Paleontology and geology
The Cretaceous sediments of Delaware record a change from terrestrial environments in the Early Cretaceous to shallow-marine environments in the Late Cretaceous. Fossil wood, plant fragments, charcoal, and pollen have been found in terrestrial sediments in northern Delaware and represent the remains of a subtropical lowland forest affected by regular fires. Late Cretaceous marine sediments are present throughout the lower three-quarters of the state, but are only exposed in stream cuts and excavations, the most famous being the Chesapeake and Delaware Canal. Alternation between sandy and muddy formations in this interval records a series of changes in sea level. Marine deposits include fossils of mosasaurs and large sharks, as well as a diverse set of invertebrates, including ammonites, belemnoids, oysters, snails, and echinoids. Fragments of dinosaur and Pteranodon bones have been found in the rocks representing an adjacent coastal plain.