These Cambrian rocks are overlain unconformably by the Coal measures to the west, and by the Keuper beds to the east; the boundary of the area is, however, locally defined by lines of fault.
The basement beds of the Hartshill Quartzite are locally composed of fragments of the underlying volcanic rocks (Caldecote Beds). The Quartzite itself, which forms the chief road metal of the neighbourhood, is laid bare in a long series of quarries between Nuneaton and Hartshill.
The overlying purple and green shales of the Stockingford Beds range from Marston Jabet, south of Chilvers Coton to Atherstone Outwoods. The best section is seen in Parley Park Lane near Atherstone, and the fossils have been obtained from this section, from Atherstone Oakwoods, Camp Hill, and Marston Jabet.
The best section of the succeeding grey and black Shales occurs in the cutting of the Midland Railway near Stockingford, which gives its name to the formation. Their fossils have been procured from the rocks of this section; from the cutting at Chilvers Coton, the banks of the Coventry Canal, from Oldbury reservoir, Mawbornes and Merevale Park.
The numerous intrusive dykes of volcanic rock form a conspicuous feature in the geology of these Cambrian strata. They are formed of coarse-grained diorites, much quarried for road metal, kerbs, and setts. Good sections occur in the quarries near Tuttle Hill, in the railway cuttings near Stockingford and Chilvers Coton, and in quarries near Oldbury Reservoir.
A small patch of these Nuneaton Cambrians is met with on the north-western margin of the East Warwickshire coalfield, at Dost Hill, to the south of Tamworth. It consists of the usual annelide-bearing Stockingford Shales, pierced by an intrusive mass of diorite.
Lower Lickey Hills.—The core of the Lower Lickey Hills between Barnt Green and Rubery, about eight miles south of Birmingham, is formed of a mass of quartzite identical in all its main features with that of Hartshill, near Nuneaton.
At the village of Rubery, in an exposure on the roadside, it is seen to be unconformably overlain by fossiliferous Llandovery sandstone, the basement beds of which contain fragments of the underlying quartzite in abundance. At the south-western extremity of the Lower Lickey Range the quartzites contain fragments of igneous rocks, and appear to pass down into a series of felspathic grits, pierced by dioritic dykes similar to those of the Nuneaton District. Good sections of the quartzites are laid bare at Rubery Station, at the village of Rubery, and in a large quarry near the roadside, a mile northward from Kendall End. In the last-named locality the quartzites are seen greatly folded and faulted.
Wrekin District.—In the Wrekin area the great volcanic series of the hills is immediately overlain by a quartzite similar to that of the Hartshill and the Lickey, the basement bed similarly containing fragments of the underlying volcanic rocks. The quartzite is succeeded by the Hollybush sandstone, with its characteristic fossil, Kutorgina cingulata.