The Age of the Dinosaurs

Seas deepened during the Jurassic period, their legacy being grey mudstone and limestone now found mainly around Antrim coast. They can yield interesting fossils but their most visible contribution has been in promoting instability of overlying rocks. Landslips of various types, both active and stable, are well seen on the Antrim coast road at Minnis, north of Ballygally, and Garron respectively.

Marine conditions were maintained through much of the succeeding Cretaceous. Initially sandstone formed but these were overlain by the visually striking white limestones. Formed from microscopic remains of marine organisms, they record warm, clear sea conditions. The hardness of this chalk has made it resilient to erosion such that our white cliffs in Antrim, unlike those at Dover which are of the same geological age, are standing fast against the action of the sea. Unfortunately however, although this was the age of the dinosaurs, no significant fossils have been found to date.

By the end of the Cretaceous, a land mass broadly recognisable as Ireland, had continued its northward movement to a position similar to southern France today. Weathering of the limestone surface created a karst landscape with sinkholes and caves present. These features are visible today at the top of much of the chalk.