| Computer Code: |
FRAS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Cisuralian Epoch (PLC)
— Lopingian Epoch (PUL) |
| Lithological Description: |
The Fraserburgh Formation generally consists of mudstone and siltstone with sporadic thin stringers of sandstone. Anhydrite nodules and patches of sandy dolomite have also been noted in a number of wells. The mudstones are mainly reddish brown or dark brown, but are occasionally grey; they are anhydritic and slightly calcareous. The siltstones are reddish brown, micaceous and slightly dolomitic. The sandstone stringers are argillaceous and anhydritic; they display wavy bedding and are mostly 2-3 cm thick. In marginal areas, the formation also includes a few thicker beds of very fine, fine or, occasionally, coarse grained, moderately sorted sandstone (e.g. 20/10a-3). Comparable sandstones, up to 13 m thick, occur at the top of the section in parts of Quadrant 21 (e.g. 21/11-1). |
| Definition of Lower Boundary: |
The Fraserburgh Formation rests unconformably on early Carboniferous coal measures (Firth Coal Formation) or fluviodeltaic sediments (Tayport Formation), or on Devonian sandstones in almost all wells, with the boundary being marked by a sharp lithological transition and wireline-log break. |
| Definition of Upper Boundary: |
The top of the Fraserburgh Formation is defined by a downward change from highly radioactive marine mudstones of the Kupferschiefer Formation to mudstone or siltstone, or locally to thin sandstone, and is always marked by a sharp downward decrease in gamma-ray values. |
| Thickness: |
The Fraserburgh Formation is typically between 60 and 175 m thick, but is 230 m thick in well 20/12-3. Deegan and Scull (1977) suggested that the sabkha mudstones might thin to the northwest, but more recent well data have shown that they thin towards the centre of the desert sabkha. |
| Geographical Limits: |
The Fraserburgh Formation is present over much of Quadrant 21 and part of Quadrant 20. Its western and eastern limits are poorly constrained by well data. The formation does not extend north of 58°N; southwards, it passes laterally into the Auk Formation (Deegan and Scull, 1977). |
| 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 21/11- 1 (Deegan and Scull, 1977, p.5, fig.6): 3165-3294.5 m (10384-10809 ft) below KB (Cameron, 1993). |
| Reference Section |
North Sea well 20/10a- 3: 3445-3515 m (11303-11533 ft) (Cameron, 1993). |
| Reference Section |
North Sea well 20/12- 3: 1195.5-1258 m (3922-4128 ft) and 1322-1489 m (4337-4886 ft) (Cameron, 1993). |
| Reference Section |
North Sea well 28/05- 1: 2812-2834 m (9226-9298 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. |
| Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. |
| Glennie, K W. 1990. Lower Permian - Rotliegend. In: Glennie, K W (ed.) Introduction to the Petroleum Geology of the North Sea, Blackwell Scientific Publications, p. 120 - 152. |
| 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.) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
