The BGS Lexicon of Named Rock Units — Result Details

Longman Gravel Formation

Computer Code: LNGR Preferred Map Code: LG
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: A cobble gravel with a little sand and clay, and sparse shell fragments.
Definition of Lower Boundary: An undulating, channelled and erosional unconformable contact with the underlying clayey silt and fine-grained sand of the Kessock Bridge Silt Formation.
Definition of Upper Boundary: The present ground surface or a sharp, generally planar, erosional and unconformable contact with the overlying Flandrian raised beach deposits.
Thickness: About 30m
Geographical Limits: The area around the Inner Moray Firth and Beauly Firth, Inverness. Sheet S87W (Fortrose).
Parent Unit: Northern Highlands And Argyll Catchments Subgroup (NHC)
Previous Name(s): Low Level Gravel Of Inverness (-3535)
Alternative Name(s): Longman Terrace
Stratotypes:
Type Section  Site investigation boreholes (570 L3-11 and M1-6) drilled along the line of the Kessock Bridge, Inverness,and registered by BGS as: NH64SW/16839 & NH64NW/17718 suffix 1 to 7, plus a second set which are currently misplaced. Peacock, J D and Wilkinson, IP in Merrit et al. 1995. 
Reference(s):
Merrit, J W, Auton, C A, and Firth. C R. 1995. Ice-proximal glaciomarine sedimentation and sea-level change in the Inverness area, Scotland: A review of the deglaciation of a major ice stream of the British Late Devensian ice sheet. Quaternary Science Reviews, Vol.14, 289-329. 
Sissons, J B. 1981. Late glacial marine erosion and a jokulhaup deposit in the Beauly Firth. Scottish Journal of Geology, Vol.17, 7-19. 
Peacock, J D. 1977. Subsurface deposits of Inverness and the Inner Cromarty Firth. 103-104 in Gill, G (editor), Moray Firth Area Geological Studues. [Inverness Field Club]. 
Fletcher, T P et al. 1996. Geology of the Fortrose and eastern Inverness district. Memoir of the British Geological Survey, Sheet 84W (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S084