Detrital zircon sources in the Ordovician metasedimentary rocks of the Moroccan Meseta: Inferences for northern Gondwanan passive-margin paleogeography

ABSTRACT Detrital zircon U-Pb geochronology has been widely used to constrain the pre-Carboniferous geography of the European and, to a lesser extent, the Moroccan Variscides. The latter have been generally considered as part of a long-lasting passive margin that characterized northern Gondwana from Ordovician to Devonian time, and was subsequently involved in the late Paleozoic Variscan orogeny. We report detrital zircon ages for three Early to Late Ordovician samples from the Beni Mellala inlier in the northeastern part of the Western Moroccan Meseta in order to discuss the temporal evolution of the sources of sediments in this region. The detrital zircon spectra of these samples, characterized by two main populations with mean ages of 630–610 Ma and 2170–2060 Ma, are typical of Cambrian–Devonian rocks from the Moroccan Variscides and confirm their link to the West African craton. A minor Stenian–Tonian population (peak at ca. 970 Ma) suggests the influence of a distant and intermittent NE African source (Sahara metacraton), which was probably interrupted after Ordovician time. Our data support previous interpretations of the Moroccan Meseta (and the entire northern Moroccan Variscides) as part of the northern Gondwana passive margin. The main sources of these sediments would have been the West African craton in the western regions of the passive margin (Moroc- can Meseta and central European Paleozoic massifs), and the Arabian-Nubian Shield and/or Sahara metacraton in the eastern areas (Libya, Egypt, Jordan, central and NW Iberian zones during Paleozoic time), where the 1.0 Ga detrital zircon population is persistent throughout the Ordovician–Devonian time span.

New Insights Into c.815_824dup Pathogenic Variant of BRCA1 in Inherited Breast Cancer: A Founder Mutation of West African Origin

Founder mutations have been reported in BRCA1 and BCRA2 in different ethnic groups with inherited breast cancer. Testing of targeted mutations in specific populations is important for cancer prevention in mutation carriers. In Sub-Saharan Africa, only a few studies have reported specific founder mutations in inherited breast cancer. The pathogenic variant c.815_824dup of BRCA1 has been reported as the most frequent among African American populations with inherited breast cancer and was supposed to have a West African origin. Recent report from Senegal identified this variant in women with inherited breast cancer at the highest frequency ever reported. The variant was linked to a common haplotype confirming its founder effect in West Africa. In this article, we review the mutation history of c.815_824dup and discuss how it spread out of Africa through the transatlantic slave trade.

A synthetic view of rainfall intensification in the West African Sahel

The West African Sahel has been facing for more than 30 years an increase in extreme rainfalls with strong socio-economic impacts. This situation challenges decision-makers to define adaptation strategies in a rapidly changing climate. The present study proposes (i) a quantitative characterization of the trends in extreme rainfalls at the regional scale, (ii) the translation of the trends into metrics that can be used by hydrological risk managers, (iii) elements for understanding the link between the climatology of extreme and mean rainfall. Based on a regional non-stationary statistical model applied to in-situ daily rainfall data over the period 1983-2015, we show that the region-wide increasing trend in extreme rainfalls is highly significant. The change in extreme value distribution reflects an increase in both the mean and variability, producing a 5%/decade increase in extreme rainfall intensity whatever the return period. The statistical framework provides operational elements for revising the design methods of hydraulic structures which most often assume a stationary climate. Finally, the study shows that the increase in extreme rainfall is more attributable to an increase in the intensity of storms (80%) than to their occurrence (20%), reflecting a major disruption from the decadal variability of the rainfall regime documented in the region since 1950.

On the taxonomy of Negeta semialba Hampson, 1918 with descriptions of two new Leucobaeta László, Ronkay & Witt, 2010 species (Lepidoptera, Nolidae, Nolinae)

The taxonomic position of the West African Negeta semialba Hampson, 1918 is revised and the species is transferred from the genus Negeta Walker, 1862 of Westermanniinae to Leucobaeta László, Ronkay & Witt, 2010 of Nolinae: Leucobaeta semialba (Hampson, 1918) comb. n., based on morphological analysis. The hitherto unknown male adult and genitalia of both sexes are described and illustrated. Leucobaeta semialba is compared to the superficially similar Afrotropical Negeta mesoleuca (Holland, 1894) and N. ruficeps (Hampson, 1902); two sibling species from East Africa and Madagascar are described as new to science: L. smithi and L. malagassa spp. n. Pairwise genetic distances of COI-5P sequences between the taxa are provided.

Regional Integration in the West African Economic and Monetary Union (WAEMU): Complementarity or Competition?

This paper analyzes and characterizes the nature of the interactions between countries of the West African Economic and Monetary Union (WAEMU) over the period 1995–2015. The analysis uses sigma-convergence on the one hand and the Dendrinos-Sonis spatial competition model estimated by the SUR method on the other hand. The results show a lack of convergence of living standards and support the idea of income polarization in space; these results also support the idea of a very poorly integrated region with relatively competitive interrelationships. The paper suggests the acceleration of regional integration in the WAEMU region combined with the implementation of inclusive integration policies that promote each member’s comparative advantage.