Lopez de Bertodano Formation

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Lopez de Bertodano Formation
Stratigraphic range: Maastrichtian-Danian
~70–65.5 Ma
Type Geological formation
Unit of Marambio Group
Underlies Sobral Fm., La Meseta Fm.
Overlies Snow Hill Island Formation
Lithology
Primary Siltstone, mudstone
Other Sandstone with concretions
Location
Region Seymour Island, James Ross Island group
Country Antarctica

The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous (upper-lower Maastrichtian stage[1]) to the Danian stage of the lower Paleocene, about 70-65.5 million years ago.[2]

Fossil content[edit]

Dinosaur remains are among the fossils that have been recovered from the formation[3] and include at least two and probably as much as six lineages of indisputably modern birds: one related to waterfowl, a primitive shorebird or related form, 1-2 species of possible loons, a large and possibly flightless bird belonging to a lineage extinct today as well as a partial skull that might belong to either of the smaller species or represent yet another one. The formation also contains a rich fossil invertebrate fauna, including bivalves, gastropods,[4] and cephalopods (ammonites and nautiloids[5]).

The Cretaceous-Paleogene boundary (K-Pg) outcrops on Seymour Island in the upper levels of the López de Bertodano Formation.[6] A small (but significant) iridium anomaly occurs at the boundary on Seymour Island, as at lower latitudes, thought to be fallout from the Chicxulub impactor in the Gulf of Mexico.[7] Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event.[6] Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction,[8] but the extent to which these affected marine biodiversity is debated. Based on extensive marine fossil collections from Seymour Island, recent work has confirmed that a single and severe mass extinction event occurred at this time in Antarctica just as at lower latitudes.[9]

Fossils from the formation[edit]

Dinosaurs of the Lopez de Bertodano Formation
Genus Species Unit Material Description

Polarornis[3]

P. gregorii[3]

Lower Sandwich Bluff Member

Partial skull and skeleton, holotype

A loon?

P.? sp.

Lower Sandwich Bluff Member

Partial skeleton including wing and hindlimbs

Possibly a more primitive form with strong flight ability and lighter bones

Vegavis

V. iaai[10]

Lower Sandwich Bluff Member

Partial skeleton, holotype

An anseriform

Undescribed Cariamae[11]

Unnamed species

Cape Lamb Member

Isolated femur

Close relative of cariamids and phorusrhacids

Undescribed charadriiform[12]

Unnamed species

Cape Lamb Member

Partial skeleton

Unidentified Neornithes[13]

Unnamed species

Partial skull

Relationships undetermined, cranium some 5–6 cm long.

Morrosaurus[14]

M. antarcticus[14]

Undescribed hadrosaurid[1]

Unnamed species

Isolated tooth[1]

Undescribed non-avian theropod[1]

Unnamed species

Fragments[1]

See also[edit]


References[edit]

  1. ^ a b c d e Olivero, E.B.; Ponce, J.J.; Marsicano, C.A.; Martinioni, D.R. (2007). "Depositional settings of the basal Lopez de Bertodano Formation, Maastrichtian, Antarctica". Revista de la Asociación Geológica Argentina. 62 (4): 521–529. 
  2. ^ Bowman, V.; Ineson, J.; Riding, J.; Crame, J.; Francis, J.; Condon, D.; Whittle, R.; Ferraccioli, F. (2016). "The Paleocene of Antarctica: Dinoflagellate cyst biostratigraphy, chronostratigraphy and implications for the palaeo-Pacific margin of Gondwana". Gondwana Research. 38: 132–148. doi:10.1016/j.gr.2015.10.018. 
  3. ^ a b c Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, Antarctica)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. p. 606. ISBN 0-520-24209-2.
  4. ^ Crame, J.A.; Beu, A.G.; Ineson J.R.; Francis J.A.; Whittle R.J.; Bowman V.C. (2014). "The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications". PLOS ONE. 7: e114743. doi:10.1371/journal.pone.0114743. 
  5. ^ Witts, J.D.; Bowman V.C.; Wignall P.B.; Crame J.A.; Francis, J.E.; Newont, R.J. (2015). "Evolution and extinction of Maastrichtian (Late Cretaceous) cephalopods from the López de Bertodano Formation, Seymour Island, Antarctica". Palaeogeography, Palaeoclimatology, Palaeoecology. 418: 193–212. doi:10.1016/j.palaeo.2014.11.002. 
  6. ^ a b Zinsmeister, W.J. (1998). "Discovery of fish mortality horizon at the K-T Boundary on Seymour Island: Re-evaluation of events at the end of the Cretaceous". Journal of Paleontology. 72 (3). 
  7. ^ Elliot D.H.; Askin RA; Kyte FT; Zinsmeister WJ (1994). "Iridium and dinocysts at the Cretaceous-Tertiary boundary on Seymour Island, Antarctica: Implications for the K-T event". Geology. 22: 675. doi:10.1130/0091-7613(1994)022<0675:IADATC>2.3.CO;2. 
  8. ^ Petersen, S.V.; Dutton A; Lohmann KC (2016). "End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change". Nature Communications. 7: 12079. doi:10.1038/ncomms12079. 
  9. ^ Witts J.D.; Whittle RJ; Wignall PB; Crame JA; Francis JE; Newton RJ; Bowman VC (2016). "Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica". Nature Communications. 7: 11738. doi:10.1038/ncomms11738. PMC 4894978Freely accessible. PMID 27226414. 
  10. ^ Clarke, J.A.; Tambussi, C.P.; Noriega, J.I.; Erickson, G.M.; Ketcham, R.A. (2005). "Definitive fossil evidence for the extant avian radiation in the Cretaceous" (PDF). Nature. 433: 305–308. doi:10.1038/nature03150.  Supporting information
  11. ^ Case, J.; Reguero, M.; Martin, J.; Cordes-Person, A. (2006). "A cursorial bird from the Maastrictian of Antarctica". Journal of Vertebrate Paleontology. 26 (3): 48A. doi:10.1080/02724634.2006.10010069. 
  12. ^ Cordes (2002). "A new charadriiform avian specimen from the Early Maastrichtian of Cape Lamb, Vega Island, Antarctic Peninsula". Journal of Vertebrate Paleontology. 22 (3): 46A. 
  13. ^ NUEVOS RESTOS DE DINOSAURIA DEL CRETÁCICO DE LAS ISLAS JAMES ROSS Y MARAMBIO, PENÍNSULA ANTÁRTICA
  14. ^ a b Rozadilla, Sebastián; Agnolin, Federico L.; Novas, Fernando E.; Aranciaga Rolando, Alexis M.; Motta, Matías J.; Lirio, Juan M.; Isasi, Marcelo P. (2016). "A new ornithopod (Dinosauria, Ornithischia) from the Upper Cretaceous of Antarctica and its palaeobiogeographical implications". Cretaceous Research. 57: 311–324. doi:10.1016/j.cretres.2015.09.009.