The BGS Lexicon of Named Rock Units — Result Details

Pickwell Down Sandstones Formation

Computer Code: PDS Preferred Map Code: notEntered
Status Code: Full
Age range: Famennian Age (DA) — Famennian Age (DA)
Lithological Description: Purple, red-brown and greenish-grey sandstones, commonly current bedded and generally fine to medium grained. Subordinate red and grey cleaved mudstones predominate at the base and top of the formation: fish fragments have been found towards the base of the formation where it is exposed on the coast; plant fragments have been found inland. Base of the formation is marked by a sporadic but persistent band of tuff (Bittadon Felsite), up to 8 m thick, the type locality of which is alongside the driveway to Hewish Barton [SS 5502 4086] which is massive, slighty foliated, fine- to-coarse grained with iron oxide spots and broken feldspar laths.
Definition of Lower Boundary: Overlie Morte Slates; the base of the formation is marked by a persistant keratophyric tuff band up to 8 m thick which is massive and strong where fresh, and forms a distinct topographic feature. The lower boundary is distinguished by a change from the grey cleaved mudstones of the Morte Slates to the massive, slightly foliated fine- to coarse-grained tuff.
Definition of Upper Boundary: At Napps Cliff [SS 4460 4072] the contact is stratigraphic and gradational over approximately 9 m of strata; progressively higher sandstones become thinner and finer-grained and give way to predominant siltstones, silty slates and slates in the Upcott Beds.
Thickness: Approx. 1200 m.
Geographical Limits: South-west England: from Morte Bay [SS 4545 4175] on the north Devon coast in a west-south-west trending outcrop of variable width as far east as Langley Marsh [ST 0718 2848].
Parent Unit: Not Applicable (-)
Previous Name(s): Pickwell Down Sandstones [Obsolete Code: Use PDS] (PWS)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Bittadon Felsite - quarry alongside the driveway to Hewish Barton. Salter, 1863. 
Type Area  Pickwell Down. Edmonds et al., 1985. 
Reference(s):
Edmonds, E A, Williams, B J and Taylor, R T. 1979. Geology of Bideford and Lundy Island. Memoir of the Geological Survey of Great Britain, Sheets 292 with 275, 276, 291, and part of 308 (England and Wales). 
Etheridge, R. 1867. On the physical structure of west Somerset and north Devon and on the palaeontological value of the Devonian fossils. Quarterly Journal of the Geological Society of London, Vol. 23, p.568-698. 
Salter, J W. 1863. On the Upper Old Red Sandstone and Upper Devonian Rocks. Quarterly Journal of the Geological Society, Vol. 19, p 479. 
Bonney, T G. 1878. Note on the felsite of Bittadon, north Devon. Geol. Mag., Vol. 15, pp 207-209. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable