Search results for "Tectonics"
showing 10 items of 385 documents
A complex thrust sequence in western Himalaya: the active Medlicott Wadia Thrust.
2017
15 pages; International audience; The recent activity of the Medlicott-Wadia Thrust (MWT) is investigated by geomorphic and tectonic studies in the Riasi zone, south of the Pir Panjal range (India, Jammu-Kasmir state of western Himalaya). In the Riasi area, the MWT forms a splay of five faults that dip northward. The recent activity of the splay is quantified using a set of deformed Quaternary alluvial units. The central branch of the thrust splay moved Precambrian limestones above Quaternary sediments and is sealed by 36 ± 3 ka (youngest OSL age) deposits. The other branches offset the top of a 15 ± 1 ka (youngest OSL age) alluvial fan by 180 to 120 m; the two southernmost branches form 17…
Permian-Triassic Rifting Stage
2019
International audience; The Permian-Triassic rifting represents the first of the two Mesozoic rifting stages recorded in the Iberian Peninsula. Its first phases of development started during the Early Permian, and were linked to the beginning of the break-up of Pangea, the large, unique and rheologically unstable supercontinent that mainly resulted from the collision of Gondwana and Laurussia. This chapter analyzes this first rifting stage in Iberia in two separate phases, an initial or tectonic phase, and a later mature phase. This analysis focuses on the main Permian-Triassic basins of the Iberian Peninsula: the Pyrenean, Iberian, Catalan, Ebro and Betic basins, as well as the basins loca…
Calculating the long-term displacement rates of a normal fault from the high-resolution stratigraphic record (early Tethyan rifting, French Alps)
2003
Displacement rates of normal faults deduced from stratigraphic data are often unreliable. Here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a highresolution time-frame established by biostratigraphy and physical stratigraphy. Our example is the Ornon normal fault bounding the Early Jurassic Bourg-d’Oisans Basin formed during Tethyan rifting. We show that motion on the fault was discontinuous when examined at high resolution and over a long time interval. During a first interval (Hettangian to Sinemurian Arietites bucklandi zone) a low rate of displacement (= 202–423 m Myr -1 ) coeval with diffused exte…
Synthèse préliminaire des travaux menés sur le bassin de Benguela (Sud Angola) : implications sédimentologiques, paléontologiques et structurales.
2006
12 pages; International audience; Les travaux menés dans le bassin de Benguela ont apporté une moisson de nouvelles données de terrain quant à la période apto-albienne de ce secteur ouest africain. Outre les résultats majeurs obtenus en ce qui concerne les faunes d'ammonites jusqu'alors peu étudiées dans ce bassin, et qui ont permis des corrélations indispensables pour la compréhension du fonctionnement de la sédimentation, cette étude a permis de mettre en évidence une compartimentation remarquable de la sédimentation et des structures de tectonique salifère. Des tels résultats ont une portée à la fois fondamentale et appliquée. En effet, il paraît que le bassin de Benguela soit un des rar…
The role of slabs and oceanic plate geometry in the net rotation of the lithosphere, trench motions, and slab return flow
2012
International audience; [1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. F…
Tectonics and seismicity of the Tindari Fault System, southern Italy: Crustal deformations at the transition between ongoing contractional and extens…
2006
The Tindari Fault System (southern Tyrrhenian Sea, Italy) is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab. Onshore structural data, an offshore seismic reflection profile, and earthquake data are analyzed to constrain the present geometry of the Tindari Fault System and its tectonic evolution since Neogene, including the present seismicity. Results show that this zone of deformation consists of a broad NNW trending system of faults including sets of right-lateral, left-lateral, and extensional faults as well as early strike-slip faults reworked …
A Low Cost Customizable Micro-ROV for Environmental Research - Applications, Advances and Challenges
2016
Summary Several shallow submarines areas are characterized by considerable releases of hydrocarbon gases, which, during earthquakes or volcanic activity, may suddenly and violently occur. In some instances, changes in chemical and physical properties of gas emissions, which are generated by geothermal systems connected to the volcanoes’ plumbing system, are important precursors of volcanic activity and useful indices for the study of the geothermal field. Furthermore, some superficial structures such faults, landslide slopes or archaeological relics should be studied with such a high detail that geophysical and bathymetric surveys are unable to provide. In response to the needs increasingly…
Coseismic extension recorded within the damage zone of the Vado di Ferruccio Thrust Fault, Central Apennines, Italy
2018
Recent high resolution hypocentral localisation along active fault systems in the Central Apennines illuminates the activation of seismogenic volumes dipping at low angle (<30°) in extensional settings overprinting contractional deformations affecting the continental crust of the Adria microplate. Individuation of the geological structures and of the fault processes associated with these seismic patterns will contribute to the interpretation of seismic sequence evolution, and seismic hazard studies.Here we report field and microstructural evidence of seismogenic extensional faults localized within pre-existing thrust fault zones. The Vado di Ferruccio Thrust Fault (VFTF) is a narrow …
Middle Miocene–Early Pliocene wedge-top basins of NW Sicily (Italy): constraints for the tectonic evolution of a ‘non-conventional’ thrust belt, affe…
2014
The study of geological evolution of a multiphase orogenic belt is complex, expecially when the tectonic events are superimposed in a coaxial fashion. The Sicilian fold-and-thrust belt represents an interest- ing case study, as a non-coaxial superimposition of structures is recognizable, owing to large synkinematic clockwise rotations during each of two subsequent compressional events. These rotations involved also the syntectonic basins that developed in the wedge-top depozone. This study aims to constrain the tectono-depo- sitional evolution of the NW Sicily fold-and-thrust belt and the associated wedge-top depozone between the middle Miocene and the early Pliocene. Integrated analyses of…
Natural Laboratories for Field Observation About Genesis and Landscape Effects of Palaeo-Earthquakes: a Proposal for the Rocca Busambra and Monte Bar…
2018
Earthquakes are phenomena that are still being learned by the scientific community, and poorly known, especially as regards the prevention, by the population. Having a more complete knowledge is a basic step in understanding the vastness and intensity of the destructive phenomenon that involves a great amount of people. The recent earthquakes occurred in Central Italy (L’Aquila and Amatrice earthquakes) are examples that demonstrate the importance of having knowledge about these phenomena to contrast their destructive effects. We present a geological field trip to recognise causes and landscape effects of palaeo-earthquakes recorded in the Mesozoic rock successions outcropping in Sicily. Th…