Paleontology and geology
During the Cretaceous, northern New Jersey was above sea level. In the south, Cretaceous seas advanced and retreated across the coastal plain numerous times, providing habitats that ranged from terrestrial to deep continental shelf. Dinosaurs and insects were among the many animals living in the humid forests and swamps of New Jersey’s low-lying areas. Fossil leaves and insects in amber have been found in former brick clay pits in the Raritan Bay area. Hadrosaurus foulkii, a duckbilled dinosaur and New Jersey’s state dinosaur, was the most complete dinosaur skeleton found when it was discovered in 1858. The Big Brook locality in Monmouth County is famous among collectors who sift modern streambed sediments for well-preserved marine fossils, including oysters, belemnites, and sharks’ teeth. Although sharks were common, giant marine reptiles called mosasaurs ruled the Cretaceous seas. This map indicates a band of Cretaceous rocks extending from central eastern New Jersey to the southwest.