Direct push tools in the frame of geoarcheological site investigation in floodplains and wetlands

Jörg Hausmann ^a,b , Christoph Zielhofer ^b, Peter Dietrich ^a,c, Stefanie-Berg-Hobohm ^d, Robert Heymann ^a,b, Ulrike Werban ^b, Lukas Werther ^e

^a Department of Monitoring and Exploration Technologies, UFZ – Helmholtz Centre for Environmental Research, Leipzig
^b Chair of Physical Geography, Leipzig University
^c Eberhard Karls Universität Tübingen
^d Bayerisches Landesamt für Denkmalpflege
^e Department of Prehistory and Early History, Friedrich-Schiller-Universität Jena

Geoarchaeological trenching techniques in floodplain and wetland environments are challenging due to the impact of groundwater inflow and highly unstable trench edges. Alternatively, classical driving core applications often come along with the contraction of organic layers and bias in height accuracies. Here, we present the application of direct push techniques for geoarchaeological studies in environments with high groundwater tables, especially when high-resolved parameterization of the near surface is of broad scientific interest.

Two of these direct push techniques, are electrical conductivity logging (EC) and the measurement of soil colors (SC) in unconsolidated sediments throughout depth. These provide proxy information about layer structure, texture and organic carbon.

Here we show that direct push techniques – yielding high-resolved information on vertical layer patterns are a promising tool for such tasks. The speed of investigation allows for obtain a large data set by means of vertical resolution and lateral profiling. We exemplary provide first results of a densely investigated cross-section, which is part of Charlemagne’s summit canal, an early medieval hydro-engineering project bridging the Central European Watershed.

We compare the obtained high-resolved probings to core samples and discuss transfer options from multiple one-dimensional logs towards generation of two-dimensional cross-section. In this context, we recognize insitu obtained soil colors and electrical conductivity as descriptive proxies for site characterization. Given the cost and time effectiveness of such tools, site information was grown rapidly, compared to less densely performed drillings, which require a high effort for post-analysis.

We conclude that direct push technologies, therefore, are especially promising for geoarchaeological applications in floodplain and wetland environments, owing to the broad variety of available sensors and probes, their minimally invasive nature, and the high-resolution data they provide (geophysical, geotechnical, hydrological, geochemical).