| Computer Code: |
TCL |
Preferred Map Code: |
TCL |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Arundian Substage (CJ) |
| Lithological Description: |
The Tom Croft Limestone Formation comprises mid to dark grey, poorly bedded biosparites (grainstone containing peloids, shelly debris, crinoid fragments and variable quantities of dolomite grains). The formation includes a macrofauna comparable with that of the Dalton Beds of south Cumbria (see Rose and Dunham 1977) and may include a thin basal unit of limestone breccia with siltstone and quartz pebbles.
Shallow marine carbonate. Arundian. |
| Definition of Lower Boundary: |
The base of the formation is disconformable on the limestone, dolostone, sandstone and siltstone of the Penny Farm Gill Formation, Ravenstonedale Group. |
| Definition of Upper Boundary: |
The top of the formation underlies the diachronous Ashfell Sandstone Formation in the Stainmore Trough and the same formation and the Fawes Wood Limestone Formation on the Askrigg Block. |
| Thickness: |
The formation is 60-80 m thick. |
| Geographical Limits: |
Askrigg Block. |
| Parent Unit: |
Great Scar Limestone Group (GSCL)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
River Clough [SD 6954 9143 to 6947 9147], Garsdale, where the lowest beds are cut out by faults (Burgess, 1986, p. 7) but there is an 80 m-thick run (possibly including some repetition) of dominantly dark grey limestone virtually free of mudstone partings (Burgess, 1986, p. 8; see Dunham and Wilson, 1985, p. 28). |
| Reference Section |
Beckermonds Scar Borehole (BGS Registration Number SD88SE/1) [SD 8636 8016] from 209.15 to 267.88 m depth including dominantly dark grey limestone with some mid grey runs (see Wilson and Cornwell, 1982). |
| Reference Section |
BGS Raydale Borehole (BGS Registration Number SD98SW/1) [SD 9626 8474] from about 273 to 350 m depth (see Dunham and Wilson, 1985, fig. 5, cols. 5 and 7). |
| Reference(s): |
| Burgess, I C. 1986. Lower Carboniferous sections in the Sedbergh district, Cumbria. Transactions of the Leeds Geological Association, Vol. 11, 1-23. |
| Wilson, A A and Cornwell, J D. 1982. The Institute of Geological Sciences borehole at Beckermonds Scar, North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol.44, 59-88. |
| Dean, M T, Browne, M A E, Waters, C N and Powell, J H. 2011. A lithostratigraphical framework for the Carboniferous successions of northern Great Britain (onshore). British Geological Survey Research Report, RR/10/007. 165pp. |
| Dunham, K C, and Wilson, A A. 1985. Geology of the Northern Pennine Orefield. Volume 2 Stainmore to Craven. Economic Memoir of the British Geological Survey, Sheets 40, 41 and 50, and parts of Sheets 31, 32, 51, 60 and 61(England and Wales). |
| 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). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E040
|
