In
lithostratigraphy, coal measures are coal-bearing strata, with the term typically applied to European units of the Upper
Carboniferous System.
In the United Kingdom, the term is equivalent to regional components of the
Westphalian-age
Coal Measures Group. The group records the deposition of fluvio-deltaic sediments which consists mainly of
clastic rocks (
claystones,
shales,
siltstones,
sandstones,
conglomerates) interstratified with the beds of
coal. In most places, the coal measures are underlain by coarser clastic sequences known as
Millstone Grit, of
Namurian age. The top of the coal measures may be marked by an
unconformity, the overlying rocks being
Permian or later in age. In some parts of Britain, however, the coal measures grade up into mainly coal-barren
red beds of late
Westphalian and possibly
Stephanian age.[1][2] Within the
Pennine Basin, these barren measures are now referred to as the
Warwickshire Group, from the district where they achieve their thickest development.[3]
The coal measures formed during Westphalian and earliest Stephanian times in the European ('Heerlen')
chronostratigraphical scheme (which is approximately equivalent to the Middle
Pennsylvanian Series of the
IUGS global chronostratigraphical scheme).
The term coal measures has also historically been used in other parts of the world for coal-bearing successions of various ages, e.g. the
Permian coal measures of
Australia and the late
Cretaceous and early
Tertiary coal measures found in
New Zealand. However, these usages are mostly informal.
^Rayner, D H; Hemingway, J E (1974), The Geology and Mineral Resources Of Yorkshire, Leeds: Yorkshire Geological Society
^Edwards, W; Trotter, F M (1954), The Pennines and Adjacent Areas, British Regional Geology (Third ed.), London: HMSO. Natural Environment Research Council