The BGS Lexicon of Named Rock Units — Result Details

Dark Slade Member

Computer Code: DAR Preferred Map Code: Dar
Status Code: Full
Age range: Asturian Substage (CAS) — Asturian Substage (CAS)
Lithological Description: Mudstone with subordinate sublitharenite sandstones and thin beds of Spirorbis limestone. Colour grey with mottled grey/brown palaeosols (but may be reddened). Distinctive geophysical log character, with gamma peaks.
Definition of Lower Boundary: At base of mudstone-dominated succession resting on litharenites of lower Halesowen Formation; or at change of gamma log character.
Definition of Upper Boundary: At base of overlying Salop Formation. In places where Member is grey there is a change to orange-red colours. Boundary also marked by a change of gamma log character.
Thickness: 40 to 90m; 60.5m in type section.
Geographical Limits: Staffordshire, Shropshire, Warwickshire.
Parent Unit: Halesowen Formation (HA)
Previous Name(s): Palustrine Unit (-2136)
Alternative Name(s): none recorded or not applicable
Type Section  Dark Slade Borehole; base at 241.8 m., top at 181.3 m. (Besly & Cleal, 1997, fig. 10) (SJ 91 NE/16). 
Reference Section  Radwood Borehole, base at 284.9 m., top at 204.3 m. (Besly & Cleal, 1997, fig. 6) (SJ 74 SE/28). 
Besly, B M and Cleal, C J, 1997. Upper Carboniferous stratigraphy of the West Midlands (UK) revised in the light of borehole geophysical logs and detrital compositional suites. Geological Journal 32, 85 - 118. 
Powell, J H, Chisholm, JI, Bridge, D M, Rees, J G, Glover, B W and Besly, B M. 1999. Stratigraphical framework for Westphalian to Early Permian red-bed successions of the Pennine Basin. British Geological Survey Technical Report WA/99/10. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable