Geoscience Reference
In-Depth Information
Quaternary
A thin veneer of glacial, fluvial and aeolian
sediments and frost weathered debris. Widely distributed,
especially in lowlands and shallow marine basins. Sand and
gravel aggregates - construction, glass industries.
Jurassic, Cretaceous and Tertiary
Limestones, clays, chalk,
sandstone and ironstones in south-eastern lowland Britain;
offshore oil and natural gas. Building stone; cement, brick and
iron and steel and - formerly - chemical industries. Power and
petrochemical industries. Ground water.
Permo-Triassic
Magnesian limestone, marl, sandstones and
evaporites in English midland basins. Some building stone and
aggregates. Salt and related chemical industries, including
phosphates. Ground water.
Carboniferous
Limestone, grits and sandstones and coal
measures in Variscan orogen upland and fringes; some
hydrothermal mineralization (lead, zinc). Crushed limestone
aggregates and cement; building stones. Coal. Former
metalliferous mining and smelting industry.
Devonian
Sandstone, slate in English borderlands, southern
Ireland and Scottish lowlands. Some building and roofing stone.
Ground water.
Later Precambrian and Lower Palaeozoic
Volcanic, intrusive
and metamorphic rocks of former subduction zones and
Caledonian orogens forming highland and upland Britain; slates,
grits and sandstones; schists and gneiss. Hydrothermal
mineralization - gold, silver, lead, zinc, copper, tin; semi-precious
stones. Hard crushed rock aggregates; building and roofing
stone. Former extensive metalliferous and smelting industries.
Other igneous rocks (mainly Devonian and Tertiary age)
Granites and basalts in Cornwall (Devonian) and Tertiary volcanic
province of Northern Ireland and western Scotland. Hard crushed
rock aggregates; kaolin (china clay) from weathered granite.
0
200
km
(a)
(c)
X
1
Tension
fracture
X
2
Local
tension
Local
compression
X
3
Cross fractures
(2 sets)
Slate
Sandstone
Tension fracture
Shale
X
2
X
3
Shrinkage
fractures
Limestone
X
1
(b)
Bedding
planes
Cleavage
Fissility
Regional
(ex)tension
Regional compression
Figure 12.21
Principal stresses and their application to geological structures. Principal stresses operating on the cube (a) are
equal. Cube (b) has been compressed vertically and has responded by extending in one horizontal plane whilst conserving its
volume. (c) The application of these forces to a sedimentary rock sequence - which also possesses lithological fractures.
Source: Partly after Selby (1993)
