Woolwich 



and 

 Reading 

 Series. 



100 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



At Orpington the Woolwich and Reading group decreases in im- 

 portance. The following section was shown in a road-cutting at 

 Crofton Pound near that village. 



Orpington. p^^^ 



I. Fine yellow sand 6 



k. Dark grey clay Of 



_;. Mass of comminuted shells, chiefly Cyrena cuneiformis 1 



i. Yellow clay and concretionary slabs of earthy Umestone, full 



of the Ostrea Bellovacina 1 



h. Light brown clay Of 



g. Rough thin concretionary limestone full of Ostrea and Cyrena 2 



f. Mixed brown and grey clay 1^ 



e. Mass of broken shells (^Cyrena, Melania, Cerithium) in yel- 

 low clay 3J- 



d. Mottled bright red and Ught greenish clay 2-^ 



c. Brown clay, full of small flint-pebbles 1 



b. Bright yellow clay li 



a. Dark clayey green sand, passing down into very light-coloured 



loose green sand, with a few thin layers of flint-pebbles. . . 8 



Traces of the mottled clays are visible yet here. The lower part 

 of this group now often assumes the character of the Thanet Sands, 

 from which it can only be distuiguished by a few scanty seams of 

 pebbles. On the hill west of St. Mary's Cray the separation of the 

 two groups is however extremely well marked, as the pebbles form a 

 dense mass in a bed of green sand. 



Immediately north of the line just passed over is a district where, 

 amidst a most variable series and a large development of unfossiliferous 

 flint-shingle and sands, one section stands out in bold relief, and 

 almost alone there preserves the fauna of the group : for a short 

 distance near Bromley and Chiselhurst portions of the usually loose 

 and sandy beds are rendered solid by a calcareous cement ; and 

 at Sundridge Park, where they are occasionally worked, they present 

 a mass 25 to 30 feet thick of a hard light-coloured conglomerate, 

 with a few subordinate sand beds, abounding in fossils. The upper 

 beds in particular of this section show a strong false stratification 

 shelving 1 2° to 22° northward. The exact position of these strata 

 cannot be recognised in this section : I believe them, however, to 

 be synchronous with the upper sands at Lewisham and the pebbly 

 sands overlying the fossiliferous clays at Woolwich. The same beds 

 are occasionally solidified nearer to London, but nowhere to the same 

 extent as at Sundridge and beneath Chiselhurst Hill. 



Organic retnains, Sundridge Park Pit. 



Cerithium variabile, Desk. Glycimeris ? 



Corbula Regulbiensis, Mor. Melanopsis buccinoides, Fer. 



Cyrena cuneiformis, Fer. Melania inquinata, Desk. 



deperdita, Souk Modiola dorsata, Mor. 



tellinella. Desk. Natica glaucinoides, Sow. 



cordata, Mor. Neritina globulus, De/". 



intermedia, Mell. Nucula fragiUs, Desk. 



Fusus latus, Sou: Ostrea Bellovacina, Des/u 



