96 PEOF. MORRIS GEOLOGY OF THE LOXDOX BASIN 



Overlying the Thanet Beds occiirs an important and interesting 

 group, showing still more marked changes in the physical condi- 

 tions of the period. This group is generally known as the Wool- 

 wich AXD Eeadi>"g Beds, which were deposited under very different 

 conditions from those of the pre-existing marine beds below. They 

 present two distinct local facics ; hence the term "Woolwich and 

 Eeading Series," given by Prof. Prestwich. In the western and 

 northern area they are more marine, in the central and eastern 

 more fiuviatile and estuarine.* It was to the south or to the 

 south-west that there must have existed a considerable extent of 

 land consisting of the Chalk and Wealden rocks, through which 

 rivers flowed, bringing down a vast amount of sediment, to be 

 deposited over a considerable portion of the southern part of 

 the London area, as marked by the deposits at Woolwich, 

 Lewisham, Peckham, and in other districts. These indicate old 

 river-courses flowing into an estuary, from what is known of the 

 shells found in them. These shells, such as Unio, Pahidina, 

 Neritina, only exist in rivers, or some at least, at the mouths of 

 rivers, where brackish water prevails ; for many of them, such as 

 Cyreyia, Melania, Melanopsis, Ostrea, Cerithium, are brackish-water 

 forms. But what is understood in relation to this and other 

 localities is, that a far larger area of country was then submerged 

 or covered by deposits than at the preceding Thanet Sand period ; 

 for these beds can be traced from beyond Hungerford in Wiltshire 

 towards the eastern part of Kent, and also on the northern side 

 of the Thames into Suffolk. 



In the western area they consist of a series of clays and muds 

 deposited in a comparatively deep sea, showing very little life 

 except a few oysters ; but towards Reading there is evidence 

 of different conditions. Here occur plants, and plants of such a 

 character as are known only to grow upon land, and which 

 must have been carried on to the old sea bed. Further eastward 

 are seen the formations indicating the great series of fi*esh-water 

 and brackish deposits, evidence of rivers draining themselves from 

 a southern land. Wlien, however, we trace them over a still 

 more eastern area, we find them becoming more marine in their 

 character. Just as wc should expect to find in any large tidal 

 river a scries of fluviatile, estuarine, and marine deposits, some- 

 times intercalated, or with the mollusca partly intermixed ; so 

 the respective deposits of the Woolwich beds, as seen at Dulwich. 

 Charlton, and Upnor, seem to indicate a slight difference in their 

 faunas, which may have resulted from their having been accumu- 

 lated at a greater or less distance from the ancient cstuary.f 



* Prestwich, Quart. Journ. Oeol. Soc, vol. x. p. 78. 



t At Peckham and Dulwich I\iludina and Unio arc abundant, with somo 

 plants and also mammals, as Cori/phodon, etc. At Upnor Ci/thfrea and JWtitii- 

 ci'.lus are common, associated with Ci/rena ; at Charlton the chief brackish or 

 marine form is Ostrea, mixed with Cyrena and Mtlania. 



