La Meseta Formation

La Meseta Formation Stratigraphic range: Eocene PreЄ Є O S D C P T J K Pg N
Type	Geological formation
Unit of	Seymour Island group.[1]
Underlies	Pleistocene glacial deposits
Overlies	Lopez de Bertodano Formation, Sobral Formation, Cross Valley Formation
Thickness	557 m.[2]
Location
Coordinates	64°14′21.782″S 56°36′11.69″W / 64.23938389°S 56.6032472°WCoordinates: 64°14′21.782″S 56°36′11.69″W / 64.23938389°S 56.6032472°W.[3]

The La Meseta Formation is a sedimentary sequence deposited during the Eocene.^[2] The formation is found on Seymour Island, Antarctica.

La Meseta Formation lies unconformably on the Cretaceous Lopez de Bertodano Formation. It is an approximately 557 m 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.^[3][2] La Meseta Formation is just one of the sequences that make up the fill of the Late Jurassic to Paleogene James Ross Basin.^[3]

Fossils

La Meseta Formation is extremely rich in fossils. 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 are also an abundance of trace fossils. Diplocraterion, Helminthopsis, Muensteria, Oichnus, Ophiomorpha, Skolithos, Teredolites and Zapfella have been described.^[4] Over 35 species and 26 families of fish have been described from the Ypresian Cucullaea bed.^[3]

List of bird fossils:

• Archaeospheniscus wimani
• Archaeospheniscus lopdelli
• Palaeeudyptes antarcticus
• Palaeeudyptes gunnari
• Palaeeudyptes klekowskii

References

1. Zinsmeister, Jeffrey D. Stilwell ; William J. (1992). Molluscan systematics and biostratigraphy : Lower Tertiary La Meseta Formation, Seymour Island, Antarctic Peninsula. Washington, DC: American Geophysical Union. ISBN 978-0875907703.
2. Pezzetti, T.F.; KRISSEK, L.A (1986). "Re-evaluation of the Eocene LaMeseta Formation of Seymour Island, AntarcticPeninsula": 75.
3. Reguero, Marcelo A.; Sergio A. Marenssi; Sergio N. Santillana (2012). "Weddellian marine/coastal vertebrates diversity from a basal horizon (Ypresian, Eocene) of the Cucullaea I Allomember, La Meseta formation, Seymour (Marambio) Island, Antarctica". Rev. peru. biol. 19: 275–284.
4. Uchman, Alfred; Andrzej GAŹDZICKI (2006). "New trace fossils from the La Meseta Formation (Eocene) of Seymour Island, Antarctica". Pol. Polar Res. 27: 153–170.