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



times but also of the occurrence along it of repeated movements of 

 uplift, in fact " posthumous " movements. It is significant, too, that 

 the series of disturbances which can be traced is in remarkable 

 agreement with the movements cited by Professor P. F. Kendall ' as 

 having occurred along the line of his celebrated Charnian axis. In 

 the East Kent Jurassics illustrations may be noted of practically 

 every kind of evidence that superincumbent strata can yield con- 

 cerning the proximity of an axis of instability. The detailed account 

 of the Jurassic succession in the deep borings at Brabourne and 

 Dover, given in a Survey memoir, 2 is most interesting from this 

 point of view. At Brabourne, although Lower, Middle, and Upper 

 Lias are represented, the total thickness is but 140 feet, and. at 

 Dover, although all three divisions apparently still occur, the total 

 thickness of the formation has dwindled to less than 40 feet. At 

 several horizons planes of erosion occur, and rolled fragments, 

 nodules, and broken fossils are abundant. 



It is to be regretted that similar detailed accounts of the Lias 

 proved in some five or six other deep borings in East Kent are not as 

 yet available. At present we have little more than the recorded 

 thicknesses to work upon (and even these sometimes differ where 

 more than one record exists), arid so many different circumstances 

 combine in affecting the thickness of a deposit that, in general, it 

 would be scarcely safe to base any definite conclusions on it alone. 

 Nevertheless, in the present case, the tracing of isopachyte systems 

 in the Jurassic strata of East Kent (Map 2, Plate XXVII) results in 

 a series of lines revealing the closest sympathy with the pre-TTpper 

 Cretaceous contours of the Palaeozoic floor and bringing out clearly the 

 north-easterly encroachment of the Mesozoics upon the subsiding ridge. 



In the case of the Lias the evidence 3 is sufficient for the insertion 

 of three isopachytes, viz. (feather-edge of formation), 50 feet, and 

 100 feet. We see tbat with proximity to the easterly ridge the 

 isopachytes reveal a marked tendency to take on a N.W.-S.E. trend. 

 The influence of the Deal-Ropersole elevation upon the isopachyte 

 of the Lias is interesting. 



Passing to the Oolites we have more data to work upon and the 

 results are still more interesting. What detailed information we 

 possess concerning the Oolite succession in the borings, adds to the 

 evidence in favour of posthumous movement along the easterly ridge. 

 At Dover, as in Kendall's area, there is a marked non-sequence 

 between the Oolites and the Lias. The Inferior Oolite, which 

 undergoes a remarkable attenuation in Northamptonshire, and 

 becomes more and more sandy as the Charnian axis is approached, is 

 doubtfully represented at Dover by less than 30 feet of calcareous 

 sandy grit and clay, and at Brabourne by about 40 feet of muddy, 



1 Kendall, loc. cifc. 



2 Lamplugh & Kitchin, On the Mesozoic Rocks in some of the Coal 

 Explorations in Kent (Mem. Geol. Surv.), 1911. N.B. — It is not proposed 

 to deal fully with this evidence here. The reader is referred to the memoir 

 quoted, pp. 5-56, for abundant details, and to p. 94 for the significant 

 conclusions arrived at by the authors. 



3 See Table of Thicknesses (Table II), p. 403, at end of paper. 



