The BGS Lexicon of Named Rock Units — Result Details

Welton Chalk Formation

Computer Code: WCK Preferred Map Code: WCk
Status Code: Full
Age range: Cenomanian Age (KE) — Turonian Age (KT)
Lithological Description: White, massive or thickly bedded chalk with common flint nodules ("burrow-form flints") but generally lacking tabular flint bands; sporadic marl seams including the Plenus Marls Member ("Black Band" sensu lato) and the Black Band Member (sensu stricto) above at the base.
Definition of Lower Boundary: The lower boundary is the base of the Plenus Marls Member, a unit of buff to green and grey marls and marly chalks, typically 0.5m thick but up to 1.4m in the Cleveland Basin. This rests on an uneven erosion surface that may be stained with iron minerals and glauconite, at the top of a succession of marly chalk (the Ferriby Chalk Formation). The marly basal beds generally form a topographical slack at outcrop, which facilitates the mapping of the base of the formation, and can also be recognised from their geophysical log signature in boreholes.
Definition of Upper Boundary: The upper boundary is at a marked change from massive, rubbly-weathering chalks below, to harder, thinly bedded or nodular chalk (Burnham Chalk Formation) above. This horizon is found just below the Ravendale Flint, a tabular or semi-tabular flint up to 0.25m thick, which is the lowest such flint in the Chalk Group and base of the chalk unit in which such flint bands are common.
Thickness: The formation is approximately 53m thick in the Burnham-Melton Ross area in the central part of the region, and at the type locality of Melton Bottoms or Welton Wold Quarry [SE 970 282]. It is thinner in the south, the equivalent beds averaging about 33m in north Norfolk (Peake and Hancock, 1970). It also may thin slightly across the Market Weighton High, perhaps to as little as 40m in places, but thickens again into the Cleveland Basin where the gamma-ray log of the Fordon No.2 borehole [TA 0689 7360] suggests it is about 55m thick. Whilst Rowe (1904; see also Neale, 1974) suggests it is about 68m thick in the Bempton and Buckton cliff sections between Flamborough and Speeton, according to Mitchell (2000) it is only 55m (cf. Fordon) at Speeton, its most northerly outcrop. Curiously, however, at Thornwick Bay, at the southeastern end of this section, measurement of the upper and greater part of the formation (see Whitham, 1991, (Figure 6, Column 7); Mitchell 2000) shows that it is slightly expanded relative to Speeton, suggesting a total of at least 60m there. This may indicate an eastward thickening towards the offshore extension of the Cleveland Basin, or an error in one or other of these sections, possibly related to structural complications.
Geographical Limits: Scarp area of Yorkshire and Lincolnshire Wolds, and superficial deposit-covered area to the southeast, from Bempton Cliffs south to the Chapel St Leonards-Skegness area on the Lincolnshire coast (see Sumbler, M G, 1999, Fig.1).
Parent Unit: White Chalk Subgroup (WHCK)
Previous Name(s): Welton Formation (-3754)
Chalk With Flints (Lower Part) (-4391)
Middle Chalk Plus Uppermost (Plenus Marls) Of Lower Chalk (-4965)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Sections within the Bempton and Buckton coastal cliffs between North Landing and Speeton. Because of inaccessibility and structural complications, the section has never been described in detail, but see; Rowe, A W, 1904; Neale, J W, 1974; Rawson, P F and Whitham, F, 1992. 
Partial Type Section  Elsham lower pit. This pit carries the basal boundary stratotype for the formation. See Gaunt et al. (1992, p.92, Figure 34). 
Type Area  Humberside area of North Lincolnshire and the East Riding of Yorkshire. 
Type Section  Quarry faces in Melton Bottom (Welton Wold) Quarry near North Ferriby, Yorkshire. The greater part of the succession is visible in the quarry and the lowest beds have been proved in boreholes in the floor of the quarry. See Gaunt, G D, et al, 1992; and Whitham, F, 1991. 
Reference(s):
Wood, C J and Smith, E G. 1978. Lithostratigraphical classification of the Chalk in North Yorkshire, Humberside and Lincolnshire. Proceedings of the Yorkshire Geological Society, Vol. 42, 263-287. 
Neale, J W. 1974. Cretaceous. 225-245 in Rayner, D H and Hemingway, J E (editors), The geology and mineral resources of Yorkshire. (Leeds: Yorkshire Geological Society.) 
Rawson, P F and Whitham, F. 1992. Itinerary XI. Thornwick Bay and North Landing. 94-99 in Rawson, P F and Wright, J K (editors), The Yorkshire Coast. Geologists' Association Guide, No.34. 
Rowe, A W. 1904. The zones of the White Chalk of the English coast. IV - Yorkshire. Proceedings of the Geologists' Association, Vol.18, 193-296. 
Sumbler, M G. 1999. The stratigraphy of the Chalk Group in Yorkshire and Lincolnshire. British Geological Survey Technical Report WA/99/02. 
Whitham, F. 1991. The stratigraphy of the Upper Cretaceous Ferriby, Welton and Burnham formations north of the Humber, north-east England. Proceedings of the Yorkshire Geological Society, Vol.48, 227-254. 
Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp. ISBN 0 852725175 
Gaunt, G D, Fletcher, T P and Wood, C J. 1992. Geology of the country around Kingston upon Hull and Brigg. Memoir of the British Geological Survey, sheets 80 and 89 (England and Wales). 172pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E103 E115 E116 E054 E055 E064 E065 E072 E073 E080 E081 E089 E090 E091