Stratigraphy
The Oxford English Dictionary defines Stratigraphy as ‘The branch of geology concerned with the order and relative position of strata and their relationship to the geological timescale’.
Stratigraphy is one of the key elements of geology and provides the basis for the subdivision of rock strata. This subdivision can be on the basis of rock type (lithostratigraphy), fossil content (biostratigraphy) or absolute age (chronostratigraphy).
The basic concept of stratigraphy was established by Nicholas Steno in the late 17th century and was developed by geologists such as William Smith and contemporary workers in the first half of the 19th century who laid down the basis for the approach to stratigraphy that is employed today.
A progressive refinement of the stratigraphy of the British Isles has occurred overtime and this continues as further research provides additional information and a more refined stratigraphic column.
Whilst identifying and recording Local Geological Sites (LGS) Cumbria GeoConservation has followed a well-established and accepted regional lithostratigraphy that has been developed over the past 200 years, starting with the 3 fold division of the geology of the central Lake District (‘the Clayslate, Greenstone and Greywacke’) described by Jonathan Otley in 1820 and culminating in detailed work currently being undertaken by UK Universities and the British Geological Survey.
In order to ensure consistency of approach Cumbria GeoConservation has chosen to follow the lithostratigraphy detailed in the latest BGS Regional Guide for the North of England (Stone et al, 2010). This lithostratigraphy is summarised in a number of tables that have adapted the information provided in the regional guide. These tables aim to cover all of the solid geology of Cumbria. Some of our Local Sites were designated more than 25 years ago and the lithostratigraphic information may now be out of date – this will be updated as individual sites are reviewed. The tables are as follows;
Ordovician – Borrowdale Volcanic Group (representative section only)
It should be noted that whilst for some elements of the stratigraphic column (e.g. the Permian/Triassic/Jurassic) the lithostratigraphy is relatively simple, sequences such as the Carboniferous are more complex; reflecting the varying nature of sedimentation in both time and space, but it is still possible to satisfactorily represent the whole region on one table. However, the Borrowdale Volcanic Group can exhibit such extreme lateral and vertical variation over small distances that it is not practical to represent the whole of the Lake District on a single table. In this case a representative section from a specific local area has been provided.
Reference
STONE, P, MILLWARD, D, YOUNG, B, MERRITT, J W, CLARKE, S M, McCORMAC, M, and LAWRENCE, D J D, 2010. British Regional Geology: Northern England (Fifth edition). (Keyworth, Nottingham: British Geological Survey).
