W. F. Hume — Notes on Russian Geology. 395 



Apparently, however, towards the W. the W. European conditions 

 seem to be mor-e nearly approached. No zones -can be determined. 



5. That the White Chalk and Chalk Marl have no absolute definite 

 relation to each other (White Chalk being sometimes found both 

 below and above Chalk Marl), but that in general the former over- 

 lies the latter. 



6. That the Upper Cretaceous is unconformable to the Tertiary 

 overlying it, and on its S. border rests successively on Arch^an, 

 Jurassic, Permian, Carboniferous, and Archaean. 



7. That a great part of these deposits is overlain by Tertiary and 

 Post-Tertiary deposits. (An important Phosphatic deposit occurs 

 a few feet above the junction of the Tertiary and Cretaceous, 

 extending through the Kharkoff, Poltava, and part of the Kieff 

 and Kursk Governments. 



8. That the Upper Cretaceous does not form one single synclinal 

 basin, but is folded into several anticlinals and synclinals, which are 

 then unconformably overlain by the Tertiary. 



The above, then, are the main general points with regard to the 

 Senonio-Turonian basin of S. Russia. 



For the Cenomanian the following conclusions may be enunciated : 



1. That in the largest number of cases where junction exposures 

 are shown, it is found underlying the above-mentioned beds. 



2. That borings prove it to underlie the Chalk and Chalk Marl 

 at the points of their greatest depth (as at Kharkoff). 



3. That lithologically it is mainly Greensand, and is on the 

 average about 100 feet thick. 



Of late years, however, new problems have come into the field, 

 and new paths have been opened up. The " Challenger" expedition 

 has thrown new light on the Ocean deposits of the present day, and 

 once more interest is turning to that vast Chalk area which lies at 

 our very doors. The homogeneity of the Chalk is fast becoming 

 a myth of the past, and the microscope seems likely to help in 

 unravelling something of the physical geography of that far distant 

 period. 



Hitherto, however, if we mistake not, the efforts in this direction 

 have never been undertaken on a large scale, unless, perhaps, 

 exception be made in the case of M. Cayeux's researches on the 

 Senonian and Turonian of the Nord. The attack has in other cases 

 been mainly made on Chalk containing more or less phosphatic 

 material. The problems maybe discussed perhaps a little as follows: 



1. What are the actual residues left after solution of the calcareous 

 portion of the Chalk ? 



2. How far may those fragments reveal their own origin, and so 

 throw light on the causes which brought them into their present 

 position ? 



The researches of M. Cayeux on the Dieves of Liege (Soc. Geol. 

 du Nord. Annales, vol. xix. 1891, 2^ Livr), may well serve as a basis 

 for further experiment in this direction. 



Statements, however, as to the contents of the Chalk residues 

 in the Tchernigov Governments are to be met with in Professor 



