part 2] TERTIABY OUTLIERS OF THE WEST OF ENGLAND. 225 



Eocene. 



The westernmost deposits of Upper Eocene age in the Hampshire 

 Basin contain an assemblage of minerals not unlike that of the 

 Eocene of Devon. Topaz is present, although not abundant (as, 

 for instance, at Fordingbridge) ; it disappears as the deposits are 

 traced eastwards. Andalusite becomes rare, but occasional grains 

 are seen. Kyanite and staux*olite increase in abundance, and occur 

 in larger grains than those found in the Haldon sands. The pre- 

 sence of these two minerals is most simply explained by postulating 

 ;a marine or fluviatile current from the south-west into the Hamp- 

 shire Basin, the drainage there \miting with that from Devon which 

 brought the abundant tourmaline into the sediments. Blue tour- 

 maline becomes less abundant towards the east. Garnet is absent 

 or very rare in the Dorset and Hampshire Eocene, just as it is in 

 Devon. 



Little doubt thus exists, on petrological grounds, that the Upper 

 Eocene of Dorset and Hampshire was brought down by rivers 

 draining both the West Country and an area of metamorphic rocks 

 .on the south-west which contained kyanite and staurolite. Clement 

 Reid advocated a western origin for the Upper Eocene of Dorset, 

 because of the abundance of kaolin and the character of the pebbles 

 in the gravels. 1 In view of the greater variety of minerals in the 

 Eocene deposits generally of the London Basin, it is clear that, 

 while some ma}^ have been derived from the west and south-west, 

 .other areas must have been laid under contribution. 



Oligocene. 



The difference in character of the Devon deposits and the 

 •Oligocene strata of the Hampshire Basin is such that a comparison 

 of the petrological characters of the two is hardly likely to show 

 many points of similarity. Briefly (as noted on p. 220), it may 

 be stated that the western deposits contain a more restricted assem- 

 blage of minerals. The Oligocene of the Isle of Wight resembles 

 the Upper Eocene of the same area in its detrital minerals. The 

 topaz and andalusite which occur rarely in the Bovey Basin have 

 not been observed in Oligocene material from the eastern outcrop. 



Pliocene. 



The assemblage of minerals in the Cornish Pliocene, while far 

 from being a poor one, is by no means so varied as that from the 

 Boxstone Bed and various Crag deposits of East Anglia. Certain 

 striking differences are to be noted. Large red garnets, for 

 example, are among the most abundant and typical minerals in 

 East Anglia. Green hornblende, pyroxene, biotite, epidote, 

 chlorite, and other minerals are very abundant, but topaz is rare. 

 The source of the staurolite, andalusite, kyanite, and tourmaline in 



1 Q. J. G. S. vol. Hi (1896) p. 490. 



