R. M. Brydone — Further Notes on the Trimmingham Chalk. 75 



unconformity between the grey chalk and 0. liinata chalk as 

 clearly as the stratigraphy. Ostrea lunata and the bun-shaped 

 EcMnoconiis are unknown in the grey chalk, which is full of Ostrea 

 incequicostata, 0. canaliculata, and Terebratida obesa, none of which 

 have ever yet been found in the 0. lunata chalk. There are very 

 similar grey beds on the foreshore underlying white chalk without 

 0. lunata, which passes up into 0. lunata chalk, but below they are 

 cut off by a fault, and until we know either what overlies the grey 

 chalk of the bluff or underlies the grey chalk of the foreshore 

 it is not safe to identify the two sets of grey beds, though it is very 

 tempting, the similarity being very striking, especially in the fossils. 



At the beginning of October, 1905, the clay behind the bluff 

 was broken through by the waves, and by the middle of the 

 month the bluff had been completely isolated and a secondary bluff 

 formed behind it out of the seaward face of the 0. lunata chalk 

 underlying the ' slope ' of grey chalk, which had by this time 

 become mainly a slope of 0. lunata chalk showing several lines of 

 flint dipping gently seaward. The cross section of this secondary 

 bluff showed gently arched lines of flint, from which it was clear 

 that this secondary bluff was the top of a gentle anticlinal fold 

 rising towards the land, exactly like the ridge forming the southern 

 part of the south bluff. It was, however, underlain where its base 

 was clear of sand by clay visibly continuous in the south bay with 

 the clay underlying the chalk masses. The same waves that had 

 breached the clay pinnacle had also cleaned the section in the south 

 bay, which is recorded by Fig. 17. The clay appeared to have 

 pressed upwards from under the mass of chalk nearer the 

 bluff and carried up with it on its surface the mass high up 

 in the cliff, for the two were connected by a very thin but 

 unbroken line of chalk which kept the clay above the masses of 

 chalk from quite touching the clay which emerged from beneath 

 them. A similar but more partial appearance was presented in the 

 north bay by the clay which emerged from imder the ' slope ' and 

 passed up into the cliff, only to arch over and, as before stated, pass 

 down beside and in under the erratic slice of chalk. Both the 

 masses in the south bay, i.e. the lateral section of the ' secondary 

 bluff' and the mass seen high up in the cliff, were composed of 

 0. lunata chalk with about a foot of grey chalk above separated by 

 the regulation grit seam with pebbles, and above the grey chalk 

 came about six inches of very regularly bedded sharp grey sand 

 with one interlaminated seam of black clay, and above the sand 

 about 2 feet of dark bluish grey clay. Between the two masses of 

 chalk the sand was cut out by the clay above it, but over the masses 

 themselves it was very regular. Above the bluff it passes into 

 a coarse gravel. 



The most recent exposures of the north side of the bluff itself 

 appear to show an actual inversion of all the chalk below the thick 

 flint. These flint lines are not clearly marked on this side, but their 

 appearance is quite consistent with and indeed suggestive of their 

 being actually inverted, and the hypothesis that they are actually 



