Context
Geological Conservation Review (GCR) sites are selected for,
and grouped according to, GCR blocks, which are site-selection
categories for nationally important Earth science sites.
There are around 100 'blocks' and about 3,000 GCR sites in
Britain. Each 'block' represents a particular geological age
or Earth science theme, such as Marine Permian Stratigraphy,
Jurassic–Cretaceous Reptilia, Caledonian Igneous Rocks and
Quaternary of Scotland.
The landforms and sediments blocks are classified on
a regional basis, although the sub-division of time (usually
stratigraphical age) is an important factor. Sites were
selected to represent the stratigraphy of Quaternary successions
and the development of landforms.
During the Quaternary Period northern
Britain was covered by a succession of ice
sheets, while southernmost Britain was
not glaciated, although frozen ground conditions were
experienced. The wide variation of ice-age sediments and
geomorphological features across Britain, and the
large number of sites available for study, have required the use of
three principal themes for the basis of the Geological Conservation
Review Quaternary site selection:
1. Environmental history and change based on the
stratigraphy at different localities, their age and fossil content,
e.g. glacial-interglacial history, sea-level change;
2. Processes and patterns of landscape evolution,
e.g. glaciation, periglaciation;
3. The history and development of the flora and
fauna, e.g. vegetation history, evolution of
vertebrates.
In choosing GCR sites, comparisons were made between the
regional Quaternary blocks to ensure that certain categories of
site were not over-represented.