Stone Gill Limestone Formation
Stone Gill Limestone Formation is part of the Ravenstonedale Group
The Stone Gill Limestone Formation comprises grey, porcellanous limestone and thin dolostone, with beds of argillaceous limestone, sandstone and mudstone common above the base. Calcretes, desiccation structures and pseudomorphs after evaporites are also present.
The presence of calcretes, desiccation structures and evaporite pseudomorphs (Holliday et al., 1979) indicate deposition in a quiet, nearshore to peritidal restricted marine environment.
The type section is in Stone Gill (NY 718 040) as defined by Ramsbottom (1973). A locality in the Appleby district is Shap Abbey (NY 5478 1550) where about 18 m of dolostone and ‘magnesian’ limestone is exposed in a cliff on the east bank of the River Lowther (see Garwood, 1913). See also the Wyegarth Gill No. 1 Borehole (BGS Registration Number NY70SW/1) (NY 7201 0354) and the gully section next to the M6 Motorway (NY 600 075) mentioned below with regard to the lower boundary of the formation.
Lower and upper boundaries
The base of the formation is conformable. Defined at a depth of 49.73 m in the Wyegarth Gill No. 1 Borehole (see above) where there is a gradational change in rock type from the underlying sandstones and siltstones of the Marsett Formation to a sequence of limestones, sandstones and mudstones of the Stone Gill Limestone Formation. However, the base can be precisely located in a gully section next to the M6 Motorway (NY 600 075), where calcareous siltstone and limestone beds rest on black marine mudstone beds marking the top of the Marsett Formation (see Pattison, 1990, p. 9; Day, 1992, p. 15; McCormac, 2001, p. 12; Figure 9, Column 16).
The formation is conformably overlain by the Coldbeck Limestone Formation of the Great Scar Limestone Group south of the Anne’s Well Fault (Figure 9, Column 16), and by the Shap Village Limestone Formation, Ravenstonedale Group, north of it.
Up to 100 m thick in the Ravenstonedale area. 20–40 m thick in the Appleby district.
Distribution and regional correlation
Stainmore Trough. In the Kendal area, strata presently assigned to the lower part of a local equivalent of the Martin Limestone Formation, Great Scar Limestone Group of open marine, platform and ramp carbonates facies, is suggested to be more typical of the Ravenstonedale Group. This appears to be further supported by the striking similarity noted in field characteristics between this succession and the Stone Gill Limestone Formation (see Section 6.6.19).
Age and biostratigraphical characterisation
The formation has a restricted marine biota of algae (including Solenopora sp.), foraminifers (including Brunsia sp. and Dainella sp.), Syringopora sp., ‘Camarotoechia’ proava, Cleiothyridina glabistria, vermetid gastropods, and ostracods. It was considered to be early Chadian (Tournaisian) in age by Holliday et al. (1979). However, the upper part has a Pu Zone miospore assemblage, and ‘Camarotoechia’ proava and Cleiothyridina glabistria are late Chadian chronozonal brachiopods (see Garwood, 1913). The succession apparently includes the early–late Chadian (Tournaisian–Visean) boundary but its position is uncertain. It may exist near the top of the formation.
- Garwood, E J.1907.Geology of Teignmouth Parish, (‘History of Northumberland’).Museum Pamphlet, Northumberland,No. 73.
- Holliday, D W, Neves, R, and Owens, B.1979.Stratigraphy and palynology of early Dinantian (Carboniferous) strata in shallow boreholes near Ravenstonedale, Cumbria.Proceedings of the Yorkshire Geological Society, Vol. 42, 343–356.
- Garwood, E J.1913.The Lower Carboniferous succession in the north-west of England.Quarterly Journal of the Geological Society, Vol. 68, 449–596.
- Pattison, J.1990.Geology of the Orton and Sunbiggin Tarn districts: 1:10 000 sheets NY60NW and NE.British Geological Survey Technical Report, WA/90/12.
- Day, A.1992.Lower Carboniferous rocks near Orton, east of Shap.12–18 in Lakeland rocks and landscape a field guide.Dodd, M (editor). (Maryport: Ellenbank Press.)
- McCormac, M.2001.The Upper Palaeozoic rocks of the Shap and Penrith district, Edenside, Cumbria.British Geological Survey Research Report, RR/01/10