Search results for "Nappe"
showing 10 items of 35 documents
Kinematics and U-Pb zircon ages of the sole metamorphics of the Marmaris Ophiolite, Lycian Nappes, Southwest Turkey
2018
In the eastern Mediterranean, the Lycian Nappes are found in the structurally uppermost position in the Anatolide-Tauride belt related to the closure of the Neotethys. In Western Turkey, the Marmaris Ophiolite with the metamorphic sole occupies the uppermost tectonic position in the Lycian belt. The metamorphic sole is represented by discontinuous tectonic slices composed of amphibolites, phyllites, micashists and quartzo-feldspathic micaschists. Zircons from the micashists and quartzo-feldspathic micaschists display dark cores and rims. The cores yield ages between 229 and 175 Ma, inner rims yield ages between 153 and 143 Ma and the outer rims show a concordia age of 96.7 ± 0.79 Ma. In ter…
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…
Scheelite-Bearing Metalliferous Sequences of the Peloritani Mountains, Northeastern Sicily (with some Remarks on Tungsten Metallogenesis in the Calab…
1988
The Peloritani Mountains (Northeastern Sicily) are part of a segment of the Hercynian chain recognized in the Calabrian-Peloritan Arc, geotectonically defined by a pre-Hercynian crystalline basement (Aspromonte Nappe + Mandanici Unit) overthrust and overturned on its Paleozoic (Cambro-Ordovician up to Devonian Carboniferous) volcanosedimentary cover. Tungsten (scheelite) and associated polymetallic stratabound ores, more or less intensely affected by the pre-Hercynian and Hercynian tectonometamorphic events, are confined to the pre-Hercynian basement. In particular, the most significant scheelite-tourmaline (arsenopyrite) and scheelite-carbonate-quartz (albite) mineralizations could be cons…
Evidence of positive tectonic inversion in the north-central sector of the Sicily Channel (Central Mediterranean)
2016
In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pul…
Early exhumation of high-pressure rocks in extrusion wedges: Cycladic blueschist unit in the eastern Aegean, Greece, and Turkey
2007
Structural, metamorphic, and geochronologic work shows that the Ampelos/Dilek nappe of the Cycladic blueschist unit in the eastern Aegean constitutes a wedge of high-pressure rocks extruded during early stages of orogeny. The extrusion wedge formed during the incipient collision of the Anatolian microcontinent with Eurasia when subduction and deep underthrusting ceased and the Ampelos/Dilek nappe was thrust southward over the greenschist-facies Menderes nappes along its lower tectonic contact, the Cycladic-Menderes thrust, effectively cutting out a ∼30- to 40-km-thick section of crust. The upper contact of the Ampelos/Dilek extrusion wedge is the top-to-the-NE Selcuk normal shear zone, alon…
How to resist subduction: evidence for large-scale out-of-sequence thrusting during Eocene collision in western Turkey
2001
Significant along-strike variations have locked large parts of the Alpine subduction complex in the Eastern Mediterranean in the Eocene, and defined the end of high-pressure accretion in western Turkey. Structural analysis reveals that the Anatolide belt in western Turkey formed under greenschist facies metamorphic conditions in the Eocene when a high-pressure metamorphic fragment of the Adriatic plate (the Cycladic blueschist unit) was thrust onto the imbricated mid-crustal units of the Anatolian microcontinent (the Menderes nappes). The contact between the Cycladic blueschist unit and the Menderes nappes, the Cyclades–Menderes thrust, represents an out-of-sequence ramp which cuts up-sect…
Horizontal contraction or horizontal extension? Heterogeneous Late Eocene and early Oligocene general shearing during blueschist and greenschist faci…
1995
Mylonitic structures related to two orogenic events are described from the upper and lower contacts of the Combin zone and the immediately overlying upper Austroalpine Dent Blanche nappe/Mont Mary klippe and the directly underlying lower Austroalpine Etirol-Levaz slice. The first event, Late Eocene in age, commenced during blueschist facies P-T conditions, but pre-dated the peak of subsequent greenschist facies overprint. The second event, Early Oligocene in age, took place during retrograde greenschist facies conditions. Most sense of shear indicators associated with the retrograde mylonites indicate top SE shearing, but subordinate top NW displacing shear sense indicators have also been m…
From intra-oceanic subduction to arc accretion and arc-continent collision: Insights from the structural evolution of the Río San Juan metamorphic co…
2013
The Río San Juan metamorphic complex exposes a segment of a high-pressure subduction-accretionary complex built during Caribbean island arc-North America continental margin convergence. It is composed of accreted arc- and oceanic-derived metaigneous rocks, serpentinized peridotites and minor metasediments forming a structural pile. Combined detailed mapping, structural and metamorphic analysis, and geochronology show that the deformation can be divided into five main events (D1eD5). An early subduction-related D1 deformation and M1 metamorphism produced greenschist (mafic rocks of the Gaspar Hernández peridotite-tectonite), blueschist and eclogite (metamafic blocks in the Jagua Clara mélang…
Structural analysis of a complex nappe sequence and late-orogenic basins from the Aegean Island of Samos, Greece
1999
The island of Samos in the Aegean Sea exposes high-pressure metamorphic rocks of the Cycladic blueschist unit which are sandwiched between the mildly blueschist-facies Kerketas nappe below and the overlying non-metamorphic Kallithea nappe. Structural and metamorphic analysis shows that deformation can generally be divided into four main stages: (1) Eocene and earliest Oligocene 0ESE‐WNW-oriented nappe stacking (D1 and D2) associated with blueschist- and transitional blueschist‐ greenschist-facies metamorphism (M1 and M2). D2 caused emplacement of the blueschist unit onto the Kerketas nappe indicating that thrusting occurred during decompression. (2) A subsequent history of Oligocene and Mio…
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…