Marsden Formation is part of the Millstone Grit Group
The new name Marsden Formation is proposed to identify all Millstone Grit Group strata of Marsdenian age. The Marsden Formation is equivalent to the former Middle Grit Group of Bradford (Stephens et al., 1953), a term considered unsuitable. The new name was chosen from Marsden (SD 030 124), which provides excellent sections representative of much of the lower part of the Marsdenian succession, and is also the location of the basal stage stratotype (Ramsbottom, 1981).
Fine- to very coarse-grained and pebbly feldspathic sandstone, interbedded with grey siltstone and mudstone, and subordinate marine black shales, thin coals and seatearths.
During the Marsdenian, shallow-water deltas dominated, extending by late Marsdenian times across the entire Pennine Basin. Early Marsdenian deltas, including that associated with the East Carlton Grit in Yorkshire and Alum Crag Grit in Lancashire, infilled the basin following the major transgression associated with the Bilinguites gracilis Marine Band. These deltas are relatively elongate in the flow direction, generally towards the south and show evidence of gravity-flow sedimentation in the delta-fronts (Wignall and Maynard, 1996). Later deltas are laterally persistent sheet sand bodies. In the Goyt and Widmerpool troughs the turbidite-fronted deep-water deltaic successions of the Roaches and Ashover grits show a palaeocurrent towards the north-west, but have typical northerly sourced petrography (Jones and Chisholm, 1997). These systems appear to infill the Widmerpool Trough, flowing along the axis of the trough. Up to 600 m of Marsdenian strata are recorded between Preston and Macclesfield (Collinson et al., 1977) infilling the accommodation space to the south and west of the thick Kinderscoutian succession. Heavy mineral studies have demonstrated the northerly provenance of the Ashover Grit and Chatsworth Grit (Chisholm and Hallsworth, 2005).
The partial type section is a stream section at Park Clough, Hey Green near Marsden, West Yorkshire (SE 0299 1246), where 20 m of dark grey mudstone from the lower part of the Marsden Formation includes the Bilinguites gracilis Marine Band, above 15 m of cross-bedded sandstone of the Hebden Formation (Ramsbottom, 1981).
Lower and upper boundaries
The sharp conformable base of the formation is taken at the base of the dark grey fissile mudstone of the Bilinguites gracilis Marine Band, with eponymous fauna where the formation overlies the Hebden Formation. In the southern part of the Askrigg Block (Figure 15, Column 5), where the marine band is absent, the base of the formation is taken at the base of the Wandley Gill Shale, described by Wilson and Thompson (1965) as 3 m of shale with a Lingula band at the base, overlying a seatearth at the top of the Upper Brimham Grit. In the Stainmore Trough the base of the formation is taken at the base of a 6 m-thick shale with Productus carbonarius, which overlies a 0.15 m-thick shaly coal (Owens and Burgess, 1965). In the southern part of the Central Pennine Basin the base of the formation is taken at the base the first thick quartz-feldspathic sandstone of Marsdenian age present above the Bowland Shale Formation.
The top of the formation is taken at the sharp conformable base of the dark grey, fissile mudstone of the Cancelloceras cancellatum Marine Band (G1A1) with eponymous fauna, overlain by a dark grey mudstone-dominated succession in the lower part of the Rossendale Formation (Figure 9, Column 17; Figure 15, Column 5). In the Stainmore Trough, the equivalent of this marine band, but lacking the diagnostic ammonoid fauna, was referred to as the Swinstone Bottom Marine Band (Owens and Burgess, 1965).
Up to 600 m thick between Preston and Macclesfield; Bradford 275 m; north Derbyshire 450 m; 15 m thick in the Kirkby Malzeard area of the Askrigg Block; 40 m thick in the Stainmore Trough.
Lancashire and West Yorkshire between Lancaster (SD 47 61) and Harrogate (SE 30 55), extending southward to north Staffordshire (SK 06), and the Askrigg Block and Stainmore Trough.
Age and biostratigraphical characterisation
Marsdenian (R2). The base of the formation is taken at the base of the Bilinguites gracilis Marine Band and the top at the base of the Cancelloceras cancellatum Marine Band (G1a).
In both the Askrigg Block and Stainmore Trough areas the succession comprises a lower mudstone-dominated and upper sandstone-dominated unit. On the Askrigg Block the former unit is referred to as the Wandley Gill Shale (see Wilson and Thompson, 1965) and the latter unit as the Wandley Gill Sandstone (see Ramsbottom et al., 1978).
- Stephens, J V, Mitchell, G H, and Edwards, W.1953.Geology of the country between Bradford and Skipton.Memoir of the Geological Survey of Great Britain, Sheet 69 (England and Wales).
- Wignall, P B, and Maynard, J R.1996.High-resolution sequence stratigraphy in the early Marsdenian (Namurian, Carboniferous) of the central Pennines and adjacent areas.Proceedings of the Yorkshire Geological Society, Vol. 51, 127–140
- Jones, C M, and Chisholm, J I. 1997.The Roaches and Ashover Grits: sequence stratigraphical interpretation of a ‘turbidite fronted delta’ system.Geological Journal, Vol. 32, 45–68.
- Collinson, J D, Jones, C M, and Wilson, A A.1977.The Marsdenian (Namurian R2) succession west of Blackburn: implications for the evolution of Pennine Delta Systems.Geological Journal, Vol. 12, 59–76.
- Chisholm, J I, and Hallsworth, C R.2005.Provenance of Upper Carboniferous sandstones in east Derbyshire: role of the Wales–Brabant High.Proceedings of the Yorkshire Geological Society, Vol. 55, 209–233.
- Wilson, A A, and Thompson, A T.1965.The Carboniferous succession in the Kirkby Malzeard area, Yorkshire.Proceedings of the Yorkshire Geological Society, Vol. 35, 203–227.
- Owens, B, and Burgess, I C.1965.The stratigraphy and palynology of the Upper Carboniferous outlier of Stainmore, Westmorland.Bulletin of the Geological Survey of Great Britain, No. 23, 17–44.
- Ramsbottom, W H C. 1978.Namurian. 178–180 in The geology of the Lake District. Moseley, F (editor).Occasional Publication of the Yorkshire Geological Society, No. 3.