Erosion rates and sediment budgets in vineyards at 1-m resolution based on stock unearthing (Burgundy, France)

A new and simple method is developed to efficiently quantify erosion and deposition rates based on stock unearthing measurements. This is applicable to spatial scales ranging from plot to hillslopes, and to time scales ranging from single hydrologic events to centennial scales. The method is applied to a plot area on vineyard hillslopes in Burgundy (Monthélie, France), with measurement of 4328 vine plants. A sediment budget established at the plot scale shows a mean soil lowering of 3.44 ± 1 cm over 20 years, involving a minimal erosion rate of 1.7 ± 0.5 mm yr^− 1. Locally, erosion rates can reach up to 8.2 ± 0.5 mm yr^− 1.This approach allows the sediment redistribution to be mapped and analyzed at 1-m resolution. It provides novel insights into the characterization of erosion patterns on pluri-decennial scales and into the analysis of spatial distribution of erosion processes on cultivated hillslopes.     

Insights into the formation of rock varnish in prevailing dusty regions

The characteristics of rock varnish from the Campo de Piedra Pomez (CPP, Andes Argentina) provides new insights into the development of rock varnish under severe dusty conditions. The CPP varnish has been analysed using SEM‐EDAX and Raman techniques. The rock coating is tens of microns in thickness and under the microscope shows a micro to cryptocrystalline appearance and a general granular texture. Silica (quartz, cristobalite and amorphous silica) is the main phase forming these coverings followed by Al, K and Na compounds. Minor Fe oxides and Mn oxides are the source for the orange (Fe) and brown (Fe and Mn) hues of the coating. The results obtained for the CPP coating show that desert varnish developed under dusty circumstances does not have the appearance of typical rock varnish. Textural characteristics include high crystallinity and granular arrangement of the components. Moreover the absence of typical microlaminations is related to the presence of aeolian mineral grains which inhibit their development. The main mechanism of formation of rock varnish under such environmental circumstances is the direct incorporation of aeolian mineral grains into the varnish. However, other physicochemical processes are also required to explain the formation of varnish components such as amorphous silica or iron oxides phases. Although the development of the desert varnish may act as a protector of the underlying pyroclastic rock, the extreme and persistent windy conditions in the CPP field are high enough to weather and erode not only the rock coating but also the original ignimbrite. As other warm desert sites on Earth, the CPP area can also be considered as possible terrestrial analogue to Mars. Some environmental attributes might be similar to those expected on the Martian surface and thus, textural similarities between the CPP varnish and the rock varnish‐like coating of Mars are likely. Copyright © 2014 John Wiley & Sons, Ltd.     

Responsible fisheries: An overview of FAO policy developments (1945–1994)

The paper outlines the evolution of fisheries development policies (aquaculture excluded), from an international perspective as seen within the various UN and FAO fishery committees. It begins with the first FAO Technical Committee on Fisheries in 1945 and extends through the various periods corresponding to post-war reconstruction (1945–1958), geographical expansion (1959–1972), establishment of a new economic order of the oceans (1973–1982), and transition towards global concerns (1983–1992). It underlines the gaps between government resolutions at the international level and effective implementation at national policy level. This identifies the elements to be considered in responsible fishing policies. Finally, the FAO International Code of Conduct for Responsible fisheries is presented as the conceptual framework for achieving sustainable fisheries development and UNCED's objectives within the framework of the 1992 Convention.     

Stable isotopes and trace elements in modern ostracod shells: implications for reconstructing past environments on the Tibetan Plateau,China

Stable isotopes and trace elements in ostracod shells have been used widely in paleolimnological investigations of past lake hydrochemistry and climate because they provide insights into past water balance and solute evolution of lakes. Regional differences in lake characteristics and species-specific element fractionation, however, do not permit generalization of results from other regions or ostracod species to the southern Tibetan Plateau, in part because most common taxa from the southern Tibetan Plateau are endemic to the area. This study evaluated relations between present-day environmental conditions and the geochemical composition of modern ostracod shells from the southern Tibetan Plateau, to assess the suitability of using shell chemistry to infer hydrological conditions. We studied nine lakes and their catchments, located along a west–east transect in the south-central part of the Tibetan Plateau. Stable oxygen and carbon isotope values and trace element concentrations in recent shells from the four most abundant ostracod species (Leucocytherella sinensis, ?Leucocythere dorsotuberosa, Limnocythere inopinata, Tonnacypris gyirongensis) were measured, together with hydrochemical properties of host waters at the time of sampling. Results revealed significant between-species differences in stable isotope fractionation and trace element incorporation into shell calcite. Stable oxygen and carbon isotope values of ostracod shells were correlated significantly with the stable isotope composition of the respective water body \( \left( {\updelta^{18} {\text{O}}_{{{\text{H}}_{ 2} {\text{O}}}} \,{\text{and }}\updelta^{13} {\text{C}}_{{{\text{H}}_{ 2} {\text{O}}}} } \right) \), reflecting salinity and productivity, respectively. Offsets between δ¹⁸O_shell and δ¹³C_shell and inorganic calcite, the latter representing isotopic equilibrium, suggest shell formation of T. gyirongensis during spring melt. L. sinensis reproduces throughout the monsoon season until September and shows several consecutive generations, and L. inopinata molts to the adult stage after the monsoon season in August/September. The influence of pore water δ¹³C was displayed by L. inopinata, suggesting shell calcification within the sediment. Mg/Ca_shell is primarily influenced by water Mg/Ca ratios and salinity and confirms the use of this shell ratio as a proxy for precipitation-evaporation balance and lake level. In addition, Sr/Ca and Ba/Ca can be used to infer changes in salinity, at least in closed-basin lakes with calcite saturation. Observed effects of water Sr/Ca and salinity on Sr/Ca incorporation are biased by the presence of aragonite precipitation in the lakes, which removes bioavailable Sr from the host water, resulting in low Sr/Ca_shell values. Changes in carbonate mineralogy affect the bioavailability of trace elements, a process that should be considered in paleoclimate reconstructions. Oxygen isotopes and Mg/Ca_shell ratios were unaffected by water temperature. Positive correlations among Fe/Ca, Mn/Ca and U/Ca in ostracod shells, and their negative correlation with δ¹³C, which reflects organic matter decay, show the potential to infer changes in redox conditions that can be used to reconstruct past oxygen supply to bottom waters and thus past water-circulation changes within lakes. The intensity of microbial activity, associated with organic matter decomposition, can be inferred from U/Ca ratios in ostracod shells. These findings highlight the value of fossil ostracod records in lake deposits for inferring paleoenvironmental conditions on the southern Tibetan Plateau.     

Counteracting urban climate change: adaptation measures and their effect on thermal comfort

Cities represent thermal load areas compared with their surrounding environments. Due to climate change, summer heat events will increase. Therefore, mitigation and adaptation are needed. In this study, meteorological measurements in various local climate zones were performed to demonstrate the influence of evaporation surfaces and other factors on thermal comfort, as determined by the physiologically equivalent temperature (PET). Furthermore, a quantification of the thermal effects of several adaptation measures and varying meteorological parameters was made using model simulations (ENVI-met) in an inner-city neighborhood (Oberhausen, Germany). The results show that the most effective adaptation measure was increased wind speed (maximal 15 K PET reduction). Moreover, vegetation areas show greater PET reductions by the combination of shading and evapotranspiration than water surfaces. The creation of park areas with sufficient water supply and tall, isolated, shade-providing trees that allow for adequate ventilation can be recommended for planning.     

Chemical Procedures for Rhenium Extraction from Geological Samples: Optimising the Anion Resin Bead Clean‐up Step

Rhenium–osmium geochronometry for samples with low Re and complex matrices requires improved Re extraction methods. Here, we investigate plausible controls on efficiency and efficacy of Re extraction during our anion resin bead purification. Four different protocols are compared, each isolating a single variable to test. Rhenium concentrations for solutions at each step of each protocol document differences in chemical recovery/yield. The negative‐thermal ionisation mass spectrometry (N‐TIMS) signal intensity serves as a proxy for Re yield and purity. These data document correlations between the N‐TIMS signal intensity and (a) the duration of anion resin bead conditioning prior to loading with Re‐bearing solution, and (b) both duration and strength of nitric acid used during rinsing of the Re‐loaded anion resin bead. The optimal protocol improved Re signal intensity around fourteen times compared with our current Re extraction protocol, an aggregate of 2.4 times improvement in chemical recovery (yield) and 5.8 times improvement in emission efficiency (purity). Repeated N‐TIMS isotopic measurements on our in‐house Re standard solution (1407) verify that our optimal protocol‐3 does not fractionate Re isotopes. The improved anion resin bead method considerably lowers the Re detection limit and allows Re‐Os isotopic analysis of picogram‐level Re hosted in geological samples with complex matrices.     

Syntectonic subaqueous mass flows of the Neoproterozoic Otavi Group,Namibia: where is the evidence of global glaciation?

The thick (>1 km) Neoproterozoic Otavi Group of Namibia accumulated after ca. 760 Ma along >700 km of the faulted margin of the Congo Craton. The margin shows a north to south, downbasin transition from a shallow‐water carbonate shelf (Otavi Platform) to offshore deepwater slope (Outjo Basin). Within the latter, the Abenab and Tsumeb Subgroups contain large volumes of poorly sorted breccias, conglomerates and diamictites composed principally of locally derived carbonate. Diamictite facies were reported in the 1930s as tillites left by an ice sheet (although the absence of striated clasts and other key glacial indicators was viewed as problematic). Later workers rejected a glacial origin concluding that Outjo basin facies were deposited as parts of prograding submarine wedges built by mass flows during active rifting. Recently, the Snowball Earth hypothesis has returned to the earlier glacial interpretation; arguing that these strata represent a record of extraordinary late Neoproterozoic glacial and interglacial climates when global temperatures fluctuated by up to 100°C. Facies analysis of breccias, diamictites, conglomerates and sandstone strata of the Otavi Group identifies them as genetically related, subaqueously deposited sediment gravity flows. They lack diagnostic indicators of any one specific climate in source areas. These facies were all deposited in deepwater at the foot of landslide‐prone scarp blocks where debris flows and turbidity currents moved large volumes of coarse, freshly broken carbonate debris produced by faulting. Breccias, diamictites, conglomerates and sandstones occur in composite fining‐ and thinning‐upward bundles that are directly analogous to those reported from many other faulted margins in the Phanerozoic stratigraphic record. These rocks provide no clear sedimentological signature of a glacial source or catastrophic Snowball Earth‐type temperature fluctuations. Instead, they point to a dominant tectonic control on sedimentation related to faulting along the margin of the Congo Craton.