The BGS Lexicon of Named Rock Units — Result Details

Stotfield Calcrete Formation

Computer Code: STCA Preferred Map Code: notEntered
Status Code: Full
Age range: Rhaetian Age (TR) — Rhaetian Age (TR)
Lithological Description: The Stotfield Calcrete Formation is composed mainly of white, pale grey, or occasionally pale brown limestone, which is microcrystalline or cryptocrystalline, and massive or platy. White, pale brown, or bluish grey chert is commonly also encountered in cuttings, and forms the infill of stylolites and veins in well 12/26-1. A few thin beds of pale grey or yellowish orange mudstone are intercalated within the limestones of blocks 12/21 and 12/27.
Definition of Lower Boundary: The Stotfield Calcrete Formation rests on Triassic sandstones, siltstones and mudstones of the Lossiehead Formation. Its base can be sharp or transitional, but is generally marked by a downward increase in gamma-ray values and a decrease in both velocity and resistivity. The equivalent boundary at Stotfield is transitional, with highly silicified sandstones grading upwards into an increasingly carbonate-rich rock containing pockets of unaltered sandstone (Naylor et al., 1989).
Definition of Upper Boundary: The top of the Stotfield Calcrete Formation is defined by a sharp downward change from alluvial red-beds (Golspie Formation) to limestone, and is marked in all sections by a downhole increase in velocity and resistivity.
Thickness: Up to 25 m thick in southwestern Quadrant 12, and more than 10 m thick in most adjacent parts of Quadrants 11 and 18, the formation thins to less than 6 m in the northeast. Equivalent sediments are less than 10 m thick in quarries near Stotfield (Peacock et al., 1968; Naylor et al., 1989).
Geographical Limits: The Stotfield Calcrete Formation and equivalent sediments in coastal outcrops extend across an area of about 4000 kmr of the Inner Moray Firth.
Parent Unit: Heron Group (HERO)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 12/26- 1: 1295.5-1308 m (4250-4291 ft) below KB (Cameron, 1993). 
Reference Section  North Sea well 11/30- 6: 1639-1652 m (5377-5419 ft) (Cameron, 1993). 
Reference Section  North Sea well 18/05a- 1: 1386-1398 m (4547-4586 ft) (Cameron, 1993). 
Reference(s):
Frostick, L, Reid, I, Jarvis, J and Eardley, H. 1988. Triassic sediments of the Inner Moray Firth, Scotland: early rift deposits. Journal of the Geological Society (London), Vol. 145, 235-248. 
Naylor, H, Turner, P, Vaughan, D J and Fallick, A E. 1989. The Cherty Rock, Elgin: A petrographic and isotopic study of a Permo-Triassic calcrete. Geological journal, Vol. 24, p. 205 - 221. 
Peacock, J D, Berridge, N G, Harris, A L, May, F. 1968. The geology of the Elgin District. Memoir of the Geological Survey of Scotland. Sheets 86 and 96 (Scotland). (Edinburgh: HMSO). 
Roberts, A M, Badley, M E, Price, J D, and Huck, I W. 1990. The structural history of a transtensional basin: Inner Moray Firth, NE Scotland. Journal of the Geological Society, London 147, 87-103. 
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable