The absence of a one-time inland-ice-cap differentiates the Ukrainian district very markedly from the other parts of Eastern Europe. As we perceive, even from this short description, the Ukraine has had an entirely different geologic history from the rest of Eastern Europe.
More plainly still, the independence of the Ukraine as a natural unit is revealed in its contour-line and surfacerelief. The Ukraine is the only portion of the Eastern European plain which has access to the mountainous region, for it rests upon the Carpathians, the Yaila Mountains and the Caucasus. Important individual districts of the Ukraine lie in these mountains and lessen the Eastern European uniformity of the country. The formation of the Yaila and the Caucasus began at the end of the Jurassic period — its completion and the building up of the Carpathians occur in the late tertiary period.
The plains and plateau of the Ukraine, while at first glance quite similar to those of Central Russia, are in reality very different from these as to structure and surface-relief. The nucleus of the Ukrainian plateau group, which is surrounded by the two plain districts of the Ukraine, consists of the so-called Azof Horst (so named by E. Suess), which stretches from the banks of the Sea of Azof in a northwesterly direction as far as Volhynia and Austrian Podolia. This primeval rock surface, composed of granite gneiss, is bounded by quarries and edged with declivities, which are hidden by more recent sediment deposits. Since this extended Horst stretches thru practically the whole length of the Ukraine, we shall call it "the Ukrainian Horst."
This Ukrainian Horst is of great importance for the entire process of folding, all over the earth. To the west of this Horst is the immense fold-system of the Altai, folded far into North America toward the north and northeast, in direct opposition to the main parts of the enormous system which lie to the east of it. In the east of the Horst we see the straight line of the mountain system of the Caucasus; in the west the winding guide-lines of Central Europe.
The region of the Ukrainian Horst has influenced not only the formation of the plicated country. In connection with it we find, arranged on a grand scale, but not very intensive, disintegrating lines, which traverse the entire Ukrainian country from N. W. to S. E. These tectonic disturbances have led to strong folding and dislocation of the more recent sedimentary layers which lie close to the Horst. This folding district can be observed only in the trunk range on the Donetz and in a few isolated places to the northwest; beyond this it is buried under the huge cover of the tertiary layers. The folding process took place in the Donetz Mountains, continuing with long interruptions from the end of the paleozoic era to the beginning of the tertiary period. As pre-tertiary disturbances of this kind we consider the disturbance of Isatchky, Trekhtimirov, etc., as well as some dividing lines at the northwestern extremity of the Ukrainian Horst.
There is no doubt that the Ukrainian Horst was also the origin of more recent tectonic disturbances — tertiary and post-tertiary. The two main lines of Karpinsky (the northern — Volga, bend of the Don, source of the Donetz, delta of the Desna, South Polissye, Warsaw; the southern — delta of the Don, end of the Porohy of the Dnieper, source of the Boh, Western Podolia) for the most part go back to these more recent post-cretaceous disturbances. Besides, we are already able, despite our insufficient morphological data on the Ukraine, to establish the fact that the entire Ukrainian plateau-group is the scene of a significant post-glacial elevation. The strikingly parallel courses of the main streams, the Dniester, the Boh, the Dnieper as far as Katerinoslav, the Donetz and the Don, together with the precipices frequently accompanying them, lead us to infer the existence of tectonic influences. That the precipices of Podolia are very recent we may now confidently maintain, and that the precipitous bank of the Dnieper is quite as recent is shown by the familiar dislocation near Kaniv, where the tertiary is affected. Seismic movements of the most recent past and morphological observations show us that the tectonic disturbances of the Ukraine are continuing into our own day. From this tectonic characterization of the Ukraine we perceive that this country occupies an independent position in relation to the rest of Eastern