DOLERITE SILL WITH CHILLED MARGIN - Tideswell Dale, Derbyshire

PART OF A DOLERITE SILL WITH CHILLED MARGIN

290 million years old

Tideswell Dale, Derbyshire
  
This specimen of dolerite is from a dolerite sill exposed in a disused quarry on the eastern side of Tideswell Dale. The sill has been injected at a very high temperature into the Carboniferous Limestone in the earliest Permian or late Carboniferous periods.

This piece shows a ‘chilled margin’ which is a fine-grained edge where the molten rock of the sill was in contact with the cool limestone. 

This is a very good example of this phenomenon. It was collected in 1995 and is from an old collection.