Determining carbon storage of a complex peat stratigraphy using non– and minimal-invasive geophysical prospection techniques (Verlorener Bach and Loosbach valleys, southern Germany)

This study investigates the stratigraphy and carbon storage of the Verlorener Bach and Loosbach valley fills, of the Alpine Foothills in Bavaria, using a combination of electromagnetic induction (EMI), electrical resistivity tomography (ERT), direct push electrical conductivity sensing (DP-EC) and drilling cores. We identified three distinct stratigraphic units, with Unit I consisting of gravel deposits, Unit II comprising Holocene peat layers, and Unit III containing redeposited carbonates and overbank deposits.

The integration of EMI data enhanced spatial resolution, while ERT data provided detailed insights into the thickness and distribution of these units. Correlating EMI-based apparent electrical conductivity values with stratigraphical data enabled the creation of a validated 3D model of sediment thickness. This approach revealed an inverted relief process where non-organic Unit III sediments remain elevated as surrounding organic-rich sediments shrink upon oxidation.

Additionally, geochemical analyses estimated the Total Carbon (TC) and Total Organic Carbon (TOC) content for Unit II, totaling 43 kt of TC and 35 kt of TOC across the entire 15-hectare study area. The high carbon storage in peatlands is attributed to the thickness of peat layers and sustained water saturation, preventing degradation. However, potential reductions in groundwater levels could lead to peat decomposition and carbon release.

This study demonstrates the effectiveness of integrating EMI, DP-EC and ERT data for stratigraphic analysis, providing a comprehensive understanding of spatial sediment stratigraphies and carbon storage in the study area. Our study demonstrates that it is possible to use geophysical prospecting methods not only to characterise surface sediments but also those located deeper in the ground. This allows for the analysis of both intact fen peats in terms of their carbon storage, as well as those that are no longer intact but buried.