Britannica Sources used in this answer

How did geologists connect the Old Red Sandstone to Devonian marine rocks?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Devonian paleogeography — Devonian Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Devonian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

Geologists connected the continental Old Red Sandstone to Devonian marine rocks primarily through the study of fossils and stratigraphic positioning.1

The initial breakthrough occurred in 1839 when William Lonsdale observed that fossil corals from Devon, England, appeared intermediate in type between those found in the underlying Silurian System and the overlying Carboniferous System. This suggested that these marine strata were the chronological equivalents of the terrestrial Old Red Sandstone deposits already identified in Wales and Scotland.1

This correlation was later confirmed through field observations by geologists Adam Sedgwick and Roderick Murchison, who visited Germany to verify the sequence. Further evidence was provided when Murchison discovered an intercalation—a layer of one rock type embedded within another—containing both Devonian marine fossils and Old Red Sandstone fish near St. Petersburg, Russia. Today, researchers continue to refine these correlations using fish and plant spores to link continental deposits to established marine faunal successions.12