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.

Moore, G. F., Taira, A., Klaus, A., Becker, L., Boeckel, B., Cragg, B. A., Dean, A., Fergusson, C. L., Henry, P., Hirano, S., Hisamitsu, T. et al. (2001). New insights into deformation and fluid flow processes in the Nankai Trough accretionary prism: Results of Ocean Drilling Program Leg 190. Geochemistry, Geophysics, Geosystems, 2, Article No: 2001GC000166.The Nankai Trough accretionary prism is considered an ?end-member? prism accreting a coarse terrigenous sediment section in a setting with structural simplicity, unparalleled resolution by seismic and other geophysical techniques, and large historic earthquakes. It therefore has been the focus of Ocean Drilling Program (ODP) drilling to address several unresolved questions concerning accretionary processes and prism evolution. At six sites cored along two transects across the Nankai Trough accretionary prism during ODP Leg 190, lithostratigraphy and sediment diagenesis vary markedly. For the first time, reference sites at the seaward ends of the two transects defined the stratigraphic framework of the accreting/subducting Shikoku Basin sedimentary section. A thick section of Miocene turbidites and smectite-rich mudstone is present within the subducting section at the Ashizuri site. The turbidites and mudstones are absent in the correlative section at the Muroto site; variations in lithology, mineralogy, and hydrologic properties of the incoming sediments probably contribute to the difference in prism wedge taper between the two transects, while possibly controlling the seismic character of the active plate boundary. The d?collement in both transects is localized within a common stratigraphic unit (?5.9?7 Ma) within the lower Shikoku Basin facies. The d?collement is also a major boundary for both physical and mechanical properties. A broad low-chloride pore water anomaly in the lower Shikoku Basin unit, first identified at Site 808, progressively decreases in magnitude from prism to basin along the Muroto Transect. Physical properties relationships, evidence for mineralogic changes in the sediments, and pore fluid chemistry suggest that the chloride anomaly results primarily from in situ diagenetic reactions in the sediments, possibly augmented by flow of freshened fluid from depth. New constraints on stratigraphy and age of units along more landward parts of the Muroto Transect have dramatically changed our ideas about the tectonic evolution of the prism in this area. Growth of the seaward-most part of the prism took place very rapidly, with 40 km of accretion within the past 2 Myr. This rate is at least 3 times greater than growth rates in a comparable prism.Peer reviewe

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In the Cyclades, low-angle normal faults juxtaposed Miocene sedimentary rock units lying over Alpine blueschist- and greenschist-facies metamorphic rocks and Miocene granites. The sedimentary units in the hanging wall were deposited in fault-bounded basins while their footwalls progressively emerged through the ductile and brittle crust.The sedimentation in the basins evolved from marine turbidites in the Early Miocene to shallow/continental conglomerates during the Late Miocene. The transition from marine to fan delta sedimentation was coeval with widespread magmatism and possibly reflects true crustal uplift. It is inferred that the sequence is no younger than 8 Ma.K–Ar and 40Ar/39Ar geochronology, petrology and petrography of the clasts deposited on the hanging wall provide proof of progressive exhumation of the footwall and reveal the nature of the overburden that covered the Cycladic blueschist belt during Alpine orogeny in the Tertiary. Abundant metamorphic clasts yielding mica cooling ages between 80 and 100 Ma occur throughout the sedimentary section and probably pertain to a vast Pelagonian-type rock mass that covered the internal Hellenides from the Olympos to the central Cyclades. In addition, volcanic clasts dated at 10 Ma reveal the existence of a hitherto unknown volcanic province of that age in the central Aegean. Miocene crustal extension and exhumation of granitic plutons is recorded in the detrital sequence in a concentration of 10 Ma granitic clasts restricted to the top of the conglomerate sequence. A group of metamorphic clasts that yielded ages of 13–16 Ma possibly represents exhumation of mid crustal levels. Clasts similar to the currently-exposed Cycladic Blueschist Unit, such as 40 Ma old blueschists, eclogites and marble, were not found, thus indicating the very late exposure of these footwall rocks.