390 W. F. Hume — Notes on Russian Geology. 



a time, the Chalk reaches the surface in the neighbourhood of Tzium. 

 Here, as shown by Murchison, the Chalk is 30 feet thick; under- 

 neath these are greensand beds 70 feet thick, and then come 44,feet 

 of Upper Jurassic beds. As this spot is 70 miles S.E. of Kharkoff, 

 and no other Jurassic outcrop occurs between the two towns, it is 

 probable that the Chalk slowly thickens towards the North. 



Further to the S. a splendid display of the Upper Cretaceous 

 and its subjacent beds occurs at the great monastery of Sviati Gori, 

 in the fine escai'praent overlooking the Donetz. The upper 300 feet 

 consists of a somewhat coarse chalk, containing layers of flints. 

 Below it occurs a large mass of somewhat fine greensand, which 

 yielded no fossils to our research. It is well displayed in the 

 winding road down to the river. I was unable to obtain sufficient 

 evidence as to its exact thickness. It was certainly at least 15 to 

 20 feet. As will be seen, this greensand occupies an enormous area, 

 and very probably belongs to the Pecten asper zone (Murchison).^ 



Variegated clays separate the greensands from the Jurassic lime- 

 stones which form a second low clifi" near the river. These beds 

 are practically unfossiliferous, although strata of similar lithological 

 character at Shilovka, near Simbirsk, yielded Amm. consobrinus to 

 the researches of M. Jasikofi" (see Murchison), and they may perhaps 

 like them be referred to "couches superieures Neocomiennes " of 

 D'Orbigny. 



Thus a comparison gives : 



Kharkoff. Izium.^ Sviati Gori. 



Tertiary, 133 ft. 

 Chalk aud Chalk Marl. Chalk. "Whitish Chalk (about 300 ft.) 



(1831ft,) (30 ft.) 



Green and grey sands. Greensand (70 ft.) Greensand (Pmore than 20 ft.) 



Same alternating with Variegated clays. 



dark clays. 



Jurassic Limestones. Jurassic Limestones. 



From Sviati Gori the Chalk area extends unbroken 20 miles to 



the south at Kramatorovka. The whole of the country between 



these two points consists of undulating steppe, the understratum 



of chalk being barely concealed by a thin covering of grass, whilst 



^ It may be noted that the repetition of the Jurassic Strata at Sviati Gori, at 

 Kamenka, and at Tzium, is regarded by Prof. Gourov as being due to a succession of 

 faults. It again raises the question how far parts of the courses of important rivers 

 have been determined by such movements of the earth's crust. Prof. Gourov has 

 shiiwn the existence of Jurassic limestones not far from Poltava, so that it is 

 probable that Upper Cretaceous beds do not extend far to the S. of that town. 



- At Fedorovka, in the Izium district, a boring by Messrs. Winning, has shown 

 the existence of 451 feet of variegated, green, and red clays, which probably belong 

 to the same category as those mentioned above. At a bore between Barvenko and 

 Stavrikov, in the valley between the stations of Gavrilovka and Slaviansk, the 

 beds vary remarkably in their lithological character. For the first 50 feet variegated 

 aud bro-mi clays predominate ; the next 150 feet are sands and sandstones. For the 

 next 100 feet there is contest between the clays, sandstones and limestones, the latter 

 forming two or three bands 6 ft. thick, separated by wide intervals. The remaining 

 228 feet are almost entirely variegated brown clays. It is possible that these beds were 

 deposited near a shore line, the sea, in which the Oolitic limestone of Sviati Gori 

 was laid down, occasionally reinvading the district. Subsequently the clays them- 

 selves invaded the Jurassic sea, and covered the limestones, as at Sviati Gori. 



