The BGS Lexicon of Named Rock Units — Result Details

Balintore Formation

Computer Code: BALR Preferred Map Code: notEntered
Status Code: Full
Age range: Callovian Age (JC) — Oxfordian Age (JO)
Lithological Description: The Balintore Formation is dominated by moderately to richly fossiliferous sandstone, sand and sandy siltstone (variously calcareous or glauconitic), and mudstone, bituminous in parts. The formation is about 68 m thick at Balintore. The lowermost unit the Cadh'-an-Righ Shale Member, is 4.2 m of sparsely fossiliferous bituminous fissile mudstone, with interbedded thin glauconitic siltstone, and includes the 0.5 m thick bioturbated sandstone of the Brora Roof Bed at the base. The overlying Shandwick Clay Member is about 28 m thick: the lower 24 m are bioturbated grey-green clay with layers of limestone nodules at the base, and the uppermost 4.1 m comprises sandy siltstone. Above is the Shandwick Siltstone Member - 12.1 m of fossiliferous siltstone, with alternating beds that are more or less calcareous. Overlying it is the Port-an-Righ Ironstone Member (Buckman, S S, 1923) comprising 2.2 m of muddy, glauconitic sand with interbedded bands of red-weathering nodular glauconitic limestone, all rich in ammonites. The overlying Port-an-Righ Siltstone Member is 21.7 m thick, and largely consists of relatively sparsely fossiliferous bituminous coarse silt. This unit comprises thin (0.1 to 1.8 m) rhythmic units that coarsen upwards from carbonaceous shale or silt, to fine-grained muddy sandstone. The uppermost bed is 5.7 m of fine-grained muddy sandstone. There is strong evidence that there are fine-grained beds above the Port-an-Righ Siltstone Member that are not exposed onshore (Sykes, 1975, p.62). The Balintore Formation yields marine biota and marine microfosils throughout. The macrofauna is dominated by ammonites and bivalves, with belemnites, brachiopods and gastropods, and dinoflagellate cysts are generally abundant and diverse (Riding, 2005).
Definition of Lower Boundary: The lower boundary is a sharp non-sequential change up from the Brora Coal (Bed) of the Brora Coal Formation to bioturbated medium-grained sandstone of the Brora Roof Bed of the Cadh'-an-Righ Shale Member (MacLennan and Trewin, 1989).
Definition of Upper Boundary: The upper boundary of the Balintore Formation at Balintore is not exposed. The Port-an-Righ Siltstone Member is the youngest unit seen, and the uppermost beds dip off into deep water at low tide. Limestone nodules with Early Oxfordian ammonites are found on the foreshore, and Sykes (1975, p.62) inferred the probable presence of a relatively soft, claystone-dominated succession. It may be present in offshore boreholes (MacLennan and Trewin, 1989).
Thickness: At the type section at Balintore, the thickness of this formation is about 68 m although the top is unseen. At Bow Buoy Skerry, about 30 m of strata are exposed, base and top unseen.
Geographical Limits: The Balintore Formation is confined to the onshore Moray Firth area, north-east Scotland forming a narrow strip along the coast at Port-an-Righ, Balintore, and an outcrop exposed only at low tide near Eathie. Both are bounded to the west by a fault parallel to the Great Glen Fault Zone, which lies close offshore to the east. It correlates offshore in the Inner Moray Firth with the lower part of the Beatrice Formation of the Fladen Group (Richards et al., 1993).
Parent Unit: Sutherland Group (SUTH)
Previous Name(s): Brora Arenaceous Formation (BRARE)
Brora Argillaceous Formation (BRARG)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  The type section of the Balintore Formation is entirely on the foreshore at Cadh'-an-Righ and Port-an-Righ [NH 849 723 to 853 733]. This exposes the formation continuously from the base upwards to the uppermost beds seen before they dip into the sea (Cox and Sumbler, 2002, pp.376-379; Sykes, 1975; Wright, J K and Cox, 2001, pp.188-190). 
Reference Section  Bow Buoy Skerry [NH 7696 6214], near Eathie, Ros and Cromarty. Exposes, only at low tide, about 30 m of shelly bioturbated very fine-grained sandstone beds, dipping at 70˚ to south-east, base and top of formation not exposed (Sykes, 1975). 
Type Area  Balintore area, Ross and Cromarty, Scotland. 
Reference(s):
Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G. Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham] 
Barron, A J M, Lott, G K, and Riding, J B. 2012. Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report RR/11/06. 
Sykes, R M. 1975. The stratigraphy of the Callovian and Oxfordian stages (Middle-Upper Jurassic) in northern Scotland. Scottish Journal of Geology, Vol.11, 51-78. 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Maclennan, A M, and Trewin, N H. 1989. Palaeoenvironments of the late Bathonian-mid Callovian in the Inner Moray Firth. Northwest European Micropalaeontology and Palynology. British Micropalaeontological Society Series. Batten, D J, and Keen, M C (editors). (Chichester: Ellis Horwood Limited.) 
Buckman, S S. 1923. Type ammonites Volume 4. (London.) 
Riding, J B. 2005. Middle and Upper Jurassic (Callovian to Kimmeridgian) palynology of the onshore Moray Firth Basin, northeast Scotland. Palynology, Vol. 29, 87-142. 
Wright, J K, and Cox, B M. 2001. British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series. No. 21. (Peterborough: Joint Nature Conservation Committee/Chapman and Hall.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable