scholarly journals Transition from slab roll-back to slab break-off in the central Apennines, Italy: Constraints from the stratigraphic and thermochronologic record

2021 ◽  
Author(s):  
Maria Giuditta Fellin ◽  
Malwina San Jose ◽  
Claudio Faccenna ◽  
Sean D. Willett ◽  
Domenico Cosentino ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Phase Evolution ◽  
Mediterranean Area ◽  
Accretionary Wedge ◽  
The West ◽  
Central Apennines ◽  
Two Phase ◽  
Transitional State ◽  
Intermontane Basins ◽  
Roll Back

Stratigraphic and thermochronologic data are used to study the processes that shaped the topography of the central Apennines of Italy. These are part of a major, active mountain belt in the center of the Mediterranean area, where several subduction zones control a complex topography. The Apennines were shaped by contraction at the front of the accretionary wedge overlying the subducting Adria microplate followed by extension at the wedge rear in response to eastward slab roll-back. In the central Apennines, intermontane extensional basins on the western flank rise eastward toward the summit. We contribute with new data consisting of 28 (U-Th-Sm)/He and 10 fission track ages on apatites to resolve a complex pattern of thermal histories in time and space, which we interpret as reflecting the transitional state of the orogen, undergoing a two-phase evolution related to initial slab retreat, followed by slab detachment. Along the Tyrrhenian coast, we document cooling from depths ≥3−4 km occurring between 8 and 5 Ma and related to the opening of marine extensional basins. Post−5 Ma, a broader region of the central Apennines exhibits cooling from variable depths, between <2 km in most areas and ≥3−4 km in the northeast, and with different onset times: at ca. 4 Ma in the west, at ca. 2.5 Ma in the center and northeast, and at ca. 1 Ma in the southeast. Between 5 and 2.5 Ma, exhumation is associated with modest topographic growth during the late stages of thrusting. Since 2.5 Ma, exhumation has concurred with the opening of intermontane basins in the west and in the east, with regional topographic growth and erosion, that we interpret to be associated with the locally detaching slab.

Subduction dynamics and rheology control on forearc and backarc subsidence: Numerical models and observations from the Mediterranean  

2021 ◽  
Author(s):  
Attila Balazs ◽  
Claudio Faccenna ◽  
Taras Gerya ◽  
Kosuke Ueda ◽  
Francesca Funiciello
Keyword(s):  
Subduction Zones ◽  
Numerical Models ◽  
Accretionary Wedge ◽  
Suction Force ◽  
Continental Subduction ◽  
Backarc Basins ◽  
The Mediterranean ◽  
Forearc Basins ◽  
Back Arc ◽  
Roll Back

<p>The dynamics of oceanic and continental subduction zones is linked to the rise and demise of forearc and backarc basins in the overriding plate. Subsidence and uplift rates of these distinct sedimentary basins are controlled by variations in plate convergence and subduction velocities and determined by lithospheric rheological structure and different lithospheric thicknesses.</p><p>In this study we conducted a series of high-resolution 2D numerical models applying the thermo-mechanical code 2DELVIS (Gerya and Yuen, 2007). The model, based on finite differences and marker-in-cell techniques, solves the mass, momentum, and energy conservation equations for incompressible media; assumes elasto-visco-plastic rheologies and involves erosion, sedimentation and hydration processes.</p><p>The models show the evolution of wedge-top basins lying on top of the accretionary wedge and retro-forearc basins in the continental overriding plate, separated by a forearc high. These forearc regions are affected by repeated compression and extension phases. Higher subsidence rates are recorded in the syncline structure of the retro-forearc basin when the slab dip angle is higher and the subduction interface is stronger and before the slab reaches the 660 km discontinuity. This implies the importance of the slab suction force as the main forcing factor creating up to 3-4 km negative dynamics topographic signals.</p><p>Extensional back-arc basins are either localized along inherited crustal or lithospheric weak zones at large distance from the forearc region or are initiated just above the hydrated mantle wedge. During trench retreat and slab roll-back the older volcanic arc area becomes part of the back-arc region. Back-arc subsidence is primarily governed by crustal and lithospheric thinning controlled by slab roll-back. Onset of continental subduction and soft collision is linked to the rapid uplift of the forearc basins; however, the back-arc region records ongoing extension. Finally, during hard collision the forarc and back-arc basins are ultimately under compression.</p><p>Our results are compared with the evolution of the Mediterranean and based on the reconstructed plate kinematics, subsidence and heat flow evolution we classify the Western and Eastern Alboran, Paola and Tyrrhenian, Transylvanian and Pannonian Basins to be genetically similar forearc–backarc basins, respectively.</p>

scholarly journals The AIDOS Project

1970 ◽  
pp. 10
Author(s):  
Lebanese American University
Keyword(s):  
Reproductive Rights ◽  
Arab World ◽  
West Bank ◽  
Gaza Strip ◽  
Mediterranean Area ◽  
International Project ◽  
Information Network ◽  
The West ◽  
West Bank And Gaza ◽  
The Mediterranean

The AIDOS Project: The Institute for Women's Studies in the Arab World, (IWSAW) was selected to take part in an international project aimed at establishing four documentation centers -specialized in women's human, civic, labor and reproductive rights- in fourArab countries: Lebanon, Egypt, Jordan, the West Bank and Gaza Strip. The main objective of the project is to create an information network of women's organizations throughout the Mediterranean area.

The geology and evolution of the Pinchi Fault Zone at Pinchi Lake, central British Columbia

1977 ◽  
Vol 14 (6) ◽  
pp. 1324-1342 ◽  
Author(s):  
I. A. Paterson
Keyword(s):  
Fault Zone ◽  
Subduction Zones ◽  
High Pressures ◽  
Metamorphic Grade ◽  
Fault System ◽  
Late Triassic ◽  
Transform Fault ◽  
The West ◽  
Early Mesozoic ◽  
Complex Fault

At Pinchi Lake, the Pinchi Fault Zone separates the early Mesozoic Takla Group to the east from the late Paleozoic Cache Creek Group to the west. Between these regions a complex fault system involves a series of elongate fault-bounded blocks of contrasting lithology and metamorphic grade. These blocks consist of: (a) highly deformed aragonite–dolomite limestone and blueschist, (b) pumpellyite–aragonite greenstone, (c) a harzburgite–gabbro–diabase–basalt ophiolite sequence, (d) serpentinized alpine ultramafite, and (e) Cretaceous (?) conglomerate. The blueschist probably formed at 8–12 kbar (8 × 105–12 × 105 kPa) and 225–325 °C during a penetrative early deformation which was closely followed by a later deformation associated with a Late Triassic uplift and cooling event. The ophiolite sequence is overlain by Late Triassic sediments which locally contain aragonite suggesting that at least part of the Takla Group may have also undergone high pressure – low temperature metamorphism.The evolution of the 450 km fault zone is discussed and a model is proposed which involves right lateral transform faulting on the Pinchi Fault and underthrusting along northerly dipping subduction zones during the Late Triassic. The blueschist formed at high pressures in such a subduction zone and leaked to the surface in zones of low pressure along an active transform fault.

PHASE EVOLUTION AND MAGNETIC PROPERTIES OF FEPT-PTTE2 NANORODS

2009 ◽  
Vol 23 (17) ◽  
pp. 3573-3578
Author(s):  
QINGYU YAN ◽  
AIDONG LI
Keyword(s):  
Magnetic Properties ◽  
Phase Transformation ◽  
High Temperature ◽  
Annealing Temperature ◽  
Phase Evolution ◽  
Polyol Process ◽  
Phase Ratio ◽  
High Temperature Annealing ◽  
Two Phase

FePt - PtTe 2 two phase nanorods have been produced by a polyol process. The shape and magnetic properties of two phase nanorods with different phase ratio are investigated. L10 phase transformation of FePt in the nanorods has been accomplished at annealing temperature as low as 400 °C with Hc above 500mT. High temperature annealing causes the disintegration of the nanorods due the melting/evaporation of Te element.

Catastrophic rainfalls in the West Mediterranean area

Meccanica ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 397-406
Author(s):  
M. C. LLasat ◽  
J. Barrantes
Keyword(s):  
Mediterranean Area ◽  
The West

Evolution of tear faults in subduction zones: an analogue modelling perspective

2020 ◽  
Author(s):  
Nicolò Bertone ◽  
Lorenzo Bonini ◽  
Roberto Basili ◽  
Anna Del Ben ◽  
Francesco Emanuele Maesano ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Strike Slip ◽  
Accretionary Wedge ◽  
Maximum Displacement ◽  
Gaussian Shape ◽  
Analogue Modelling ◽  
Experimental Apparatus ◽  
Subsidence Zone ◽  
Tear Fault

<p>Tear faults are common structures in subduction zones, especially at slab edges, where they origin from differential forces applied to a subducting slab in areas close to the trench. Presence and geometry of tears have been sometimes inferred from bathymetric features, suggesting the abrupt lateral termination of the subduction zone.</p><p>Differential forces acting at the subduction boundaries can be related to different mechanisms, such as slab retreat, differential velocities along plate margins, complex mantle flow, differential lateral rheology. As a result, plates down-warp and tear in a scissor-like motion, with both strike-slip and dip-slip kinematics.</p><p>The goal of this work is to gain insights into the evolution of tear faults by adopting an analogue modelling approach and comparing the results with natural cases. In particular, we focus on the bathymetric observation made in subduction zones where the upper plate accretionary wedge is not well developed. Two scenarios were considered: 1) tear faults nucleating and evolving in a homogeneous setting, i.e. without large mechanical discontinuities (e.g., Tonga subduction zone); and 2) tear faults reactivating pre-existing strike-slip faults as an analogue of transform faults (e.g., South Sandwich subduction zone).</p><p>The experimental apparatus was designed to reproduce the lateral propagation of a tear fault using two blocks: one entirely flat and the other with an inclined plane. Wet kaolin acts as the analogue of the intact rocks above a propagating tear fault.</p><p>Our results revealed different evolutionary processes: in the homogeneous setting, the tear fault generates a symmetric subsidence zone with an axis perpendicular to the fault zone and a depocenter located in the centre; in the second case, the depocenter is located in front of the fault plane and the subsidence zone is asymmetric. Both cases depict a symmetrical Gaussian shape of the displacement profile, with the maximum displacement located at the centre of the fault. However, the maximum slip (D<sub>max</sub>) and the fault length (L)  are both larger in the experiment involving a strong re-activation of the strike-slip fault than those in the case of the homogeneous setting.</p>

Differential geographical trends for loggerhead turtles stranding dead or alive along the Andalusian coast, southern Spain

2009 ◽  
Vol 90 (2) ◽  
pp. 225-231 ◽  
Author(s):  
Juan J. Bellido ◽  
Juan J. Castillo ◽  
Francisco Pinto ◽  
Juan J. Martín ◽  
José L. Mons ◽  
...  
Keyword(s):  
Mediterranean Area ◽  
Mediterranean Coast ◽  
Geographical Pattern ◽  
The West ◽  
Unequal Distribution ◽  
Induced Stress ◽  
Loggerhead Turtles ◽  
Gibraltar Strait ◽  
Alboran Basin ◽  
The Mediterranean

Every year, an undetermined number of loggerhead turtles cross the Gibraltar Strait entering and going out of the Mediterranean Sea. An unknown percentage of them strand on the Andalusian beaches, alive or dead, with an unequal distribution along the coast. We found a geographical pattern in the density of strandings, as well as in the proportion of them that were alive and dead. Atlantic areas receive a higher number of strandings, although most of them correspond to dead individuals, especially on the west coast (province of Huelva), whereas on the Mediterranean coast there is less difference between the number of alive and dead turtles stranded. The causes of stranding also presented a spatial segregation along these coasts: net fisheries were concentrated in Huelva, cold stunning was more frequent in Atlantic Cádiz, and debilitated turtle syndrome and longline were biased to the Mediterranean coast. The Atlantic areas might be an important accumulation zone for turtles, but where they endure a high human-induced stress and mortality. In the Mediterranean area, different causes, such as the narrowness of the Alborán basin, the ocean currents, human activity, or the number of turtles crossing, may increase the number of turtles stranding alive on the coast.

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