112 SESSION I, DISCUSSION 



gcochcmical facies sometimes diminishes and sometimes increases, at times rcacliing 

 more than i",,, as for example, in the rocks of the Rudkinsk horizon of the Frasnian. 



At the same time the qualitative composition of the bituminous substances syngenetic 

 with the sedimentary rocks is determined mainly by gcochcmical conditions and also 

 changes vertically though they arc continuous throughout the territory. As analysis 

 of the palaeogcographic conditions has shown, the rocks of the Morsovo and Dankovo- 

 Lebedyan horizons of the middle and upper Devonian, which were mainly laid down 

 under the conditions of saline lagoons in reducing circumstances favourable to the laying 

 down and transformation of organic substances, arc characterized essentially by a reduced 

 type of bituminous substances. 



In the rocks of the Upper Givetian of the middle Devonian, which were laid down 

 under shallow-water conditions, i.e. under conditions which were not favourable for the 

 accumulation and transformation of organic substances, we find either a complete absence 

 of bituminous substances, or bituminosities of an acid character. 



The factual material which has been brought forward concerning the study of the 

 present distribution of bituminous substances is evidence that the bituminous material 

 found in a scattered form in sedimentary deposits is found in the very deposits (or in their 

 immediate vicinity) where the gcochcmical conditions were favourable for the laying 

 down and transformation of organic compounds of animal and vegetable origin. The 

 bituminous substances in the scattered form which are contained in the rocks of the 

 sedimentary complex which was studied are therefore, in the first place, syngenetic 

 with the deposits in which they lie and, in the second place, they are undoubtedly of 

 biogenic origin. This is indicated by the numerous finds of remains of animal and plant 

 life in these rocks. 



As concerns the more ancient rocks of the crystalline foundation, it must be stated 

 that no traces of vital activity have been found in them. 



The question arises as to the source of the bituminous substances which have been 

 foimd in the rocks of the foundation. 



One hypothesis, based on the possibility that bitumens of biogenic origin might have 

 migrated downwards from the overlying sedimentary strata into the foundation, seems 

 vmtenable in that it is inconsistent with the possible rate of their migration from the less 

 dense sedimentary deposits into the denser igneous rocks of the foundation. Further- 

 more, if this were correct, it would be impossible to explain those cases in which the 

 distribution of bituminous substances is such that their concentration in the rocks of the 

 foundation is greater than in the sedimentary rocks immediately overlying it, for migration 

 from areas of low concentration to areas of higher concentration cannot occur. 



All this suggests that the bituminous substances found in the metamorphic rocks of 

 the foundation were either formed in the metamorphic rocks themselves, or else that 

 they migrated into these formations from the magmatic focus by cracks and fissures. 



Both of these suggestions imply that the bituminous substances found in the crystalline 

 foundation were of completely abiogenic origin. 



As concerns the view that bituminous substances migrated out of the foundation into 

 the sedimentary rocks, this idea does not receive any confirmation in the territory under 

 discussion, as there are places in it where bituminous substances are completely absent 

 from the foundation while being present in considerable amounts in the sedimentary 

 layers immediately overlying it. 



In conclusion, it must be remarked that the material produced is evidence of the 

 extensive distribution in the crust of the Earth of bituminous substances in the dispersed 

 form, which also contain a certain amount of hydrocarbons. They are found botli in the 

 strata of the sedimentary complex, and sometimes in the metamorphic rocks of the 

 crystalline foundation. However, analysis of the gcochcmical and palaeogeographical 

 circumstances demonstrates, absolutely convincingly, the independent and separate forma- 

 tion of the bituminous substances which have been discovered in the sedimentary strata 

 and the hydrocarbon compounds of the metamorphic rocks of the foundation. 



The demonstration, over an enormous territory, of bituminous substances in only very 

 minute amounts in the rocks of the crystalline foundation, the impossibility of their 

 migrating upwards to any considerable extent, and also the absence of any appreciable 

 quantity of them, not to speak of the absence of petroleum deposits in the graben of the 

 Vyatsk uplift and on the Tokmovo uplift which are broken into by a large number of 

 deep fractures of the foundation, constitute serious objections to the hypothesis of the 

 inorganic origin of petroleum. 



