444 EOCENE PERIOD. CHAP. 



In a general view, the cainozoic beds of marine origin in the 

 vale or basin of the Thames belong mainly to the earlier or eocene 

 group : the meiocene and pleiocene strata (taking this last to 

 include all the successive 'crag' beds) are deficient. After a long 

 interval we find glacial, marine, and fresh-water deposits, of the 

 pleistocene age, to which the next chapter is devoted. 



Diagram CCI. Section across the Vale of Kennet. 

 C. Chalk. W. Woolwich beds. S. Sarsen stoiie. D. Drift. 



The best sections of these strata which fall within the area 

 o f the Map already referred to are found near Reading. 

 At Theale the following succession is clearly seen : 



ft. in. 

 g. The soil slightly mixed with pebbles of flint, with a few fragments of red 



quartzite and other northern stones 26 



/. Clay not laminated, penetrated by tubular traces of plant roots . .16 

 e. Yellow sand, of coarse grain with very small chips of flint (marten holes) I 6 



d. Pale laminated clays . . I 6 



c. Pale and brown laminated clay bands 26 



6. Ferruginous laminated bands I 6 



a. Brown bands, pebbly above, and again at the base pebbly and dark, with 



Ostrea bellovacina 20 



Beneath is chalk perforated in various directions to the 

 depth of a foot; and below this, chalk with flints in irregular 

 layers with variously directed joints. Here occurs Ananchytes 

 ovatus. 



The series at Katesgrove, near Reading, examined by Dr. Buck- 

 land a in 1817, may be thus described: 



ft. 



Surface deposit of clay, sand, and gravel ; this last composed of chalk, flint, 

 quartz, and brown compact sandstone. 



Loamy sand and clay, ferruginous below 1 1 



Clay, dark-red and mottled with grey 4 



Clay, ash -coloured, and fine sand of same tint 7 



Sand, micaceous, laminated, and partially mixed with clay .... 4 



a Geol. Trans., vol. iv. p. 276 (1817). 



