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The concentrations of long-lived in-situ produced cosmogenic nuclides (10Be, 21Ne, 26Al) in quartz obtained from a very recent (~200 a, based on 14C data on organic material) terrace of the Swakop River in Namibia are nearly constant throughout a 322 cm-long depth profile. These findings corroborate earlier hypotheses postulating a homogeneous distribution of these nuclides in freshly deposited river terrace sediments. An averaged nuclide concentration is a crucial and generally assumed prerequisite for the determination of numerical ages of old sediments.

The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (DREAMS) facility, we also work on enhancing the chemical quartz-enrichment methodology from bulk rock and dissolution of quartz. Repeated exposure of the bulk material to acid mixtures (HCl/H2SiF6) at room temperature for cleaning and its monitoring by optical microscopy works for most quartz-rich samples. The quartz dissolution in HF under rather mild conditions (at room temperature on a shaker-table) has the advantage to leave difficult-to-dissolve minerals (e.g., tourmaline, zircon, rutile, sillimanite, kyanite, chromite, corundum), not separated by other physical methods before, as residue. Our comparison with a high-temperature dissolution method (in a microwave) indicates an additional amount of interfering elements, such as in average about 3 mg of Ti, more than 7 mg of Al, and about 22 mu g of Be (for 50 g SiO2), is added to the sample, hence showing the superiority of our mild method. This way, we reduce problems for chemistry and AMS, but also ensure better comparability to production rates of cleaner stoichiometric quartz from calibration sites.

The nuclide 35Cl can act as a minor “neutron poison” in the stellar slow neutron capture process. Neutron activation combined with accelerator mass spectrometry (AMS) was applied to measure the (n,γ) cross section of 35Cl for neutron spectra simulating Maxwell-Boltzmann distributions of kT,∼,30,keV and 40,keV, respectively. The neutron activations were performed at the Karlsruhe Van de Graaff accelerator and at the superconducting linear accelerator of the Soreq Applied Research Accelerator Facility utilizing the 7Li(p,n)7Be reaction. AMS measurements of the irradiated samples were performed at the 3,MV Vienna Environmental Research Accelerator, the 6,MV tandem accelerator at the Dresden AMS facility, and the 14,UD tandem accelerator of the Australian National University in Canberra. Our method is independent of previous measurements. For an energy of kT,=,30,keV, we report a Maxwellian averaged cross sections of 8.33(32),mb. Using this new value in stellar isotopic abundance calculations, minor changes for the abundances of 35Cl, 36Cl and 36S are derived.

Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co-seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after earthquake-induced sediment pulses around Pokhara, Nepal's second largest city. Freshly exhumed cohorts of floodplain trees in growth position indicate rapid and pulsed sedimentation that formed a fan covering 150 km 2 in a Lesser Himalayan basin with tens of metres of debris between the 11th and 15th centuries AD. Radiocarbon dates of buried trees are consistent with those of nearby valley deposits linked to major medieval earthquakes, such that we can estimate average rates of re-incision since. We combine high-resolution digital elevation data, geodetic field surveys, aerial photos, and dated tree trunks to reconstruct geomorphic marker surfaces. The volumes of sediment relative to these surfaces require average net sediment yields of up to 4200 t km –2 yr –1 for the 650 years since the last inferred earthquake-triggered sediment pulse. The lithological composition of channel bedload differs from that of local bedrock, confirming that rivers are still mostly evacuating medieval valley fills, locally incising at rates of up to 0.2 m yr –1 . Pronounced knickpoints and epigenetic gorges at tributary junctions further illustrate the protracted fluvial response; only the distal portions of the earthquake-derived sediment wedges have been cut to near their base. Our results challenge the notion that mountain rivers recover speedily from earthquakes within years to decades. The valley fills around Pokhara show that even highly erosive Himalayan rivers may need more than several centuries to adjust to catastrophic perturbations. Our results motivate some rethinking of post-seismic hazard appraisals and infrastructural planning in active mountain regions.

Ice cores are well-established archives for paleo-environmental studies, but this requires a reliable ice core chronology. The concentration of cosmogenic radionuclides in ice cores reflects the solar activity in the past and, thus, can be used as a dating tool for ice cores. Accelerator mass spectrometry (AMS) allows the determination of nuclides in high resolution. Here, we present results of a 10Be study in an ice core from Akademii Nauk (Severnaya Zemlya, Russian Arctic). AMS analyses of more than 500 samples were carried out using the 6 MV accelerator facility of the Ion Beam Center of the Helmholtz-Zentrum Dresden-Rossendorf. For the time period 400 to 2000 CE the temporal variations of 10Be reflect the centennial variations of solar activity known from similar studies of Greenlandic ice cores and from 14C production reconstructions. The 10Be peak of 775 CE, today understood as result of the strongest known solar particle storm, was found by high-resolution core analysis. This peak is used as a tie point (additionally to volcanic reference horizons) for the development of the depth-age relationship of the Akademii Nauk ice core. Indications of the so called “Carrington Event” of 1859 CE, 20 to 30 times weaker than 775 CE, could also be detected in the core.

Temporal variations of the radionuclide 10Be are broadly synchronous across the globe and thus provide a powerful tool to synchronize ice core chronologies from different locations. We compared the 10Be record of the Akademii Nauk (AN) ice core (Russian Arctic) for the time period CE 1590–1950 to the 10Be records of two well-dated Greenland ice cores (Dye3 and NGRIP). A high correlation (r = 0.59) was found between the AN and Dye3 records whereas the correlation with NGRIP was distinctly lower (r = 0.45). Sources of deviations may include local fluctuations in the deposition of 10Be due to changes in the precipitation patterns, and artefacts due to the core-sampling strategy. In general, the existing age model was validated, confirming the AN ice core to be a unique and welldated source of palaeoclimate parameters for the Russian Arctic. We further used numerical simulations to test the influence of the core-sampling strategy on the results and derived an optimized sampling strategy for the deeper parts of the ice core.

Elevated shorelines and lake sediments surrounding Issyk Kul, the world’s second largest mountain lake, record fluctuating lake levels during Quaternary times. Together with bathymetric and geochemical data, these markers document alternating phases of lake closure and external drainage in the Late Pleistocene. The uppermost level of lake sediments requires a former blockage of the lake’s western outlet through the Boam gorge. Previous studies hypothesised that failures of Pleistocene ice or landslide dams in the gorge generated partial outburst floods of Issyk Kul. We test this hypothesis by exploring possible links between late Quaternary lake levels and outbursts. We dated stranded shorelines using 14C in shells, snails, and plant detritus, as well as sand lenses in delta and river sediments using Infrared Stimulated Luminescence. Our dates are consistent with lake levels expanding into Boam gorge between ~46 ka and 22 ka. Cosmogenic 10Be and 26Al exposure ages of fan terraces containing erratic boulders downstream of the gorge constrain the timing of possible outburst floods to 22-24 ka, postdating a highstand of Issyk Kul. A flow competence analysis gives a peak discharge of >104 m3 s–1 for entraining and transporting these boulders. Palaeoflood modelling, however, shows that naturally dammed lakes unconnected to Issyk Kul could have produced such high discharges upon sudden emptying. Hence, although our data are consistent with hypotheses of catastrophic outburst flooding, we caution against directly these to Pleistocene lake levels of Issyk Kul. Average lake-level changes of up to 90 mm yr–1 in the past 150 years were highly variable without any outburst event, so that attributing catastrophic lake-level drops to dam breaks is ambiguous using sedimentary archives alone. Nevertheless, the Pleistocene flood events that we reconstruct are among the largest reported for the Tien Shan mountains, and motivate further research into the palaeoflood hydrology in Central Asia.

Der vorliegende Band versammelt die Beiträge eines internationalen Workshops, der unter gleichem Titel im Jahr 2011 in Berlin stattfand. Er stellte die erste Initiative des kurz zuvor gegründeten „Netzwerks Archäologisch-Historisches Metallhandwerk (NAHM)“ dar und wurde im Verbund mit dem Exzellenzcluster Topoi durch geführt. Die Aufsätze widmen sich den Feinschmiede techniken metallener Objekte und behandeln aus ge wählte Fundgruppen und Fragestellungen aus der Sicht der Archäologie, der Metallkunde, den Naturwissenscha en sowie der Restaurierungspraxis. Die Erschließung eines „Verborgenen Wissens“ zielt auf die Rekonstruktion des technologischen Knowhow. Dessen Bestimmung ermöglicht weiterführende Fragen und Antworten nach der sozialen Organisation des Handwerks oder nach Werkstattkreisen. Für das umfassende Verständnis der einem Objekt zugrundeliegenden chaîne opératoire ist eine interdisziplinäre Herangehensweise unerlässlich. Dies spiegelt sich in der Vielfalt der angewandten Methoden in den elf Beiträgen wider. Die Autorinnen und Autoren spannen zudem einen weiten chronologischen Bogen von der Bronze zeit bis in die Neuzeit, der zu einer vergleichenden Betrachtung einlädt.

The Himalayas and their foreland belong to the world’s most earthquake-prone regions. With millions of people at risk from severe ground shaking and associated damages, reliable data on the spatial and temporal occurrence of past major earthquakes is urgently needed to inform seismic risk analysis. Beyond the instrumental record such information has been largely based on historical accounts and trench studies. Written records provide evidence for damages and fatalities, yet are difficult to interpret when derived from the far-field. Trench studies, in turn, offer information on rupture histories, lengths and displacements along faults but involve high chronological uncertainties and fail to record earthquakes that do not rupture the surface. Thus, additional and independent information is required for developing reliable earthquake histories. Here, we present exceptionally well-dated evidence of catastrophic valley infill in the Pokhara Valley, Nepal. Bayesian calibration of radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments yields a robust age distribution that matches the timing of nearby M>8 earthquakes in ~1100, 1255, and 1344 AD. The upstream dip of tributary valley fills and X-ray fluorescence spectrometry of their provenance rule out local sediment sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from the Annapurna Massif >60 km away. The landscape-changing consequences of past large Himalayan earthquakes have so far been elusive. Catastrophic aggradation in the wake of two historically documented medieval earthquakes and one inferred from trench studies underscores that Himalayan valley fills should be considered as potential archives of past earthquakes. Such valley fills are pervasive in the Lesser Himalaya though high erosion rates reduce preservation potential. Further studies may wish to seek such remnants of prehistoric earthquakes using extensive sedimentological work as well as numerical age control.

Der vorliegende Band versammelt die Beiträge eines internationalen Workshops, der unter gleichem Titel im Jahr 2011 in Berlin stattfand. Er stellte die erste Initiative des kurz zuvor gegründeten „Netzwerks Archäologisch-Historisches Metallhandwerk (NAHM)“ dar und wurde im Verbund mit dem Exzellenzcluster Topoi durchgeführt. Die Aufsätze widmen sich den Feinschmiedetechniken metallener Objekte und behandeln ausgewählte Fundgruppen und Fragestellungen aus der Sicht der Archäologie, der Metallkunde, den Naturwissenschaften sowie der Restaurierungspraxis. Die Erschließung eines „Verborgenen Wissens“ zielt auf die Rekonstruktion des technologischen Knowhow. Dessen Bestimmung ermöglicht weiterführende Fragen und Antworten nach der sozialen Organisation des Handwerks oder nach Werkstattkreisen. Für das umfassende Verständnis der einem Objekt zugrundeliegenden chaîne opératoire ist eine interdisziplinäre Herangehensweise unerlässlich. Dies spiegelt sich in der Vielfalt der angewandten Methoden in den elf Beiträgen wider. Die Autorinnen und Autoren spannen zudem einen weiten chronologischen Bogen von der Bronzezeit bis in die Neuzeit, der zu einer vergleichenden Betrachtung einlädt.