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==Black Metals Member [http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=BKME (BKME)], Carboniferous, Midland Valley of Scotland ==
Black Metals Member is part of the [[Limestone Coal Formation]]
=== Name ===
Clough et al. (1916)<ref name="Clough16">Clough, C T, Hinxman, L W, Wright, W B, Anderson, E M, and Carruthers, R G.1916.The economic geology of the Central Coalfield of Scotland. Area V.''Memoir of the Geological Survey of Great Britain'' (Scotland)</ref> previously named the member the Black Metals. It should not to be confused with the locally named Black Metals (Haughton) Marine Band of the Cumberland Coalfield which is Duckmantian (Westphalian.B) in age.

=== Lithology ===
The Black Metals Member is a thick, laterally persistent dark grey mudstone (Read, 1965<ref name="Read65">Read, W A.1965.Shoreward facies changes and their relation to cyclical sedimentation in part of the Namurian east of Stirling, Scotland.''Scottish Journal of Geology'', Vol. 1, 69–92</ref>) distinguished by one or more beds, termed ‘Black Metals Marine Bands’. Read (1965)<ref name="Read65"></ref> described a sequence within the member of mudstone with ''Lingula'' at the base; overlain by mudstone with nonmarine bivalves or unfossiliferous mudstone, overlain by mudstone with a varied marine fauna that comprises the middle part of the member; which in turn is overlain by mudstone with nonmarine bivalves. The characteristic lithologies of the member vary laterally within the Midland Valley of Scotland. On the western side of the Central Coalfield in the Glasgow district strata that comprise the member are described and illustrated by Hall et al. (1998, fig..11<ref name="Hall98">Hall, I H S, Browne, M A E, and Forsyth, I H.1998.Geology of the Glasgow district.''Memoir of the British Geological Survey'', Sheet 30E (Scotland).</ref>) as black and dark grey, carbonaceous mudstones and silty mudstones with characteristic development of brownish-grey clayband ironstone nodules (California Clayband Ironstone). Sandstones are restricted to thin beds, collectively 2 or 3 m thick in a total thickness interval of about 32 m. Eastwards from the Central Coalfield the member includes siltstone and sandstone beds that increase progressively in number and thickness to become the predominant lithology; seatearth and coal also appear (Read, 1965<ref name="Read65"></ref>). In the western coastal Irvine district, the Logan’s Bands, comprising thin beds of ironstone in a laterally persistent mudstone sequence, have been correlated with the Black Metals Member of the Glasgow district (Richey et al., 1930<ref name="Richey30">Richey, J E, Anderson, E M, and MacGregor, A G.1930.The geology of north Ayrshire.''Memoir of the Geological Survey of Great Britain'', Sheet 22 (Scotland)</ref>).

=== Genetic interpretation ===
Beds containing shelly marine faunas indicate a marine depositional environment (Wilson, 1967<ref name="Wilson67">Wilson, R B.1967.A study of some Namurian marine faunas of central Scotland.''Transactions of the Royal Society of Edinburgh'', Vol. 66, 445–490</ref>). However, beds with shells including ''Naiadites'' sp., indicate nonmarine depositional conditions.

=== Stratotype ===
The type section is north of Glasgow in the Cardowan No. 2 Bore (BGS Registration Number NS66NE/66) (NS 6706 6752) from 470 to 502.3 m depth. Reference sections are provided in Fife, at the Dora Opencast Coal Site, Area G (BGS Registration Number NT19SE/550) (NT 1830 9100 to 1860 9130), and in Midlothian, in the Monkton House Borehole (BGS Registration Number NT37SW/43) (NT 3325 7044) from about 888 to 907 m depth (see Tulloch and Walton, 1958, plate 3<ref name="Tulloch58">Tulloch, W, and Walton, H S.1958.The geology of the Midlothian coalfield.''Memoir of the Geological Survey of Great Britain'' (Scotland)</ref>). Both reference sections include interbedded sandstone and coal-bearing strata within the member.

=== Lower and upper boundaries ===
In the Central Coalfield the base of the mudstone comprising the member is picked at the top of the Black Metals Basal Coal (Forsyth and Read, 1962<ref name="FandR">Forsyth, I H, and Read, W A.1962.The correlation of the Limestone Coal Group above the Kilsyth Coking Coal in the Glasgow–Stirling region.''Bulletin of the Geological Survey of Great Britain'', No. 19, 29–52</ref>). Eastwards the base is picked at the top of a laterally equivalent seatearth and correlated to a thin coal above the Torrance Four-inch Coal farther east in Fife (Read, 1965, fig. 2<ref name="Read65"></ref>). Westwards, in the Glasgow district, marine fossils are recorded just above the base of the Black Metals Member, the boundary being picked at the roof of the Upper Garscadden Coal which here may be developed as a blackband ironstone (Upper Garscadden Ironstone) (Hall et al., 1998, fig. 11<ref name="Hall98"></ref>; Forsyth and Read, 1962<ref name="FandR"></ref>).

At its upper boundary in the Central Coalfield, mudstone of the Black Metals Member is interbedded with sandstone of the overlying Limestone Coal Formation (Figure 6, Column 4). The boundary is picked at the base of the lowermost bed of coarse siltstone or sandstone (Read, 1965<ref name="Read65"></ref>). In the Bo’ness area of the Livingson district (Read, 1965<ref name="Read65"></ref>), the erosive base of the sandstone has cut down into the member, or it is abruptly overlain by lavas of the Bathgate Hills Volcanic Formation. In the Glasgow district the upper boundary of the Black Metals Member is just below (within about 5 m of) the Knott Coal horizon (Hall et al., 1998, fig..11<ref name="Hall98"></ref>).

=== Thickness ===
Read (1965)<ref name="Read65"></ref> described the thickness of the member as exceeding that of typical fining-upwards cycles of the Limestone Coal Formation, which are usually about 3–10.m thick. North of Glasgow on the western side of the Central Coalfield in the Cardowan No. 2 Bore (see above) the member is 32.3 m thick (from 470 to 502.3 m depth) (Hall et al., 1998, fig. 11<ref name="Hall98"></ref>). The thickness is similar in the Kincardine and Fife–Midlothian basins. However, in the Kincardine Basin in west Fife the thickness of the member increases eastwards from 33 m to a maximum of 66 m, associated with the lateral change to an increasingly sandstone-bearing succession (Francis et al., 1970, p. 190, and plate 8<ref>Francis, E H, Forsyth, I H, Read, W A, and Armstrong, M.1970.The geology of the Stirling district.''Memoir of the Geological Survey of Great Britain'', Sheet 39 (Scotland).</ref>).

=== Distribution and regional correlation ===
Central Scotland, but not identified in southern and central Ayrshire by Simpson and MacGregor (1932)<ref>Simpson, J B, and MacGregor, A G.1932.The economic geology of the Ayrshire coalfields, Area IV.''Memoir of the Geological Survey'' (Scotland)</ref> or Eyles et al. (1949)<ref>Eyles, V A, Simpson, J B, and Macgregor, A G.1949.Geology of central Ayrshire.''Memoir of the Geological Survey of Great Britain'', Sheet 14, parts 8, 13, 15 and 22 (Scotland)</ref>.

=== Age and biostratigraphical characterisation ===
Pendleian. The ‘Black Metals Marine Bands’ yield macrofossils in most parts of central Scotland although in some areas only ''Lingula'' is present. The annelid ''Serpuloides carbonarius'', the brachiopods ''Buxtonia'' spp., ''Pleuropugnoides'' cf. ''pleurodon'' and ''Lingula'' spp. and the bivalve ''Streblopteria ornata'' are the main forms. The bivalve ''Aviculopinna mutica'' is commonly present in Midlothian and Fife, but has not been found elsewhere (Wilson, 1967<ref>Wilson, R B.1967.A study of some Namurian marine faunas of central Scotland.''Transactions of the Royal Society of Edinburgh'', Vol. 66, 445–490</ref>). The member also includes beds with a nonmarine shelly fauna including ''Naiadites'' sp. The Logans Bands in the western coastal Irvine district contain ''Lingula'' and ''Naiadites'' or nonmarine bivalves (Monro, 1999<ref>Monro, S K.1999.Geology of the Irvine district.''Memoir of the British Geological Survey'', Sheet 22W, part 21E (Scotland)</ref>).

== References ==
<references/>
[[Category:Carboniferous lithostratigraphical nomenclature]]

Black Metals Member - Revision history

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Geosource>Volunteer 01 at 10:03, 7 July 2015