The Griman Creek Formation is a geological formation in northern New South Wales and southern Queensland, Australia whose strata date back to the Albian-Cenomanian stages of the mid-Cretaceous. It is most notable being a major source of opal, found near the town of Lightning Ridge, New South Wales. Alongside the opal opalised fossils are also found, including those of dinosaurs and primitive monotremes.
Description As a whole, the formation primarily consists of thinly bedded medium to fine sandstone, siltstone and mudstone, with sporadic coal seams. In the vicinity of Lightning Ridge, it is divided up into two informal members the underlying Wallangulla Sandstone Member which primarily consists of red fine grained sandstone, light siltstone and grey claystone and is up to thick while the overlying Coocoran Claystone consists of about 10 metres of claystone. The contact between the two units is sudden and unconformable. Discontinuous clay lens beds within the Wallangulla Sandstone Member near Lightning Ridge, referred to as the Finch Clay Facies, are one of Australia's primary sources of commercial precious opal, with many mines dug in the area. These deposits are also the primary source of fossils within the formation, a large proportion of which are preserved as semi-precious opalized pseudomorphs. The fauna found in lightning ridge indicates that the depositional environment of the Finch Clay Facies was in near-coastal freshwater lagoons.
Background
Fossil content Indeterminate avialan, euornithopod, and sauropod remains that were once misidentified as brachiosaurid are present in New South Wales, Australia. Euornithopod tracks are also present in New South Wales.
Dinosaurs
Ornithischians Indeterminate ornithopods and iguanodontians are known from the formation. Indeterminate avetheropods and megaraptorans are known from the formation.
Ornithischians of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Ankylosauria Indet. Indeterminate Osteoderm Elasmaria indet. Indeterminate New South Wales, Australia An articulated hindlimb comprising the femur, tibia, astragalus Fostoria F. dhimbangunmal New South Wales, Australia A elasmarian ornithopod Fulgurotherium F. australe New South Wales, Australia An indeterminate ornithischian Weewarrasaurus W. pobeni New South Wales, Australia Isolated dentary A non-iguanodontian ornithopod
Sauropods Two species of titanosauriforms and one species of titanosaur are known from teeth.
Sauropods of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Sauropoda Indet. Indeterminate Five morphotypes of teeth indicating at least two distinct non-titanosaur titanosauriform species and one titanosaur species. An indeterminate sauropod
Theropods Theropods of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Enantiornithes Indet. Indeterminate Partial femora Megaraptora Indet. ("Lightning Claw") IndeterminateNew South Wales, AustraliaPartial skeleton including parts of the lower arm, claws, lower leg, part of the hip, and pieces of ribs. Noasauridae Indet. Indeterminate Cervical vertebra Rapator"Table 4.1," in R. ornitholestoides New South Wales, Australia "Manual element" A megaraptoran theropod Walgettosuchus"Table 4.1," in W. woodwardi New South Wales, Australia "Vertebra" An indeterminate theropod
Pterosaurs Pterosaurs of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Anhangueria Indet. Indeterminate "two isolated tooth crowns", possible limb elements
Crocodylomorphs Crocodylomorphs of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Isisfordia I. molnari Lightning Ridge, New South Wales, Australia Braincase and referred maxillary fragment A neosuchian metasuchian
Turtles Turtle of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage SpoochelysT-Bone Extension, Coocoran Opal Fields at Fossilworks.org S. ormondea perichelydian stem-turtle Chelidae Indet.Indeterminate
Mammals
Monotremes Monotremes of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImageDharragarraD. aurora A partial left mandibular ramus. A ornithorhynchid monotreme Kollikodon K. ritchiei An opalised dentary fragment, with one premolar and two molars in situ, as well as a referred maxillary fragment containing the last premolar and all four molars A kollikodontid monotremeOpaliosO. splendens A fragmentary left dentary. A opalionid monotremeParvopalusP. clytiei A partial left dentary. A steropodontid monotreme Steropodon S. galmani A steropodontid monotreme Stirtodon S. elizabethae A large isolated premolars. A teinolophid monotreme
Fish
Lobe-finned Fish Lobe-finned Fish of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Ceratodus C. diutinus Isolated tooth plates A ceratodontid lungfish Metaceratodus M. wollastoni Isolated tooth plates A ceratodontid lunfish Neoceratodus N. potkooroki Isolated tooth plates A neoceratodontid lungfish
Ray-finned Fish Ray-finned Fish of the Griman Creek FormationGenusSpeciesLocationStratigraphic positionMaterialNotesImage Calamopleurus? C. sp. Isolated jaw bones
See also List of dinosaur-bearing rock formations South Polar region of the Cretaceous Western Interior Seaway Cenomanian-Turonian extinction event
References
Bibliography