The BGS Lexicon of Named Rock Units — Result Details

Drygill Mudstone Formation

Computer Code: DRSH Preferred Map Code: DrSh
Status Code: Full
Age range: Longvillian Substage (OL) — Longvillian Substage (OL)
Lithological Description: Fissile, thinly bedded and laminated, grey to black calcareous mudstone and siltstone, with an abundant shelly fauna. Locally, pervasively bleached adjacent to intrusions. The depositional environment was on an open shelf with conditions suitable for the abundant marine fauna. The formation contains a Longvillian fauna of trilobites and brachiopods (Dean, 1963).
Definition of Lower Boundary: Neither the base nor top of the formation are proved because the outcrops are either faulted or in contact with intrusive igneous rocks.
Definition of Upper Boundary: Neither the base nor top of the formation are proved because the outcrops are either faulted or in contact with intrusive igneous rocks.
Thickness: About 200 m seen, but full thickness unknown.
Geographical Limits: Confined within a small outlier on the north side of Carrock Fell in the northern Lake District.
Parent Unit: Dent Group (DNT)
Previous Name(s): Drygill Shales [Obsolete Name and Code: Use DRSH] (-1516)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Drygill Beck and on the surrounding fell side, north side of Carrock Fell, Cumbria [NY 3185 3462 to NY 3260 3441]. 
Reference(s):
Dean, W T, 1963. The Stile End Beds and Drygill Shales in the east and north of the English Lake District. Bulletin of the British Museum of Natural History, Vol.9, No.3, pp47-65. 
Millward, D, and Stone, P. 2012. Stratigraphical framework for the Ordovician and Silurian sedimentary strata of northern England and the Isle of Man. British Geological Survey Research Report, RR/12/04. 119pp. 
Nicholson, H A, and Marr, J E. 1887. On the occurrence of a new fossiliferous horizon in the Ordovician Series of the Lake District. Geological Magazine, Decade 3, Vol. 4, 339–344. 
Elles, G L, and Wood, E M R. 1895. Supplementary notes on the Drygill Shales. Geological Magazine, Vol. 2, 246–249. 
Eastwood, T, Hollingworth, S E, Rose, W C C, and Trotter, F M. 1968. Geology of the country around Cockermouth and Caldbeck. Memoir of the Geological Survey of Great Britain, England and Wales, Sheet 23. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E023