Temporally Constant Quaternary Uplift Rates and Their Relationship With Extensional Upper-Plate Faults in South Crete (Greece), Constrained With ~(36)C1 Cosmogenic Exposure Dating

摘要

Preserved sets of marine terraces and palaeoshorelines above subduction zones provide an opportunity to explore the long-term deformation that occurs as a result of upper-plate extension. We investigate uplifted palaeoshorelines along the South Central Crete Fault and over its western tip, located above the Hellenic Subduction Zone, in order to derive uplift rates and examine the role that known extensional faults contribute to observed coastal uplift. We have mapped palaeoshorelines and successfully dated four Late-Quaternary wave-cut platforms using in situ Cl-36 exposure dating. These absolute ages are used to guide a correlation of palaeoshorelines with Quaternary sea level highstands from 76.5 to similar to 900ka; the results of which suggest that uplift rates vary along fault strikes but have been constant for up to 600ka in places. Correlation of palaeoshorelines across the South Central Crete Fault results in a throw-rate of 0.41mm/year and, assuming repetition of 1.1-m slip events, a fault-specific earthquake recurrence interval of approximately 2,700years. Elastic-half-space modeling implies that coastal uplift is related to offshore upper-plate extensional faults. These faults may be responsible for perturbing the uplift rate signals in the south central Crete area. Our findings suggest that where uplifted marine terraces are used to make inferences about the mechanisms responsible for uplift throughout the Hellenic Subduction Zone, and other subduction zones worldwide, the impact of upper-plate extensional faults over multiple seismic cycles should also be considered.