Search results for "continental margin"

Crust–mantle transition and Moho model for Iceland and surroundings from seismic, topography, and gravity data

2005

An increasing data set exists on the nature and thickness of the Iceland crust. This paper relates topography, i.e., elevation and bathymetry (TOP), Bouguer gravity anomalies (BA) and Moho depths to each other to assess the consequences of the “thick crust model” for Iceland in the context of the North Atlantic. Results of regression of TOP and BA vs. Moho depth are converted into “Airy densities” Δρ* (mantle crust density contrasts in the case of ideal Airy isostasy). For Iceland, Δρ* is very low (105±10 kg/m3); for the adjacent continental margins and relicts, it is high and intermediate for the Jan Mayen Ridge. The values are affected by lithosphere cooling and systematic variations of i…

The oldest rocks of Greece: first evidence for a Precambrian terrane within the Pelagonian Zone

2005

The Pelagonian Zone in Greece represents the westernmost belt of the Hellenide hinterland (Internal Hellenides). Previous geochronological studies of basement rocks from the Pelagonian Zone have systematically yielded Permo-Carboniferous ages. In this study we demonstrate, for the first time, the existence of a Precambrian crustal unit within the crystalline basement of the Pelagonian Zone. The U–Pb single-zircon and SHRIMP ages of these orthogneisses vary from 699 ± 7 Ma to 713 ± 18 Ma, which identify them as the oldest rocks in Greece. These Late Proterozoic rocks, which today occupy an area of c. 20 × 100 km, are significantly different from the neighbouring rocks of the Pelagonian Zone.…

Zircon isotopic ages from magnetite quartzites of the Jianping metamorphic complex, western Liaoning Province

2000

Using the zircon Pb evaporation method and high precise ion microprobe analyses, zircon isotopic ages in supracrustal magnetite quartzites from Jianping metamorphic complex have been obtained. The results show that the deposition of the supracrustal rocks occurred around 2 552–2 520 Ma and the peak of granulite facies metamorphism reached at about 2 487 Ma; about (1 806±16) Ma, i.e. Mid-Proterozoic, the other possible metamorphic event with relatively low intensity happened in the study area. It is speculated that a likely tectonic setting where the Jianping metamorphic complex formed is an active continental margin that is involved in continental collision and crustal thickening shortly af…

On the formation of laminated sediments on the continental margin off Pakistan – reply to the comment by von Rad et al.

2002

Marqueurs d'une structuration extensive jurassique en arrière de la marge nord-téthysienne (monts du Mâconnais, Bourgogne, France)

2000

Structural analysis of extensional faults in the Mâconnais Hills shows that low-intensity extensional phenomena occurred back from the passive margin of the Ligurian Tethys, the axis of which lay some 400 km southeast of the study area in Mid-Jurassic times. Storm-induced rip current directions and coral lens positions suggest that the palaeotopography was maintained by early faulting.

Formation of Hercynian subplates, possible causes and consequences

1976

WITH the exception of the microplate models of Badham and Halls1 and Riding2 models of Hercynian plate tectonics3–7 have assumed the existence of only one plate, that is, South Europe, between Africa and the Tethys in the south and North America–Europe and the Mid-European Ocean in the north. The South European plate has generally been considered as a stable unit. Studies of the Alpine system8, however, suggest that such an assumption may not be valid. I assume here that during the Carboniferous, South Europe was originally an elongated plate with nearly straight margins and internal structures. Collision with the irregular continental margins of the bounding plates North America–Europe and…

Jurassic Ophiolite Formation And Emplacement As Backstop To A Subduction-Accretion Complex In Northeast Turkey, The Refahiye Ophiolite, And Relation …

2013

International audience; The eastern Mediterranean region within the Tethyan realm shows a high concentration of ophiolites with contrasting times of formation and emplacement along the belt: In the Balkans, the ophiolites formed during the early to medial Jurassic, and were obducted during the late Jurassic, whereas in Turkey and farther east, structurally intact Jurassic ophiolites are rare and Jurassic ophiolite obduction is unknown. Here we report a structurally intact, large ophiolite body of early Jurassic age from NE Turkey, the Refahiye ophiolite, located close to the suture zone between the Eastern Pontides and the Menderes-Taurus block. The Refahiye ophiolite forms an outcrop belt,…

African linkage of Precambrian Sri Lanka

1991

New age and isotopic data show that the high-grade basement rocks of Sri Lanka were not linked to the Archaean granulite domain of southern India but experienced their main structural and metamorphic development during the Pan-African event some 950 to 550 Ma ago. This occurred when West Gondwana and East Gondwana collided to form one of the longest collisional structures in the Supercontinent — the Mozambique belt that extends from Mozambique to Ethiopia and Sudan. A major tectonic boundary, interpreted as a thrust zone, divides the Highland/Southwestern Complex in the central part of Sri Lanka from the Vijayan Complex in the E and SE. The former is interpreted to represent the remnant of …

Tectono-stratigraphic modelling of the North Sicily continental margin (southern Tyrrhenian Sea).

2004

A two-dimensional numerical modelling that simulate the kinematic and thermal response of the lithosphere to thinning was used for the quantitative reconstruction of the late Neogene to Recent times tectonic and stratigraphic evolution of the North Sicily continental margin (southern Tyrrhenian Sea). The numerical study of the evolution of the North Sicily margin builds on the crustal image and kinematic interpretation of the margin obtained by Pepe et al. [Tectonics 19 (2000) 241] on the basis of seismic data and gravity modelling. Tectonic modeling indicate that different segments of the margin were undergoing different vertical movements, which are mainly expression of the rifting and th…

Seismogenic rotational slumps and translational glides in pelagic deep-water carbonates. Upper Tithonian-Berriasian of Southern Tethyan margin (W Sic…

2017

Abstract Soft-sediment deformation structures (SSDSs), which reflect sediment mobilization processes, are helpful to identify punctual events of paleoenvironmental stresses. In the upper Tithonian-Berriasian calpionellid pelagic limestone of the Lattimusa Fm. outcropping in the Barracu section (W Sicily), paleoenvironmental restoration reveals the occurrence of a deep-water flat basin, characterised by undeformed planar bedding, laterally passing to a gentle slope where the deformed horizons alternate with undeformed beds. Here, two types of gravity slides have been differentiated on the basis of different kinds of SSDSs, brittle deformation, involved lithofacies, geometry and morphology. T…