174 The Geology of the Berks ^ Hants Extension, 



upper band of stone in the green-sand is brought up first to the 

 bottom of the cutting, and a little farther on 10 feet higher, by 

 four or five jumps. To the west of the fault the band of stone is 

 broken and irregular in its dip, and the dip is much less than to 

 the east of the fault. A fissure in the fault was filled in with 

 a compact green chloritic mineral. The beds thrown up by the 

 fault have been denuded, and the whole planed down to an even 

 surface which is covered by a chalky drift, 3 or 4 feet thick. A 

 section of the fault is given in fig. 2. 



We have here the top of the Upper-green-sand dipping at 7° N. W., 

 this would bring up the Gault to the surface in less than a quarter 

 of a mile, taking the thickness of the Upper Greensand at 138 feet, 

 which is its estimated thickness at Devizes.' A quarter of a mile 

 brings us back to the east end of the cutting, at the road to Full- 

 way ; and as the dip of the beds for this distance is unbroken, and 

 at nearly the same angle, we have between the end of the cutting 

 and the fault a section of the Upper-green-sand from bottom to 

 top. Indeed, in the road to Fullway we probably see the top of 

 the Gault in some clayey beds there exposed. Although the clay 

 dug for brickmaking close by is certainly not Gault in situ, still its 

 origin and that of the more clayey portion of the drift towards 

 this end of the marshes, is probably due to the former presence of 

 the Gault at the surface. 



Either another fault, or a fold in the strata must exist between 

 Stert and Patney, to bring the beds in Stert cutting, there rising at 

 an angle of 7° towards the S.E., down to the Upper-green-sand near 

 Patney. It is more probably a fault, parallel in general direction 

 with the one exposed in the cutting, and which there appears to 

 run E.N.E. and W.N.W. 



The fault exposed in the cutting is perhaps one running from 

 Coulston along the junction of the Gault and the Portland sands, 

 to Stert and Etchilhampton. This would account for the bringing 

 up of the Portland sands to the level of the Gault in Urchfont 

 bottom, and for the elevation of the chalk composing Etchilhampton 

 hill. Such a fault would be in general direction parallel to those 

 ' Memoirs of Geological Siirvey, Sheet 34, p. 33. 



