CRC 1266 - Scales of Transformation

Phase 2 - Research activities 2020-2024


F2: Socio-environmental Transformations and Interdependencies


 

Research activities 2020/21


Paleoecological re-evaluation of sediment sequences from the Duvenseer Moor 

The long-term archaeological excavations for the Mesolithic in the Duvenseer Moor, most recently as part of sub-project B2, were accompanied several times by palynological investigations. As part of this, numerous sediment profiles from the shoreline area of the former lake were processed. So far, however, the results of the pollen analyses have mainly been used for archaeological purposes, e.g. for the pollen stratigraphic classification of the Mesolithic dwelling places or for the clarification of the stratigraphy. However, the paleodata were never considered from a holistic perspective. This is now being done within the framework of the F2 sub-project with the aim of obtaining as precise a picture as possible of the landscape transformations in the course of the Mesolithic and beyond.

Coring campaign at sites of the Wartberg culture in Hesse

The analysis of drill cores from natural archives aims at providing information about the former use of the settlement area and contributing to the reconstruction of local environmental conditions. The focus is on the question of how far these environmental conditions have influenced local settlement behavior. As part of the cooperation with the subproject D2, a drilling campaign took place in the Wetterau and the Amöneburg Basin in the Hessian low mountain range in October 2020. One of the drilling sites was located in the catchment area of ​​the late Neolithic flatland settlement of the Wartberg culture near Schröck, which was fortified with a double ditch. The drilling yielded two sediment sequences with embedded organic layers that appeared promising for palynological analysis. When examining the deposits, however, it was found that the Neolithic section was missing due to a hiatus in the sediment. Unfortunately, this is a common phenomenon, as the region's expert Dr. Astrid Stobbe from Frankfurt confirmed. Other locations, for example at the foot of the Alteburg near Dauernhaim, have been prospected and will be examined for their suitability for detailed analyses from the 3rd millennium BC. checked. During the excavations at Schröck planned for the summer of 2021, on-site samples will be taken from the Wartberg settlement, which will contribute to the interpretation of the findings.

Near- and on-site investigations on the Neolithic 

In the context of the archaeological investigations of subproject C1 in the Dümmer area, Lower Saxony, prospecting drillings were carried out in summer 2021 together with colleagues from the Lower Saxony State Office for Monument Preservation and the nature conservation officer of the Diepholz district. They concerned the immediate vicinity of the Hunte 4 excavation area and selected raised bogs in the wider area. Subsequent pollen analyzes of selected horizons of the prospecting boreholes enabled the potential for environmental reconstruction for the Neolithic to be determined. Other ongoing work includes the analysis of on-site profiles of Neolithic settlement sites. In addition to the previously mentioned Hunte 4 site, another settlement site in Schönhagen, Schleswig-Holstein, from the 3rd millennium BC is being investigated. In addition to references to local activities, the reconstruction of the genesis of the sediments investigated also contributes to the understanding of the sites. 

Near- and on-site investigations on the Bronze Age in the vicinity of the Woseriner See

In addition to archaeological investigations of a Bronze Age settlement near Dobbin, Mecklenburg-Western Pomerania (cf. subproject D3), near- and on-site analyzes for the reconstruction of the environmental history are carried out. In order to identify suitable archives in the vicinity of the archaeological site, prospecting drillings were carried out at the end of the last project phase (October 2019) (Fig. 6-8). Up to 6 m thick Holocene deposits were found in a muddy depression northwest of the excavation area. At this point, several core series were drilled in spring 2020 with a Usinger drill, a coring system developed in Kiel. The ongoing investigations on the sediments include the analysis of pollen and non-pollen palynomorphs (NPP), geochemical analyzes (pXRF), determination of ignition loss and radiocarbon dating as well as micromorphological analyses on thin sections. Individual samples from archaeological layers and structures of the Bronze Age settlement are also examined by pollen analysis.

Car in landscape with 2 people and excavation equipmentFig. 1: Drilling campaign in a bog near Dobbin

Synchronization of high-resolution geo-archives by means of cryptotephral layers 

Due to the Covid 19 situation, the prospections planned for the 2nd phase for off-site archives in other investigation areas (e.g. Denmark, Poland) are currently not possible. The ongoing work on off-site archives is therefore limited to the analysis and evaluation of existing profiles. This includes the search for traces of former volcanic eruptions in the well-dated (AMS) laminated lake sediments of the Woseriner See (see link to phase 1 Poggensee). The microscopic detection of individual volcanic glass particles, so-called cryptotephra, and the subsequent analysis of their geochemical fingerprints allow the reconstruction and dating of former volcanic eruptions. Due to the continuous, high-resolution analysis of various proxies, the Woseriner See is one of the best-studied locations in Central Europe and thus makes an important contribution to the tephrochronology of this area. The next step is to search for and identify Kryptotehpra in archives that were previously difficult to date. These include, for example, sediments from the Baltic Sea and profiles from Brandenburg, which have already been well investigated by pollen analysis, for which conventional dating using radiocarbon dating is difficult. In the context of the SFB1266, this approach promises the possibility of an extended supra-regional, chronologically precise comparison of the history of vegetation and the identification of land use patterns from the Neolithic to the Bronze Age along the planned investigation transect.

microscope viewFig. 2: Tephra Particel from Lake Woserin, diameter 30 µm

Reconstruction of climate and environmental development 

The combination of microscopic thin section analysis and geochemical measurements on annual layered lake sediments enables a highly precise reconstruction of the climate and environmental development of the lakes during prehistoric settlement phases. The thin section analyzes enable a continuous seasonal resolution of the sedimentation processes and also form an important basis for the chronology (Fig.xx). The thickness of the sediments deposited in spring, summer, autumn and winter is measured. The components of the layers are documented in a standardized way on the basis of ordinal scaling. Geochemical measurements on mixed sediment samples provide comparable, temporally high-resolution continuous data for the lake and between different lakes on a ratio scale (e.g. element content ... g * cm-2 * a-1). The geochemical measurement data are used to calibrate the microscopic estimation scale.

Graphic of a core section and a microphotoFig.3 Photograph of a core section of the warned sequence of the Belauer See (left) and a microphoto of a thin section of the sequence (crossed polarizers, seasons indicated)

The results of the detailed analysis of the preserved sediments of the Belauer See show characteristic changes during the Bronze Age (Fig. Xy.) Which partly reflect the archaeological and pollen-analytically detected transformations of the Bronze Age (Project D3). The overall thickness of the varves reflects the bio-productivity of the lake. Discrete phases of lesser varve thickness coincide with known paleoclimatic phases. The almost continuous formation of winter shifts is remarkable. These occur in the surface sediment only in years with at least 50 ice days or an average temperature from December to February of below 0 ° C. This shows that the winters of the Bronze Age were considerably more pronounced in northern Germany, which indicates a more continental climate regime. Discrete phases with particularly thick winter layers coincide with generally lower varve thickness and therefore lower aquatic bioproductivity. The analysis of the thin sections shows an increase in the occurrence of carbonate precipitation in spring locations from around 1250 BCE. In addition to higher wind speeds in the Bronze Age springs, this result can also point to the opening of the landscape (clearing). The latter would increase the exposure of the lake to the attacking wind and therefore also lead to increased carbonate precipitation under turbulent circulation conditions.

Graphic of development of the valve thicknessFig. 4: Development of the varve thicknesses in the Bronze Age section of the sequence of the Belauer See (left), development of the winter layers (middle) and the development of spring layers with pronounced carbonate precipitation (right), black line - 10 years running mean in each case.

Geochemical analyses of the varved sediments also show a characteristic variability, which can be explained on the one hand by paleoclimatic conditions and on the other hand by social transformations (project D3) (Fig. Yy).

Graphic of selected element contents and element ratiosFig. 5. Selected element contents and element ratios of the sediment of the Belauer See; black line 10 point running mean 

The Bronze Age transformation of the landscape is reflected by changes in the sediment composition. Analyzes of the likewise laminated lake sediments of the Woseriner See will follow.

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