Ixxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 101 1, 



movements the chief are the earlier and later stages of those move- 

 ments with Caledonian trend and that of post-Carboniferous times. 

 Of cpeirogenic may be noted the middle portion of the Caledonian 

 movement, that in the late Carboniferous, that which closed the 

 Jurassic Period, and that great uplift which came at the end of 

 the Cretaceous. 



But there were many gentle movements which we are only now 

 beginning to appreciate, and doubtless many others of which we 

 shall gain information later on by the application of the methods 

 that have proved so successful in the hands of Mr. S. S. Buckman, 

 Mr. L. Richardson, and others, in the study of the Jurassic rocks. In 

 this case the minute zoning of the Bajocian rocks has shown clearly 

 that the local thinning of the strata so frequent along the outcrop 

 of the Inferior Oolite is correlated with the absence of particular 

 faunas, and presumably of the strata which should contain them. 

 This may be due to one of two main causes — (a) the absence of 

 the strata owing to non-deposition or subsequent erosion, or (/3) the 

 migration and substitution of faunas. Exhaustive examination of 

 the fossils indicates that the former explanation is more likely to 

 be the satisfactory one ; and that this is the case seems to me to be 

 proved by the fact that at the junction-line, to which attention is 

 called by minute zone-working, signs of erosion and of pause in 

 deposition are usually visible in the form of irregular surfaces, 

 borings by worms and mollusca, and by deposits of oysters or of 

 rolled fragments and broken organisms. Further, the correlation 

 of series of localities indicates progressive absence of increasing 

 thicknesses of rock in definite directions. The directions thus indi- 

 cated correspond with the position of minor folds in the subjacent 

 or superjacent rocks. So there is every probability that these 

 areas of erosion have been determined by slight but long-continued 

 local uplift of anticlinal nature, affecting well-marked areas and 

 culminating along definite lines. 



Results apparently similar are coming out from the zoning work 

 in Lower Carboniferous rocks, and it is interesting to compare 

 these with the latest interpretation of the ' Symon Fault,' to which 

 attention has already been directed. That such results do not yet 

 appear to have been reached in the zoning of the Chalk may be 

 partly due to the thickness of the zones into which that Formation 

 is at present divided, or, which is more likely, to the Chalk having 

 been formed under water so much deeper than most other British 

 organic formations, that the elevatory movement was not sufficient 

 to bring the area within the scope of denudation. On the other 



