Middridge Quarry is a Site of Special Scientific Interest

Site of Special Scientific Interest

A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...

 in the Sedgefield district of County Durham

County Durham

County Durham is a ceremonial county and unitary district in north east England. The county town is Durham. The largest settlement in the ceremonial county is the town of Darlington...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It is a disused quarry, situated alongside the railway line between Newton Aycliffe

Newton Aycliffe

Newton Aycliffe is a town in County Durham, England. Founded in 1947 under the New Towns Act of 1946, it is the oldest new town in the north of England.-Geography:...

 and Shildon

Shildon

Shildon is a town in County Durham, in England. It is situated 2 miles to the south east of Bishop Auckland and 11 miles north of Darlington. It is 13 miles away from Durham, 23 miles from Sunderland and 23 miles from Newcastle-upon-Tyne...

, 1 km south of the village of Middridge

Middridge

Middridge is a village in County Durham, England. It is situated east of Shildon and north-west of Newton Aycliffe. The village is situated not far from a quarry that was mined by the people many generations ago...

.

The quarry was excavated in magnesian limestone

Magnesian limestone

Magnesian limestone can refer to:* For the rock made of magnesium carbonate ie Magnesian limestone see dolomite or dolostone* For the traditional name of a specific suite of Permian age rocks in north-east England see Magnesian Limestone...

, the lowest level of which is an exceptionally fossiliferous marl

Marl

Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...

 slate

Slate

Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering...

 which has yielded the richest and most varied Permian flora in the Britain and is the type locality for the pteridosperm, Pseudoctensis middridgensis. Fossils obtained from the quarry have included several species of fish and reptiles, numerous invertebrates and plants, and the site is considered to be of international paleontological importance.