Geology Site Account

Site name: Freewood Lane Boulder, Elmdon

Grid reference: TL 4638 3912

Brief description of site:

At the entrance to Freewood Lane is a glacial erratic boulder (80 x 60 x 50 centimetres in size). It is unusual as it consists of Spilsby Sandstone and originates in Lincolnshire. It was brought here by the great Anglian Ice Sheet when it covered almost the whole of Britain 450,000 years ago.

The Spilsby Sandstone Formation is found at the junction of the Jurassic and Cretaceous rocks in the southern part of Lincolnshire. It is mainly sandy with some silt layers. Some is very friable, but it also contains irregular lumps hardened by a calcareous cement. It is these lumps which would have survived transport in the ice sheet moving south to Essex and were dumped here when the ice melted. They contain distinctive ammonites and casts of boring bivalves.