98 Jules Marcou — The Permian- Trias Question. 



spot, of the size of a pea, north-east of Astrakan at the Grand Bogdo 

 Mountain. 



On his Geological Map of Europe, in collaboration with James 

 Nicoll, 1856, in four sheets, Murchison colours and marks with the 

 letter e as ' Permian ' all the rocks in Kussia between the Carbon- 

 iferous and the Jurassic, excluding even the Trias of Mount Bogdo, 

 with the remark however, inscribed under the word Grand Bogdo : 

 "Limestone with Trias fossils on Saliferous Sandstone." 



The two general Geological Maps of Russia published at St. 

 Petersburg by Colonel Ozerski in 1849, and by General Helmersen 

 in 1863, reproduce the geographical distribution of the 'Permian' as 

 it was delineated by Murchison, with a few alterations near the foot 

 of the north-eastern part of the Ural Mountains. 



The first general Geological Map of Russia, after Helmersen's of 

 1863, is Valerien de Moeller's Carte des gites miniers de la Eussie 

 d^Enrope, 1878. Here we have a map differing entirely, as to the 

 distribution of the Trias and ' Permian,' from those previously 

 quoted. Instead of the single small spot of Trias of Mount Bogdo, 

 we have an immense surface, twice as large as England and Scot- 

 land together, coloured as Trias, while the ' Permian ' is so much 

 diminished in size, as to occupy only a very modest place, along the 

 western foot of the Ural Mountains and at a few spots along the 

 Volga river, also east and north of Moscow, and near Mittau in 

 Courland. In fact, the ' Permian System ' in the map of Moeller, 

 1878, plays a very secondary part in the geology of Russia. 



In a special Geological Map of the Ural Mountains, entitled 

 Carte geologique du versant occidental de VOural, published in 1869, 

 M. Valerien de Moeller gave already an entirely different view of 

 the geographical distribution and stratigraphical section of the so- 

 called 'Permian Series.' For not only M. de Moeller admits fully 

 the existence of the Trias, over immense surfaces precedently 

 coloured as ' Permian,' but he divides the rocks placed between the 

 Trias and the Carboniferous into two great groups, one formed of 

 Limestone with marls, slates, gypsum and salt, and the other of 

 Sandstone, conglomerate, copper grits and coal ; in fact, M. de 

 Moeller's ' Permian ' is a regular Dyas, somewhat similar to the 

 Dyas of Central Germany. 



How such a great change came about requires a few words of 

 explanation; for it seemed according to Murchison that we have 

 in Russia a type of a formation badly defined in Germany and in 

 England, and that for the first time himself and his associates 

 De Verneuil and von Keyserling had found in the great Russian 

 Empire, and more especially in the Government of Perm, proof of 

 the existence of a great series of rocks, which he offered to geologists 

 as a typical formation, under the title of the ' Permian System.' 



The publication of my memoir, entitled Dyas et Trias, at Geneva, 

 in 1859, first attracted attention to the difficulties and even impossi- 

 bilities of accepting such a type, so far from Central Germany and 

 the classical ground of Thuringia in Saxony; and with such an 

 unsatisfactory description as the one contained in Bussia and the 

 Ural Mountains. 



