part 4] juEASsic ciiEONOLoar. 445 



shows the most attenuated facies of the Junction-Bed yet observed 

 on the coast. 



Section VII — The Junction-Bed and Contiguous Deposits, measured 

 in situ close to the Eastern End of Thorncombe Beacon. 



Hemeras. 



Dumortieria. 



Bifrons. 



S err at a. 



Strata and Fauna. Feet inches. 



A + B. Blue sandy 'Upper Lias' clay. Coarsely- 

 ribbed Dumortieria sp. in friable condition. 

 Thin irony scale (impersistent). 

 L. Eartli}^ congloneratic limestone, with a mark- 

 edly-srnootii top. Hildoceras hifrons. 

 Strong parting. 

 P. Light-brown, linel}^ oolitic 'marlstone,' yielding 

 Rhi/nchonella acuta. Top planed off verj^ 

 smooth, 

 liesting upon 

 S. Blue sandy clay. 



6-6 



6-7 



Sections I to YII will have served to illustrate some of the 

 extraordinary complexities of the Junction -Bed ; a larger num.ber 

 of sections would show still further variations. 



A few yards east of Section YII the outcrop of the Junction- 

 Bed leaves the cliff-face, and turns inland ; when the Junction-Bed 

 reappears at Watton Cliff, east of Eypesmouth, the whole facies 

 is remarkably changed. 



(4) The Watton-Cliff Section. 



From the last appearance of the Junction-Bed at the eastern 

 end of Thorncombe Beacon to its reappearance at the western 

 end of Watton Cliff, east of Eypesmouth, there is a gap of some 

 three-quarters of a mile. 



At Watton Cliff the Junction-Bed is exposed in a particularly 

 inaccessible position. It forms a kind of projecting cornice, 

 high up in the precipitous face of the cliff, on the upcast side of 

 the great fault that throws ' Fuller's Earth ' and ' Forest Marble ' 

 against the ' Middle ' and ' Upper Lias.' According to the Geolo- 

 gical Survey,^ the downthrow is ' at least 425 feet.' 



The only published reference to the existence of the Junction- 

 Bed at Watton Cliff that I have been able to find is the following 

 short and inconclusive note by the Greological Survey (loc. cit.) : 



' East of Eype the cliff again exhibits a portion of the Middle Lias. At the 

 base there are blue clays with Amtnonites margaritatus, and these are suc- 

 ceeded by the Starfish Bed, the Laminated Beds, and Yellow Sands. These 

 are capped by grey shaly beds, that include a hard band that may be the 

 Junction-Bed of Middle and Upper Lias, with perhaps some portions of 

 the overlying Upper Lias. The higher strata were, however, difficult of 

 access.' 



It seems somewhat remarkable that this unique section should 

 have escaped general notice for so many years. It is quite easy to 

 observe from the talus that the Junction-Bed is much thicker here 

 than in the Western Cliffs. 



^ ' The Jurassic Rocks of Britain : the Lias of England & Wales ' Mem. 

 Geol. Surv. vol. iii (1893) p. 200. 



2h2 



