Neogene tectonics and basin fill patterns in the Hellenic outer-arc (Crete, Greece)

Six time-slice reconstructions in the form of palaeogeographical maps show the large-scale tectonic and sedimentary evolution of the Hellenic outer-ar e basins in central and eastern Crete for the middle and late Miocene. The reconstructions are based on extensive field mapping and a detailed chronos tratigraphy. Latest compressional features related to subduction and associated crustal thickening are poorly dated and assigned a middle Miocene age. These are po ssibly contemporaneous with widespread occurrence of breccia deposits all o ver Crete. The precise date for the onset of extension, possibly controlled by the roll-back of the subsiding African lithosphere, remains at this poi nt a discussion. We present circumstantial evidence to place the beginning of the roll back in the middle Miocene, during the accumulation of an arc-p arallel, westward-draining fluvial complex. The continental succession is t ransgressed steadily until it is interrupted by an important tectonic event at the boundary of the middle and late Miocene (normally seen as the onset of slab roll-back). In the earliest late Miocene a few large-sized fault b locks along arc-parallel normal faults subsided rapidly causing a deepening of the half-graben basins up to approximately 900 m. About 1 Myr later, a new N020E and N100E fault system developed fragmenting the existing half-gr abens into orthogonal horst and graben structure. The development of the ne w fault system caused original continental regions to subside and original deep basins to emerge, which is not easy to reconcile with roll back contro lled extensional processes alone. Underplating and inherited basement struc ture may have played here an additional role, although evidence for firm co nclusions is lacking. In late Miocene times (late Tortonian, approximate to 7.2 Ma), the extensional outer are basins become deformed by N075E-orienta ted strike-slip. The new tectonic regime begins with strong uplift along ex isting N100E: fault zones, which developed about E-W-striking topographical highs (e.g. Central Iraklion Ridge and Anatoli anticline) in about 0.4 Myr . The strong uplift is contemporaneous with abundant landsliding observed a long an important N075E fault zone crossing eastern Crete and with renewed volcanic activity of the are. The origin of the ridges may be due to active folding related to the sinistral slip.