Multi-proxy analysis of colluvial deposits: Archaeopedological reconstruction of land use practices in southwestern Germany

Abstract

This thesis aims at achieving a better understanding of past human-land interaction by following an interdisciplinary approach, which includes the (sub-)disciplines of soil sciences, archaeology, archaeobotany and archaeozoology. The decipherment of past human-land interaction entails the identification of resources that were significant for the cultural development of prehistoric societies in southwestern Germany. The theoretical superstructure of this thesis is based on the Favor-Disfavor dichotomy, which classifies landscapes as ‘favourable’ and ‘unfavourable’ based on its suitability for agricultural purposes. The application of the concept of ResourceCultures and the framework of Complex Adaptive Systems attempts to refine this one-dimensional interpretation of past human-land interaction. For this study, multi-proxy analyses of multi-layered colluvial deposits in the area surrounding prehistoric settlements at the Baar, in the Hegau (both favourable) and in the Westallgäu (unfavourable) are performed. These multi-proxy analyses are utilized to reconstruct the colluvial deposition history based on ages from optically stimulated luminescence dating (OSL) and radiocarbon (AMS 14C) dating. The resulting colluvial chronostratigraphy is then synchronized with the local archaeological record. Pedogenic properties, such as the soil organic carbon (SOC) and calcium carbonate (CaCO3) content, as well as pH values, grain size distributions, X-ray fluorescence (XRF) and pedogenic iron oxides are analysed to support the (chrono)stratigraphy of colluvial deposits. In this context, the identification of former land surfaces, based on varying intensities of soil formation and weathering processes, is of major interest. The investigation of soil microstructure is applied to identify human permeation of colluvial deposits (e.g., accumulation of charcoal, identification of plough marks). Land use proxies such as the analysis of phytoliths, charcoal spectra, black carbon (BC), polycyclic aromatic hydrocarbons (PAHs), urease enzyme and microbial activities, faecal biomarker (e.g., sterols, stanols and stanones) and heavy metals from colluvial samples are used to gain insights into prehistoric land use practices. The local archaeological record, as well as offsite pollen data, complement the dataset. At the prehistoric site of Fürstenberg, the analysis of colluvial deposits provide information on land use practices, such as wood procurement and livestock husbandry, between the Late Bronze Age and the Early Iron Age. At the Middle Bronze Age (MBA) settlement site of Anselfingen, the sedimentation history confirms the beginning of soil erosion during the MBA. From the MBA colluvial horizons, land use practices, such as arable farming (e.g., ploughing, manuring and cultivation of cereals), forest management (wood procurement and forest pasture) and livestock husbandry, can be reconstructed. The land use practices are complemented by the investigation of onsite charred archaeobotanical remains and animal bones from archaeological structures. Archaeological structures further contribute to a detailed understanding of MBA land use practices in the Hegau. Offsite pollen data, from nearby peat bogs, allows for a regional interpretation and suggests that the identified onsite and near-site vegetation change and land use practices were characteristic for the north-western Alpine foreland. At the two sites in the Westallgäu, land use areas are attributed to nearby MBA settlement sites. Based on the depositional history, the beginning of soil erosion is dated to the MBA, with up to 90 cm of eroded soil column within few hundreds of years. Land use practices, such as livestock husbandry and heavy metal processing, appear to be likely at the Westallgäu sites. The acquired data support the interpretation of colluvial deposits as archives for the reconstruction of past land use practices in the areas surrounding prehistoric settlement sites. The data also show that, especially during the Middle Bronze Age in the Hegau, an elaborated land management was established to maintain the landscape and the subsistence economy. The results derived from the colluvial deposits and the local archaeological records of the two sites in the Westallgäu suggest that settlement communities must have already existed in the MBA, even if these sites are considered less favourable than sites in the Hegau and at the Baar in terms of agricultural practices. In summary, the multi-proxy analysis of colluvial deposits contributes to better understanding of prehistoric land use practices in the areas surrounding prehistoric settlements. Land use proxies from specific colluvial horizons, that can be correlated to the local archaeological record and offsite pollen data, provide in-depth insights into past human-land interactions in southwestern Germany. The ResourceCultures concept and Complex Adaptive System framework provide a more detailed understanding of prehistoric farmers and their efforts to maintain subsistence economy.