Difference between revisions of "Park Limestone Formation"
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Park Limestone Formation is part of the Great Scar Limestone Group
The name is derived from Park Sop (hematite mine) (SD 213 754) in Low Furness. The Park Limestone of Rose and Dunham (1977) was given formational status by Johnson et al. (2001). It is equivalent to Garwood’s (1913) ‘Nematophyllum (Lithostrotion) minus Subzone’.
The Park Limestone Formation consists of pale grey or cream, weakly bedded, closely jointed, poorly sorted and bioturbated, packstone and grainstone.
Shallow marine carbonate.
The type area is the south Cumbria– Furness area. Reference sections are at Barker Scar (SD 3330 7827) to Capes Head (SD 334 778) (including the crag forming the western boundary of Old Park Wood), and a disused quarry at Ravensbarrow Point (SD 3380 7749). At Barker Scar, the basal 45 m of the formation, and the contact with the underlying Dalton Formation are exposed. At Crown Quarry at about (SD 246 728) and Devonshire Quarry (SD 249 728) more than 150 m of limestone is exposed, comprising approximately the upper half of the Park Limestone and much of the Urswick Limestone formations (see Rose and Dunham, 1977, pp. 35, 48–49).
Lower and upper boundaries
The base of the formation conformably overlies the Dalton Formation (Figure 9, Column 14), and the absence of Garwood’s (1913) ‘Cyrtina carbonaria Subzone’ suggests basal onlap. The upward change from dark grey, bedded packstones of the Dalton Formation to pale grey, unbedded grainstones of the Park Limestone Formation can extend over 1 or 2 m but more generally it is even sharper.
The top of the Park Limestone Formation is a well-developed palaeokarstic surface, locally with clay-filled potholes. This upper boundary shows change from typical Park Limestone to pale grey, thickly bedded, ‘pseudobrecciated’ limestone of the overlying Urswick Limestone Formation.
The formation maintains a nearly constant thickness of about 125 m throughout its outcrop.
Distribution and regional correlation
South Cumbria. The formation extends from around Dalton-in-Furness in the west, to near Carnforth in the east.
Age and biostratigraphical characterisation
Fossils are uncommon, but include Diphyphyllum smithi, Lithostrotion minus, Linoprotonia ashfellensis andL. corrugatohemispherica, all of which are restricted to the unit in the south Cumbria area. The formation almost equates to the Holkerian Stage. The lower lithostratigraphical boundary seen in the Holkerian Stratotype at Barker Scar (SD 3330 7827) (George et al., 1976) is 4.2 m lower than the Holkerian/Arundian stage boundary (see Johnson et al., 2001, pp. 60–61). It should be noted that Riley (1993) stated that it seems likely that a considerable non-sequence is developed at Barker Scar and that the stratotype will require relocation.
- 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).
- 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).
- Garwood, E J.1913.The Lower Carboniferous succession in the north-west of England.Quarterly Journal of the Geological Society, Vol. 68, 449–596.
- George, T N, Johnson, G A L, Mitchell, M, Prentice, J E, Ramsbottom, W H C, Sevastopulo, G D, and Wilson, R B.1976.A correlation of Dinantian rocks in the British Isles.Geological Society of London Special Report, No.7.