610 Notices of Memoirs — W. Topley — On Petroleum. 



Trenton Limestone. In the North- West Territories there seem to 

 be great stores of oil in Devonian rocks. Gas and oil now found in 

 Cretaceous strata of the prairies and Athabasca may have been 

 derived from underlying Devonian rocks ; but in the Eocky 

 Mountains, at Crow's Nest Pass, oil is probably native to the 

 Cretaceous beds. 



In Mexico, the West Indies, and parts of South America, Tertiary 

 strata seem to be the chief source of oil. The age of the petroleum- 

 bearing unfossiliferous sands, etc., of the Argentine Republic (pro- 

 vince of Jujuy) is not certainly known ; they have been referred by 

 diiferent writers to various ages from Silurian to Tertiary ; they are 

 probably sub-Cretaceous. In Europe and Asia the petroleum- 

 bearing beds are of Secondary or Tertiary age, the Palgeozoic rocks 

 yielding only an insignificant supply. 



In North-west Germany we find petroleum in the Keuper Beds, 

 and more or less in other strata up to and including the Gault. As 

 we pass to the south and south-east from this district we find, as 

 a general rule, that oil occurs in newer strata. The various pro- 

 ductive horizons of different districts are as follows : — 



North-west Germany Keuper to Gault. 



Rhone Valley ) t 



Savoy ^ } J'^^^^'^''- 



cJ^ . \ Neocomian and Cretaceous. 



Spam j 



Elsass Oligocene. 



Bavaria Lower Tertiary (Flysch). 



Italy Eocene. 



NoSeast Hungary ( Neocomian to Miocene. 



Poland 



Eoumania \ Miocene 



Caucasus 



The important districts of Baku occur on plains over anticlinals of 

 Miocene beds. The petroleum-bearing sands are interstratified with 

 impervious clays, separating the strata into distinct productive 

 horizons. 



In Algeria oil occurs in Lower Tertiary beds. The Egyptian 

 petroleum comes from Miocene strata. 



Petroleum seems to be unknown in peninsular India ; but it 

 occurs in many places along the flanks of the Himalayan range, and 

 also in Lower Burma, generally in Lower Tertiary strata. In Upper 

 Burma and Japan the oil-bearing rocks are probably Newer Tertiary. 

 In all these areas the beds are greatly disturbed, and the same is the 

 case with the great Carpathian field ; but it frequently happens that 

 the most productive regions are along anticlinal lines. 



In New Zealand oil occurs in Cretaceous and Tertiary strata. 



Petroleum and gas almost universally occur associated with brine. 

 This may come wholly or partly from the decomposition of the 

 animal matter which has produced the hydrocarbons, together 

 with the remains of the sea- water originally present in the rocks. 

 But the frequent occurrence of rock-falt in the neighbourhood of 

 petroleum-bearing districts is worthy of note. 



