Geoscience Reference
In-Depth Information
formation (Reid
1890
). Wood, Jun., for example, regarded the shell-beds of
Walton-on-the-Naze, comprising strongly-marked southern molluscan fauna, as
being the oldest of the Red Crag deposits and grouped the remainder of the
formation, in which northern shells occur more or less abundantly, under the
names of Suttonian and Butleyan. On the other hand, the renowned British
geologist Sir Joseph Prestwich (1816-1896) maintained that all the Red Crag beds
were contemporaneous. In view of these differences of opinion, Harmer decided to
re-examine the subject to determine, if possible, a more definite conclusion.
Accordingly, he spent 5 or 6 years revisiting every part of the Crag region, as well
as examining the more important Crag fossil collections with the intention of
obtaining evidence to establish the correct classification of these beds.
As a result of his research, Harmer subdivided the Red Crag into three for-
mations on the basis of their fossilized molluscan fauna, namely, Waltonian,
Newbournian and Butleyan (Figs.
3.9
and
3.10
).
Fig. 3.9 A formation of the Red Crag in Bawdsey Cliff, Suffolk showing the typical inclination
of about 30 to the horizontal of this obliquely bedded deposit (Wood Jun. and Harmer
1872
-
1874)
