Yol. 52.] PLIOCENE DEPOSITS OE HOLLAND. 771 



deserves to be noticed. The Chillesford Beds have no doubt been 

 exposed to considerable denudation ; at the same time the dotted 

 lines which I have drawn may indicate approximat el)- a part at least 

 of the tortuous course of this ancient estuary. 1 Beyond these limits 

 there occur in places thin layers of laminated clay, the age of* which 

 is doubtful. If these are of Chillesford age they may have been 

 deposited in time of flood beyond the usual channel, or the stream 

 may have changed its course from time to time. It is possible also 

 that the Chillesford Beds may be present below the water-level in 

 some part of East Norfolk, but if so they are the marginal deposit 

 of a wider body of water than that which is suggested on the map, 

 and their supposed boundary to the east must be shifted accordingly. 

 On the whole it seems more probable that the abrupt change from 

 sand to clay, and again from clay to the beds of gravel next to 

 be described, was due to some alteration in the geographical con- 

 ditions of the East Anglian portion of the Pliocene basin, such as 

 •the substitution of an estuary for a bay, rather than to a difference, 

 from some unexplained cause, in the character of the sediment 

 brought into the area. 



It is in Norfolk — that is, towards the mouth, as it seems to me, of 

 the supposed estuary of the Chillesford period — that the beds occur 

 upon which Mr. Woodward lays so much stress. In that district 

 ■cases are occasionally met with where laminated clay is inter- 

 stratified with sand and gravel, sometimes apparently of Norwich 

 -Crag age, but which at other times seem to belong to the later 

 period of the pebbly series. One such case especially occurs to me, 

 that at Hartford Bridge, 2 miles south of Norwich, to which I called 

 Mr. H. B. Woodward's attention and which we visited together 

 many years ago. This was figured by him, 2 but at present it 

 indicates still more plainly the connexion between the Chillesford 

 Clay and the Bure Valley Beds. The section now shows 10 feet 

 of laminated brick-earth, more sandy than the typical Chillesford 

 Clay of Suffolk, interbedded with fine pebbly gravels containing a 

 •considerable admixture of stones of southern origin. It seems to 

 me that these beds may belong to a period when the submergence 

 which afterwards carried the sea of the Bure Valley Crag (referred 

 to below) over a considerable part of Norfolk and Suffolk was com- 

 mencing, but before it had proceeded far enough to put an end 

 altogether to the deposition in places of laminated estuarine beds 

 containing mica brought down from the south. The beds present 

 in the Hartford Bridge section may thus be intermediate between 

 the Chillesford Clay and the Bure Valley Crag, and it is not difficult 

 to understand that there may be others, although it may not be 

 easy to distinguish them, which similarly connect the Chillesford 

 Clay with the Norwich Crag. 



Succeeding the Chillesford Clay are some fossiliferous beds of sand 

 and pebbly gravel, composed principally of flint, but containing, as 



1 Estuarine deposits not only imply an estuary, but also indicate the position 

 which it occupied. 



2 Mem. Geol. Surv. Norwich, 1881, pi. iii. fig. 7. 



