Search results for "Transtension."
showing 6 items of 6 documents
Geochemistry, tectonic setting and geodynamic significance of late orogenic dikes in the Melibocus Massif, Bergsträsser Odenwald
2001
The Melibocus Massif forms a tonalite pluton in the W’ Bergstrasser Odenwald, which is interpreted as part of a magmatic arc of Devonian to Carboniferous age. Dikes of various compositions intrude frequently this tonalite. Different dike-lithologies are associated with different strike directions. Most dikes show evidence of high-temperature shearing. A probable maximum paleostress direction of ca. 060° can be estimated, i.e. nearly parallel to the known Variscan subduction zone in the Northwest. Due to their ductile deformation under conditions around the Ar-closing temperature of amphibole, intrusion likely occurred during the Carboniferous (Mississippian). The gabbroic to dioritic dikes …
Active deformation in Southern Italy, Sicily and southern Sardinia from GPS velocities of the Peri-Tyrrhenian Geodetic Array (PTGA)
2008
Campaign measurement (1995-2000) of Global Positioning System (GPS) site velocities in southern Italy, Central Mediterranean area, document differential displacements within the orogens rimming the Tyrrhenian Sea. Within the Southern Apennines, GPS velocities define two laterally juxtaposed belts of deformation, with transpression in the east and transtension in the west. In the east, ~8 mm/yr convergence between northern Murge-Gargano block and the International GPS System (IGS) site MATE is partitioned across ~east-west striking right-lateral faults, consistent with seismicity and with the offshore geological record. To the south, in northern Calabria, site velocities relative to MATE ind…
STRUCTURATION EXTENSIVE ET TRANSTENSIVE AU DEVONO-DINANTIEN DU BASSIN DE TIM MERSOÏ (BORDURE OCCIDENTALE DE L'AÏR, NORD NIGER).
2007
International audience; L'étude tectono-sédimentaire préliminaire du bassin de Tim Mersoï confirme le contrôle exercé par les accidents majeurs N-S d'In Azaoua-Arlit, N30°E de Madaouéla et N70°E de Tin Adrar sur la géométrie du remplissage sédimentaire. Pour la période dévono-dinantienne, deux phases majeures de structuration ont été mises en évidence : une phase extensive, multi-épisode (du Dévonien au Viséen supérieur) et une phase transtensive débutant au Viséen terminal. Ces deux phases tectoniques majeures sont responsables de l'ouverture polyphasée du bassin. Pendant la phase extensive, la direction d'allongement qui était globalement N90°E au Dévonien, devient successivement N70°E pu…
Intrusion within a transtensional tectonic domain: the Čistá granodiorite (Bohemian Massif)—structure and rheological modelling
2000
Abstract The Cista granodiorite stock, which intrudes the Tis granite laccolith, and their Neoproterozoic country rocks of the Tepla–Barrandian zone were studied by means of structural analysis and anisotropy of magnetic susceptibility. The rocks were dated by the Pb–Pb evaporation on zircons, determining the age of the Cista granodiorite and Tis granite at 373 Ma and 504 Ma, respectively. The structures in the country rocks are characterised by an axial cleavage dipping to the northwest and overprinting the folded bedding. S1 cleavage bears NE–SW-trending mineral lineations, which plunge to the northeast or southwest at shallow angles. The cleavage is deformed by D2 kink-bands, which indic…
Normal vs. strike-slip faulting during rift development in East Africa: The Malawi rift
1992
Kinematic analysis of Neogene and Quaternary faults demonstrates that the direction of extension in the Malawi rift rotated from east-northeast to southeast. Rift development commenced with the formation of half-grabens bounded by northwest-, north-, and northeast-striking normal faults. Owing to slightly oblique rifting, the northwest-striking faults in the northernmost rift segment show a small dextral oblique-slip component, whereas north- and northeast-oriented faults in the central part of the rift display a sinistral oblique-slip component. This first event resulted in block faulting and basin subsidence, which is largely responsible for the present-day basin morphology of Lake Malawi…
Cretaceous tectonic evolution of the Sava-Klepa Massif, Republic of North Macedonia – Results from calcite twin based automated paleostress analysis
2019
Abstract The Sava-Klepa Massif represents an approximately 5 × 2 km sized fault-bounded block of dominantly basaltic rocks located within the Sava-Zone, an important suture zone between the Eurasian (Europe) and Gondwana (Adria) continental plates in the Balkans. Its nature and tectonic evolution is controversial: It is either interpreted as a remnant of the youngest Tethyan oceanic realm left behind after the main closure in the Late Jurassic or as the delimiter of a diffuse tectonic boundary between Adria and Europe, which had already collided in the Late Jurassic and was dominantly controlled by transtensional tectonics during Cretaceous times. In order to strengthen one or the other mod…