Geology of the Andover area: Concealed strata

This page is part of a category of pages providing a summary of the geology of the Andover district (British Geological Survey Sheet 283), which extends over approximately 600 km2 of north-west Hampshire and a small part of eastern Wiltshire. Links to other pages in this category can be found at the foot of the page. Authors: J Thompson, K A Lee, P M Hopson, A R Farrant, A J Newell, R J Marks, L B Bateson, M A Woods, I P Wilkinson and N J Smith.

There are six deep hydrocarbons boreholes, within or adjacent to the Andover district, which provide evidence of the strata encountered at depth. Figure P807821 shows the location of the boreholes and the Stratal thickness table details the stratal thicknesses within each. Seismic sections show that Ordovician to Carboniferous strata form the basement beneath the area.

Stratal thickness table
Key hydrocarbons boreholes and deeper wells in the Andover district and adjacent areas.

Strata	Kingsclere	Egbury 1	Upper Enham 1	Ham 1	Hurstbourne Tarrant	Carnarvon Arms
Borehole number	SU45NE 1	SU45SW 46	SU35SE 23	SU36SW 1	SU35SE 27	SU45NE 3
Grid reference	49840 58200	44484 52364	36598 50430	33100 62470	36032 53500	45720 59450
Palaeogene	Absent	Absent	Absent	Absent	Absent	124.6
White Chalk Subgroup	Absent	170.6	Absent	Absent	217.6	12.5+
Grey Chalk Subgroup	Absent	68.4	Absent	18.3
Upper Greensand Formation	33.8	70.0	57.7	42.7	62.8
Gault Formation	86.6	41.0	58.7	84.1	55.5
Lower Greensand Group	13.7	10.5	11.3	4.8	10.4
Wealden ‘Group’	178.9	118.5	127.1	11.0+	125.9
Purbeck Group	164.3	43.5	53.8		36.3
Portland Group	43.6	46.0	53.4		50.0
Kimmeridge Clay Formation	284.4	187.5	203.2		218.2
Corallian Group	53.6	58.0	57.5		125.0
Oxford Clay Formation	95.1	117.3	132.7		25.0
Kellaways Formation	9.1	10.5	14.0		14.0
Great Oolite Group	85.0	93.9	108.1		61.0
Inferior Oolite Group	109.4	48.3	75.9		118.3
Lias Group†	360.9+	377.7	495.5		38.4+
Penarth Group		9.3	28.5+
Permo-Triassic		Absent
Ordovician to Carboniferous		29.0+

Notes: †The Lias Group undivided encompasses the old divisions of Lower, Middle and Upper Lias. Modern terminology that can be
applied to the strata encountered in these boreholes is discussed on the Jurassic page.

Location of key deep hydrocarbons boreholes in the Andover district and adjacent areas. P807821.

Additional data in nearby deep wells such as Farley South, Stockbridge, Lockerly and Humbly Grove can be found in Hopson et al. (2007), Booth (2002) and Farrant (2002).