Search results for "Accretionary wedge"
showing 10 items of 17 documents
Structural contacts in subduction complexes and their tectonic significance: the Late Palaeozoic coastal accretionary wedge of central Chile
2007
Understanding the contact between the very low-grade metagreywacke of the Eastern Series and high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show the progressive development of structures and finite strain from the least deformed rocks in the eastern part of the Eastern Series of the accretionary wedge to high-pressure schist of the Western Series at the Pacific coast. Upright chevron folds of sedimentary layering are associated with an axial-plane foliation, S1. As the F1 folds became slightly overturned to the west, S1 was folded abou…
Tectonic evolution of the Sicilian Thrust System (central Mediterranean)
2012
The Sicilian Thrust System (STS) is a south-verging (Africa-verging) fold-and-thrust belt including a Mesozoic-Paleogene sedimentary sequence. This thrust stack owes its origin to the deformation of pre-orogenic strata deposited in different palaeogeographic domains belonging to passive margins of the African plate. The STS was deformed during the Neogene, following the closure of the Tethys Ocean and the continental collision between the Sardo-Corso Block and the North Africa margins. The thrust pile was detached from the underlying basement during the Miocene-Pleistocene. The regional-scale structural setting recognized allows us to reconstruct the tectonic evolution of the STS as follows…
Tectonic history of the submerged Maghrebian Chain from the Southern Tyrrhenian Sea to the Pelagian Foreland
1995
A description is given here of the structure and tectonic evolution of the submerged NW-SE trending Alpine belt extending from the Sardinia Channel across the Sicily Straits to the Pelagian Sea. This mainly results from re-interpretation of the existing seismic network. In the Sicily Straits the crust comprises an allocthonous belt composed of Tertiary flysch-type thrust slices stacked in an imbricate wedge. The wedge is composed of Mesozoic basin and platform carbonates thrusts derived by deformation of the old Sicilian continental margin. Lower Miocene to Lower Pleistocene foredeep deposits (terrigenous and clastic carbonates) filled progressively onlapping foreland basins during regional…
Carbonate/evaporitic sedimentation during the Messinian salinity crisis in active accretionary wedge basins of the northern Calabria, southern Italy
2020
Abstract This work deals with Messinian deposits belonging to the Neogene infill of the Rossano and Belvedere Basins, respectively developed along the fore-arc and the back-arc areas of the north Calabria accretionary wedge. The main goal is to characterize the carbonate and evaporitic sedimentation during the Messinian Salinity Crisis, in the general framework of the basin architecture and the interplay between eustatic vs tectonic controlled sea-level variations. Fieldwork integrated with seismic lines and well logs interpretations led to the revision of the general stratigraphy of the basins and the proposal of a new sequential stratigraphic model driven by cyclic sea-level variations. E…
Accretionary orogens through Earth history
2009
Accretionary orogens form at intraoceanic and continental margin convergent plate boundaries. They include the supra-subduction zone forearc, magmatic arc and back-arc components. Accretionary orogens can be grouped into retreating and advancing types, based on their kinematic framework and resulting geological character. Retreating orogens (e.g. modern western Pacific) are undergoing long-term extension in response to the site of subduction of the lower plate retreating with respect to the overriding plate and are characterized by back-arc basins. Advancing orogens (e.g. Andes) develop in an environment in which the overriding plate is advancing towards the downgoing plate, resulting in th…
Geochemical signature of Paleozoic accretionary complexes of the Central Asian Orogenic Belt in South Mongolia: Constraints on arc environments and c…
2006
Abstract We report a reconnaissance geochemical and Nd-isotopic study for 33 metaigneous and metavolcaniclastic rocks from the ca. 470 to 290 Ma old Gurvan Sayhan, Zoolen, Nemegt Uul, Bayanleg-Hatuu, and Tseel mountain ranges in southern Mongolia, in order to infer tectonic environments, test a recently proposed multiple terrane model, and explore the late-stage development of the southern Central Asian Orogenic Belt (CAOB). Samples from the Gurvan Sayhan and the Zoolen ranges have a predominantly intermediate, calc-alkaline composition; they display LREE enrichment, excess abundances of fluid-soluble elements, and low concentrations of high-field strength elements. These data, in combinati…
The Western Alps from the Jurassic to Oligocene: spatio-temporal constraints and evolutionary reconstructions
2005
Abstract Despite extensive research in the last 150 years, the regional tectonic reconstruction of the Western Alps has remained controversial. The curved orogenic belt consists of several ribbon-like continental terranes (Sesia/Austroalpine, Internal Crystalline Massifs, Brianconnais), which are separated by two or more ophiolitic sutures (Piemonte, Valais, Antrona?, Lanzo/Canavese?). High-pressure (HP) metamorphism of each terrane occurred during distinct orogenic episodes: at ∼65 Ma in the Sesia/Austroalpine, at ∼45 Ma in the Piemonte zone and at ∼35 Ma in the Internal Crystalline Massifs. It is suggested that these events reflect individual accretionary episodes, which together with kin…
Timing of deformational events in the Río San Juan complex: implications for the tectonic controls on the exhumation of high-P rocks in the northern …
2013
An integrated structural, petrological and geochronological study was undertaken to constrain the tectonic history and controls on the exhumation of the high-P rocks of the Río San Juan complex in the northern Caribbean subduction–accretionary wedge. In the main structural units of the complex, microtextural analyses were performed to identify the fabrics formed at peak ofmetamorphismin eclogite-facies conditions and during the main retrogressive event toward the low-P amphibolite or blueschist/greenschist-facies conditions. U–Pb SHRIMP dating on zircon rims (71.3 ± 0.7 Ma) coupled with 40Ar–39Ar analyses on phengite (~70– 69 Ma) in felsic sills placed temporal constraints on the exhumation…
The role of trapped fluids during the development and deformation of a carbonate/shale intra-wedge tectonic mélange (Mt. Massico, Southern Apennines,…
2020
Abstract Numerous studies exist on exhumed tectonic melanges along subduction channels whereas, in accretionary wedge interiors, deformation mechanisms and related fluid circulation in tectonic melanges are still underexplored. We combine structural and microstructural observations with geochemical (stable and clumped isotopes and isotope composition of noble gases in fluid inclusions of calcite veins) and U-Pb geochronological data to define deformation mechanisms and syn-tectonic fluid circulation within the Mt. Massico intra-wedge tectonic melange, located in the inner part of the central-southern Apennines accretionary wedge, Italy. This melange developed by shear deformation at the bas…
Normal faulting at convergent plate boundaries: Mylonitic extensional fabrics in the Franciscan subduction complex in Del Puerto Canyon, California, …
2004
[1] Using a strain and rotation analysis we tested the hypotheses that top-east mylonitic extensional structures in the uppermost Franciscan subduction complex in Del Puerto Canyon, California, accomplished exhumation of the Franciscan blueschists. We found no evidence of strongly noncoaxial deformation, instead our data indicate overall coaxial deformation in the proposed zone of mylonitic extensional deformation. There are no extensional strains, moderate vertical shortening occurred without horizontal extension and was compensated by modest deformation-related volume loss. There is also no strain gradient toward and within the proposed shear zone. Therefore the results of our work indica…