The Williamsport Sandstone is a sandstone geologic formation in West Virginia, Virginia, Pennsylvania, and Maryland. the formation includes the Cedar Creek Limestone member. Near Cumberland, Maryland it includes the Cedar Creek Limestone member. It preserves fossils dating back to the Silurian period.
The Warsaw Formation is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian subperiod.
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 Frederick Limestone is a geologic formation in Maryland and Virginia. It preserves fossils dating back to the Cambrian period.
The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period.
The Rockdale Run Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating back to the Ordovician period.
The Choptank Formation is a geologic formation in Virginia and Maryland. It preserves fossils dating from the Miocene epoch of the Neogene period.
The Grainger Formation is a geologic formation in Tennessee, Kentucky, and Virginia. It preserves fossils dating back to the early Mississippian subperiod of the Carboniferous period.
The Whitesburg Formation is a dark limestone with interbedded shales geologic formation in Tennessee and Virginia. It preserves fossils dating back to the Ordovician period.
The Jennings Formation is a geologic formation in Maryland. It preserves fossils dating back to the Devonian period.
The Matawan Formation is a geologic formation in Maryland and New Jersey. It preserves fossils dating back to the Cretaceous period.
The Monmouth Formation is a geologic formation in Prince George's County, Maryland. It preserves fossils dating back to the Cretaceous period.
The Java Formation is a geologic formation in Kentucky, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia. It preserves fossils dating back to the Devonian period. The formation comprises the Pipe Creek Shale, Wiscoy Sandstone Member in New York, and Hanover Shale Member except in Tennessee.
The Tomstown Dolomite or Tomstown Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating to the Cambrian Period.
The Cape May Formation is a geologic formation in New Jersey and Pennsylvania. It preserves fossils.
The Alum Bluff Group is a geologic group in the states of Georgia, Florida, and Alabama. It preserves fossils dating back to the Neogene period.
Yazoo Clay is a clay geologic formation in Alabama, Louisiana, and Mississippi. It was named after a bluff along the Yazoo River at Yazoo City, Mississippi. It contains is a type of clay known as montmorillonite, making it a poor foundation material due to the fact that moisture causes extreme changes in volume. Sand, pyrite, and marl have all been noted in the formation. It preserves fossils from the Eocene, including the prehistoric cetaceans Basilosaurus and Zygorhiza, and the marine snake Pterosphenus. Sharks, rays, eels, and fish have also been found from the formation.
The Weches Formation is a greensand, slay, and shale geologic formation in Louisiana and Eastern Texas. It preserves fossils dating back to the Paleogene period, specifically the Eocene.
The Alamosa Formation is a geologic formation in Colorado. It preserves fossils. The formation was deposited by Lake Alamosa, a paleolake that existed from the Pliocene to the middle Pleistocene.
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