Characterisation of the organic matter of upper Bedoulian and lower Gargasian strata in the historical stratotypes (Apt and Cassis-la-Bédoule areas, SE France)

International audienceThe Total Organic Carbon (TOC) content of the Gargasian strata studied in their historical stratotype area is rather low (0.3% on average). Only a few levels show TOC values approaching 1.2%. This small amount of preserved organic matter, associated with low hydrogen index values (10 to 115 mg hydrocarbons/g TOC), argues for deposition in fully oxic conditions. This organic content is a mixture of land-derived organic particles and deeply oxidized marine organic matter. The organic flux was strongly diluted by the autochthonous carbonate input

Distribution of the organic matter in the channel-levees systems of the Congo mud-rich deep-sea fan (West Africa). Implication for deep offshore petroleum source rocks and global carbon cycle

International audienceThe Corinth Rift is superimposed on the Hellenic nappe stack that formed at the expense of the Apulian continental crust above the subducting African slab. Extension started in the Pliocene and the major steep normal faults that control the geometry of the present-day rift were born very recently, some 600 kyr ago only. They root into a shallow-dipping zone of microseismicity recorded near the base of the upper crust. The significance of this seismogenic zone is debated. Considering the northward dip of the zone of microseismicity, the depth of microearthquakes and their focal mechanisms, we observe a strong similarity with the northern Cycladic detachments in terms of expected pressure, temperature conditions and kinematics. We herein show (1) that the formation of the Corinth Rift can be considered a part of a continuum of extension that started some 30–35 Ma in the Aegean and that was recently localised in a more restricted area, (2) that the present-day structure and kinematics of the Corinth Rift can be explained with a series of decollements relayed by steeper ramps that altogether formed a mechanically weak, crustal-scale detachment, and (3) that the deformation, fluid behaviour and metamorphic features seen in the northern Cycladic metamorphic core complexes can be good analogues of the processes at work below the Corinth Rift

A GUIDE-LEVEL OF THE UPPERMOST HAUTERIVIAN (LOWER CRETACEOUS) IN THE PELAGIC SUCCESSION OF UMBRIA-MARCHE APENNINES (CENTRAL ITALY): THE FARAONI LEVEL

The definition of a regional guide-level, named Faraoni Level, in the Maiolica limestone of the Umbria-Marche Apennines is proposed in this paper. The age of the Faraoni Level is latest Hauterivian. Abundant ammonites date it as angulicostata zone, catulloi subzone. The level is characterized by the alternation of white micritic limestones and black shales with high organic marrer conrent

Characterization at a local scale of a laser-shock peened aluminum alloy surface

The influence of a laser shock peening mechanical surface treatment on 2050-T8 aluminum alloy has been investigated, mostly using Scanning Kelvin Probe Force Microscopy. Volta potential difference maps around Al(CuFeMn) precipitates were performed before and after laser-shock peening to determine the influence of laser treatment versus galvanic coupling near precipitates, and resulting pit initiations. It has been shown that laser shock peening either preserves or reduces precipitate-matrix Volta potentials gradients, which in this later case, and correlated to recent corrosion electrochemical investigations, could explain corrosion improvement obtained after laser-shock peening treatments of aluminum alloys. The influence of crystal orientation and plastic deformation, and more specifically the effect of laser-induced compressive residual stresses or work-hardening, on the Volta potential values and on the pitting corrosion behavior was also addressed

Caractérisation de la matière organique du Bédoulien supérieur et du Gargasien dans les stratotypes historiques de l'Aptien (régions d'Apt et de Cassis-la Bédoule, SE de la France)

Les teneurs en Carbone Organique Total (COT) des couches gargasiennes étudiées dans leur région stratotypique historique sont faibles (0,3% en moyenne), à l'exception de quelques niveaux où les teneurs atteignent 1,2%. Ces faibles quantités de matière organique préservée, associées à des faibles valeurs de l'index d'hydrogène (10 à 115 mg d'hydrocarbures/g COT), suggèrent un dépôt en conditions oxiques franches. Cette contribution organique au sédiment est un mélange de particules d'origine terrestre et d'une biomasse marine fortement oxydée. Ces maigres apports organiques étaient fortement dilués par les flux de carbonate biogène autochtone.The Total Organic Carbon (TOC) content of the Gargasian strata studied in their historical stratotype area is rather low (0.3% on average). Only a few levels show TOC values approaching 1.2%. This small amount of preserved organic matter, associated with low hydrogen index values (10 to 115 mg hydrocarbons/g TOC), argues for deposition in fully oxic conditions. This organic content is a mixture of land-derived organic particles and deeply oxidized marine organic matter. The organic flux was strongly diluted by the autochthonous carbonate input

On the recrystallization and texture of Fe-36%Ni alloy after accumulative roll bonding and annealing at 600 °C

Microstructure and texture evolution of Fe-36%Ni (wt.%) alloy after 1, 5 and 10 accumulative roll-bonding (ARB) cycles and annealing at 600 °C up to 3600 seconds were studied using electron backscatter diffraction. Microstructural and textural changes after ARB and annealing were compared to those existing in the literature after conventional rolling. The microstructure was not stable at 600 °C for all ARB samples even after 3600 seconds of annealing. The recrystallization texture was dominated by the Cube {001} texture component. Recrystallization kinetics were determined using microhardness measurement and were close to those after cold rolling with Avrami time exponent around unity. The texture evolution at high strain was discussed in terms of grain boundary migration obstruction by the formation of layer interfaces and small recrystallized grains near the bonded interfaces

The Oxfordian–Kimmeridgian transition in the Boulonnais (France) and the onset of organic-rich marine deposits in NW Europe: a climatic control?

International audienceWe characterised the organic matter content of marine deposits at the Oxfordian–Kimmeridgian transition in the Boulonnais (France). Organic rich deposits in platform environments are evidenced in the uppermost Cymodoce and lowermost Mutabilis Zone (early late Kimmeridgian), associated with enhanced planktonic palaeoproductivity and/or developing dysoxia/anoxia. Similar organic rich intervals in early late Kimmeridgian are also evidenced in platformdeposits in Normandy and Charentes in France, and in basinal deposits from Yorkshire and Dorset in UK. This refined onsetof the organic rich bands (ORB), as described in NW Europe during the late Jurassic, is coeval with seawater warming. We propose that this seawater warming was an important trigger of the onset of the late Jurassic ORB deposition system in NW Europe, which began at the Cymodoce–Mutabilis boundary during the early late Kimmeridgian and lasted until the middle part of the Tithonian, over a time span of 6.8Myr