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 of the Early-Late Cretaceous.[1] 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.[2]

Not to be confused with Gorman Creek Formation.
Griman Creek Formation
Stratigraphic range: late Albian-early-mid Cenomanian
~105–96 Ma
TypeGeological formation
Unit ofRolling Downs Group
Sub-unitsCoocoran Claystone & Wallangulla Sandstone Members
UnderliesUnconformity with Oligo-Miocene Cumborah Gravel
OverliesSurat Siltstone, Wallumbilla Formation
ThicknessUp to 345 m (1,132 ft)
Lithology
PrimarySandstone, siltstone, mudstone
OtherConglomerate, coal
Location
Coordinates29.4°S 147.7°E / -29.4; 147.7
Approximate paleocoordinates64.4°S 134.9°E / -64.4; 134.9
Region Queensland
 New South Wales
Country Australia
ExtentSurat Basin
Type section
Named forGriman Creek
Named byReiser
Year defined1970
Griman Creek Formation (Australia)

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 30 metres (98 ft) 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 depositonal environment of the Finch Clay Facies was in near-coastal freshwater lagoons.[1]

Background
See also: Surat Basin
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)
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.[2] Euornithopod tracks are also present in New South Wales.

Mammals
Mammals
GenusSpeciesPresenceNotesImages
Kollikodon K. ritchiei
Steropodon S. galmani
Stirtodon S. elizabethae

Crocodyliformes
Crocodyliformes
GenusSpeciesPresenceNotesImages
Isisfordia I. molnari Lightning Ridge Braincase and referred maxillary fragment[3]

Dinosaurs

Indeterminate ornithopods and iguanodontians are known from the formation.[4] Indeterminate avetheropods and megaraptorans are known from the formation.[1] Two species of titanosauriforms and one species of titanosaur are known from teeth.[5]

Dinosaurs
GenusSpeciesPresenceNotesImages
Fostoria F. dhimbangunmal New South Wales A member of Rhabdodontomorpha.
Fulgurotherium F. australe New South Wales [2]
Rapator R. ornitholestoides New South Wales A megaraptorid; "Manual element"[2][6]
Walgettosuchus W. woodwardi New South Wales "Vertebra"[2][7]
Later determined to be an indeterminate theropod[2]
Weewarrasaurus W. pobeni New South Wales An ornithopod known from an isolated dentary[4]
Ankylosauria Indeterminate Osteoderm[8]
Enantiornithes Indeterminate Partial femora
Megaraptora Indeterminate New South Wales Partial skeleton including parts of the lower arm, claws, lower leg, part of the hip, and pieces of ribs.[9]
Noasauridae Indeterminate Cervical vertebra[10]
Sauropoda Indeterminate A tooth

Pterosaurs
Pterosaurs
GenusSpeciesPresenceNotesImages
Anhangueria Indeterminate "two isolated tooth crowns", possible limb elements

Testudines
Turtles
GenusSpeciesPresenceNotesImages
Spoochelys S. ormondea Perichelydian stem-turtle[11][12]

See also
Australia
South America
North America
Europe
Asia

References
  1. Bell et al., 2019
  2. Weishampel et al., 2004, pp.573-574
  3. Hart et al., 2019
  4. Bell et al., 2018
  5. Frauenfelder et al. 2020
  6. "Table 4.1," in Weishampel et al., 2004, p.74
  7. "Table 4.1," in Weishampel et al., 2004, p.78
  8. Bell et al., 2017
  9. Bell et al. 2016
  10. Brougham et al., 2020
  11. T-Bone Extension, Coocoran Opal Fields at Fossilworks.org
  12. Smith et al., 2013

Bibliography
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