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| Computer Code: | WHM | Preferred Map Code: | WhM |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Toarcian Age (JT) — Toarcian Age (JT) | ||
| Lithological Description: | Medium and dark grey fossiliferous mudstone and siltstone, laminated and bituminous in part, with thin siltstone or silty mudstone beds and rare fine-grained calcareous sandstone beds; dense, smooth argillaceous limestone nodules very common at some horizons; phosphatic nodules at some levels. Nodular and fossiliferous limestones occur at the base in some areas. Formation fully divided into five members in North Yorkshire: in ascending order the Grey Shale, Mulgrave Shale, Alum Shale, Peak Mudstone and Fox Cliff Siltstone members. | ||
| Definition of Lower Boundary: | In Cleveland Basin, base of mudstone resting upon ooidal limestone or sideritic mudstone nodules of the Cleveland Ironstone (see Cox et al., 1999, for more details). Elsewhere, at base of mudstone overlying ironstone of the Marlstone Rock Formation. | ||
| Definition of Upper Boundary: | In most areas, sharp, eroded boundary with limestones or sandstones of the Inferior Oolite Group (East Midlands Shelf) or the Ravenscar Group or Dogger Formation (Cleveland Basin). In Ravenscar area, and in much of Worcester Basin arbitrary boundary in transition to sandy sediments of the Blea Wyke Formation or Bridport Sand Formation respectively. | ||
| Thickness: | Up to about 120 m. | ||
| Geographical Limits: | Cleveland Basin, East Midlands Shelf and Worcester Basin (i.e. Yorkshire coast to Mendip). | ||
| Parent Unit: | Lias Group (LI) | ||
| Previous Name(s): | Coleby Mudstones [Obsolete Name And Code: Use CHAM Or WHM]
(CLM)
Upper Lias [Obsolete Name And Code: See WHM] (ULI) Upper Lias Clay Formation [Obsolete Name And Code: Use WHM] (ULC) Coleby Mudstone Formation [Obsolete Name and Code: Use WHM] (-2531) Upper Lias Clay [Obsolete Name and Code: Use WHM] (-3760) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | Coastal exposures from Hawsker Bottoms [NZ 951 077] to Whitby Harbour [NZ 901 114]. | ||
| Reference Section | Copper Hill Borehole. Depths 17.31 - 63.70 m. | ||
| Type Area | North Yorkshire Coast. | ||
| Reference Section | BGS Stowell Park Borehole, Gloucestershire (Reg. No. SP01SE/1) [SP 0835 1176] 122.28 - 220.50 m depth. | ||
| Reference(s): | |||
| Berridge, N G, Pattison, J, Samuel, M D A, Brandon, A, Howard, A S, Pharaoh, T C, and Riley, N J. 1999. Geology of the Grantham district. Memoir of the British Geological Survey, sheet 127 (England and Wales). | |||
| Cox, B M, Sumbler, M G, and Ivimey-Cook, H C. 1999. A Formational framework for the Lower Jurassic of England and Wales (Onshore Area). British Geological Survey Research Report RR/99/01. | |||
| 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. | |||
| Powell, J H, 1984. Lithostratigraphic nomenclature of the Lias Group in the Yorkshire Basin. Proceedings of the Yorkshire Geological Society, Vol.45, p.51-57. | |||
| Sumbler, M G, Barron, A J M and Morigi, A N, 2000. Geology of the Cirencester district. Memoir of the British Geological Survey, Sheet 235 (England and Wales). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E052 E034 E043 E127 E062 E035 E044 E042 E054 E072 E235 E199 E102 E055 E065 E064 E080 E114 E143 E144 E157 E158 E159 E170 E171 E203 E172 E185 E186 E187 E201 E202 E204 E217 E218 E142 E220 E236 E251 E252 E253 E264 E265 E219 E279 E280 | |||