We distinguish 7 tephra layers during the last 60,000 years, which are visible in all cores. The eruption of these marker tephra must have been very strong and changing wind directions during the weeks of a maar eruption has apparently distributed the tephra over the entire Eifel as cm-thick layers. It is quite likely that small eruptions can have produced additional ash layers, which form cm to mm-thick layers at distances of more than a few kilometers from the eruption site. Thin minerals of dark layers are numerous at all times and can be analyzed on the petrographic thin sections, but it is sometimes difficult to distinguish mm-thick airfall from reworked ash particles within the maar crater.
At the moment we distinguish only the 7 marker tephra layers, which have a typical sediment petrography. This petrographic characterization is a new method developed by Förster & Sirocko (2016) and uses 10 different minerals from the bedrock and the eruption itself. The method thus does not only characterize the magmatic processes, but also the regional geology of the bedrock at the site of eruption.
The Laacher See Tephra (LST) at 12,880 yr b2k is found always below the Holocene pollen and is characterized by abundant sanidine grains of more than 40%. However, the pumice of the LST is easily transported by running water and, thus, the LST is often not only an airfall, but washed into the lake together with reddish and greyish sandstone fragments from the river catchment that drain into the maar lake.
We do not observe any distinct tephra during the last glacial maximum, but many thin layers of volcanic minerals at the base of LGM turbidites, which transport volcanic debris from the tuff wall into the maar. It remains to be analyzed if thin tephra from distant airfall may be hidden in the glacial sections. We have, however, quantified a layer of dark minerals with a geochemical composition quite similar to the Eltville Tephra (EVT) (Förster et al. 2019), which is well known from LGM loess profiles. ELSA-20 dates the EVT at 24,708 yr b2k.
A very well distinguishable tephra occurred then at 28,100 yr b2k, between the interstadials GI4 and GI3. The high pyroxene content associates perfectly with the composition of volcanic minerals of the Wartgesberg Tephra (WBT), which was dated also by Ar/Ar to the same age. The complex structure of the WBT at the site of eruption is also visible in the sediments as three distinct subtephra of the WBT. It cannot be distinguished if other smaller eruptions, contemporary with the WBT cluster, are hidden in the thick WBT layers. The same petrographic composition as the WBT is prominent in a tephra at 30,300 yr b2k, which cannot be related to a specific site of eruption (UT1).
A sanidine rich tephra at 40,370 yr b2k fits nicely the complex mineral composition of the Dreiser Weiher Tephra (DWT), where sanidines and olivine occur together in the same tuff layers around the site. The eruption mixed apparently proportions from the upper mantle with sanidines, formed in the lower crust, and bedrock fragments from the upper crust. The tephra is thus visibly zonated with grey and dark layers.
A tephra with an ELSA-20 age of 47,330 yr b2k is petrographically comparable to the tuff around the Meerfelder Maar, but the sediment petrographic fingerprint is not very specific. The eruption of the Meerfelder Maar has been also dated by 14C analysis to 43,000 BP (Schaber & Sirocko 2005), which is an additional argument for the assignment of this tephra to the Meerfelder Maar Tephra (MMT).
The next marker tephra is the eruption of Auel, which we analyze at the depth of cores AU2, AU3, AU4, and which we find with the same petrographic composition in the nearby Dehner Maar and Jungferweiher sediment cores at 59,130 yr b2k.
The tephra with the most distinct petrographic fingerprint is, however, a layer, with up to 5% of leucite, which we only observe once during the last 130,000 years. Förster & Sirocko (2016) called it accordingly Leucite Tephra. Leucites have been reported up to now only from the tuff wall around the Schalkenmehrener Maar, and the idiomorphic grains from the tuff wall and lake sediment are indeed most similar. We regard the Leucite Tephra to represent the Schalkenmehrener Maar Tephra (SMT). This dates the eruption time of the Dauner Maar Group (Schalkenmehrener Maar, Gemündener Maar, Weinfelder Maar) to have occurred at around 65,000 yr b2k. A precise age will be obtained from the varve counting of the MIS4 section of the Dehner Maar cores.