PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



INTERRELATIONS OF THE FOSSIL FUELS* 



III. 



By JOHN J. STEVENSON. 



(Read November 2, iQiT-) 



THE JURASSIC AND TRIASSIC COALS. 



The Jurassic. 



Like the Cretaceous, this is barren in the greater part of its 

 extent within Europe and the productive areas are of Hmited extent, 

 though some of them are important. Conditions favoring accumula- 

 tion of coal existed in widely separated localities elsewhere, as in 

 Siberia, Australia, New Zealand and Alaska ; in some of which 

 the deposits may prove to be valuable. The geologic features have 

 material bearing upon the problem under consideration in this study. 



Great Britain. — British geologists have grouped the Jurassic 

 deposits into Upper, Middle, Lower Oolite and the Lias. Transi- 

 tion from the Cretaceous is often gradual. Local deposits of coal 

 are in the Lower Oolite and soils of vegetation have been observed 

 in both the Upper and the Lower Oolite. 



The Purbeck " Dirt Beds," soils of vegetation near top of the 

 Upper Oolite, have been mentioned in most of the text-books on 



* Part I. appeared in these Proceedings, Vol. LV., pp. 21-203 ; Part II., in 

 Vol. LVI., pp. 53-151- 



PROC AMER. PHIL. SOC. , VOL. LVII, A, JANUARY 30, I918. 



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