Danny Bridge Limestone Formation
Danny Bridge Limestone Formation (DBL), Carboniferous, Northern England Province
Danny Bridge Limestone Formation is part of the Great Scar Limestone Group
Name
The name is derived from Danny Bridge (SD 6982 9128), Garsdale, Yorkshire (see Dunham and Wilson, 1985, and references therein[1]). The formation was proposed by Burgess (1986[2]).
Lithology
The Danny Bridge Limestone Formation consists of pale to mid grey biosparites and biopelsparites (mainly wackestone, with packstone and minor grainstone), and subordinate mudstone in 10 regularly spaced interbeds. Palaeokarst surfaces overlain by bentonitic clays, palaeosols and calcareous laminated crusts are common and the formation displays a characteristically stepped landscape.
Genetic interpretation
Shallow marine carbonates (emergent at times).
Stratotype
The type section of the formation is the River Clough at Garsdale (SD 7000 9118 to 6977 9128), which consists mainly of marine limestone (biomicrite, biomicrosparite, biosparite) and mudstone (see Burgess, 1986, pp. 13–14[2]). Reference sections include the Beckermonds Scar Borehole (BGS Registration Number SD88SE/1) (SD 8636 8016) from about 8.0 to 101 m depth with mainly pale grey (and subordinate mid grey) limestone, thin mudstone or siltstone beds, and a section of mineralised flats (see Wilson and Cornwell, 1982, pp. 61–63[3]; Dunham and Wilson, 1985, fig..5, col. 5), and the BGS Raydale Borehole (BGS Registration Number SD98SW/1) (SD 9626 8474) from about 5 to 103 m depth. Dunham and Wilson (1985, fig..5, col..7[1]) summarised the Raydale Borehole and surface exposures as a largely complete sequence about 127.m thick with mainly pale grey limestone and thin mudstone or siltstone beds.=== Lower and upper boundaries === The base of the formation is conformable on the dark grey limestone of the Garsdale Limestone Formation (Figure 9, Column 17).
The cross-bedded, regressive sandstones of the Wintertarn Sandstone Member (WTRS), marking the base of the Tyne Limestone Formation, Yoredale Group, overlie the top of the Danny Bridge Limestone Formation (Figure.15, Column 3).
Thickness
The formation is 102–168 m thick, the greatest thickness being on the southern margin of the Askrigg Block (see Dunham and Wilson, 1985[1]).
Distribution and regional correlation
Askrigg Block, Wensleydale and Wharfedale. The formation is the direct equivalent of the Knipe Scar and Urswick limestone formations of the Stainmore Trough and south Cumbria respectively.
Age and biostratigraphical characterisation
Late Asbian. Amongst the general shelly debris, fossils include Davidsonina septosa and typically, Siphonodendron martini. The formation also yields a diagnostic late Asbian assemblage of foraminifers (see Dunham and Wilson, 1985, p. 22[1]).
References
- ↑ 1.0 1.1 1.2 1.3 Dunham, K C, and Wilson, A A.1985.Geology of the Northern Pennine Orefield: Volume 2, Stainmore to Craven.Economic Memoir of the British Geological Survey, Sheets 40, 41 and 50, parts 31, 32, 51, 60 and 61(England and Wales).
- ↑ 2.0 2.1 Burgess, I C.1986.Lower Carboniferous sections in the Sedbergh district, Cumbria.Transactions of the Leeds Geological Association, Vol. 11, 1–23.
- ↑ Wilson, A A, and Cornwell, J D.1982.The Institute of Geological Sciences Borehole at Beckermonds Scar, North Yorkshire.Proceedings of the Yorkshire Geological Society,Vol. 44, 59–88.