Geology of the Andover area: Concealed strata - Permian

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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.

Permian strata are absent from wells but have been interpreted from seismic sections to be present in the west. The strata, as described in the neighbouring Devizes district explanation (Booth et al., 2011)[1], comprise interbedded, red, micaceous mudstone and siltstone with rare thin sandstone interbeds. The strata are displayed as an undivided Permo-Triassic unit on the cross-sections on the Andover 50k map.

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.

References

  1. Booth, K A. 2001. Geology of the Wherwell–Bullington district, Hampshire. British Geological Survey Technical Report, WA/01/08.

Geology of the Andover area — contents