Sedimentology and Stratigraphy of the Pleistocene sediments in Lake Llauset (Southern Pyrenees, Spain)-a first approach

The high alpine valleys in the Southem Pyrenees are characterised by a many small lakes and ponds. They occur above 2000 m and are said to have been formed by glacial erosion. The sediments in these basins should, therefore, contain s t p tigraphic information since deglaciation, at least. An interesting and may be one of the most important of these basins is Lake Llauset in the Alta Ribagorca. The Llauset basin has recently been developped for hydsopower production. In conection with the construction of the retaining wall at the 'Riegel' the sedimentary filling of the lake basin could be investigated, and the first sedimentological and stratigraphicalresults are presented

Distribution, geometry, age and origin of overdeepened valleys and basins in the Alps and their foreland

Overdeepened valleys and basins are commonly found below the present landscape surface in areas that were affected by Quaternary glaciations. Overdeepened troughs and their sedimentary fillings are important in applied geology, for example, for geotechnics of deep foundations and tunnelling, groundwater resource management, and radioactive waste disposal. This publication is an overview of the areal distribution and the geometry of overdeepened troughs in the Alps and their foreland, and summarises the present knowledge of the age and potential processes that may have caused deep erosion. It is shown that overdeepened features within the Alps concur mainly with tectonic structures and/or weak lithologies as well as with Pleistocene ice confluence and partly also diffluence situations. In the foreland, overdeepening is found as elongated buried valleys, mainly oriented in the direction of former ice flow, and glacially scoured basins in the ablation area of glaciers. Some buried deeply incised valleys were generated by fluvial down-cutting during the Messinian crisis but this mechanism of formation applies only for the southern side of the Alps. Lithostratigraphic records and dating evidence reveal that overdeepened valleys were repeatedly occupied and excavated by glaciers during past glaciations. However, the age of the original formation of (non-Messinian) overdeepened structures remains unknown. The mechanisms causing overdeepening also remain unidentified and it can only be speculated that pressurised meltwater played an important role in this contex

Schotterpetrologie und deren relativ-stratigraphische Anwendbarkeit im Aaretal südlich von Bern (Schweiz)

Schotterpetrologische Untersuchungen im Aaretal südlich von Bern zeigen, daß die petrologische Zusammensetzung der Fraktion > 2 cm von älteren zu jüngeren Schotterakkumulationen gesetzmäßig ändert. Die ältesten, bis jetzt nachgewiesenen pleistozänen Schotter im Aaretal, die Bümbergschotter, sind reich an aufgearbeitetem Mollassematerial (>15 %), welches in den letzteiszeitlichen Münsingenschottern, bzw. spätglazialen Wichtrachschottern <10% beträgt (Abb. 2). Bei den Münsingenschottern (Obere und Untere als Einheit betrachtet) kann östlich und westlich des heutigen Aarelaufes eine verschiedene Fazies in der Geröllführung nachgewiesen werden (Abb. 3). Das von Cadisch (1928) beobachtete Widerspiegeln der Heraushebungs- und Erosionsgeschichte des Alpenkörpers in der Petrologie der Molassesedimente gilt auch für die petrologische Geröllzusammensetzung der mittel- bis jungpleistozänen Schotterakkumulationen.researc

Die früheren Vergletscherungen in Anatolien: - Ein schematischer Rückblick & erste Ergebnisse

Anatolia is situated in the Eastern Mediterranean region between 36 – 42N and 26 – 45E. The geological records of paleoglaciations in the high terrains of Anatolia are key archives to quantify paleoclimate change in the Eastern Mediterranean area. The climate of the Eastern Mediterranean region is influenced by three main atmospheric systems: the main middle to high latitude westerlies, the mid-latitude subtropical high-pressure systems, and the monsoon climate. Glacial geological studies in Turkey have started in the late 19th century. Glacial deposits are found mainly in the eastern, northeastern and southern part of the Anatolian Peninsula. Anatolia is the fundamental element to understand the interactions between paleoenvironment, climatic variations, and development of the human societies. As the Taurus and Black Sea Mountains are sensitively situated for the paleoclimatic reconstructions, a chronostratigraphic framework on the paleoglaciation should be elaborated. The timing of the Last Glacial Maximum (LGM) in Anatolia is still unknown. Our first results from Kavron Valley (Kaçkar Mountains, NE Turkey) are encouraging for the reconstruction of paleoglaciations in Turkey and related paleoclimatological interpretations although it is presently difficult to pinpoint the classical Last Glacial Maximum – Younger Dryas – Little Ice Age moraine sequences in the field.Die spezielle geographische Lage der Türkei nordöstlich vom Mittelmeer zwischen 36 und 42 N, bzw. zwischen 26 und 45 E macht sie für Klima- und Paläoklimastudien zu einem besonders zentralen und sensiblen Gebiet. Der Vergletscherungsgeschichte von Anatolien kommt demzufolge eine Schlüsselrolle bei der Bewertung von Klimaveränderungen im östlichen Mittelmeerraum zu. Bereits aus dem späten 19. Jahrhundert sind glazialgeologischse Studien aus der Türkei bekannt. Vergletscherungsspuren sind vorwiegend in den östlichen, nordöstlichen und südlichen Gebirgszügen von Kleinasien vorhanden: in den Gebirgen am Schwarzen Meer, im Taurus, in den ostanatolischen Bergen, dem Uludağ und auf isolierten Vulkanen wie Erciyes, Süphan und Ararat. Das Klima im östlichen Mittelmeerraum ist hauptsächlich durch drei atmosphärische Strömungen geprägt: westliche Höhenströmungen der mittleren und höheren Breiten, subtropische Hochdruckgebiete der mittleren Breiten und der Monsun. Der Transport von Feuchtigkeit ist die zentrale Bestimmungsgröße für die Niederschlagsverteilung in diesem Gebiet. Für die Feuchtigkeitszufuhr in die Gebirge Kleinasiens während der pleistozänen Kaltzeiten sind Lage und Maxima der Jetstreams wichtig. Gletscher und ihre Ablagerungen sind in diesem Zusammenhang zentrale Archive für Klimarekonstruktionen Amplitude und Frequenz von eiszeitlichen Gletscherschwankungen müssen möglichst präzise erfasst werden, um Aussagen über die eiszeitliche atmosphärischen Zirkulationen – wie in den Alpen – machen zu können. Dies ist für Kleinasien auch zudem wichtig und interessant, weil diese Gegend seit Jahrtausenden intensive besiedelt ist. Das Alter der letzten maximalen Vereisung in Anatolien ist bisher unbekannt. Unsere ersten Ergebnisse aus dem Kavrontal (Kaçkar Gebirge, NE Türkei) sind vielversprechend in bezug auf die Rekonstruktion früherer Vergletscherungen in der Türkei und daraus folgenden Interpretationen über die paläoklimatologischen Verhältnisse. Es ist im Augenblick jedoch schwierig die im Gelände unterscheidbaren Moränensequenzen mit den klassischen Vereisungsstadien (Letztes Glaziales Maximum, Jüngere Dryaszeit, Kleine Eiszeit) zu verknüpfen

Post-depositional impacts on ‘Findlinge' (erratic boulders) and their implications for surface-exposure dating

Understanding and interpretation of ‘numbers' produced about the depositional age of an erratic boulder by cosmogenic nuclide surface-exposure dating is important in the construction of glacial chronology. We have sampled three ‘Findlinge' (glacially transported boulders) located on the right-lateral margin of the Aare glacier at Möschberg, Grosshöchstetten, southeast of Bern, with the aim of shedding light on this topic. The boulders have the same depositional, but different post-depositional histories: simple exposure; exhumation; and human impact. This sampling is specially selected for this study, since the boulders showing exhumation and human impact would not have been sampled in a regular surface-exposure dating application. We measured cosmogenic 10Be concentrations and calculated apparent exposure ages that are 13.6±0.5, 18.1±0.8, and 7.5±0.4ka, respectively. The exposure age of the first boulder reflects exhumation. The apparent exposure age of 18.1±0.8ka (erosion-corrected exposure age 19.0±0.9ka) from the second boulder correlates well with the end of the Alpine and global last glacial maximum. The third boulder shows evidence of quarrying as it is surrounded by a rim of excavation material, which is also reflected by the 7.5±0.4ka apparent exposure age. We modeled the variation of 10Be concentrations with depth down into the sediment in which the first (exhumed) boulder was once buried in, and down into the third (quarried) boulder. According to our modeling, we determined that the exhumed ‘Findling' was buried in sediment at a depth of around 0.5m, and around 2m of rock was quarried from the third ‘Findling'. Our results reveal the importance of sampling for surface-exposure dating within a well defined field context, as post-depositional impacts can easily hinder exposure-dating of surface

Pliocene Paleoenvironment and Antarctic Ice Sheet Behavior: Evidence from Wright Valley

Investigations in Wright Valley, adjacent to the Transantarctic Mountains in East Antarctica, shed light on the question of whether high-latitude Pliocene climate was warm enough to cause widespread deglaciation of the East Antarctic craton with a concurrent Magellanic moorland-like environment. If Pliocene age diatoms, presently in glaciogenic deposits high in the Transantarctic Mountains, had come from seaways on the East Antarctic craton, an expanding Late Pliocene ice sheet must have first eroded them from marine sediments and then deposited the diatoms at their present high-altitude locations. This hypothetical expanding glacier would have had to have come through Wright Valley. Glacial drift sediments from the central Wright Valley were mapped, sampled, analyzed, and Ar-40/Ar-39 whole rock dated. Our evidence indicates that an East Antarctic outlet glacier has not expanded through Wright Valley, and hence cannot have overridden the Dry Valleys sector of the Transantarctic Mountains, any time in the past 3.8 myr. Rather, there was only moderate Pliocene expansion of local cola-based alpine glaciers and continuous cold-desert conditions in Wright Valley. Persistence of a cold-desert paleoenvironment implies that the sector of the East Antarctic Ice Sheet adjacent to Wright Valley has remained relatively stable without melting ablation zones since at least 3.8 Ma, in Early Pliocene time. A further implication is that Antarctic Ice Sheet behavior in the Pliocene was much like that in the Quaternary, when the ice sheet consisted of a stable, terrestrial core in East Antarctica and a dynamic, marine-based appendage in West Antarctica

Larch Cellulose Shows Significantly Depleted Hydrogen Isotope Values With Respect to Evergreen Conifers in Contrast to Oxygen and Carbon Isotopes

The analysis of the stable isotope of the tree-ring cellulose is an important tool for paleo climatic investigations. Long tree-ring chronologies consist predominantly of oaks and conifers in Europe, including larch trees (Larix decidua) and cembran pines (Pinus cembra) that form very long tree ring chronologies in the Alps and grow at the treeline, where tree growth is mainly determined by temperature variations. We analyzed δ13C, δ18O and δ2H isotopes in the cellulose extracted from tree-rings of wood samples collected at high altitude in the Swiss and Tyrol Alps, covering the whole Holocene period. We found that larch cellulose was remarkably more depleted in deuterium than that of cembran pine, with mean δ2H values of −113.4 ± 9.7‰ for larch and of −65.4 ± 11.3‰ for cembran pine. To verify if these depleted values were specific to larch or a property of the deciduous conifers, we extended the analysis to samples from various living conifer species collected at the Bern Botanical Garden. The results showed that not only the larch, but also all the samples of the deciduous larch family had a cellulose composition that was highly depleted in δ2H with regard to the other evergreen conifers including cembran pine, a difference that we attribute to a faster metabolism of the deciduous conifers. The δ18O values were not statistically different among the species, in agreement with the hypothesis that they are primary signals of the source water. While the δ13C values were slightly more depleted for larch than for cembran pine, likely due to metabolic differences of the two species. We conclude that the deciduous larch conifers have specific metabolic hydrogen fractionations and that the larch unique signature of δ2H is useful to recognize it from other conifers in subfossil wood samples collected for paleoclimatic studies. For climate information the absolute δ2H values of larch should be considered carefully and separate from other species

Der nacheiszeitliche Bergsturz im Kandertal (Schweiz): Alter und Auswirkungen auf die damalige Umwelt

Zusammenfassung.: Beim Bau des neuen AlpTransit Lötschberg Basistunnels wurden unter murgangartig verschwemmten Ablagerungen der alten Bergsturzmasse des Kandertals Stillwasserablagerungen mit zahlreichen organischen Resten und Torflagen gefunden. Die 14C-datierten Resultate der Pollen, Makrorest-, Holz- und Holzkohleanalysen ermöglichten eine Rekonstruktion der lokalen bis regionalen Umweltgeschichte. Ein Gewässer, vermutlich ein kleiner See, begann beim Tellenfeld in Frutigen um 8800 kal. Jahre v. Chr. zu verlanden. In der näheren Umgebung wuchs von 8800 v. Chr. bis 8000 v. Chr. ein Föhrenwald (Pinus silvestris), der reichlich mit Hasel (Corylus avellana) und anderen wärmeliebenden Gehölzen (Ulmen, Linden, Eichen; Ulmus, Tilia, Quercus) und Birken (Betula) durchsetzt war. Diese für die Nordalpen sehr frühe Bedeutung der Hasel ist durch 14C-datierte Corylus-Nussfragmente (9310±50 14C BP, 8722-8337 v. Chr.) belegt. Nach 8500 v. Chr. drängte die Hasel die Waldföhre allmählich zurück. Auf Grund der paläoökologischen Resultate muss angenommen werden, dass die Wälder um 7600 v. Chr. durch ein katastrophales Ereignis stark gestört wurden. Als Reaktion darauf kam es zu einer starken Zunahme der Waldbrände und es breiteten sich zuerst Farne und Gräser sowie wenig später Waldföhren aus. Das Gewässer wurde um 7100 v. Chr. durch verschwemmtes Bergsturzmaterial zerstört. Der geomorphologische Befund deutet darauf hin, dass diese Ereignisse in engem Zusammenhang mit dem Hauptbergsturz im Kandertal stehen, der aussergewöhnliche Ausmasse hatte (ca. 800 Millionen m3). Die Zerstörung der lokalen ökosysteme als Folge des Bergsturzes um 7600-7100 v. Chr. fiel in ein frühes holozänes Wärme- und Sonneneinstrahlungsmaximum, in dem es, wie vorgängige Untersuchungen in den Alpen und in anderen Gebirgen belegen, zu überdurchschnittlich vielen Hanginstabilitäten ka