Formations beginning with O
101 names, each with a page of its own for the fossils recorded from it. The list is what this site has looked up and cached, not every formation the record holds.
- Oak Grove
- Oak Orchard
- Oakville
- Oatka
- Obayla
- Ober Süßwassermolasse
- Oberrhaet
- Obotanhondi
- Obourg
- Obukhovo
- Ocala
- Ocala limestone
- Ocala Limestone
- Ocieseki Sandstone
- Ocozocoautla
- Odins Fjord
- Odukpani
- Oehrli
- Offley Island
- Ogallala
- Ogof Hen
- Ogon'or
- Ohesaare
- Ohineruru
- Ohio Shale
- Ohle
- Õhne
- Oi-Muran Reef Massif
- Oiching
- Oil Creek
- Ojinaga
- Ojo Alamo
- Okarahia Sandstone
- Okeechobee
- Okhonchevayamskaya
- Okinoshima
- Ol'chan
- Ola
- Öland C
- Olazagutia
- Olcese
- Olcott
- Old Bank
- Old Church
- Old Pera
- Oldman
- Olduvai
- Olentangy Shale
- Oler
- Olesa-Les Fonts alluvial system
- Olmos
- Olorgesailie
- Olympia beds
- Omagari
- Omolon
- Onaga Shale
- Onate
- Oneota Dolomite
- Onny Shale
- Onondaga
- Onzole
- Oolithe corallienne de Pagnoz
- Oolithe miliaire
- Oosterhout
- Opalinuston
- Opoka
- Oranda
- Oread
- Oread Limestone
- Oregonia
- Oriskany Sandstone
- Orr
- Osakhta
- Osawa
- Osborne Beds
- Osgood
- Osgood Shale
- Osinovaya
- Osinovo
- Osmington Oolite
- Ospika
- Otahuhu
- Otaio Gorge Sandstone
- Otamatea
- Otekaike Limestone
- Ototara Limestone
- Ottawa
- Otter
- Otter Sandstone
- Otto Fiord
- Ottweiler Stufe
- Otuma
- Oued Ali
- Oust
- Outram
- Overton
- Owl Creek
- Oxford Clay
- Oxtrack
- Ozan
- Ozirovo