Matthias Leopold

A ground-penetrating radar survey of late Holocene fluvial sediments in NW Namibian river valleys: characterization and comparison

Fine-grained terraces and coarse-grained channel fills that represent episodes of late Holocene valley aggradation are used as geoarchives for palaeohydrological reconstructions in many arid regions of the world (e.g. southwestern USA, Australia, Israel and the Namib Desert). In Namibia, previous work on the sediment texture and facies of these valley fills has led to diverse interpretations of the depositional environment, including river-end, palaeoflood and floodout. Here we show, using ground-penetrating radar (GPR) profiles across four complex river channels to image sedimentological and stratigraphical structures, that the GPR images can be grouped into eight ’radar facies’ (reflection patterns). A combination of radar facies analysis and groundcheck (exposures, boreholes) has been used to interpret the radar profiles. By considering the geomorphological–sedimentological features and age determinations of the fluvial deposits described by earlier researchers and supplemented by our own investigations, we explain the late Holocene fine-grained terraces and coarse-grained channel fills as deposits accumulated during floods. Although the GPR results alone cannot conclusively resolve the fine-grained terrace deposits either as river-end or as slackwater accumulation, the novel combination of GPR, geomorphological findings and results from the literature provides evidence for our interpretation.

Reconstruction of the old cultural surface of a Bronze Age Settlement – An example for a multi-methodological interaction of Soil Science and Archaeology in Southern Germany

During the excavation of a Late Bronze Age settlement at Mintraching (near Regensburg, Germany) the on-site pedological and geomorphological settings were studied in order to collect data regarding the palaeopedological and geomorphological conditions of the settlement area, as well as to elaborate further on the former Bronze Age surface. Pedological and geophysical field methods in combination with laboratory analyses were used in close proximity to the archaeological excavation site. Studies about the terrace stratigraphy of the river Danube and associated soil profiles provided data to determine the altitude of the ancient surface. This assisted in calculating the altitude of the former surface of the highest prehistoric building found in Bavaria to date. Since Bronze Age, a minimum amount of 80 - 100 cm soil loss referring to the original Holocene surface could be calculated. Furthermore, the accumulation history of black sediments distributed nearby is described. The black sediments, which are rich in organic matter, accumulated in an old palaeo channel close to the settlement since the Neolithic period. The deposits are not the remnants of a Tschernosem soil as previously thought. Erosion and deposition of the black material give an indication of anthropogenic activities like clearing and farming in the close vicinity of the former settlement area which was located next to an old water filled channel.