GEOLOGY OF THE NORWICH DISTRICT 53 
noted that the majority of these shells are living species, and northern 
in character. The old names are retained to facilitate comparison with 
lists long published.) 
The detrital minerals found in the Norwich Crag differ but little 
from those of the earlier deposit, the Red Crag, and appear to indicate 
a southernly origin for each of the sediments. Beds of highly micaceous 
sands and clays occasionally occur, like those in the Chillesford Beds 
of Suffolk; these suggest that the parent rocks were of mica-schist 
type. 
at the base of the Norwich Crag, where it is seen to rest on the Chalk, 
is a bed of brown-coated flints, among which are found the famous 
‘ rostro-carinates ’ and other types of implements, described by Mr. J. E. 
Sainty in Chapter VIII. These implements afford evidence of the earliest 
appearance of man in Norfolk, but for many years the flaking was 
the subject of vigorous controversy. On the question as to whether the 
implements prove the existence of Pliocene man depends in turn the 
question as to whether the Norwich Crag is to be regarded as Pliocene— 
the long-established practice—or placed in the Lower Pleistocene, as 
E. Ray Lankester advocated so long ago as 1912. 
Whilst in Suffolk the Chillesford Beds are marked by a well-defined 
fauna and lithology, indicating their deposition under quiet estuarine 
conditions, in the district here described the homotaxially equivalent 
deposits are irregular and impersistent. The presence of comparatively 
thin seams (‘jambs’) of highly micaceous clay in sands and pebbly 
gravels has, despite their impersistence, led to correlation with the 
micaceous Chillesford Beds of Chillesford in Suffolk. F. W. Harmer 
has linked up the various occurrences of these beds and traced the ancient 
course of an estuary winding through Norfolk from Beccles to Rockland, 
Wroxham, and Burgh. H. B. Woodward preferred to map these variable 
beds with the Norwich Crag. Although in Suffolk the beds contain a 
molluscan fauna more recent and boreal than the Norwich Crag, the 
fauna in Norfolk is not well defined. 
The Weybourne Crag is of marine facies and is marked by the first 
appearance in Britain of the northern shell Tellina (Macoma) balthica 
Linné. The molluscan fauna is not rich, only about 50 species having 
been recorded, but JT. balthica itself often constitutes the bulk of the 
shells present. The deposit is well exposed in the Norfolk cliffs, and 
sands in which the same shell and its associates have been found occur 
in the Bure Valley and as far south as Norwich, but no farther. F. W. 
Harmer opined that the beds indicate a renewed incursion of the sea 
into Norfolk, following the opening-up of communication with the 
northern and Baltic areas. 
In recent years there has been a growing tendency to group together 
these ill-defined Crag divisions—that is, to revert to the practice adopted 
by the Geological Survey during the original mapping of Norfolk. 
Certainly, the separate divisions cannot be delineated on a map with 
any satisfaction to the surveyor. The officers of the Geological Survey 
were inclined, for example, to correlate the Weybourne Crag of northern 
Norfolk with the Chillesford Clay inland. Dr. J. D. Solomon sees in 
