CHAP. XI.] HANTONIAN PERIOD. 225 



estuary into which rivers from the west emptied them- 

 selves. 1 



In the first pla.ee, the Lower and Middle Bagshots of the 

 London basin are certainly not the deposits of an open sea. 

 All who have recently studied these beds agree in regard- 

 ing the Lower Bagshot Beds as of freshwater origin and 

 either fluviatile or lacustrine deposits, and Mr. Irving 

 considers the middle group to be lagoon deposits in the 

 close neighbourhood of land, the waters of which were 

 kept in a partially saline condition by occasional intrusions 

 of the sea, and by percolation through fringing shingle 

 banks. 3 It is clear there was land to the north and 

 west of this area and open water to the south, but it is 

 probable that the ridge of the Wealden anticline was again 

 above the sea-level and contributed a share of the flint 

 pebbles that occur in the Middle and Upper Bagshot Beds. 



Secondly, there are clear proofs in the strata of the 

 Hampshire basin that this area was a gulf which received 

 the waters and the sediment of one or more rivers ; rivers 

 which had doubtless contributed their quota of sediment 

 to the London Clay.- The changes of level which closed 

 the episode of this clay formation converted the head of 

 the southern gulf into a broad alluvial plain through which 

 the rivers slowly made their way to the sea and probably 

 opened out at intervals into lagoon or lake-like expansions. 

 Thus Mr. G-ardner is of opinion that the most western beds 

 of Corfe, Studland, and Alum Bay were accumulated in a 

 wide valley or shallow lake, and he remarks that "the 

 complexity of the stratification suggests that two rivers 

 united in this valley, and shows plainly that the waters 

 must, in any case, have been rapid at times, and subject to 

 periodical fluctuations of volume." He infers also, " from 

 the absence of lignites in some parts of the series, that 



1 Gardner, " Proc. Geol. Assoc.," vol. vi. p. 95. 



2 " Quart. Journ. Geol. Soc.," vol. xliii. p. 389. 



