Late Middle Pleistocene (MIS 11-6) in Europe – introduction

The detailed chronostratigraphy of the Saalian Stage sensu lato (Marine Isotope Stage: MIS 11b-6) in Europe is far from being clarified and with the exception of the Late Saalian glaciation (MIS 6), there are in fact two separate schemes. One is for the northern, glaciated part of the continent, which is full of stratigraphical hiatuses that make interregional correlation difficult. The other one is for the extraglacial area, based on sites with fluvial, lake, and loess sequences, and this scheme is much more complete. Combining these two schemes remains a challenging field in the European stratigraphy. Among the main problems, there is a lack of reliable dating methods that can be applied to this part of the Middle Pleistocene. Correlation of terrestrial sequences with high-resolution deep-sea oxygen isotope curves seems to be a good way forward for future progress. Such correlation is crucial for identifying and understanding the interactions between orbital parameters, global ice volume, and greenhouse gas concentrations, which are responsible for the various expansions and contractions of the ice sheets throughout the Saalian Stage.

The following collection of contributions presents both unique and synthesized regional evidence that provides considerable clarification regarding this part of the European Quaternary stratigraphical sequence. It is a reliable step forward to overcome an over-simplistic view, because progress over recent years in many different fields has led to significant advances in our understanding regarding the interactions between environmental processes and climate.

We have here articles related to the late Middle Pleistocene stratigraphy including several topics, among them MIS 10-7 palaeoclimate, Early Saalian (= MIS 9) and Late Saalian (= MIS 7) interglacials, glacial evidence, loess and fluvial stratigraphy, as well as correlation of terrestrial and marine stratigraphy. The contributions are multidisciplinary and provocative, being focused on the main challenges to stimulate further scientific discussion.

The contribution of Candy et al. (2024) is a review of the Holsteinian Stage and its equivalents (= MIS 11c; c. 426 000 to 396 000 years ago) to climate reconstructions across Europe, based on varved lake records from the northern part of the continent, long pollen records of southern Europe and the comparison of both with marine, including pollen, records from the North Atlantic. This review is especially focused on evidence of abrupt climate changes and the result is a discussion of the evidence for millennial and centennial scale climate change noted in the European records, the patterns of warming across this interglacial and the discrepancy in duration between the marine and terrestrial records.

The contribution by Antoine & Limondin-Lozouet (2024) is a review of loess–palaeosol sequences and fluvial terrace records from the late Middle Pleistocene of northern France. Based on the cyclostratigraphical approach to pedosedimentary sequences controlled by major glacial–interglacial climate cycles, it shows that the MIS 7-equivalent is undoubtedly an unusual interglacial characterized either by drier and/or cooler conditions than other Pleistocene temperate events, despite this interglacial being marked by the highest Northern Hemisphere insolation of the last 800 000 years. There are two alluvial formations deposited between early MIS 8 and late MIS 7 in the Somme terraces and two interglacial luvisols (MIS 7e and 7a–c) separated by loess of MIS 7d, the latter a cold-climate stadial that lasted c. 18 000 years.

The contribution by Krahn et al. (2024) provides evidence for repeated variations in climate, hydrology, and catchment vegetation cover during the MIS 9 equivalent event at Schöningen in northern Germany. It offers the opportunity to reconstruct a rarely well-preserved and highly dynamic post-Holsteinian environmental transition. Temperature reconstructions of two steppe (open woodland) phases demonstrate a more pronounced continental climate during this interval. During the interjacent woodland and steppe or woodland phase the climate was generally more humid and with reduced seasonal temperature variations.

The contribution by Rigterink et al. (2024) presents the first subfossil chironomid record with summer temperatures reconstruction from the 300 000-year-old Reinsdorf sequence at Schöningen in northern Germany. By applying temperature interpretation models to the chironomid assemblages, based on Swiss–Norwegian and Swiss–Norwegian–Polish chironomid–temperature calibration data, mean July air temperatures have been reconstructed. They were found to be lower (as much as 1 °C than today) during warmer and wetter transitional zones, and slightly increasing (up to 1.5 °C warmer than today) during cooler and dry steppe phases, most likely caused by higher continentality.

The contribution of Gibson & Gibbard (2024) is a profound revision of the Middle Pleistocene glacial history of Britain and its correlation across the North Sea. Two major glaciations have been identified, the earliest during the Anglian Stage (= Elsterian, c. MIS 12), and the second recorded by two phases during the Late Wolstonian Substage (Late Saalian; MIS 6). Until recently, the area occupied by ice sheet during this younger glacial episode was much more limited, less clearly represented, little studied and weakly defined.

The contribution by Šeirienė & Bitinas (2024) is a critical overview of the late Middle Pleistocene stratigraphy in Lithuania. The Butėnai (Holsteinian) Interglacial is well defined, except for its correlation with a marine isotope stage. By contrast, the geological setting of the Snaigupėlė Interglacial (MIS 10 or 8?) remains controversial.

The contribution by Marković et al. (2024) presents a regional loess stratigraphy in the Vojvodina region, in the southeastern Carpathian Basin. The loess stratigraphy in the Vojvodina region is an important link in the integration of the European terrestrial stratigraphical schemes and the marine isotope stratigraphical model.

As this collection of articles demonstrates, despite these lines of new evidence, much is still to be investigated and established on the nature and timing of events during the c. 270 000 years of the Saalian Stage and its equivalents. This is especially so for northern Europe where the fragmented sequences across the region make a full understanding of this period problematic. Unquestionably, this period is characterized by major landscape remodelling, which resulted from the impact of extensive erosion particularly under both prolonged periglacial and glaciation regimes. It is now well established that these lengthy cold-climate phases were punctuated by short interglacials and associated temperate climatic intervals, the character of which is slowly beginning to emerge. Whilst the focus of research has inevitably been on the environment of these interglacial and interstadial events, the character of the longer cold-climate phases remains poorly understood. Future research should be directed towards unravelling the nature of both the cold and warm intervals resulting from different climate background conditions, and indeed the nature and timing of this complex period of the late Middle Pleistocene throughout the European continental region.