The La Meseta Formation is a sedimentary sequence deposited during much of the Paleogene on Seymour Island off the coast of the Antarctic Peninsula. It is noted for its fossils, which include both marine organisms and the only terrestrial vertebrate fossils from the Cenozoic of Antarctica.
In some treatments, the La Meseta Formation is restricted to just the older Thanetian to Lutetian-aged strata, with the younger Bartonian to Rupelian strata treated as the overlying Submeseta Formation. However, other papers instead treat the Submeseta Formation as an allomember of the La Meseta Formation.
Description
La Meseta Formation lies unconformably on the Cretaceous Lopez de Bertodano Formation. It is an approximately thick sequence of poorly consolidated sandstones and siltstones. The depositional environment was probably coastal, deltaic or estuarine in character. The top of the sequence is an erosional unconformity to Pleistocene glacial gravels. La Meseta Formation is one of the sequences that make up the fill of the Late Jurassic to Paleogene James Ross Basin.
Paleoenvironment
The terrestrial environment surrounding the deposition area is thought to have been a temperate polar forest, including podocarp and araucarian conifers, as well as Nothofagus. Most of the fossilized woods and flowers discovered on Seymour Islands consist of extinct species of conifer trees and lilies during warm climate.
Paleobiota
La Meseta Formation is extremely rich in fossils. Among mammals, the meridiungulata Antarctodon and Trigonostylops have been found in the formation. as well as marsupial Derorhynchidae, Microbiotheria, and polydolopimorphia. It is famous for its penguin fossils, for example the two genera Archaeospheniscus and Palaeeudyptes. Other bird fossils include Dasornis, a genus of pseudotooth birds. There is also an abundance of trace fossils. Diplocraterion, Helminthopsis, Muensteria, Oichnus, Ophiomorpha, Skolithos, Teredolites and Zapfella have been described. Over 35 species and 26 families of fish, which includes sharks, have been described from the Ypresian Cucullaea bed.
Mammals
Meriduingulata
Astrapotheria
Litopterna
Cetaceans
Metatherians
Derorhynchidae
Microbiotheria
Polydolopimorphia
Other mammals
Birds
Sphenisciformes
Other birds
Reptiles
Amphibians
Cartilaginous fish
Chimaeras
Sharks
Rays
Ray-finned fish
Cephalopods
Plants
See also
References
Further reading
- R. A. Askin. 1997. Eocene-?Earliest Oligocene terrestrial palynology of Seymour Island, Antarctica. : 993-996. The Antarctic Region: Geological Evolution and Processes 993-996
- M. A. Bitner. 1991. A supposedly new brachiopod from the Paleogene of Seymour Island, West Antarctica. Polish Polar Research 12(2):243-246
- M. Bond, M. A. Reguero, S. F. Vizcaino and S. A. Marenssi. 2006. A new 'South American ungulate' (Mammalia: Litopterna) from the Eocene of the Antarctic Peninsula. Geological Society, London, Special Publications 258:163-176
- J. A. Case. 1988. Paleogene floras from Seymour Island, Antarctic Peninsula. Geology and Paleontology of Seymour Island Antarctic Peninsula 523-540
- M. M. Cenizo. 2012. Review of the putative Phorusrhacidae from the Cretaceous and Paleogene of Antarctica: new records of ratites and pelagornithid birds. Polish Polar Research 33(3):225-244
- A. L. Cione, M. de las Mercedes Azpelicueta, and D. R. Bellwood. 1995. An oplegnathid fish from the Eocene of Antarctica. Palaeontology 37(4):931-940
- A. L. Cione and M. A. Reguero. 1994. New records of the sharks Isurus and Hexanchus from the Eocene of Seymour Island, Antarctica. Proceedings of the Geologists' Association 105:1-14
- S. A. Marenssi, M. A. Regeuro, S. N. Santillana and S. F. Vizcaino. 1994. Eocene land mammals from Seymour Island, Antarctica: palaeobiogeographical implications. 6(1):3-15
- I. Poole, A. M. W. Mennega, and D. J. Cantrill. 2003. Valdivian ecosystems in the Late Cretaceous and Early Tertiary of Antarctica: further evidence from myrtaceous and eucryphiaceous fossil wood. Review of Palaeobotany and Palynology 124:9-27
- R. R. Pujana, S. N. Santillana, and S. A. Marenssi. 2014. Conifer fossil woods from the La Meseta Formation (Eocene of Western Antarctica): Evidence of Podocarpaceae-dominated forests. Review of Palaeobotany and Palynology (200)122-137
- S. F. Vizcaino, M. A. Reguero, S. A. Marenssi and S. N. Santillana. 1997. New land mammal-bearing localities from the Eocene La Meseta Formation, Seymour Island, Antarctica. The Antarctic Region: Geological Evolution and Processes 997-1000