The Clackmannan Group is the name given to a suite of rocks of late
Dinantian and
Namurian age laid down during the
Carboniferous
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...
period in the
Midland Valley of
Scotland
Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
.
Description
The Group comprises a lower
unit of coarse
sandstone
Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
s,
siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.
Although its permeabil ...
s,
mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...
, and
limestone
Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
s with thin
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal i ...
s and
ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.
Not to be c ...
s known as the Lower Limestone Formation, an overlying sequence of similar rocks known as the Limestone Coal Formation, then an Upper Limestone Formation and at its top the sandstones of the Passage Formation. This last formation also includes
fireclays, siltstones, mudstones, ironstones, coal and
seatrocks.
The Clackmannan Group conformably overlays the rocks of the
Strathclyde Group
The Strathclyde Group is a Group (geology), geological group found in the Central Lowlands, Midland Valley of Scotland. It preserves fossils of Visean, the Visean age (early Carboniferous Period (geology), period).
See also
* List of fossilife ...
and underlays the
Coal Measures, this latter boundary also being
conformable.
Paleontology
Remains of the prehistoric shark †''
Cladodus elegans''
Newberry & Worthen, 1870 (braincase and a tooth) have been found in the Lower Limestone Formation.
[The Braincase and Jaws of Cladodus from the Lower Carboniferous of Scotland. Michal Ginter and John G. Maisey, Palaeontology, March 2007, Volume 50, Issue 2, pages 305–322, ]
See also
*
Fossil Grove
References
{{reflist
Geological groups of the United Kingdom
Geologic formations of Scotland
Fossiliferous stratigraphic units of the United Kingdom
Carboniferous System of Europe
Carboniferous Scotland
Carboniferous southern paleotropical deposits