QUATERNARY TOPOGRAPHIC DEVELOPMENT OF THE HELLENIC FOREARC: INSIGHTS FROM THE TECTONIC GEOMORPHOLOGY OF SOUTH-CENTRAL CRETE, GREECE

The topographic development of the island of Crete, Greece is characterized by rapid and sustained uplift and extension. Crete occupies a forearc high above the Hellenic subduction zone. N-S and E-W striking faults are pervasive on the island, with the E-W oriented structures dwarfing the others in size. A diversity of opinion exists on the E-W striking faults, which have been interpreted as active or inactive and contractional, strike-slip, or extensional. Here we present new observations from south-central Crete on the activity and kinematics of a large-scale E-W striking fault array from south-central Crete. Our results clarify the ongoing role of these structures in the construction of topography on Crete and provide clues of the processes governing rapid uplift in the Hellenic forearc. Pleistocene marine terraces were used in conjunction with optically stimulated luminesce dating and correlations to the late Quaternary eustatic curve to document coastal uplift and identify active faults. Two southward dipping normal faults were mapped that extend offshore and offset terraces, indicating that (1) they are active and, (2) N-S directed extension continues into the late Quaternary. Importantly, marine terraces are preserved in the foot – and hanging walls of both faults, demonstrating that regional uplift outpaces surficial extension along Crete’s southern coast. Average uplift rates are ~0.65 mm yr^-1 and ~0.35 mm yr^-1 in the foot – and hanging walls, respectively. Fault aspect ratios were used to constrain the three dimensional geometry of one of the more easterly fault, which forms the ~ 55 km long range front of the Dikti Mountains. This analysis suggests that this fault projects to near the brittle-ductile transition, a scenario that is kinematically inconsistent with hypothesized N-S shortening on an adjacent offshore structure to the south. This kinematic assessment and the position of mapped onshore faults demonstrate that the southern coastline of Crete is bound by a large and active extensional fault array. Our results do not support a model of active orogenesis due to shortening in the upper crust, but are consistent with forearc growth due to underplating, dynamic topography, or both. Within this framework we present a new conceptual model for the late Cenozoic topographic evolution of the Hellenic forearc.