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The Pennant Measures is the traditional name for a sequence of sedimentary rocks of the South Wales Coalfield. They were also referred to as the Upper
Coal Measures
In lithostratigraphy, the coal measures are the coal-bearing part of the Upper Carboniferous System. In the United Kingdom, the Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coal ...
and assigned to the Westphalian 'C' and Westphalian 'D' stages of the Carboniferous Period. The Pennant Measures were divided into the Lower Pennant Measures and the Upper Pennant Measures, differing from the underlying Middle and Lower Coal Measures in being principally of sandstone units – known collectively as the Pennant Sandstone – with mudstone being the subsidiary rock type. Numerous coal seams occur within the Pennant Measures though they are less common than in the underlying Coal Measures.British Geological Survey 1:50,000 map sheet 231 'Merthyr Tydfil' & accompanying memoir.
However recent reclassification of the sequence has resulted in the definition by the British Geological Survey
The British Geological Survey (BGS) is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research.
The BGS h ...
of the Pennant Sandstone Formation as a sub-unit of the newly established Warwickshire Group
The Warwickshire Group is a lithostratigraphic unit of rock strata defined within the British Carboniferous system. Within the Pennine Basin it overlies (i.e. postdates) the Coal Measures Group and is deemed to be of late Westphalian and St ...
. The formation is recognised to be of Bolsovian to 'Westphalian D' age. It overlies the uppermost strata of the newly defined South Wales Coal Measures Group
The South Wales Coal Measures Group is a lithostratigraphy, lithostratigraphical group (stratigraphy), term referring to the coal-bearing succession of rock stratum, strata which occur in South Wales within the Westphalian (stage), Westphalian sta ...
and underlies the rocks of the succeeding Grovesend Formation
Grovesend ( cy, Pengelli; ) is a village in the community of Grovesend and Waungron ( cy, Pengelli a Waungron), City and County of Swansea in Wales. The community has a population of 1,131.Craig y Llyn where they are represented by the Hughes Member.
The sandstone where quarried both in South Wales and the Bristol area for use in paving and roofing is also known as Pennant Stone.
The sandstone where quarried both in South Wales and the Bristol area for use in paving and roofing is also known as Pennant Stone.
References
{{Reflist Sandstone formations Coal in Wales Geology of Wales Carboniferous Wales Carboniferous System of Europe Geologic formations of the United Kingdom Stratigraphy of the United Kingdom