Palaeomagnetism of the Ordovician dolerites of the Crozon Peninsula (France)

In order to obtain a Lower Palaeozoic pole for the Armorican Massif and to test the origin of the Ibero-Armorican arc, the Ordovician dolerites of the Crozon peninsula have been palaeomagnetically studied. The samples show a multicomponent magnetization which has been revealed by AF and thermal demagnetization and thoroughly investigated with rock magnetic experiments, polished section examinations and K/Ar dating. Four groups of directions have been recognized, often superimposed on each other in an individual sample. One component (D) has always the lowest blocking temperatures and coercivities and is considered to be of viscous origin, acquired recently in situ or in the laboratory during storage. Two components (A and B) are interpreted to be of secondary origin and to correspond to the observed K/Ar age distribution between 300 and 190 Myr. These ages represent the time interval between two regional thermo-tectonic events, associated with the Hercynian orogeny and the intrusion of dykes related to the early opening of the Central Atlantic Ocean and the Bay of Biscay. A fourth component (C) could be of Ordovician or younger Palaeozoic age; it is not clear whether the age of the magnetization is pre- or post-folding, but a pre-folding age would yield a direction of magnetization similar to Ordovician results from the Iberian peninsula. The latter interpretation suggests a fairly high palaeolatitude, which is in agreement with a glacio-marine postulated for sediments overlying the dolerite sills.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73214/1/j.1365-246X.1983.tb03785.x.pd

Geosphere-Biosphere coupling processes: the TTR interdisciplinary approach towards studies of the European and North African margins, International conference and Post-Cruise meeting of the Training-Through-Research programme, Marrakech, Morocco, 2-5 February 2005

The annual international post-cruise meeting and research Conference on ‘Geosphere-BiosphereCoupling Processes: the TTR interdisciplinary approach towards studies of the European and NorthAfrican margins’ was organized by the Intergovernmental Oceanographic Commission (IOC) ofUNESCO and its Training-through-Research (TTR) programme together with the Geosphere-BiosphereCoupling Processes Consortium of the universities and research institutions of Morocco (GBCPMorocco)and Ghent University (Belgium). It considered the results of the TTR14 (2004) cruise to theGulf of Cadiz and the Mediterranean Sea, results of some other TTR cruises carried out at the Europeanand North Atlantic margins and in the Central Atlantic, and other national and international projectsrelevant to subjects of the TTR research. The Conference had dual but complementary tasks: to discussthe most recent achievements in interdisciplinary research mostly on ocean margins and to providestudents, including Ph.D. students, with a forum to present and discuss their research results. It had yetanother target: to contribute in a wider sense to capacity building in countries of the South.The Conference took place in Marrakech, Morocco (2-5 February 2005). The meeting brought togethernearly 70 participants from sixteen countries: Belgium, France, Germany, Greece, Ireland, Italy,Morocco, the Netherlands, Norway, Portugal, Russia, Saudi Arabia, Senegal, Spain, Switzerland andthe United Kingdom. Attending were researchers and students with different specialties (geology,sedimentology, geophysics, geochemistry, microbiology, biology, etc.) and research interests falling inthe area of the conference themes. In total 37 oral and nine poster presentations were made groupedaround several themes like mud volcanoes, fluid venting, carbonate mounds, slope processes,geohazards etc

The basic magmatism in the Famennian-Dinantian Sidi Bettache Basin (Northwest Hercynian Morocco): new facts

Commonly is held up that the Sidi Bettache Basin corresponds to the collapse of a large block of the middle Devonian carbonate platform with subsequent magmatic injections emplacement along its boundaries. Previous studies of one of us (A.L.) and those in progress show instead that this magmatism is primarily controlled by distensional activity of NNW-SSE to NW-SE faults before Middle Visean time. These faults affect throughout the 60 km wide western part of the basin which is also characterized by its Famennian-Lower Visean sedimentary evolution and by a complex variscan polyphasic structuratio

Distribution of benthic foraminifera in semi-arid climates: Nador (Morocco) and El Meleh (Tunisia) lagoons

This paper effectuates a preliminary analysis of the foraminiferal distribution in two coastal lagoons of northern Africa: Nador (Morocco) and El Meleh (Tunisia). In Nador lagoon, the highest richness of species was found in the inner margin of the lagoon, with frequent specimens of Ammonia and Quinqueloculina. A single species (Nonion depressulum Walker & Jacob) was collected near an old iron mine, whereas low densities and diversities were observed near the artificial mouth. In El Meleh lagoon, high number of both individuals and species characterize the marine connection. In the remaining zones, these microorganisms are very scarce (mainly Ammonia spp.), especially near the treatment station of the Slimene tow

Cold-water coral mounds on the Pen Duick Escarpment, Gulf of Cadiz: the MiCROSYSTEMS approach

Here we present a case study of three cold-water coral mounds in a juvenile growth stage on top of the Pen Duick Escarpment in the Gulf of Cadiz; Alpha, Beta and Gamma mounds. Although cold-water corals are a common feature on the adjacent cliffs, mud volcanoes and open slope, no actual living cold-water coral has been observed. This multidisciplinary and integrated study comprises geophysical, sedimentological and (bio)geochemical data and aims to present a holistic view on the interaction of both environmental and geological drivers in cold-water coral mound development in the Gulf of Cadiz. Coring data evidences (past or present) methane seepage near the Pen Duick Escarpment. Several sources and pathways are proposed, among which a stratigraphic migration through uplifted Miocene series underneath the escarpment. The dominant morphology of the escarpment has influenced the local hydrodynamics within the course of the Pliocene, as documented by the emplacement of a sediment drift. Predominantly during post-Middle Pleistocene glacial episodes, favourable conditions were present for mound growth. An additional advantage for mound formation near the top of Pen Duick Escarpment is presented by seepage-related carbonate crusts which might have offered a suitable substrate for coral settling. The spatially and temporally variable character and burial stage of the observed open reef frameworks, formed by cold-water coral rubble, provides a possible model for the transition from cold-water coral reef patches towards juvenile mound. These rubble “graveyards” not only act as sediment trap but also as micro-habitat for a wide range of organisms. The presence of a fluctuating Sulphate–Methane Transition Zone has an important effect on early diagenetic processes, affecting both geochemical and physical characteristics, transforming the buried reef into a solid mound. Nevertheless, the responsible seepage fluxes seem to be locally variable. As such, the origin and evolution of the cold-water coral mounds on top of the Pen Duick Escarpment is, probably more than any other NE Atlantic cold-water coral mound province, located on the crossroads of environmental (hydrodynamic) and geological (seepage) pathways