Der Laacher-See-Vulkan und das mittlere Lahngebiet. Geoarchäologische Untersuchungen zu den Auswirkungen des Vulkanausbruchs auf Mensch und Umwelt vor 12.900 Jahren
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Philipps-Universität Marburg
Abstract
This study deals with the effects of the Laacher See volcano on humans and the environment in the distal depositional areas of the central Lahn region. The approach is based on the following questions:
- Which processes led to the formation of the profiles that were discovered, i.e. which impact do the LST layers possess on the drainage behavior of late-glacial, near-natural streams in the middle Lahn area?
- Is it possible to reconstruct a chronological sequence from the different stratifications, i.e. can these deposits be attributed to a longer or shorter formation process?
- Are there any indications that the fallout had an effect on humans at that time?
Methods of soil science, mineralogical analyses, facies-architectural-element analyses and stratigraphic analyses, which are used in archaeology, served as the basis for investigating these questions.
In order to be able to reconstruct the formation process of the palaeochannels, a total of 58 samples were examined in the laboratory for the grain size composition, organic matter and water content. In combination with the identification of architectural elements, the individual fluvial processes of the channel in Argenstein could thus be identified.
The investigations showed that the LST is largely responsible for disturbing the discharge of both the palaeochannels in Argenstein and the channel observed in Niederwald. While the channel in Niederwald silted up completely in the case of the fallout, the geoarchive in Argenstein often shows massive deposits caused by denudation processes, which affected the discharge, the transport vessels and thus the entire channel structure. As a result, recurring sedimentation occurred at times due to the eruptions.
The resulting deposits show both phases of short formation processes - such as massive deposits of the LST - as well as longer-lasting processes - such as the occurrence of stillwater sediments.
To support the stratigraphic interpretation, more than 400 measurements of the magnetic susceptibility were carried out. The measurements serve to delimit the deposited pyroclastics in the profiles and boreholes. This made it possible to gain detailed knowledge of the individual strata. In addition, the occurrence of LST-stemmed hornblende fragments could be detected by REM analysis. This made it possible to determine the time period of the channel structures that were recorded, which can therefore be dated to the late Alleröd.
The environmental conditions observed also made it possible to draw conclusions about the impact of the LST on humans of the Late Palaeolithic time period.
The comparison with the current state of research suggests that the area of the middle Lahn valley was not a life-friendly environment for the local population during and for a while after the fallout. The numerous sites buried under LST and the chain of events that occurred as a result of the volcanic eruptions underline this approach.
The discovery of Late Paleolithic artifacts above LST rules out a complete decline of the ridge-top circle. However, a migration of hunter-gatherers out of the middle Lahn area seems extremely plausible.
Overall, the Alleröd Interstadial represents one of the most interesting periods in the past. The climate change, the change in the channel structures as well as the change in hunting techniques and the shift towards microlithics characterize this time period. The effects of the Laacher See volcano can be traced especially in geoarchives and are used by geoarchaeologists to reconstruct human-environment interactions.
The investigation and interpretation of the geoarchives presented here and the associated effects on humans can also contribute to modern disaster research. In particular, studies on past volcanic eruptions can provide information on the possible consequences for humans and the environment, which can in principle be applied to present-day eruptions. For example, past volcanic eruptions, earthquakes and floods are not different from those in the present, especially as the Laacher See volcano does not yet appear to be extinct.
Keywords
paleo channels, Fluvialmorphologie, Paläorinnen, Laacher-See-Vulkan, Fluvial morphology, Laacher Lake volcano