146 MB. 8. S. BTJCKMAN ON THE BAJOCIAN [Feb. I9OI, 



Then the boring at Mickleton went through nearly 1000 feet 

 of Lias ; bur, I have not the details of it. 



The difFerenee between the thickness of the Lins nt Bnrford and 

 Mickleton is probably due to denudations of anticlinal elevations 

 ■which occurred during Liassic times. It' that surmise be correct, 

 then there were mnny successive elevations along about the same 

 axial lines, and mnny denudations; a deduction which is important. 

 The dccrea>-e in thickness of Liassic rocks from Mickleton to Burford 

 might be taken as a measure of estimated decrease farther on. But 

 when such decrease is due to denudation, it is unsafe to do so, 

 because directly the anticlinal fold is re iched the rocks would begin 

 to thicken again. That is where the difi'erence lies between Hull's 

 surmises and my results.^ 



(/) Bajocian Denudation and the Vale of Moreton. 



A revised copy of the map of the Bajocinn denudation, which 

 appealed in the paper on the Cleeve Hill Plateau, may be given 

 here (PI. VI). I have marked therein the additional obsprvafions, 

 made certain corrections, and put in the lines ot the anticlinal and 

 synclinal axes. The most important point is the alteration of the 

 eastern lines of outcrop, showing that they run nearly with the 

 eastern flank of the Cotteswolds, pointing to an anticline in the 

 Vale of Moreton. 



The coincidence of the axis of this anticline with the Vale of 

 Moreton is certainly suggestive. It may be readily seen that the 

 denudation would have had a considerable effect on the making of 

 the Vale of Moreton, from two causes : — 



(1) Owirg to the antirline, an imperviovis bed is brought rearer to tbe 

 surface along the line of the Vale of Moreton, thus laycuring the outbreak of 

 sprivigs. 



(2) Owirg to denudation, something like 200 feet of what must have been a 

 very protective liniestore capping has been runovcd. The present denuding 

 agencies get down to easily rcini-ved clay 200 feet sooner than they would have 

 done without the Jurassic denudation. 



The diagram given on p. 140 illustrates the aspect of affairs. 

 It shows how, the Great Oolite being removed, there remained no 

 protective covering of Inferior Oolite of any grent thickness. ISo 

 soon as that was cut through, the Lias would be easily excavated, 



(g) Bajocian Denudation and the V^ale of Bourton. 



The peculiar shape of the Vale of Bourton has always seemed to 

 be rather difficult of explanation. The Bajocian denudation seems 

 to give the necessary clue. The Vale owes its existence to a com- 

 bination of four circumstances ; but without the Bajocian denudation 



^ [All the details given by Hull in his paper on the 'Attenuation of the 

 Secoi.daiy EoclvS ' (Quart. Juuru. Geol Soc. vol. xvi, 18fi0, p. ()3) figrte wilh the 

 idea ( t peneconleniporaneous erosion, particularly of ihe successiye erosions | 

 detailed here in Appendix II, p. \b2.-— January '22nd, 1901.] 



