DRIFT-STAGES OF Ullu DAKKXT VALLEY. 155 



jx'bbles derived evidently from the lied Cluy-with-flints, and 

 from the Lower-Eocene strata on the adjacent hills. This red 

 argiUaceous rubble is certainly not rainwash, nor can it be the 

 result of surface disintegration. At present, however, I am only 

 concerned with the fact of its being a drift or covering which 

 precludes us from assigning the Chalk-rubble which underlies it 

 to sucli existing causes as rainwash or weathering. 



Not being worked for any purpose, it is rarely that sections of 

 these " rubbles " arc to be seen. Of the few that have come under 

 my notice in this valley, the following (fig. 12) is an example. It 

 occurred in digging a pit about 10 to 12 feet deep for a reservoir in 

 a field on the slope above Sepham Parm, near Otford. 



.Fig. 12. — Section on Sepham Farm, on the lotver slope of the 



Chalk hills. 



^reSK^^^wii 



^^O^^^i 





a'. Eed argillaceous rubble with dispersed Chalk flints and Tertiary pebbles, 

 2'. Chalk-rubble of broken chalk and sharp angular flint-fraginents in a 



chalk-paste, passing into — 

 2, Solid Chalk with layers of flint. 



The two beds {a' and 2') are perfectly distinct, and never pass- 

 one into the other ; 2', on the other hand, does not form a sharp line 

 with the underlying Chalk, but graduates into it. The height of 

 the ground is about 280 feet above O.D., and 90 feet above the- 

 level of the Darent. The Red rubble is easily recognized in the 

 ploughed fields by its colour. But while this is local and only 

 covers certain areas in the valleys intersecting the Red Clay-with- 

 flints plateau, the white " Chalk- and tiint-rubble " is more 

 general *, passing under the Red rubble, as well as over the wider 

 intervening spaces. In those valleys to which it is limited it rises 

 to a considerable height on the slopes and descends to the bottom of 

 the valley. 



From the position and character of the White rubble, in which 

 the Chalk forms a pulverized paste with dispersed subangular frag- 

 ments of chalk, sharply angular flints — broken but otherwise un- 

 altered — and occasionally some Tertiary flint-pebbles, and a few 

 fragments of ironstone and chert from the Lower Greensand, it is, 

 I think, not improbably Glacial waste connected with that stage of 

 valley-erosion whicli preceded the drift /', and of which the festoon- 

 ing of the Chalk is a subordinate feature. 



Just east of Otford, at the angle formed at the junction of the 

 Holmesdale Yalley with the pass of the Darent Valley through the 



* 'Chalk- and flint-rubble' was said to underlie the MamiuothgraTel at 

 Shoreham, 



