OR/14/029 Modelled surfaces/volumes

Geological units modelled

In total, 64 superficial and artificial geological units were modelled (including mass movement deposits). Table 1 lists the units in broad stratigraphic order together with the BGS stratigraphic lexicon code for each (see https://www.bgs.ac.uk/lexicon/) and lithology. Standard BGS map colours have been used for all superficial units in the model (Figure 2). These should be referred to when viewing images of the model in this report. Note that the Head and Clay-with-flints deposits are known to be polycyclic, and in the case of the latter, its formation is likely to have started as early as the Pliocene

Inferred age	LEXICON CODE	Full name	Lithology
Holocene deposits and artificially modified ground	slip	Landslide deposits	Mass movement deposits; variable composition, dependent on the nature of the upslope material
	wgr	Worked Ground	Artificially lowered area, or void, through man-made excavation, e.g. a gravel pit
	mgr	Made Ground	Artificially raised areas, variable composition
	wmgr	Worked & Made Ground	Area of artificial cut and fill, e.g. a backfilled quarry, variable composition
	ddgr	Disturbed Ground	Area of disturbance associated with surface or near-surface collapse
	lsgr	Landscaped Ground	Extensively remodelled areas where it is difficult to delineate zones of Made, Worked or Disturbed Ground. Variable composition
	peat	Peat	Humic deposits, consisting of wet dark brown partially decomposed vegetation
	tufa	Tufa	Inorganic calcium carbonate or sinter deposited at or near springs and seepages
	alv	Alluvium	Fluvial deposits of modern flood plains, consisting of clay, silt, sand and peat
Late Anglian – Devensian glacigenic deposits and river terraces, various catchments	rtdu	River Terrace Deposits (undifferentiated)	Sand and gravel deposits directly beneath alluvium
	head	Head	Solifluction or hillwash deposit, composition dependent on source material. Usually gravelly sandy clay
	cwf	Clay-with-flints Formation	Residual deposit formed through weathering of a previous cover of Palaeogene deposits, and through dissolution of Chalk bedrock. Typically orange-brown and red-brown sandy clay with flint nodules and pebbles
	rtdo	Pleistocene River Terrace Deposits (unclassified)	Exposed river terrace deposits (not below alluvium). Composed of sand and gravel
	igd	Interglacial Deposits	Composed of silty clay
	lasi	Langley Silt Member	Varies from silt to clay, usually yellow brown and massively bedded
	shgr	Shepperton Gravel Member	Gravel with clay and sand
	no1a	Northmoor Sand and Gravel Member	Sand and gravel
	no1b
	no
	rosi	Roding Silt Member	Varies from silt to clay, usually yellow brown and massively bedded
	esi	Enfield Silt Member	Varies from silt to clay, usually yellow brown and massively bedded
	cfsi	Crayford Silt Member	Varies from silt to clay, usually yellow brown, often contains wind-blown sand
	kpgr	Kempton Park Gravel Member	Sand and gravel, with local lenses of silt, clay or peat
	bggr	Beenham Grange Gravel Member	Sandy clayey gravel
	sura	Summertown-Radley Sand and Gravel Member	Sand and gravel
	rtd2	2nd river terrace deposit	Sand and gravel
	ilsi	Ilford Silt Member	Sandy clay and silt
	tpgr	Taplow Gravel Member	Sand and gravel, locally with lenses of silt, clay or peat
	thgr	Thatcham Gravel Member	Sandy clayey gravel
	wv	Wolvercote Sand and Gravel Member	Sand and gravel
	rtd3	3rd river terrace	Sand and gravel
	hagr	Hackney Gravel Member	Sand and gravel, locally with lenses of silt, clay or peat
	lhgr	Lynch Hill Gravel Member	Sand and gravel, locally with lenses of silt, clay or peat
	han	Hanborough Gravel Member	Sand and gravel
	rtd4	4th river terrace deposits	Sand and gravel
	dasi	Dartford Silt Member	Varies from silt to clay, usually yellow brown, often contains wind-blown sand
	figr	Finsbury Gravel Member	Sand and gravel, locally with lenses of silt, clay or peat
	bht	Boyn Hill Gravel Member	Sand and gravel with possible lenses of silt, clay or peat
	rtd5	5th river terrace deposits	Sand and gravel
		bpgr	Black Park Gravel Member	Sand and gravel with possible lenses of silt, clay or peat
	rtd6	6th river terrace deposit	Sand and gravel
	sigr	Silchester Gravel Member	Clayey, sandy gravel