ORIGINAL ARTICLES. 



Intra-Jurassic Movements and the Underground Structure 

 of the Southern Midlands. 



By Professor Arthub Hubert Cox, M.Sc, Ph.D., F.G.S., and 

 Arthur E. Trueman, D.Sc, F.G.S., University College of South 

 Wales and Monmouthshire, Cardiff. 



I. Introduction. 



EECENT investigations into the relationship between geological 

 structure and magnetic disturbance have called attention to 

 the existence of a line of anticlinal folding that affects the Triassic 

 and Lower Jurassic rocks in the neighbourhood of Melton Mowbray, 

 Leicestershire.^ It has further been shown to be highly probable 

 that this post-Triassic anticline follows and is founded upon the 

 line of an older and more pronounced anticlinal uplift of pre-Permian 

 date.^ The presence of the post-Triassic anticline is indicated on 

 the geological map by the sudden swing round of the outcrops of 

 Triassic and Liassic rocks from the normal north to south (or 

 N.N.E. to S.S.W.) direction into a north-west to south-east direction, 

 and then back again to the normal (N.N.E. to S.S.W. ). The sudden 

 change of strike is noticeable in the outcrops of all the formations 

 from the Keuper Marl to the Inferior Oolite inclusive, but it becomes 

 least apparent and is gradually lost in the succeeding divisions of 

 the Middle Jurassic. This suggests that the movements that gave 

 rise to the anticlinal structure had died down during or prior to the 

 deposition of the Bathonian rocks. 



A similar swing is seen in the Vale of Moreton, and again in the 

 north Cotteswolds, and these were shown by Mr. S. S. Buckman 

 to be due to anticlinal and synclinal folding ;''' the same writer has 

 repeatedly shown by his detailed zonal studies that the Inferior 

 Oolite and other divisions of the Jurassic rocks frequently shoM^ 

 evidence of anticlinal flexuring and penecontemporaneous erosion.* 

 For instance, he showed that the sequence of the Upper Liassic 

 zones is complete, or nearly so, at Bredon Hill, which is situated on 

 a synclinal axis, while elsewhere non-sequences frequently occur, 

 especially along lines of anticlinal folding. He has further suggested 

 that movement has occurred along many of these lines at intervals 

 during Mesozoic and even Tertiary times.' 



1 Cox, " A Report q]i Magnetic Disturbances in Northamptonshire and 

 Leicestershire and tlieir Relations to the Geological Structure ' ' : Phil. Trans., 

 ser. A, vol. 219, 1919, Appendix, pp. 73-135. 



2 Loo. cit., p. 122. 



^ Buckman, "The Toarcian of Bredon Hill" : Quart. Journ. Geol. Soc, 

 vol. lix, 1903, p. 449. 



^ A list of Mr. Buckman's chief papers on these subjects is given in Quart. 

 Journ. Geol. Soc., vol. Ixvi, 1910, p. .53. 



^ Op. supra cit., 1903, p. 449. 



