| Computer Code: |
LMS |
Preferred Map Code: |
LmS |
| Status Code: |
Full |
| Age range: |
Cisuralian Epoch (PLC)
— Lopingian Epoch (PUL) |
| Lithological Description: |
The Leman Sandstone Formation is characterized by red-brown, pink, and occasionally grey, sandstones with interbedded conglomerates, breccias and red mudstones. The sandstones are typically very fine to medium grained, although some coarse grained sandstones are also present. They are generally clean, moderately to well-sorted, and non-micaceous with common frosted grains. Locally, slightly argillaceous, micaceous, poorly sorted, commonly upward fining sandstones with sporadic pebbles and rip-up clasts of mudstone are prevalent. Mineralogically, the sandstones are moderately mature quartz arenites with up to about 10 per cent feldspar grains. Dolomitic cement is common in the argillaceous sandstones. |
| Definition of Lower Boundary: |
The lower boundary of the Leman Sandstone Formation with the Carboniferous is everywhere an unconformity surface. The lower boundary with the Conybeare Group is generally marked by a downward change from red-brown sandstones and local fluvial conglomerates (e.g. 53/2-4), to grey mudstones with interbedded sandstones and coals. It is marked on wireline logs by a significant downward increase in gamma-ray values. However, where the Leman Sandstone overlies reddish brown to purple mudstones and reddish brown or occasionally white sandstones of the Ketch Member (Schooner Formation), the boundary is normally marked by a sharp downward decrease in velocity (e.g. 49/1-3, p.23 in Cameron, 1993). Locally, the Leman Sandstone Formation overlies interbedded grey, white and brown sandstones and grey, carbonaceous mudstones of the Millstone Grit Formation (Cameron, 1993).
Where the Leman Sandstone Formation is split by mudstones of the Silverpit Formation, the base of the upper leaf (Upper Leman Sandstone) is marked by a downward change from sandstone to red-brown mudstone and this coincides with a downward increase in gamma-ray values. |
| Definition of Upper Boundary: |
The boundary between the Leman Sandstone Formation and the overlying Kupferschiefer Formation is marked by a sharp downward passage from dark coloured mudstone to grey and red-brown sandstone, corresponding to a marked downward decrease in gamma-ray values and an increase in velocity.
Where the Leman Sandstone Formation is split by mudstones of the Silverpit Formation, the upper boundary of the lower leaf (Lower Leman Sandstone) is typically marked by a downward change from red-brown mudstones to redbrown sandstones. This is associated with a downward decrease in gamma-ray values. Locally, the downward passage from the Silverpit Formation to the Leman Sandstone Formation is gradational (e.g. 48/6-25). |
| Thickness: |
The formation is most thickly developed in the Sole Pit Trough, where it reaches about 290 m thick. Thinner successions are developed on the Inde and South Hewett shelves and on the Cleaver Bank and Winterton highs. |
| Geographical Limits: |
The Leman Sandstone Formation extends throughout the Sole Pit Basin, South Hewett Shelf, Inde Shelf, and across the Cleaver Bank and Winterton highs to the boundary with the Dutch sector. It interdigitates with, and passes northwards into the laterally equivalent Silverpit Formation in the Silverpit Basin. It thins to a feather edge near the English coast. |
| 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 49/26- 4 (Rhys, 1974, table 2, fig. 2): 2013-2289 m (6604-7510 ft) below KB (Johnson et al., 1994). |
| Reference Section |
North Sea well 44/21- 1: 3863-3864.5 m (12674-12678 ft) and 4185-4202 m (13730-13786ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 48/06- 25: 2831.5-2848.5 m (9290-9345 ft) and 2905-3021 m (9531-9911 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 53/02- 4: 1834.5-2083 m (6018-6834 ft) (Johnson et al., 1994). |
| Reference(s): |
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. |
| Cameron, T D J. 1993. 5. Carboniferous and Devonian of the Southern 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. 1972. Permian Rotliegendes of northwest Europe interpreted in light of modern desert sedimentation studies. AAPG Bulletin 56, 1048-1071. |
| 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. |
| NAM and RGD (Nederlandse Ardolie Maatschappij and Rijks Geologische Dienst) 1980. Stratigraphic nomenclature of the Netherlands. Transactions of the Royal Dutch Geological and Mining Society of Delft. |
| Rhys, G H. 1974. A proposed standard lithostratigraphic nomenclature for the southern North Sea and an outline structural nomenclature for the whole of the (UK) North Sea. Report of the Institute of Geological Sciences, 74/8. |
| Butler, J B. 1975. The West Sole gas-field. 213-221 in Petroleum geology and the continental shelf of North-West Europe. Woodland, A W (editor). (London: Applied Science Publishers.) |
| France, D S. 1975. The geology of the Indefatigable Gas-Field. In: Woodland, A W (ed.) Petroleum geology and the continental shelf of North-West Europe, 233-239. Applied Science Publishers, London. |
| Van Veen, F R. 1975. Geology of the Leman Gas-Field. In: Woodland, A W (ed.) Petroleum geology and the continental shelf of North-West Europe, 223-231. Applied Science Publishers, London. |
| Johnson, H, Warrington, G and Stoker, S J. 1994. 6. Permian and Triassic of the Southern 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: |
|
E162
|
