| Computer Code: |
WAM |
Preferred Map Code: |
WaM |
| Status Code: |
Full |
| Age range: |
Ypresian Age (GY)
— Ypresian Age (GY) |
| Lithological Description: |
The Walton Member comprises partly bioturbated, silty clays and clayey silts, interbedded with some very fine-grained sandy silty clay. It is micaceous, frequently with lignitic debris and pyrite, but is generally not glauconitic nor calcareous. There is usually a thin basal glauconitic sandy and gravelly bed, or a layer of dispersed well-rounded gravel. Where the Walton Member is thin, it includes several coarse sandy and gravelly seams. It is also characterised by the occurrence of numerous whitish streaks of silt, 1-3 mm diameter and about 5 mm long, which are the remains of a type of tubular foraminiferid (King, 1981; in prep., and unpublished notes). Disseminated lignite is abundant and marine molluscs and fish teeth occur in places.
Marine: inner to outer shelf.
Eocene (Ypresian). |
| Definition of Lower Boundary: |
The Walton Member rests on a discontinuity, usually marked by a flint gravel bed or a glauconitic horizon, or both. It generally overlies the Harwich Formation except where it locally overlies the Lambeth Group (King, 1981; Ellison et al., 1994). |
| Definition of Upper Boundary: |
The top of the Walton Member is marked by the upwards appearance of more homogeneous strata comprising grey claystones and silty clays, in the overlying Ockendon Member (Division A3 of King, 1981). |
| Thickness: |
The Walton Member thickens generally eastwards to a maximum of 17 m (King, 1981, in prep.). |
| Geographical Limits: |
The Walton Member is present throughout the Hampshire and London basins, except in the west, and in East Anglia. |
| Parent Unit: |
London Clay Formation (LC)
|
| Previous Name(s): |
London Clay Basement Bed [Obsolete Name and Code: Use HWH]
(LCBA)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Partial Type Section |
Cliff section at The Naze, Walton-on-the-Naze [TM 267 238]. This exposes the lower 15 m of the unit (Daley, 1999b; King, 1981, fig. 14). |
| Reference Section |
CTRL borehole A2 (TQ38SW 2212) [TQ 330 805] (central London), between 21.50 and 33.25 m depth. |
| Reference(s): |
| Aldiss, D T. 2014. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report OR/14/008. 95 pp. |
| Daley, B. 1999. London Basin: eastern localities, In: Daley, B, Balson, P (Eds.), British Tertiary Stratigraphy. Geological Conservation Review Series 15, pp. 23-72. |
| Ellison, R A, Knox R W O'B, Jolley, D W and King, C, 1994. A revision of the lithostratigraphical classification of the early Palaeogene strata of the London Basin and East Anglia. Proceedings of the Geologists' Association, Vol.105, 187-197. |
| King, C. 1981. The stratigraphy of the London Clay and associated deposits. Tertiary Research Special Paper No.6. (Backhuys: Rotterdam). |
| King, C. in prep. A revised correlation of Palaeogene and Neogene deposits in the British Isles. Geological Society of London Special Report. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E162
|
