1850.] 



PRESTWICH ON THE LOWER TERTIARY STRATA. 



259 



tiaries. They enable us to trace the sands and mottled clays with- 

 out much difficulty over a large district ; but although these lower 

 tertiary beds are so frequently worked, and their relation to the 

 chalk underlying them is often shown, the sections nevertheless 

 rarely exhibit the overlying lower beds of the London clay. 



At the base of the chalk hills between Inkpen and Basingstoke 

 there are a considerable number of sections, more or less perfect, 

 of these lower tertiary beds. One of the best and most illustrative 

 is in a brick-field at Itchingswell, two miles westward of Kingsclere. 

 (See fig. 4.) 



Fig. 4. — Section at Iti/ / // 



d ~~t b 



b. London clay ; upper part bluish grey passing down into brown ; sandy at base ; a few calca- 



reous concretions, and a few fossils. (The lower part of this bed should perhaps be in- 

 cluded in "c") 



c. Ferruginous sand and iron sandstone mixed with green sand, and full of round flint pebbles, 



varying in size from 1 to 14 inches in diameter ; no fossils except a few teeth of Lamnce, 



d. Mottled clay and sands. 



The chalk outcrops at a distance of about 50 feet from " e." 



Organic remains of stratum "c," at Itchingswell. 



Cancellaria laeviuscula, Desh. Nucula. 



Cytherea obliqua, Desh. Panopsea intermedia, Sow. 



Ditrupa plana, Sow. sp. Pectunculus Plumsteadiensis, Sow. 

 Ostrea, large species. 



These fossils occur at the base of "6," just above "c." 



A section at Chinham, one mile and a half north-east of Basing- 

 stoke, on the line of railway from that town to Reading, showed the 

 basement conglomerate bed passing gradually upwards into the mass 

 of the London clay. The organic remains were numerous, but in a 

 very friable state. (See fig. 5.) 



Fig. 5. — Section at Chinham. 



•London clay ; thin-bedded brown clay with- 

 out fossils passing downwards into dirty 

 yellow sands with seams of brown clay, 

 and then into a sandy light-coloured clay 

 " c," with seams of green sand and a few 

 round flint pebbles occasionally concreted 

 into small flat masses by carbonate of 

 lime ; traces of vegetable matter ; shells 

 abundant in the seams and patches of 

 green sand, but very friable and generally 

 in the state of casts. Average thickness 

 of " c" 5 feet. 

 Mottled red and brown clays ; upper surface slightly uneven and worn. 



The junction with the chalk, which crops out immediately on the 

 opposite side of the small valley formed in these lower sands, is not 

 exposed. 



Organic remains of stratum '^c,*' at Chinham. 



Cassidaria striata. Sow. Fusus, small species. 



Cardium Plumsteadiense, Sow. Modiola elegans, Sow. 



Cytherea ovalis, var. ?, Sow. Natica glaucinoides. Sow. 



Ditrupa plana, Sow. sp, Hantoniensis> Pilk. 



