550 J. W. Ehces — London Clay at Southampton. 



of the Test has exposed in its bed septarian blocks containing 

 pebbles and oysters. The number of species obtained as yet is not 

 sufficient to identify this bed as London Clay, but from a considera- 

 tion of its position with regard to the beds in the well on the com- 

 mon, and the outcrop of the Lower Bagshot at Bassett, there can be 

 little doubt that the bed is of London Clay age. 



The outcrop of these lower beds in the area occupied chiefly by 

 strata higher in the series is perhaps to be explained as follows : — 

 About four miles to the south of the northern outcrop of the Chalk 

 of the Hampshire basin, there runs an anticlinal axis, the existence 

 of which, in part of its course at least, has long been known to 

 geologists. In the eastern part of the basin it appears in the shape 

 of the Portsdown Chalk ridge, but west of Fareham the Chalk dis- 

 appears beneath the Tertiaries. The axis can be traced on the pre- 

 sent map as far west as Botley, but no further indication of it is to 

 be seen till we pass west of the Test valley, the Chalk re-appearing 

 at Dean Hill", which forms a promontory running out in an easterly 

 direction into the Tertiary beds. If a curved line be drawn connect- 

 ing Portsdown and Dean Hill, a few miles south of the northern 

 outcrop of the Chalk, it will be found to pass north of Southampton, 

 and near the localities of the above-described outcrops of the London 

 Clay. Consequently an upthrow of the beds above the Chalk has 

 been caused, and where denudation has produced sufficiently deep 

 valleys, some of the lower beds of the Eocene series are exposed, 

 though the Chalk has not been reached. 



Another possible explanation is the existence of a fault, but I am 

 not aware that any evidence has yet been obtained which would tend 

 to support such a view. 



On the subject of this anticlinal Mr. C. Evans (On the Geology of 

 Portsmouth and Ryde, Proc. Geol. Assoc, vol. ii. No. 3, p. 63) re- 

 marks that the various chalk-pits opened on the south escarpment of 

 Portsdown show that the dip of the strata is in general to the north- 

 east, but to the west near Fareham they may be seen to dip S.S.W. 

 A plain of Chalk extends to some distance south of the escarpment. 

 " It is therefore probable that Portsdown is the northern side of an 

 anticlinal fold of the Chalk, the southern portion of which has suf- 

 fered much denudation." East of Portsdown the Chalk outcrop 

 occupies lower ground, and at one spot near Chichester, Woolwich 

 beds cover it; thence it j^asses seawards. At the western end of 

 the axis, the dip of the beds is well seen in the railway cuttings of 

 the Salisbury and Dorset line. Mr. E. Westlake, F.G.S. (Geology, 

 in Notes on the Town and Neighbourhood of Fordingbridge), states 

 that " from Downton the Chalk rises gradually to the north for about 

 2^ miles, till it reaches the line of uplift of Dean Hill and Clearbury 

 — then in the last cutting it dips sharply to the north, and passes 

 again beneath the Eocene." 



The existence of this anticlinal in the neighbourhood of South- 

 ampton was indicated in the section accompanying a paper on the 

 Southampton well, by Messrs. E. Westlake and T. W. Shore, read at 

 the meeting of the British Association, 1882. 



