Multiproxy approach to understanding the origin of Cretaceous pelagic limestone–marl alternations (DSDP site 391, Blake-Bahama Basin)

Limestone–marl alternations are usually directly interpreted to reflect cyclic palaeoenvironmental signals. However, uncertainty in such interpretations stems from the differential diagenesis that most limestone–marl alternations have undergone. Differential diagenesis results in markedly different alterations between limestones and marls and in the loss of comparability of many measurable parameters. For an unequivocal interpretation of the origin of rhythmic alternations, diagenetically robust parameters or parameters that clearly indicate the degree of diagenetic bias are required. The present study uses a multiproxy approach (independent biotic, sedimentary and geochemical parameters) in order to unravel the palaeoenvironmental signal recorded in Valanginian (Early Cretaceous) limestone–marl alternations from the Blake‐Bahama Basin (DSDP site 391). Using this approach, terrestrial and marine influences can be distinguished, changes in nutrient levels estimated and prediagenetic differences in the non‐carbonate fraction constrained. Surprisingly, no systematic variations in any of these parameters were observed between limestone and marl layers, implying that none of these was directly responsible for the formation of the rhythmic alternation. Hence, none of the current models of sedimentary formation of limestone–marl rhythmites is applicable here. Calcareous nannofossils are equally well preserved in limestone and marl layers, ruling out their dissolution in marl layers as a source of the calcite cement in the limestone beds. Sr values of 700–900 p.p.m. indicate that aragonite may have been present in the original, pelagic sediment. The assumption of fine‐grained sedimentary aragonite imported from nearby carbonate platforms as the source of the cement would explain a number of otherwise enigmatic features in these rhythmites, including the source of the calcite cement observed in the limestones, the equally good preservation of calcareous nannofossils in limestones and marls and the higher concentration of calcareous nannofossils in marl layers. The study demonstrates that examination of diagenetically inert parameters or parameters in which diagenetic effects can be filtered can yield unexpected results. Clearly, careful analysis of such parameters needs to be undertaken in order to make reliable palaeoenvironmental interpretations from rhythmite successions.     

Quantitative high resolution cathodoluminescence spectroscopy of diagenetic and hydrothermal dolomites

A combination of high resolution cathodoluminescence-spectroscopy (HRS-CL=high resolution spectroscopy of cathodoluminescence emission) with spatial resolving trace element analyses (PIXE=proton induced X-ray emission) is used to establish a method for the quantitative determination of the Mn-content of diagenetic and hydrothermal dolomites using the measurements of peak areas of Mn-activated CL emission bands. This method takes into account the overlap of the CL broad bands of Mn²⁺ in the Mg- and the Ca-lattice-position of dolomite. There is a linear correlation between the peak areas and Mn concentration up to approx. 1000–1500 ppm. Thus, CL spectroscopy allows a determination of Mn concentrations below the abilities of PIXE (10–15 ppm) to less than 1 ppm by extrapolation of this linear relation.

Up to an Fe-content of approx. 2000 ppm, no quenching effect of Fe on this linear relationship occurs. However, Fe-contents above 2000 ppm result in a decrease of Mn-induced luminescence. Even at Fe-concentration >25,000 ppm spectroscopy reveals that Mn-activated CL of dolomite is not entirely extinguished.     

The latin American city and the symbolic impact of built environment

Cities as crystalisations of civilizations represent symbolic impact in their layout and architecture. Built environment in this sense has an symbolic impact. Intending to understand a civilization it can be helpful to look at these symbols. This article tries to demonstrate the changing symbols in different historic periods of Latin America. Symbols were to be found in the urban morphology of even the precolumbian cities. They changed within the colonial era, and again during the different influences of French, British or North American domination. Today there can be noticed a decline of the traditional symbolic elements of towns. On the other hand there are certain symptoms of a crisis of self-identity of the Latin Americans. So even the diverse ideas how to define a new image are to be seen in the built environment of main cities of various states. shortened version of a presentation to the Meeting of the Association of Pacific Coast Geographers at Eugene, Oregon, September 12, 1986 I wish to thank my friend William S. Preston, Department of Geography, Calif. Polytechnic State Univ. San Luis Obispo, for his patience helping me to translate this article. It was a pleasure to have a competent translater and partner of discussion.     

Analysis and optimization of wide-band force-balance seismometer responses

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Dynamics and contribution of karst groundwater to surface flow during Mediterranean flood

This paper describes the role of groundwater contribution to surface flow at the Causse d’Aumelas, a karst system near Montpellier (France), which is traversed by an intermittent river, the Coulazou. A first hydrologic model integrating a digital terrain model shows the inability of a standard rainfall-runoff model to replicate recorded flood hydrographs. While the flood peaks are routed through the karstic system along the Coulazou without a phase lag, the peak magnitude is somewhat modified. These results indicate an initial karst system recharge followed by a significant contribution to surface flow. A hydrodynamic analysis of ground-water flow confirms these results: the karst system first absorbs part of the rainfall, which induces a general water table rise within the aquifer, and then contributes to surface flow in the Coulazou.     

A Green Planet Versus a Desert World: Estimating the Maximum Effect of Vegetation on the Land Surface Climate

We quantify the maximum possible influence of vegetation on the global climate by conducting two extreme climate model simulations: in a first simulation (desert world), values representative of a desert are used for the land surface parameters for all non glaciated land regions. At the other extreme, a second simulation is performed (green planet) in which values are used which are most beneficial for the biosphere's productivity. Land surface evapotranspiration more than triples in the presence of the green planet, land precipitation doubles (as a second order effect) and near surface temperatures are lower by as much as 8 K in the seasonal mean resulting from the increase in latent heat flux. The differences can be understood in terms of more absorbed radiation at the surface and increased recycling of water. Most of the increase in net surface radiation originates from less thermal radiative loss and not from increases in solar radiation which would be expected from the albedo change. To illustrate the differences in climatic character and what it would imply for the vegetation type, we use the Köppen climate classification. Both cases lead to similar classifications in the extra tropics and South America indicating that the character of the climate is not substantially altered in these regions. Fundamental changes occur over Africa, South Asia and Australia, where large regions are classified as arid (grassland/desert) climate in the desert world simulation while classified as a forest climate in the green planet simulation as a result of the strong influence of maximum vegetation on the climate. This implies that these regions are especially sensitive to biosphere-atmosphere interaction.     

Potential of wind power projects under the Clean Development Mechanism in India

Background  

So far, the cumulative installed capacity of wind power projects in India is far below their gross potential (≤ 15%) despite very high level of policy support, tax benefits, long term financing schemes etc., for more than 10 years etc. One of the major barriers is the high costs of investments in these systems. The Clean Development Mechanism (CDM) of the Kyoto Protocol provides industrialized countries with an incentive to invest in emission reduction projects in developing countries to achieve a reduction in CO₂ emissions at lowest cost that also promotes sustainable development in the host country. Wind power projects could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable rural development, if developed correctly.     

Climate or development: is ODA diverted from its original purpose?

We analyze the interaction of climate and development policy that has taken place since the early 1990s. Increasing dissatisfaction about the results of traditional development cooperation and the appeal of climate policy as a new policy field led to a rapid reorientation of aid flows. At the turn of the century, over 7% of aid flows were spent on greenhouse gas emissions mitigation. However, the contribution of emissions mitigation projects to the central development objective of poverty reduction as specified in the Millennium Development Goals is limited and other project types are likely to be much more effective. Adaptation to climate change can be expected to have higher synergies with poverty alleviation than mitigation, primarily through its impact on health, the conservation of arable land and the protection against natural disasters. An analysis of the Clean Development Mechanism shows that projects addressing the poor directly are very rare; even small renewable energy projects in rural areas tend to benefit rich farmers and the urban population. Use of development aid for CDM projects and / or their preparation via capacity building is thus clearly not warranted. We further analyze whether the use of development aid for climate policy could be justified as a countermeasure against the emission increase related to successful development itself. However, countries that are achieving an improvement of human development from a low level are unlikely to increase their energy consumption substantially. Only at a level where the middle class expands rapidly, energy consumption and greenhouse gas emissions soar. Thus targeting middle class energy consumption by appliance efficiency standards and public transport-friendly urban planning are the most effective measures to address developing country emissions. Rural renewable energy provision in poor countries has a much higher impact on poverty, but a much lower impact on greenhouse gas emissions. We conclude that while there are valid reasons for long-term collaboration with emerging economies on greenhouse gas mitigation, there should be a separate budget line for such activities to avoid “obfuscation” of a decline of resources aimed at poverty alleviation. Nevertheless, mitigation will remain attractive for donors because it ensures quick disbursements and relatively simple measures of success. Moreover, mitigation activities in developing countries provide politicians in industrialized countries with a welcome strategy to divert the attention of their constituencies from the lack of success in reducing greenhouse gas emissions domestically.     

A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa

International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such...