*3.1. Sedimentological Record*

The measured sediment properties of the section examined allow a detailed description of the layers depicted in Figure 2. Layer A is characterised by a water content of c. 5%, an average SOC concentration of around 1%, acidic pH values (top A: < 3.5, basis A: 4.5), and high concentrations of silt compared to the other layers (Figure 5). At the top of layer B (sublayer 5), a peak of water content is visible (c. 10%). Layers B and D show strong variation between their individual sublayers, averaging at around 5% water content, acidic pH values between 3.5 and 4.5, and low SOC concentrations (<0.2%). The dark, thin horizontal layer C shows a peak in water content (c. 10%) and a slight increase of silty material and SOC content compared to the surrounding materials (Figure 5).

**Figure 5.** Sedimentological record of SD17P1 (layers A, B, C and D). Sediment colour and texture [69] as documented during fieldwork, location of samples, and respective results of the sediment analyses performed. Centred log-ratio (clr) transformed contents of relevant elements measured with the p-ED-XRF device.

During pre-processing of the p-ED-XRF data, we excluded several elements due to their insignificance or erroneous measurements. The following eight elements showed valid measurements and were processed: Zr, Zn, Fe, Ti, Ca, K, Si, and Al. Concentrations of these elements are heterogeneous in the lower parts of the examined profile (layers B, C, D), while layer A repeatedly shows continuous trends of element concentrations from its top to its bottom (Figure 5).
