| Computer Code: |
ARS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Valanginian Age (KV)
— Valanginian Age (KV) |
| Lithological Description: |
Fine- and medium-grained quartzose cross-bedded sandstone, largely thickly bedded or massive. Commonly referred to as "sandrock" meaning a clean white or greyish white soft quartzose sandstone. The member is believed to become finer-grained towards the south, away from the Horsham-Ardingly type area. The member shows a tendency to "coarsen-upwards" and commonly contains "stringers" of quartz and quartzite pebbles. Natural crags show a cyclic succession from almost parallel bedded units up into shallow trough cross bedded sandstones and capped by massive units with thin units of contorted bedding. |
| Definition of Lower Boundary: |
The lower boundary is rarely exposed but where seen it is a sharp contact, possibly erosional, between thinly interbedded silty fine-grained sandstones and siltstones of the un-named lower part of the informal lower Tunbridge Wells Sand and the thick cross-bedded sandstones of the Ardingly Sandstone Member. For mapping purposes the boundary is placed either at the top of the highest discernible thinly-bedded siltstones and sandstones, or at the base of the prominent "crags" characteristic of the Ardingly Sandstone Member outcrop. |
| Definition of Upper Boundary: |
The upper boundary is conformable or erosional at the junction of the overlying grey to greenish grey mudstones of the Grinstead Clay Member. In places the base of the Grinstead Clay Member is marked by a minor erosion surface on which is developed the informally named Top Lower Tunbridge Wells Pebble Bed (see Allen, 1967). This pebble bed is represented by a "ripple-drift" (climbing ripple) bedded fine- to medium-grained sand with small quartz pebbles. Locally the Cuckfield Stone Bed (which cuts out the lower part of the Grinstead Clay Member) rests directly on the Ardingly Sandstone Member. Here the boundary is clearly erosive with massive sandstones of the Ardingly Sandstone Member underlying the "festoon-bedded", finely trough-cross-bedded sandstones of the Cuckfield Stone Bed. |
| Thickness: |
Maximum 25 to 33m but ranges down to 12.2m at Cuckfield and 18 to 24m around Haywards Heath. |
| Geographical Limits: |
Ardingly Sandstone Member is known from the Horsham, Tunbridge Wells, Sevenoaks, Tonbridge, Lewes and Brighton districts of the central Weald and seems to mirror the known extent of the Grinstead Clay Member. Elsewhere in the Weald the absence of these two units prevents the informal division of the Tunbridge Wells Sand Formation into lower and upper units. |
| Parent Unit: |
Tunbridge Wells Sand Formation (TWS)
|
| Previous Name(s): |
Ardingly Sandstone [Obsolete Name and Code: Use ARS]
(-27)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
In Cuckfield No. 1 borehole TQ22NE19 [2961 2731], see Lake and Thurrell (1974). The Ardingly Sandstone Member is identified between 192.94 and 204.22m depth in the borehole. Massive sandstone(199.03 to 204.22m) and siltstone(195.99 to 199.03m) units at the base are overlain by thinly interbedded siltstone, sandstone and mudstone. |
| Reference Section |
Philpotts Quarry, West Hoathly [TQ 3536 3215] where the upper boundary of the member can be seen. "The quarry exposed a complete section of the Lower Grinstead Clay and Top Lower Tunbridge Wells Pebble Beds and a frost-disturbed junction with the Cuckfield Stone". (Bristow and Bazley, 1972) |
| Reference Section |
The lower boundary of the member can be seen in a stream section near Ditton Place, Handcross [TQ 2821 2980]. The best section showing the base of the Ardingly Sandstone in the Horsham Sheet district is exposed in the stream gorge west of Ditton Place where 9.0m of massive trough cross-bedded sandstone of the member is seen overlying interbedded siltstones and fine-grained sandstones of the lower Tunbridge Wells Sand Formation. |
| Type Area |
Natural crags of the member are common within the limits of the outcrop but notably at Stonehurst, Ardingly [TQ 344 317]; Balcombe Mill [TQ 317 305]; Chiddingly Wood, West Hoathly [TQ 349 321]; Stone Farm rocks, Saint Hill Green [TQ 381 348]; Redleaf House, Penshurst [TQ 522 455]; Rustall Toad Rock, Tunbridge Wells [TQ 568 395]; Eridge Rocks [TQ 554 357]; Bowles Rocks, Boarstead [TQ 542 330]; The Rocks, Uckfield [TQ 464 217]. See also other sections in the relevant BGS memoirs. |
| Reference(s): |
| Young, B and Lake, R D. 1988. Geology of the country around Brighton and Worthing. Memoir of the British Geological Survey, Sheet 318 and 333 (England and Wales). |
| Gallois, R W and Worssam, B C. 1993. Geology of the country around Horsham. Memoir of the British Geological Survey, Sheet 302 (England and Wales). 130pp. |
| 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). |
| Dines, H G, Buchan, S, Holmes, S C A and Bristow, C R. 1969. Geology of the country around Sevenoaks and Tonbridge. Second edition. Memoir of the Institute of Geological Sciences, Sheet 287 (England and Wales). |
| Gallois, R W. 1965. Horsham (302) Sheet. Summary of Progress of the Geological Survey of Great Britain for 1964. |
| Lake, R D and Thurrell, R G. 1974. The sedimentary sequence of the Wealden Beds in boreholes near Cuckfield, Sussex. Report of the Institute of Geological Sciences, No.74/2. |
| Lake, R D, Young, B, Wood, C J and Mortimore, R N. 1987. Geology of the country around Lewes. Memoir of the British Geological Survey, Sheet 319 (England and Wales). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
