| Computer Code: |
ROHL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Anisian Age (TA)
— Anisian Age (TA) |
| Lithological Description: |
The Röt Halite Member comprises halite with thin interbeds of red, green and grey mudstone and some anhydrite. The member shows low gamma-ray values and high velocities and a mainly parallel-sided log signature representive of halite; narrow peaks of high gamma-ray and lower velocity values correspond to mudstone interbeds. |
| Definition of Lower Boundary: |
The base of the Röt Halite Member is placed at the downward change from halite to red-brown mudstones in the lowest part of the Dowsing Formation. The boundary is marked by an abrupt downward increase in gamma-ray values and a decrease in velocity. |
| Definition of Upper Boundary: |
The top of the Röt Halite Member is placed at a downward change, in the lower part of the Dowsing Formation, from red-brown mudstones, with beds of dolomite and some anhydrite, to halite. The boundary is marked by an abrupt downward change from very variable gamma-ray values and velocities, to lower gamma-ray and slightly higher velocity values. In southern parts of quadrants 42, 43 and 44, and northern parts of quadrants 47 and 48, the boundary is 25 to 30 m below the base of the less extensive 'Upper Röt Halite Member' of Southworth (1987, cited in Cameron et al., 1992, pp.60-63). |
| Thickness: |
Thicknesses are commonly over 30 m and exceed 60 m in parts of quadrants 42, 43, 44 and 48 (Cameron et al., 1992). |
| Geographical Limits: |
The Röt Halite Member is the most extensive of the three halite members recognized in formations of the Haisborough Group and is the only one to extend westwards into the eastern UK onshore. It is more extensive than the Muschelkalk Halite Member, which is present higher in the Dowsing Formation, and is recognized over about 60% of the offshore area occupied by that formation. |
| Parent Unit: |
Dowsing Formation (DWDL)
|
| 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): 1348-1367 m (4423-4485 ft) below KB. The type well does not show the relationship of the Röt Halite Member to the thinner, less extensive, 'Upper Röt Halite Member' of Southworth (1987, cited in Cameron et al., 1992, pp.60-63). The contrasting characters of the succession overlying the Rot Halite Member where the 'Upper Röt Halite Member' is present and where it is absent are illustrated in the reference sections. |
| Reference Section |
North Sea well 43/26- 7: 1339-1411.5 m (4393-4631 ft) drilled depths, 1338.5-1410.5 m (4391-4628 ft) true vertical depths (Johnson et al., 1994). |
| Reference Section |
North Sea well 49/21- 3: 1287.5-1316 m (4224-4317 ft) (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, Crosby, A, Balson, P S, Jeffery, D H, Lott, G K, Bulat, J, and Harrison, D J. 1992. The geology of the southern North Sea. United Kingdom offshore regional report. (London: HMSO for the British Geological Survey.) |
| Geiger, M E, and Hopping, C A. 1968. Triassic stratigraphy of the southern North Sea Basin. Philosophical Transactions of the Royal Society of London B254, 1-36. |
| 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. |
| Southworth, C J. 1987. Lithostratigraphy and depositional history of the Middle Triassic Dowsing Dolomitic Formation of the southern North Sea and adjoining areas. Unpublished Ph.D. thesis, University of Oxford. |
| Van der Zwan, C J, and Spaak, P. 1992. Lower to Middle Triassic sequence stratigraphy and climatology of the Netherlands, a model. Palaeogeography, Palaeoclimatology, Palaeoecology 91, 277-290. |
| Holser, W T, and Wilgus, C K. 1981. Bromide profiles of the Rot salt, Triassic of northern Europe, as evidence of its marine origin. Neues Jahrbuch fur Mineralogie Monatshefte, 1981, H.6, 267-276. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
