The
geology of Merseyside in northwest
England largely consists of a faulted sequence of
Carboniferous Coal Measures rocks overlain in the west by younger
Triassic and
Permian age
sandstones and
mudstones.
Glaciation during the present
Quaternary Period has left widespread
glacial till as well as erosional landforms. Other post-glacial superficial deposits such as river and
estuarine alluvium,
peat and blown sand are abundant.
Carboniferous
Carboniferous rocks underlie all of Merseyside but are only exposed to the east of the north-south Boundary Fault. The sequence encountered locally comprises (in descending order, youngest at top)
The oldest rocks to appear at or near the surface within the county are from the
Namurian Epoch. These are alternate units of sandstone ('flags' and 'grits') and mudstone with occasional
coal seams (known locally as 'mines') forming a part of the Millstone Grit Group. They are brought to the surface on the eastern side of the Upholland Fault and dip eastwards beneath
Billinge Hill. The full Namurian sequence hereabouts is:
Overlying the Millstone Grit sequence is the thick
Westphalian sequence of sandstones, mudstones and coal seams collectively referred to as the Pennine Coal Measures Group and which forms the
Lancashire Coalfield, the western part of which extends into Merseyside....
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