STRUCTURE OF THE JURASSIC BASIN OF THE LOWER VOLGA. 245 
the Sura contains a considerable number of them, and they are prolonged to 
the Volga. At Goroditche, below Simbirsk, they appear to lie in the upper part 
of the formation, i. e, above “ Inoceramus sandstone,” like that which has been 
described at Moscow. On the other hand, they are found in the great cliffs of 
Saratof, rather low in the series ; and there they have no longer the form of ellip- 
soids, but more frequently of truncated cones applied base to base. 
One of the most interesting beds of this Jurassic system, at Simbirsk and Go- 
roditche, is the Inoceramus sandstone. This band has already been noticed at 
Moscow, and we now allude to it, to show the remarkable persistence of the same 
strata over wide areas, and also to demonstrate, that all these Jura deposits of Russia, 
however distant from each other, belong to one stage in the series. At Simbirsk this 
sandstone is almost on the level of theVolga, whilst at Goroditche, twenty-five versts 
to the north of this town, it is nearly at the summit of cliffs 150 or 160 feet above 
the stream. This difference of level, in a band of such persistence and which 
marks so distinct a horizon, indicates in the deposits of that tract a regular inclination 
to the south, although it is as imperceptible to the eye as the dip of the Silurian 
and Devonian rocks upon the Volkof (p. 30). But slight as it is, this inclination is 
still adequate to cause the whole of the Jurassic rocks to disappear at some versts 
below Simbirsk, where they are replaced by the chalk, which descends to the water’s 
edge and occupies the river cliffs. The rise of the carboniferous limestone in the pe- 
ninsula of the Volga near Samara (p. 86), again brings to day the Jura beds in the 
neighbourhood of Sysran, and with exceptions they thenceforward form the bottom 
of the valley of the Volga as far south as a promontory below Saratof. Another 
band worthy of notice, because it occurs in several localities and serves to mark a 
fixed place in the deposit, contains beds of combustible matter or lignite, these 
are the bituminous schists of Goroditche ', and of Kaschpoor near Sysran, which 
contain Ammonites and Belemnites described by M. Eichwald, and which Colonel 
Helmersen has shown to re-occur at Ivhvalinsk 2 . 
Sections on the Lower Volga .— We will now give in detail the section of the right 
i The Jurassic shale we have described contains in parts of its range, as we have shown, some courses 
of bituminous schist and impure lignite, notably at Goroditche and at Khvalinslc on the Volga. One of 
the chambered shells from the last-mentioned locality having been described by Professor Eichwald as a 
goniatite these strata were considered to belong to the carboniferous system until we visited the locality. 
As the character of the sliale had led some persons to think that lignites fit for use might be extracted in 
this region, we beg to state, that we dissent entirely from this surmise, and believe that in an economical 
sense the bituminous shale of the Volga is worthless. 
9 See a Geological Map of Russia by Colonel Helmersen, published before we visited these parts, 
anno 1841. 
2 K 
