BROOK AND ATHERFIELD 35 



Hard ledges of the Crioceras beds run into the sea. The 

 shore is usually covered deep with sand and small shingle ; 

 but there are times when the sea has washed the ledges 

 clear ; and it is then that the shore should be examined. 



The Walpen and Ladder Sands (42 ft.) ; the Upper 

 Exogyra Group (16 ft. ) ; the Cliff End Sand (28 ft.) ; and 

 the Foliated Clay and Sand (25 ft.), consisting of thin 

 alternations of greenish sand and dark-blue clay, follow. 

 Then the Sands of Walpen Undercliff (about 100 ft.) ; 

 over which lie the Ferruginous Bands of Blackgang Chine 

 (20 ft.). Over these hard beds the cascade of the Chine 

 falls. Cycads and other vegetable remains are found in 

 this neighbourhood. Throughout the Atherfield Green- 

 sand fragments of the fern Lonchopteris (Weichselia) 

 Mantelli are found. 220 ft. of dark clays and soft white 

 or yellow sandrock complete the Lower Greensand. In 

 the upper beds of the Greensand few organic remains 

 occur. A beautiful section of Sandrock with the junction 

 of the Carstone is to be seen inland at Rock above Bright- 

 stone. The Sandrock here is brightly coloured like the 

 sands of Alum Bay, though it belongs to a much older 

 formation, and shows current bedding very beautifully. 

 The junction of the Sandrock and Carstone is also well 

 seen in the sandpit at Marvel. 



We have now come to the end of the Lower Cretaceous, 

 in which are included the Wealden and the Lower Green- 

 sand. Judged by the character of the flora and fauna, 

 the two form one period, the main difference being the 

 effect of the recession of the shore line, due to the sub- 

 sidence which let in the sea over the Wealden delta, so 

 that we have marine strata in place of freshwater deposits. 

 But that the plants and animals of the Wealden age still 

 lived in the not distant continent is shown by the remains 

 borne down from the land. These strata are an example 

 of a phenomenon often met with in geology, that of a 

 great thickness of deposits all laid down in shallow water. 



