Vol. 65.] GEOLOGY OF THE NEIGHBOURHOOD OF SEAFOED. 457 



of the lower part of the Cuckmere Valley : this is well brought out 

 in the relief-diagram (fig. 8). The east side is deeply intersected 

 by dry valleys ; while the west side is but a faintly eroded dip-slope, 

 except near liishopstone, wbere we pass beyond the limits of the 

 depression. This feature may, therefore, also be attributed to the 

 influence of the Seaford Head fold. The depression formed by this 

 fold would retain its Tertiary cover long after it had been denuded 

 from the adjoining areas. Within the limits of this basin exten- 

 sive spreads of Eocene strata are still preserved : the Newhaven 

 Tertiary beds, and those at Seaford and Chyngton, are remnants 

 owing their preservation to this hollow. That at Chyngton is 

 particularly instructive, because it lies partly in the Cuckmere 

 Valley itself : a position which it would scarcely have occupied, if 

 this locality had not been situated at the bottom of the trough. 

 There are also other remnants of Tertiary beds in this area which 

 are not marked on the maps of the Geological Survey. Some of 

 these occupy deep pipes in the Chalk, one of which is situated close 

 to the northern boundary of the Actinocamax-quadratus Chalk, 

 near the 300-foot contour, about 2 miles due north of Seaford, 

 where it has been excavated to a depth of 20 feet for sand for the 

 new golf-links. That this pipe is in A.-q. Chalk is proved by direct 

 fossil evidence, and curiously I obtained here a perfect specimen 

 of Cardiaster pillula from the Tertiary sand itself. I have found 

 no evidence of any transgression in the Tertiary beds beyond the 

 limits of the Actinocamax-quadratus Zone. 1 It seems to me clearly 

 established that the persistence of the Eocene cover over the 

 area of the synclinal depression accounts for the absence of deep 

 dry valleys from the west side of the Cuckmere Fault, and their 

 recurrence beyond the limits of the hollow. 



A further result following from the geological structure of this 

 area is the break in the continuity of the cliff between Seaford 

 Head and Newhaven. This is clearly due to the fact that the 

 coast-line here intersects the trough of the basin. Seaford Head is 

 the last remnant of a limb of the uniclinal fold, the trend of which 

 is lost westwards in the Channel. The Newhaven cliffs are on the 

 northern margin of the basin, and the apparent horizontality of the 

 beds there is due to the fact that the cliff approximately follows 

 the direction of the strike. Towards Brighton the cliff trends still 

 more northwards, and thus recedes farther from the trough of the 

 fold, which may explain the absence of Tertiary beds for some 

 distance west of the Newhaven outliers. 



The view here expressed with regard to the absence of deep 

 valleys around Seaford is based on the theory that such valleys are 

 due mainly to erosion. The origin of such valleys in Chalk districts 

 has recently been much discussed, although data for studying their 

 relationship to the local stratigraphy have not generally been 

 available. 



1 The numerous greywethers about Alfriston have probably been let down 

 into their present position by the removal of tbe Chalk. 



