The BGS Lexicon of Named Rock Units — Result Details

Wealden Group

Computer Code: W Preferred Map Code: notEntered
Status Code: Full
Age range: Berriasian Age (KR) — Barremian Age (KB)
Lithological Description: Interbedded thick sandstones, siltstones, mudstones ("shales"), limestones and clay ironstones of predominantly non-marine facies. Divided into formations and members. For full details of lithologies see the definitions of the constituent parts.
Definition of Lower Boundary: In the Wealden Basin the base of the Wealden Group is conformable, where the base of non-marine sandstones and siltstones of the Ashdown Formation overlies calcareous mudstones and limestones of the Purbeck Group (Durlston Formation). In the Vectian Basin the undivided Wealden Group non-marine sandstones and siltstones (or at the base of the Wessex Formation on the Isle of Wight) rest conformably on calcareous mudstones and limestones of the Purbeck Group (Durlstone Formation). Towards the basin margins the group is represented by deposits of a limited age range and is unconformable on a variety of older rocks.
Definition of Upper Boundary: The upper boundary is unconformable in the Wealden Basin at a sharp contact between the grey or red mudstones of the Weald Clay Formation with the overlying dark grey or black mudstones of the Atherfield Clay Formation (Lower Greensand Group). It is also unconformable in the Vectian Basin (Isle of Wight) at the sharp contact between the dark finely bedded mudstones of the Vectis Formation (formerly the Wealden Shales) and the dark grey to black mudstones of the Atherfield Clay Formation (at the base of the "Perna Beds" of Casey, 1961). Elsewhere the top is erosional or unconformable with significantly younger beds (e.g. the Lower Greensand Group or Gault Formation).
Thickness: Up to 850 m (Wealden Basin) and c. 500 m (Vectian Basin), thinning to a few metres in marginal areas.
Geographical Limits: The Weald and Vectian basins. The Wealden Group is introduced and redefined to include the Weald Clay Formation. The group's precursors (notably variations of the Hastings "Group"/"Beds") are used on map sheets and in memoirs in Kent, Surrey, Sussex, Hampshire, Dorset and Wiltshire within the Lower Cretaceous Wealden and Vectian basins.
Parent Unit: Not Applicable (-)
Previous Name(s): Wealden (-1259)
Wealden Beds (-1260)
Wealden Facies (-1261)
Wealden Series (-3749)
Wealden Formation (-4955)
Wealden Strata (-3113)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The Weald of Kent and Sussex. The first description of the constituent parts of the succession is by Drew (1861) in the northern Weald area, principally in the Tunbridge Wells (Sheet 303) district (see the Lexicon descriptions for the constituent parts of the Group). Bristow and Bazley (1972) state "The designations of type sections in the Hastings Beds [now Wealden Group] is impracticable. Complete natural sections are unknown for any of the formations, ... cored boreholes provide the most continuous sections available". The details of the appropriate boreholes are given in the formation descriptions.There is no type section designated for the group; see instead the type and reference sections of the group's constituent units. 
Reference Section  The cliff sections from Compton Bay [SZ 36 85] to St. Catherine's Point [SZ 50 75] on the Isle of Wight constitute the type sections for the individual formations designated in the Vectian Basin. 
Reference Section  The cliff sections in Sandown Bay [SZ 58 80 to SZ 62 85] on the Isle of Wight constitute the type sections for the individual formations designated in the Vectian Basin. 
Reference(s):
Rawson, P F. 1992. Cretaceous, 355-388 in Duff, P McL D and Smith, A J (editors), Geology of England and Wales. (London: Geological Society.) 
Kerth, M and Hailwood, E A. 1988. Magnetostratigraphy of the Lower Cretaceous Vectis Formation (Wealden Group) on the Isle of Wight, southern England. Journal of the Geological Society, Vol.145, 351-360. 
White, H J O. 1921. A short account of the geology of the Isle of Wight. Memoir of the Geological Survey of Great Britain, (1994 reprint). 
Drew, F. 1861. On the succession of the beds in the Hastings Sand in the Northern portion of The Weald. Quarterly Journal of the Geological Society, London, Vol.17, 271-286. 
Martin, P J, 1828. A Geological Memoir of Part of Western Sussex. [London.] 
Rawson, P F, Curry, D, Dilley, F C, Hancock, J M, Kennedy, W J, Neale, J W, Wood, C J and Worrsam, B C. 1978. A correlation of Cretaceous rocks in the British Isles. Geological Society of London, Special Report No.9. 
Topley, W. 1875. The geology of the Weald. Memoir of the Geological Survey of England and Wales. 
Casey, R, 1961. The stratigraphical palaeontology of the Lower Greensand. Palaeontology, Vol.3, 487-621. 
Bristow, C R and Bazley, R A. 1972. Geology of the country around Royal Tunbridge Wells. Memoir of the Geological Survey of Great Britain, sheet 303 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable