In the Early Silurian, during an episode of uplift and mountain building, streams flowed
northwestward across northern New Jersey, depositing thick sequences of
river deposits ranging from quartz pebble conglomerates to fine
mudstones. Following this uplift, the sea moved in and out over
northwestern New Jersey for some time. Fragments of eurypterids (“sea
scorpions”) and traces of trilobites have been found in rocks between
terrestrial sediments. In the Delaware Water Gap area, fossils of
ostracoderms (early fish) have also been found. Shallow seas returned to
New Jersey during the Late Silurian, as evidenced by fossils of a
diverse marine fauna including, corals, crinoids, brachiopods,
bryozoans, and trilobites. This map indicates an exposure of Silurian
rocks in northwestern New Jersey.
 Silurian and Devonian Rocks in Green Pond Outlier |
 | North American Paleogeography: A shallow sea covered much of
North America during the Silurian, except for its southern margin (now
the East Coast), which was being uplifted. The uplift began as a collision with an island arc in the Ordovician and developed into a collision with the continent of Avalonia
by the end of the Silurian. In the shallow sea, limestone's, shale's, and
sandstones were deposited, and many large reefs developed. |