Wealden Sandstones and Clays – Lower Cretaceous (lead authors JT &WGT)

System	Stage	Ma	Group	Formation		Use
Lower Cretaceous	Aptian	~125	Lower Greensand			Ferruginous sandstone
			Wealden	Vectis
	Barremian	~129.4
					Course Quartz Grit
	Hauterivian	~132.9		Wessex
	Valanginian	~139.8
	Berriasian
			Purbeck	Durlston

The Wealden Group is a multi-coloured sequence of sands, silts and clays deposited in lakes, rivers and deltas 146-125 million years ago, overlying the Purbeck Group. 

These strata outcrop in the area between Swanage (thickest) and Durdle Door, bounded to the north by the Chalk ridge and to the south by the Purbeck hills.  They are best exposed at Swanage, Worbarrow Bay and Lulworth Cove.  

Coarse Wealden sandstone Lulworth Cove. Photo: WGT

There are also occasional concretions within the clays, of similar colour, but smoother in texture.  Both these rock types have been used in field walls and the foundations of cottages in the vale.  Near Swanage, Wealden clay is used for brickmaking.  

A pebble of the ironstone from the clays at Worbarrow Bay, Loupe photo, 2 x 2 cm. Image : JT

Brick pit in Wealden clays near Swanage. Photo: WGT

Ferruginous Wealden sandstone Lulworth Cove. Photo: WGT

 Some coarse pebbly ”gritty” sandstones form ridges in the vale, such as Windmill Knap (near Swanage) and Corfe Common where the “Coarse Quartz Grit” was once quarried.  This is a hard ferruginous sandstone, of a purple to blood-red colour, containing minerals derived from erosion of the Dartmoor granite. (see image below)

Wealden sandstone in a building near Swanage. Photo: WGT

Wealden Bricks. Photo: WGT

Text JT & GT   Mar 2017