In order to have a common and precise language of geologic time to understand Earth’s history, it is necessary to have a series of fixed points in geological history which together define the stage sub-divisions of the geological timescale. The International Commission on Stratigraphy (ICS) and its predecessors primary aim has been to unite the individual ‘regional scales’ by agreement on a standardized nomenclature and hierarchy for these stages, defined by precise Global Boundary Stratotype Sections and Points (GSSP). These on-going decisions are primarily controlled by the activities of the task forces of the various ICS sub-commissions. Some of these GSSP’s are defined or proposed in Britain, primarily because Britain contains some globally significant geological intervals, particularly in the Mesozoic and mid Palaeozoic. A list of these sites and sections in Britain are shown below, the full global list of ratified GSSP's is updated by the ICS.
GSSP's Located in Britain
Kimmeridgian Stage: Proposed at Flodigarry coast section (Isle of Skye, NW Scotland), 57.6000°N 6.2000°W, First occurrence of ammonite Pictonia flodigarryensis, at the base of the Baylei Zone (awaiting final ratification).
Pliensbachian Stage. Ratified at Wine Haven, Robin Hood's Bay, Yorkshire Coast, England 54.4069°N 0.4975°W base of Bed 73b at Ammonite association of Bifericeras donovani and Apoderoceras sp.
Sinemurian Stage. Ratified at East Quantoxhead, SW England 51.1909°N 3.2364°W 0.90 m above the base of Bed 145 at the Ammonite FAD Vermiceras quantoxense, Vermiceras palmeri.
Ludfordian Stage. Ratified at Sunnyhill Quarry, near Ludlow, UK 52.3592°N 2.7772°W coincident with the base of the Leintwardine Formation, near the base of the Saetograptus leintwardinensis Graptolite zone. More
Gorstian Stage. Ratified at Pitch Coppice, near Ludlow, UK 52.3592°N 2.7772°W coincident with the base of the Lower Elton Formation, at the FAD of Graptolite Saetograptus (Colonograptus) varians.
Homerian Stage. Ratified at Whitwell Wood, Sheinton Brook, Homer, near Wenlock Edge, UK 52.6156°N 2.5647°W within upper part of the Apedale Member of the Coalbrookdale Formation at the FAD of Graptolite Cyrtograptus lundgreni.
Sheinwoodian Stage, and the base of the Wenlock Series. Ratified at Hughley Brook, UK 52.5811°N 2.6389°W base of the Build was Formation, between the base of acritarch biozone 5 and LAD of conodont Pterospathodus amorphognathoides.
Telychian Stage ( 436 ± 1.9 Ma). Ratified at the Cefn-cerig Road Section, Wales, UK 51.9700°N 3.7900°W within the Wormwood Formation, just above Brachiopod LAD Eocoelia intermedia and below FAD of Eocoelia curtisi.
Aeronian Stage (439 ± 1.8 Ma). Ratified at Trefawr Track Section, Wales, UK 52.0300°N 3.7000°W within Trefawar Formation, at FAD of Graptolite Monograptus austerus sequens.
Rhuddanian Stage, and base of the Silurian and base of the Llandovery Series. Ratified at Dob's Linn, Scotland 55.4400°N 3.2700°W, 1.6 m above the base of the Birkhill Shale Formation, at FAD of Graptolite Akidograptus ascensus.
Other important sections in Britain across stage boundaries
The ratified GSSP for the base of the
Hettangian Stage and base
Jurassic is in
Austria. Two key sections across this boundary in the UK are at St
Audrie's Bay (Somerset) and
Waterloo Bay (Northern Ireland).