The effects of explosive-driven shocks on the natural remanent magnetization and the magnetic properties of rocks

International audienc

Paleoproterozoic structural evolution of the Eglab domain (Eglab shield, Algeria) from aeromagnetic data and anisotropy of magnetic susceptibility (AMS) study of the post-collisional Aftout granitoids

International audienceNew interpretation of the aeromagnetic data allowed strong improvement in the knowledge of the Eglab domain, better specifying major deep structures. This domain corresponds to a regional extension of the unfoliated Aftout granitoids. In order to correlate this deep structures with those at the rock scale, AMS analyses were performed on these Aftout granitoids. Samples were collected in spaced sites along long profiles. Rockmagnetic studies have shown that magnetic fabric is mainly carried by large magnetite grains. AMS data appeared with different characteristics within two large compartments separated by a NE-SW limit that corresponds to a border of the Kahal Morrat corridor (KMC), a major structure evidenced by aeromagnetic data analyses. To the SE, the magnetic foliation and lineation are homogeneous (mainly ESE-WNW to E-W subvertical magnetic foliation and subhorizontal magnetic lineation). To the NW, the declination of the magnetic foliation and the plunge of the magnetic lineation show significant local variations, without coherency from one site to another. That highlights different stress field conditions (and then different depths) during emplacement. The major deep crustal structure separating these two compartments allowed a considerable relative uplift of the SE part of the Eglab domain relatively to the NW part. This period was also characterized by a cataclysmic volcanism in a very large area around the KMC, suggesting a relation with this deep structure

The fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV), April 9-12, 2017, Algiers (Algeria)

International audienceWe present a report about the fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV) that took place in Algiers at the USTHB (Université des Sciences et Technologie Houari Boumedienne, Algiers, Algeria) in the presence of the presidents of the USTHB and Boumerdès Universities, the Director of CRAAG (Centre de Recherche en Astronomie, Astrophysique et Géophysique), and the General Director of the National Administration for Scientific Research (NASR/DGRSDT). This series of conferences aims to promote research interest for impact cratering in the Arab world and beyond, including for instance in African countries. In spite of persistently restraining travel measures to Algeria, the fourth edition held in Algiers was marked by continuous international participation, with participants from seven different countries. This conference focused on presentations of scientific results in the research fields related to planetology, meteorites, and impact craters. In particular, the Algerian impact structures were under the spotlights during both oral and poster sessions. During this conference, the presence of freshly graduated Ph.D. students and new Ph.D. projects related to impact cratering or meteoritic science was a positive sign for the consolidation of research groups in this domain in the Arab world and Africa. Therefore, international cooperation or external support and funding are still needed to ensure the development of this scientific discipline in this part of the world

GEOPHYSICAL CONSTRAINTS ON THE STRUCTURE, FORMATION PROCESS, AND AGE OF THE MAADNA CRATER (TALEMZANE, ALGERIA).

79th Annual Meeting of the Meteoritical-Society, Berlin, GERMANY, AUG 07-12, 2016International audienc

Geophysical and magneto-structural study of the Maâdna structure (Talemzane, Algeria): Insights on its age and origin

International audienceThe Maâdna structure is located approximately 400 km south of Algiers (33°19' N, 4°19' E) and emplaced in Upper-Cretaceous to Eocene limestones. Although accepted as an impact crater on the basis of alleged observations of shock-diagnostic features such as planar deformation features (PDFs) in quartz grains, previous works were limited and further studies are desirable to ascertain the structure formation process and its age. For this purpose, the crater was investigated using a multidisciplinary approach including field observations, detailed cartography of the different geological and structural units, geophysical surveys, anisotropy of magnetic susceptibility, paleomagnetism, and petrography of the collected samples. We found that the magnetic and gravimetric profiles highlight a succession of positive and negative anomalies, ones that might indicate the occurrence of a causative material which is at least in part identical. Geophysical analysis and modeling suggest the presence of this material within the crater at a depth of about 100 m below the surface. Using soil magnetic susceptibility measurements, the shallowest magnetized zone in the central part of the crater is identified as a recently deposited material. Paleomagnetic and rock magnetic experiments combined with petrographic observations show that detrital hematite is the main magnetic carrier although often associated with magnetite. A primary magnetization is inferred from a stable remanence with both normal and reverse directions, carried by these two minerals. Although this is supposed to be a chemical remagnetization, its normal polarity nature is considered to be a Pliocene component, subsequent to the crater formation. The pole falls onto the Miocene-Pliocene part of the African Apparent Polar Wander Path (APWP). Consequently, we estimate then formation of the Ma^adna crater to have occurred during the time period extending from the Late Miocene to the Early Pliocene. Unfortunately, our field and laboratory investigations do not allow us to confirm an impact origin for the crater as neither shatter cones, nor shocked minerals, were found. A dissolved diapir with inverted relief is suggested as an alternative to the impact hypothesis, which can still be considered as plausible. Only a drilling may provide a definite answer

A Ring-Distortion Strategy from Marine Natural Product Ilimaquinone Leads to Quorum Sensing Modulators

WOS:000434220200016International audienceWe report herein a ring-distortion strategy applied to marine natural substances ilimaquinone and 5-epi-ilimaquinone. A chemically diverse library of molecules was synthesised that included rearrangements of the sesquiterpene moiety and original reorganisations of the quinone ring. Chemoinformatic analyses evaluated the rise of structural diversity and the exploration of chemical space. Some focussed biological activities of this library were also investigated; quorum sensing activity of Vibrio harveyi was envisaged and some of the new compounds were shown to be good quorum sensing inhibitor candidates, whereas others were activators. Toxicities were also evaluated and some products showed micromolar activities against human umbilical vein endothelium, human hepatocellular carcinoma and human lung carcinoma (A549) cells

The State of Planetary and Space Sciences in Africa

Africa has an enormous potential to provide insights into planetary and space sciences, but it has remained largely untapped. Fostering a new generation of scientists promises far-reaching benefits

Africa Initiative for Planetary and Space Sciences

Elevating planetary and space sciences across Africa could help nations reach their development goals. Efforts will require collaboration, creativity, efficient planning, and political will