JURASSIC DEPOSITS OF ORENBURG. 
247 
Though we had no time to seek for many fossils, our readers cannot fail to per- 
ceive in this section a close analogy to the succession at Moscow and other places, 
and will readily admit with us, that as at the ancient metropolis and at Inkino on 
the Oka so at Saratof, ferruginous and white sands form the upper part of the de- 
posit. We shall presently see how these sands connect the strata we have been 
considering with the next overlying formation in the south of Russia. 
Eastern tract of Jurassic Rocks.— It is a remarkable proof of the value of pale- 
ontological evidence, in identifying strata before they have been examined by field 
geologists, that certain fossils sent to M. Yon Buch from the government of Oren- 
burg, enabled him anterior to our visit, to assert that the same band of Jurassic 
rocks which occurs at intervals in the plains of Russia and near Berlin, appeared 
also in the steppes which lead from Europe into Asia. Whilst our own observations 
completely confirm this view, we must state, that however uniform is the com- 
position of the rocks of this age in the central and northern regions of Russia, yet 
as they approach to the Ural chain and the Asiatic steppes, they put on lithological 
characters dissimilar from their ordinary matrix. The higher grounds which rise 
above the cupriferous strata of Kargala and the Saragula Hills, are covered by 
very siliceous beds, in which the same Jurassic fossils as at Moscow, such as 
Ammonites cordatus and Gryphaa dilatata, occur in nearly pure silex. On the 
river Vitlanka, not far from the salt mines of Illetzkaya-Zastchita, the same forma- 
tion is well seen in open quarries of about fifteen feet in depth, where the stone is 
of light yellow colour, sonorous under the hammer, and is composed of minute, 
white siliceous grains cemented in a calcareous paste, which still more prevails in 
other beds which become calcareous grits. Here are again found fossils which are 
common in the Jurassic shales of Moscow, such as a Lima closely allied to . 
proboscidea, Ammonites cordatus , &c. &c. In two ridges, called Tatchi noi ora an 
Jornavoi Kamen, the same rock becomes a complete siliceous grit, an is even 
quarried for millstones and grindstones. Near the fort of Isabelnoi upon t le c , 
similar beds occur and have furnished osseous remains, which we did not see, 
but probably belonging to a large Saurian ; and they are also seen at the sources ot 
the river Kamenko on the slope of the Obstchey Syrt, forty versts north of the fort 
We may here remark, that the surface of these Jurassic districts is often covered 
with rolled pebbles of white quartz and Lydian stone, both on the river Vitlanka and 
on the adjacent hills, and among this detritus are large blocks of quartz. Near the 
small river Tchorni Retchki, to the north of Novo Uletzkaya, we discovered beds ol 
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