Occurrence of photosynthetic microbial mats in a Lower Cretaceous black shale (central Italy): a shallow-water deposit

Cretaceous oceanic anoxic events (OAEs) were periods of high organic carbon burial corresponding to intervals with excellent organic matter (OM) preservation. This work focuses on the Urbino level, i.e., OAE1b, which is thought to be of regional extent. A detailed microscopical study of OM shows a dominance of microbial activity, characterized by a typical arrangement of exopolymeric substances (EPS) related to microbial mats, bacterial bodies, and some photosynthetic microorganisms, as shown by thylakoids. The latter lived where they have been found, i.e., at the sea bottom, which indicates that OM results from the diagenesis of benthic photosynthetic microbial mats, an interpretation supported through the comparison with a recent analogue. The exceptional preservation of such organic structures in OM points to the joint role of the selective and sorptive preservation pathways. These data and interpretation strongly differ from previous observations in OAE1b equivalents. They suggest that the Urbino level might be an atypical OAE of regional/local extent which was formed within the photic zon

An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean

The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with 187Os/188Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism

Stress Processes: An Essential Ingredient in the Entrepreneurial Process

The entrepreneurial process is associated with high uncertainty. Uncertainty is also a major source of stress. Therefore, a core aim of entrepreneurs is to reduce uncertainty to an extent that allows the entrepreneurial process to unfold. However, entrepreneurship scholars have insufficiently addressed stress processes that may be associated with this uncertainty. We argue that uncertainty is the concept connecting both the entrepreneurial and stress processes. We discuss the link between the two processes regarding: (1) opportunity recognition, (2) opportunity exploitation, and (3) associated outcomes. We then illustrate how future research should incorporate the interaction between the two processes using a morphological box and discuss how such research would change the way we specify entrepreneurial process models and study entrepreneurial behavior

3D Reactive Transport simulations of Uranium In Situ Leaching : Forecast and Process Optimization

International audience3D reactive transport model is an efficient tool to simulate ISR operation: indeed the whole process is based on reacting fluid circulation in porous media. The simulation can help quantify the processes at stake, and optimize the ore dissolution rate and the use of reagents. It can also be used to test the efficiency of alternative well patterns or to refine well screens vertical position within the ore body.The model relies on an appropriate description of uranium bearing aquifer. 3D geologic block models based on geological observations and geostatistical reconstruction were used. They describe the spatial distribution of both hydrodynamic and geochemical units (including uranium and other mineral concentrations). Also, a correct assessment of the chemical reactions (thermodynamic and kinetics) at stake is necessary.This study details the application of a 3D reactive transport approach (using the code HYTEC) at operation scale in Kazakhstan (technological blocks, approx. 70 wells each). Among other simulation results available, it has been shown that the evolution of the uranium concentration in the production wells and the acid consumption can be accurately forecasted. Moreover, various scenarios of operational optimization, mainly dedicated to well patterns and wells screen localization refinement, were simulated. The results assess the interest of using 3D reactive transport modelling tool for such optimization purposes

Revisiting amorphous organic matter in Kimmeridgian laminites: what is the role vulcanization process in the amorphization of organic matter ?

International audienc

Unravelling the origin of ultralaminae in sedimentary organic matter: the contribution of bacteria and photosynthetic organism

International audienc

Reactive transport simulation of Uranium ISL at the block scale: a tool for testing designs and operation scenarios

International audienceThis study details the development of a tool simulating in the 3D fluid flow as well as the coupled physical and chemical processes in an ISL production block. The model relies on an appropriate description of uranium bearing aquifer: 3D geologic model, geostatistical simulation of hydrodynamic parameters, the uranium and other mineral concentrations. Also, a correct assessment of the chemical reactions at stake is necessary. It is then possible to simulate the ISL operations with a reactive transport approach (code HYTEC). Among other simulation results available, the evolution of the uranium concentration at production wells can be predicted. The model was applied at a technological block scale (75 technical wells). The simulations allow to reproduce the behaviour in terms of uranium recovery and to test scenarios of production for optimization purposes

Unravelling the origin of ultralaminae in sedimentary organic matter: the contribution of bacteria and photosynthetic organism

International audienc