86 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 19, 



only is the condition of the upper 15 or 20 feet of the chalk in the 

 section at Litcham, upon which the Lower Drift rests, such as this, hut 

 the state of the flint bands there indicates that great disturbance has 

 taken place by a force acting downwards from the surface, and be- 

 coming less powerful the deeper the section descends. This is best 

 displayed in a part of the quarry where the Lower Drift has, by the 

 postglacial denudation which gave rise to the gravel (d), been re- 

 moved ; but although such is the case, it is sufficiently clear from 

 similar although less striking features in the adjoining quarry, 

 where the Lower Drift occurs, that this force was exerted before 

 that formation was spread over the chalk. By the section (fig. 2) it 

 will be seen that, of the bands of flint, ovlj the lowest is perfect in its 

 continuity, the others having been ruptui^ed by some force not exerted 

 from below, and whose intensity diminished downwards; and that this 

 lowest band, although not ruptured, indicates, by its upward curva- 

 ture under the spot where the bands which overlie it are ruptured 

 and destroyed, that it has sustained in a less degree that dragging 

 towards the surface which has been powerful enough to shatter al- 

 together the bands above it. In the body of the chalk also are galls 

 or cavities filled with dark-brown clay. These galls are not sections 

 cutting obliquely across pipes or potholes, which are so common 

 where the chalk or other soft limestone strata have been subjected 

 to the Postglacial denudation, and into which the bed immediately 

 over them commonly descends, but are cavities filled with some ma- 

 terial quite foreign to the present superincumbent strata. Pipes, or 

 potholes, of the well-known kind do, in fact, occur in the adjoining 

 quarry, and are of great dimensions, passing completely through the 

 thin bed of Lower Drift exposed there, and thence through some 20 

 feet of chalk. These, as is usual in similar cases, are filled with the 

 gravel {d) ; but to them the galls of clay shown in the section have 

 no relation. 



Fig. 2. — Section at Litcham Lime-Jciln. 



a. Chalk with flint bands, becoming gradually more impure upwards, and the 

 flints becoming detached and scattered in the upper part, about 20 feet. d. 

 Coarse red Postglacial gravel. + Grails of dark -brown clay. 



N.B. The lines of shading indicating the chalk in the upper part of the section 

 are not to be regarded as lines of stratification. 



Closely resembling the chalk in this section, are several of the 



