Difference between revisions of "Shap Village Limestone Formation"
|[unchecked revision]||[checked revision]|
m (1 revision imported)
Latest revision as of 15:53, 26 July 2021
Shap Village Limestone Formation is part of the Ravenstonedale Group
The name is derived from the Village of Shap, Cumbria. The name Shap Village Limestone Formation was introduced by McCormac (2001) and the unit is equivalent to the Shap Limestone of Dakyns et al. (1897; see Millward et al. 2003, p. 13).
The Shap Village Limestone Formation is composed, in its lower part, of well-bedded dolostone with interbeds of siltstone and calcareous sandstone. In its middle part it consists of cross-bedded, dark grey, sandy packstone/grainstone with the coral genus Dorlodotia. In its upper part it comprises finely cross-laminated oolites, thick-bedded calcareous, rippled sandstone, pebbly sandstone, and cross-bedded calcarenite.
The depositional environments include fluvial and marginal marine.
The partial type section is in Force Beck (NY 5684 1384 to 5772 1354) where the basal algal beds are overlain by a mudstone seatearth, dolostone (20–40 m thick) with thin interbeds of siltstone or fine-grained sandstone, of packstone/grainstone (also 20–40 m thick and with thin interbeds of siltstone or fine-grained sandstone), oolitic limestone, and a mixed succession of calcareous sandstone, pebbly sandstone, and oolites. The section is incomplete due to faulting (see McCormac, 2001, pp. 12–13). Another locality in the Appleby district is Loudon Hill (NY 4650 2725), Dacre, where workings in the upper sandstones can be seen (see McCormac, 2001, p. 13).
Lower and upper boundaries
Beds with algal mats and nodules mark the base of the Shap Village Limestone Formation. North of Anne’s Well Fault in the Shap area the formation overlies the limestones with sandstones and mudstones of the Stone Gill Limestone Formation, and north of the River Lowther in Westmorland it overlies the sandstone and conglomerate dominated Marsett Formation.
The top of the Shap Village Limestone Formation is marked by distinctive pebble beds and is overlain conformably by the Ashfell Sandstone Formation (Great Scar Limestone Group) (Figure 14, Column 3).
The formation is 40–120 m thick, and 70–100 m thick in the Appleby district.
Distribution and regional correlation
The Shap–Penrith area, east Cumbria (McCormac, 2001), extended to include equivalent rocks assigned to the ‘Ravenstonedale Limestone’ in the Alston and Brough areas (Arthurton and Wadge, 1981; Burgess and Holliday, 1979).
Age and biostratigraphical characterisation
The coral genus Dorlodotia, described from several localities in the Shap and Askham area (Dean, 2001), indicates a late Chadian age for the bulk of the formation. Garwood (1913) described a coral/brachiopod fauna typical of his Camarophoria isoryncha subzone at the top of the succession at Shap. In the correlation of George et al. (1976), this would place the upper part of the formation in the Arundian. However, more recently, Riley (1993) has argued that all the rocks found at this level in the Ravenstonedale area are Chadian in age, and this cannot be refuted in the apparent absence of of data concerning the presence of archaediscid foraminifers, the first entry of primitive forms defining the base of the Arundian.
- McCormac, M.2001.The Upper Palaeozoic rocks of the Shap and Penrith district, Edenside, Cumbria.British Geological Survey Research Report, RR/01/10
- Dakyns, J R, Tiddeman, R H, and Goodchild, J G.1897.The geology of the country between Appleby, Ullswater and Haweswater.Memoir of the Geological Survey of Great Britain
- Millward, D, McCormac, M, Hughes, R A, Entwistle, D C, Butcher, A, and Raines, M G.2003.Geology of the Appleby district.Sheet explantion of the British Geological Survey,Sheet 30 (England and Wales)
- Arthurton, R S, and Wadge, A J.1981.Geology of the country around Penrith.Memoir of the Geological Survey of Great Britain, Sheet 24 (England and Wales).
- Burgess, I C, and Holliday, D W.1979.Geology of the country around Brough-under-Stainmore.Memoir of the Geological Survey of Great Britain, Sheet 31, parts 25 and 30 (England and Wales)
- Day, J B W.1970.Geology of the country around Bewcastle.Memoir of the Geological Survey of Great Britain, Sheet 12 (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.
- Riley, N J.1993.Dinantian (Lower Carboniferous) biostratigraphy and chronostratigraphy in the British Isles.Journal of the Geological Society of London, Vol. 150, 427–446.