CHAP. X.] CRETACEOUS PERIOD. 169 



The Upper Vectian sands next appear near Leighton and 

 Woburn, where they are 200 feet thick, and consist chiefly 

 of yellow and white sands, but have near the base a re- 

 markable seam of phosphate nodules, with fossils and 

 pebbles derived chiefly from Upper Jurassic strata ; there 

 are pebbles of quartz and chert like those of the Berkshire 

 beds, as well as fragments of an older Cretaceous rock. 

 The sands above are current-bedded, and the inclination 

 of the layers is generally south or south-eastward, showing 

 that the prevalent currents came from the north. Similar 

 beds with layers of nodules stretch through Bedford and 

 Cambridge as far as Ely. 



With regard to the subterranean extension of these 

 sands, it is known that they do not stretch far to the east- 

 ward. In Cambridgeshire they are present at Shelford 

 and Sawston, but appear to be absent at Saffron Walden in 

 the north of Essex. 1 In Hertfordshire they occur below 

 Hitchin, but are absent at Cheshunt and Ware. At Eich- 

 mond there are ten feet of calcareous sandstone, with a 

 pebble bed at its base, which consists of material derived 

 from Palaeozoic and Jurassic rocks; this is probably of 

 Vectian age, but no such beds occur under London. It is 

 clear, therefore, that the sands thin out against the slope 

 of the Palaeozoic rocks which underlie the east of England, 

 see fig. 3, p. 115. 



In Norfolk other beds begin to set in, the descending 

 succession being (3) ferruginous sandstone or Carstone, (2) 

 blue clay, (1) soft yellow and white sand. In Lincolnshire 

 the clay is thicker, and in Yorkshire the whole is repre- 

 sented by clays, which rest on still older Cretaceous clays 

 (see p. 164). The Lower Vectian consists of clays with 

 Pecten cinctus and Meyeria ornata (120 feet), and the Upper 



1 A boring here was carried through blue clays below the Chalk for 

 about 550 feet without any record of sand, and without finding any 

 water. (See " Mem. Geol. Survey," Expl. Sheet 47, p. 79.) 



