Barnt Green Volcanic Formation

Barnt green Volcanic Formation

Age: 488-478 million years (Ordovician, Tremadocian-Arenig)

Overview

Ordovician rocks are restricted to one area in the north of Worcestershire – an inlier (an area of older rocks surrounded by younger rocks) centred on the Lickey Hills. The nature of the rocks suggests a shallow marine sea existed at the time, during which volcanic activity was occurring close by.

Lithology

The Barnt Green Volcanic Formation consists of coarse grained green tuffs, grey sandstones, purple/dark brown grits with some calcite veins and thin bedded siltstones and mudstones, which appear to have been laid down in water and were intruded by a few microdiorite dykes after their deposition. The presence of lower Ordovician microfossils (acritarchs) in sediments within the unit tentatively correlates it to the Ordovician, although there is still some debate as to its precise age.

The outcrop occurs in a small, fault bounded inlier running southwards from Kendal End. There is one large exposure of the unit, which has only recently been identified, revealing the formation at its best for probably the first time ever.

Sites

Lickey Lower Quarry, Worcestershire (no longer exposed)
Small exposure present in SE corner of Barnt Road Quarry, Worcestershire