SECTIONS ON THE VOLGA — KOSTROMA TO NIJNI NOVOGOROD. 179 
inarlstone, and some courses of sandy mottled flagstones, which from their concre- 
tionary tendency, run into the form of pot-stones, are covered by Jurassic shale, 
with Ammonites, Belemnites, &c. So conformably does the Jura shale here repose 
on red and green marls, that when we first saw this section (1840), we were led to 
consider the latter as the Keuper ; but a further examination of the banks of the 
Volga below this point, by Pies to Kineshma and Yurievetz, convinced us that, on 
the whole, the surface of the red deposits is uneven and irregular, the Jurassic 
shale being at one spot on the level of the river, and at other places high above the 
red marl. We therefore concluded (independent of the non-existence of Lias in 
Russia), that there was no regular sequence of deposits, but, on the contrary, that 
a long interval had elapsed between the respective accumulations of the red ground 
and the black Jurassic shale. 
At Christof on the Volga, below Yurievetz, and a little above the small town of 
Katungo, the marls fold around and dip away from a great concretionary mass 
of white limestone, which rises through the strata, to at least fifty feet above 
the stream. This limestone, which is almost pure white, is of subcrystalline 
structure, with a splintery and conchoidal fracture, contains here and there im- 
pure smaller concretions of marl and less pure calcareous matter, and in parts 
assumes a laminated structure. Slickenside polish and scratchings are frequent 
on the sides of the joints, which, together with the convoluted broken condition 
of the adjacent marls, through 
which the calcareous mass pro- 
trudes, demonstrate the great 
power of concretionary action in 
modifying the form of strata, 
and in producing all the appear- 
ances of upheaval and disloca- 
tion from beneath. Associated 
with this concretion are courses of rose and white coloured gypsum, numerous red 
and white, small, calcareous concretions, and occasionally brown and red calcare- 
ous grits, in which we searched long and fruitlessly for traces of organic remains. 
Some of the beds are micaceous, and thin courses of irregular concretionary flag- 
stone are to be detected. 
At Balachna, still lower on the Volga, the red and green marls with gypsum, 
give rise to copious salt-springs, in the deepening of which the strata have been 
30 . 
