The BGS Lexicon of Named Rock Units — Result Details

Letchworth Gravels Formation

Computer Code: LTH Preferred Map Code: LTH
Status Code: Full
Age range: Pleistocene Epoch (QP) — Pleistocene Epoch (QP)
Lithological Description: Pebbly sand and sandy gravel with a high proportion (commonly 50% or more) of rounded quartzose pebbles (quartz, quartzite and sandstone).Quartzose gravel and sand - [Generic description: 1:50 k map margins].
Definition of Lower Boundary: Unconformable on Lower Chalk.
Definition of Upper Boundary: Mostly found at surface. Overlain in part by (Anglian) chalky till.
Thickness: 3.55m proven in borehole TL23NW/113 (TL 2048 3540). May be up to 5m elsewhere.
Geographical Limits: Capping hill top above c.65m OD around Fairfield Hospital, near Letchworth, with smaller spreads along the Pix Brook and to the southwest of Lower Wilbury Farm. Possibly underlying till-covered ground, south of the Hospital.
Parent Unit: Dunwich Group (DUNW)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Reference Section  (Hand-Auger Hole) TL23NW/113. 100m northeast of church at Fairfield Hospital. 
Type Area  Hill top at Fairfield Hospital, particularly open farmland to north. 
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used: