The BGS Lexicon of Named Rock Units — Result Details

Little Orme Limestone Member

Computer Code: LOLS Preferred Map Code: notEntered
Status Code: Full
Age range: Asbian Substage (CR) — Asbian Substage (CR)
Lithological Description: Knoll reef limestones comprising highly fossiliferous, massive, pale, fine-grained, recrytallised and locally dolomitised limestones with abundant calcite-lined former cavities with internal geopetal sediment (stromatactis). Contains a rich brachiopod and goniatite fauna. During the time of late Asbian carbonate platform development in North Wales a series of knoll reefs formed along, and serve to define, the platform margin. The knoll reef facies interdigitate with platformal facies on one side, and resedimented basinal facies of the Craven Group on the other.
Definition of Lower Boundary: Entry of massive "reef" limestones above well-bedded Loggerheads Limestone Formation; also passes laterally into Loggerheads Limestone Formation.
Definition of Upper Boundary: Not seen, but was probably overlain unconformably by red beds of the late Westphalian Warwickshire Group, or by Permo - Triassic strata (? Kinnerton Sandstone Formation).
Thickness: c.50m
Geographical Limits: Little Orme, Llandudno, (SH 81 82) North Wales.
Parent Unit: Loggerheads Limestone Formation (LGHL)
Previous Name(s): "Knoll Reef Limestones" (-4168)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Little Orme, Llandudno, provides extensive, but largely inaccessible cliff and quarry sections through massive "reef" limestones. The lateral (southwards) transition into bedded limestones of the Loggerheads Limestone Formation is well displayed on the south side of the Little Orme. (Warren et al., 1984). 
Reference(s):
Warren, P T, Price, D, Nutt, M J C and Smith, E G. 1984. Geology of the country around Rhyl and Denbigh. Memoir for 1:50 000 geological sheets 95 and 107 and parts of sheets 94 and 106. 
Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable