Evolución tectónica de una cuenca retroarco a partir del estudio de los clastos de una secuencia conglomerática (Mar Egeo, Grecia)

Resumen

In the Cyclades (eastern Mediterranean), low-angle normal faults juxtaposed Miocene sedimentary rock units on top of 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 foot wall progressively emerged through the ductile and brittle crust. The overall section of the sedimentary rocks is divided by a major unconformity that separates Lower to Middle Miocene turbiditic sandstones from Upper Miocene continental conglomerates. K-Ar and 40A r/39Ar geochronology, coupled by petrology and petrography ofdetrital clasts in the sedimentary hanging wall reveal the progressive exhumation of the footwall. Abundant metamorphic clasts yielding ages between 80-100 Ma occur throughout the conglomerate section and probably pertain to a vast Pelagonian-type rock mass now disappeared. Dating also revealed remnants of a completely eroded volcanic province that existed in the Cyclades at 10 Ma. Miocene crustal extension and exhumation of granitic plutons is recorded in the detritic sequence in a concentration of 10 Ma granitic clasts restricted to the top of the conglomerate section. Clasts typical to the currently exposed Cycladic blueschist unit, such as 40 Ma old blueschists, eclogites, and marble, were not found by us indicating the very late exposure of these footwall rocks