Mass movements in cave sediments: investigation of a ∼40,000-year-old guano mudflow inside the entrance of the Great Cave of Niah, Sarawak, Borneo

The West Mouth of the Great Cave at Niah in Sarawak, northwest Borneo and the North Passage that leads to the West Mouth contain large deposits of guano. The main deposit, several metres thick in places, forms the sloping floor of the entire North Passage. A mass movement deposit identified in the West Mouth, having a volume of 600 m³, originated as a guano mudflow up the North Passage in the order of 40,000 years ago. This failure of the guano slope was investigated to determine whether particular conditions or events could be identified as the most likely causes. The physical, hydrological and geotechnical properties of samples of the material were determined so that the stability of the slope could be assessed. Stability analyses showed that shearing failure of the slope would require inputs of water to the slope in quantities for which no feasible explanation can be suggested. However, the properties of the guano are similar to those of loess, indicating a high susceptibility to ‘hydrocollapse’. Very shallow failure of the slope, possibly as several smaller mudflows, could therefore have occurred due to additional water in quantities that could realistically be supplied as rainwater spray, possibly with a seismic trigger. The climate must therefore have been wetter than it is at present. These findings have implications for the interpretation of sediment deposits in other relict caves.     

New insights into rare earth element (REE) particulate generated by cigarette lighters: an electron microscopy and materials science investigation of a poorly understood indoor air pollutant and constraints for urban geochemistry

Cigarette smoking is a well-recognized cause of lung cancer and other diseases and is a major contributor to indoor air pollution in numerous settings worldwide. Most cigarette lighters use rare earth element (REE) mischmetal in their flints in order to aid ignition, and these lighters thus have pyrophoric properties. REE particulate emitted from these lighters presents a complexity in the role of health of smokers that has yet to be explored fully. Furthermore, these particles are likely present in numerous urban settings and contribute to the complexities of urban geochemistry. Details of the material properties of rare earth element (REE) particulate derived from smoking lighters are determined first the first time. Particulate was investigated using back-scatter detection scanning electron microscopy techniques and transmission electron microscopy techniques. Several particle types were observed and demonstrate a diverse range of size and textures, many of which are previously not documented and are much smaller than previous basic scanning electron microscopy investigations. These include irregularly shaped fragments of mischmetal, micrometer-scale spherules, aggregates of nanospherules, and platy sponge-like nanoparticles. All of these particles have significant REE content, and most are of a particle size that can be deposited deep in the lung. The available literature regarding toxicity of REEs and the material science data presented here argues very strongly for cause for concern.     

A strontium,neodymium and oxygen isotope study of hydrothermal metamorphism and crustal anatexis in the Trois Seigneurs Massif,Pyrenees, France

Nd, Sr, and O isotope analyses have been made on metamorphic and igneous rocks and minerals from a 310–340 Ma Hercynian-age metamorphic terrane in the Pyrenees, France. Lower Paleozoic shales and phyllites have ⁸⁷Sr/⁸⁶Sr values of 0.707–0.717 at 310 Ma, but model values at 310 Ma of 0.709–0.736 (based on assumed depositional age of 450 Ma and an initial ⁸⁷Sr/⁸⁶Sr=0.707). On a regional scale, ⁸⁷Sr/⁸⁶Sr was homogenized to about 0.713 to 0.717 in the higher-grade pelitic schists during metamorphism. Much of this ⁸⁷Sr/⁸⁶Sr exchange occurred at very low grades (below the biotite isograd), but significant changes also accompanied the δ ¹⁸O lowering of the phyllites (+13 to +16) during their transformation to andalusite- and sillimanite-grade schists (δ ¹⁸O=+11 to +12); all of these effects are attributed to pervasive interactions with hydrothermal fluids (Wickham and Taylor 1985). The data also show that a syn-metamorphic plutonic complex, dominated by a biotite granite body, was derived by mixing of a relatively mafic magmatic end-member (⁸⁷Sr/⁸⁶Sr～ 0.7025–0.7050 and δ ¹⁸O～ +7.5 to +8.0) with two metasedimentary sources, both having ⁸⁷Sr/⁸⁶Sr～0.715 and δ ¹⁸O～ +10.0 to +12.0, but with one being more homogeneous than the other. The more homogeneous component and the (mantle-derived?) magmatic end-member dominate at low structural levels within the complex. The less homogeneous end-member that dominates at high levels is clearly derived from the local Paleozoic pelitic schists. A Rb-Sr age of 330±20 Ma was obtained on hornblende from a deep level within the complex, which fixes this age for the regional metamorphism, as well. Although a post-metamorphic granodiorite magma body at Trois Seigneurs also displays heterogeneities in δ ¹⁸O and ⁸⁷Sr/⁸⁶Sr (and thus does not give a clear-cut Rb-Sr isochron), the data are consistent with an emplacement age between 260 and 310 Ma, similar to ages of other late granodiorites in the Pyrenees. ¹⁴³Nd/ ¹⁴⁴Nd is very uniform within the Hercynian crust, both at Trois Seigneurs (? _Nd=?3 to ?7) and elsewhere in the Pyrenees; almost all igneous lithologies have depleted-mantle, mid-Proterozoic model ages, consistent with efficient recycling of crustal material following original crustal accretion in this area at about 1600 Ma or earlier. Rb-Sr mineral ages exhibit a complex cooling history reflecting late Hercynian and Mesozoic thermal events. Our results show that profound homogenization of the ⁸⁷Sr/⁸⁶Sr and ¹⁸O/¹⁶O ratios of large volumes of the crust can occur during regional metamorphism and crustal anatexis, particularly in regions undergoing extensional tectonics. Such processes can significantly modify the isotopic compositions of the protoliths of granitic magmas; this may explain why many peraluminous Hercynian granitoids of Western Europe have anomalously low (⁸⁷Sr/⁸⁶Sr) initial values compared to their probable sedimentary parent rocks.     

An Attempt to Partition Stomatal and Non-stomatal Ozone Deposition Parts on a Short Grassland

To evaluate the damaging effect of tropospheric ozone on vegetation, it is important to evaluate the stomatal uptake of ozone. Although the stomatal flux is a dominant pathway of ozone deposition onto vegetated surfaces, non-stomatal uptake mechanisms such as soil and cuticular deposition also play a vital role, especially when the leaf area index \({LAI}< 4\). In this study, we partitioned the canopy conductance into stomatal and non-stomatal components. To calculate the stomatal conductance of water vapour for sparse vegetation, we firstly partitioned the latent heat flux into effects of transpiration and evaporation using the Shuttleworth–Wallace (SW) model. We then derived the stomatal conductance of ozone using the Penman–Monteith (PM) theory based on the similarity to water vapour conductance. The non-stomatal conductance was calculated by subtracting the stomatal conductance from the canopy conductance derived from directly-measured fluxes. Our results show that for short vegetation (LAI \(=\) 0.25) dry deposition of ozone was dominated by the non-stomatal flux, which exceeded the stomatal flux even during the daytime. At night the stomatal uptake of ozone was found to be negligibly small. In the case of vegetation with \({LAI}\approx 1\), the daytime stomatal and non-stomatal fluxes were of the same order of magnitude. These results emphasize that non-stomatal processes must be considered even in the case of well-developed vegetation where cuticular uptake is comparable in magnitude with stomatal uptake, and especially in the case of vegetated surfaces with \({LAI}< 4\) where soil uptake also has a role in ozone deposition.     

Climate change and infectious diseases: Can we meet the needs for better prediction?

The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed.     

Geologie an den höheren Schulen Sachsens

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