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- ItemOSL-dating of the Pleistocene-Holocene climatic transition in loess from China, Europe and North America, and evidence for accretionary pedogenesis(Amsterdam [u.a.] : Elsevier, 2021) Constantin, D.; Mason, J.A.; Veres, D.; Hambach, U.; Panaiotu, C.; Zeeden, C.; Zhou, L.; Marković, S.B.; Gerasimenko, N.; Avram, A.; Tecsa, V.; Groza-Sacaciu, S.M.; del Valle Villalonga, L.; Begy, R.; Timar-Gabor, A.Loess deposits intercalated by paleosols are detailed terrestrial archives of Quaternary climate variability providing information on the global dust cycle and landscape dynamics. Their paleoclimatic significance is often explored by quantifying their mineral magnetic properties due to their sensitivity to local/regional hydroclimate variability. Detailed chronological assessment of such regional proxy records around the climatic transitions allow a better understanding of how regional records react to major global climatic transitions such as the Pleistocene-Holocene climatic transition. Logs of high-resolution magnetic susceptibility and its frequency dependence were used as paleoclimatic proxies to define the environmental transition from the last glacial loess to the current interglacial soil as reflected in nine loess-paleosol sequences across the northern hemisphere, from the Chinese Loess Plateau, the southeastern European loess belt and the central Great Plains, USA. The onset of increase in magnetic susceptibility above typical loess values was used to assess the onset of, and developments during, the Pleistocene-Holocene climatic transition. High-resolution luminescence dating was applied on multiple grain-sizes (4–11 μm, 63–90 μm, 90–125 μm) of quartz extracts from the same sample in order to investigate the timing of Pleistocene-Holocene climatic transition in the investigated sites. The magnetic susceptibility signal shows a smooth and gradual increase for the majority of the sites from the typical low loess values to the interglacial ones. The initiation of this increase, interpreted as recording the initiation of the Pleistocene-Holocene climatic transition at each site, was dated to 14–17.5 ka or even earlier. Our chronological results highlight the need of combining paleoclimatic proxies (magnetic susceptibility) with absolute dating when investigating the Pleistocene-Holocene climatic transition as reflected by the evolution of this proxy in order to avoid chronostratigraphic misinterpretations in loess-paleosol records caused by simple pattern correlation. The detailed luminescence chronologies evidence the continuity of eolian mineral dust accumulation regardless of glacial or interglacial global climatic regimes. Coupled with magnetic susceptibility records this indicates that dust sedimentation and pedogenesis act simultaneously and result in a non-negligible accretional component in the formation of Holocene soils in loess regions across the Northern Hemisphere. The luminescence ages allowed the modeling of accumulation rates for the Holocene soil which are similar for European, Chinese and U.S.A. loess sites investigated and vary from 2 cm ka−1 to 9 cm ka−1. While accretional pedogenesis has often been implicitly or explicitly assumed in paleoclimatic interpretation of loess-paleosol sequences, especially in the Chinese Loess Plateau, our luminescence data add direct evidence for ongoing sedimentation as interglacial soils formed.
- ItemLoess landscapes of Europe – Mapping, geomorphology, and zonal differentiation(Amsterdam [u.a.] : Elsevier, 2021) Lehmkuhl, F.; Nett, J.J.; Pötter, S.; Schulte, P.; Sprafke, T.; Jary, Z.; Antoine, P.; Wacha, L.; Wolf, D.; Zerboni, A.; Hošek, J.; Marković, S.B.; Obreht, I.; Sümegi, P.; Veres, D.; Zeeden, C.; Boemke, B.; Schaubert, V.; Viehweger, J.; Hambach, U.Paleoenvironmental reconstructions on a (supra-)regional scale have gained attention in Quaternary sciences during the last decades. In terrestrial realms, loess deposits and especially intercalations of loess and buried soils, so called loess-paleosol sequences (LPS) are important archives to unravel the terrestrial response to e.g. climatic fluctuations and reconstruct paleoenvironments during the Pleistocene. The analysis of LPS requires the knowledge of several key factors, such as the distribution of the aeolian sediments, their location relative to (potential) source areas, the climate conditions that led to their emplacement and the topography of the sink area. These factors strongly influence the sedimentological and paleoenvironmental characteristics of LPS and show broad variations throughout Europe, leading to a distinct distribution pattern throughout the continent. We present a new map of the distribution of aeolian sediments (mainly loess) and major potential source areas for Europe. The map was compiled combining geodata of different mapping approaches. Most of the used geodata stems from accurate national maps of 27 different countries. Problematic aspects such as different nomenclatures across administrative borders were carefully investigated and revised. The result is a seamless map, which comprises pedological, geological, and geomorphological data and can be used for paleoenvironmental and archeological studies and other applications. We use the resulting map and data from key geomorphological cross-sections to discuss the various influences of geomorphology and paleoenvironment on the deposition and preservation of Late Pleistocene loess throughout Europe. We divided the loess areas into 6 main loess domains and 17 subdomains to understand and explain the factors controlling their distribution and characteristics. For the subdivision we used the following criteria: (1) influence of silt production areas, (2) affiliation to subcatchments, as rivers are very important regional silt transport agents, (3) occurrence of past periglacial activity with characteristic overprinting of the deposits. Additionally, the sediment distribution is combined with elevation data, to investigate the loess distribution statistically as well as visually. Throughout Europe, the variations, and differences of the loess domains are the results of a complex interplay of changing paleoenvironmental conditions and related geomorphologic processes, controlling dust sources, transport, accumulation, preservation, pedogenesis, alongside erosional and reworking events. Climatic, paleoclimatic, and pedoclimatic gradients are on the continental scale an additional important factor, since there are e.g. latitudinal differences of permafrost and periglacial processes, an increase in continentality from west to east and in aridity from northwest to southeast and south, strongly affecting regional sedimentary and geomorphic dynamics. We propose three main depositional regimes for loess formation in Europe: (1.) periglacial and tundra loess formation with periglacial processes and permafrost in the high latitude and mountainous regions; (2.) steppe and desert margin loess formation in the (semi-)arid regions; and (3.) loess and soil formation in temperate and subtropical regions. Loess deposits of (1.) and (2.) show coarser, sandier particle distributions towards the glacial and desert regions. In the humid areas (3.) forest vegetation limited dust production and accumulation, therefore, there is an increase in finer grain sizes due to an increase in weathering.
- ItemGrain-size distribution dataset of supercritical flow sediments from a Gilbert-type delta that are associated with disaggregation bands(Amsterdam [u.a.] : Elsevier, 2022) Tanner, David C.; Brandes, Christian; Winsemann, JuttaThis is a dataset of grain-size distribution in sub- and supercritical flow sediments of a Gilbert-type delta from an outcrop in North Germany. Thirteen samples of ca 2.5 kg were dried (at 105°C), and homogenised twice with a sample divider. A representative sample of 1-2 g was then analysed using laser diffraction. The grain-size distribution of the sand has a maximum between fine to medium sand, with a long fine fraction tail down to 0.06 µm and occasional coarse fractions (up to 1.5 mm) in some samples. Specific grain-size distributions correlate with the different sedimentary bedforms from which the samples were taken. This data is important for two reasons: Firstly, sedimentary structures formed by Froude supercritical flows are controlled by grain-size. However, few studies have provided grain-size datasets from the natural record, which often have a much wider grain-size distribution than experimentally-produced supercritical flow deposits. Secondly, the sands were deformed subsequently by disaggregation bands, a type of geological fault that only develops in porous granular materials, i.e. well-sorted, medium sand. The disaggregation bands are indicative of seismic or even aseismic, creeping movement of basement faults.
- ItemMeasuring and evaluating colorimetric properties of samples from loess-paleosol sequences(Amsterdam [u.a.] : Elsevier, 2023) Laag, Christian; Lagroix, France; Kreutzer, Sebastian; Chapkanski, Stoil; Zeeden, Christian; Guyodo, YohanColorimetric measurements are valuable in studying paleoenvironmental changes in sediment archives such as loess-paleosol sequences. These measurements allow for the identification of climate-sensitive minerals such as hematite, goethite, and secondary carbonates, as well as the observation of stratigraphic changes influenced by paleoclimate variations. Herein, a detailed workflow protocol emphasizing mineral abundance extraction by determining true band amplitudes is presented. Moreover, we present a protocol for colorimetric measurements that eliminates container bias, allowing the analysis and re-analysis of stored sediment quickly and inexpensively. Finally, we introduce a new R-package ('LESLIE') for graphical data display and enhancement. The protocol and its validation are demonstrated on the Suhia Kladenetz loess-paleosol sequence of northern Bulgaria. • A detailed workflow protocol eliminating container bias in colorimetric measurements and extracting mineral abundances is presented. • The protocol is independently validated with aid of Attenuated Total Reflectance Fourier Transform mid-infrared (ATR-FTIR) spectroscopic experiments. • Stratigraphic color enhancement using the R-package 'LESLIE' is facilitated by a user-friendly R-shiny application.
- ItemSeismic interpretation and structural restoration of the Heligoland glaciotectonic thrust-fault complex: Implications for multiple deformation during (pre-)Elsterian to Warthian ice advances into the southern North Sea Basin(Amsterdam [u.a.] : Elsevier, 2020) Winsemann, Jutta; Koopmann, Hannes; Tanner, David C.; Lutz, Rüdiger; Lang, Jörg; Brandes, Christian; Gaedicke, ChristophDespite a long history of research, the locations of former ice-margins in the North Sea Basin are still uncertain. In this study, we present new palaeogeographic reconstructions of (pre-) Elsterian and Warthian ice-margins in the southeastern North Sea Basin, which were previously unknown. The reconstructions are based on the integration of palaeo-ice flow data derived from glaciotectonic thrusts, tunnel valleys and mega-scale glacial lineations. We focus on a huge glaciotectonic thrust complex located about 10 km north of Heligoland and 50 km west of the North Frisian coast of Schleswig-Holstein (Northern Germany). Multi-channel high-resolution 2D seismic reflection data show a thrust-fault complex in the upper 300 ms TWT (ca. 240 m) of seismic data. This thrust-fault complex consists of mainly Neogene delta sediments, covers an area of 350 km2, and forms part of a large belt of glaciotectonic complexes that stretches from offshore Denmark via northern Germany to Poland. The deformation front of the Heligoland glaciotectonic complex trends approximately NNE-SSW. The total length of the glaciotectonic thrust complex is approximately 15 km. The thrust faults share a common detachment surface, located at a depth of 250–300 ms (TWT) (200–240 m) below sea level. The detachment surface most probably formed at a pronounced rheological boundary between Upper Miocene fine-grained pro-delta deposits and coarser-grained delta-front deposits, although we cannot rule out that deep permafrost in the glacier foreland played a role for the location of this detachment surface. Restored cross-sections reveal the shortening of the complex along the detachment to have been on average 23% (ranging from ca. 16%–50%). The determined ice movement direction from east-southeast to southeast suggests deformation by an ice advance from the Baltic region. The chronospatial relationship of the thrust-fault complex and adjacent northwest-southeast to northeast-southwest trending Elsterian tunnel valleys implies a pre-Elsterian (MIS 16?) age of the glaciotectonic complex. However, the age of these Elsterian tunnel valleys is poorly constrained and the glaciotectonic complex of Heligoland may also have been formed during an early Elsterian ice advance into the southeastern North Sea Basin. The glaciotectonic complex underwent further shortening and the Elsterian tunnel-valley fills that were incised into the glaciotectonic complex were partly deformed during the Saalian Drenthe and Warthe (1) ice advances.