CRETACEOUS ROCKS OF KHARKOF. 
267 
to the north, we must specially revert to the admirable section at Izium on the 
river Donetz (p. 252). There, as above remarked, is seen a clear order of super- 
position, which shows the upper Jura limestone or coral rag covered, by light- 
coloured sandstone and sand with green grains, inclosing thin courses of marl. 
These beds pass upwards into porous sandstone with tripoli, the whole of this low ei 
cretaceous or greensand group, of about 70 feet in thickness, being surmounted by 
pure white chalk. 
SECTION AT IZIUM. 39 bis. 
m. White chalk * 
1. Hard quartzose grit, with siliceous cement 
k. Sandy clay, 
j. Green sandstone, with siliceous concretions. 
i. Porous light-coloured sandstone, with tripoli and yellow sand. . 
h. Grey sandstone and sand, with green grains and courses of marl . 
g. Three beds of limestone, with small univalves and Nerinaa. 
f. Fine-grained oolite in a base of compact limestone 
e. Soft yellow limestone, with Gervilliat 
d. Limestone, very hard and compact, slightly translucent, occasionally con- 
taining gypseous courses and a few fossils 
c . Marls and shelly agglomerates, with Trigonia clavellata and Cida - j 
b. Band of fine oolitic structure 
a. Beds obscured by alluvia. Sands with plants. 
Level of the Donetz 
The structure of the country in the governments of Kharkof and Kursk con- 
vinced us, however, that thick as it may be at Lugan and in the upper steppe of 
the Don Cossacks, the white chalk dwindles out to one thin bed in the adjacent 
regions upon the north, and plays a very subordinate part only, amid argillaceous 
and siliceous masses which there represent the Cretaceous system. 
The important and flourishing city of Kharkof 1 stands in the centre of deposits 
which, from their light colours alone, might lead to the impression of their being 
cretaceous ; for, consisting of whitish, greenish, and light yellow argillaceous beds, 
which, at first sight, very much resemble chalk marls, they become white in 
weathering, and leave chalk-like streaks when rubbed upon any other substance. 
This rock is, however, nothing more than one of the varieties of a deposit we shall 
in the sequel describe, as existing in great force on the banks of the Volga and the 
Don • being a very light, minutely micaceous and fine-grained earthy sandstone, 
which derives its colour and character from a large proportion of white felspar. It 
contains no lime, at least in most places, it does not effervesce with acids, and is 
• This city, little known in Europe, contains an university and a population of upwards of 40,000 
persons. 
