| Monmouth Group | |
| Type: | Group |
| Age: | Late Santonian to late Maastrichtian, |
| Prilithology: | Marl, glauconite |
| Region: | ,,,, |
| Subunits: | See text |
| Underlies: | Rancocas Group |
| Overlies: | Magothy Formation |
| Period: | Late Cretaceous |
The Monmouth Group or Matawan Group is a major Late Cretaceous-aged geologic group in the eastern United States, known from New Jersey, Pennsylvania, New York, Delaware, and Maryland.[1] It comprises a number of geological formations dating from the Santonian to nearly the end of the Maastrichtian, deposited in nearshore environments off the coast of eastern Appalachia, including deltaic and marine ecosystems.[2] It is highly fossiliferous and preserves a diverse array of fossils, including some of the most prominent dinosaur-bearing deposits of eastern North America.
The following formations are included, from youngest to oldest:[3]