portlandian

Updated: July 19, 2025

But some fragments of them occur beneath the Neocomian or Speeton Clay on the coast of Yorkshire, containing many more fossils common to the Portlandian of the Continent than does the same formation in Dorsetshire. The Kimmeridge Clay consists, in great part, of a bituminous shale, sometimes forming an impure coal, several hundred feet in thickness.

Sir Charles Lyell - The Student's Elements of Geology