic archaeological assemblages, sometimes including Neandertal remains. Its age is estimated between 78 and 80 ka. This tephra has been linked to the West Eifel Volcanic Field in Germany, but its corresponding source volcano is unknown. Such a discovery would make it possible to confirm or challenge the age of the tephra, because this source volcano could be dated by various methods. It would also be possible to know the composition of the magma, which cannot be determined from the altered clasts of the tephra, as well as the original mineralogical composition, thereby strengthening the validity of the marker by providing more distinctive data. Two Eifel monogenic volcanoes have been cited as potential sources, the Dreiser Weiher and the Pulvermaar, due to their large sizes and broadly similar compositions. A study of the tephra layers from these volcanoes was carried out to compare their mineral compositions with that of the Rocourt Tephra. Based on new analytical data on the composition and magmatic trends of pyroxenes, it is concluded that neither of the two volcanoes can be the source of the RT.