Blisworth Limestone Formation facts for kids

Quick facts for kids Blisworth Limestone Formation Stratigraphic range: Bathonian PreЄ Є O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Great Oolite Group
Underlies	Blisworth Clay Formation
Overlies	Rutland Formation
Thickness	up to 12 metres (40 ft)
Lithology
Primary	Limestone
Other	Marl, Mudstone
Location
Region	Europe
Country	UK
Extent	Northamptonshire, Lincolnshire
Type section
Named for	Blisworth
Location	Blisworth Rectory Farm Quarry
Thickness at type section	6-7 m

The Blisworth Limestone Formation is a type of rock (a geological formation) made mostly of limestone. This rock was formed a very long time ago, during the Middle Jurassic period, specifically in a time called the Bathonian stage. You can find it along the Jurassic ridge, which stretches north and south through England.

This limestone was laid down in the shallow parts of the ancient Jurassic sea. It is part of a larger group of rocks known as the Great Oolite Group. In the past, it was also called the Great Oolite Limestone or the White Limestone.

How This Rock Formed

The Blisworth Limestone sits on top of older rock layers called the Upper Estuarine Series. These older layers formed near the coast, where rivers flowed from a landmass known as the London-Brabant Island.

Later, the land slowly sank a little, and the area became slightly further offshore. In the warm, shallow sea, some of the water evaporated. This caused dissolved calcium carbonate (CaCO₃), which is a mineral, to turn into solid particles. These particles formed tiny, round spheres, like fish eggs. This type of rock is called an oölite. This natural process still happens today in places like the seas around Bahamas.

Many marine shells, especially oyster shells, are also found in this limestone. After the limestone formed, the area became less deeply submerged. This led to the Blisworth Clay being deposited on top, which formed in slightly salty (brackish) water.

The rock layer is called Blisworth Limestone because it was first studied in Blisworth, a village in Northamptonshire. This happened when the Blisworth Tunnel was being dug for what is now called the Grand Union Canal. The tunnel was finally opened in 1805.

Where It Is Found

The Blisworth Limestone is generally thin but spread widely across eastern England. It gets thicker as you go south from north Lincolnshire or west from Norfolk.

For example, near King's Lynn, it is a shelly oolitic limestone, about 1 to 2 meters (3 to 6 feet) thick. Around Towcester, it can be as thick as 9 meters (30 feet). You can see it exposed at the surface around the valleys of the East and West Glen rivers in Lincolnshire.

What It Is Used For

Blisworth Limestone is used as a building material, especially for making stone blocks. A famous example is Lilford Hall in Northamptonshire, which was built using Blisworth limestone.