​​​​​​​Micromorphological analysis using a petrographic microscope is one of the conventional methods to characterise microfacies in rocks (sediments) and soils. This analysis of the composition and structure observed in thin sections (TSs) yields seminal, but primarily qualitative, insights into their formation. In this context, the following question arises: how can micromorphological features be measured, classified, and particularly quantified to enable comparisons beyond the micro scale? With the Micromorphological Geographic Information System (MiGIS), we have developed a Python-based toolbox for the open-source software QGIS 3, which offers a straightforward solution to digitally analyse micromorphological features in TSs. By using a flatbed scanner and (polarisation) film, high-resolution red–green–blue (RGB) images can be captured in transmitted light (TL), cross-polarised light (XPL), and reflected light (RL) mode. Merging these images in a multi-RGB raster, feature-specific image information (e.g. light refraction properties of minerals) can be combined in one data set. This provides the basis for image classification with MiGIS. The MiGIS classification module uses the random forest algorithm and facilitates a semi-supervised (based on training areas) classification of the feature-specific colour values (multi-RGB signatures). The resulting classification map shows the spatial distribution of thin section features and enables the quantification of groundmass, pore space, minerals, or pedofeatures, such nodules being dominated by iron oxide and clay coatings. We demonstrate the advantages and limitations of the method using TSs from a loess–palaeosol sequence in Rheindahlen (Germany), which was previously studied using conventional micromorphological techniques. Given the high colour variance within the feature classes, MiGIS appears well-suited for these samples, enabling the generation of accurate TS feature maps. Nevertheless, the classification accuracy can vary due to the TS quality and the academic training level, in micromorphology and in terms of the classification process, when creating the training data. However, MiGIS offers the advantage of quantifying micromorphological features and analysing their spatial distribution for entire TSs. This facilitates
The loess–palaeosol sequence and intercalated Palaeolithic find layers at the former brickyard of Rheindahlen are matters of ongoing scientific dispute. The age of different palaeosols and loess layers, hence their correlation with the global climate cycles, and the timing of repeated Neanderthal occupations have been hotly debated. These disagreements should be solved because the exceptional sedimentary and Palaeolithic sequences at Rheindahlen provide a unique opportunity to study diachronic changes in Neanderthal behaviour within the context of past climate change. We thus revisited one of the key loess sections of the Rheindahlen site to improve our understanding of loess formation processes and provide a more reliable chronostratigraphic framework for the sequence. High-resolution grain size analyses and micromorphology show that the Erkelenz Soil and the Rheindahlen Soil are characterized by more strongly developed Bt horizons than the modern soil. While these soils represent interglacial phases, the lowermost palaeosol likely formed during an interstadial and has been overprinted by weak clay illuviation during the formation of the Rheindahlen Soil. Sedimentary features of prolonged frost characterize loess and palaeosols below the modern soil and give indirect evidence for a Holocene age of the uppermost part of the sequence. Our luminescence dating approach corroborates this correlation and adds several Last Glacial deposition ages for the upper metres of the sequence. Previous correlation of this part of the sedimentary sequence with the penultimate glacial is thus rejected, whereas placing the Middle Palaeolithic inventories A3, B1, and B2 into the Last Glacial is confirmed. Luminescence measurements for the parental loess of the Erkelenz Soil and for loess layers below did not provide reliable ages probably related to signal saturation. The age of this part of the sequence thus remains open, hence the timing of human occupation testified by Palaeolithic inventories B3, B4/5, C1, and D1. The new findings provide an improved base for stratigraphic correlation of the Rheindahlen loess sequence and for investigating diachronic change in Neanderthal behaviour against the background of past climate change.
The flexibility in growth of BetulapubescensThe area of investigation is the southern Weichselian younger morainic area of Schleswig-Holstein, including a major Late Glacial archaeological type locality – the Ahrensburg tunnel valley. The period under investigation spans the time between 11 700 and 11 400 cal BP and hence the Late Glacial–Early Holocene transition, which is characterized by a significant shift in the vegetation. This shift has often been seen as a simple transition from treeless tundra to birch forest. The aim of the article is to provide a more realistic image of plant cover of the late Dryas 3 period and the Early Holocene period before the Preboreal oscillation by considering past natural growth limits of Betula pubescens
Loess–palaeosol sequences (LPSs) are important archives of landscape evolution, recording alternating periods of geomorphic activity (dust deposition and slope processes) and landscape stability (soil formation). LPSs of the Rhône Rift Valley are located along a spatial climatic gradient from the mid-latitudes to the Mediterranean region. This position renders them extremely valuable archives for correlating LPSs in the European loess belt and the Mediterranean region. Despite this important function, Rhône Rift Valley LPSs have been little investigated. In this study, we aimed to narrow this knowledge gap, in a first step towards linking LPS-based mid-latitude and Mediterranean palaeoenvironmental reconstructions. We studied the ∼ 14 m thick Baix LPS located at the western edge of the Rhône Rift Valley near Valence. Here, we focus on the lower ∼ 7 m of the LPS, which comprises 12 of 19 soil horizons overall, and record regional palaeoenvironmental variations from the Eemian to the Middle Pleniglacial (∼ marine isotope stage (MIS) 5 to MIS 3). Our reconstruction is based on detailed field description, complemented by granulometry (10 cm vertical resolution), and micromorphological analyses. Luminescence screening of cut-out soil-sediment columns subsampled with ∼ 5 cm vertical resolution (126 subsamples over 7 m) provides a preliminary chronometry. The loess deposits of the Baix LPS are strongly calcareous and predominantly silty but also contain sandy and fine gravelly laminae typical of loess deposits subjected to slope-wash processes. From bottom to top, the investigated part shows three intensely pedogenised levels: (1) a basal sequence of reddish-brown Btg and Bt horizons of a thick Eemian Stagnic Luvisol (MIS 5e); (2) an early glacial yellowish-brown∼ 100 km further south but also exhibits differences, reflecting its position at the spatial climatic transition between the presently temperate and the Mediterranean zone.
Anthropogenic activities have exerted strong influence on ecosystems worldwide, particularly since 1950 CE. The local impact of past human activities often started much earlier and deserves detailed study. Here, we present an environmental record from a 278 cm long sedimentary core from Lake Höglwörth (Bavaria, Germany). Sedimentological and geochemical parameters indicate that the organic-rich bottom sediments of the record consist of peat that formed prior to
Archeological and geoscientific research in loess landscapes remains challenging due to erosional discordances and the relocation of sediments by fluvial erosion and slope wash. The Lower Rhine Embayment (LRE) can serve as a blueprint for archeological and paleoenvironmental research in loess landscapes of Central Europe. The accumulation of wind-blown dust; paleosols developed therein; and the archeological artifacts preserved in loess, colluvial or alluvial sediments are evidence of the Pleistocene and Holocene dynamics of the landscape. Geomorphologic processes in different and specific relief positions must be considered different processes that transform and relocate sediments and archeological remains. Besides aeolian accumulation, erosion and deflation have also transformed the landscape of the LRE. These include fluvial slope wash, gully formation, colluviation, and periglacial processes such as solifluction, cryoturbation and the formation of ice wedge pseudomorphs. In addition, other post-depositional processes, including weathering and soil formation, modify the sedimentary record. In light of the landscape evolution from more hilly landscapes to the flat, agriculturally used terrain we see today, we highlight the relevance and importance of different geomorphological and soil processes including their impacts and challenges for archeological and geoscientific studies.
At the Last Glacial Maximum (LGM), the Rhine Glacier complex (Rhine and Linth glaciers) formed large piedmont lobes extending north into the Swiss and German Alpine forelands. Numerous overdeepened valleys there were formed by repeated glaciations. A characteristic of these overdeepened valleys is their location close to the LGM ice margin, away from the Alps. Numerical models of ice flow of the Rhine Glacier indicate a poor fit between the sliding distance, a proxy for glacial erosion, and the location of these overdeepenings. Calculations of the hydraulic potential based on the computed time-dependent ice surface elevations of the Rhine Glacier lobe obtained from a high-resolution thermo-mechanically coupled Stokes flow model are used to estimate the location of subglacial water drainage routes. Results indicate that the subglacial water discharge is high and focused along glacial valleys and overdeepenings when water pressure is equal to the ice overburden pressure. These conditions are necessary for subglacial water to remove basal sediments, expose fresh bedrock, and favor further erosion by quarrying and abrasion. Knowledge of the location of paleo-subglacial water drainage routes may be useful to understand patterns of subglacial erosion beneath paleo-ice masses that do not otherwise relate to the sliding of ice. Comparison of the erosion pattern from subglacial meltwater with those from quarrying and abrasion shows the importance of subglacial water flow in the formation of distal overdeepenings in the Swiss lowlands.
The study of geological archives of dust is of great relevance as they are directly linked to past atmospheric circulation and bear the potential to reconstruct dust provenance and flux relative to climate changes. Among the dust sinks, loess–palaeosol sequences (LPSs) represent the only continental and non-aquatic archives that are predominantly built up by dust deposits close to source areas, providing detailed information on Quaternary climatic and terrestrial environmental changes. Upper Pleistocene LPSs of western central Europe have been investigated in great detail showing their linkage toHere, we present an integrative approach that systematically combines sedimentological, rock magnetic, and bulk geochemical data, as well as information on Sr and Nd isotope composition, enabling a synthetic interpretation of LPS formation. We focus on the Schwalbenberg RP1 profile in the Middle Rhine Valley in Germany and integrate our data into a robust age model that has recently been established based on high-resolution radiocarbon dating of earthworm calcite granules. We show that Schwalbenberg RP1 is subdivided into a lower section corresponding to late oxygen isotope stage 3 (OIS; ∼ 40–30 ka) and an upper section dating into the Last Glacial Maximum (LGM; ∼ 24–22 ka), separated by a major stratigraphic unconformity. Sedimentological proxies of wind dynamics (U ratio) and pedogenesis (finest clay) of the lower section attest to comparable and largely synchronous patterns of northern hemispheric climatic changes supporting the overall synchronicity of climatic changes in and around the North Atlantic region. The anisotropy of magnetic susceptibility (AMS) reveals a clear correlation between finer grain size and increasing AMS foliation within interstadials, possibly owing to continuous accumulation of dust during pedogenic phases. Such a clear negative correlation has so far not been described for any LPS on stadial–interstadial scales.
Distinct shifts in several proxy data supported by changes in isotope composition (The ongoing ecological conversion of mountain forests in central Europe from widespread PiceaBetula–PinusCorylusPiceaFagus–PiceaAbies–Fagus–PiceaFagusAbiesPiceaPicea
Erosion during potential future glaciations, especially the incision of deep tunnel valleys, is a major challenge for the long-term safety of a radioactive waste repository. Tunnel valleys are a common feature of formerly glaciated sedimentary basins and were incised by pressurised subglacial meltwater. Besides glaciological conditions, tunnel-valley formation depends strongly on the erodibility and hydraulic conductivity of the substratum. In northern Germany, tunnel valleys formed during the Pleistocene glaciations are widespread and may attain depths of almost 600 m. The Pleistocene record may provide an indication for the potential regional distribution and maximum depth of future glaciogenic erosion. We present a new overview map of the maximum depth of Pleistocene erosion in northern Germany. Depth zones were extracted from the existing data and maps provided by the state geological surveys. Based on the mapped depth zones, the potential for future tunnel-valley formation can be assessed. The map may serve as a base to define a spatially variable additional depth that should be added to the minimum depth of a repository required by legislation.
Valley infills are essential for understanding changes in hydrology and landscape. Anthropogenic activities are proven by prehistoric settlement remains, which mark distinct sediments and soils as usable land during certain time periods. In 2009 and 2018/19, excavations by the Saxonian Archaeological Heritage Office were conducted in the Elbe valley between Meißen and Dresden, preceding the construction of two natural gas pipelines. As a result, two important multicultural prehistoric sites were discovered on the Lower Weichselian Terrace (LWT) in different sediments and on varying stratigraphic levels.
During this study sediments and soils at the excavation sites and throughout the pipe trench have been documented. Micromorphological, sedimentological and geochemical investigations and analyses of archaeobotanical and archaeological finds, complemented by 14C and optically stimulated luminescence (OSL) dating, enabled deciphering the structure of sediments and soils. Two major sites were the focus. At the Clieben site, an early Neolithic settlement and former topsoil, developed in a Weichselian valley loam above gravels and sands, are covered by younger overbank fines. At the Brockwitz site, shallow incision channels in the LWT were filled with clayey overbank fines during the Preboreal. An overprinting humic soil horizon was later anthropogenically overprinted during the early and middle Neolithic period. An omnipresent layer of Subboreal or younger overbank fines, covering the majority of the LWT in combination with the spatially confined Preboreal overbank fines, mirrors the ever-growing risk of flooding in a formerly attractive settlement area.Loess–palaeosol sequences (LPSs) of the oceanic-influenced European loess belt underwent frequent post-depositional processes induced by surface runoff or periglacial processes. The interpretation of such atypical LPSs is not straightforward, and they cannot be easily used for regional to continental correlations. Within the last few years, however, such sequences gained increased attention, as they are valuable archives for regional landscape dynamics. In this study, the Siersdorf LPS was analysed using a multi-proxy approach using sedimentological, geochemical, and spectrophotometric methods combined with luminescence dating and tentative malacological tests to unravel Pleniglacial dynamics of the Lower Rhine Embayment. A marshy wetland environment for the late Middle Pleniglacial to the early Upper Pleniglacial was shown by colour reflectance and grain size distribution. Age inversions from luminescence dating paired with geochemical and sedimentological data reveal long-lasting erosional processes during the early Upper Pleniglacial, which were constrained to a relatively small catchment with short transport ranges. The upper sequence shows typical marker horizons for the study area and indicate harsh, cold-arid conditions for the late Upper Pleniglacial. In comparison with other terrestrial archives, the Siersdorf LPS shows that the Lower Rhine Embayment was more diverse than previously assumed, regarding not only its geomorphological settings and related processes but also its ecosystems and environments.
representative preliminary safety assessments
The age of the push moraine complex Wallsbüll-Böxlund, Schleswig-Holstein, is unclear despite investigations in this area for decades. To address the timing of formation of both the push moraine complex and the peat and soils found in its depressions, an outcrop in Osterbylund (OBL) was investigated. Optically stimulated luminescence and
The sites of Hawelti–Melazo in the Tigray region of the northern Ethiopian Highlands is an archaeological hotspot related to the D'mt kingdom (ca. 800–400 BCE). The existence of several monumental buildings, which have been excavated since the 1950s, underline the importance of this area in the Ethio-Sabaean period. We investigated the geomorphological and geological characteristics of the site and its surroundings and carried out sedimentological analyses, as well as direct (luminescence) and indirect (radiocarbon) sediment dating, to reconstruct the palaeoenvironmental conditions, which we integrated into the wider context of Tigray. Luminescence dating of feldspar grains from the May Agazin catchment indicate enhanced fluvial activity in the late Pleistocene, likely connected to the re-occurring monsoon after the Last Glacial Maximum (LGM). The abundance of trap basalt on the Melazo plateau, which provides the basis for the development of fertile soils, and the presumably higher groundwater level during the Ethio-Sabaean Period, provided favourable settlement conditions. The peninsula-like shape of the Melazo plateau was easily accessible only from the east and northeast, while relatively steep scarps enclose the other edges of the plateau. This adds a possible natural protective function to this site.
Overdeepened structures occur in formerly and presently glaciated regions around the earth and are usually referred to as overdeepenings or tunnel valleys. The existence of such troughs has been known for more than a century, and they have been attributed to similar formation processes where subglacial meltwater plays a decisive role. This comparison highlights that (foreland) overdeepenings and tunnel valleys further occur in similar dimensions and share many characteristics such as gently sinuous shapes in plan view, undulating long profiles with terminal adverse slopes, and varying cross-sectional morphologies. The best explored examples of overdeepened structures are situated in and around the European Alps and in the central European lowlands. Especially in the vicinity of the Alps, some individual troughs are well explored, allowing for a reconstruction of their infill history, whereas only a few detailed studies, notably such involving long drill core records, have been presented from northern central Europe. We suggest that more such studies could significantly further our understanding of subglacial erosion processes and the regional glaciation histories and aim to promote more intense exchange and discussion between the respective scientific communities.
Loess–palaeosol sequences (LPSs) remain poorly investigated in the southern part of the Upper Rhine Graben but represent an important element to understand the environmental context controlling sediment dynamics in the area. A multi-method approach applied to the LPS at Köndringen reveals that its formation occurred during several glacial–interglacial cycles. Field observations, as well as colour, grain size, magnetic susceptibility, organic carbon, and carbonate content measured in three profiles at 5 cm resolution, provide detailed stratigraphical information. Only minor parts of the LPS are made up of loess sediment, whereas the major parts are polygenetic palaeosols and pedosediments of varying development that are partly intersected, testifying to a complex local geomorphic evolution. The geochronological framework is based on 10 cm resolution infrared-stimulated luminescence (IRSL) screening combined with 18 multi-elevated-temperature post-IR IRSL ages. The luminescence ages indicate that two polygenetic, truncated Luvisols formed during marine isotope stages (MISs) 9(–7?) and MIS 5e, whereas unaltered loess units correspond to the last glacial (MISs 5d–2) and MIS 8. The channel-like structure containing the two truncated Luvisols cuts into > 2 m thick pedosediments apparently deposited during MIS 12. At the bottom of the LPS, a horizon with massive carbonate concretions (loess dolls) occurs, which may correspond to at least one older interglacial.