200 A. H. Cox and A. E. Trueman — 



bending of outcrops without the aid of any anticlinal flexuring. On 

 the other hand, the existence of the valleys may be significant when 

 account is taken of the known preference of river valleys for anti- 

 clinal areas, as instanced by the anticlines already proved through 

 Melton Mowbray and the Vale of Moreton. 



Although the outcrops of the various members of the Lower 

 Jurassic, particularly the Lower and Middle Lias, suffer marked 

 deviations in the valleys mentioned above, it is noticeable that the 

 outcrops of the Middle and Upper Jurassic rocks are not affected 

 in any way. This at once suggests that the flexuring took place 

 during Jurassic time, and that the movements had died down 

 prior to the deposition of the Cornbrash and Oxford Clay. 



If such intra-Jurassic folding has occurred it would give rise 

 to non-sequences along the anticlinal axes, while in the com- 

 plementary synclines the succession should be more nearly complete. 

 This has proved to be the case wherever the strata have been 

 sufficiently studied, as in the Vale of Moreton anticline and the 

 Bredon syncline, investigated by Buckman. 



in. Further Evidences of Intra-Jurassic Movement. 



In attempting to use zonal methods to demonstrate the existence 

 of Jurassic folding in the area between the Vale of Moreton and 

 Melton Mowbray, we are imfortunately met by a great lack of 

 detailed information which can be regarded as trustworthy in the 

 light of recent refinements of zonal work. Further, it has frequently 

 happened that the thickness of a subdivision or zone as determined 

 at one locality has been quoted as the thickness throughout a ivliole 

 county. In point of fact, thicknesses may vary greatly within the 

 county limits. For these reasons we have been unable to use many 

 of the figures that at first sight would appear to be available. Owing 

 to this lack of reliable information only certain well-marked zones 

 can at present be used for our purpose. 



It is obvious that non-sequences and local variations in thickness 

 will show best in thin zones. Further, the most \iseful deposits 

 will be those which were laid down after periods of con- 

 siderable movement ; thus Mr. Buckman has found that some of 

 the most notable non-sequences correspond with the Bajocian 

 uplift and denudation.' During the deposition of the Lias, the 

 maximum movement occurred between the times of accumulation of 

 the Middle and Upper Lias, that is after the hemera of spinati, when 

 slight uplift took place, and gentle folding resulted in the formation 

 of several shallow basins in which first a thin deposit of the 

 Transition Bed {acutuni zone) and then the lower zones of the Upper 

 Lias were laid down.^ These beds would naturally be absent or very 



' Buokman, " The Cleeve Hill Plateau " : Quart. Journ. Geol. Soc, vol. Iviii, 

 1897, pi. xlvi ; and also "The Bajocian of the North Cotteswolds " : ibid., 

 vol. Ivii, 1901, p. 14fi. 



^ Trueinan, " The Lias of South Lincolnshire " : Geoi.. Mag., 1918, p. 108. 



