CORRELATIVE REFERENCE LEVELS OF THE PERMIAN

The analysis of Permian biotic and abiotic events has revealed a serie s of contrasting global biostratigraphic levels, to which significant changes in faunal assemblages are confined. The most important among t hem-the ''Kungurian,'' Kubergandian (Roadian) and Djulfian stages-are related to transgressions, the Kungurian being also associated with a large-scale paleogeographic reorganization. The global character of th ese transgressions and related biotic changes are caused most Likely b y eustatic sea level fluctuations. The most significant changes in the Permian biota, which showed up differently in basins of the Boreal an d Tethyan realms, occurred in the early ''Kungurian'' time. The Kuberg andian (Roadian) Stage is associated with a wide geographic distributi on of the Roadian ammonoid assemblage, which includes the Ceratitida o rder, and the simultaneous appearance of Mesogondolella nankingensis. The Djulfian Stage is characterized by the extinction of almost all hi gher fusulinids, the mass development of aberrant genera, the appearan ce of araxoceratids, and substantial changes in the evolution of coral s, brachiopods and other faunal assemblages. Levels of a lower order a re also established. One of them corresponds to the maximum developmen t of the mid-Permian transgression (the Neoschwagerina craticulifera-A fghanella schencki Zone in the Tethys and its analogues in other areas ) and marks the appearance of the Wordian ammonoid assemblage. The mid -Midian level coincides in time with the boundary of the Kaiama and Il lawarra paleomagnetic hyperzones and is marked by the appearance of th e Capitanian zonal genus Timorites. The stages revealed here represent reference levels, which allow wide correlations to be made.