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The hydrogen isotope composition of leaf-wax-derived biomarkers, e.g., long-chain n-alkanes (δ2Hn-alkane), is widely applied in paleoclimate. However, a direct reconstruction of the isotope composition of source water based on δ2Hn-alkane alone is challenging due to the enrichment of heavy isotopes during evaporation. The coupling of δ2Hn-alkane with δ18O of hemicellulose-derived sugars (δ18Osugar) has the potential to disentangle this limitation and additionally to allow relative humidity reconstructions. Here, we present δ2Hn-alkane as well as δ18Osugar results obtained from leaves of Eucalyptus globulus, Vicia faba, and Brassica oleracea, which grew under controlled conditions. We addressed the questions of (i) whether δ2Hn-alkane and δ18Osugar values allow reconstructions of leaf water isotope composition, (ii) how accurately the reconstructed leaf water isotope composition enables relative humidity (RH) reconstruction, and (iii) whether the coupling of δ2Hn-alkane and δ18Osugar enables a robust source water calculation. For all investigated species, the n-alkane n-C29 was most abundant and therefore used for compound-specific δ2H measurements. For Vicia faba, additionally the δ2H values of n-C31 could be evaluated robustly. Regarding hemicellulose-derived monosaccharides, arabinose and xylose were most abundant, and their δ18O values were therefore used to calculate weighted mean leaf δ18Osugar values. Both δ2Hn-alkane and δ18Osugar yielded significant correlations with δ2Hleaf water and δ18Oleaf water, respectively (r2=0.45 and 0.85, respectively; p, n=24). Mean fractionation factors between biomarkers and leaf water were found to be −156 ‰ (ranging from −133 ‰ to −192 ‰) for εn-alkane/leaf water and +27.3 ‰ (ranging from +23.0 ‰ to 32.3 ‰) for εsugar/leaf water, respectively. Modeled RHair values from a Craig–Gordon model using measured Tair, δ2Hleaf water and δ18Oleaf water as input correlate highly significantly with modeled RHair values (R2=0.84, p, RMSE = 6 %). When coupling δ2Hn-alkane and δ18Osugar values, the correlation of modeled RHair values with measured RHair values is weaker but still highly significant, with R2=0.54 (p, RMSE = 10 %). Finally, the reconstructed source water isotope composition (δ2Hs and δ18Os) as calculated from our coupled approach matches the source water in the climate chamber experiment (δ2Htank water and δ18Otank water). This highlights the great potential of the coupled δ2Hn-alkane–δ18Osugar paleohygrometer approach for paleoclimate and relative humidity reconstructions.

Time and circumstances for the disappearance of Neanderthals and its relationship with the advent of Modern Humans are not yet sufficiently resolved, especially in case of the Iberian Peninsula. Reconstructing palaeoenvironmental conditions during the last glacial period is crucial to clarifying whether climate deteriorations or competition and contacts with Modern Humans played the pivotal role in driving Neanderthals to extinction. A high-resolution loess record from the Upper Tagus Basin in central Spain demonstrates that the Neanderthal abandonment of inner Iberian territories 42 kyr ago coincided with the evolvement of hostile environmental conditions, while archaeological evidence testifies that this desertion took place regardless of modern humans’ activities. According to stratigraphic findings and stable isotope analyses, this period corresponded to the driest environmental conditions of the last glacial apart from an even drier period linked to Heinrich Stadial 3. Our results show that during Marine Isotope Stages (MIS) 4 and 2 climate deteriorations in interior Iberia temporally coincided with northern hemisphere cold periods (Heinrich stadials). Solely during the middle MIS 3, in a period surrounding 42 kyr ago, this relation seems not straightforward, which may demonstrate the complexity of terrestrial climate conditions during glacial periods.

Mountain glaciers are very sensitive to (past) climate changes. Paleoglaciation of the Tibetan Plateau and the Himalaya received plenty of attention for the reconstruction of past climate and environmental conditions, whereas few studies have been conducted so far in the adjacent Altai and Sayan Mountains in Siberia, although they promise a complex history. The investigated Sayan Mountains in the Russian Altai indicate extensive glacial activity during the Pleistocene and a shifting of the local Last Glacial Maximum (LGM). Rich glacial residues in terms of moraine ridges and erratic boulders in the region provide excellent opportunities to establish a detailed age chronology using in-situ cosmogenic ¹⁰Be surface exposure dating and derive information about paleoclimatic conditions. We present 28 ¹⁰Be surface exposure ages from the Ergaki Range and Tuva Uplands in the western Sayan Mountains. Distinct lateral moraines document the extents of former glaciation during a last glacial maximum. Several recessional moraines in the Ergaki Range additionally record stand stills or readvances during the last glacial termination. The prominent lateral moraine in the Ergaki Range yields three exposure ages of ~19 ka, indicating a MIS 2 glaciation. The maximum advances correlate with the end of the global LGM. Concluding, glaciers in the Ergaki Range existed continuously during the late Pleistocene only varying in their extent. The well-clustered ages of the Ergaki Range provide a robust deglaciation chronology. The readvances/ stand stills consistently date to ~18 ka (three boulders), ~17.5 ka (two boulders), ~17 ka (three boulders), and ~16 ka (two boulders), with a deglaciation starting after 16 ka. The valley is not elevated enough to record younger, less extensive glaciation, e.g. during the Younger Dryas and the Holocene. Exposure ages from the Tuva Uplands are more difficult to interpret: The lateral moraine documenting the most extensive glaciation yields two exposure ages of ~22 ka. The immediately adjacent inner lateral moraine has two slightly younger and stratigraphically consistent ages of ~21 ka, yet three more boulders from that moraine are ~27 and 43 ka. At this point, we suspect these older boulders to have inheritance, but we cannot confidently exclude a much older deposition age for both moraines. Planned are analyzes of other cosmogenic nuclides, such as ²⁶Al and/or in situ ¹⁴C, which might help to more robustly identify inheritance and complex exposure histories.

During the last decade compound-specific deuterium (δ2H) analysis of plant leaf wax-derived n-alkanes has become a promising and popular tool in paleoclimate research. This is based on the widely accepted assumption that n-alkanes in soils and sediments generally reflect δ2H of precipitation (δ2Hprec). Recently, several authors suggested that δ2H of n-alkanes (δ2H,sub>n-alkanes) can also be used as proxy in paleoaltimetry studies. Here we present results from a δ2H transect study (~1500 to 4000 m a.s.l.) carried out on precipitation and soil samples taken from the humid southern slopes of Mt. Kilimanjaro. Contrary to earlier suggestions, a distinct altitude effect in δ2Hprec is present above ~2000 m a.s.l., i.e. δ2Hprec values become more negative with increasing altitude. The compound-specific δ2H values of nC27 and nC29 do not confirm this altitudinal trend, but rather become more positive both in the O-layers (organic layers) and the Ah-horizons (mineral topsoils). Although our δ2Hn-alkane results are in agreement with previously published results from the southern slopes of Mt. Kilimanjaro (Peterse et al., 2009, BG, 6, 2799–2807), a major re-interpretation is required given that the δ2Hn-alkane results do not reflect the δ2Hprec results. The theoretical framework for this re-interpretation is based on the evaporative isotopic enrichment of leaf water associated with transpiration process. Modelling results show that relative humidity, decreasing considerably along the southern slopes of Mt. Kilimanjaro (from 78% at ~ 2000 m a.s.l. to 51% at 4000 m a.s.l.), strongly controls δ2Hleaf water. The modelled δ2H leaf water enrichment along the altitudinal transect matches well the measured 2H leaf water enrichment as assessed by using the δ2Hprec and δ2Hn-alkane results and biosynthetic fractionation during n-alkane biosynthesis in leaves. Given that our results clearly demonstrate that n-alkanes in soils do not simply reflect δ2Hprec but rather δ2Hleaf water, we conclude that care has to be taken not to over-interpret δ2Hn-alkane records from soils and sediments when reconstructing δ2H of paleoprecipitation. Both in paleoaltimetry and in paleoclimate studies changes in relative humidity and consequently in δ2Hn-alkane values can completely mask altitudinally or climatically-controlled changes in δ2Hprec.

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied 10Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.

Während der Eiszeiten sind wiederholt die Gletscher aus den Alpen bis weit in das Schweizer Mittelland vorgestossen. Genaues Ausmass und Zeitpunkt sind selbst für die letzte Vergletscherung umstritten. Publizierte 10Be Expositionsalter von Findlingen auf dem Niederbippstadium des Rhone-Aare-Gletschers dokumentieren scheinbar den maximalen Vorstoss während der letzten Vergletscherung vor ca. 24 ka. Allerdings ist die Bodenentwicklung auf dem Niederbippstadium deutlich fortgeschrittener (Entkalkungstiefen von 3 bis 4 m) als die Bodenentwicklung auf dem Bern- und Gurtenstadium mit vermuteten Altern von ca. 18 – 20 ka (Entkalkungstiefen dort 10Be Expositionsalter bestimmt. Die ältesten drei von sechs Findlingen vom Bernstadium liefern Expositionsalter um ca. 18 ka und dokumentieren den Gletscherstand des Aaregletschers kurz vor dem endgültigen und raschen Zerfall der Vorlandgletscher am Ende der letzten Eiszeit. Zwei von fünf Findlingen vom Gurtenstadium haben Expositionsalter um 20 ka und zeigen, dass der Aaregletscher zu diesem Zeitpunkt noch sehr viel grösser war. Auf beiden Stadien gibt es deutlich “zu junge” Expositionsalter, die höchstwahrscheinlich mit Erosion, geomorphologischer Instabilität, und menschlicher Aktivität erklärt werden müssen. Es kann bisher nicht vollständig ausgeschlossen werden, dass die Expositionsalter des Niederbippstadium ebenfalls “zu jung” sind. Dann liesse sich die Bodenentwicklung auf dem Niederbippstadium problemslos erklären. Dokumentieren die Expositionsalter tatsächlich den maximalen Gletschervorstoss vor 24 ka, muss davon ausgegangen werden, dass die mächtige Entkalkung und Tonverlagerung dort in wenigen tausend Jahren, und vor allem unter glazialen Bedingungen stattgefunden hat. Weitere Findlinge sind daher im Moment in Bearbeitung, um den Zeitpunkt der maximalen, letztglazialen Vergletscherung zu klären.

The hydrogen isotopic composition (δ 2H) of leaf waxes, especially of n-alkanes (δ 2Hn−alkanes), is increasingly used for paleohydrological and paleoclimate reconstructions. However, it is challenging to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water, which are both recorded in leaf wax δ 2H values. In order to overcome this limitation, Zech M. et al. (2013) proposed a coupled δ 2Hn−alkane–δ 18Osugar biomarker approach. This coupled approach allows for calculating (i) biomarker-based “reconstructed” δ 2H/δ18O values of leaf water (δ 2H/δ18Oleaf water), (ii) biomarker-based reconstructed deuterium excess (dexcess) of leaf water, which mainly reflects evapotranspirative enrichment and which can be used to reconstruct relative air humidity (RH) and (iii) biomarker-based reconstructed δ 2H/δ18Oprecipitation values. Here we present a climate transect validation study by coupling new results from δ 2H analyses of n-alkanes and fatty acids in topsoils along a climate transect in Argentina with previously measured δ 18O results obtained for plantderived sugars. Accordingly, both the reconstructed RH and δ 2H/δ18Oprecipitation values correlate highly significantly with actual RH and δ 2H/δ18Oprecipitation values. We conclude that compared to single δ 2Hn−alkane or δ 18Osugar records, the proposed coupled δ 2Hn−alkane–δ 18Osugar biomarker approach will allow more robust δ 2H/δ18Oprecipitation reconstructions in future paleoclimate research. Additionally, the proposed coupled δ 2Hn−alkane–δ 18Osugar biomarker approach allows for the establishment of a “paleohygrometer”, more specifically, the reconstruction of mean summer daytime RH changes/history Fil: Tuthorn, M.. University Of Bayreuth; Alemania Fil: Zech, R.. ETH Zurich. Geological Institute; Suiza Fil: Ruppenthal, M.. University of Tübingen; Alemania Fil: Oelmann, Y.. University of Tübingen; Alemania Fil: Kahmen, A.. University of Basel. Department of Environmental Sciences – Botany; Suiza Fil: del Valle, Hector Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Eglinton, T.. ETH Zurich. Geological Institute; Suiza Fil: Rozanski, K.. AGH University of Science and Technology. Faculty of Physics and Applied Computer Science; Polonia Fil: Zech, R.. University Of Bayreuth; Alemania. Martin-Luther University. Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry; Alemania

Paleoenvironmental and paleoclimate reconstructions based on molecular proxies, such as those derived from leaf wax biomarkers, in loess-paleosols sequences represent a promising line of investigation in Quaternary research. The main premise of such reconstructions is the synsedimentary deposition of biomarkers and dust, which has become a debated subject in recent years. This study uses two independent approaches to test the stratigraphic integrity of leaf-wax biomarkers: (i) Long-chain n-alkanes and fatty acids are quantified in two soil profiles in till on the Swiss Plateau. Since glacial sediments are extremely poor in organic matter, significant amounts of leaf-wax biomarkers in the lower part of those profiles would reflect post-sedimentary root-derived or microbial contributions. (ii) Compound-specific radiocarbon measurements are conducted on n-alkanes and fatty acids from several depth intervals in the loess section "Crvenka", Serbia, and the results are compared to independent estimates of sediment age. We find extremely low concentrations of plant wax n-alkanes and fatty acids below the topsoils in the soil profiles. Moreover, compound-specific radiocarbon analysis yields plant wax 14C ages that agree well with published luminescence ages and stratigraphy of the Serbian loess deposit. Both approaches confirm that post-sedimentary, root-derived or microbial contributions are negligible in the two systems investigated. The good agreement between n-alkane and fatty acid ages, as well as between odd and even homologues, further indicates that reworking and incorporation of fossil leaf-waxes is not particularly relevant either.

Mountain glaciers are sensitive indicators for climate change, mainly summer temperature and precipitation. Glacial chronologies from Central Asia have therefore been suggested to provide valuable information about past changes in temperature, as well as precipitation and related changes in atmospheric circulation. However, available age control is still sparse. Here we present a glacial chronology for the Gissar Range, Tajikistan, based on thirteen 10Be surface exposure ages. Prominent moraine lobes document glacial advances in phase with the global last glacial maximum (LGM) during marine isotope stage (MIS) 2. Rapid and significant deglaciation occurred already at ~20 ka as inferred from recessional stages. An older and slightly more extensive glaciation could be dated to MIS 4, whereas the timing of the most extensive glaciation remains speculative. In contrast to the glacial chronologies from the nearby, more arid Pamir and Tien Shan, where MIS 3 and MIS 5 moraines likely document past periods with increased precipitation, glaciers in the more humid Gissar Range predominantly recorded past changes in temperature and summer insolation.

The Pamir Mountains have been extensively glaciated several times in the past. As glaciers are mainly sensitive to variations in temperature and precipitation, they reflect changes in large-scale atmospheric circulation patterns. The Pamir Mountains are situated in a climatic transition zone between mid-latitude westerlies, the Indian summer monsoon and the Siberian High. Today main moisture to the Pamir comes with SW-cyclones along the westerly jetstream. Up to now the impact of the Indian monsoon on former glaciations of the Pamir Mountains has not yet been adequately examined. Even chronological information about former glaciations in the Pamir are still sparse. The objective of our study is: To upgrade the present glacial chronology by 10Be surface exposure dating of erratic boulders on top of moraines along a moisture gradient from the north-western to the southern Pamir Mountain ranges. We present preliminary 10Be ages from moraine successions of three study sites (Iskenderkul area, Muksu-Kyslsu area, Alichur area). Our first results from the southern Pamir (Alichur area) corroborate and refine previously published findings: Extensive glaciation occurred during MIS 4 and during MIS 2 coinciding with lower insolation intensity. Because during climatic cold phases the Indian Monsoon was weakened we assume that these glacier advances were mainly triggered by westerly moisture supply. However, our data indicate that glaciers in the southern Pamir also advanced during ~58 to ~45 ka as also observed in monsoonal influenced Karakoram and eastern Hindu Kush regions. Our surface exposure ages point to rapid deglaciation after ~18 ka. So far there is no evidence for glacier advances during the Holocene. Analyses of further samples, from both the Muksu-Kyzlsu area and the Iskenderkul area are in progress.

The reconstruction of past climate changes in the Pamir Mountains has high potential for identifying the dynamics of circulation systems in Asia and for understanding global environmental changes during the Late Quaternary. The Pamir Mountains are situated in a climatic transition zone between mid-latitude westerlies, the Indian summer monsoon and the Siberian High. Today main moisture to the Pamir comes with SW- cyclones along the westerly jetstream whereas the influence of the Indian monsoon typically ends south of the NW-Himalaya. Up to now the impact of the Indian monsoon on former glaciations of the Pamir Mountains has not yet been adequately examined. Even chronological information about former glaciations in the Pamir is still sparse. The objectives of our study are: To upgrade the present glacial chronology by dating glacial successions along a moisture gradient from the north-western to the southern Pamir Mountain ranges. We present preliminary 10Be ages from moraine successions of three study sites (Iskenderkul area, Muksu-Kyzlsu area, Alichur area). Our first results from the southern Pamir (Alichur area) corroborate and refine previously published findings: Extensive glaciation occurred during MIS 4 and during MIS 2. However our data indicate that glaciers in the southern Pamir also advanced during ~50 to 40 ka. Rapid deglaciation occurred after ~18 ka. So far there is no evidence for glacier advances during the Holocene. Overall, we conclude that the glacial chronology of the Pamir seems to be mainly controlled by temperature, with maxima during ~70 to 60 ka, ~50 to 40 ka and ~20 ka. Because during climatic cold phases the Indian Monsoon was weakened, we assume that glacier advances in the Pamir Mountains during the Last Glacial cycle were mainly triggered by westerly moisture supply. Analyses of further samples, from both the Muksu-Kyzlsu area and the Iskenderkul area are in progress.