| Computer Code: |
DWDL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Anisian Age (TA)
— Ladinian Age (TD) |
| Lithological Description: |
The Dowsing Formation consists largely of mudstones but a significant amount of bedded halite is present, mostly concentrated in the widespread Röt Halite Member, near the base of the formation, and in the less extensive Muschelkalk Halite Member in the higher part of the formation. The mudstones are red, red-brown, orange-red and green, and silty in part; thin beds of anhydrite occur and beds of grey to buff coloured dolomite are more prominent than in the overlying Dudgeon Formation. |
| Definition of Lower Boundary: |
The base of the Dowsing Formation is defined by a sharp downward change from red-brown mudstones, with dolomite and evaporite interbeds, to the sandstone-dominated sequence of the underlying Bunter Sandstone Formation. This boundary corresponds to an abrupt decrease in gamma-ray values and an increase in velocity. The boundary is an angular unconformity at which the Dowsing Formation oversteps beds within the Bunter Sandstone Formation. |
| Definition of Upper Boundary: |
The top of the Dowsing Formation is placed at a downward change from Dudgeon Formation mudstones, with silty interbeds, thin anhydrites, dolomites and traces of halite, to a sequence in which rather similar mudstones are distinguished by more numerous and prominent beds of grey and buff coloured dolomite. The boundary corresponds to a downhole decrease in gamma-ray values and an increase in velocity at a regionally consistent logmarker that is slightly below the level selected by Rhys (1974) in the type section (49/21-2). |
| Thickness: |
The Dowsing Formation is more than 200 m thick over a large part of the UK Southern North Sea and has a maximum thickness of 420 m in the southeastern part of Quadrant 43. The formation is partially eroded around the basin margins (Cameron, 1993). |
| Geographical Limits: |
Occurs over a large part of the UK Southern North Sea. |
| Parent Unit: |
Haisborough Group (HAI)
|
| Previous Name(s): |
Dowsing Dolomite Formation [Obsolete Name and Code: Use DWDL]
(-4628)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 49/21- 2 (Rhys, 1974): 1161.5-1375.5 m (3810-4512 ft) below KB (metric conversion revised; revised top). Rhys (1974) regarded this section as possibly faulted at the level of the base of the Muschelkalk Halite Member and illustrated potentially missing beds with a section from well 49/22-1. The characters of this part of the succession, and the lateral variations within the formation, are better illustrated in the reference sections. |
| Reference Section |
North Sea well 42/15b- 1: 862-1025 m (2828-3362 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 47/05a- 2: 1438-1773.5 m (4718-5818 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 49/21- 3: 994.5-1324 m (3262-4344 ft) (Johnson et al., 1994). |
| Reference Section |
North Sea well 53/02- 3: 829-1082 m (2720-3550 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. 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. |
| 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. |
| Reitz, E. 1985. Palynologie der Trias in Nordhessen und Siidniedersachsen. Geologische Abhandlungen Hessen 86. |
| 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. |
| Visscher, H. 1966. Paleobotany of the Mesophytic III. Plant microfossils from the Upper Bunter of Hengelo, the Netherlands. Acta Botanica Neerlandica 15, 316-375. |
| Visscher, H, and Commissaris, A L T M. 1968. Middle Triassic pollen and spores from the Lower Muschelkalk of Winterswijk (The Netherlands). Pollen et Spores 10, 161-176. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
