Search Results (6)

Recent technological advancements in spectral imaging core-scanning techniques have proved to be a promising tool to study lake sediments at extremely high resolution. We used this novel analytical approach to scan core AU3 of the Pleistocene Auel maar, Western Germany. The resulting ultra-high-resolution RABD₆₇₀ spectral index, a proxy for the lake’s primary production, shows an almost complete succession of Greenland Interstadials of the NGRIP ice core chronology back to around 60,000 years. Using the ELSA-20 chronology and its anchor points to the NGRIP record as a stratigraphic basis, we were able to compare and fine-tune prominent climate signals occurring in both regions. This in-depth correlation yields strong evidence that the climates of Greenland and Central Europe were not only strongly coupled on timescales of stadials and interstadials but even on multidecadal scales, showing prominent climate cycles between 20 and 125 years. As climate changes in these regions were ultimately driven by variations in the North Atlantic meridional heat transport, their strong coupling becomes most apparent during cold and arid intervals. In contrast, longer-lasting warmer and more humid phases caused the activation of various regional feedback mechanisms (e.g., soil formation, forest growth), resulting in more complex patterns in the proxy records. Full article

The analysis of tephra layers in maar lake sediments of the Eifel shows 14 well-visible tephra during the last glacial cycle from the Holocene to the Eemian (0–130,000 yr b2k). These tephra were analyzed for their petrographic composition, which allows us to connect several tephra to eruption sites. All tephra were dated by application of the ELSA-20 chronology, developed using the late Pleistocene infilled maar lake of Auel and the Holocene lake Holzmaar (0–60,000 yr b2k). We extend the ELSA-20 chronology with this paper for the millennia of 60,000–130,000 yr b2k (ELSA-23 chronology), which is based on the infilled maar lake records from Dehner, Hoher List, and Jungferweiher. The evaluation of the tephra from the entire last glacial cycle shows that all 14 tephra were close to interstadial warming of the North Atlantic sea surface temperatures. In particular, phreatomagmatic maar eruptions were systematically associated with Heinrich events or C-events. These events represent times of warming of the Southern Hemisphere, global sea level rise, and CO₂ increase, which predate the abrupt interstadial warming events of the Northern Hemisphere. This synchroneity indicates a physical relationship between endogenic and exogenic processes. Changes in the lithospheric stress field in response to changes in continental ice loads have already been suggested as a potential candidate to explain the exogenic forcing of endogenic processes. The chronology of volcanic activity in the Eifel demonstrates that intraplate mantle plumes are also affected by the exogenic forcing of endogenic processes. Full article

We analyzed mineralogical characteristics, and major as well as rare earth element concentrations, from a cryptotephra layer in sediments of the infilled maar of Auel (Eifel, Germany). The results of detailed geochemical analyses of clinopyroxenes and their glassy rims from the Auel cryptotephra layer showed that they are similar to those from the thick Campanian Ignimbrite tephra occurrence in a loess section at Urluia (Romania). Both tephras show idiomorphic green clinopyroxenes and formation of distorted grains up to millimeter scale. The cryptotephra in the Auel core has a modelled age of around 39,940 yr b2k in the ELSA-20 chronology, almost identical to the latest ⁴⁰Ar/³⁹Ar dates for the Campanian Ignimbrite/Y-5 (CI/Y-5) eruption. These observations suggest that parts of the CI/Y-5 ash cloud were transported also northwestward into Central Europe, whereas the main branch of the CI/Y-5 ash plume was transported from southern Italy towards the NE, E, and SE. Based on pollen analyses, we conclude there was no direct effect on vegetation from the CI/Y-5 fallout in the Eifel area. Trees, shrubs, and grasses remained at pre-tephra-airfall levels for roughly 240 years, but changed around 39,700 yr b2k when thermophilic woody plants (e.g., Alnus and Carpinus) disappeared and Artemisia spread. This change in vegetation was well after the Laschamp geomagnetic excursion and also after the GI9 interstadial and quite probably represents the onset of the Heinrich Event 4 (H4) cold spell, when climatic conditions over the North Atlantic, and apparently also in Central Europe, deteriorated sharply. Full article

Seven published and four new pollen records from well-dated sediment cores from six Pleistocene and Holocene maar structures located in the Eifel, Germany, are combined to a pollen stack that covers the entire last 132,000 years. This stack is complemented by new macroremain data from one additional sediment core. The pollen data included into the stack show consistently that the Eifel was covered by a dense forest during the Eemian, early Marine Isotope Stage (MIS) 3, and the Holocene. While other European records indeed indicate a warming, the early MIS 3 fully developed forest remains a unique feature in central European pollen records. Comparison to orbital parameters and insolation hints to warm and humid, however, not fully interglacial conditions, which are also visible in speleothem growth throughout Europe. With the cooling trend towards the glacial maxima of MIS 4 and 2, tree pollen declined, with recovering phases during MIS 5c and 5a, as well as during all MIS 3 interglacials. During the colder stadials, steppe vegetation expanded. For MIS 5 and 4, we defined six new landscape evolution zones based on pollen and macroremains. Full article

We present a record of pollen and spores of coprophilous fungi from a sediment core from Auel infilled maar, Eifel, Germany, covering the period from 42,000 to 36,000 yr b2k. We can show that vegetation cover was dominated by a boreal forest with components of steppe and cold-temperate wood taxa. The proportion of wood taxa was higher during interstadials, whereas steppe-vegetation became more prominent during stadials. During Heinrich stadial 4, temperate taxa are mostly absent. Spores of coprophilous fungi show that megaherbivores were continuously present, albeit in a larger number during stadials when steppe environment with abundant steppe herbs expanded. With the onset of Greenland stadial 9, forests became more open, allowing for steppe-environment to evolve. The shift in vegetation cover coincides with the highest values of herbivore biomass at the time that Neanderthal humans demised and Anatomically Modern Humans most probably arrived in Central and Western Europe. Megaherbivore biomass was a direct consequence of vegetation cover/availability of food resources and thus an indirect consequence of a changing climate. Herds of large herbivores following suitable (steppe) habitats may have been one cause of the migration of AMH into Europe, going along with their prey to productive hunting grounds. Full article

We present a timeseries of flood and slumping phases in central Europe for the past 65,000 years from event layers in sediment cores from infilled Eifel maar basins (Germany). Palynological, petrographic and organic carbon (chlorins) records are used to understand the precise timing of these events. Periods of increased flood activity seem to coincide with Heinrich stadials in marine sediment records, which are associated with cold and more arid climate conditions, indicating a vegetation response within the maars’ catchment areas. This multi-proxy correlation reveals prominent slumps at different maar sites during Greenland Stadial (GS) 12. The stratigraphy is based on sediment records from the Auel infilled maar and we thus call this event Auel Cold Event (ACE). Frozen and fractured sediment packages within the slump suggest deep frost or permafrost conditions for the region during the stadial. The results agree well with sediment archives and archeological sites across Europe that report severely cold and arid conditions for the stadial. This supports the assumption that GS12 was indeed one of the coldest periods of the last glacial cycle rather than the Heinrich stadials. Based on our age model, the ACE occurred at 43,500 yr b2k (years before the year 2000), which coincides with the initial weakening of Earth’s magnetic field strength prior to the Laschamp geomagnetic excursion. Full article