Contamination des sédiments récents après leur prélèvement

The hydrocarbon content of recent sediments is often very low. Consequently, account must be taken of the numerous possibilities of contamination, which may completely obscure analytical results and, therefore, their interpretation. Two new contaminants are described and their causes determined: (1) hydrocarbons, essentially even-numbered $\text{n-}\text{alkanes}$, from the polyethylene core sleeves of Kullenberg corers, (2) $\text{n-}\text{heptadecane}$, biosynthesized during the storage of wet sediments at 4°C, in darkness.In order to avoid these contaminants, it is advisable to core without plastic core sleeves, and to store the freeze-dried sediments in metal or glassware, under an inert atmosphere. Some of the conclusions of previously published works about hydrocarbons in recent sediments should be re-evaluated.     

Extension et sédimentation au paléozoïque terminal et au Mésozoïque dans le bassin de Majunga (Nord-Ouest de Madagascar)

The Majunga Basin is located in the northwestern part of Madagascar with a N45–60°E trending axis. It was filled by almost exclusively continental Karoo Supergroup sediments, which are Permian to Early Jurassic in age, and by younger sequences, mainly marine, that were deposited from the Middle Jurassic to the present.The Karoo Basin geometry is deduced from the analysis of seismic sections. A central northeast trending horst is flanked by two sub-basins. Deposition of the Karoo sequences was controlled by these northeast trending faults. On the contrary, the Middle Jurassic to present sequences witness only a slight tilting of the basement towards the northwest.The development of the Majunga Basin includes, therefore, two successive stages. In the synrift episode, from Permian to Early Jurassic times, the sedimentation was syntectonic, controlled by synsedimentary faulting and the creation of a horst and graben extensive pattern. The postrift episode started during the Middle Jurassic.These two stages of the Majunga Basin development correspond to the geodynamic evolution recorded elsewhere in this part of the Gondwana.     

Quantifying the effectiveness of climate change mitigation through forest plantations and carbon sequestration with an integrated land-use model

Background

Carbon plantations are introduced in climate change policy as an option to slow the build-up of atmospheric carbon dioxide (CO₂) concentrations. Here we present a methodology to evaluate the potential effectiveness of carbon plantations. The methodology explicitly considers future long-term land-use change around the world and all relevant carbon (C) fluxes, including all natural fluxes. Both issues have generally been ignored in earlier studies.

Results

Two different baseline scenarios up to 2100 indicate that uncertainties in future land-use change lead to a near 100% difference in estimates of carbon sequestration potentials. Moreover, social, economic and institutional barriers preventing carbon plantations in natural vegetation areas decrease the physical potential by 75–80% or more. Nevertheless, carbon plantations can still considerably contribute to slowing the increase in the atmospheric CO₂ concentration but only in the long term. The most conservative set of assumptions lowers the increase of the atmospheric CO₂ concentration in 2100 by a 27 ppm and compensates for 5–7% of the total energy-related CO₂ emissions. The net sequestration up to 2020 is limited, given the short-term increased need for agricultural land in most regions and the long period needed to compensate for emissions through the establishment of the plantations. The potential is highest in the tropics, despite projections that most of the agricultural expansion will be in these regions. Plantations in high latitudes as Northern Europe and Northern Russia should only be established if the objective to sequester carbon is combined with other activities.

Conclusion

Carbon sequestration in plantations can play an important role in mitigating the build-up of atmospheric CO₂. The actual magnitude depends on natural and management factors, social barriers, and the time frame considered. In addition, there are a number of ancillary benefits for local communities and the environment. Carbon plantations are, however, particularly effective in the long term. Furthermore, plantations do not offer the ultimate solution towards stabilizing CO₂ concentrations but should be part of a broader package of options with clear energy emission reduction measures.     

Austerity urbanism and the promise of immigrant- and refugee-centered urban revitalization in the US Rust Belt

Recent urban studies research emphasizes the unevenness of local responses to immigration in the United States and the emergence of economic development-focused inclusionary initiatives as a response to neoliberal downscaling in the Rust Belt. Scholars also highlight the impact of austerity urbanism – the deepening of neoliberal urbanism – in Rust Belt cities following the 2007–2008 financial crisis, noting its potential to produce progressive activism. This article considers the relationship between downscaling, austerity urbanism, and immigration activism in the Rust Belt by analyzing economic revitalization narratives within a regional consortium of inclusionary initiatives. My findings underscore the incongruities and compromises encompassed by welcoming coalitions operating in the age of austerity. Some local actors are motivated by growth agendas but affirm inclusionary values toward immigrants and refugees to substantiate them. Other actors are motivated by social justice agendas but cite the economic benefits of immigration to garner support from other factions.