Frank Lehmkuhl

The source of aeolian sediments such as loess has been investigated since decades. Reliable knowledge on potential dust sources is crucial to understand past climatic and environmental conditions accompanying the dispersal of early modern humans (EMH) into Europe. Provenance studies are usually performed on small sample sets and most established methods are expensive and time-consuming. Here, we present the results of high-resolution geochemical analyses performed on five loess-palaeosol sequences from the Lower Danube Basin (LDB), a region, despite its importance as a trajectory for EMH, largely underrepresented in loess provenance studies. We compare our results with geochemical data of loess-palaeosol sequences from Austria, Hungary, Serbia, and Ukraine. Based on published literature, we thus evaluate five plausible sedimentary pathways for the LDB loess: 1) the Danube alluvium (DA) pathway, which constrains the transport and re-deposition of detrital material by the Danube and i...

"Today, so called Kobresia-pastures (alpine meadows) are the dominant vegetation type in eastern Tibet, covering an area of about 450.000 km2. They are mostly understood as more or less natural vegetation type. Our palynological data combined with ecological results lead to the assumption, that Kobresia-pastures are the product of grazing. We demonstrate that nomadic use influenced their development possibly as early as 8500 years ago concomitant with the early domestication of yaks. Since then, structure and species composition of the mats have been shaped by grazing. The anthropo-zoogenic influence increased with the establishment of the first Tibetan kingdom, the so called Yarlung Dynasty, some 1500 years ago and 1200 years ago with the establishment of nomadic migration routes which are still practiced today. During the medieval warm period the upper limit of the mats raised. The latest increase in grazing intensity started around 1980.

The Carpathian Basin is a key region for understanding modern human expansion into western Eurasia during the Late Pleistocene because of numerous early hominid fossil find spots. However, the corresponding archeological record remains less understood due to a paucity of well dated, contextualized sites. To help rectify this, we excavated and sampled Crvenka-At (Serbia), one of the largest Upper Paleolithic sites in the region to obtain radiometric ages for the archeological artifacts and evaluate their depositional context and subsequent site formation processes. Our results confirm that this locality represents a multiple-occupation Aurignacian site that dates to 36.4 ± 2.8 ka based on modeling of luminescence ages. Electrical resistivity tomography measurements indicate that the site formed on a sandy-gravelly fill terrace covered by overbank deposits. Complex grain size distributions further suggest site formation in contrasting depositional environments typically occurring alon...

Menschliche Eingriffe in Form von Landnutzungsänderungen, Hochwasserschutzmaßnahmen, Wasserkra anlagen, Bergbauaktivitäten, Schifahrt und Trinkwasserversorgung haben in den letzten Jahrhunderten dazu geführt, dass viele heutige Fluss systeme umfangreiche Veränderungen der Ab„ussund Morphodynamik erfahren haben [2, 3]. Aus der menschlichen Beein„ussung ergeben sich nicht nur negative Folgen für die Hochwassersicherheit, die Ökologie und die SchiŒarkeit von Gewässern, sondern auch für die Verbreitung von aquatischen Schadstoen. Viele Schadstoe lagern sich an Sedimenten an und werden so mit der Strömung transportiert und entweder auf der Gewässersohle oder bei Hochwasserereignissen auf den Vorländern abgelagert und bei späteren Ereignissen wieder remobilisiert [1, 11]. Bereits im Wasserhaushaltsgesetz (§ 6 Abs. 1 WHG) ist verankert, dass Gewässer vor nachteiligen Veränderungen der Gewässereigenscha en geschützt werden müssen. In § 6, Abs. 2. WHG wird festgelegt, dass nicht naturnah ausgebaute natürliche Gewässer so weit wie möglich in einen naturnahen Zustand zurückgeführt werden sollen. Spätestens seit Inkra treten der EG-Wasserrahmenrichtlinie nimmt der naturnahe Gewässerausbau eine zentrale Rolle in Wasserbau und Wasserwirtschaft ein. Bei Renaturierungsmaßnahmen sollen die mittels Vergleich von Leitbild und Ist-Zustand eines Fließgewässers festgelegten Entwicklungsziele hinsichtlich Abflussdynamik und Morphologie innerhalb eines bestimmten Zeitraumes erreicht werden. In der vorgestellten Studie soll die morphodynamische Entwicklung eines neu angelegten Gewässerabschnittes am Beispiel der Inde (Nebenf luss der Rur in Nordrhein-Westfalen) sowie der Eintrag von Schadstoen von Oberstrom in den neuen Gewässerabschnitt, als Tracer für die morphodynamische Entwicklung, bestimmt werden. Die Verlegung der Inde war Konsequenz des fortschreitenden, gro߄ächigen Tagebaus Inden im Rheinischen Braunkohlerevier zwischen Aachen und Mönchengladbach (Bild 1) und wurde zum Anlass einer naturnahen Gestaltung des neu angelegten Gewässerabschnittes genommen. In diesem Zusammenhang stellt sich die Frage, welche morphologischen Veränderungen im System noch auf die Verlegung der Inde in ihr neues Gewässerbett und die daraus resultierenden Anpassungen zurückzuführen sind und inwieweit die Entwicklung der Inde nach Fertigstellung der Maßnahme im Jahr 2005 ein dynamisches Gleichgewicht erreicht hat. Dabei ist zu berücksichtigen, ob die heutige Morphodynamik leitbildkonform ist, ob zukünftig weiterhin fortschreitende Erosion stattfindet und welche Maßnahmen zur Vermeidung ungewollter Tiefenund Breitenerosion gegebenenfalls erforderlich werden. Zur Schaung eines „urnahen Grundwasserstandes in der Aue und zur Tagebausicherheit ist die Entwicklung nur bis zu einer künstlich eingebauten Abdichtungsschicht und innerhalb eines festgelegten Entwicklungskorridors möglich. Durch die Dichtungsschicht wird die Versickerung in den Untergrund begrenzt, um den natürlichen Niedrigwasserab„uss zu gewährleisten.

Abstract Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene–Holocene transition (~ 12 ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan ( Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer consideration of the fluvial influence on aeolian archives in palaeoenvironmental studies from central Asian and other drylands.

Abstract The Eltville Tephra (ET) is an important stratigraphic marker bed in the Western European loess stratigraphy at the boundary between the regional Last Glacial Maximum (LGM) in the sense of the maximum extent of glaciation of the Scandinavian ice sheet and a ‘terrestrial’ LGM with the highest degree of aridity and coldness. Stratigraphic marker beds such as tephra layers are commonly dated at more than one location, and often with more than one method. The sediments surrounding the ET were dated 87 times at 15 localities with different luminescence techniques yielding ages between 13.5 and 49.6 ka. Based on individual sections, the deposition of the ET was supposed to have taken place between 20 and 23 ka. This raises the question of whether a quantitative combination of individual ages can give a reproducible common age, including uncertainties. After screening the dataset and applying selection criteria, a Bayesian resampling approach is applied to obtain a common age consistent with a high percentage of observations from multiple localities. Four new luminescence ages bracketing the ET and two ages directly generated from the tephra horizon are presented and combined with all available data. The 1σ age range of the Bayesian age modelling yields a deposition age between 23.2 and 25.6 ka, which is in excellent agreement with two new luminescence ages from the tephra of 24.1 ± 1.9 ka (quartz) and 24.3 ± 1.8 ka (pIRIR290) and a peak of volcanic minerals in the Dehner Maar core around 24.3 ka. This age is clearly older than previously suggested for the ET volcanic eruption, but fits better with stratigraphic and paleoenvironmental evidence. Therefore, the ET was deposited during phases of strong aeolian activity of the Greenland Stadial 3. Additionally, for the first time, a correlation can be made between the ET and tephra layers recognized in the Eifel Maar lake cores.

Loess-paleosol sequences (LPSs) are important terrestrial archives of paleoenvironmental and paleoclimatic information. One of the main obstacles for the investigation and interpretation of these archives is the uncertainty of their age-depth relationship. In this study, four different dating techniques were applied to the Late Pleistocene to Holocene LPS Balta Alba Kurgan (Romania) in order to achieve a robust chronology. Luminescence dating includes analysis of different grain-size fractions of both quartz and potassium feldspar and the best results are obtained using fine-grained quartz blue‐stimulated and polymineral post-infrared infrared-stimulated luminescence measurements. Radiocarbon (14C) dating is based on the analysis of bulk organic carbon (OC) and compound-specific radiocarbon analysis (CSRA). Bulk OC and leaf wax-derived n-alkane 14C ages provide reliable age constraints for the past c. 25–27 kyr. CSRA reveals post-depositional incorporation of roots and microbial OC ...

Climate, geology, geomorphology, soil, vegetation, geomorphology, hydrology, and human impact affect river–floodplain systems, especially their sediment load and channel morphology. Since the beginning of the Holocene, human activity is present at different scales from the catchment to the channel and has had an increasing influence on fluvial systems. Today, many river–floodplain systems are transformed in course of river restorations to “natural” hydrodynamic and morphodynamic conditions without human impacts. Information is missing for the historical or rather “natural” as well as for the present-day situation. Changes of the “natural” sediment fluxes in the last centuries result in changes of the fluvial morphology. The success of river restorations depends on substantial knowledge about historical as well as present-day fluvial morphodynamics. Therefore, it is necessary to analyze the consequences of historical impacts on fluvial morphodynamics and additionally the future impli...

<p>Four M~8 earthquakes in the 20<sup>th</sup> century reflect active deformation in western Mongolia as a result of far-field stresses related to the India-Eurasia collision. Historic seismicity indicates that deformation localises around the relatively rigid Hangay dome in central Mongolia, however, tectonic lineaments in the surrounding Valley of Lakes basins suggest more widespread and diffuse deformation. In southern Mongolia, seismicity clusters around the Bogd fault, which ruptured during the 1957 Mw 8.1 Gobi Altai earthquake. To determine whether the kinematics interpreted from this earthquake are regionally representative, especially in consideration of the heterogeneity of intraplate tectonics, we expand the spatial scale of tectonic studies to range between the Gobi Altai and Hangay massifs. We do this by combining observations from regional and local digital elevation models, ground-penetrating radar analyses, geological and geomorphological field data, and seismic reflection data. Additionally, we increase the temporal scale of palaeoseismic studies up until the Middle Pleistocene through OSL and surface exposure dating, to compare the effects of tectonic processes to those of Quaternary climate variations on landscape evolution. We show that reverse and oblique strands of the Bogd fault accommodate <0.3 mm/yr vertical slip rates along the northern margin of the transpressive Gobi Altai massif. Four ~E-W striking faults in the seismically quiescent Valley of Gobi Lakes each have the potential for M~7 earthquakes and they are likely part of a left-lateral strike-slip system rooted at depth. Although cumulatively, the Valley of Gobi Lakes faults are deforming at a regionally representative ~0.3 mm/yr vertical slip rate, recurrence intervals of major earthquakes are much longer than those determined along the Bogd fault (~5-80 ka vs. 3-5 ka). Overall, we interpret the Valley of Gobi Lakes faults to have played a large role in drainage reorganisation and Middle Pleistocene to modern landscape evolution. Sub-surface faults interpreted from seismic reflection data and associated geomorphological irregularities in the Orog Nuur Basin indicate two NW-SE striking lineaments that may connect the Valley of Gobi Lakes fault system to the Bogd fault system. Our observations suggest a more complex and extensive fault system in southern Mongolia than previously expected and the geometry and potential connectivity of faults indicates a continuing northward progression of transpressive deformation from the Gobi Altai towards the Hangay. The obscurity of active deformation in the Valley of Gobi Lakes is likely due to faster erosion and deposition rates and this highlights the importance of understanding the interplay between tectonic, climatic and geomorphological processes and their effects on the landscape system. We suggest that, especially in slowly deforming, intraplate regions, an increase of spatial and temporal scales of active tectonic research is necessary to improve interpretations of tectonically altered landforms, palaeo-environmental reconstructions, and seismic hazard assessments.</p>

Background Over the last 200 years, the courses of most European rivers have experienced significant irreversible changes. These changes are connected to different kinds of anthropogenic river use and exploitation, which have varied from running water mills and rafting to large-scale hydroelectric power plants, industrial water withdrawal and flood protection measures. Today, in most developed countries, water quality and ecological river development are important factors in water management. The aim of this study is to evaluate the specific impacts of different time periods during the last 200 years on river courses and their effects on current river management using the example of the 165-km-long German Rur River (North Rhine-Westphalia). The Rur River is a typical central European upland-to-lowland river whose catchment has been affected by various phases of industrial development. Methods In this study, a range of morphological changes over the last 200 years are determined base...

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This study evaluates the applicability of trace element and organic contaminant data from a floodplain cross-section as the basis for a numerical model of spatial floodplain dynamics. Using threshold values of pollution-sensitive trace elements and market introduction dates of organic xenobiotics, the sampled sediment is assigned to historical phases to develop a sediment chronology. The investigation is based on a 60-m wide core transect from which sediment samples were analyzed to determine grain-size distribution, trace element inventory, and organic xenobiotic content. In addition, floodplain inundation, flow velocities, and the amount of sediment deposited were numerically modeled using Delft3D to verify the analyses results; conversely, the results of the sedimentary analysis served the input data for the model. Changes in floodplain morphology were interpreted on the basis of a digital elevation model (1 m resolution), historical maps from 1865 AD, and field surveys. The architecture of the alluvial sediments was examined in the cores accounting recent floodplain relief and possible historical factors. The results show a broad range of heavy metal pollutants and the presence of 57 volatile organic compounds in a pattern that reflects multiple deposition processes and phases. Based on these results and the model verification, the sediments were assigned to pre-industrial, industrial, and post-industrial phases, and sedimentation rates of 0.6–1.3 cm a−1 were estimated. The results of this study contribute to a better understanding of the development of small meandering gravel-bed rivers with large floodplains, where suspended sediments predominate.

This study describes the luminescence characteristics of quartz of Upper Pleistocene loess of the Middle Rhine area. The loess/palaeosol sequence of the Schwalbenberg near Remagen com-prises a multitude of interstadial soils and soil sediments that have been dedicated to the Marine Iso-tope Stage 3 (MIS 3). These weak calcaric cambisols and their derivates are underlain by loess and soil sediments of MIS 4 to MIS 5 and covered by loess sediments and intercalated gelic gleysols of MIS 2. We applied luminescence dating of quartz and feldspar of drill core samples and observed an age discrepancy within both data sets. The quartz ages were clearly younger than the feldspar ages, because of thermally unstable signal components of the quartz luminescence signal. Therefore, we re-garded the quartz samples of the lower parts of the drill core as unsuitable for luminescence dating. This underestimation did not affect the quartz samples of the upper part of the drill core which was indicated ...

The northeastern part of Eurasia represents one of Earth‟s most extreme periglacial climate regions, characterized by the strongest seasonal temperature amplitudes on the northern hemisphere. The region is occupied by deep-reaching permafrost and covered by widespread taiga and tundra vegetation (Muller et al., 2010). Paleoenvironmental studies have been conducted close to the northern polar cycle in the Verkhoyansk Mountain Range and its western foreland to infer periglacial landscape dynamics in response to late Quaternary climate change. The distribution of preserved terminal moraines reveal several mountain glacier advances in the past (Stauch and Lehmkuhl, 2010). According to luminescence dating, the widest geologically documented glacial advence took place during the Saalian stage around 135 ka. Less extended glaciations to the foreland appeared during the early Weichselian at 100-120 ka and at 85-90 ka, while the youngest glaciation (>50 ka) was confined to the mountain area. No regional glacial advance is evident for the late Weichselian and the last glacial maximum, a time which was characterized by aeolian loess formation (Stauch et al., 2007, Popp et al., 2007). Sediment cores from the 25 m deep Lake Billyakh (340 m a.s.l.), a former proglacial basin, document environmental changes of the last 50 kyr (Diekmann et al., 2007). Pollen records indicate a dry climate for the late Weichselian, indicated by a change from tundra towards cold steppe vegetation after 32 ka until 13.5 ka BP (Muller et al., 2009, 2010). For the same time, sedimentological and diatom data indicate a lake level drop. Modelling experiments with a general circulation model suggest that the consecutive decline in the extent of mountain glaciers and increase in dryness through the Weichselian was dictated by the growing shielding effect of the western Eurasian ice sheets that prevented the supply of moist Atlantic air masses to eastern Siberia (Krinner et al., 2011). In addition, enhanced deposition of dust reduced the albedo and promoted ice and snow melting during summer (Krinner et al., 2011). Environmental changes towards interglacial conditions of the Holocene are documented in the Lake Billyakh deposits (Muller et al., 2009) as well as in a peat section at Dyanushka River (Werner et al., 2009). Both records show that climate amelioration started after 13.5 ka BP with the quick return of larch trees that also persisted during the Younger Dryas cold spell, suggesting that the Verkhoyansk Mountain area possibly represented a plant refugium during the climate extremes of the last ice age (Tarasov et al., 2009). Reforestation continued since 11.4 ka BP with the spread of boreal cold deciduous and taiga forests and reached a maximum extent after 7 ka BP. Limnological conditions of Lake Billyakh changed to a higher lake-level and increased biological productivity consistent with climate warming and increased humidity. Mean July air temperatures reconstructed by fossil aquatic chironomids, using a regional inference model (Nazarova et al., 2011), indicate warmest summer temperatures between roughly 9.0 and 6.6 ka BP. The stable-isotope composition of ice wedges in permafrost soils point to warmer winters during the early Holocene compared to the late Holocene (Popp et al, 2006). The recognition of a regional early Holocene climate optimum is consistent with long-term Holocene climate development in wide parts of northern Eurasia. References Diekmann, B., Andreev, A.A., Muller, G., Lupfert, H., Pestryakova, L., Subetto, D., 2007. Expedition 'Verkhoyansk 2005' - Limnogeological studies at Lake Billyakh, Verkhoyansk Mountains, Yakutia. In: Schirrmeister, L. (ed.): Expeditions in Sibiria in 2005, Reports on Polar and Marine Research, 550: 247-258. Krinner, G., Diekmann, B., Colleoni, F., Stauch, G., 2011. Global, regional and local scale factors determining glaciation. Quaternary Science Reviews, 30: 821-831. Muller, S., Tarasov, P. E., Andreev, A., Diekmann, B., 2009. Late Glacial to Holocene environments in the present-day coldest region of the Northern Hemisphere inferred from a pollen record of Lake Billyakh, Verkhoyansk Mts ., NE Siberia. Climate of the Past 5: 73-84. Muller, S., Tarasov, P.E., Andreev, A.A., Tuetken, T., Gartz, S., Diekmann, B., 2010. Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh. Quaternary Science Reviews, 29: 2071-2086. Nazarova, L., Herzschuh, U., Wetterich, S., Kumke, T., Pestryakova, L., 2011. Chironomid-based inference models for estimating mean July air temperature and water depth from lakes in Yakutia, northeastern Russia. Journal of Paleolimnology, 45(1): 57-71. Popp, S., Belolyubsky, I., Lehmkuhl, F., Prokopiev, A., Siegert, C., Spektor, V., Stauch, G., Diekmann, B. (2007): Sediment provenance of late Quaternary morainic, fluvial and loess-like deposits in the southwestern Verkhoyansk…

The Titel loess plateau in the Vojvodina region of Serbia is considered to contain the most detailed terrestrial paleoclimatic records in Eu-rope, with a thick and apparently continuous record extending through the middle and late Early Pleistocene. In the past few decades the plateau has been investigated on a fairly large scale and has provided important records of climatic and environmental changes during the Pleisto-cene in this part of Europe. Regardless the extensive research in the past, high detailed optically stimulated luminescence (OSL) dating of the Ti-tel loess plateau has not yet been conducted on the site, despite having been shown in China to be essential in development of reliable chronologies and in accurate reconstruction of the last two glacial-interglacial cycles. The absence of a detailed independent chronology limits the pale-oclimatic interpretations possible from this valuable archive. In order to obtain detailed stratigraphic, climatic and chronological information from the plateau, two cores were drilled in the northern area of the plateau, near the village of Mošorin (45.296225 N 20.188648 E). The first core (TLP 1) was drilled to a depth of 22.93 m while the second one (TP 1A) was drilled to a depth of 21.42 m. The two cores were drilled side by side, covering about the same stratigraphic depths. Sampling for equivalent dose determination using the Single Aliquot Regeneration (SAR) protocol was undertaken in continuous sections at 13-15 cm resolu-Loess2M – modelling & mapping 33

This contribution focuses on two PhD projects, which are integrated within the collaborative research centre 806 “Our way to Europe” at the University of Cologne and the RWTH Aachen University (Germany). The main research focus is the migration of anatomical modern human (AMH) to Europe. We concentrate on the paleoenvironmental conditions on the route through southeastern Europe. This links the region with the earliest fossils of Homo sapiens sapiens (so far known) in the Middle East, Anatolia, the Northwestern Black Sea, the Balkans and the Pannonian Basin. One PhD topic deals with the sedimentological and geochemical approach mainly from loess and loess-like sediments to reconstruct the paleoenvironmental conditions; the other PhD topic places an emphasis on the exact timing of those sedimentary records via luminescence dating. In particular the investigation of loess-paleosol sequences plays a central role. Geoarchives in Hungary, Serbia and Romania are of main interest for the p...