It extended from the present Hudson River westward across New York State and into Ohio and Indiana. It also extended southward into West Virginia and Kentucky. This sea was home to many invertebrates, especially coral, along with many jawless, shark-like fish. The corals in the Catskill Sea built many reefs in different areas. Along with corals there were many species of brachiopods and pelecypods, which were shelled organisms similar to modern clams and scallops.
Arrows show inferred Late Devonian river systems.
Adapted and redrawn from Isachsen et al. This collision produced the Acadian Mountains, which rose in present-day New England and the Canadian Maritime Provinces. During and after the collision, erosion gradually stripped sediment from the Acadian Mountains. Streams and rivers carried huge quantities of sediment westward to the Catskill Sea. All this occurred throughout the Middle and Late Devonian.