Geoscience Reference
In-Depth Information
Fig. 3.14 P680269 (1907) Harmer's geological excursion to Norfolk with Harmer (on left), the
German geologist, Carl C. Gottsche and the Austrian geologist, Emil Tietze above the Runton
Gap, Norfolk coast. (CP13/050 Reproduced by permission of the British Geological Survey
NERC. All rights reserved)
possibility that some of the remains may have been 'derived' that is washed out
from material deposited upstream in the proto-Rhine (Figs.
3.13
and
3.14
).
The deposition of the Chillesford and Cromer Forest Beds each representing a
slight upheaval of the western part of the Pliocene basin, was separated by a period
of depression, which led to the formation of the shallow-water marine sands of the
Weybourne Crag when the sea re-invaded part of the area now known as Norfolk
as far south as Norwich.
The molluscan faunae of the Chillesford and Cromer Forest Beds which were
considered to be boreal rather than arctic, were similar to those of the Norwich
Weybourne Crag zone, except that they comprised a smaller number of species
and contained throughout, in the greatest profusion, a shell, Tellina balthica, which
up to that time was unknown in the Crag Sea. The relative abrupt and abundant
appearance of this species at the Weybourne Crag stage suggested that commu-
nication was at that time opened up by a continued progress of the northeasterly
subsidence with a sea area, possibly the Baltic, in which this mollusc had estab-
lished itself (Figs.
3.15
,
3.16
,
3.17
,
3.18
,
3.19
and
3.20
).
