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°00′S 57°24′W / 64.0°S 57.4°W / -64.0; -57.4
Approximate paleocoordinates61°54′S 68°06′W / 61.9°S 68.1°W / -61.9; -68.1
RegionSeymour Island, James Ross Island group, Vega Island
CountryAntarctica
Type section
Named forLópez de Bertodano Bay
Lopez de Bertodano Formation is located in Antarctica
Lopez de Bertodano Formation
Lopez de Bertodano Formation (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, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.[2]

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]

Climate

During the Maastrichtian, Seymour Island was located within the Antarctic polar circle at around ~65°S latitude.[7] Chemical studies on oxygen-18 isotopes found in shells and benthic foraminifera have calculated intermediate-depth and deep-sea ocean temperatures at a mean average of 6 °C (43 °F) with fluctuations of 4–12 °C (39–54 °F) throughout the Maastrichtian; one of the same studies has also suggested that sea surface temperatures may have been colder, possibly dropping below freezing and forming sea ice at times.[8][9] Alternatively, a study using data acquired from ancient bacterial membrane lipids yielded a slightly warmer temperature of 12 ± 5 °C (54 ± 9 °F) around 66 Ma. Nevertheless, these estimated climates characterize primarily cool temperate environments with possible subpolar and warm episodes.[7]

Fossil content

The Lopez de Bertodano Formation has provided many fossils of flora, dinosaurs and birds.[10][11][12] Also the first fossil egg from Antarctica, Antarcticoolithus, was found in the formation.[13]

Dinosaur remains are among the fossils that have been recovered from the formation[14] 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,[15] and cephalopods (ammonites and nautiloids).[16]

The fish assemblage of the López de Bertodano Formation was dominated by Enchodus and ichthyodectiformes, accounting for 21.95% and 45.6% of local fish diversity respectively. Of the remaining percentages, sand sharks made up 10.5%, the cow shark Notidanodon 6.8%, chimaeras 3.9%, saw sharks 2.7%, various other teleost fish 2.4%, and the remaining 6% were shared between other sharks like Paraorthacodus, frilled sharks, Protosqualus, and Cretalamna.[17]

Dinosaurs

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Theropod
Theropods recorded from Lopez de Bertodano Formation
Genus Species Member Material Description Image
Charadriiform[18] Unnamed species Cape Lamb Partial skeleton
Conflicto C. antarcticus Partial skeleton An anseriform
Neornithes Indeterminate. Partial skull Relationships undetermined, cranium some 5–6 centimetres (2.0–2.4 in) long
Polarornis P. gregorii Lower Sandwich Bluff Partial skull and skeleton, holotype A loon?[14]
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[19] Lower Sandwich Bluff Partial skeleton, holotype An anseriform
V. sp. Cape Lamb Isolated femur Initially identified as a fossil of a member of Cariamae,[20] but subsequently reinterpreted as a fossil of an unnamed large-bodied member of the genus Vegavis.[21]
Theropoda Indeterminate. Fragments[1]
Ornithopods
Ornithopods recorded from Lopez de Bertodano Formation
Genus Species Member Material Description Image
Hadrosauridae Indeterminate. Sandwich Bluff Member Isolated cheek tooth, MLP 98-I-10-1.[1]

Reptiles

Reptiles recorded from Lopez de Bertodano Formation
Genus Species Member Material Description Image
Aristonectes[22] A. parvidens Seymour Island. Partial postcranial skeleton, MLP 89-III-3-1. A giant elasmosaur
Kaikaifilu K. hervei Seymour Island. Several incomplete parts of a skull, jawbone, 30 isolated teeth, and a partial left humerus. A mosasaur.
Morturneria M. seymourensis Seymour Island. several cervical vertebrae, a right humerus, a nearly complete left forelimb missing the proximal end of the humerus, and a left femur (TTU P9217). An elasmosaur

Other fossils

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

Ammonites[16]
Ammonites recorded from Lopez de Bertodano Formation
Genus Species Member Material Description Image
Diplomoceras D. cylindraceum A paperclip-shaped Ammonite.
Gaudryceras G. seymouriense
Grossouvrites G. joharae
Kitchinites K. laurae
Maorites M. densicostatus
Pachydiscus P. (Pachydiscus) ultimus
Pseudophyllites P. cf. loryi
Zelandites Z. varuna
Other invertebrates
Invertebrates recorded from Lopez de Bertodano Formation
Genus Species Member Material Description Image
Eutrephoceras E. dorbignyanum
Cyathocidaris C. nordenskjoldi
C. patera
Rotularia R. fallax
Flora

See also

References

  1. ^ a b c 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. ^ 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): 556–571. doi:10.1017/S0022336000024331. S2CID 132206016.
  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. ^ a b David B. Kemp; Stuart A. Robinson; J. Alistair Crame; Jane E. Francis; Jon Ineson; Rowan J. Whittle; Vanessa Bowman; Charlotte O'Brien (2014). "A cool temperate climate on the Antarctic Peninsula through the latest Cretaceous to early Paleogene". Geology. 42 (7): 583–586. Bibcode:2014Geo....42..583K. doi:10.1130/g35512.1. hdl:2164/4380.
  8. ^ Vanessa C. Bowman; Jane E. Francis; James B. Riding (2013). "Late Cretaceous winter sea ice in Antarctica?" (PDF). Geology. 41 (12): 1227–1230. Bibcode:2013Geo....41.1227B. doi:10.1130/G34891.1. S2CID 128885087.
  9. ^ Thomas S. Tobin; Peter D. Ward; Eric J. Steig; Eduardo B. Olivero; Isaac A. Hilburn; Ross N. Mitchell; Matthew R. Diamond; Timothy D. Raub; Joseph L. Kirschvink (2012). "Extinction patterns, δ18 O trends, and magnetostratigraphy from a southern high-latitude Cretaceous–Paleogene section: Links with Deccan volcanism". Palaeogeography, Palaeoclimatology, Palaeoecology. 350–352 (2012): 180–188. Bibcode:2012PPP...350..180T. doi:10.1016/j.palaeo.2012.06.029.
  10. ^ Marambio Group - Lopez de Bertodano Formation at Fossilworks.org
  11. ^ Seymour Island Group - Lopez de Bertodano Formation at Fossilworks.org
  12. ^ Upper Lopez de Bertodano Formation at Fossilworks.org
  13. ^ Legendre et al., 2020
  14. ^ a b 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.
  15. ^ 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.
  16. ^ a b 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.
  17. ^ Alberto L. Cione; Sergio Santillana; Soledad Gouiric-Cavalli; Carolina Acosta Hospitaleche; Javier N. Gelfo; Guillermo M. Lopez; Marcelo Reguero (2018). "Before and after the K/Pg extinction in West Antarctica: New marine fish records from Marambio (Seymour) Island". Cretaceous Research. 85: 250–265. doi:10.1016/j.cretres.2018.01.004.
  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.
  19. ^ 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
  20. ^ 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.
  21. ^ 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.
  22. ^ O'Gorman, J. P., Gasparini, Z., & Salgado, L. (2012). Postcranial morphology of Aristonectes (Plesiosauria, Elasmosauridae) from the Upper Cretaceous of Patagonia and Antarctica. Antarctic Science, 25(1), 71–82. https://doi.org/10.1017/S0954102012000673

Bibliography

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