Continental climate archive – from the Eifel into the world.
Written by Prof. J.F.W. Negendank

Seit 30 Jahren hat sich Negendank Arbeitsgruppe mit den Sedimenten der Maartrichter beschäftigt

These studies started with the Eifel, in which these volcanic craters were first given the name “maar” by Steininger in 1819, to which Thienemann added the definition of eutrophic and oligotrophic (nutrient-rich and nutrient-poor) waters in 1916. As well as the water-filled maars there are also what’s known as dry maars, like the Eocene maar at Eckfeld, a rich fossil site whose tropical climate is as world-famous as the Messel pit fossil site and which inspired the establishment of the Maar Museum in Manderscheid. The more recent maars, on the other hand, are part of the West Eifel volcanic activity (700,000 years old), and the water-filled maars are considered to be the most spectacular ever recorded. They contain layers and layers of diatom gyttja (eutrophic) and siderite laminate (oligotrophic) laid down in the Holocene epoch (current interglacial age), which made it possible to create an annual calendar for the last 23,000 years.

Using this, climate archives were created on the continents – where people were actually living – that enabled scientists to document the chronological, environmental and climatic indicators including a definition of years and ages; as this was in the style of a calendar it represents a document in the form of a quasi-meterological series of measurements. As it was not possible in the maar lakes in the Eifel to get a complete varve profile over the whole 23,000 years, maar lakes around the world in the different climate zones on the Eurasian continent were drilled (image 1) with similiarly fascinating results to the Eifel, but gathering data on a period around 130,000 years ago, the last glacial period and the last interglacial period, what is known as the Eemian. For example, there is the Lage Grande di Monticchio maar lake in Italy, where analysis of the varves enabled us for the first time to calculate the length of an interglacial period, around 17,700 years. The current interglacial period in which we live has lasted for 11,600 years so far (Eifel varve chronology). The Sirocco study group (University of Mainz) has previously drilled dry maars and extended the sequence for the Eifel into the Eemian period; here the published chronology does not represent varve chronology but relies on “wiggle-matching”. Extracting lake sediment from the water-filled maars is done using drilling techniques (image 2) with the help of a Usinger-corer that have been perfected over the last 30 years in parallel with research, so that now at a depth of 20-40m it is possible to extract around 100m of sediment with precision. In order to create a reliable chronology it is necessary to assess at least 3-4 overlapping sediment cores, from which thin overlapping sections can be created. Using a microscope, layers in these cores from individual years and periods – varve by varve – can be identified, correlated and assessed. The research is multi- and interdisciplinary. It took around 50 scientists from different disciplines 15 years to create the only varve chronologies for the last 130,000 years (Eifel and Monticchio) (e.g. the following study groups: Litt / Bonn; Usinger / Kiel; Schleser / Jülich; Huntley / Durham).