Patapsco Formation

{{Short description|Fossil-rich geologic formation on the East Coast of the United States}}

{{Infobox rockunit

| name = Patapsco Formation

| image = Patapsco Formation.png

| caption = Outcrop of the Patapsco Formation at Reynold's Mine, Anne Arundel County, Maryland showing the Arundel Formation overlain by the Patapsco Formation

| type = Formation

| age = {{fossilrange|Albian|Cenomanian}}

| period = Cenomanian

| prilithology = clay, sand

| otherlithology = silt

| namedfor = Patapsco River

| namedby = William Bullock Clark (1897){{Cite report|last=Clark|first=W.B.|year=1897|title=Outline of present knowledge of the physical features of Maryland|publisher=Maryland Geological Survey|series=Volume Series|volume=1|pages=172-188|url=https://ngmdb.usgs.gov/Prodesc/proddesc_90375.htm}}

| region = Virginia, Maryland

| country = United States

| coordinates =

| unitof = Potomac Group

| subunits =

| underlies = Raritan Formation

| overlies = Arundel Formation

| thickness = {{Convert|200|ft|m|-1}}

| extent =

| area =

| map =

| map_caption =

}}

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.{{cite journal |last1=Richards |first1=Horace G. |last2=Olmstead |first2=F. H. |last3=Ruhle |first3=James L. |title=Generalized structure contour maps of the New Jersey coastal plain |journal=New Jersey Geological Survey Reports |date=1962 |volume=4 |page=38 |url=https://pubs.usgs.gov/unnumbered/70095376/report.pdf |accessdate=28 June 2018}} It preserves fossils such as plants and molluscs dating back to the Cretaceous period.