Ibrahim Murtuzayev¹

(1) Independent, Baku, Azerbaijan

ABSTRACT: Role of the 40th Parallel Shear in Tectonics of South Caspian Basin

40th parallel shear is a 40 km wide lateral displacement zone, whose southern master fault coincides with latitude 40o North. In Azerbaijan, its strand embraces, from east to west, the Pliocene Navaghy pull-apart, S-shaped Sarysou lake, series of Jurassic calderas in the Lesser Caucasus, and Paleocene Kelbadjar caldera west of the ophiolites. Seismic profile across the supposed offshore continuation of shear reveals the flower structure. Imageries show the 40th parallel to coincide with the linear zone of evaporation related to thermal anomaly, which indicates the shear to be mantle-involved. High heat flow results in high fluidity and enormous length of flows produced by the shear-controlled active mud volcanoes. Mesozoic volcanics produced by the shear-controlled paleovents belong to subalkaline type. Tectonic motions outward of the 40th parallel shear are indicated by 180o-reversal in directions of mud volcano feeders' tilt and fold vergence that occurs along it, and explain simultaneous subduction of South Caspian plate beneath Scythyan plate to the north and South Caucasian plate to the south-west. Outward tilt of faults shows that transtension has not yet reached the stage of wall's downcreep towards the splitting axial zone. On the eastern Caspian shore, 40o N is a strike line of Koubadagh suture separating the Turan and South Caspian plates. This is some 20´ to the south with respect to western onshore's South Caspian northern margin and implies dextral displacement along deep meridional fault bisecting the Caspian.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado