| Computer Code: |
INVO |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Cisuralian Epoch (PLC)
— Cisuralian Epoch (PLC) |
| Lithological Description: |
Most of the Inge Volcanics Formation is composed of red and purple weathered tuffs and purple, reddish grey, and occasionally dark green basalts; the latter may include extrusive and intrusive rocks. The tuffs are hard and cindery, and they contain feldspar laths and occasional glassy shards. Grains of chlorite locally give the tuffs a speckled appearance. Well 31/26-3 terminated in 79 m of amygdaloidal basaltic lavas, but individual basalt units are less than 20 m thick in other wells. The basalts contain pyroxene phenocrysts and possible serpentine pseudomorphs of olivine in a feldspar pyroxene groundmass. |
| Definition of Lower Boundary: |
Only three wells have drilled through the base of the Inge Volcanics Formation in the UK sector. Secondarily reddened sandstones and mudstones of possible Carboniferous age have been recorded beneath the volcanics in wells 39/1-1 and 39/2-1, and the Inge Volcanics Formation rests unconformably on Devonian strata in well 30/25b-3. The base of the formation is a sharp wireline-log break in all three wells. |
| Definition of Upper Boundary: |
Where Lower Permian sandstones and mudstones of the Auk Formation rest on the basal Permian section in Quadrant 31, the top of the Inge Volcanics Formation is defined by the uppermost occurrence of volcanics. The boundary is marked by a conspicuous wireline-log break in most wells, as in 31/26-1. Locally, Upper Permian sediments of the Zechstein Group overstep the Auk Formation to rest on the volcanics, and in such areas the boundary is clearly defined by contrasts in lithology and wireline-log character (e.g. 39/2-1). |
| Thickness: |
Well 31/26-1 has encountered the thickest section of Lower Permian volcanics so far (349 m) but terminated above their base. The Inge Volcanics Formation thins westwards and southwards from there, being only 51 m thick in well 30/25b-3 and 205 m thick in well 39/2-1. Records from well 211/11b-4 indicate that Early Permian volcanics are at least 77 m thick in parts of the East Shetland Basin. |
| Geographical Limits: |
The Inge Volcanics Formation is largely restricted to southeastern Quadrant 30, Quadrant 31 and northern Quadrant 39 in the UK sector. Possibly contemporary volcanics have been recorded in East Shetland Basin well 211/11b-4, but the outlying occurrences of intrusive basalt at the base of the Permian in Argyll well 30/24-10 and of tuff within Lower Permian sands in Outer Moray Firth well 14/29a-2 are included within the Auk Formation. |
| 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 31/26- 1: 2783-3131.5 m (9130-10274 ft) below KB (Cameron 1993). |
| Reference Section |
North Sea well 39/02- 1: 2809-3014 m (9216-9888 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. |
| 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. |
| Dixon, J E, Fitton, J G, and Frost, R T C. 1981. The tectonic significance of post-Carboniferous igneous activity in the North Sea Basin. In: Illing, L V, and Hobson, G D (eds.) Petroleum geology of the continental shelf of Northwest Europe, 121-140. Heyden and Son, London. |
| Sørensen, S, and Martinsen, B B. 1987. A paleogeographic reconstruction of the Rotliegendes deposits in the Northeastern Permian Basin. In: Brooks, J, and Glennie, K W (eds.) Petroleum geology of North West Europe, 497-508. Graham and Trotman, London. |
| 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 |
