Transformation of a low-relief periglacial landscape during the Mid Pleistocene Transition revealed by cosmogenic Krypton

The Early to Mid-Pleistocene Transition (MPT) between ~ 1.2 Ma to ~500 ka (also termed as ‘900 ka event’) marks a change in climatic periodicity, from 41 ka cycles to 100 ka cycles of increased intensity. In non-glaciated areas of Europe this climatic shift has been associated with pronounced acceleration of river incision, in part driven by increased sediment loads from periglacial hillslope processes. Until the Pleistocene, low-relief landscapes are thought to have dominated throughout Europe. Utilizing novel in-situ cosmogenic Krypton in zircon methodology (Dunai et al. 2022), we find direct evidence that this was indeed the case, and that these landscapes were profoundly transformed during the MPT.

Our study area (Vogtland, Saxony, Germany) was never glaciated but was within 50 km of the ice margins during the largest Quaternary glaciations. For our study, we utilize a unique source of megacryst zircons (Ebersbrunn diatreme), whose exhumation, dispersal and burial history is recorded by cosmogenic Krypton. The megacryst zircons are found in the fluvial sediments of the current catchments downstream of the source (Raumbach, Göltzsch, Weiße Elster), however, also in a distal catchment (Weida), now disconnected from the source due to late Pleistocene superimposed drainage (Weiße Elster valley).

The cosmogenic Krypton data from the megacryst zircons is commensurate with a long (1 to 3 Myr) exposure at or near the surface, or exhumation at a very low rate (<0.1 mMyr^-1), followed by a period of burial of 600 to 900 kyr and a recent re-emergence in the active fluvial system. Samples collected further from the source (≥15 vs. 5 km) have longer burial histories. The extremely low erosion rates inferred prior to burial (<0.1 mMyr^-1) are unprecedented for temperate regions in Europe, and late Quaternary erosion rates of landscapes with similarly moderate relief are two orders of magnitude faster. In situ cosmogenic ¹⁰Be and ²⁶Al results on vein-quartz from the region address the latter findings.

Based on our data and external constraints on climate and landscape evolution in Europe, the most likely scenario is that of a formerly stable, low-relief Plio-Pleistocene landscape whose transformation in response to periglacial processes commenced during marine isotope stage (MIS) 22 and was largely concluded by MIS 16. Incision of drainage that developed during and after the MPT formed the current moderate relief landscape.

Dunai et al. (2022) Geochronology, https://doi.org/10.5194/gchron-4-65-2022