The BGS Lexicon of Named Rock Units — Result Details
Cloud Hill Dolostone Formation
| Computer Code: | CLHD | Preferred Map Code: | CHD |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Holkerian Substage (CQ) — Asbian Substage (CR) | ||
| Lithological Description: | Grey, pale buff and reddish grey, fine- to coarse-crystalline, thin to very thickly bedded dolostones, with shaly mudstone or clay partings and beds. Bioclastic grainstones interbedded with mudstones and dolostones are defined as the Cloud Wood Member, calcareous mudstones seen where undolomitised. The mudmound reef dolostones are typically buff to grey, massive, fine-grained and fossiliferous with common brachiopods, crinoids, corals, gastropods, nautiloids and ammonoids. | ||
| Definition of Lower Boundary: | The lower boundary is an unconformity, possibly in part a shear surface, with biosparites and micrites of the Milldale Limestone Formation of early Asbian age below, locally marked by the incoming of mudstone-dominated sediments, such as the Cloud Wood Member, and may be crowded with Thallasinoides trace fossils. | ||
| Definition of Upper Boundary: | The top is taken at the incoming of the first palaeosol of friable siltstone and sandstone, displaying carbonate nodules of the overlying Ticknall Limestone Formation. | ||
| Thickness: | At least 125 m thickness proved at type section. | ||
| Geographical Limits: | The outcrop is restricted to inliers at Barrow Hill, Cloud Hill and Breedon Hill across south Derbyshire and north-west Leicestershire; the subcrop extends at least to the Ticknall area [SK 35 24]. | ||
| Parent Unit: | Peak Limestone Group (PKLM) | ||
| Previous Name(s): | Carboniferous Limestone [Obsolete Name and Code: Use CL]
(-4550)
Cloud Hill Dolomite Formation [Obsolete Name and Code: Use HYBH, CLHD] (-133) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Old quarries, Barrow Hill, displaying well exposed mudmound reef dolostones. | ||
| Type Section | Cloud Hill Quarry, at least 125 m thickness, displaying basal unconformity and mudmound reef dolostone. | ||
| Reference Section | Top: BGS Ticknall Borehole (SK32SE/103), between 55.4 m and 92.3 m. | ||
| Reference(s): | |||
| Ambrose, K, and Carney, J N. 1997. Geology of the Breedon on the Hill area. British Geological Survey Technical Report WA/97/42. | |||
| Carney, J N, Ambrose, K and Brandon, A. 2001. Geology of the country between Burton, Loughborough and Derby. Description of 1:50k Sheet 141 (England and Wales). | |||
| Monteleone, P H, 1973. The Carboniferous Limestone of Leicestershire and south Derbyshire. Unpublished PhD thesis, University of Leicester. | |||
| Mitchell, G H and Stubblefield, C J, 1991. The Carboniferous Limestone of Breedon Cloud, Leicestershire. Geological Magazine, 78, 201-219. | |||
| Parsons, L M. 1918. The Carboniferous Limestone bordering the Leicestershire Coalfield. Quarterly Journal of the Geological Society, 73, 84-110. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E141 | |||