The Geopark extends across territory underlain by
sedimentary rocks of
Silurian,
Devonian,
Carboniferous,
Permian and
Triassic age together with some limited outcrops of
igneous rocks.
Coal,
ironstone,
limestone,
fireclay, brick clay and building stones have all been exploited in the area in the last few centuries. Evidence is also present for the margins of both the
Anglian icesheet and the
Devensian icesheet.
Silurian rocks The oldest rocks which outcrop at the surface within the Geopark are the early
Silurian shales and limestones which are seen in a series of
faulted and
folded inliers between
Lye in the south and
Ettingshall Park in the north. There is a further area of Silurian rocks exposed between
Walsall,
Gravelly Hill Interchange and
Aldridge. The sequence locally (in
stratigraphic order i.e. uppermost/youngest, at top): • Raglan Mudstone Formation (mudstone and siltstone) • Temeside Mudstone Formation (mudstone, siltstone and sandstone) •
Downton Castle Sandstone Formation •
Whitcliffe Formation (siltstone/mudstone/limestone, formerly Upper Ludlow Shales) •
Aymestry Limestone Formation (limestone/mudstone) •
Lower Ludlow Shales Group •
Much Wenlock Limestone Formation (comprises three sub-units; Lower Quarried Limestone Member, the Nodular Limestone Member and the Upper Quarried Limestone member each of which comprises both limestone and mudstone) •
Coalbrookdale Formation (green-grey mudstones, formerly known as the Grey or Wenlock shales) • Barr Limestone Formation (grey limestone, mudstone) The Barr Limestone is of
Sheinwoodian age (433-430.5 Ma (million years ago)), the Much Wenlock Limestone of
Homerian age (430.5-427 Ma) with the Coalbrookdale Formation being transitional between the two: all three formations are of
Wenlockian age (c.433-427 Ma). The youngest three of the Silurian formations dates from the
Pridoli epoch (423-419 Ma), towards the end of the period, and are regarded as the lowest/earliest part of the
Old Red Sandstone succession in this region. The Much Wenlock limestones were extensively quarried at the Wren's Nest inlier.
Dudley Castle is built upon a neighbouring inlier.
Devonian rocks The Clee Sandstone Formation, which outcrops to the west and northwest of Sedgeley, originates in the Devonian period and is of
Emsian age (c.408-393 Ma). The sandstone strata which dip moderately away to the northwest, form a part of the Old Red Sandstone succession. These rocks may be seen as outlying parts of the Anglo-Welsh Basin.
Carboniferous intrusive rocks A series of
dolerite and
basalt intrusions occur within the Carboniferous sequence including the Brewin's Bridge microgabbro
dyke, London Fields basalt
sill and Rowley Regis microgabbro
lopolith. Associated with these is a basaltic
vent at Barrow Hill. ==Geography==