Deglaciation and landscape history around Annapurna,Nepal, based on 10Be surface exposure dating

The High Himalaya is a key area for tectonic, geomorphological and climate studies, because of its extreme relief and location at the transition zone between areas with abundant monsoonal precipitation and the arid/semiarid Tibetan Plateau. We present ¹⁰Be surface exposure ages on 22 boulders from the Annapurna area in Nepal. The ages improve understanding of the Late Quaternary landscape history and the geomorphological processes operating in this part of the Himalaya.Although our study is reconnaissance in nature, it highlights the importance of catastrophic events, such as landslides and debris flows, for denudation of high mountains. Holocene exposure ages for the Dhampu–Chooya landslide (～4.1 ± 0.6 ka) and for 600 m of alluviation in Kali Gandaki Valley (～2.1 ± 0.6 ka), for example, indicate the frequent occurrence and extent of catastrophic events and their implications for natural hazards. We also offer an explanation for the differences in Late Quaternary glacial chronologies at closely spaced study sites in the Nepal Himalaya. Topographically controlled and spatially variable precipitation in the Himalaya determines the sensitivity of glaciers to changes in temperature and precipitation. Accordingly, some glaciers advanced in-phase with Northern Hemisphere ice sheets, whereas others reached their maximum extent at times of increased monsoonal precipitation during Marine Isotope Stage 3 and the early Holocene.     

A siliceous chrysophycean cyst-based pH transfer function for Central European lakes

The surface sediments of 50 Central European low to high mountain, acid-sensitive lakes were examined for chrysophycean stomatocysts. One hundred and twenty sic siliceous stomatocyst morphotypes were differentiated by using scanning electron microscope (SEM), counted and illustrated (light microscopy and SEM). Canonical Correspondence Analysis (CCA) showed that pH is the most important measured variable in explaining the cyst distributions, with a strong correlation to the first axis (r²=-0.78). Simple Weighted Averaging (WA) regression and calibration was performed to generate a transfer function for lake water pH. Finally, the transfer function was evaluated by reconstructing pH for a short annually laminated and ¹³⁷Cs dated core from Lake Plené, a strongly acid lake, in the Bohemian Forest. A comparison of the measured and inferred pH values indicates that the model has good predictive power. The cyst-inferred pH and the diatom-inferred pH both indicate that pH was low during the 1970s and that the lake has experienced recovery in recent years.     

Climatic Changes from 12,000 to 4,000 Years Ago in the Austrian Central Alps Tracked by Sedimentological and Biological Proxies of a Lake Sediment Core

Major and trace elements, minerals, and grain-size were analysed from the early to mid-Holocene (12 to 4 ky BP) period of a sediment core from the Alpine lake Oberer Landschitzsee (ObLAN, 2076 m a.s.l.), which is located on predominantly crystalline bedrock on the southern slopes of the Austrian Central Alps. Geochemistry and mineralogy were compared with diatom-inferred (Di-) ‘date of autumn mixing’ (A_mix), DOC, pH, and selected indicator pollen species from the same sediment core. Principal components analysis (PCA) indicated a positive correlation between processes triggered by temperature and precipitation (e.g., lake mixing, DOC). PCA grouped indicators of physical weathering and enhanced catchment run-off (sand, quartz, feldspar), elements of weathering (e.g., Ti, Rb, Mn) under dryer conditions (clay to silt fractions), and elements that probably were related to changes in redox conditions (Cu, Fe, S, Zn). The duration and height of the snow-pack played an important role in this high-alpine environment, affecting weathering, erosion, pH, and lake stratification. Low Alnus viridis pollen abundance, together with markers for increased elements of erosion, indicated extensive snow-pack. Changes in S coupled with As, and elements indicating increased weathering, reflected climate oscillations. LOI was affected by productivity and erosion. High (late) Di–A_mix coupled with increased Di-DOC indicated prolonged summers with increased productivity. Cold and wet (snow-rich) phases and subsequent melting caused low pH and a decoupling of the significant linear correlation between sedimentary Ca and Di-pH. Weathering and leaching during climate deteriorations opposed the long-term trend in a loss of cations and forced in-lake alkalinity generation during the following lake warming. Overall, the multi-proxy study indicated complex climate-driven processes within different time-scales (long-term trends, climate oscillations, seasonality). The climate oscillations within 12–5 ky BP corresponded well with the cool and wet phases known from central Europe suggesting a dominant common Atlantic climate impact. When Mediterranean climate established between 5 and 4 ky BP, its influence on the southern slopes of the Alps increased.     

Restriction on the motion of a solid in a gravitational field

As is well known, the orbital and rotational motions of a solid are coupled, and the integrals of energy and angular momentum (in a gravitational field with spherical symmetry) impose restrictions on them. We study the regions allowed to the motion in configurational space. It turns out that even in the crudest model (planar motion of a triple rod) the restrictions on the libration angle and the orbital radius of the center of mass are coupled, so that excessive ellipticity of the orbit excludes stabilization in the neighbourhood of the spoke equilibrium position by gravitational forces only.Chargé de Cours.     

InterPreting effects of TOCinert organic content on source rock Potential using S2 vs. TOC graPh in Maamba Coalfield,southern Zambia

The authors Present the effects of the total organic carbon( TOCinert )during Pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI)using the cross Plot S2 vs. TOC graPh. A to...     

Imaging diffuse emission with COMPTEL

The imaging telescope COMPTEL aboard the NASA Compton Observatory satellite has been demonstrated to be capable of imaging diffuse emission along the Galactic plane. Here we describe details of the imaging data spaces and methods to model the background. Different methods of imaging analysis are compared. Verification of consistency among these methods is a key factor in overall assessment of diffuse emission results. Source simulations and statistical analysis through the bootstrap method are applied to verify the significances of image structures.     

Subduction of the Daiichi Kashima Seamount in the Japan Trench

In 1984–1985, the Kaiko consortium collected Seabeam, single-channel seismic and submersible sampling data in the vicinity of the Daiichi-Kashima seamount and the southern Japan trench. We performed a prestack migration of a Shell multichannel seismic profile, that crosses this area, and examined it in the light of this unusually diverse Kaiko dataset. Unlike the frontal structure of the northern Japan trench, where mass-wasting appears to be the dominant tectonic process, the margin in front of the Daiichi-Kashima shows indentation, imbrication, uplift and erosion. Emplacement of the front one-third of the seamount beneath the margin front occurs without accretion. We conclude that the Daiichi-Kashima seamount exemplifies an intermediate stage between the initial collision and subduction of a seamount at a continental margin.     

Dispersant Use and a Bioremediation Strategy as Alternate Means of Reducing Impacts of Large Oil Spills on Mangroves: The Gladstone Field Trials

Over a three-year period (1995–1998), we studied short-term effects of dispersant use and a bioremediation strategy in two consecutive field trials in sub-tropical Australian mangroves. In each case, weathered oil was applied, and a large spill simulated, in mature Rhizophora stylosa trees around 4–9 m tall. In the first trial, we used Gippsland light crude oil with or without dispersant, Corexit 9527. In the second, a bioremediation strategy followed application of Gippsland oil or Bunker C fuel oil. Bioremediation involved forced aeration with supplemental application of nutrients. Dispersant use had an overall positive benefit shown as reduced tree mortality. By contrast, there was no apparent reduction in mortality of trees with bioremediation. However, one year after oiling, leaf densities of surviving trees were greater in bioremediation plots than in controls, and less in oil-only plots. These and other results have been incorporated into spill response management strategies in Australia.     

Towards an integration of process measurements, archive analysis and modelling in geomorphology — the Kärkevagge experimental site, Abisko area, northern Sweden

The analysis of Holocene geomorphic process activity demands long–term data sets, which are available for the Kärkevagge catchment due to 50 years of intensive geomorphologic field studies. This data set is used in combination with additional field measurements, remote sensing and digital elevation model (DEM) analysis to provide input data for modelling Holocene valley development. On the basis of this information, geomorphic process units (GPUs) are defined by means of GIS modelling. These units represent areas of homogeneous process composition that transfer sediments. Since the data base enables the quantification of single processes, the interaction of processes within the units can also be quantified. Applying this concept permits calculation of recent sediment transfer rates and hence leads to a better understanding of actual geomorphic landscape development activity. To extrapolate these data in time and space the process–related sediments in the valley are analysed for depth and total volume, primarily using geophysical methods. In this fashion the validity of measured process rates is evaluated for the Holocene time scale. Results from this analysis are exemplified in a cross–profile showing some of the principal sediment units in the valley. For example, the measured modern rates on a slush torrent debris fan seem to represent the Holocene mean rate. This approach should also be suitable for revealing Holocene geomorphic landscape development in terms of climate change.