300 V. 0. Illing—The Search for Oil. 



main thrust of the American mountain-building movements. In 

 spite of this they have been folded, tilted, and fractured to an 

 extent which can be readily gauged by the inspection of any of the 

 Coal-Measure maps. In addition, the subsequent denudation has 

 been so extensive that the lower rocks are exposed in the anticlinal 

 areas and the Coal-Measures are largely confined to the structural 

 basins. It is largely in the subsidiary upwarps of these synclinal 

 areas that the borings for oil are situated. The tilting and faulting 

 of the Coal-Measures, small as it may be when compared with the 

 structures in the main mountain zones, is much more intense than 

 in any of the American Palaeozoic oilfields. In view of this difference 

 in tectonics, and still further the extreme erosion to which Palaeozoic 

 rocks have been subjected in these Islands, the chances of finding 

 commercial supplies of petroleum are extremely small. To be sure 

 there is hardly any doubt that small quantities of oil and gas lie 

 locked up within the impervious strata of Britain ; such patches 

 have been found before and no doubt will be found again, but they 

 will give little satisfaction to those who believe the country is yet 

 to be covered with flourishing oilfields. 



The comparison of Britain and America is an unfortunate one. The 

 broad area of American Palaeozoic rocks, between the Pennsylvanian 

 Mountains on the east and the Rocky Mountains on the west, lies 

 on the great Pre-Cambrian shield of North America, and, though 

 bordered by mountains, it has never been affected by orogenic 

 movements. On the other hand, the structure of Britain may be 

 said to be based on mountain-building movements. Pre-Cambrian, 

 Caledonian, and Armorican movements have successively striven to 

 impose their structures on the ground-plan of these Islands. The 

 folded, crumpled, and rifted nature of our Palaeozoic structures 

 testify to the success of their efforts. Even the Alpine folds invaded 

 our southern shores. To search for petroleum in such structures, 

 deeply dissected by extensive periods of denudation, cannot be 

 justified by comparison with any analogous examples of successful 

 oilfields in the equivalent formations of the rest of the world. 



Conclusions. 



It appears to the writer, after a review of the oil indications and 

 comparison of the geological conditions both in Britain and America, 

 that the following conclusions may be drawn : — 



1. The asphalt, oil, and gas occurrences in Britain are no more 

 than would be expected in any thick mass of deltaic and marine 

 sediments. Their haphazard distribution indicates their local origin 

 and does not imply any association with commercial oil-pools. 



2. There is a significant absence of definite oil and asphalt 

 indications in localities where the geological conditions would lead 

 one to expect such occurrences, on the assumption that the Lower 

 Carboniferous rocks contain large supplies of oil. 



3. No parallel can be drawn between the structures of the 

 British Carboniferous rocks and the equivalent formations of the 

 American oilfields. The structures in the British formations are 

 much more highly warped and fractured than are those in America. 



