Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting

Based on field work and seismic reflection data, we investigate the Cenozoic tectono-sedimentary evolution offshore and onshore Ibiza allowing the proposal of a new tectonic agenda for the region and its integration in the geodynamic history of the West Mediterranean. The late Oligocene-early Miocene rifting event, which characterizes the Valencia Trough and the Algerian Basin, located north and south of the study area respectively, is also present in Ibiza and particularly well-expressed in the northern part of the island. Among these two rifted basins initiated in the frame of the European Cenozoic Rift System, the Valencia Trough failed rapidly while the Algerian Basin evolved after as a back-arc basin related to the subduction of the Alpine-Maghrebian Tethys. The subsequent middle Miocene compressional deformation was localized by the previous extensional faults, which were either inverted or passively translated depending on their initial orientation. Despite the lateral continuity between the External Betics and the Balearic Promontory, it appears from restored maps that this tectonic event cannot be directly related to the Betic orogen, but results from compressive stresses transmitted through the Algerian Basin. A still active back-arc asthenospheric rise likely explains the stiff behavior of this basin, which has remained poorly deformed up to recent time. During the late Miocene a new extensional episode reworked the southern part of the Balearic Promontory. It is suggested that this extensional deformation developed in a trans-tensional context related to the westward translation of the Alboran Domain and the coeval right-lateral strike-slip movement along the Emile Baudot Escarpment bounding the Algerian Basin to the north. (C) 2016 Elsevier B.V. All rights reserved

An Early Cretaceous vertebrate assemblage from the Cabao Formation of NW Libya

Fossil vertebrates from the Cabao Formation discovered in the area of Nalut in northwestern Libya include the hybodont shark Priohybodus, the crocodilian Sarcosuchus, an abelisaurid, a baryonichine spinosaurid and a large sauropod with spatulate teeth. The Cabao Formation may be Hauterivian to Barremian in age, although an earlier Berriasian to Valanginian age cannot be excluded. Its dinosaur assemblage is reminiscent of that of the El Rhaz and Tiouraren formations of Niger and strongly differs from both the Cenomanian assemblages of Morocco and Egypt and the Late Aptian to Albian fauna of Tunisia. Fossil vertebrates may be an important tool to establish the stratigraphical framework of the poorly dated Early Cretaceous continental deposits of Afric

Les reliques téthysiennes en Méditerranée orientale: les bassins Ionien, d'Hérodote et du Levant

National audienc

Microfossils from the late Mesoproterozoic - early Neoproterozoic Atar/El Mreiti Group, Taoudeni Basin, Mauritania, northwestern Africa

The well-preserved Meso-Neoproterozoic shallow marine succession of the Atar/El Mreïti Group, in the Taoudeni Basin, Mauritania, offers a unique opportunity to investigate the mid-Proterozoic eukaryotic record in Western Africa. Previous investigations focused on stromatolites, biomarkers, chemostratigraphy and palaeoredox conditions. However, only a very modest diversity of organic-walled microfossils (acritarchs) has been documented. Here, we present a new, exquisitely well-preserved and morphologically diverse assemblage of organic-walled microfossils from three cores drilled through the Atar/El Mreïti Group. A total of 48 distinct entities including 11 unambiguous eukaryotes (ornamented and process-bearing acritarchs), and 37 taxonomically unresolved taxa (including 9 possible eukaryotes, 6 probable prokaryotes, and 22 other prokaryotic or eukaryotic taxa) were observed. Black shales preserve locally abundant fragments of organic-rich laminae interpreted as benthic microbial mats. We also document one of the oldest records of Leiosphaeridia kulgunica, a species showing a circular opening interpreted as a sophisticated circular excystment structure (a pylome), and one of the oldest records of Trachyhystrichosphaera aimika and T. botula, two distinctive process-bearing acritarchs present in well-dated 1.1 Ga formations at the base of the succession. The general assemblage composition and the presence of three possible index fossils (A. tetragonala, S. segmentata and T. aimika) support a late Mesoproterozoic to early Neoproterozoic (Tonian) age for the Atar/El Mreïti Group, consistent with published lithostratigraphy, chemostratigraphy and geochronology. This study provides the first evidence for a moderately diverse eukaryotic life, at least 1.1 billion years ago in Western Africa. Comparison with coeval worldwide assemblages indicates that a broadly similar microbial biosphere inhabited (generally redox-stratified) oceans, placing better time constraints on early eukaryote palaeogeography and biostratigraphy.Research support from BELSPO IAP PLANET TOPERS to J. Beghin (PhD scholarship) and E.J. Javaux (PI), and European Research Council (ERC) Stg ELiTE FP7/308074 to J.-Y. Storme (postdoc fellowship) and E.J. Javaux (PI) are gratefully acknowledged. J.J. Brocks acknowledges support from the Australian Research Council (DP1095247)

Evidence for Anthropogenic Surface Loading as Trigger Mechanism of the 2008 Wenchuan Earthquake

Two and a half years prior to China's M7.9 Wenchuan earthquake of May 2008, at least 300 million metric tons of water accumulated with additional seasonal water level changes in the Minjiang River Valley at the eastern margin of the Longmen Shan. This article shows that static surface loading in the Zipingpu water reservoir induced Coulomb failure stresses on the nearby Beichuan thrust fault system at <17km depth. Triggering stresses exceeded levels of daily lunar and solar tides and perturbed a fault area measuring 416+/-96km^2. These stress perturbations, in turn, likely advanced the clock of the mainshock and directed the initial rupture propagation upward towards the reservoir on the "Coulomb-like" Beichuan fault with rate-and-state dependent frictional behavior. Static triggering perturbations produced up to 60 years (0.6%) of equivalent tectonic loading, and show strong correlations to the coseismic slip. Moreover, correlations between clock advancement and coseismic slip, observed during the mainshock beneath the reservoir, are strongest for a longer seismic cycle (10kyr) of M>7 earthquakes. Finally, the daily event rate of the micro-seismicity (M>0.5) correlates well with the static stress perturbations, indicating destabilization.Comment: 22 pages, 4 figures, 3 table

A palaeoecological model for the late Mesoproterozoic – early Neoproterozoic Atar/El Mreïti Group, Taoudeni Basin, Mauritania, northwestern Africa

Reconstructing the spatial distribution of early eukaryotes in palaeoenvironments through Proterozoic sedimentary basins provides important information about their palaeocology and taphonomic conditions. Here, we combine the geological context and a reconstruction of palaeoenvironmental redox conditions (using iron speciation) with quantitative analysis of microfossil assemblages (eukaryotes and incertae sedis), to provide the first palaeoecological model for the Atar/El Mreïti Group of the Taoudeni Basin. Our model suggests that in the late Mesoproterozoic – early Neoproterozoic, the availability of both molecular oxygen and nutrients controlled eukaryotic diversity, higher in oxic shallow marginal marine environments, while coccoidal colonies and benthic microbial mats dominated respectively in anoxic iron-rich and euxinic waters during marine highstands or away from shore where eukaryotes are lower or absent

TAOK2 Kinase Mediates PSD95 Stability and Dendritic Spine Maturation through Septin7 Phosphorylation

Abnormalities in dendritic spines are manifestations of several neurodevelopmental and psychiatric diseases. TAOK2 is one of the genes in the 16p11.2 locus, copy number variations of which are associated with autism and schizophrenia. Here, we show that the kinase activity of the serine/threonine kinase encoded by TAOK2 is required for spine maturation. TAOK2 depletion results in unstable dendritic protrusions, mislocalized shaft-synapses, and loss of compartmentalization of NMDA receptor-mediated calcium influx. Using chemical-genetics and mass spectrometry, we identified several TAOK2 phosphorylation targets. We show that TAOK2 directly phosphorylates the cytoskeletal GTPase Septin7, at an evolutionary conserved residue. This phosphorylation induces translocation of Septin7 to the spine, where it associates with and stabilizes the scaffolding protein PSD95, promoting dendritic spine maturation. This study provides a mechanistic basis for postsynaptic stability and compartmentalization via TAOK2-Sept7 signaling, with implications toward understanding the potential role of TAOK2 in neurological deficits associated with the 16p11.2 region

Microfossils from the late Mesoproterozoic – early Neoproterozoic Atar/El Mreïti Group, Taoudeni Basin, Mauritania, northwestern Africa

The well-preserved Meso-Neoproterozoic shallow marine succession of the Atar/El Mreïti Group, in the Taoudeni Basin, Mauritania, offers a unique opportunity to investigate the mid-Proterozoic eukaryotic record in Western Africa. Previous investigations focused on stromatolites, biomarkers, chemostratigraphy and palaeoredox conditions. However, only a very modest diversity of organic-walled microfossils (acritarchs) has been documented. Here, we present a new, exquisitely well-preserved and morphologically diverse assemblage of organic-walled microfossils from three cores drilled through the Atar/El Mreïti Group. A total of 48 distinct entities including 11 unambiguous eukaryotes (ornamented and process-bearing acritarchs), and 37 taxonomically unresolved taxa (including 9 possible eukaryotes, 6 probable prokaryotes, and 22 other prokaryotic or eukaryotic taxa) were observed. Black shales preserve locally abundant fragments of benthic microbial mats. We also document one of the oldest records of Leiosphaeridia kulgunica, a species showing a pylome interpreted as a sophisticated circular excystment structure, and one of the oldest records of Trachyhystrichosphaera aimika and T. botula, two distinctive process-bearing acritarchs present in well-dated 1.1 Ga formations at the base of the succession. The general assemblage composition and the presence of three possible index fossils (A. tetragonala, S. segmentata and T. aimika) support a late Mesoproterozoic to early Neoproterozoic (Tonian) age for the Atar/El Mreïti Group, consistent with published lithostratigraphy, chemostratigraphy and geochronology. This study provides the first evidence for a moderately diverse eukaryotic life, at least 1.1 billion years ago in Western Africa. Comparison with coeval worldwide assemblages indicate that a broadly similar microbial biosphere inhabited (generally redox-stratified) oceans, placing better time constraints on early eukaryote palaeogeography and biostratigraphy

Signification sédimentologique des oolithes calcaires et bioclastes noircis remaniés au Sud-Est de l'île de Djerba

The nuclei of the calcareous ooids found south-east off Djerba are mostly composed of blackened epiphytic forami-nifera whose coloration appears to be due to a neogenetic argilaceous mineral belonging to the chlorite family. The genesis of these ooids, does not appear to be actual but very recent. It could be contemporaneous of the last climatic warming, whereas the chlorite neogenesis seems actually lasting in some restricted and well defined areas of the pelagian platform.Les nucléus des oolithes calcaires trouvées dans les prélèvements situés au sud-est de l'île de Djerba sont très souvent constitués par des Foraminifères épiphytes dont la teinte noire est due à un minéral argileux de néogenèse de la famille des Chlorites. La formation des oolithes de ce secteur, sans être actuelle, serait cependant très récente : elle serait contemporaine de la dernière période de réchauffement climatique. Quant à la néogenèse des "chlorites", elle pourrait se poursuivre encore à l'heure actuelle dans certains sites privilégiés de la plate-forme pélagienne.Blanpied Christian, Bellaiche Gilbert. Signification sédimentologique des oolithes calcaires et bioclastes noircis remaniés au Sud-Est de l'île de Djerba. In: Géologie Méditerranéenne. Tome 8, numéro 3, 1981. Pleistocène. pp. 167-172

The Upper Jurassic Stanleyville Group of the eastern Congo Basin: An example of perennial lacustrine system

International audienceThe intracratonic Congo Basin, located in the Democratic Republic of Congo (DRC), is the largest sedimentary basin of Africa. The Jurassic strata outcrop along its eastern margin, south of Kisangani (formerly Stanleyville). In the last century, the Upper Jurassic Stanleyville Group was described as a lacustrine series containing a thin basal marine limestone designed as the ;Lime Fine; beds. Since the proposal of this early model, the depositional environment of the Stanleyville Group, and especially the possible marine incursion, has been debated, but without re-examining the existing cores, outcrop samples and historical fossils from the type location near Kisangani that are available at the Royal Museum for Central Africa (MRAC/KMMA, Tervuren, Belgium). In order to refine the former sedimentology, a series of nine exploration cores drilled in the Kisangani sub-basin have been described. This study aims at integrating sedimentary facies in existing sedimentary models and to discuss the hypothesis of the presence of Kimmeridgian marine deposits along the Congo River near Kisangani, a region which lies in the middle of the African continent. Eight facies have been identified, which permit a reinterpretation of the depositional environment and paleogeography of the Stanleyville Group. The base of the Stanleyville Group is interpreted to represent a conglomeratic fluvial succession, which filled an inherited Triassic paleotopography. Above these conglomerates, a transition to a typically lacustrine system is interpreted, which includes: (1) a basal profundal, sublittoral (brown to dark fine-grained siltstones with microbial carbonates, i.e., the ;Lime Fine; beds) and littoral lacustrine series; covered by (2) a sublittoral to profundal interval (brown to dark organic-rich, fine-grained siltstones), which corresponds to the maximum extent of the paleo-lake; and, finally (3) a shallow lacustrine series (greenish calcareous siltstones and sandstones with red siltstones). Unlike what has been proposed, the ;Lime Fine; beds are interpreted herein to be of lacustrine origin, rather than representing a Kimmeridgian marine transgression. We conclude that a Jurassic marine transgression did not, in fact, occur in the eastern region of the Congo Basin