IN THE ANGLO-PARIS BASIN 49 



(e) Blackgang 



The section in the Carstone and Gault at Blackgang shows that the sequence has 

 changed fairly considerably in the mere 4! miles from Ventnor. The section given 

 in text-fig. 21 exposed below Cliff Cottage, Blackgang, shows that the sediments are 

 generally coarser in grade. It is exposed at the summit of a cliff of Sandrock Series 

 and in wet weather is dangerous. 



Bed 8 of the Carstone is probably of eodentatus Subzone age, but Hoplites (Iso- 

 hoplites) has not yet been found here. Unfortunately, the lower 8 feet (2-438 m.) of 

 the Gault is not clearly exposed but it certainly contains at least one fawn pyritic clay 

 band which has not yet yielded fossils. The only ammonite seen in Bed 3 was a 

 crushed Hamites (H.) sp. 4 inches (o-ioi m.) below the top which indicates the spathi 

 rather than the lyelli Subzone. Bed 12 has also yielded crushed Hoplites (H.) spp. 

 which indicate the spathi Subzone. No other ammonites have been found higher in 

 the section but /. concentricus still occurs 11 feet (3-352 m.) up in Bed 13. 



A section below Gore Cliff about 825 yards SE. of Cliff Cottage shows higher Gault 

 (text-fig. 22). Unfortunately the two sections probably do not overlap although 

 there is an obscured interval of 12 feet (3-657 m.) at the base of the Gore Cliff sequence. 

 /. concentricus is present in the top 1 foot 6 inches (0-457 m.) of ' Bed 1 ' showing it to 

 be still of Middle Albian age, but no other age indicative fossils are yet known from 

 this section. 



Certainly some of the lower part of the Gault here is of spathi Subzone age. How- 

 ever, the specimen of Hoplites aff. vectensis recorded by Spath (1925 ; 128, BMNH., 

 C 890) and said to be from Blackgang is in fact identical in preservation to specimens 

 from the top of the spathi Subzone at Osmington, Dorset, from whence it undoubtedly 

 came. 



(ii) BALLARD CLIFF TO OSMINGTON 



The early accounts of the Gault in this coastal area of Dorset were given by Strahan 

 (1898) and Jukes-Browne (1900). This work was revised by Wright {in Arkell 

 1947b ; 178-194), and there is no new information to add to his lithological account 

 for the sections have deteriorated considerably. However, his Subzonal classifica- 

 tion of the basal beds requires revision. Wright redescribes, as far as it is possible, 

 the sections at Punfield Cove, Swanage (SZ 03878110), Flower's Barrow, Worbarrow 

 Bay (SY 86388045), Lulworth Cove (East SY 82867988, West SY 82427988), 

 Durdle Cove (SY 80578028), White Nothe, and Black Head, Osmington, covering in 

 all a distance of 35 miles (text-fig. 18). 



Beds 1 and 2 at Flower's Barrow, Worbarrow Bay, are apparently of the same age 

 as the ferruginous clay with concretions at Black Head, Osmington, as Wright stated. 

 However, the fauna from these sediments at Black Head, first recorded by Cunning- 

 ton (1929) is not of ' benettianus ' Subzone age as Spath originally thought (Wright 

 in Arkell 1947b ; 181) for all the species of Hoplites (H.) which occur, such as H. (H.) 

 dorsetensis and H. (H.) vectensis, can be matched in the highest part of the spathi 

 Subzone in the Weald and elsewhere. Even Spath was to change his mind about the 

 Subzonal age of these two species, placing them in the intermedins Subzone (1942 ; 



D 



