Search results for "Continental margin"
showing 10 items of 78 documents
Episodic deposition of the Lias in the Medianes nappe (western Switzerland): a record from mineralized ammonite-bearing beds
1992
Abstract Sinemurian and Pliensbachian depositional sequences from the starved distal northern continental margin of the Tethys are preserved in the Medianes Nappe (Western Swiss Prealps). They contain mineralized beds which include a variety of facies. The northern continental margin of the Tethys was broken into blocks, less than 50 km wide, during an extensional phase. The Sinemurian and Pliensbachian sediments in the study are vary in thickness from less than 50 m in the north to more than 200 m in the south. Although the upper Sinemurian to Pliensbachian mineralized beds are thin, between 0.10 and 0.50 m thick, they commonly contain several distinct faunal horizons stacked one upon anot…
New stratigraphical data on the Middle-Late Jurassic biosiliceous sediments from the Sicanian basin, Western Sicily (Italy)
2008
The reported data present the stratigraphy of several sections across a Middle–Late Jurassic Radiolaritic Unit, well exposed in different thrust sheets pertaining to the Maghrebian chain of Southwestern Sicily. The aim was to define the chronostratigraphical distribution of the Jurassic biosiliceous sedi- mentation in the Sicanian palaeogeographical zone, a deep water basin belonging to the Southern Tethys continental margin. The radiolarian biostratigraphy indicates that the switching from carbonate to siliceous sedimentation in the Sicanian Basin is referable to the Bajocian, as shown by the section of Campofiorito, near Corleone. The biostratigraphical dataset allows the correlation betw…
Age and tectonic setting of granitoid gneisses in the Eastern Desert of Egypt and south-west Sinai
1994
Strongly deformed and locally migmatized gneisses occur at several places in the southern Eastern Desert of Egypt and in Sinai and have variously been interpreted as a basement to Pan-african (≈900 to 600 Ma) supracrustal and intrusive assemblages. A suite of grabbroic to granitic gneisses was investigated in the Hafafit area, which constitutes an I-type calc-alkaline intrusive assemblage whose chemistry suggests emplacement along an active continental margin and whose granitoid members can be correlated with the so-called ‘Older Granites’ of Egypt. 207Pb/206Pb single zircon evaporation from three samples of the Hafafit gneisses yielded protolith emplacement ages between 677 ± 9 and 700 ± 1…
Preliminary data concerning the morphology of a Calabrian Ionian margin area: Caulonia and Marina di Gioiosa canyons
2008
In the framework of the Vector National Italian Project (VulCost line), aimed to study the role of the morphology and the geology of the Ionian Calabrian margin in the coastline evolution, an oceanographic cruise was planned to collect geophysical data along two canyon systems: Caulonia and Marina di Gioiosa. The survey explored the continental shelf and slope from a depth of 15 m to more than 1150 m, using Multibeam Echosounder to investigate the seafloor topography. This work provides an outline of the erosive feature of the slope, shaped mostly by seasonal river input and by the connection to the structural and geological characteristics of the margin, made interesting by a narrow shelf …
Structural highs formation and their relationship to sedimentary basins in the north Sicily continental margin (southern Tyrrhenian Sea): implication…
2005
Two high-penetration seismic profiles across the continental margin of north Sicily (southern Tyrrhenian Sea) have been interpreted to construct a crustal section across the margin and to provide a three-dimensional perspective on the upper crustal setting of the Solunto High and its structural relationships with the adjacent Cefalù Basin. Crystalline rocks of the Kabilian-Calabrian Units (KCU) are recognized in the Solunto High region and farther to the north. The KCU body is tectonically superimposed onto sedimentary rocks pertaining to the Sicilian-Maghrebian Units (SMU) and the Solunto High corresponds to the thrust sheet culmination. Its occurrence in the Solunto High demonstrates that…
A new concept of continental construction in the Central Asian Orogenic Belt
2011
A new concept of continental construction based on four main terms: (1) crustal growth, (2) crustal formation, (3) continental growth and (4) continental formation is presented here. Each of these terms reflects a certain process responsible for the formation of what we call now "continental crust". This concept is applied to the Central Asian Orogenic Belt (CAOB), which is a global major accretionary orogen formed after the closure of the Paleo-Asian Ocean, and to its actualistic analogues - orogenic belts and accretionary complexes of the Western Pacific. The main focuses of the paper are the state of activities in the study of the CAOB, the theoretical basics of the new concept of contin…
The architecture and Neogene to Recent evolution of the W Calabrian continental margin: an upper plate perspective to the Ionian subduction system (C…
2010
The western Calabria continental margin forms the transition between the Pliocene to Recent Marsili spreading center and continental Calabria, all parts of the upper plate of the Ionian subduction zone. Integrating high-resolution and crustal seismic images constrained by gravity modeling, we provide a detailed reconstruction of the architecture of the margin and develop a new scheme for its Miocene to present evolution. This time span encompasses the continent-continent collision between Africa and Eurasia, subsequent orogenic collapse and rifting apart between the two continental masses, and the Pliocene to Recent emplacement of oceanic crust in the Vavilov and Marsili basins. The crust o…
Structural trends and palaeogeography of the central and western Sicily Belt: new insights
1995
The geology of the Sicilian mainland is summarized by N–S geological sections. A continuous late Cenozoic orogenic belt through central and western Sicily resulted from a complex deformative history, recorded by several tectonic events. The deformation mainly involved the sedimentary cover of the old African continental margin, formed in a large basinal area, bordered at its southern margin by a shallow-water carbonate environment attached to Gondwana. The orogenic belt involves a complex architecture of thrust systems, of different size, geometry and palaeogeographical origin. Deformation, which mainly developed in the earlier stages of thrusting in the basinal rock assemblages, mainly gav…
Geohazard assessment of the north-eastern Sicily continental margin (SW Mediterranean): coastal erosion, sea-level rise and retrogressive canyon head…
2022
Coastal dynamics are the result of several processes controlling the balance between sediment input and output over time. The beach system is not always able to maintain a neutral coastal balance due to natural and anthropogenic causes. We present an integrated marine geology, geomorphological and sea-level rise analysis in the coastal sector between Torre delle Ciavole and Capo Calavà (North-Eastern Sicily, Italy).This sector is characterized by high uplift rates and frequent seismicity (mainly generated by the very active Vulcano-Tindari Fault System), promoting the development of mass-wasting processes in the coastal and offshore sectors. A main erosive feature observed in the area is th…
Mechanism and time of deformation and metamorphism of mylonitic orthogneisses from the Shagou Shear Zone, Qinling Belt, China
1990
Abstract The Shagou Shear Zone south of Xian (Shaanxi Province) is a branch of the Shangdan Fault Zone in the Qinling Belt and documents ductile deformation that affected granitoid rocks. Mylonitization took place under conditions of the lower amphibolite facies at temperatures of ca. 530°C, followed by a phase of stagnation, still under the same metamorphic conditions. The last deformation was a weak event during retrogressive greenschist metamorphism. The emplacement of the granitoid precursors of the mylonite is dated at 211 ± 8 Ma by the U/Pb zircon method, much younger than Nd model ages of 1.2–1.3 Ga, which indicates the involvement of older continental crust, probably in an active co…