ACTIVE TECTONICS OF THE SOUTH CASPIAN REGION

The South Caspian Basin is an important element in the accommodation of the convergence between Arabia and Eurasia at the longitude of Iran. Most of the basin is underwater, yet it is largely aseismic, flat and probably relatively rigid. Its motion within the collision zone, and its tectonic significance, must therefore mostly be assessed from the deformation observed on its edges, in the very active seismic belts that surround it on all sides. Since the last major review of the active tectonics of this region in 2002, much improved new data have emerged from GPS, earthquakes and an increasing knowledge of the active faulting and Quaternary geology. As a result, we now have a better understanding of how the current motions in these belts relate to the wider collisional configuration, though other uncertainties and controversies remain, especially in the timing, duration and onset of large-scale features in the Tertiary geology. This talk will review the new information in this region, built up principally by sustained fieldwork in Iran and a re-examination of the earthquake information. The tectonics of the South Caspian basin is probably representative of a more general process within collision orogens, in which trapped basins become surrounded by thrust belts on all sides that eventually consume them; but the processes involved are very three-dimensional, likely to involve rotations about vertical axes and to change rapidly with time, and leave behind them a rather complicated and confusing geological record.