Mat 28, 1920] 



SCIENCE 



541 



DISCUSSION AND CORRESPONDENCE 



" PETROLIFEROUS PROVINCES " 



In a discussion of Petroliferous Provinces in 

 a recent number of Mining and Metallurgy,'^ 

 Dr. Charles SciLucliert has quoted from an 

 article on " Some Factors in the Geographic 

 Distribution of Petroleum "^ by the present 

 writer, and has dra-wn certain conclusions and 

 made certain inferences which are decidedly 

 at variance with the ideas the author intended 

 to convey. In order that some of the appar- 

 ently ambiguous statements in the article on 

 Geographic Distribution should not be gener- 

 ally misconstrued, it is desired to call atten- 

 tion to certain points which the reviewer has 

 apparently overlooked. 



Dr. Schuchert says: 



Since the previous paragrapli was written there 

 appeared the suggestive paper by Mehl, already 

 cited, in Tvlhieh he points out that all the major oil 

 fields of the world are situated between 20° and 

 50° north latitude. Further, that there are no 

 major oil areas within the tropics or in *he south- 

 ern hemisphere. As the known major oil fields lie 

 between the present isotherms of 40° and 70° F., 

 he tihinks that this distribution "does suggest a 

 distinctly zonal distribution of petroleum in which 

 temperature may have been an important factor. ' ' 

 The question that here arises is. Is this suggestion 

 of present climatic conditions also true for the 

 times when the oil was deposited in the strata in 

 which it is now found, remembering that the oil 

 fields were not made recently but are the accumu- 

 lations of hydrocarbons of the seas of geologic 

 ages? The answer is not at all in harmony with 

 Mehl's suggestion, for we are living dn an excep- 

 tional time of stressed climates and marked zonal 

 oonddtions, while the mean temperature conditions 

 during the geologic ages were warm and equable 

 throughout most of the world, and this is even 

 m'ore true of the tem,p'erature of oceans than of 

 the lands. 



The paragraph that called forth this com- 

 ment follows: 



1 Bull. Amer. Inst. Mining and Metallurgical 

 Engineers, No. 155, pp. 3058-3070, November, 1919. 



2 Bull. Scientific Laboratories, Dennison Univ., 

 Vol. XIX., pp. 55-63, June, 1919. 



Attention da further called to the general corre- 

 spondence between the position of the twentieth 

 and fiftieth parallels in both hemispheres with the 

 average annual isotherms of 70° and 40° respect- 

 ively. Although these parallels are, in reality, 

 nothing more than imaginary lines of geographic 

 references, each does, in much proiaiility, marTc 

 the average position of some isotherm as it has 

 shifted in past geologic times. While the disposi- 

 tion of maximum accumulations as here bounded 

 does not indicate a definite temperature zone within 

 which petroleum has been formed, it does suggest 

 a distinctly zonal distribution of petroleum in 

 which temperature may have been an important 

 factor. 



There follows a few paragraphs further on: 



Very often the rapid decay of organisms is 

 pointed to as illustrating the manner in whieih pe- 

 troleum is formed. In certain parts of the Medi- 

 terranean Sea, for instance, the accumulation and 

 decay of organic detritus is so rapid that the lower 

 levels of the water are filled with scattered globules 

 of oil. Instead of illustrating how petroleum is 

 formed, however, it points to the effective manner 

 in which fatty matter is ordinarily separated 

 out from accumulating sediments. Certainly, the 

 gloiules which are escaping into the water offer 

 no suggestion of being retrapped and converted 

 into petroleum. It is only that part of the or- 

 ganic matter which is converted into oil so slowly 

 that the accumulating sediments form a sufiS.eient 

 thickness and suitable succession to retain it against 

 the tendency of the associated waters to drive it 

 off, that may become petroleum. 



So much has been added to our knowledge 

 of the climates of past geological ages by the 

 work of Dr. Schuchert and others that it does 

 not seem appropriate, in an article not in- 

 tended primarily for the beginning student in 

 geology, to call attention to the fact that the 

 present average annual isotherms are not nec- 

 essarily coincident with the same isotherms 

 throughout past geologic periods. Further- 

 more, it would appear that one might logically 

 take for granted a general knowledge of the 

 principles underlying temperature zones and 

 the nature of their boundary lines as follows: 



1. The sinuosity of isotherms is determined 

 largely by the 'extent of the land masses and 

 their configuration. 



