26 



CORNISH POST-TERTIARY GEOLOGY. 



Fig. 18. Towan Head. 

 Vertical Scale— 1 inch = 20 feet. 



"%^ 



Near Xew Quay Pier, a raised beach occurs on a rocky platform 

 about 20 yards in widtb, and from 5 to 

 6 feet above high-water mark. It con- 

 sists of tough, buff, sand rock, weather- 

 ing dark grey (frequently emitting 

 sparks when struck), containing large 

 slate and limestone boulders, quartz, 

 slate, and, occasionally, flint pebbles. 

 The boulders might have fallen from 

 cliffs overhanging the old beach during -_-::= ^"""^z^^"^- ^^^^^ - ~ 

 its formation. 



Consolidated sand beds (old blown sands) are visible in the 

 adjacent cliffs. Bones of oxen are said to have been found in the 

 consolidated sands of New Quay.^ 



De la Beche says that the consolidated sands of New Quay are 

 sometimes cemented by oxide of iron or calcareous matter, and 

 sometimes by both.^ In the Fistral Bay raised beach, Mr. S. E. 

 Pattison ^ found Modiola vulgaris, Cytherea cliione, Patella, Ostrea. 



(Fig. 19). Constantine Island is capped by brown sand, with 

 tests oi Patellce and broken Mytili to a depth of from 1 to 2 feet; 

 under which, toward the north part of the island, angular fragments 

 of slate and quartz, and occasionally gi-eenstone pebbles, are shown, 

 forming an impersistent bed 3 feet in maximum thickness, and at 

 base, from 5 to 8 feet above hiojh-water mark. 



Fig. 19. Constantine Island. 

 1 inch = 24 feet. 



^ii^^:p^^ 



1 From the small quantity of sand now drifted on the old consolidated sand dunes 

 of Xew Quay, De la Beche considered that the change of level had rendered the 

 locality less fit for .such accumulations than it was during the Eaised Beach forma- 

 tion.— De la Beche, Report on the Geology of Cornwall and Devon, p. 428. 



2 md. p. 431. 



* Trans. Hoy. Geol. Soc. Corn. vol. vii. p. 50. 



