The BGS Lexicon of Named Rock Units — Result Details

Derbyhaven Formation

Computer Code: DBH Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Arundian Substage (CJ)
Lithological Description: Limestone, with interbedded subordinate claystone and siltstone. Limestones vary from packstone to wackestone and grainstone. They are typically grey, bioclastic including crinoids and corals and bioturbated. Sedimentary structures vary but include cross-bedding, wave ripples and hummocky cross-bedding. Claystones and siltstones are grey, bioclastic, forming thin, discontinuous beds. Interpreted to represent a carbonate ramp facies.
Definition of Lower Boundary: The base of the formation is taken at the base of the Turkeyland Member,which is poorly defined. It rests directly on conglomerate of the Langness Conglomerate Formation on the foreshore at Derbyhaven [SC 2820 6607], although outcrops are discontinuous and poorly exposed. It was formerly exposed at the now infilled Turkeyland Quarry [SC 2950 6940], where it rested directly on conglomerates of the Langness Conglomerate Formation.
Definition of Upper Boundary: The top of the formation is poorly defined. It is overlain by the Knockrushen Formation, with the boundary taken as immediately above a byozoan bed which is exposed to the north-east of the airport light gantry at Ronaldsway, at Port St Mary and Ballasalla (Dickson et al.1987). No grid references are quoted in the Dickson et al. (1987) papers for these localities.
Thickness: Greater than 90m.
Geographical Limits: Southern part of the Isle of Man, in the Castletown area, from Ballasalla [SC 2857 7017] to Derbyhaven [SC 2798 6754].
Parent Unit: Great Scar Limestone Group (GSCL)
Previous Name(s): Lower Castletown Limestones (-2743)
Derbyhaven Formation (DBH)
Ballasalla Formation (-845)
Lower Grey And Dark Limestones Of Lewis (-846)
Derbyhaven Beds (-3349)
Alternative Name(s): none recorded or not applicable
Partial Type Section  Foreshore exposures from Derbyhaven to Creg Inneen Thalleyr. Discontinuous exposures through Turkeyland Member. Dickson et al.(1987) 
Reference Section  Foreshore exposures east and north-east of Ronaldsway airport. Mainly argillaceous limestone with abundant shale intercalations. Dickson et al.(1987) 
Dickson, J A D, Ford, T D and Swift, A. 1987. The stratigraphy of the Carboniferous rocks around Castletown, Isle of Man. Proceedings of the Yorkshire Geological Society, Vol.46, 203-229. 
Lamplugh G W. 1903. The geology of the Isle of Man. Memoir Geological Survey of Great Britain 
Lewis, H P. 1930. The Avonian succession in the south of the Isle of Man. Quarterly Journal of the Geological Society of London, 86, 234-290. 
Chadwick, R A, Jackson, D I, Barnes, R P, Kimbell, G S, Johnson, H, Chiverell, R C, Thomas, G S P, Jones, N S, Riley, N J, Pickett, E A, Young, B, Holliday, D W, Ball, D F, Molyneux, S G, Long, D, Power, G M and Roberts, D H. 2001. Geology of the Isle of Man and its offshore area. British Geological Survey Research Report, RR/01/06. 
Bristow, C R, Freshney, E C and Penn, I E. 1991. Geology of the country around Bournemouth. Memoir for 1:50 000 geological sheet 329 (England and Wales). HMSO, London. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: