Digital elevation model of the Central Section including detailed drilling positions.

<p>Raw data source: LIDAR data are cordially provided by Bavarian Land Surveying Office for illustrative purposes.</p

Stratigraphical documentation of the KG 256 cross section within the North-Eastern Section.

<p>The cross section shows the in situ layers of the Rezat fen in the East and the trench structure in the West. For the first time there is in situ evidence for a Carolingian trench in the North-Eastern Section. The trench bottom is shown by horizontal bars.</p

West-East Section of the Fossa Carolina.

<p>The figure shows a digital elevation model with detailed drilling positions, electrical transects, and the flux gate magnetic survey. White dots mark the drilling positions. The black lines show the geo electrical transects 1 and 2. Raw data source: LIDAR data are cordially provided by Bavarian Land Surveying Office for illustrative purposes.</p

Synthetic longitudinal profile of the Fossa Carolina from Graben to Rezat River.

<p>a) The red line shows the Pre-Carolingian surface and watershed, the red dot indicates the summit the natural watershed. b) The short horizontal bars feature the Carolingian levels of excavation deduced from the drilling stratigraphies, and the blue dot indicates the artificial summit of the Carolingian trench bottom. c) The solid black line represents the level of the recent trench surface following the course of the canal.</p

The local topographical setting of the Fossa Carolina.

<p>The canal is located across a valley watershed between the Altmühl River (Danube catchment) and the Swabian Rezat River (Rhine-Main catchment) within the Treuchtlingen valley junction at the piedmont of the Franconian Jura escarpment. Data source: Open access SRTM data (3 arc-second, 90 m raster, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108194#pone.0108194-Greenbelt1" target="_blank">[72]</a>) and OpenStreetMap <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108194#pone.0108194-OpenStreetMap1" target="_blank">[73]</a>.</p

Stratigraphical documentation of the QP cross section within the Northern Section of the canal.

<p>The drawing shows a 42 m long cross section with the different facies types and the Carolingian level of excavation.</p

Cross section of the West-East Section at core O position.

<p>Cross section of the West-East Section at core O position.</p

Types of sediment texture in the Central Section and the West-East Section.

<p>a) fluvial type and b) ponding type.</p

SQUID magnetogram from the Northern Section.

<p>White dots mark the drilling positions. White arrows feature the course of canal. The image represents an area of 600 m×400 m. The magnetogram is embedded in a LIDAR illustration, which raw data are cordially provided by Bavarian Land Surveying Office.</p

Radiocarbon ages of the Fossa Carolina trench fill (Part 1).

<p>Calibration (one sigma) of the conventional ages was performed using the Cologne Radiocarbon Calibration Program (quickcal2007 ver.1.5, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108194#pone.0108194-Danzeglocke1" target="_blank">[48]</a>). KIA samples were conducted at Kiel AMS facility. SU-GL and SUERC samples were conducted at Glasgow AMS facility. MAMS samples were conducted at Mannheim AMS facility.</p><p>Radiocarbon ages of the Fossa Carolina trench fill (Part 1).</p