172 
GYPSIFEROUS ROCKS OF THE PINEGA. 
The rocks which are exposed in ascending the river Dwina from Archangel to 
Ustiug-Veliki, a distance of about 600 versts, exhibit, with some modifications, a 
succession similar to that which has been described in proceeding from the western 
flanks of the Ural Mountains to the interior of the governments of Orenburg and 
Kazan. The great band of carboniferous limestone which traverses the Dwina 
above its embouchure, has already been spoken of, and our first point is to show T , 
that it is succeeded by newer formations on the south 
In our journey up the banks of the Dwina, we naturally met 
with newer deposits ; for even supposing that the strata, partaking of the very 
great flatness of this region, were entirely horizontal, still in ascending this great 
river for several hundred miles, we inferred, that as we gained a higher level, so 
should we arrive at newer formations. The stream is, indeed, known to have a 
pretty rapid descent, and Ustiug lies at about 300 feet above the sea. While one 
of our parties examined the coasts of the White Sea 1 , the other (so limited was our 
time) explored the river Pinega or eastern tributary of the Dwina 2 . 
Section of the Pinega . — We will first briefly describe the order on the Pinega. 
In ascending this river, extensive masses of carboniferous limestone, with Productus 
antiquatus, appear at intervals through the drift and sand, and are succeeded at 
the village of Uksenskaya, by other bands of the same limestone in which many 
other carboniferous fossils occur. Although we had not leisure to ascertain the 
fact, we think it is highly probable that, by exploring the picturesque adjacent 
gorge of the Tinga, a junction might be detected between those carboniferous 
rocks, there very much developed, and certain overlying gypsiferous strata which 
we class with the Permian system. The road, as is usual in Russia, being carried 
over the higher ground and the river flowing in an alluvial valley filled with much 
detritus, we were prevented, throughout a space of about twenty-six versts, from 
tracing all the links of succession ; but on rejoining the stream we observed, at four 
versts beyond the station of Kuzomenskaya, large masses of gypsum occupying the 
Clift's, to heights of thirty or forty feet. We ascertained that this gypsum, having a 
small course of limestone subordinate to it, is continuous from this point (fifty- 
five versts south-west of Pinega, to twelve versts above that town), and we have 
no doubt that it spreads over a considerable region to the north-east. At two 
or three versts above the station of Beschkom, on the right bank of the river, 
the gypsum, in the form of brilliantly white alabaster, forms cliffs, and alternates 
1 Mr. Murchison and Count Keyserling. 2 M. de Verneuil and Lieut. Koksharof. 
