| Computer Code: |
KIDS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Westphalian Stage (CW)
— Stephanian Stage (CS) |
| Lithological Description: |
The group comprises mainly mudstones and siltstones, but with significant interbedded sandstones, especially in the upper part, and with coals and seatearths, predominantly in the lower part. The lithofacies throughout the Kidston Group are arranged in cyclic units. Strata of Langsettian to early Bolsovian age comprise grey coal-bearing, upward-coarsening cyclothems of delta plain origin (Guion and Fielding, 1988). More arenaceous, fluviatile cycles of late Bolsovian to Westphalian D age (cf. Besly, 1988; Ramsbottom et al., 1978; Hamblin and Coppack, 1995) comprise primary red (and subordinate grey) upward-fining units. Cantabrian and Stephanian strata may occur in the core of the Quadrant 109 Syncline (Jackson and Mulholland, 1993). |
| Definition of Lower Boundary: |
The base of the Kidston Group is taken at the base of the Subcrenatum Marine Band (cf. Ramsbottom et al., 1978) though this horizon has not been identified conclusively to date offshore. Precise recognition of the lower boundary of the Kidston Group is unsatisfactory using spore dating and analysis from cuttings, and is dependent chiefly on identification of the wireline log signature of the Subcrenatum Marine Band - generally a high gamma mudstone (Whittaker et al., 1985; Penn, 1987; Leeder et al., 1990) - or recovery of the eponymous goniatite. In the south, offshore to the west of the Vale of Clwyd Fault, the Subcrenatum Marine Band may be absent, and westwards, progressively higher strata of the Kidston Group are thought to rest unconformably on the Bisat Group and, locally, adjacent to Anglesey, on the Garwood Group (BGS, 1994; Williams and Eaton, 1993). |
| Definition of Upper Boundary: |
The top of the Kidston Group is marked everywhere by the Variscan Unconformity. At this boundary, the juxtaposed lithologies and resulting wireline log responses are extremely varied. In the North Irish Sea the youngest preserved Kidston Group ranges in age from ?Stephanian in the Quadrant 109 Syncline to earliest Langsettian. |
| Thickness: |
Offshore in available wells and shallow BGS boreholes, only beds of Langsettian and early Duckmantian age are believed to have been drilled; Bolsovian and Westphalian D strata subcrop Permo-Triassic rocks offshore from North Wales (Smith, 1985; Williams and Eaton, 1993; Jackson et al., 1995). The maximum thickness proved to date in available offshore wells is 485.5 m in 110/20-1, in a sequence dated by palynology as Langsettian to Duckmantian; this considerable thickness is comparable with equivalents nearby in south Lancashire (Ramsbottom et al., 1978). Seismic data suggest that a relatively complete succession of the Kidston Group up to 4000 m thick (comprising both Westphalian and ?Stephanian rocks) is likely to be present in the core of the Quadrant 109 Syncline (Jackson and Mulholland, 1993). |
| Geographical Limits: |
The Kidston Group was deposited originally, in whole or in part, over the entire East Irish Sea Basin and much of the North Irish Sea. Onshore equivalents overlap Dinantian rocks in SW Anglesey to rest on the Precambrian (Smith, 1985; Calver and Smith, 1974). The group was removed by pre-Permian erosion from structural culminations which were created during the Variscan Orogeny (Smith, 1985; BGS, 1994; Jackson et al., 1995). |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
Irish Sea well 110/02b- 10: 2167-2354.5 m (7110-7725 ft) below KB (Jackson and Johnson, 1996). The larger part of the Kidston Group has been removed by pre-Permian erosion in all available wells in the East Irish Sea. Stratigraphically more complete reference sections may be proposed as additional well sections enter the public domain. In this section, only beds dated by spores as early and middle Langsettian have been preserved beneath the Variscan Unconformity. |
| Reference(s): |
| Besly, B M. 1988. Palaeogeographic implications of late Westphalian to early Permian red-beds, Central England. 200-221 in Sedimentation in a synorogenic basin complex; the Upper Carboniferous of Northwest Europe. Besly, B M, and Kelling, G (editors). (Glasgow: Blackie.) |
| Cope, J W C, Ingham, J K, and Rawson, P F. 1992. Atlas of palaeogeography and lithofacies. Geological Society Memoir, No. 13. |
| Guion, P D, and Fielding, C R. 1988. Westphalian A and B sedimentation in the Pennine Basin, UK. 153-177 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of north-west Europe. Besly, B M, and Kelling, G (editors). (Glasgow and London: Blackie.) |
| Hamblin, R J O and Coppack, B C, 1995. Geology of Telford and the Coalbrookdale Coalfield. Memoir of the British Geological Survey, parts of Sheets 152 and 153 (England and Wales). |
| Jackson, D I, and Mulholland, P. 1993. Tectonic and stratigraphic aspects of the East Irish Sea Basin and adjacent areas: contrasts in their post-Carboniferous structural styles. In: Parker, J R (ed.) Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, 791-808. The Geological Society, London. |
| Jackson, D I, Jackson, A A, Evans, D, Wingfield, R T R, Barnes, R P, and Arthur, M J. 1995. United Kingdom offshore regional report: the geology of the Irish Sea. HMSO, London, for the British Geological Survey. |
| Leeder, M, Raiswell, R, Al-Biatty, H, McMahon, A and Hardman, M. 1990. Carboniferous stratigraphy, sedimentation and correlation of well 48/3-3 in the southern North Sea Basin; integrated use of palynology, natural gamma/sonic logs and carbon/sulphur geochemistry. Journal of the Geological Society, London 147, 287-300. |
| Penn, I.E. 1987. Geophysical logs in the stratigraphy of Wales and adjacent offshore and onshore areas. Proceedings of the Geologists' Association, 98, 275-314. |
| Ramsbottom, W H C, Calver, M A, Eagar, R M C, Hodson, F, Holliday, D W, Stubblefield, C J and Wilson, R B. 1978. A correlation of the Silesian rocks in the British Isles. Geological Society of London, Special Report No.10. |
| Stubblefield, C J and Trotter, F M, 1957. Divisions of the Coal Measures on Geological Survey Maps of England and Wales. Bulletin of the Geological Survey of Great Britain, No.13, p.1-5. |
| British Geological Survey. 1994. East Irish Sea (Special Sheet Edition, Solid Geology). 1:250 000, British Geological Survey, Edinburgh. |
| Calver, M A. 1969. Westphalian of Britain. Compte Rendu du Sixieme (6me) Congrès International de Stratigraphie et de Géologie du Carbonifère, Sheffield, (1967), Vol. 1, 233-254. |
| Calver, M A, and Smith, E G. 1974. The Westphalian of North Wales. 169-183 in The Upper Palaeozoic and post-Palaeozoic rocks of Wales. Owen, T R (editor). (Cardiff: University of Wales Press.) |
| Goossens, R F, Smith, E G, and Calver, M A. 1974. Westphalian. 87-114 in The geology and mineral resources of Yorkshire. Rayner, D H, and Hemingway, J E (editors). (Leeds: Yorkshire Geological Society.) |
| Smith, N J P (compiler). 1985. Pre-Permian geology of the United Kingdom (south sheet). British Geological Survey 150th Anniversary Publication. British Geological Survey, Keyworth. |
| Whittaker, A, Holliday, D W, and Penn, I E. 1985. Geophysical logs in British stratigraphy. Geological Society, London, Special Report No. 18. |
| Williams, G D, and Eaton, G P. 1993. Stratigraphic and structural analysis of the Late Palaeozoic-Mesozoic of NE Wales and Liverpool Bay: implications for hydrocarbon prospectivity. Journal of the Geological Society, London, 150, 489-499. |
| Jackson, D I and Johnson, H, 1996. Lithostratigraphic nomenclature of the Triassic, Permian and Carboniferous of the UK offshore East Irish Sea Basin, British Geological Survey, Nottingham. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
