ORIGIN OF THE SOUTH CASPIAN IN THE LIGHT OF DATA ON ITS STRIKE-SLIP FAULTING

South Caspian plate (SCP) represents a block of oceanic crust surrounded by continental blocks of Eurasia and Arabia-Iran and is traditionally considered to be a remnant of either Paleo-Tethys or Mesozoic back-arc basin formed by rifting of Lesser Caucasus arc.

Both concepts seem disputable in that (i) they contradict the SCP being "unconsumed"; (ii) drawing of "Tethys/Gondwana suture" along the southern Caspian shore is based on the only ophiolite exposure; (iii) geometry of SCP is not parallel to that of the Lesser Caucasus.

Writer's and published data allow the following supposition: present South Caspian has been opening in Meso-Cenozoic in a result of northward-propagating process of transtension of Eurasian margin along successively younger, latitudinal, strike-slip faults (SSF's).

Line of reasoning includes:

1. Series of latitudinal mantle-involved SSF's passing, from W to E, through S. Caucasian plate, SCP, Kopet Dagh fold belt, and Turan plate;

2. Successively younger disrupted formations, smaller offsets, and narrower pull-aparts developed progressively northward along above SSF's;

3. Bilateral subduction of SCP by active divergence along the 40th parallel shear, which is the northernmost extensional SSF;

4. Indications of SCP bilateral subduction in Mesozoic;

5. Similarity of Paleozoic ophiolites exposed at Rasht, SSW of SCP, to those of Dziruli and Khrami basement culminations in the Lesser Caucasus; similarity of Paleozoic metamorphic rocks of the Gorgan Coastal Plane, SSE of SCP, to those of southern margin of the Turan plate basement exposed on the northern coast of Krasnovodsk Bay and drilled on the Karabogaz Swell, eastern Caspian;

6. Relation of both Rasht and Gorgan to strike-slip-faulted blocks, i.e., their unlike formation in situ;

7. Two transfer SSF's that have been accommodating the movement of separated slices: West Caspian fault, which separates the S. Caspian and S. Caucasian plates and is trending parallel to the western Caspian shore, and Djebel fault, which has been established in West Turkmen desert and is trending parallel to the eastern Caspian shore.

Origin of SCP is supposed to be generally analogous to that of the Western Black Sea opened in mid-Cretaceous as Western and Central Pontides separated from Eurasia and moved southeast to leave an oceanic basin behind them.