OCEANIC DEPOSITS IN THE UST-URT. 
325 
the cities of Volsk and Sysran, and probably communicating with the same de- 
posits in the large steppe of Astrakhan, ranges northwards to the junction of 
the Motsha and Kundurstsha rivers. The northern Aralo-Caspian tract, called 
by M. Jasikoff the “ Basin of Bulgar,” is, according to him, quite insulated and 
separated from that of the south by the carboniferous rocks described p. 85, 
which form the promontory of the Volga near Samara, and by the Permian deposits ; 
from whence it ranges northwards on the left bank of the Volga beyond Simbirsk, 
to the environs of Tetushi and Spask. Throughout these tracts, which are sandy 
steppes, reposing, as we believe, upon our Permian rocks, M. Jasikoff has found 
the Mytilus polymorphus and other Aralo-Caspian shells, and has thus added proofs 
of another arm, perhaps a detached bay or fiord ?, of a former Caspian Sea, into 
which the Volga of that day emptied itself in 55° north latitude (see Map). 
Oceanic Deposits in the Ust-Urt. — Uncertainty as to the real Level of the Aral Sea . — 
In the absence of any geological survey of the Ust-Urt or wild plateau between 
the Caspian and the Aral, the description of its southern portion by Captain Abbott, 
the presence of a shell described by Eichwald as Cyclas Ust-uertensis, as well as the 
account of the monotony of the tract given by the party which accompanied Gene- 
ral De Berg (see p. 310), have all led us to infer, that the older Caspian deposits 
which unquestionably form the cliffs of the Sea of Aral as well as of the Caspian, 
extended continuously over the whole tract which rises to a maximum height of 731 
feet. An excursion to St. Petersburgh since the preceding sheets were printed has 
induced Mr. Murchison to modify this opinion. After inspecting certain fossils 
collected on part of the higher grounds of the Ust-Urt by M. Basiner, to whom 
allusion has already been made, and submitted to him by Colonel Helmersen, he had 
no hesitation in agreeing with the latter, that these shells and the oolitic marly lime- 
stone in which they occur are of oceanic character, and synchronous in age with the 
uppermost Miocene deposits of Podolia, Bessarabia, and Taganrog already alluded to. 
According to M. Basiner, these beds appear to have been upheaved into a plateau, 
which formed the western shore of a former Aral Sea. In our view, which sup- 
poses the previous union of that sea with the Caspian, we would suggest that these 
upraised oceanic deposits may have constituted an island in the great Aialo-Cas- 
pian brackish sea. Future surveys must determine this point, and decide whether 
the earliest Caspian waters may have communicated with those of the Aral by a 
northern strait ; for to the south there must have been a communication over the 
low steppes and one of a very broad character. In the mean time, the facts before 
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