150 MR. A. J. JUKES-BROWNE ON [May I906, 



Woodford on the Avon, but here it seems to die out ; and I am 

 inclined to regard the small scattered tracts of Clay-with-Flints 

 around Woodford as being disposed round thepericlinal termination 

 of this anticline, a position which would account for the low levels 

 at which they occur (400 to 300 feet). 



On the east side of the Avon Valley another set of flexures come 

 in, which seem to be independent of those on the west. Here we 

 find a synclinal trough filled with Eocene, stretching eastward 

 from Alderbury. This is bounded on the south by a well-marked 

 anticline of bare chalk, and on the north by what is probably a 

 monoclinal rise, carrying the basal plane of the Eocene Series up 

 to a level which is much higher than the present general level of 

 Salisbury Plain. Here it is interesting and instructive to observe 

 several tracts of Clay-with-Flints, which behave exactly as if they 

 were outliers of Reading Beds, their southern boundaries being at 

 about 300 feet, while on the north they reach a height of about 

 440 feet. On a line with them, but at a slightly-higher level (486 

 feet), near Laverstock is a small outlier of Reading Beds ; and to 

 the north of them, on Thorny Down, is another outlier at 533 feet. 

 This last is about 300 feet higher than the outcrop of the Reading 

 Beds in Clarendon Park, only 3 miles to the south, and shows the 

 rapid rise of the basal plane or floor, upon which the Eocene rests. 



These small outliers, and the others previously noted as occurring 

 farther north in the area of Sheet 282, enable us to construct a 

 section showing the relative level at which the Eocene floor passed 

 over this part of Salisbury Plain (see Pi. YI, fig. 1). It also 

 indicates the manner in which the higher zones of the Chalk were 

 planed off prior to the formation of the Reading Beds, and thus 

 demonstrates the compound nature of the geanticline between the 

 London and Hampshire Basins. 



Passing now to the area included within Sheet 283 of the 

 Geological Survey-map, a casual view might convey the impression 

 that the tracts of Clay-with-Flints were distributed in an irregular 

 manner without respect to present levels, and without any special 

 relation to the flexuring of the district; but a closer examination 

 shows that there is a definite relation between them and the post- 

 Eocene flexures. 



Broadly speaking, the structure of the area is as follows. Its 

 northern part is traversed by an anticline, or rather by a series 

 of periclinal domes, which are made apparent by the outcrops of 

 Selbornian and Cenomanian strata near Grafton, Shalbourn, Wood- 

 hay, and Burghclere. From this irregular anticline the beds of the 

 Chalk slope southwards into a deep periclinal basin, the centre of 

 which must lie near the town of Andover, for near this place the 

 zone of Marsupites is found at levels of from 300 to 400 feet. 



If this basin be the complement of the northern anticline, and 

 was formed in post-Eocene times by a movement which carried the 

 basal plane of the Eocene with it, and, further, if the Clay-with- 

 Flints be mainly an Eocene residue : then we should expect to find 



