During the Devonian, warm shallow seas covered northwestern New Jersey.
Brachiopods, bryozoans, corals, crinoids, and trilobites are common
fossils found in the Devonian rocks of the upper Delaware River valley
in northwestern Warren and Sussex Counties.
 | North American Paleogeography: Most of North America was covered
by a shallow sea throughout the Devonian, although some small
landmasses were exposed around the continent. On its southern margin
(now the East Coast), the collision with Avalonia
begun in the Late Silurian continued into the Devonian and produced an
extensive chain of mountains. The rivers that drained these mountains
deposited abundant sand and mud over parts of present-day Canada and
the Northeast from Maine to Tennessee. |