MARINE GEOLOGICAL EXCURSION. Ixiii. 



Beyond this the sea again obtains access to the Cretaceous Beds in St. Oswald's 

 Bay, which terminates in Man-o'-War Cove. Here and at Durdle Door we 

 perceive the maximum effect of the Isle of Purbeck thrust -fault. Note the 

 outlying rocks of Portland stone in which the " door " occurs. Facing this the 

 Cretaceous rocks are inverted and compressed, whilst the Upper and most of the 

 Middle Purbecks are squeezed out altogether. The Great Fault runs about 

 750ft. inland from the Durdle Door ridge, passing through the Chalk at various 

 elevations, and coming out in the cliffs beneath the Warren about the third of a 

 mile to the westward of Bat's Head. Outside (north) of the thrust-fault, at the 

 point where it runs into the sea, the dip is 25 N. by W. ; whilst inside (i.e., on 

 the south) the dips are vertical for some distance, and opposite Durdle Door there 

 are inversions to the extent of 30 (110 N.N.W. and 120 N.N.E). The Chalk 

 inside the thrust zone is much shattered. The phenomena of Ballard Down are 

 here repeated, but less easy to perceive. 



White Nothe Point (summit 549ft. 1 ) is just about a mile west of the spot 

 where the thrust-fault emerges from the cliff and passes out to sea. The base of 

 White Nothe is formed by the Pecten asper-'beds of the Upper Greensand, which 

 dip 5 E., whilst the Chalk underneath the Coastguard Station dips 12 S.S.E. 

 These directions are nearly the reverse of those prevailing at Durdle Door, and 

 indicate a considerable amount of confusion in the stratigraphy. Notice the 

 " King Kock " and the " Old Castle " Eocks on the undercliff. 



Holworth House and Ringstead Bay. Beyond the point of White Nothe and 

 underneath Holworth House there is a landslip coming down to the beach, and 

 towards the head of Eingstead Bay, at some little distance from the shore, is the 

 " burning cliff " in Kimmeridge shale. Underneath Holworth House the Gault 

 may be seen to rest uncomformably on Purbecks, Portlands, and Kimmeridge 

 Clay. Throughout part of Eingstead Bay a low cliff of Kimmeridge Clay, and 

 at its base the " coral-bed," or topmost Corallian may be seen. The Trigonia- 

 beds and Osmington Oolite of the Corallian series occur in the cliff beneath 

 Upton House, dipping 4 E. ; they also form reefs out to sea. 



Osmington Mills. There is a complex fault and high anticlinal axis here, of an 

 age anterior to that of the Isle of Purbeck thrust- fault. This affects the Oolitic, 

 but not the Cretaceous beds in the vicinity. The stratigraphy of the interior at 

 Osmington Mills is extremely interesting and complex, but cannot be realized 

 from the coast. The great masses of stone hereabouts belong to the Bencliff 

 Grits of the Corallian series, and this feature may be noticed at several places in 

 the Weymouth peninsula. The Triffonia-loedLs on the shore west of Osmington 

 Mills have yielded many Coralliau fossils in a fine state of preservation. 



By the kindness of Mr. Hudleston luncheon was served on 

 board the "Empress," soon after which Lulworth Cove was 

 reached ; here the party disembarked and walked along the 

 beach to the tiny chapel on the hill, said by Mr. Hudleston and 



