Transcaucasia is one of the few places in the world where continuous marine sections of Upper Permian and Lower Triassic strata, containing a rich and diverse fauna, may be studied. The sections have been investigated by many authorities, but as yet there is no agreement on the exact position of the Permian-Triassic boundary.

Relatively complete sections co-exist with condensed sequences in Transcaucasia. Complete sections occur in the Dzhulfa Gorge of the Araxes River, near railway sidings Dorasham I and II, while condensed sequences occur elsewhere, as in parts of Nakhichevan A.S.S.R. and southwestern Soviet Armenia.

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Ruzhentsev and co-workers (1965) were able to recognize certain ammonoid and brachiopod assemblages in strata from both types of sections. In the more complete sections, the Phisonites-"Berhardites" beds are represented by a 20m (65.6 ft) thick clay lithofacies, while in the condensed sections these beds are represented by a thin limestones lithofacies not exceeding 2m (6.6 ft) in thickness. The Paratirolites and Claraia beds are usually represented in both types of sections by separate limestone lithofacies.

New discoveries of ammonoids in the Claraia beds are extremely important in determining the precise position of the systemic boundary. Several species of Ophiceras occur quite commonly in the lower part of these strata, while Gyronites and Koninckites occur sparingly in the upper part. Thus the Claraia beds are undoubtedly of Early Triassic age and correspond with the Otoceras and Gyronites Zones.

The Claraia beds are underlain by the Phisonites-Paratirolites beds and the upper part of the Vedioceras beds, containing a distinctive ceratite assemblage of Otoceras, Glyptophiceras and Metophiceras, together with rare tabulate and tetracorals, goniatites and productid brachiopods. Taking into consideration, then, the absence of Permian faunal elements in the Claraia beds and the similarity of underlying ammonoid assemblages in the Phisonites-Paratirolites beds to those of the Upper Permian Talung Formation of southern China, plus the other Permian faunal elements mentioned above, the authors favor a Permian-Triassic boundary between the Paratirolites beds and the Claraia beds.

The interval of the section from the "Tompophiceras" beds up to the Paratirolites beds may be regarded as the highest horizon of the Permian System not yet included in the standard scale. The authors here suggest that this stratigraphic interval, together with the Phisonites beds, be designated the Dorashamian Stage. This new stage is believed to have equivalents in Iranian Azerbaijan (Stepanov et al., 1969), central Iran (Taraz, 1969) south China (Chao, 1959) and Madagascar (Tozer, 1969).

The Permian-Triassic boundary problem in Transcaucasia should not be considered completely solved, however. Some investigators believe that the ammonoids from the upper part of the Vedioceras beds and the Phisonites beds are truly Triassic in aspect. These workers explain the presence of relict Permian corals, goniatites and productids in these strata by uninterrupted transitional conditions from the Permian to the Triassic.

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