The Upper Permian (presumably Tatarian) deposits of the basins of the middle and lower reaches of the Lena and Aldan rivers, and also of the upper reaches of the Jana and Indigurka rivers are overlain without visible break by Induan strata assigned to the Otoceras Zone (according to Abramov, Vosin and Korobitsyn). Characteristic of the uppermost Permian beds (Imtatshan Formation) are abundant Strophalosia, Neospirifer invisus and rare Cancrinelloides obrutschevi. The complete extinction of the brachiopod subfamily Licharewiinae also occurs at this stratigraphic level.

While the Imtatshan Formation and the Doulgalakh Formation are generally recognized as the highest stratigraphic units of the Permian in eastern and western Verkhoyan, respectively, authors Andrianov, Arkhipov and Korostelyov stress that the correlation of these formations with the Tatarian Stage of the Fore-Urals and the Dzhulfian Stage of Transcaucasus is still tentative.

Complete sections of the Lower Triassic are known from the basins of the Tompo and Delinja rivers of eastern Verkhoyan, where Triassic deposits overlie Permian strata without visible disconformity. In other

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regions of Verkhoyan, stratigraphic breaks from the base of the Triassic up to the top of the Induan Stage have been established. The systemic boundary is drawn at the base of the Otoceras boreale Zone, above which Andrianov, Arkhipov and Korostelyov have recognized, in ascending order, the zones of Episageras dalailamae, Glyptophiceras pascoei, Pachyproptychites strigatus, and Pachyproptychites turgidus.

East of Verkhoyan, in the Ochotsk Massif and the Kolyma area of the Yana-Kolyma folded belt, marine Lower Triassic deposits with ceratitids and bivalves overlie the Permian Khivatsch Beds, which is probably a marine development of the Tatarian Stage. Zavodovsky believes this contact to be a conformable one, but according to Bytshkov, the fauna of the Otoceras Zone has not been discovered in this area and the exact stratigraphic position of Epiageceras and Pachyproptychites, recorded from the headwaters of the Upper Garmanda River, is uncertain. A continuous sequence from the Permian to the Triassic may exist in the upper reaches of the Kulu and Tenke rivers (Upper Kolyma region), where the Upper Permian deposits of the Khivatsch Beds, consisting of sandstones, conglomerates and shales with Nuculana magna, Kolymia, Bellerophon and Rectoglandulina gigantea, are overlain by a shale-sandstone sequence containing Conchostraca of Induan age. This sequence is followed by clay deposits with Ophiceras and Glyptophiceras ex gr. extremum. A continuous section of Permian-Triassic strata may also be demonstrated in the interior region of the Omolon Massif, where a 15-50m (approximately 48-164) limestone sequence contains the Khivatsch fauna in the lower levels and numerous Posidonia mimer and rare Hedenstroemia and Paranorites in the upper levels.

In other regions of the northeast U.S.S.R. there is a stratigraphic break at the Permian-Triassic boundary and the Upper Permian is overlain by various horizons of the Lower, Middle and Upper Triassic.

In the Transbaikal region and in the extreme eastern part of the Soviet Union, Permian-Triassic boundary beds are poorly developed. In Transbaikal, laminated siltstones with Ophiceras and Gyronites are in tectonic contact with Lower Paleozoic rocks. In the area of the middle Amur River, Upper Permian sandstones with Schizodus and gastropods are succeeded by laminated siltstones with Glyptophiceras, Metotoceras (?) and Posidonia. In the Uda River Basin, the relationship between Olenekian siltstones and the underlying beds is uncertain, while in the southern maritime region a marked stratigraphic break separates the upper part of the Upper Permian and the lower part of the Lower Triassic, with beds containing Gyronites overlying different horizons of the Upper Permian.

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