Geoscience Reference
In-Depth Information
Fig. 3.10 Section of the map made by Wood, Jun. and Harmer showing the upper Tertiary
formations of the Crag district, including the Red Crag site in Bawdsey Cliff, Suffolk (Wood Jun.
and Harmer
1872
-1874)
These formations indicated the progressive retreat northwards and cooling of
the Crag Sea, with an ever-increasing proportion of boreal molluscan species. For
example, the southernmost exposures of the Red Crag, particularly at Walton-on-
the-Naze (appropriately assigned to the Waltonian formation), were considered to
represent the oldest Red Crag stage containing the warmest water faunas,
including many species that are rare or absent elsewhere in the Red Crag, whilst
the Newbournian and Butleyan formations outcropping further north probably
indicated cool temperate conditions (Figs.
3.11
and
3.12
).
