GCR block - Tremadoc (TRE)


Block Description

UK map showing distribution of GCR sites of GCR block TRE
Distribution of GCR sites of GCR block Tremadoc

The GCR sites selected for this GCR Block represent the British geological record of Earth history from about 491 to 483 million years ago (Ma), as represented by the rocks deposited during the first epoch of the Ordovician Period (495–440 Ma), which is the second period of the Palaeozoic Era (545 to 251 Ma). Rocks that formed during the Ordovician Period constitute the Ordovician System. Both Cambrian–Tremadoc and Tremadoc–Arenig boundary sites have their own GCR Blocks. See CAM-TRE and ARE-TRE.

The Cambrian and Ordovician rocks of Britain are essentially of marine origin; freshwater and subaerial deposits have been identified only in settings where volcanic edifices were raised above sea level. Within the marine setting there are rocks of the widest variety, from sandstones and limestones of the shoreline and shallow shelves to beds that accumulated in deep basins or on the continental slopes. Transects from shelf to basin are seen in both Cambrian and Ordovician rocks, and examples of shallow- and deep-water deposits are recognized in both Anglo-Welsh and Scottish areas.

The traditional series of the Ordovician System are Tremadoc (oldest), Arenig, Llanvirn, Caradoc and Ashgill (youngest). There are no globally agreed divisions of the Cambrian System, although ‘Lower’, ‘Middle’ and ‘Upper’ are widely used, but not universally defined.

Volume Introduction


Site List

Your selection found 9 GCR sites. Sites are sorted alphabetically by country, local authority and then by site name -
CodeNameCountryLocal AuthorityGrid RefGCR Site Account
3217Bullhill BrookEnglandShropshire CCSJ55480168Not available
532Cherme`s DingleEnglandShropshire CCSJ611069Not available
533Sheinton BrookEnglandShropshire CCSJ608042Not available
413Amnodd BwllWalesGWYNEDDSH806367Not available
535Pen BenarWalesGWYNEDDSH313283Not available
411Tyn-llanWalesGWYNEDDSH542404Not available
414Wern Road SectionWalesGWYNEDDSH543396Not available
412Y GarthWalesGWYNEDDSH595393Not available
410Cwm CrymlynWalesSOUTH WEST WALESSN347174Not available
Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access. Search Again