Geology of the Andover area: Concealed strata - Triassic
| 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.
Triassic rocks are absent in the east of the district but are present in the Upper Enham 1 Borehole and continue to thicken westwards in seismic sections to a total thickness of approximately 520 m at the western limit of the district.
Sherwood Sandstone Group (SSG)
The Sherwood Sandstone Group consists of red, yellow and brown sandstone that is pebbly in places along with subordinate red mudstone and siltstone. It is estimated to be between 0 and 230 m thick in this district. The upper boundary of this unit is gradational into the Mercia Mudstone Group above.
Mercia Mudstone Group (MMG)
The Mercia Mudstone Group consists of dominantly red, less commonly green-grey, mudstones and subordinate siltstones; they are unlikely to be thick enough to contain halite-bearing units. Thin beds of gypsum or anhydrite are widespread and some sandstones may also be present. It is estimated to be between 0 and 270 m thick in this district.
Penarth Group (PnG)
The Penarth Group consists of grey to black mudstones with subordinate limestones and sandstones; the group is predominantly marine in origin. It is estimated to be between 10 and 20 m thick in this district.