The BGS Lexicon of Named Rock Units — Result Details
Chanter Sandstone Member
| Computer Code: | CHNT | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Kimmeridgian Age (JD) — Kimmeridgian Age (JD) | ||
| Lithological Description: | Five lithofacies have been described: 1) Bioturbated, fossiliferous marine mudstones and siltstones with thin, poorly sorted, very fine grained, glauconitic sands at their base. 2) Bioturbated, silty, fine-grained sandstones with fragments of bivalves and belemnites. 3) Well sorted, massive to cross-bedded, bioturbated, medium-grained sandstones with sporadic shell debris. 4) Well sorted, planar to cross-bedded, coarse-grained sandstones. 5) Upward fining, very coarse- to coarse-grained, cross-bedded sandstones. Locally, argillaceous and bioturbated sandstones with very high gamma-ray values ('Hot Sands member' of Waddams and Clark, 1991) occur in the upper part of the member. In many wells the lithofacies of the Chanter Sandstone Member are stacked in upward-coarsening cycles (e.g. well 15/16-6) (Turner et al., 1984). In the type section there are three large scale upward coarsening cycles and two upward fining cycles occur (Richards et al., 1993). The mudstones within the member are commonly dark grey, carbonaceous and micaceous. In the Ivanhoe and Rob Roy fields, the basal unit comprises organic-rich mudstones with pyritic nodules, passing up into bioturbated mudstones and siltstones grading up into argillaceous sandstones (Parker, 1991). In the Piper Field Maher (1981) and Schmitt and Gordon (1991) recognised seven subunits in the Chanter Sandstone Member, informally designated 'C' to 'I' in descending order. | ||
| Definition of Lower Boundary: | The base of the Chanter Sandstone Member, where it rests on the Pibroch Sandstone Member, is placed at the base of a widespread marine mudstone informally known as the 'I Shale' (of Maher, 1981). Where the Pibroch Sandstone Member is missing, the base is placed either at the base of the Kimmeridgian shallow marine sandstone section, or at the base of a thin unit of Kimmeridge Clay mudstone (the 'I Shale'). | ||
| Definition of Upper Boundary: | The top is commonly defined by the down-section change from mudstones or siltstones to sandstones. Wireline log signatures often show a transitional change across the boundary, but on structural highs it may be sharp. The top of the member can be difficult to define from wireline log data. This is particularly so when the Claymore Sandstone Member overlies the Chanter Sandstone Member (e.g. in well 15/12-1), although in some areas a thin unit of Kimmeridge Clay separates the two. | ||
| Thickness: | Up to 300 m. | ||
| Geographical Limits: | Central part of the Witch Ground Graben between Halibut Horst and Fladen Ground Spur (within ts 14 and 15). | ||
| Parent Unit: | Piper Formation (PIPR) | ||
| Previous Name(s): | Tartan Upper Piper Sand
(-5161)
15/16-6 Sand Member (-5153) Chanter Member (-5154) Hot Sand Member (-5155) Lower Shale Member (-5157) Main Piper Sand (-5158) I Shale (-5156) Main Sand Member (-5159) Tartan Hot Sands (-5160) |
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| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | North Sea well 15/16- 9: 3652.5-3849.5 m (11983-12629 ft) below KB (Richards et al., 1993). | ||
| Reference Section | North Sea well 15/16- 6: 3612-3787.5 m (11850-12426 ft) (Richards et al., 1993). | ||
| Reference Section | North Sea well 15/22- 4: 3721.5-3776 m (12210-12388 ft) (Richards et al., 1993). | ||
| Reference(s): | |||
| Parker, R H. 1991. The Ivanhoe and Robb Roy fields, Block 15/21a-b, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields, 25 years commemorative volume. Memoir of the Geological Society, London, 14, 353-360. | |||
| Schmitt, H and Gordon, A F. 1991. The Piper Field, Block 15/17, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields 25 years commemorative volume. Memoir of the Geological Society, London, 14, 361-368. | |||
| Turner, C C, Richards, P C, Swallow, J L and Grimshaw, S P. 1984. Upper Jurassic stratigraphy and sedimentary facies in the Central Outer Moray Firth Basin, North Sea. Journal of Marine and Petroleum Geology, 1, 105-117. | |||
| Waddams, P and Clark, N M. 1991. The Petronella Field, Block 14/20b, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields, 25 years commemorative volume. Memoir of the Geological Society, London, 14, 353-360. | |||
| Coward, R N, Clark, N M and Pinnock, S J. 1991. The Tartan Field, Block 15/16, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields, 25 years commemorative volume. Memoir of the Geological Society, London, 14, 377-384. | |||
| 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. | |||
| O'Driscoll, D, Hindle, A D and Long, D C. 1990. The structural controls on Upper Jurassic and Lower Cretaceous reservoir sandstones in the Witch Ground Graben, UK 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. | |||
| Maher, C E. 1981. The Piper Oil Field. In: Illing, L V and Hobson, G D (eds.) Petroleum Geology of the continental shelf of North West Europe, 358-370. [Heyden & Son, London] | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||