The boundary between the Silurian and the Devonian has not been established internationally. In England the dispute arises over the age of the Downtonian

End_Page 199------------------------

beds which have been regarded by many British geologists as Late Silurian. Recently, they have been placed in the Lower Devonian with the base of the Ludlow Bone Bed marking the contact with the Upper Silurian. In continental Europe, the Gedinnian stage has long been considered the base of the Devonian and its lower part is correlated with the Downtonian of England. Rapidly changing facies and facies fossils around the border of the Old Red Sandstone continent render regional correlation difficult.

In northeastern United States, sedimentation was continuous across the boundary in the type areas and the problem involves the age of Manlius and Keyser limestones. Recently, the upper Keyser and the Manlius have been placed in the Lower Devonian. Poorly fossiliferous Upper Silurian strata make correlation with the type European sections insecure.

Comparison of the Canadian Arctic sections with the type areas of Europe and eastern North America is presently insoluble, due mainly to insufficient detailed information. the boundary is obscured by earth movements of restricted extent resulting in isolated, unfossiliferous sediments that present no bases for regional or local correlation.

End_of_Record - Last_Page 200-------