364 R. M. Brydone — Zone of Offaster iJilula 



B. Suhzone of abundant 0. pilula. 



The lower boundary of this subzone comes into the cliff just 

 opposite Roedean School, and the upper boundary also undoubtedly 

 comes in towards the top of Beacon Hill just west of Bottingdean. 

 Rottingdean Gap cuts clean through this subzone and into the 

 one below, but it reappears in East Hill, where its full thick- 

 ness is present and there is also room for a substantial amount of 

 quadratus-ohsilk. Saltdean Bottom cuts again clean through this 

 subzone, but it is clearly present in Portobello cliff in its full 

 thickness, sinking gradually eastwards as the Saltdean anticline 

 passes into the Telscombe syncline. In the centre of the Telscombe 

 syncline the whole subzone passes out of the cliff on to the foreshore, 

 the upper boundary descending several feet below high-water mark ; 

 but it soon rises into the cliff again, and then monopolizes the base of 

 the cliff most of the way to the west end of Friars Bay and does not 

 rise wholly out of reach until the west horn of Friars Bay is turned. 

 Over the Friars Bay anticline it is in the upper part of the cliff, but 

 never quite reaches the top of the cliff ; even Chene Gap fails 

 apparently to cut quite down to it. At Old Nore Point it comes 

 down to beach level and the greater part of it passes rather quickly 

 out of the cliff on to the foreshore ; but the rapid diminution in the 

 dip as the Friars Bay anticline passes into the Castle Hill syncline 

 keeps the upper boundary just above beach level. From this point 

 to Newhaven the dip (westwards) is very slight, but gradually brings 

 the upper belt and then the middle belt and finally perhaps the top 

 of the lower belt of the subzone into the cliff. 



The subzone has sunk again below the surface when the chalk 

 reappears above beach level at Buckle Inn, but between that point and 

 Seaford it used to be recognizable on the foreshore at low water. At 

 Seaford Head it reappears for the last time, emerging from behind the 

 sea-wall with its upper boundary about 12 feet below the esplanade 

 level and passing rapidly up through the cliff and out at the top. 



The subzone is so uniform in its physical characters that the 

 following section will apply to every occurrence of it. 



Subzone of abundant Offaster pilula in the SUSSEX Cliffs. 

 Chalk of zone of A. quadratus. 



Marl seam. ft. in. ft. in. 



/ /Chalk with very large 0. pilula . . 1 to 1 6 



/ ^ I Flint seam. 



o ^. Chalk with large 0. pilula . . .16 2 

 ^ '^ Marl seam. 



-^•-S -(Chalk 2 6 2 9 



S V Marl seam. 



So Chalk 6 6 7 6 



*-* I Marl seam. 



^Chalk .10 16 



05 Marl seam. 



.§ ^ /Chalk with very few marl seams (except 

 g.S V at Seaford Head, where there are five) 20 22 

 "o ^ Flint seam, often tabular. 



5H ■« ^* fChalk with varying seams of marl and 



""'J flint 10 6 11 



Marl seam. 

 .Chalk 13 16 



r oU 



Marl seam. 44 3 to 49 9 



Chalk of subzone of E. scutatus, var. depressus. 



