Griman Creek Formation

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.Template:Sfn 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.Template:Sfn

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.Template:Sfn

Background

File:Geology of Asia 100Ma.jpg

Australia was located near the South Pole in the Early and Middle Cretaceous
GPlates reconstruction for 100 Ma (Albian-Cenomanian and Early and Late Cretaceous boundary)

File:90 Ma - Late Cretaceous paleogeography with known distribution of Arcellites disciformis indicated.jpg

Paleogeography of the Turonian (90 Ma)
Original map by Ron Blakey

Fossil content

Indeterminate avialan, euornithopod, and sauropod remains that were once misidentified as brachiosaurid are present in New South Wales, Australia.Template:Sfn Euornithopod tracks are also present in New South Wales.

Dipnoi

Dipnoi of the Griman Creek Formation
Taxa	Species	Presence	Material	Notes	Images
Ceratodus	C. diutinus		Isolated tooth plates
Metaceratodus	M. wollastoni		Isolated tooth plates
Neoceratodus	N. potkooroki		Isolated tooth plates

Actinopterygii

Actinopterygians of the Griman Creek Formation
Taxa	Species	Presence	Material	Notes	Images
Calamopleurus?	sp.		Isolated jaw bones

Mammals

Monotremes

Mammals
Genus	Species	Presence	Materials	Notes	Images
Dharragarra	D. aurora		A partial left mandibular ramus.	A 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 monotreme.
Opalios	O. splendens		A fragmentary left dentary.	A monotreme.
Parvopalus	P. clytiei		A partial left dentary.	A monotreme.
Steropodon	S. galmani			A monotreme	File:Steropodon BW.jpg
Stirtodon	S. elizabethae		A large isolated premolars.	A monotreme

Crocodyliformes

Crocodyliformes
Genus	Species	Presence	Materials	Notes	Images
Isisfordia	I. molnari	Lightning Ridge	Braincase and referred maxillary fragmentTemplate:Sfn	A crocodyliform.	File:Isisfordia.jpg

Dinosaurs

Indeterminate ornithopods and iguanodontians are known from the formation.Template:Sfn Indeterminate avetheropods and megaraptorans are known from the formation.Template:Sfn Two species of titanosauriforms and one species of titanosaur are known from teeth.Template:Sfn

Dinosaurs
Genus	Species	Presence	Notes	Images
Fostoria	F. dhimbangunmal	New South Wales	A member of Rhabdodontomorpha.
Fulgurotherium	F. australe	New South Wales	Template:Sfn
Rapator	R. ornitholestoides	New South Wales	A megaraptoran; "Manual element"Template:Sfn	File:Rapator.png
Walgettosuchus	W. woodwardi	New South Wales	"Vertebra"Template:Sfn Later determined to be an indeterminate theropodTemplate:Sfn	File:Walgettosuchus.png
Weewarrasaurus	W. pobeni	New South Wales	An ornithopod known from an isolated dentaryTemplate:Sfn
Ankylosauria	Indeterminate		OsteodermTemplate:Sfn
Enantiornithes	Indeterminate		Partial femora
Megaraptora ("Lightning Claw")	Indeterminate	New South Wales	Partial skeleton including parts of the lower arm, claws, lower leg, part of the hip, and pieces of ribs.Template:Sfn
Noasauridae	Indeterminate		Cervical vertebraTemplate:Sfn
Sauropoda	Indeterminate		A tooth

Pterosaurs

Pterosaurs
Genus	Species	Presence	Notes	Images
Anhangueria	Indeterminate		"two isolated tooth crowns", possible limb elements

Testudines

Turtles
Genus	Species	Presence	Notes	Images
Spoochelys	S. ormondea		Perichelydian stem-turtleTemplate:Sfn
Chelidae	Indeterminate

See also

• List of dinosaur-bearing rock formations
• South Polar region of the Cretaceous
• Western Interior Seaway
• Cenomanian-Turonian extinction event