The BGS Lexicon of Named Rock Units — Result Details

Elvington Glaciolacustrine Formation

Computer Code: ELV Preferred Map Code: ELV
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Firm to stiff, rarely soft, mottled reddish brown (5YR 4/3) and grey (GLEY 2 3/1) thinly laminated clay. Sporadically interlaminated with silt and fine reddish brown sand. Commonly fissured. Gypsum, in the form of opaque, tabular selenite is found locally within the laminated clay below a depth of 2.5m. Crystal size is typically 15 to 35mm along the longest axis.
Definition of Lower Boundary: Not observed. In most places the Elvington Glaciolacustrine Formation will overlie tills of the Vale of York Formation as proved in borehole SE64NE/10, where 4.6m of soft grey brown clay is recorded resting on "brown boulder clay" (glacial till).
Definition of Upper Boundary: An outcrop overlain by aeolian or fluvial sand or clayey sand. The contact is sharp where proven in auger bores.
Thickness: Minimum thickness of 4.2m proved in borehole (SE64NE/17)(SE6838 4634) but generally exceeds 5m in thickness. 4.6m proved in borehole SE64NE/10.
Geographical Limits: The Elvington Glaciolacustrine Formation is constrained between the York Moraine Member to the north (between York in the west and Sand Hutton in the east) and the Escrick Moraine Member to the south (from Stillingfleet in the west to Sutton in the east. It extends as far west as Copmanthorpe and as far east as Sutton Upon Derwent.
Parent Unit: North Pennine Glacigenic Subgroup (NPEG)
Previous Name(s): Elvington Glacial Lake Formation (-2783)
Silts And Clays Of The Vale Of York (-2784)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Borehole SE64NE/16 (SE6874 4683), 1500m southwest of Elvington. The borehole shows a 5m section.0.5 - 2.5m firm to stiff brown clay with thin silt lenses; 2.5 - 4.4m firm brown laminated clay with interlaminated silt; 4.4 - 5.0m soft to firm brown laminated clay with interlaminated silt and sand. The base of the Formation was not penetrated. 
Reference Section  Borehole SE64NE/10 (SE6830, 4620) in what is now a clay pit, proving the Elvington Glaciolacustrine Formation to be locally 4.6m thick resting on glacial till (brown boulder clay). 
Reference(s):
1:50k geological map of Selby (Sheet 71) (in prep): Selby Sheet Explantion (in prep). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E071