Paleontology and geology
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.