A new amber deposit from the Cretaceous (uppermost Albian-lowermost Cenomanian) of southwestern France

A Cretaceous amber deposit has recently been discovered in a quarry of Charente-Maritime (southwestern France), at Cadeuil. This paper presents the sedimentary and palaeoenvironmental settings of the uppermost Albian-lowermost Cenomanian series including the amber deposit. A preliminary analysis of the amber samples reveals diverse fossil arthropods (a few mites and at least 20 insect families within 9 orders), as well as numerous micro-organisms, mainly algae and mycelia. A myceloid colony of bacteria, a flagellate algae and four especially well preserved insects are illustrated (Diptera Dolichopodidae, Diptera Chironomidae, Hymenoptera Parasitica, and Heteroptera Tingidae). The abundance of the limnic micro-organisms is discussed in terms of bloom events. Their relative scarcity in almost all the amber pieces containing fossil arthropods is attributed to differences in the origin of resin: production along trunk and branches for amber with arthropods; production by aquatic roots for amber rich in algae. The absence of pollen and spores in amber is attributed to differences in the respective periods of resin and palynomorph production, which may be related to a seasonal climate during the Albian-Cenomanian transition in Western Europe.     

Particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine,Goesdorf, Luxembourg

Particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine (Goesdorf, Luxembourg) were quantified by single particle counting based on light scattering (100 nm–2 μm) combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction. This water system was chosen as a surrogate for groundwaters. The dependence of the colloid number concentration on colloid diameters can be described by a power-law distribution in all cases. Power-law slopes ranged from −3.30 to −4.44, depending on water ionic strength and flow conditions. The same main mineral types were found in the different samples: 2:1 phyllosilicates (illite and mica), chlorite, feldspars (albite and orthoclase), calcite and quartz; with a variable number of Fe oxide particles. The colloid mineralogical composition closely resembles the composition of the parent rock. Spatial variations in the structure and composition of the rock in contact with the waters, i.e. fissured rock versus shear joints, are reflected in the colloid composition. The properties of the study colloids, as well as the processes influencing them, can be considered as representative of the colloids present in groundwaters.     

Geology, petrology and isotope geochemistry of massif-type anorthosites from southwest Madagascar

Four massif-type anorthosite bodies 25–100 km² in area occur within high-pressure granulite facies supracrustal gneisses in southwestern Madagascar. Two of these bodies (Ankafotia and Saririaky) appear to have been pulled apart by 40 km in a ductile shear zone, but structural features such as sub-vertical stretching lineations indicate an origin by intense west-directed flattening and pure shear. Country rocks (Graphite Series) include abundant graphite schist (some with >60% graphite), marble, quartzite, and minor amphibolite and leucogneiss. Comagmatic granitoids (e.g. charnockites) are conspicuously absent. The anorthosite bodies are dominated by coarse grained anorthosites and leuconorites (feldspars typically 3–5 cm, up to 1 m); minor norites and oxide-rich ferrogabbros occur near the margins, but ultramafic rocks are absent. Typical mineralogy of the anorthositic rocks is: plagioclase (An_41–54) + orthopyroxene (En_38–66) ± augite (Mg♯ = 32–68) ± ilmenite ± magnetite ± apatite. High-alumina (to 6.1 wt% Al₂O₃) orthopyroxene megacrysts are widespread; most have exsolutions of calcic plagioclase (An_72–85) but some contain garnet lamellae. Metamorphism has produced abundant recrystallization and sporadic coronitic garnet (Mg ♯=12–36) + clinopyroxene assemblages. Rb-Sr isotopic analyses of whole-rocks and minerals reveal no meaningful age relationships. The age of late Neoproterozoic metamorphism is best constrained at 559 ± 50 Ma by a 6-point Sm-Nd mineral isochron (whole rock, plag, pyx, ilm, apat, gar) from a Saririaky oxide-rich gabbro. The igneous crystallization age of the anorthosites is estimated at 660 ± 60 Ma by a 19-point combined whole-rock and mineral Sm-Nd isochron for samples from both the Ankafotia and Saririaky bodies. Initial isotopic ratios calculated at 0.66 Ga among 13 whole rocks are: _Nd=+2.6 to +5.2 (mean=+3.7) and I_Sr=0.70328–0.70407 (mean=0.70347), indicating derivation of the Malagasy anorthosites from a depleted mantle source, and little, if any, contamination with Archean crustal material. One anorthosite sample with _Nd=−1.4 and I_Sr=0.70344 (calculated at 0.66 Ga) probably reflects the effects of assimilation of Early to Middle Proterozoic crustal basement, but typical surrounding graphite schist (_Nd=+0.3, I_Sr=0.70636, both at 0.66 Ga; T_DM= 1131 Ma) represents only a minor potential contaminant for the anorthosite bodies. T_DM model ages of the Malagasy anorthosites (797–1280 Ma; mean of 14 samples=949 Ma), as those of most other massif-type anorthosites, are older than the true crystallization age, because of crustal contamination effects. Our isotopic data, together with recent U-Pb data from the anorthosites and surrounding country rocks, are consistent with emplacement of the Malagasy anorthosite bodies at or before the start of a protracted, high-grade metamorphic event or series of events between about 630 and 550 Ma. This period coincides with the collision between, and amalgamation of, East and West Gondwana. Received: 19 December 1997 / Accepted: 12 June 1998     

Climate change and the water–energy–food nexus: insights from policy and practice in Tanzania

The threat of climate change is emerging at a time of rapid growth for many economies in sub-Saharan Africa (SSA). Dominant narratives comprising ambitious development plans are common and often based around sectors with strong inter-dependencies that are highly exposed to climate variability. Using document analysis and key informant interviews, this article examines how climate change is addressed in policy, how it is being mainstreamed into water, energy and agriculture sector policies and the extent to which cross-sectoral linkages enable coordinated action. These questions are addressed through a case study of Tanzania, highlighting broader lessons for other developing countries, particularly those in SSA facing similar challenges. The article finds that, while the agriculture and water sectors are increasingly integrating climate change into policies and plans in Tanzania, practical coordination on adaptation remains relatively superficial. Publication of the Tanzania National Adaptation Plan of Action (NAPA) in 2007 marked a step change in the integration of climate change in sectoral policies and plans; however, it may have reinforced a sectoral approach to climate change. Examining the policies for coherence highlights overlaps and complementarities which lend themselves to a coordinated approach. Institutional constraints (particularly structures and resources) restrict opportunities for inter-sectoral action and thus collaboration is confined to ad hoc projects with mixed success to date. The results highlight the need for institutional frameworks that recognize and address these constraints to enable development goals to be pursued in a more sustainable and climate-resilient manner.

KEY POLICY INSIGHTS

• The NAPA has been successful at encouraging climate change mainstreaming into sectoral policies in Tanzania; however, the cross-sectoral collaboration crucial to implementing adaptation strategies remains limited due to institutional challenges such as power imbalances, budget constraints and an ingrained sectoral approach.

• Collaboration between nexus sectors in Tanzania is largely through ad hoc projects with limited progress on establishing deeper connections to enable collaboration as a process. Regular cross-sectoral planning meetings and consistent annual budgets could provide a platform to enhance cross-sectoral coordination.

• Plans to develop hydropower and agriculture are prevalent across sub-Saharan Africa. Insights from Tanzania highlight the importance of institutional and policy frameworks that enable cross-sectoral coordination.

     

CMIP5 simulated climate conditions of the Greater Horn of Africa (GHA). Part II: projected climate

This is the second of the two-part paper series on the analysis and evaluation of the Fifth phase of Coupled Model Intercomparison Project (CMIP5) simulation of contemporary climate as well as IPCC, AR5 Representative Concentrations Pathways (RCP), 4.5 and 8.5 scenarios projections of the Greater Horn of Africa (GHA) Climate. In the first part (Otieno and Anyah in Clim Dyn, 2012) we focused on the historical simulations, whereas this second part primarily focuses on future projections based on the two scenarios. Six Earth System Models (ESMs) from CMIP5 archive have been used to characterize projected changes in seasonal and annual mean precipitation, temperature and the hydrological cycle by the middle of twenty-first century over the GHA region, based on IPCC, 5th Assessment Report (AR5) RCP4.5 and RCP8.5 scenarios. Nearly all the models outputs analyzed reproduce the correct mean annual cycle of precipitation, with some biases among the models in capturing the correct peak of precipitation cycle, more so, March–April–May (MAM) seasonal rainfall over the equatorial GHA region. However, there is significant variation among models in projected precipitation anomalies, with some models projecting an average increase as others project a decrease in precipitation during different seasons. The ensemble mean of the ESMs indicates that the GHA region has been experiencing a steady increase in both precipitation and temperature beginning in the early 1980s and 1970s respectively in both RCP4.5 and RCP8.5 scenarios. Going by the ensemble means, temperatures are projected to steadily increase uniformly in all the seasons at a rate of 0.3/0.5 °C/decade under RCP4.5/8.5 scenarios over northern GHA region leading to an approximate temperature increase of 2/3 °C by the middle of the century. On the other hand, temperatures will likely increase at a rate of 0.3/0.4 °C/decade under RCP4.5/8.5 scenarios in both equatorial and southern GHA region leading to an approximate temperature increase of 2/2.5 °C by the middle of twenty-first century. Nonetheless, projected precipitation increase varied across seasons and sub-regions. With the exception of the equatorial region, that is projected to experience precipitation increase during DJF season, most sub-regions are projected to experience precipitation increase within their peak seasons, with the highest rate of increase experienced during DJF and OND seasons over southern and equatorial GHA regions respectively. Notably, as precipitation increases, the deficit (E < P) between evaporation (E) and precipitation (P) increased over the years, with a negatively skewed distribution. This generally implies that there is a high likelihood of an increased deficit in local moisture supply. This remarkable change in the general hydrological cycle (i.e. deficit in local moisture) is projected to be also coincident with intensified westerly anomaly influx from the Congo basin into the region. However, better understanding of the detailed changes in hydrological cycle will require comprehensive water budget analyses that require daily or sub-daily variables, and was not a specific focus of the present study.     

Exploring the past through lynchet landscapes in the Vosges Mountains and the Lorraine Plateau (France)

Lynchets are ridges formed by erosion and sediment accumulation downstream of agricultural plots and offer valuable insights into past agricultural activity. These microtopographies cover vast areas and serve as indicators of historical changes in land use. As a result, their ubiquity across Europe makes them particularly interesting. In this study, we propose a geoarchaeological approach to analyze six lynchets, four in the Vosges Mountains and two on the Lorraine Plateau (France). The lynchets can be considered soil archives with no stratigraphic organization or chronological sequence from bottom to top, making it difficult to determine the age of the lynchets and identify changes in land use over time. To this end, we propose the analysis of historical and geo-historical archives combined with the “pedosedimentary” archives of lynchets through charcoal identification and dating combined with near-infrared spectroscopy to determine the age, vegetation, and past land use changes associated with lynchet landscapes. By combining these multiple data sources, we are better able to show the chronological development of these ancient agricultural systems and uncover valuable information on landscape history. Charcoal dating suggests a higher frequency of fires from the Middle Ages. The dating aligns with the regional dynamics of anthropogenic fires, indicating a potential use of fire for cultural purposes. We also demonstrate the difficulty of extrapolating the dating of a lynchet to the entire lynchet system. Our results highlight the difficulties of interpreting the formation and dating of lynchets and the lynchet system on the sole basis of charcoal analysis. However, we highlight the value of applying pedoanthracology to lynchets to determine the dynamics of land use change in former fields.     

Scientific detector workshop 2022 on-sky performance verification of near-infrared e−APD technology for wavefront sensing and demonstration of e−APD pixel performance to improve the sensitivity of large science focal planes

Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e⁻APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is m_k = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10⁻³ e⁻/s have been demonstrated with 1Kx1K e⁻APD arrays and 2Kx2K e⁻APD arrays have already been developed, the possibilities and adaptations of e⁻APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed.