Poole Basin is a geological formation that forms the western part of the much larger Hampshire Basin from which it is separated by the River Avon.

Geology

The rim and bed of the basin are formed by chalk, within which lie the Tertiary sands and clays underlying the

Dorset Heaths The Dorset Heaths form an important area of heathland within the Poole Basin in southern England. Much of the area is protected. Extent According to Natural England, who have designated the Dorset Heaths as National Character Area 135, th ...

. The most extensive deposits here are those of the

Poole Formation Poole () is a large coastal town and seaport in Dorset, on the south coast of England. The town is east of Dorchester and adjoins Bournemouth to the east. Since 1 April 2019, the local authority is Bournemouth, Christchurch and Poole Council ...

or Bagshot Beds. At one time the whole area was almost all heathland lying on acidic soils. Between the chalk perimeter and the central heaths is a belt where the Reading Beds and London Clays surface, giving rise to richer, albeit still acidic, soils. Deposits of plateau and valley

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

s overlie the sands of the Poole Formation, but their soils are likewise poor and acidic. Erosive forces have resulted in an undulating landscape with considerable local variation from narrow, steep-sided valleys and escarpments to areas of flat terrain. The highest point is

Creech Barrow Hill Creech Barrow Hill is a steep, conical hill, Ordnance Survey 1:50,000 ''Landranger'' series, no. 195. (one source 637 feet) high, near the coast of Dorset, England, and the highest point of the Dorset Heaths. It has been described as "one of D ...

(193 m), Ordnance Survey 1:50,000 ''Landranger'' series, no. 195. the highest Tertiary hill in England, capped with Eocene limestone.''The nature conservation interest of the Natural Area''
at www.naturalareas.naturalengland.org.uk. Accessed on 4 Sep 2013

References

{{coord, 50.7, -1.9, display=title Geology of Dorset