The BGS Lexicon of Named Rock Units — Result Details

Pibroch Sandstone Member

Computer Code: PIBR Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: The Pibroch Sandstone Member comprises mainly fine- to coarse-grained sandstones with subordinate dark grey, marine mudstones. It has been divided into five lithofacies: 1) Bioturbated, fossiliferous mudstones with thin (1-2 m thick), poorly sorted, glauconitic, very fine-grained sandstones at their base. 2) Bioturbated, silty, fine-grained sandstones with broken bivalves and belemnites. 3) Well-sorted, massive to cross-bedded, bioturbated, medium-grained sandstones with sporadic shelly debris. 4) Well sorted, massive to planar bedded, coarse grained sandstones. 5) Upward fining, cross-bedded, very coarse- to coarse-grained sandstones. Thin coals formed locally. The lithofacies are arranged in a stacked succession of large scale, upward coarsening cycles, about 20 m thick.
Definition of Lower Boundary: The base is placed at a down-section transition from sandstone to mudstone (Heather Formation) and a down-section increase in gamma-ray values. Locally the Pentland Formation underlies the Pibroch Sandstone Member and here it rests on coal or coal-bearing mudstones of the Stroma Member or volcanics of the Rattray Volcanics Member.
Definition of Upper Boundary: The top is defined by the base of the overlying, widespread, marine mudstone, informally named the 'I Shale' (of Maher, 1981). This down-section change from mudstone to sandstone usually coincides with a marked by a decrease in gamma-ray values and increased velocity.
Thickness: Up to 150 m.
Geographical Limits: Central part of the Witch Ground Basin, east of the Halibut Horst (Quadrants 14 and 15).
Parent Unit: Piper Formation (PIPR)
Previous Name(s): J Sand (-5168)
Main Piper Sandstone (-5169)
Pibroch Member (-5170)
Piper Formation Lower Sand Member (-5171)
Scott Member (Sgiath Formation) (-5172)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea Well 15/21a-11 between depths 2399 and 2472.5 m below KB (Richards et al., 1993). 
Reference Section  North Sea Well 15/16-1 between depths 3080-3093.5 m (Richards et al., 1993). 
Reference Section  North Sea Well 15/21-3 between depths 2474.5-2528.5 m (Richards et al., 1993). 
Reference(s):
O'Driscoll, D, Hindle, A D and Long, D C. 1990. The structural controls on Upper Jurassic and Lower Cretaceous reservoir sandstones in the Witch Ground Graben, UK North Sea. In: Hardman, R F P and Brooks, J (eds.) Tectonic events responsible for Britain's oil and gas reserves. Special Publication of the Geological Society, London, No.55, 191-205. 
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] 
Harker, S D, Mantel, K A, Morton, D J and Riley, L A. 1993. The stratigraphy of Oxfordian-Kimmeridgian (Late Jurassic) reservoir sandstones in the Witch Ground Graben, UK North Sea. American Association of Petroleum Geologists Bulletin, 77, 1693-1709. 
Boldly, S A R and Brearly, S. 1990. Timing, nature and sedimentary result of Jurassic tectonism in the Outer Moray Firth. In: Hardman, R F P and Brooks, J (eds.) Tectonic events responsible for Britain's oil and gas reserves. Special Publication of the Geological Society, London, No.55, 259-279. 
Coward, R N, Clark, N M and Pinnock, S J. 1991. The Tartan Field, Block 15/16, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields, 25 years commemorative volume. Memoir of the Geological Society, London, 14, 377-384. 
Maher, C E. 1981. The Piper Oil Field. In: Illing, L V and Hobson, G D (eds.) Petroleum Geology of the continental shelf of North West Europe, 358-370. [Heyden & Son, London] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable