*3.3. Sedimentology*

Core data provide the ground-truth information needed to calibrate/confirm geophysical data with localized information. The cores help define sedimentary features of the electrically resistive point-bar body, related channel-fill deposits and surrounding electrically conductive overbanks. All cores reveal that the deposits were intensely reworked by agricultural activities down to 80 cm below ground. Note that this fact may pose significant limitations to remote-sensing interpretation that is forcibly limited to surface images. Reworked deposits are dark brown and consist of very fine sand with a variable amount of mud. Point-bar deposits were completely cored at sites AV\_a–c (Figure 7). Point-bar deposits occur from 0.8 m to a maximum of 5.4 m below ground and mainly consist of sand with a scarce percentage of mud. Cores AV\_a–c reveal that bar deposits cover either organic-rich mud (core AV\_b) or sandy deposits (cores AV\_a and AV\_c). Point-bar deposits are floored by a channel lag that consists of massive medium sand with pebble-sized mudclasts (Figure 8a). This basal lag is covered by lower bar deposits, consisting of 1–1.5 m of mud-free, well-sorted fine to medium sand, which is commonly massive or crudely plane-parallel stratified (Figure 8b). Upper bar deposits are ca. 2.5–3 m thick and consist of fine to very fine sand with subordinate mud layers. Sand is plane-parallel to ripple cross-laminated (Figure 8c) and contains mud for ca. 12%, 21% and 20% in the upstream, central and downstream zone, respectively. Mud layers (Figure 8c) range in thickness between 0.5 and 2 cm, and consist of massive or crudely laminated mud with plant debris. Lower bar deposits are ubiquitously mud free. The overall grain size of the bar deposits does not relevantly change along the bar, which appears as an almost monotonous sandy body from its upstream to downstream reach.

**Figure 7.** Sedimentary features of cores for bar and overbank deposits at the study site. Location of cores is shown with the conductivity for Slice 6.

**Figure 8.** Cored deposits: (**a**) massive medium sand with pebble-sized mudclasts forming the channel lag; (**b**) fine to medium sands from the lower point bar; (**c**) fine to very fine sands, with cross lamination and mud layers from the upper point bar; and (**d**) massive overbank mud with moderate organic content and horizontal bedding.

The overbank deposits were cored where geophysical investigations reveal the occurrence of electrically conductive sediments. These deposits mainly consist of silt-rich mud with subordinate sandy layers with horizontal bedding. Mud is massive and can be organic-rich (Figure 8d) or slightly oxidized in the lower and upper part of the overbank succession, respectively.
