Deciphering Flexural Subsidence in the Lower Rhine Embayment: Quaternary Burial Dating as a Key to Uplift–Subsidence Coupling
Dr. habil. Benedikt Ritter-Prinz
Geology
Motivation
Uplift and subsidence driven by mantle plume upwelling or long-wavelength lithospheric folding exert a powerful influence on regional topography. Proximal to the deformational source, rock uplift generates elevated terrain, promoting the development of river terraces and accelerating incision (e.g. Rockwell et al., 1988; Burbank et al., 1996). In contrast, distal regions often respond through flexural isostasy, where downward bending of the lithosphere leads to subsidence and the formation of sedimentary basins (Watts, 2023). This dynamic interplay between uplift and subsidence governs both landscape evolution and sediment dispersal patterns (Watts, 2023). Accurately quantifying vertical motions is therefore essential for reconstructing tectonic histories and understanding how surface processes respond to deep Earth forcing.
Within a recent project (DFG 525049675 – “Quantifizierung von Flusseinschneidung und Hebung im Rheinischen Schiefergebirge durch Datierung von Flussterrassen im Plateau-Tal des Rheins mit der 10Be–26Al burial dating-Methode"), we have already gained new insights into the uplift rates of the Rhenish Massif by applying state-of-the-art burial dating methods. These techniques allow us to establish the timing of Rhine River terrace formation and, in turn, to constrain regional uplift rates. Such chronological constraints are crucial for distinguishing between the potential driving forces behind isostatic uplift, whether mantle-related (e.g. Kreemer et al., 2020) or lithospheric in origin (e.g. Cloetingh and Burov, 2011) coupled with Quaternary climate variability in the Rhine region. However, to achieve a holistic understanding of the processes involved, it is equally important to investigate the complementary regions that undergo flexural isostatic subsidence. These subsiding areas act as sedimentary sinks and provide critical information on the feedback between uplift, erosion, and deposition, thereby offering a more complete picture of landscape evolution and Earth surface dynamics.
The central hypothesis of this project is that sediments within the Lower Rhine Embayment (NW of the above mentioned Rhenish Massif) preserve a record of distal subsidence directly linked to flexural responses from uplift in adjacent regions and paleoclimate variability during the Quaternary (e.g. Boenigk and Frechen, 2006). However, disentangling this signal is challenging due to the region’s complex tectonic history. The Lower Rhine Embayment has long been affected by rift-related subsidence, particularly during the Miocene when major sediment accumulation and extensive lignite formation occurred (Stock et al., 2016; Schäfer et al., 2005). Although this rift-driven subsidence has since diminished, Quaternary vertical movements may reflect flexural subsidence induced by uplift of the Rhenish Massif around the Eifel region (Gibbard, 2021). To resolve these overlapping signals, we will target and date Quaternary fluvial sediments exposed in active open-pit lignite mines, which provide exceptional high-resolution outcrops.
Plan
The work plan begins with a pilot field campaign to one open-pit mine, where we will conduct detailed sedimentological recording and assess the stratigraphic relationships between the various formations. With support from RWE Energy and the Geological Survey of NRW (GD NRW), we will obtain initial samples for a proof-of-concept study. Methodologically, we aim to apply ¹⁰Be/²⁶Al burial dating (Balco and Rovey, 2008; Granger, 2006) to constrain sediment deposition ages and evaluate the feasibility of ¹⁰Be meteoric dating (Bourles et al., 1989) for those sediments as a complementary approach. This dual dating strategy will provide absolute chronological information, allowing us to better resolve the timing and drivers of subsidence in the Lower Rhine Embayment during the Quaternary.