Das Projekt "Rock boulders as indicators of soil erosion (RAISE)" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. Landscape and soil changes are strongly coupled to chemical and physical (erosion) weathering and soil production. The erosion rate is preserved in the signal of cosmogenic nuclides (e.g., 10Be) in stream sediments or even directly in a soil profile. The genesis of clastic sediments and soils has been investigated to quantify processes occurring within source areas and catchments, including chemical and physical weathering, and textural and compositional modification of detritus during transition from bedrock to grus and thereafter to soil or a fluvial environment. Well-defined (or -controlled) settings are however needed to calculate mass balances for a given (tectonically active) catchment. Measurements of mid- to long-term erosion rates have recently become more widely available through cosmogenic nuclide techniques. Still, new approaches can be developed to improve our understanding of weathering processes and their rates. Ideal settings and a considerable dataset about mineral weathering are given for the Sila massif in southern Italy (and consequently in a Mediterranean environment). It represents a tectonically active area. The upland plateaus consist of old planation surfaces, bordered by steep slopes, and are characterised by granitic spheroidal boulders which form wide boulder fields. The combination of the major tectonic and relief features with typical upland Mediterranean climate conditions promoted the triggering of severe erosion, that led to the exhumation of the boulders. Data about soil erosion amounts and rates related to the soil formation period would complete the puzzle of the driving forces and enable a more detailed interpretation of landscape and soil evolution. These boulders seemed to 'grow' out of the surface with time. Consequently, by measuring the 10Be content at different levels along a rock boulder (from the soil surface to the top of boulders), the age(s) of exposure could be derived and subsequent total denudation rates will be obtained. This would be an elegant way to calculate erosion rates for different time-steps that cover almost the entire period of soil evolution. Such an approach would give insight into a) the overall denudation and erosion rates over the whole (potential) soil formation period and b) erosion and denudation rates during time segments and would allow for the distinction of different erosion phases during the Pleistocene and Holocene c) volumes of loose material that were removed from the uplands and entered the drainage river system in this time span. (...)
Das Projekt "Influence of permafrost on chemical and physical weathering" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. With increasing temperatures, permafrost is continuously thawing. This will lead in future to different thermal and hydrological conditions in the soil and regolith in cold regions. Therefore, climate change is assumed to cause a marked change in weathering conditions in high Alpine areas. Long-term chemical weathering and physical erosion rates are interrelated processes. In order to better understand landscape response to climate change, it is important to quantify both processes. The planned investigations generally aim at the estimate of element denudation/weathering rates and short- and long-term erosion of high Swiss Alpine soils (Upper Engadine: Albula and Val Bever). Both types of sites will be considered: a) with and b) without permafrost. The main objectives include 1) the evaluation of chemical weathering mechanisms using tracers such as immobile elements and Sr-isotopes 2) the determination of soil erosion rates (long-term) using two different techniques: a) in situ produced cosmogenic 10Be in soil sections and b) the inventory of meteoric 10Be in soils. Short-term erosion rates will be estimated using 137Cs as tracer. 3) determination of organic matter stocks in soil and characterisation and 14C dating of labile and stable (resistant to a H2O2 treatment) organic matter fractions. 4) Mapping of present day permafrost distribution and monitoring of near-surface and ground surface temperatures is essential for the understanding and prediction of the weathering behaviour of high Alpine regions. An important and innovative aspect is that chemical weathering and particularly erosion rates will be characterised using a multi-method approach. A cross-check of all the methods used will allow an extended interpretation and mutual control of the results. Furthermore, novel or very recently developed methods (erosion rates determined by meteoric 10Be using a non-steady-state approach; spatial on-site detection and characterisation of permafrost using a highly novel 3-D geophysical approach, 14C dating of stable (H2O2-resistant) soil organic matter, etc.) will be applied for the first time in high Alpine regions. The expected new insights will lead to a better understanding of the processes of high mountain soils and are a further step towards improving climate-related modelling of fast warming scenarios and increasing system disequilibria.
Das Projekt "Soil and Alpine landscape evolution since the Lateglacial and early/mid Holocene in Val di Sole (Trentino, Italy)" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. Fast climate changes have occurred in the Lateglacial and early Holocene period. The investigation of this time span therefore gives precise insight into the sensitivity of Alpine areas regarding fast changing environmental conditions. The investigation generally focuses at dating selected Alpine sites of distinct landform surfaces with several absolute and relative methods with the aim to establish an absolute chronology of surfaces, to correlate several dating methods and to improve every ones. The investigation area is in Trentino (Northern Italy). Special emphasis is given to the Lateglacial and early Holocene period. We use several methods (absolute and relative techniques) for dating. A main focus is addressed to moraines and surfaces using soils as an indicator of landscape history. Moraines will be suitable sites for soil investigations where soil chemical and mineralogical techniques can be compared to the absolute age dating techniques. Special aims of the work will be: - 10Be in soil as an age indicator (developing method on Trentino soils and in other sites (e.g. Swiss Alps)) - Dating with 14C and charcoal analyses - Deciphering landscape history in small catchments in Val di Sole using relative and absolute dating techniques. A cross-check of exposure dating, radiocarbon ages and relative methods will allow an extended interpretation, mutual control of the applied methods and a more accurate estimate of possible error sources. A so-calibrated methodology may later also be applied on other characteristic cold-mountain deposits such as debris flows or rock-fall deposits. The whole set of newly developed dating methodologies opens most interesting perspectives for chronological work about late-glacial and Holocene landscape evolution in climate-sensitive high-mountain areas.
Das Projekt "Das Quartaer-Klimaprotokoll in Loesssedimenten: Nachweis mittels magnetischer und geochemikalischer Analysen von Gestein und Mineralen" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Geophysik durchgeführt. Leading Questions: - Which physical and chemical processes control the formation of the loess rock magnetic and isotope signature? - How are isotope influx and magnetic input into the loess sediments correlated? - How can palaeoclimatic conditions, especially palaeorainfall be reconstructed from the loess magnetic susceptibility and the 10Be record? Abstract: Loess is a wind-blown Quaternary silt deposit which blankets vast tracts of land and in places reaches thickness in excess of 300m. Over the last decade it has emerged that certain loess sections have recorded the polarity history of the geomagnetic field and now provide essentially continuous magnetostratigraphic archives covering the last 2-3 Ma. Indeed, it is the chronology provided by the magnetic polarity signature itself which was largely responsible for establishing the timing of the initiation of loess accumulation, particularly in the celebrated Chinese Loess Plateau where a starting date close to the Gauss/Matuyama chron boundary (2.6 Ma) is now firmly established. This coincides with a widely documented global climatic shift and accelerated uplift of the Tibetan Plateau. Many loess sections contain fossil soil (paleosols) which bear witness to warmer and wetter climatic conditions corresponding to interglacial periods in contrast to the cold, arid environments in which pristine loess accumulated and which correspond to glacial intervals. The resulting sequences of alternating loess and paleosols also manifest themselves magnetically, in this case in terms of susceptibility changes, entirely distinct from the remanence characteristics which encode the geomagnetic polarity. The susceptibility time series obtained from localities in Alaska and China correlate remarkably well with the oceanic oxygen isotope signal, and yield spectral power estimates in agreement with those predicted by the astronomical (Milankovitch) theory of ice ages. Comparison of susceptibility patterns with corresponding profiles of 10Be concentration in loess allows major changes in rainfall to be estimated. In China, for example, data spanning the last 130ka (corresponding to oxygen isotope stages 1-5) indicate that paleoprecipitation was almost halved (from 540 mm/a to 310mm/a) as the warm interglacial during which paleosol S1 formed gave way to the following glacial interval in which loess layer L1 accumulated. It has also been found that increased amounts of continent-derived dust delivered to the deep ocean correlates with loess formation and thereby permits certain broad features of atmospheric circulation (paleowinds) to be worked out. Debate continues over the actual mechanism by which magnetic susceptibility becomes a climate proxy. The current consensus is that some form of in situ process must be responsible, at least in part.
Das Projekt "Kosmogene Radionuklide in polarem Eis" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz, Abteilung für Umweltphysik durchgeführt. Messung kosmogener Radionuklide (10Be, 36Cl, 26Al) im GRIP Eiskern. Interpretation der Resultate mit Schwergewicht auf: Herleitung von Paleo-Niederschlagsraten, Rekonstruktion der Sonnenaktivitaet und des Geomagnetfeldes, Untersuchung des Zusammenhangs zwischen Sonnenaktivitaet und Luminositaet, Vergleich mit den 14C-Daten von Baumringen. Trennung von Produktions- und Systemeffekten.