The BGS Lexicon of Named Rock Units — Result Details
Darwin Formation
| Computer Code: | DARW | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Pliensbachian Age (JE) — Toarcian Age (JT) | ||
| Lithological Description: | Lenticular bedded, grey siltstones and fine-grained sandstones, heavily bioturbated locally to produce structureless sandy siltstones. Very fine- to coarse-grained sandstones occur in thin (c. 0.6 m), sharp based beds. Thicker (c. 1.3 m) well laminated, rippled and occasionally bioturbated, very fine-grained sandstones also occur. Sandstones are most common in the middle part of the formation. The heterolithic nature of the formation results in an erratic gamma-ray profile. | ||
| Definition of Lower Boundary: | The lower boundary is defined by a downwards passage from siltstones (Darwin Formation) to sandstones (Nansen Formation) and a marked decrease in gamma values. | ||
| Definition of Upper Boundary: | The upper boundary is defined by a downward passage from interbedded sandstones, siltstones and coals (Pentland Formation) to siltstones. The boundary coincides with a marked increase in gamma values. | ||
| Thickness: | 0 to 80 m. | ||
| Geographical Limits: | Beryl Embayment and Viking Graben, in North Sea quadrant 9. | ||
| Parent Unit: | Dunlin Group (DUNL) | ||
| Previous Name(s): | Amundsen Formation
(AMND)
Burton Formation (BURT) Dunlin Group (DUNL) Lower Beryl Floating Sand Grain Unit (-5183) Lower Beryl Shale (-5184) Upper Formation (-5185) |
||
| Alternative Name(s): | Dunlin Group Burton Formation Amundsen Formation |
||
| Stratotypes: | |||
| Type Section | North Sea well 9/13- 19 between 3564.5 and 3608 m below KB (Richards et al., 1993). | ||
| Reference Section | North Sea well 9/08a- 10 between 3951.5 m and 4018 m (Richards et al., 1993). | ||
| Reference Section | North Sea well 9/14b- 2B between 4618 and 4666 m (Richards et al., 1993). | ||
| Reference Section | North Sea well 9/19- 5A between 3767 and 3842 m (Richards et al., 1993). | ||
| Reference(s): | |||
| Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) | |||
| Richards, P C. 1989. Lower and Middle Jurassic sedimentology of the Beryl Embayment, and implications for the evolution of the northern North Sea. Unpublished Ph.D. thesis, University of Strathclyde. | |||
| Richards, P C. 1991. The evolution of Lower Jurassic coastal plain and fan delta sediments in the Beryl Embayment, North Sea. Journal of the Geological Society, London, 148, 1037-1047. | |||
| Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic 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. | |||
| Richards, P C. 1990. The early to mid-Jurassic evolution of the northern North Sea. In: Hardman, R F P and Brooks, J (eds.) Tectonic events responsible for Britain's oil and gas reserves. Special Publication of the Geological Society, London, No.55, 191-205. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||