The Warwickshire Group is a lithostratigraphic

Lithostratigraphy

Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology...

 unit of rock strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 defined within the British Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 system. Within the Pennine Basin

Pennine Basin

The Pennine Basin is a sedimentary basin which was active during the Carboniferous Period and which reached from the Southern Uplands of Scotland in the north to the former Wales-London-Brabant Massif in the English Midlands to the south...

 it overlies (ie postdates) the Coal Measures Group

Coal Measures Group

The Coal Measures Group is a lithostratigraphical term coined to refer to the coal-bearing succession of rock strata which occur in Great Britain within the Westphalian Stage of the Carboniferous Period. The Coal Measures Group is preceded by the Millstone Grit Group which is of Namurian age...

 and is deemed to be of late Westphalian

Westphalian (stage)

The Westphalian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 313 and 304 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Westphalian is named for the region of Westphalia in western Germany where strata...

 and Stephanian

Stephanian (stage)

The Stephanian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 304 and 299 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series...

 age. It contains the youngest Carboniferous rocks in Britain.
The name Warwickshire Group

Warwickshire Group

The Warwickshire Group is a lithostratigraphic unit of rock strata defined within the British Carboniferous system. Within the Pennine Basin it overlies the Coal Measures Group and is deemed to be of late Westphalian and Stephanian age...

 is a relatively recent one, replacing a variety of earlier names for the succession of coal-barren red-beds such as Barren Coal Measures and Red Measures which overlie the productive coal measures. It is derived from the Warwickshire Coalfield

Warwickshire Coalfield

The Warwickshire Coalfield extends between Warwick and Tamworth in the English Midlands. It is about 40km / 25 miles from north to south and its width is around half that distance. Its western margin is defined by the 'Western Boundary Fault'. In the northeast it abuts against steeply dipping...

where they achieve their thickest development.