Açu Formation
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Early Cretaceous geologic formation in Ceará, Brazil
| Açu Formation | |
|---|---|
| Stratigraphic range: Albian ~112–100 Ma | |
| Type | Geological formation |
| Unit of | Apodi Group |
| Underlies | Jandaíra Formation |
| Overlies | Alagamar Formation |
| Lithology | |
| Primary | Sandstone |
| Location | |
| Coordinates | 5°48′S 38°06′W / 5.8°S 38.1°W / -5.8; -38.1 |
| Approximate paleocoordinates | 11°54′S 10°54′W / 11.9°S 10.9°W / -11.9; -10.9 |
| Region | Ceará |
| Country | Brazil |
| Extent | Potiguar Basin |
  Açu Formation (Brazil) | |
The Açu Formation is an Early Cretaceous (Albian) geologic formation of the Potiguar Basin in Ceará, northeastern Brazil. The formation comprises coarse-grained sandstones deposited in a fluvio-deltaic environment. The Açu Formation, belonging to the Apodi Group, has provided fossils of an indeterminate rebbachisaurid.
The Açu Formation was deposited in a passive margin setting, overlying the Alagamar Formation and is overlain by the Jandaíra Formation. In the petroleum producing Potiguar Basin, the formation is a reservoir rock.[1]
Fossil content
The following fossils were reported from the formation:[2]
Color key
|
Notes Uncertain or tentative taxa are in small text; |
Dinosaurs
Sauropods
| Sauropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Rebbachisauridae indet.[3] | Indeterminate | Ceará | Albian | Vertebrae | ||
| Tiamat[4] | T. valdecii | Ceará | Albian to Cenomanian | Caudal vertebrae | A titanosaurian sauropod; closely related to Andesaurus delgadoi. |  |
| Titanosauria Indet.[5] | Indeterminate | Ceará | Albian | Osteoderm | ||
Theropods
| Theropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Abelisauridae Indet.[6] | Indeterminate | Ceará | Albian to Cenomanian | Teeth & Completed Femur | ||
| Baryonychinae Indet. | Indeterminate | Ceará | Albian | Tooth | A spinosaurid theropod | |
| Carcharodontosauridae Indet. | Indeterminate | Ceará | Albian | Vertebrae | ||
| Megaraptora Indet. | Indeterminate | Ceará | Albian | Vertebrae | ||
| Noasauridae Indet. | Indeterminate | Ceará | Albian to Cenomanian | Teeth | ||
| Paraves Indet. | Indeterminate | Ceará | Albian | Vertebrae | A maniraptoran theropod | |
| Spinosaurinae Indet. | Indeterminate | Ceará | Albian | Tooth | A spinosaurid theropod | |
Crocodylomorphs
| Crocodylomorps of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Candidodontidae Indet.[7] | Indeterminat | Ceará | Albian to Cenomanian | |||
| Itasuchidae Indet. | Indeterminate | Ceará | Albian to Cenomanian | |||
| Peirosauridae Indet. | Indeterminate | Ceará | Albian | Insolated Tooth | ||
| Sphagesauria Indet. | Indeterminate | Ceará | Albian to Cenomanian | |||
Fish
| Fish of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Arganodus | A. tiguidiensis | Ceará | Albian | Teeth | A arganodontid lungfish | |
| Ceratodus | C. brasilensis | Ceará | Albian | Teeth | A ceratodontid lungfish | |
| Bawitius | B. bartheli | Ceará | Albian | Scales & Tooth | A bichir | |
| Distobatus[8] | D. potiguarense | Ceará | Albian to Cenomanian | A distobatid hybodont | ||
| Lepisosteus[9] | L. sp. | Ceará | Albian to Cenomanian | Scales & Tooth | A gar | |
| Mawsonia | M. gigas | Ceará | Albian to Cenomanian | A mawsoniid coelacanth | ||
| Pycnodontiformes Indet. | Indeterminate | Ceará | Albian | Teeth | ||
| Tharrhias | T. castelhanoi | Ceará | Albian | Scales | A gonorynchiform fish | |
| Tribodus | T. limae | Ceará | Albian to Cenomanian | A hybodont shark | ||
| Vidalamiinae Indet. | Indeterminate | Ceará | Albian | |||
Crustaceans
| Crustaceans of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Unusuropode | U. castroi | Ceará | Albian | A isopod | ||
Molluscs
Bivalves
| Bivalves of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Brachidontes | B. sp. | Ceará | Albian | A mytilid mussel | ||
| Mytilus | M. rosadoi | Ceará | Albian | A mytilid mussel | ||
Gastropods
| Gastropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Gastropoda Indet. | Indeterminate | Ceará | Albian | |||
Echinoderms
| Echinoderms of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Echinodermata Indet. | Indeterminate | Rio Grande do Norte | Albian | |||
Plants
| Plants of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Palmoxylon | P. sp. | Rio Grande do Norte | Albian | |||
Bibliography
- Gomes da Costa Pereira, Paulo Victor; Ribeiro, Theo Baptista; Brusatte, Stephen Louis; Dos Anjos Candeiro, Carlos Roberto; da Silva Marinho, Thiago; Paglarelli Bergqvist, Lilian (2020), "Theropod (Dinosauria) diversity from the Potiguar basin (Early-late Cretaceous Albian – Cenomanian), Northeast Brazil" (PDF), Cretaceous Research, in press 104517, doi:10.1016/j.cretres.2020.104517, hdl:20.500.11820/849a673d-9aa1-4b8e-be0c-f630af8a5d5e
- Maraschin, Anderson; Mizusaki, Ana Maria P.; Vasconcelos, P.M.; Hinrichs, Ruth (2010), "Depositional age definition of the Açu Formation (Potiguar Basin, northeastern Brazil) through 40Ar-39Ar dating of early-authigenic K-feldspar overgrowths", Pesquisas Em Geociencias, 37: 85–96, doi:10.22456/1807-9806.22649, retrieved 2020-06-18
References
- ↑ Maraschin et al., 2010, p.87
- ↑ Açu Formation at Fossilworks.org
- ↑ Paulo Victor Luiz Gomes da Costa Pereira; Ingrid Martins Machado Garcia Veiga; Theo Baptista Ribeiro; Ryan Henrique Bezerra Cardozo; Carlos Roberto dos Anjos Candeiro; Lilian Paglarelli Bergqvist (2020). "The path of giants: a new occurrence of Rebbachisauridae (Dinosauria, Diplodocoidea) in the Açu Formation, NE Brazil, and its paleobiogeographic implications". Journal of South American Earth Sciences. 100 102515. Bibcode:2020JSAES.10002515P. doi:10.1016/j.jsames.2020.102515. S2CID 212916577.
- ↑ Pereira, P. V. L. G. C.; Bandeira, K. L. N.; Vidal, L. S.; Ribeiro, T. B.; Candeiro, C. R. A.; Bergqvist, L. P. (2024). "A new sauropod species from north-western Brazil: biomechanics and the radiation of Titanosauria (Sauropoda: Somphospondyli)". Zoological Journal of the Linnean Society. 202 (4). doi:10.1093/zoolinnean/zlae054.
- ↑ Pereira, P.V.L.G.C.; Marinho, T.S.; Candeiro, C.R.A.; Bergqvist, L.P. (2018). "A new titanosaurian (Sauropoda, Dinosauria) osteoderm from the Cretaceous of Brazil and its significance". Ameghiniana. 55 (6): 644–650. doi:10.5710/AMGH.26.08.2018.3168.
- ↑ Ribeiro, T. B.; Vecchietti, L. F.; Candeiro, C. R. A.; Canale, J. I.; Bergqvist, L. P.; Brito, P. M.; Pereira, P. V. L. G. C. (2025). "Overabundance of abelisaurid teeth in the Açu Formation (Albian-Cenomanian), Potiguar Basin, Northeastern Brazil: morphometric, cladistic and machine learning approaches". Journal of Vertebrate Paleontology. e2487366. doi:10.1080/02724634.2025.2487366.
- ↑ Albuquerque, A. S.; Pinheiro, A. E. P.; Ribeiro, T. B.; Bergqvist, L. P.; Pereira, P. V. L. G. C. (2025). "Crocodyliform diversity of the Açu Formation (Albian–Cenomanian), Potiguar Basin, Brazil: geographical distribution and palaeobiological implications". Papers in Palaeontology. 11 (4) e70027. Bibcode:2025PPal...1170027A. doi:10.1002/spp2.70027.
- ↑ Brito, P. M.; Veiga, I. M.; Dutheil, D. B.; Bergqvist, L. P. (2025). "First occurrence of Distobatus Werner, 1989 (Elasmobranchii: Hybodontiformes) in the middle Cretaceous (Albian–Cenomanian) of Brazil: Taxonomic and biogeographical implications". Cretaceous Research. 171 106119. 106119. doi:10.1016/j.cretres.2025.106119.
- ↑ Costa, V. P. G.; Aureliano, T.; Santos, C. L. A.; Ghilardi, A. M. (2025). "The oldest occurrence of Lepisosteus (Ginglymodi: Lepisosteiformes: Lepisosteidae) in Gondwana". Historical Biology: An International Journal of Paleobiology: 1–8. doi:10.1080/08912963.2025.2504475.