| Computer Code: |
HAHY |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Guadalupian Epoch (PUG)
— Lopingian Epoch (PUL) |
| Lithological Description: |
The Hauptanhydrit Formation consists of white or pale grey anhydrite. It is often described as soft and amorphous, or microcrystalline and hard (e.g. 41/25a-l). Locally, minor intercalations of yellow-brown, microcrystalline dolomite are recorded (e.g. 49/25-1). Thin argillaceous laminae have been noted in a number of wells. At its extreme landward margin, the Hauptanhydrit Formation includes interbedded soft, grey and dark grey mudstone (e.g. 53/2-2) and passes laterally into grey, dark grey and red-brown mudstone with anhydrite interbeds of the Blakeney Formation (e.g. 53/1-1 and 53/1-2). Marginal facies of the Z3 anhydrites have been cored in many boreholes in northeast England, where they are mainly composed of nodular and cumuloid anhydrite interbedded with laminated anhydrite (Smith, 1989 and references therein). In more basinal sections, a thin unit of halite up to about 4 m thick locally occurs at the base of the Hauptanhydrit Formation (e.g. 43/26-5 and 48/13-2A). |
| Definition of Lower Boundary: |
The lower boundary of the Hauptanhydrit Formation is usually marked by a sharp or gradual downward change from white or pale grey anhydrite to grey, microcrystalline dolomite (e.g. 41/25a-1) or anhydritic dolomite of the Plattendolomit Formation. It is marked on wireline logs by a downward decrease in density, an increase in gamma-ray values and commonly an increase in velocity (e.g. 41/25a-1). |
| Definition of Upper Boundary: |
The top of the Hauptanhydrit Formation is normally marked by a sharp downward change from white to clear and pink halite of the Leine Halite Formation or undivided Zechstein salt to white to pale grey anhydrite and dolomitic anhydrite. It is characterized on wireline logs by a sharp downward increase in velocity and density. At the extreme margins of the Hauptanhydrit Formation, where it includes a significant proportion of mudstone, the log character associated with this boundary becomes variable (e.g. 53/1-1). |
| Thickness: |
Generally, the Hauptanhydrit Formation is thicker in more marginal sections, with thin developments in the basin centre (e.g. 42/10a-l). However, it locally shows dramatic and complex thickness variation over relatively short distances. For example, it reaches over 45 m thick in 49/24-4, but is less than 3 m thick in the nearby well 49/23-2. |
| Geographical Limits: |
The Hauptanhydrit Formation is widely distributed across the Southern Permian Basin and passes northwards into the Turbot Anhydrite Formation on the Mid North Sea High (Cameron, 1993). |
| Parent Unit: |
Zechstein Group (ZG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
North Sea well 41/25a- 1: 1238-1258 m (4061-4127 ft) (Johnson et al. 1994). |
| Reference Section |
North Sea well 43/26- 5: 2650-2655 m (8694-8711 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 48/13- 2A: 1978-2008.5 m (6490-6590 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 49/26- 4: 1691.5-1695.5 m (5550-5563 ft) (revised 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. |
| 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. |
| 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. |
| Smith, D B. 1980. The evolution of the English Zechstein basin. In: Fuchtbauer, H, and Peryt, T M (eds.) The Zechstein basin with emphasis on carbonate sequences. Contributions to Sedimentology 9, 7-34. |
| Smith, D B, Brunstrom, R G W, Manning, D I, Simpson, S and Shotton, F W. 1974. A correlation of Permian rocks in the British Isles. Geological Society of London Special Report No. 5. |
| Smith, D B, Harwood, G M, Pattison, J and Pettigrew, T H. 1986. A revised nomenclature for Upper Permian strata in eastern England. 9-17 in Harwood, G M and Smith, D B (editors). The English Zechstein and Related Topics. Geological Society Special Publication No.22. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
