The colloidal structure of bitumen: Consequences on the rheology and on the mechanisms of bitumen modification

Geological atlas of western and central Europe

Evolution of the European Cenozoic Rift System: interaction of the Alpine and Pyrenean orogens with their foreland lithosphere

The circum-Mediterranean anorogenic Cenozoic igneous province

More than 100 offshore mass-movement deposits have been studied in Holocene and Pleistocene sediments. The processes can be divided into three main types: slides/slumps, plastic flows, and turbidity currents, of which 13 main varieties have been recognized. The three types are differentiated mainly by motion, architecture, and shape of failure surface. For slides, the morphology of deposits can usually be linked to a process, but for plastic flows and turbidity currents, information about the motion is mainly provided by the sedimentary record. A static classification based on these features is given, and is related to a dynamic classification system to try to underline the morphological transformation of an offshore event from initiation to deposition.

Classification of offshore mass movements

https://hal.archives-ouvertes.fr/hal-00450273/document

How summit calderas collapse on basaltic volcanoes: New insights from the April 2007 caldera collapse of Piton de la Fournaise volcano

We report the discovery of a detachment fault within reach of structural investigation in a shield volcano (Piton des Neiges, La Reunion hotspot). The detachment, exposed by erosion, is located between the top of an extinct gabbroic magma chamber and a cover of debris avalanche deposits. The fault simultaneously concentrated ductile and brittle deformation toward the sea, hydrothermal alteration in the greenschist facies, and repeated sill injections of basic magmas. Our study of this exceptional detachment exposure suggests that two mechanisms participate in volcano flank failure: hydrothermal alteration, likely sustained by the heat of cooling sills, induces slow inter-intrusion deformation, whereas sill injections in the fault may trigger rapid cointrusive slip. This twofold process of destabilization might currently occur on some active volcanoes such as Piton de la Fournaise.

Volcano destabilization by magma injections in a detachment

The topography of Piton de la Fournaise volcano (PdF) differs from the classic view of basaltic shield volcanoes as it is characterized by (1) several steep slope zones on its flanks and (2) a large U-shaped caldera, the Enclos-Grand Brule structure (EGBS). Most of these structures were previously interpreted as the scars of lateral landslides, the deposits of which cover the submarine flanks of PdF. We carried out a detailed analysis of the morphology of PdF, which reveals that the steep slope zones form two independent, circumferential structures that continue into the caldera. The development of circumferential steep slopes on volcano flanks may have several origins: constructive, destructive, and deformation processes. We interpret those processes acting on PdF as caused by the spreading of the volcanic edifice above a weak hydrothermal core, leading to outward displacements and a summit extensive stress field. The continuity of the steep slope on both sides of the EGBS escarpments suggests that this structure was not caused by a 4.5 ka old giant landslide as it is usually proposed but is due to a mainly vertical collapse. The recent debris avalanche deposits east of the island indicate that this event likely destabilized part of the submarine flank. We propose that the collapse of the Grand Brule, the lower half of the EGBS, was due to the downward drag related to the dense intrusive complex of the Alizes volcano, which is located 1 km below the Grand Brule. The collapse of the Enclos is interpreted as the consequence of the deformation of the hydrothermal system of the pre-Enclos volcano. Although the continuity of the geological and morphological structures between the Enclos and the Grand Brule suggests a narrow link between these two collapse events, their chronology and relationship are still uncertain. Finally, we hypothesize that the persistence of the NE and SE rift zones during the last 150 ka, despite the large changes of the topography related to the recurrent flank destabilizations, is linked to a deep sources, which can be either underlying crustal faults or the continuous downward subsidence of the Alizes intrusive complex.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JB004118

Morphology of Piton de la Fournaise basaltic shield volcano (La Réunion Island): Characterization and implication in the volcano evolution

The amorphous and crystalline phases in asphalt have been identified and studied using low-temperature solid-state carbon-13 CP/MAS NMR and DSC techniques. The NMR mass percent of the crystalline methylene carbons was shown to correlate linearly with the mass percent of crystalline wax in asphalts measured using DSC. While the internal methylene carbon content of long-chain alkanes in the crystalline phase in the asphalts varied, the internal methylene carbon content of the long-chain alkanes in the amorphous phase remained relatively constant. The NMR crystalline methylene carbon content was plotted against a low-temperature cracking parameter, the fracture temperature of an asphalt. It was found that 1% or less of aliphatic carbons in the crystalline phase has little effect on the fracture temperature. For these asphalts, the fracture temperature depends mainly on the initial amount of mobile aliphatic carbons in the amorphous phase at 23 °C. For asphalts containing 1% or more of crystalline aliphatic c...

Laurent Michon

Papers

How summit calderas collapse on basaltic volcanoes: New insights from the April 2007 caldera collapse of Piton de la Fournaise volcano

Volcano destabilization by magma injections in a detachment

Morphology of Piton de la Fournaise basaltic shield volcano (La Réunion Island): Characterization and implication in the volcano evolution

A 13C NMR and DSC study of the amorphous and crystalline phases in asphalts

Estimation of average structural parameters of bitumens by 13C nuclear magnetic resonance spectroscopy