| Computer Code: |
LHF |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Devensian Stage (QD)
— Devensian Stage (QD) |
| Lithological Description: |
Characteristically reddish yellow very silty fine to medium sand with beds of silt or sand. Very sparse fine gravel and limited bands of fine dark detrital material are noted. Lawns House Farm Sand Member is commonly water saturated, supporting a weak hydrostatic head, and prone to "running". |
| Definition of Lower Boundary: |
Nowhere exposed; details unknown. |
| Definition of Upper Boundary: |
Sharp to gradational upwards transition (over several cms) via finely interbedded silty sand and clay into clays of the Thorganby Clay Member. |
| Thickness: |
Estimated to be approximately 2.5m maximum. |
| Geographical Limits: |
This unit has a lobate form extending south from the Escrick Moraine for up to 15km, thinning gradually from a maximum of about 2.5m in the north. It is thought to extend across from River Ouse in the west to the River Foulness in the east. Its northern limit is believed to be the Escrick Moraine, and the southern extent reaches at least as far as Selby. |
| Parent Unit: |
Hemingbrough Glaciolacustrine Formation (HEM)
|
| Previous Name(s): |
Silt and Clay of the 25 Foot Drift of the Vale of York [Obsolete Name and Code: Use LHF]
(-1027)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Partial Type Section |
Temporary exposure on the southern bank of a partially exposed drainage ditch, approximately 1400m southsouthwest of Thorganby and 750m northeast of Lawns House Farm. About 1m of vertical exposure shows reddish yellow very silty fine sand. Corresponding auger hole traversesprove a very sharp upper contact with clays of the Thorganby Clay Member. |
| Reference(s): |
| 1:50k geological map of Selby (Sheet 71) (in prep): Selby Sheet Explantion (in prep). |
| British Geological Survey. 1973. Sheet 71 Selby solid and drift/compiled and drawn in Leeds Office of the Institute of Geological Sciences - Solid and drift ed. Provisional ed. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
