Nos-Gora (Saraktashsky District)

Nos-Gora (also known by its Turkic name, Kurmain) is a ridge-shaped hill on the right bank of the Sakmara River in Saraktashsky District, Orenburg Oblast, Russia, near the village of Kondurovka. A cliff section exposed on the mountain is regarded as the stratotype of the Sakmarian Stage of the Permian System, which is why the site is known among geologists worldwide.

Research history

In 1874 the section in the Nos-Gora cliff was first described by academician Alexander Karpinsky, who also gave it the name "Sakmarian", after the Sakmara River. In 1936 the palaeontologist Vladimir Ruzhentsev, after a thorough study of the fossil fauna, established the Sakmarian Stage as a distinct subdivision of the Permian System. The site's scientific importance was confirmed again in 1991, when it was visited by an excursion of the International Geological Congress devoted to the Permian System.

Relief, name and geology

Nos-Gora is ridge-shaped, stretches for 3.5-4 km and rises to 385 m. Its Turkic name, Kurmain, translates as "narrow neck"; the Russian name ("Nose Mountain") comes from a limestone ledge at its southern end that, in profile, resembles a human nose.

The eastern slope and summit are built of platy limestones of the Kurmain formation of the Asselian Stage of the Permian. On the southern and south-western slopes, limestones and sandstones of the Sakmarian Stage alternate in layers; accounting for the folding, their combined thickness in the section reaches about 900 m. The layers contain fossils of the Sakmarian fauna — shells of brachiopods, pelecypods and ammonites, remains of bryozoans and sea lilies, and microscopic shells of fusulinids and radiolarians.

Karst and Chyortovo Lake

The limestones of Nos-Gora show present-day carbonate karst: traces of leaching are visible on the surface of slot-like cavities and niches. At the southern end of the mountain lies the karst Chyortovo Lake ("Devil's Lake"); in 1976 its depth was about 8 m, but it has since become noticeably shallower due to siltation.

Getting there

Nos-Gora is the sixth stop on the "Seven Peaks of the Steppe Urals" tourist route. The nearest landmark is Kondurovka railway station, about a 30-40 minute walk from the foot of the mountain.