The BGS Lexicon of Named Rock Units — Result Details

Grange Hill Sand Formation

Computer Code: GRHS Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Sand dominated sequence (Hempriggs Sand Member), capped by red brown sandy silt (Milton Hill Silt Member) and locally overlying a sandy silty matrix-supported diamicton (East Grange Till Member) or contorted silt and sand. The sand is typically medium- to fine-grained pale yellow to pale orange in colour, in cross-stratified units.
Definition of Lower Boundary: Not seen; mapping indicates erosional contact on Till (Finglack Till Formation), Glaciofluvial outwash of the Main Late Devensian Glaciation, laid down prior to the Elgin Oscillation and Old Red Sandstone bedrock.
Definition of Upper Boundary: Generally the ground surface, but locally unconformably overlain by sandy Late Devensian Raised Beach Deposits or sandy Holocene Raised Marine Deposits.
Thickness: Composite sections indicate a typical thickness >10m; the land forms indicate a thickness of >20m locally. (see type localities of component members of the Formation.
Geographical Limits: Discontinuous curvilinear ridge that extends northwestwards from 2.6 km east of the centre of Forres, a distance of 8.5km to Easter Coltfield [NJ 1202 6440]. Isolated undulating ridges rising to between 45m and 55m AOD are also present east of Forres. All known exposures lie within the SW corner of the Elgin Sheet (Scotland Sheet 95).
Parent Unit: Banffshire Coast and Caithness Glacigenic Subgroup (BCD)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Not Formally Named Previously
Partial Type Section  Sand Pit on Kinloss Golf Course, 1.06km NNW of Spot Height on top of Grange Hill. Cross-bedded pale yellow medium- to fine-grained micaceous sand with sparse partings of pale brown silt; some contorted laminations and soft sediment deformation ('flame structures'). Low-angle tabular foresets; cosets fine upwards suggesting waining turbidity flows. Some ripple drift lamination and a thin bed ( c.10-12 cm thick) of sandy till in upper part of sand unit. Up to 4.2m of section exposed. Tabular cosets dip at a shallow angle (16 degrees) towards NNE 022 degrees suggesting ice front lay towards the SW at the time of deposition. Low angle faulting gives possible evidence of ice "push" towards the north east. 
Reference Section  Type section of the East Grange Till Member; disused clay pit, 560m north of East Grange farm. Red-brown sandy diamicton, at least 2.5m thick, containing dropstone cobbles deforming laminated lenses of silty fine white sand. For further detail see Lexicon entry for East Grange Till Member. 
Partial Type Section  Former section in disused sand pit, 215m SE of Upper Hempriggs farm; from Elgin Memoir and original notes on field map. Brown Till, 0.3-0.7m thick, overlying sand and silt, 9.1m thick; with gravel lenses and faults lined with indurated sandy clay; 'balls' of rock flour occur within the sand. Cross- bedding within the sand dips towards the north east. Sand dominated sequence with faulting and ball and pillow structures, deposited from an ice margin to the south west. 
Partial Type Section  Auger hole to 1.2m depth (unbottomed). Red-brown micaceous sandy silt. Sparse scattered cobbles and boulders on ground surface. This unit is also exposed in degraded sections on the track to the top of Grange Hill, 83m NW of the auger hole. These suggest that the unit may reach up to c. 5m in thickness. 
Reference Section  Degraded sections up to c.3m high in disused sand pit, c.190m south of Spot Height on top of Grange Hill. Sequence coarsens downwards from fine-grained, red-brown silty micaceous sand into medium-grained pale yellow sand. This pit is close to the base of the Grange Hill feature and at least 15m below the base of the Milton Hill Silt Member which caps the hill. This suggests that the sand unit is c.15-20m thick. 
Geology of the Elgin District Geological Survey Scotland Memoir Sheet 95 (Peacock et al; 1968). 
1:50K maps on which the lithostratigraphical unit is found, and map code used: