Red Hill Limestone Formation

From Earthwise
Jump to navigation Jump to search

Red Hill Limestone Formation (RHO), Carboniferous, Northern England Province[edit]

Red Hill Limestone Formation is part of the Great Scar Limestone Group

Name[edit]

The name is derived from Red Hills Quarry, Millom, south-west Cumbria. The Red Hill Oolite of Rose and Dunham (1977[1]) was given formational status by Johnson et al. (2001[2]).

Lithology[edit]

The Red Hill Limestone Formation comprises pale grey, closely jointed, coarse-grained, intraclastic peloidal grainstone, which is cross-bedded in part. Rubbly textured limestone with probable nodular calcrete (the ‘Algal Band’ of Rose and Dunham, 1977[1]) marks the base of this unit.

Genetic interpretation[edit]

Transgressive shallow marine carbonate.

Stratotype[edit]

The original type section at Red Hills Quarry (SD 178 793), Millom includes 20 m of massive or poorly bedded, bioclastic limestone but the section is now largely obscured (see Rose and Dunham, 1977, p. 40[1]). Reference sections exist at Dunnerholme (SD 2128 7963) where 21 m of the base and lower parts of the formation are present as pale grey, ‘oolitic’ and fragmental limestones with some beds being secondarily dolomitised (Rose and Dunham, 1977, p. 41[1]; Johnson et al., 2001, p. 59[2]), and Meathop Quarry (SD 4316 7928), Grange-over-Sands where the base of the formation is taken at a sharp, erosional contact with the subjacent Martin Limestone Formation (Johnson et al., 2001, p. 59[2]).

Lower and upper boundaries[edit]

The base of the formation is a non-sequence. The lower boundary is taken at the base of the ‘Algal Band’ of Rose and Dunham (1977[1]) in the type locality and elsewhere, or at upward change from the carbonate mudstones, grainstones and fine oolites of the Martin Limestone Formation to coarse grainstone (Figure 9, Column 14).

The conformable upper boundary of the formation is the base of the overlying dark grey crinoidal packstones with conspicuous thin siltstone interbeds of the Dalton Formation.

Thickness[edit]

The formation is up to about 60 m thick.

Distribution and regional correlation[edit]

South Cumbria.

Age and biostratigraphical characterisation[edit]

Early Arundian. Fossils are not common, but include the corals Koninckophyllum sp., Michelinia megastoma and Palaeosmilia murchisoni. The base of the formation is coincident with the Arundian/Chadian boundary. The formation corresponds to the ‘Camarophoria isorhyncha’ subzone of Garwood (1913[3]).

References[edit]

  1. 1.0 1.1 1.2 1.3 1.4 Rose, W C C, and Dunham, K C.1977.Geology and hematite deposits of South Cumbria.Economic Memoir of the Geological Survey of Great Britain, Sheet 58, part 48 (England and Wales).
  2. 2.0 2.1 2.2 Johnson, E W, Soper, N J, and Burgess, I C.2001.Geology of the country around Ulverston.Memoir of the British Geological Survey, Sheet 48 (England and Wales).
  3. Garwood, E J.1913.The Lower Carboniferous succession in the north-west of England.Quarterly Journal of the Geological Society, Vol. 68, 449–596.