The BGS Lexicon of Named Rock Units — Result Details

Denbury Crinoidal Limestone Formation

Computer Code: DCL Preferred Map Code: notEntered
Status Code: Full
Age range: Eifelian Age (DI) — Eifelian Age (DI)
Lithological Description: The Denbury Crinoidal Limestone occurs in the Denbury Unit (i.e. the thickness of rock that is bound by the Forder Green Thrust at the base, and normal faults (including the Ipplepen Fault) at the top), in which it is identified within the Beacon Hill Succession, Torbryan Succession and the Ugbrooke - East Ogwell Succession. The type locality occurs in the Ugbrooke - East Ogwell Succession; in an old quarry at [SS 8203 6912], crinoid debris in a shaly matrix or fine-grained calcareous cement is seen. Elsewhere in this Succession, either coarsely crystalline crinoidal limestone [SX 8234 7029] or limestone with red mudstone (i.e. [SS 8203 6911]) predominates.
Definition of Lower Boundary: The lower boundary of the Denbury Crinoidal Limestone in the Ugbrooke - East Ogwell and Torbryan Successions is conformable with the Nordon Slate. This contact may be identified in the field by the transition from a sequence of greenish-weathering black or bluish-grey slates with local interbeds of dark grey / black limestones in which the bedding is obscured by cleavage, with local spilites, tuffs and small intrusions of dolerite to the rock types characteristic of the Denbury Crinoidal Limestone, as described in the lithology description above.
Definition of Upper Boundary: The upper boundary of the Denbury Crinoidal Limestone in the Ugbrooke - East Ogwell Succession is conformable with the Chercombe Bridge Limestone, a contact which is identified in the field by a transition from the lithologies associated with the Denbury Crinoidal Limestone (described in lithology section above) to well bedded limestone, fine to medium grained, dark grey to bluish-black, with rich fauna including tabulate and rugose corals, dendroid stromatoporoids, characteristic of the Chercombe Bridge Limestone. In the Torbryan Succession, the upper boundary is with the Pulsford Limestone, a transition recognised in the field by the change from the lithologies of the Denbury Crinoidal Limestone (described above) to medium to dark grey thinly bedded limestones of the Pulsford Limestone.
Thickness: Up to 213 m.
Geographical Limits: Area around Denbury [SX 8203 6912], West Ogwell [SX 8240 7040], Chercombe Bridge [SX 8331 7113] and around Torbryan [SX 8208 6691] - all in south Devon.
Parent Unit: Not Applicable (-)
Previous Name(s): Denbury Crinoidal Limestone (-851)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Old quarry, 365 m north-west of Denbury. Selwood and others, 1984. 
Reference(s):
Selwood, E B, Edwards, R A, Simpson, S, Chesher, J A, Hamblin, R J O, Henson, M R, Riddolls, B W and Waters, R A. 1984. Geology of the countryside around Newton Abbot. Memoir of the British Geological Survey, Sheet 339 (England and Wales). 
Ussher, W A E. 1913. Geology of the country around Newton Abbot. Memoir of the British Geological Survey, Sheet 339. (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E339