Roll-back controlled vertical movements of outer-arc basins of the Hellenic subduction zone (Crete, Greece)

Crustal thickening north of the Hellenic subduction zone continued in the m ost external zones (e.g. Crete) probably until the late middle Miocene. The following period of predominant extension has been related by various work ers to a number of causes such as: (1) trench retreat (roll back) driven by the pull of the African slab and (2) gravitational body forces associated with the thickened crust, both in combination with NNE motion of the Africa n plate combined with westward extrusion of the Anatolian block along the N orth Anatolian Fault. To verify these hypotheses an inventory of fault orie ntations and fault-block kinematics was carried out for central and eastern Crete and adjoining offshore areas by combining satellite imagery, digital terrain models, and structural, seismic, sedimentary and stratigraphical f ield data, all set up in a GIS. The GIS data set enabled easy visualization and combination of data, which resulted in a relatively objective analysis . The geological results are discussed in the light of a numerical model th at investigated the intraplate stresses resulting from the above mentioned forces. Our tectonostratigraphic results for the late Neogene of central and easter n Crete show three episodes of basin extension following a period of approx imately N-S compression. In the earliest Tortonian, N130E- to N100E-trendin g normal faults developed, resulting in a roughly planar, are-parallel faul t system aligning strongly asymmetric half-grabens. The early Tortonian to early Messinian period was characterized by an orthogonal fault system of N 100E and N020E faults resulting in rectangular grabens and half-grabens. Fr om the late Tortonian to early Pleistocene, deformation occurred along a pa ttern of closely spaced, left-lateral oblique N075E faults, orientated para llel to the south Cretan trenches. Deformation phases younger than early Pl eistocene are dominated by normal to oblique faulting along WSW-ENE (N050E) faults and dextral, oblique motions along NNW-SSE (N160E) faults. Many fau lts that were generated during previous deformational episodes appear to be reactivated in later periods. Our tectonostratigraphy paints to a three step anticlockwise rotation of ac tive fault systems since the late middle Miocene compressional phase. We su ggest here that the rotation is associated with a reorganization of the str ess field going from SSW-NNE tension in the early late Miocene to NE-SW lef t-lateral shear in the Quaternary. The rotation is likely to be a response to are-normal pull forces combined with a progressive increase of the curva ture of the are. During the Pliocene to Recent period, the SSW-ward retreat of the are and trench system relative to the African plate was accomplishe d by transform motions in the eastern (Levantine) segment of the Hellenic A re, resulting in, respectively, NNW-SSE and NE-SW left-lateral shear on Cre te.