| Computer Code: |
KPAN |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Norian Age (TN)
— Norian Age (TN) |
| Lithological Description: |
The Keuper Anhydrite Member comprises red, red-brown and grey-green mudstones with numerous beds of white to grey, transparent, crystalline anhydrite and some interbedded dolomite and siltstone. The member typically shows lower gamma-ray values and higher velocities than the overlying and underlying Triton Formation mudstones. The gamma-ray and velocity logs also display greater ranges in value and are more spikey in character. |
| Definition of Lower Boundary: |
The base of the Keuper Anhydrite Member is placed at the base of the main concentration of anhydrite interbeds in the Triton Formation. It is characterized by a marked downhole increase in gamma-ray values and a decrease in velocity. |
| Definition of Upper Boundary: |
The top of the Keuper Anhydrite Member is defined by a downward change from red-brown mudstones with some grey-green interbeds to a unit of similar mudstones with numerous interbeds of anhydrite and some thin dolomites and siltstones. The boundary corresponds to a downward decrease in gamma-ray values, compared with the overlying mudstones; an increase in velocity may be apparent at the same level. |
| Thickness: |
The member varies in thickness from about 30 m, to the north of the Sole Pit Basin, to over 115 m in that basin. |
| Geographical Limits: |
The Keuper Anhydrite Member is widely recognized within the UK sector where its extent is only slightly less than that of the Triton Formation. |
| Parent Unit: |
Triton Formation (TTHY)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 49/21- 2 (Rhys, 1974): 697-808.5 m (2287-2653 ft) below KB (metric conversion revised). The upper boundary of the Triton Formation, close above the top of the Keuper Anhydrite Member, is poorly characterized on the velocity log of this well; the characters of this part of the sequence are better represented in the reference sections. |
| Reference Section |
North Sea well 47/05a- 3: 1158.5-1235 m (3800-405l ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 49/21- 5: 594-702.5 m (1949-2305 ft) drilled depths, 594-702 m (1948-2303 ft) true vertical depths (Johnson et al., 1994). |
| Reference(s): |
| 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. |
| 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. |
| Taylor, S R. 1983. A stable isotope study of the Mercia Mudstones (Keuper Marl) and associated sulphate horizons in the English Midlands. Sedimentology, Vol. 30, 11-31. |
| Warrington, G, and Ivimey-Cook, H C. 1992. Triassic. In: Cope, J C W, Ingham, J K, and Rawson, P F (eds.) Atlas of palaeogeography and lithofacies. Geological Society, London, Memoir No. 13, 97-106. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
