The BGS Lexicon of Named Rock Units — Result Details

Thorpe Sand And Gravel Member

Computer Code: THSG Preferred Map Code: notEntered
Status Code: Full
Age range: Pleistocene Epoch (QP) — Pleistocene Epoch (QP)
Lithological Description: Predominantly cold-phase sands and gravels that underlie the Thorpe or Second Terrace of the River Bain. Dominated by clasts of flint with up to 50% chalk (though decalcified near ground surface) and a smaller proportion of Upper Jurassic and Lower Cretaceous lithologies plus minor exotics, notably Carboniferous sandstone and "Bunter" quartz/quartzite pebbles (mostly derived from Anglian tills). It forms a rather degraded terrace surface typically some 3 to 4m above the modern alluvial floodplain, and c.2m higher that the adjacent Castle Terrace, though deposits extend beneath the level of the latter. Sections show intraformational and epigenitic ice wedge casts, and upper part locally incorporates a rubified palaeosol (Hykeham Soil; Ipswichian). Locally includes cold-phase organic silts and peats, but channel-filling organic silts at the base (Kirkby Bed) yield a temperate flora and fauna assigned to MIS 7. Correlated with the Southrey and Balderton Sand and Gravel members and Egginton Sand and Gravel Member (all in the Trent Valley Formation).
Definition of Lower Boundary: Unconformable, commonly channelled base, resting on Anglian Wragby Till in the Type Area but possibly locally on Upper Jurassic mudstone bedrock if present elsewhere.
Definition of Upper Boundary: Ground surface or (locally) overlain by the Castle Sand and Gravel Member.
Thickness: 0 to c.8m
Geographical Limits: Bain valley; upstream limits unknown but possibly represented in the Upper Bain. To the northwest, merges with correlative Southrey Sand and Gravel in the Witham valley.
Parent Unit: Bain Valley Formation (BAINV)
Previous Name(s): Tattershall-Kirkby Terrace Deposits (-3275)
Southrey Terrace Deposits (-110)
Second Terrace Deposits (-4908)
Thorpe Member (-568)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Tattershall Thorpe Gravel Pit. Brandon and Sumbler, 1999, p.14. 
Reference(s):
Girling, M A. 1977. Tattershall and Kirkby-on-Bain. 19-21 in Catt, J A. Yorkshire and Lincolnshire guidebook for excursion C7, Xth INQUA Congress. 
Jackson, I and Issaias, M D. 1982. The sand and gravel resources of the country around Coningsby, Lincolnshire: description of 1:25 000 resource sheet TF25. Mineral Assessment Report, Institute of Geological Sciences, No.128. 
Power, G and Wild, J B L. 1982. The sand and gravel resources of the country around south of Horncastle, Lincolnshire. Description of 1:25 000 resource sheet TF26. Mineral Assessment Report, Institute of Geological Sciences, No.108. 
Rackham, D J. 1981. Mid-Devensian mammals in Britain. Unpublished M.Sc. Thesis. University of Birmingham. 
Straw, A. 1958. The glacial sequence in Lincolnshire. East Midlands Geographer, Vol.2, 29-40. 
Brandon A and Sumbler, M G. 1991. The Balderton Sand and Gravel: pre-Ipswichian cold stage fluvial deposits near Lincoln, England. Journal of Quaternary Science, Vol.6. 117-138. 
Bryant, I D. 1983. Periglacial river systems: ancient and modern. Unpublished PhD Thesis, University of Reading. 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Brandon, A and Sumbler M G. Unpublished manuscript. 
Rackham, D J. 1978. Evidence for changing vertebrate communities in the Middle Devensian. Quaternary Newsletter, No.25. 1-3. 
Bryant, I D. 1983b. Facies sequences associated with some braided river deposits of late Pleistocene age from southern Britain. 267-275 in Collinson, J D and Lewis, J (editors), Modern and ancient fluvial systems. Special Publication of the International Association of Sedimentologists, No.6. 
Girling, M A. 1980. Late Pleistocene insect faunas from two sites. Unpublished PhD Thesis, University of Birmingham. 
Holyoak, D T and Preece, R C. 1985. Late Pleistocene interglacial deposits at Tattershall, Lincolnshire. Philosophical Transactions of the Royal Society of London, Vol. B311, 193-236. 
Lister, A M and Brandon, A. 1991. A pre-Ipswichian cold stage mammalian fauna from the Balderton Sand and Gravel, Lincolnshire, England. Journal of Quaternary Science, 6, 139-157. 
Perkins, N K and Rhodes, E J. 1994. Optical dating of fluvial sediments from Tattershall, UK. Quaternary Science Reviews, Vol.13. 517-520. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E103 E115