QUATERNARY TECTONICS OF THE ARGOLIKOS GULF AND ADJACENT BASINS, GREECE

A single-channel seismic reflection survey of the Argolikos Gulf and I dhra Channel casts light on the tectonic history of this extensional b asin of which the current subsidence phase is less than 0.5 Ma old. Al though the Gulf has very low seismicity, Holocene subsidence on the we stern boundary faults increases southward from 50 to 100 cm ka-1. The eastern margin of the Gulf is offset eastward twice. For these offsets we postulate two left-lateral strike-slip faults accommodating a sout hward increase in the extension rate. These features can be traced on land where at least one of them shows evidence of left lateral movemen t. The Idhra Channel has a different tectonic pattern of E-W-trending extensional troughs separated by basement ridges. The latter diverge w estward and continue into the southern Argolid as Mesozoic limestone r idges separated by ophiolite-floored tectonic valleys. The causes of t his discordant pattern remain obscure.