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Abstract.In the western Alpine system, Neogene extensional tectonics triggered the development of marine basins on the concave side of tight orogenic arcs, as happened within the Alboran Crustal Domain, the hinterland of the Gibraltar Arc. A detailed analysis of the structural and metamorphic records of one of the main Alboran Domain complexes, however, plainly reveals a complex tectonic evolution prior to the development of the Miocene arc/back arc system, which includes a major intraorogenic extensional event. This large-scale subvertical shortening, that can be assessed from the PT paths of representative tectonic units, was subsequent to the continental crust subduction inferred from high pressure-low temperature mineral asssemblages. The crustal section was thinned in nearly isothermal conditions, its thickness being reducted to at least 1/3 of the initial value. Yet still before the Miocene, a second contractional event led to the overthrusting of high-grade metamorphic rocks over other low-grade rocks, accompanied by subordinate overturning of the metamorphic zones. Since migration of the Gibraltar Arc is roughly balanced by crustal spreading in the back arc, available data concerning Miocene extension suggest that the Alboran Domain can be restored to its appropriate position several hundred kilometers to the east. Thus a collision belt that underwent significant intraorogenic extension must have existed in what is now the western South-Balearic basin.

A close relationship of the kinematics and timing between low‐angle extensional faulting and upright folding is established for the Miocene detachment systems in the hinterland of the Betics in southeastern Spain. Folding accompanied tectonic denudation developing elongated domes with fold axes both parallel and perpendicular to the direction of extension. The geometry, kinematics, and tectonic evolution of two major sequentially developed extensional fault systems have been characterized in several E‐W elongated mountain ranges of the central Betics on the basis of new cartographic and structural data and a comprehensive revision of other available geological and geophysical observations. The extensional systems have an average WSW direction of extension and led to exhumation of the two lower metamorphic complexes of the Betics, the Nevado‐Filabride and the Alpujarride, during the middle and upper Miocene (Serravallian to Tortonian). The extended domain contains a core complex, with distal and proximal antiformal hinges separated by around 60 km and with a fold amplitude of ∼6 km (measured parallel to the direction of extension). The total amount of extension across the core complex is about 109–116 km, corresponding to a stretching factor (β) of 3.5–3.9, estimated using the distance between fold axial surfaces and a geometrical model accomplishing footwall deformation during tectonic denudation via subvertical simple shear. The elongated domal and basinal geometry of the detachments and their respective footwalls is due to the interference between two sets of orthogonal large‐scale open folds, trending N‐S and E‐W. Longitudinal, N‐S trending folds are interpreted as isostatic folds, i.e., folds that developed in response to differential unloading of the extensional detachment footwalls inducing ductile flow in the middle crust. These folds formed in a rolling‐hinge anticline in which rotation migrates westward through the footwall as it is progressively unroofed. In contrast, E‐W trending folds, being subparallel to the direction of extension, have a contractional origin and progressively affect to the west the isostatically readjusted segments of the detachments once they are inactive. Orthogonal folding occurred since the Serravallian to lower Pliocene. Extension is still active from the rolling‐hinge anticline in Sierra Nevada to the west. The middle Miocene to Pliocene tectonic evolution of the Sierra Nevada elongated dome at the core of the Betic hinterland is another example of the coexistence of extension and contraction during continued overall convergence and mountain‐building.

New bathymetric and magnetic anomaly data from the Phoenix Ridge, Antarctica, show that extinction of all three remaining segments occurred at the time of magnetic chron C2A (3.3 ± 0.2 Ma), synchronous with a ridge-trench collision south of the Hero Fracture Zone. This implies that the ultimate cause of extinction was a change in plate boundary forces occasioned by this collision. Spreading rates slowed abruptly at the time of chron C4 (7.8 ± 0.3 Ma), probably as a result of extinction of the West Scotia Ridge, which would have led to an increase in slip rate and transpressional stress across the Shackleton Fracture Zone. Spectacular, highrelief ridges flanking the extinct spreading center, mapped for the first time using multibeam swath bathymetry, are interpreted as a consequence of a reduction in spreading rate, involving a temporary magma oversupply immediately prior to extinction.

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Mediterranean tectonics results in tight orogenic arcs enclosing back‐arc basins of oceanic or thinned continental lithosphere. The Gibraltar Arc cannot be explained solely by the Europe‐Africa plate convergence; therefore complementary mechanisms have been proposed. Most of them imply a westward motion of the arc and a general transpressive regime on both branches (Betic and Rif chains). A structural revision made along the western Gibraltar Arc allows us to generate a detailed kynematic map and to introduce new constraints on the possible arc formation mechanisms. Our results suggest that the strain partitioned into two main types of structures: structures accommodating suborthogonal shortening (folds and thrusts) and structures accommodating arc‐parallel stretching (normal faults, conjugate strike‐slip faults, and distributed minor structures). On the basis of the fan pattern depicted by the slip direction of contractional structures and the homogeneous distribution of arc‐parallel stretching, an arc formation mode close to the piedmont glacier type is suggested.

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