A continuous marine carbonate sequence, commencing with the Artinskian transgression and ending with a regression of probably early Middle Triassic age, was discovered by the author in 1967 in central Iran, near the town of Abadeh (lat. 30° 55 N; long. 53° 13E). This sequence has a total thickness of over 2,650 m, or approximately 8,692 ft.

The units of the Abadeh sequence appear to be transitional and continuous. Artinskian and Guadalupian fossils, mostly fusulinids, are present in the lower part of this section. In the middle part, grey and red limestones (41.3 m or 135.7 ft thick) compare closely with the Dzhulfian and the Permian-Triassic passage beds of the Dzhulfa (Julfa) region of Soviet Armenia, which is the type section for the Dzhulfian Stage. The upper part of the Abadeh sequence represents the Lower Triassic Claraia Beds, locally known as the "calcaires vermicules facies". The section concludes with over 780 m (2,558 ft) of dolomite, tentatively assigned a Lower to Middle Triassic age by the author.

Because of the close proximity of the well-known Dzhulfa section, a detailed correlation between it and the Abadeh section has been attempted. This correlation has established that the fossil zones in the Dzhulfa region, attributed to the Dzhulfian, passage beds and lowermost Triassic, are also present in the Abadeh section. The main difference between the two sections is a lithological one, the Dzhulfa section comprising mainly shales, while the Abadeh section consists of marine limestones. In addition, the thickness of the latter section is less than that of Dzhulfa.

A preliminary study of conodonts indicates that the Permian-Triassic boundary lies within the middle portion of the Abadeh section. Conodonts typical of the lowermost Triassic beds of the Salt Range have been found in the Abadeh section, allowing a direct comparison between the two regions.

An abrupt change of facies occurs at the contact of the Claraia Beds with the Paratirolites Beds in the Abadeh section. Detrital deposits, or other evidence of erosion, have not been observed at this contact, and the same situation pertains in the Dzhulfa region. This similarity between the two regions of 1,100 km (683 mi) apart suggests that the sharp contact and abrupt change of facies is due to a sudden climatic change, rather than to a regression and sedimentary gap.

This postulated climatic change led to deposition of dolomitic sediments during Early to Middle Triassic times in central Iran, and it may

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have been the main cause for extinction of stenohaline forms and the appearance of new faunas.

In the Upper Permian subdivision by Glenister and Furnish (1961), the boundary between the Guadalupian and Dzhulfian stages is considered to be transitional. Study of the Abadeh section, however, suggests that there is a gap between these stages at this locality and a section of about 334 m (1,096 ft) of limestones, shales and marls, named the Abadeh Formation, separates Guadalupian from Dzhulfian strata. The author proposes that this formation be recognized as the Abadehian Stage, of pre-Dzhulfian, post-Guadalupian age.

In general, the faunal transition across the Permian-Triassic boundary in the Abadeh section appears to have been gradual, rather than sharp. While the exact delineation of the Permian-Triassic boundary is not discussed in this paper, a chart has been complied to show the fossil zones and occurrences.

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