Lopez de Bertodano Formation

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, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.[2]

Lopez de Bertodano Formation
Stratigraphic range: Maastrichtian-Danian
~70–65.5 Ma
↓
TypeGeological formation
Unit ofMarambio & Seymour Island Groups
Sub-unitsCape Lamb & Lower Sandwich Bluff Members
UnderliesSobral Fm., La Meseta Fm.
OverliesSnow Hill Island Formation
Lithology
PrimarySiltstone, mudstone
OtherSandstone with concretions
Location
Coordinates64.0°S 57.4°W / -64.0; -57.4
Approximate paleocoordinates61.9°S 68.1°W / -61.9; -68.1
RegionSeymour Island, James Ross Island group
CountryAntarctica
Type section
Named forLópez de Bertodano Bay
Lopez de Bertodano Formation (Antarctica)

Cretaceous-Paleogene boundary
Geologic map of Seymour Island, Antarctica with the Lopez de Bertodano Formation in light green, the locations where the Cretaceous–Paleogene boundary is exposed are indicated

The Cretaceous–Paleogene boundary (K–Pg) crops out on Seymour Island in the upper levels of the Lopez de Bertodano Formation.[3] 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.[4] Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event.[3] Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction,[5] 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.[6]

Fossil content

The Lopez de Bertodano Formation has provided many fossils of flora, dinosaurs and birds.[7][8][9] Also the first fossil egg from Antarctica, Antarcticoolithus, was found in the formation.[10]

Dinosaur remains are among the fossils that have been recovered from the formation[11] 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 to 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,[12] and cephalopods (ammonites and nautiloids).[13]

Dinosaurs
Genus Species Member Material Description Image
Polarornis P. gregorii Lower Sandwich Bluff Partial skull and skeleton, holotype A loon?[11]
P.? sp. Lower Sandwich Bluff Partial skeleton including wing and hindlimbs Possibly a more primitive form with strong flight ability and lighter bones
Vegavis V. iaai[14] Lower Sandwich Bluff Partial skeleton, holotype An anseriform
V. sp. Cape Lamb Isolated femur Initially identified as a fossil of a member of Cariamae,[15] but subsequently reinterpreted as a fossil of an unnamed large-bodied member of the genus Vegavis.[16]
Conflicto C. antarcticus Partial skeleton An anseriform
Morrosaurus[17] M. antarcticus An elasmarian ornithopod
Undescribed charadriiform[18] Unnamed species Cape Lamb Partial skeleton
Unidentified Neornithes Unnamed species Partial skull Relationships undetermined, cranium some 5–6 centimetres (2.0–2.4 in) long
Undescribed hadrosaurid Unnamed species Isolated tooth[1]
Undescribed non-avian theropod Unnamed species Fragments[1]

Other fossils

Among others, the following fossils have been found in the formation:

Ammonites[13]
  • Diplomoceras cylindraceum
  • Gaudryceras seymouriense
  • Grossouvrites joharae
  • Kitchinites laurae
  • Maorites densicostatus
  • Pachydiscus (Pachydiscus) ultimus
  • Zelandites varuna
  • Pseudophyllites cf. loryi
Other invertebrates
  • Eutrephoceras dorbignyanum
  • Rotularia fallax
  • Cyathocidaris nordenskjoldi, C. patera
Flora
  • Antarctoxylon juglandoides
  • Eucryphiaceoxylon eucryphioides
  • Myrceugenelloxylon antarcticus
  • pollen

See also

References
  1. 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. Bibcode:2016GondR..38..132B. doi:10.1016/j.gr.2015.10.018.
  3. 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): 556–571. doi:10.1017/S0022336000024331.
  4. 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 (8): 675. Bibcode:1994Geo....22..675E. doi:10.1130/0091-7613(1994)022<0675:IADATC>2.3.CO;2.
  5. 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. Bibcode:2016NatCo...712079P. doi:10.1038/ncomms12079. PMC 4935969. PMID 27377632.
  6. 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. Bibcode:2016NatCo...711738W. doi:10.1038/ncomms11738. PMC 4894978. PMID 27226414.
  7. Marambio Group - Lopez de Bertodano Formation at Fossilworks.org
  8. Seymour Island Group - Lopez de Bertodano Formation at Fossilworks.org
  9. Upper Lopez de Bertodano Formation at Fossilworks.org
  10. Legendre et al., 2020
  11. 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.
  12. 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 (12): e114743. Bibcode:2014PLoSO...9k4743C. doi:10.1371/journal.pone.0114743. PMC 4262473. PMID 25493546.
  13. 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" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 418: 193–212. Bibcode:2015PPP...418..193W. doi:10.1016/j.palaeo.2014.11.002.
  14. 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 (7023): 305–308. Bibcode:2005Natur.433..305C. doi:10.1038/nature03150. PMID 15662422. S2CID 4354309. Supporting information
  15. 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. S2CID 220413406.
  16. Abagael R. West; Christopher R. Torres; Judd A. Case; Julia A. Clarke; Patrick M. O'Connor; Matthew C. Lamanna (2019). "An avian femur from the Late Cretaceous of Vega Island, Antarctic Peninsula: removing the record of cursorial landbirds from the Mesozoic of Antarctica". PeerJ. 7: e7231. doi:10.7717/peerj.7231. PMC 6626523. PMID 31333904.
  17. 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.
  18. 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.

Bibliography

Further reading
  • Poole, I.; Mennega, A. M. W.; Cantrill, D. J. (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 (1–2): 9–27. doi:10.1016/s0034-6667(02)00244-0. hdl:1874/31608.
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