H. A. Baker — Chamian Movement in East Kent. 399 



and Transition Measures (but particularly the latter) to thin in an 

 easterly direction has been observed. 1 



The present contours of the Palaeozoic floor in East Kent must 

 differ considerably from those presented by it during the time of the 

 encroachment upon it of the Lias and Oolites. This is in consequence 

 of the severe post-Jurassic earth-movements which have affected the 

 South-East of England. The most important of these movements 

 occurred 1 in post-Cretaceous times, and that which had the greatest 

 effect upon the Palaeozoic floor was the one Avhich resulted in 

 the uplift of the Weald. Its chief effect upon the old floor in East 

 Kent was to decrease very considerably the south-westerly slope. 

 Considering, for example, the average downward slope of the 

 Palaeozoic floor from Ripple to Ellinge, it is now seen to be about 

 51£ feet to the mile, whereas in pre-Cretaceous times it must have 

 been more than 110 feet to the mile. Consequently, in considering 

 the disposition and variation in thickness of the members of the 

 Mesozoic cover in relation to the old floor upon which they 

 successively encroached, it is necessary to have some idea of the form 

 of the latter as it was during the time of the deposition of these 

 Mesozoics. Map 1 (Plate XXVI) is inserted here in which an attempt 

 is made to eliminate the effects of post-Lower Cretaceous movements 

 from the Palaeozoic floor by considering the base of the Gault as 

 a datum-plane and drawing a system of lines through points on the 

 floor at equal depths below it. 2 This method naturally suffers from 

 the imperfections of artificiality, and, of course, gives only an 

 approximation to the true pre-Upper Cretaceous contours of the 

 floor, since no allowance has been made (nor, in the circumstances, 

 can be made) for the variation in depth of the Gault sea ; but, 

 speaking generally, the chief error involved is that the south- 

 westerly slope of the floor appears somewhat less than it must 

 actually have been. The point, however, is one of no importance for 

 our present purpose. 



The map shows very clearly indeed that in pre-Cretaceous times 

 the Palaeozoic floor of East Kent was part of the western flank of an 

 elevated ridge lying to the north-east of the Ebbsfleet-Deal area, and 

 possessing a distinctly N.W.-S.E. trend. Westward, however, the 

 influence of the ridge is seen to die out. The contours present one 

 or two features of special interest. The lines do not everywhere 

 accord with those of a peneplain, but suggest, rather, immature 

 denudation, or, at any rate, interruption and readjustment of the 

 conditions under which denudation was progressing, by a movement 

 of uplift in the north, probably accompanied by faulting, along a new 

 and discordant line, viz. roughly east and west. An interesting 

 subsidiary ridge or spur (or disturbance) crossed the area, entering 

 Kent in the neighbourhood of Deal and dying out near Popersole. 



Turning now to the consideration of the features presented by the 

 Jurassic strata in proximity with this N.W.-S.E. ridge, we find 

 abundant evidence not only of the existence of the ridge in Jurassic 



1 Newell Arber, Trans. Inst. Min. Eng., vol. xlvii, pt. v, pp. 677-724, 

 1914. 



2 See Table I, p. 402, at end of paper. 



