﻿442 MR. E. H. RASTALL ON THE [Aug. I905, 



changed, and some 150 feet of the cliff-section seems to be un- 

 represented. Over the rest of the Jurassic area, to the north and 

 west, this second type of junction between the Lias and Oolites 

 alone occurs ; and it is the object of the present paper to attempt to 

 offer an explanation of this state of things. 



Before discussing this question it will be necessary to describe, 

 somewhat in detail, the section at Blea Wyke, and some of the more 

 northerly and westerly sections where the junction is visible. 

 Fortunately such sections are numerous, as these beds are always 

 well displayed in the old Alum-Shale quarries which are so 

 abundant in this neighbourhood. The Alum-Shale is, practically, 

 the Ammonites-communis and bifrons- zone, and no higher zone is 

 developed to any appreciable extent in these quarries. Directly 

 upon it rest what appear to be the basement-beds of the Oolites, 

 commonly known as the Dogger ; and to this our attention will 

 be directed, in the endeavour to discover elsewhere representatives 

 of the passage-beds of Blea Wyke. 



II. The Typical Section : Blea Wyke Point. 



Immediately below Bavenscar Railway-station the cliff is 600 feet 

 high, and shows a very fine section of the estuarine development of 

 the Middle Jurassic, from the Moor Grit downwards : this series is 

 here unusually thick, measuring about 630 feet, instead of some 

 400 feet as usual. 



The Blea Wyke Beds and the overlying Dogger form a small 

 headland, Blea Wyke Point, while the softer StriatulusSh&les have 

 been excavated into a small wyke or bay, to the west of the point. 

 This bay and point are very easily reached by a path down the cliff 

 immediately opposite the station, and this is much the best locality 

 to study these beds. 



At the point the « Dogger ' and Yellow Beds form the lowest part 

 of the cliff, while the underlying beds form flat scaurs covered at 

 high tide. 



The detailed section here is as follows : — 



Thickness in feet. 



s f Ferruginous sandstone, with scattered pebbles 10 



o I ' Nerin(ea-~Bed ' : band of shells preserved in iron-oxide li 



( Greenish-yellow sandstone, with bands of pebbles 25 



Brown shaly bed 1 



Brown sandstone, full of Terebratula trilineata .... 2 



Yellow sandstone, with a band of belemnites and pebbles at its 



W I base 1 



£ \ Yellow ferruginous sandstone 2 



Very soft yellow sandstone 1 



Soft yellow ferruginous sandstone, with irony knobs and con- 

 cretions ; in the lower part are very numerous specimens of 



Avicula, with Serpula, Fecten, EhynchuneUa, Mytilus 20 



^ Soft rotten band 1 



