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| La Meseta Formation | |
|---|---|
| Name | La Meseta Formation |
| Period | Eocene |
| Region | Antarctic Peninsula |
| Country | Argentina |
| Namedfor | La Meseta |
| Namedby | José Bonaparte |
| Year ts | 1974 |
La Meseta Formation is an Eocene sedimentary succession exposed on the Seymour Island shelf off the Antarctic Peninsula that has yielded diverse fossil assemblages crucial to understanding Paleogene Antarctic biota. The unit records marine and marginal-marine deposition during a time of major Paleogene climate change and has been central to debates involving Antarctic paleogeography, James Ross Island stratigraphy, and Southern Hemisphere biotic interchange. Research on the formation links to institutions such as the British Antarctic Survey, the Smithsonian Institution, and the Yale Peabody Museum.
The formation forms part of the Gondwana-derived stratigraphic succession on Seymour Island within the James Ross Island group, overlying Cretaceous strata and interfingering with Oligocene rocks recognized in regional correlations to the Weddell Sea margin. Its tectonostratigraphic context relates to the breakup of Gondwana and the opening of the Southern Ocean, with ties to plate reconstructions developed by researchers at the University of Cambridge and the US Geological Survey. Structural studies reference the role of regional tilting and faulting recognized during mapping campaigns led by teams from the British Antarctic Survey and the Swedish Polar Research Secretariat.
Biostratigraphic, magnetostratigraphic, and radiometric work constrain the succession to the middle to late Eocene, with correlations to the Lutetian and Bartonian stages. Key chronology has been provided by studies utilizing foraminiferal zonation, nannofossil assemblages tied to the International Commission on Stratigraphy timescale, and isotopic calibration comparable to records from the Wilson Grove Formation and other Southern Hemisphere Eocene units. Stratigraphic subdivisions include multiple shelly and tuffaceous horizons that have been correlated across the Seymour Island section and cited in regional syntheses by the Geological Society of America.
Lithologically, the succession comprises sandstones, siltstones, mudstones, and tuff beds, with shell beds and concretionary horizons that record episodic sedimentation. Petrographic and geochemical analyses by teams from the University of Buenos Aires and the University of Oslo document volcaniclastic input linked to Antarctic magmatic centers contemporaneous with rift events recognized in studies by the British Antarctic Survey. Sedimentary structures, bioturbation, and facies architecture indicate shallow marine to estuarine depositional settings comparable to modern analogues studied by the Scripps Institution of Oceanography.
The formation has produced an exceptionally diverse fossil record including marine invertebrates such as bivalves, gastropods, echinoderms, and diverse benthic foraminifera; vertebrates including well-preserved penguin remains, teleost fishes, and marine mammals; and plant remains including leaves and wood that inform paleovegetation reconstructions. Notable discoveries tie to research programs at the Natural History Museum, London, the Smithsonian Institution, and the Museo Paleontológico Egidio Feruglio, and have been featured in collaborative publications with the American Museum of Natural History. Taxa documented from the succession have been compared with Eocene faunas from the La Meseta Formation type section (site work by Argentine and international teams), as well as coeval assemblages in New Zealand and Patagonia, informing models of Southern Hemisphere dispersal promoted in literature by the Royal Society.
Evidence from stable isotopes, palynology, and paleobotanical remains indicates relatively temperate Eocene conditions with reduced Antarctic glaciation compared to Neogene climates. Oxygen isotope studies and leaf physiognomy analyses conducted in collaboration with laboratories at the University of Cambridge and the University of California, Santa Cruz suggest seasonally mild climates and vegetated coastal environments. These paleoenvironmental reconstructions contribute to broader debates about Eocene greenhouse climates, polar amplification, and the timing of Antarctic glaciation explored in reports by the Intergovernmental Panel on Climate Change and specialized articles in journals affiliated with the Geological Society of London.
Systematic study of the succession began in the mid-20th century with Argentine and British expeditions, including seminal mapping and fossil collecting by scientists associated with the Instituto Antártico Argentino and the British Antarctic Survey. Subsequent field and laboratory programs involving institutions such as the Smithsonian Institution, the University of Buenos Aires, the Yale Peabody Museum, and the Natural History Museum, London expanded taxonomic and stratigraphic understanding. International collaborations and Antarctic Treaty-supported logistics facilitated multidisciplinary campaigns that linked paleontology, stratigraphy, and geochronology, producing high-impact syntheses published through outlets tied to the Geological Society of America and the Royal Society.
Exposures are concentrated on Seymour Island and adjacent islands in the James Ross Island group off the northeastern tip of the Antarctic Peninsula, within the jurisdictional framework of Antarctic treaty zones managed through consultative meetings involving parties such as Argentina and the United Kingdom. The regional geological setting interfaces with the Weddell Sea Embayment and is integral to reconstructions of Eocene paleogeography of southern high latitudes advanced by researchers at the British Antarctic Survey and the University of Tasmania.
Category:Eocene geology Category:Antarctic paleontology