Fluvial activity of the late-glacial to Holocene “Bergstraßenneckar” in the Upper Rhine Graben near Heidelberg, Germany – first results

Abstract

Abstract. The term “Bergstraßenneckar” (BSN) refers to an abandoned course of the river Neckar. It flowed in a northern direction east of the river Rhine in the eastern part of the northern Upper Rhine Graben in southwestern Germany. The former meandering course merged with the Rhine ca. 50 km further north of the site of the present-day confluence near Mannheim. The palaeo-channels are still traceable by their depressional topography, in satellite images and by the curved boundaries of adjacent settlements and land parcels. In the plan view, satellite and aerial images reveal a succession of meander bends, with older bends being cut off from younger channels. Based on stratigraphic investigations of the channel infill in the northern part of the BSN, fluvial activity is assumed from ca. 14 500 years ago until the onset of the Holocene. We present results of the first stratigraphic investigations at two sites in the southern part of the BSN near Heidelberg (Rindlache, Schäffertwiesen), together with results from granulometric, carbonate and organic content analyses, as well as electrical resistivity tomography (ERT) measurements. The data clearly show a change from high-energy fluvial bedload (sand, gravel) to low-energy fluvio-limnic suspended load (organoclastic and calcareous mud) and to peat formation. Radiocarbon dating indicates a time lag of ca. 1500 years between the cut-off meander site (Schäffertwiesen) and the younger site (Rindlache) that was possibly still active until the present-day confluence near Mannheim was established and the BSN eventually became abandoned. Our preliminary data conform with the pedo-sedimentary evidence from the northern BSN, but slight differences in the stratigraphic pattern of the youngest channels are identified: whilst for the younger channel sections of the northern BSN the channel-bottom facies (sand, gravel) is directly overlain by peat, the channel at Rindlache shows substantial intervening mud deposition, which is interpreted as suspension load from flooding by the new Neckar channel nearby. The study shows that more chronostratigraphic data from channel sections of the southern BSN are needed to better constrain the timing of the fluvial activity and to decipher the reasons for the abandonment of the BSN. These data are also necessary to better understand the pattern of temporary reactivation of the BSN channels across the Holocene and their usage by humans, which can be deduced from historical sources and archaeological data.

Lidar visualization techniques for the construction of geoarchaeological deposit models: An overview and evaluation in alluvial environments

“…Thus, while lidar visualizations aid in the interpretation of geomorphological processes and landscape evolution, they cannot be taken at face value and are most effective when integrated with other intrusive data sets (e.g., boreholes, test-pitting, etc.) or deeper methods of geophysical survey such as low-frequency ground penetrating radar (GPR), electrical resitivity tomography (ERT), or electromagnetic induction (EM) (Bates & Bates, 2016;Engel et al, 2022;Verhegge et al, 2016Verhegge et al, , 2021.…”

“…However, deposit models vary significantly in terms of their visual outputs from relatively simple two‐dimensional vertical cross‐sections and horizontal surfaces to more computationally demanding deposit thickness maps and pseudo‐three‐dimensional models. Some advanced deposit models also integrate a range of airborne and terrestrial remote sensing (Carey et al, 2019; Crabb et al, 2022; Schmidt et al, 2019) and geophysical survey data (Bates & Bates, 2016; Engel et al, 2022; Verhegge et al, 2016, 2021). Yet, the coalescing of such disparate, albeit complementary, measurements of flood plain surface features together with records of subsurface sediment stratigraphy and architecture is not straightforward.…”

“…significantly in terms of their visual outputs from relatively simple twodimensional vertical cross-sections and horizontal surfaces to more computationally demanding deposit thickness maps and pseudo-threedimensional models. Some advanced deposit models also integrate a range of airborne and terrestrial remote sensing (Carey et al, 2019;Crabb et al, 2022;Schmidt et al, 2019) and geophysical survey data (Bates & Bates, 2016;Engel et al, 2022;Verhegge et al, 2016Verhegge et al, , 2021).…”

Preface: Quaternary research from and inspired by the first virtual DEUQUA conference

“…While methodological aspects of obtaining ideal samples are discussed, their study also reports high-resolution paleoenvironmental records of likely sub-seasonal resolution. Engel et al (2022) investigate the late-glacial Bergstraßenneckar, a former course of the Neckar River in the Upper Rhine Graben in southwest Germany, by sediment cores and geophysical measurements. They were able to reconstruct the shift from a running river to silting-up meanders that took place about 11 000 to 10 500 years ago.…”