560 MR. A. STRAHAN OX OVERTHRUSTS OF [N~OV. 1895, 



The Osmington Mills anticline, to -which the dip of these earlier 

 rocks is due, runs along the shore west of that place, and is accom- 

 panied by a series of smaller rolls that can be seen at low-water in 

 the Corallian rocks farther east. It brings up the Osmington 

 Oolite and overlying Corallian subdivisions in an extremely sharp 

 A-shape close to the end of the jetty at the Mills, and gives rise also 

 to some remarkable trough-faulting at that place. The Kimmeridge 

 Clay in the northern limb of this anticline dips northwards at 40°, 

 but the Upper Greensand x lies nearly horizontally upon it, the 

 actual junction being fully exposed at Coggin's Barrow. The 

 denudation of the Upper Cretaceous rocks has proceeded just so far 

 as to render possible the mapping of the northern limb of this 

 anticline beneath them ; the Portland Stone, for example, repeatedly 

 disappears under the horizontal Upper Cretaceous rocks, always to 

 re-appear in the proper line of strike acquired through the intra- 

 Cretaceous tilt. 



Northwards this anticline is succeeded by the Upton syncline, 

 which is no less obviously of the earlier age. There we obtain con- 

 clusive proof that the movements were post-Wealden, which indeed 

 might have been inferred from the section at Whitenose. For 

 there they are seen to have been later than the Purbeck rocks, 

 which pass insensibly up into the "Wealden. 



The Upton syncline is followed by an anticline which has been 

 partly obliterated by the Eidgeway fault, but which can be traced 

 even through the disturbance by observing the difference in dip 

 between the Oolitic and Upper Cretaceous rocks, and thence in- 

 ferring the dip of the former before they received their second tilt. 



The Broadway anticline has hitherto been considered one and the 

 same with the Isle of "Wight and Isle of Purbeck fold 2 and has even 

 been assigned to a Quaternary age. 3 In placing it with the earlier 

 disturbances I am guided by its obvious connexion with the 

 Osmington Mills anticline. The Kimmeridge Clay outcrop runs 

 uninterruptedly along the northern sides of both, and both to the east 

 at Osmington and to the west at Abbotsbury is overlain by nearly 

 horizontal Upper Cretaceous strata. 



North of the Broadway anticline a syncline brings in the Middle 

 Purbeck strata west of Upway ; it can be traced as far as Abbotsbury. 

 On its northern side the strata turn up as though to another anti- 

 cline, which, however, is hidden by the Eidgeway fault. 



At Abbotsbury one of the largest of the earlier faults of the 

 district falls nearly in a line with the Ridgeway fault, of which it 

 has hitherto been considered part. It has, however, a downthrow 

 south of 600 or 700 feet, and passes under the Greensand without 

 displacing it. Were the Upper Cretaceous rocks affected to any- 

 thing like this extent, they would occur in force under the village. 



1 The G-ault is not generally distinguishable from the Upper Greensand in 

 this district. 



2 Hudleston, Proc. Geol. Assoc, vol. vii. (1881) p. 179, and vol. xi. (1889) 

 pp. Hi, liii. 



3 Prestwich, Quart. Journ. Geol. Soc. vol. xxxi. (1875) p. 43. 



