This article contains a list of fossil-bearing stratigraphic units in the state of Delaware, U.S.
| Group or Formation | Period | Notes |
|---|---|---|
| Chesapeake Group/Calvert Formation | Neogene | |
| Crosswicks Clay | Cretaceous | |
| Englishtown Formation | Cretaceous | |
| Marshalltown Formation | Cretaceous | |
| Matawan Formation | Cretaceous | |
| Merchantville Formation | Cretaceous | |
| Mount Laurel Formation | Cretaceous | |
The Chesapeake Group is a geologic group in Maryland, Virginia, Delaware, and North Carolina. It preserves mainly marine fossils dating back to the Miocene and Pliocene epochs of the Neogene period. This group contains one of the best studied fossil record of Neogene oceans in the world. Professional Paleontologists and amateur fossil hunters alike collect from this group intensely. The Calvert Cliffs stretch the length of Calvert County, Maryland and provide the best continuous stretch of the Calvert, Choptank, and St. Marys Formations. Ward (1985) recommended including the Old Church Formation in this group.
The Potomac Group is a geologic group in Delaware, Maryland, New Jersey, and Virginia. It preserves fossils dating back to the Cretaceous period. An indeterminate tyrannosauroid and Priconodon crassus, a nodosaurid, are known from indeterminate sediments belonging to the Potomac Group. The Potomac Group was initially believed to have been Late Jurassic in age by Othniel Charles Marsh but later studies, such as Clark (1897), have found that the Potomac Group is in fact Early-Late Cretaceous (Aptian-Turonian) in age.
The Patapsco Formation is a geologic formation of varigated clays, sandy clays, and sand in Virginia, the District of Columbia, Maryland, Delaware, Pennsylvania, and in the subsurface of New Jersey. It preserves fossils such as plants and molluscs dating back to the Cretaceous period.
The Delaware River Formation is a geologic formation in Pennsylvania and New York (state). It preserves fossils dating back to the Devonian period.
The Crosswicks Clay is a geologic formation in Delaware. It preserves fossils dating back to the Cretaceous period.
The Englishtown Formation is a geologic formation in Delaware. It preserves fossils dating back to the Cretaceous period.
The Delaware River Flags is a geologic formation in New York. It preserves fossils dating back to the Devonian period.
The Delaware Mountain Formation is a geologic formation in the Delaware Mountains of Texas. It preserves fossils dating back to the Permian period.
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