The BGS Lexicon of Named Rock Units — Result Details

Findhorn Formation

Computer Code: FIND Preferred Map Code: notEntered
Status Code: Full
Age range: Cisuralian Epoch (PLC) — Lopingian Epoch (PUL)
Lithological Description: The Findhorn Formation in Quadrant 12 is composed largely of very fine to fine grained, occasionally medium or coarse grained, argillaceous, locally micaceous, sandstones. The sandstones are moderately or poorly sorted, and reddish brown or, less commonly, pale grey in colour. They are mainly cemented by anhydrite or kaolinite and are mostly non-calcareous. Subsidiary beds, up to 5 m thick, of darker reddish brown or greenish grey mudstone or siltstone are present. Calcareous sandstones and thin beds of limestone have been noted in several wells. In the south of the quadrant, in particular, the gamma-ray response is irregular, suggesting an alternation of thinly bedded clean sandstones, argillaceous sandstones and mudstones.
Definition of Lower Boundary: Red, unfossiliferous clastic sediments of the Findhorn Formation rest unconformably on reddened, sparsely fossiliferous Devonian clastic sediments across most of the Inner Moray Firth (e.g. on the Lower Devonian Struie Formation in 12/27-1, and on the Middle Devonian Strath Rory Formation in 12/27-2). Locally, they rest on metamorphic or granitic basement, or, as in well 12/23-1, on Upper Devonian to Lower Carboniferous strata (Buchan Formation).
Definition of Upper Boundary: The Findhorn Formation is conformably overlain by basal Upper Permian mudstones of the Kupferschiefer Formation in almost all wells, and the top of the formation is thus defined by a sharp downward change from mudstones to sandstones, marked by a sharp decrease in gamma-ray values. In the few wells in which the Kupferschiefer is absent, the Findhorn Formation is overlain by Upper Permian carbonates or, where the Upper Permian has been removed, by Upper Jurassic or Cretaceous rocks.
Thickness: The Findhorn Formation is more than 500 m thick in most of Quadrant 12; it has a maximum drilled thickness of 842 m in well 12/29-2. The formation is appreciably thinner adjacent to the Wick Fault and in central Quadrant 13, where it is about 300 m or less in thickness.
Geographical Limits: Well penetrations of the Findhorn Formation are confined to the Inner Moray Firth Basin, though an outlier of equivalent sediments may occur farther north in the East Orkney Basin (Andrews et al., 1990). The formation abuts northwards against the Wick Fault and westwards against the Helmsdale Fault or Great Glen Fault. It encroaches close to the Buchan coastline to the south, but, being of early Permian age, is older than the lithologically similar, mainly Triassic, Hopeman Sandstone Formation of onshore sections (Andrews et al., 1990). The formation pinches out eastwards and is absent across the Halibut Horst and South Halibut Basin.
Parent Unit: Rotliegend Group (RLG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 12/23- 1: 1509-1961 m (4950-6435 ft) below KB. The well operators and Andrews et al. (1990) took the base of the Lower Permian to be at 2201 m (7222ft). However, the section below 1961 m (6435 ft) displays markedly higher velocity than the overlying section, and is here assigned to the Upper Old Red Group (Cameron, 1993). 
Reference Section  North Sea well 13/18- 1: 2159-2440 m (7084-8007 ft) (Cameron, 1993). 
Reference(s):
Cameron, T D J. 1993. 4. Triassic, Permian and pre-Permian of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. 
Andrews, I J, Long, D, Richards, P C, Thomson, A R, Brown, S, Chesher, J A, and McCormac, M. 1990. The geology of the Moray Firth. (London: British Geological Survey.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable