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Coordinates: 76°54′S 159°24′E / 76.9°S 159.4°E / -76.9; 159.4
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Mawson Formation
Stratigraphic range: Toarcian
~182–177 Ma
↓
Mawson Peak, where the main strata was recovered
TypeGeological formation
Unit ofFerrar Large Igneous Province
Sub-unitsCarapace Sandstone Member[1]
UnderliesKirkpatrick Basalt (In part)
OverliesLashly Formation
Area28.5 km²
ThicknessUp to 400 m
Lithology
PrimaryVolcaniclastic mudstone
OtherVolcaniclastic gray & blue mudstone
Location
Coordinates76°54′S 159°24′E / 76.9°S 159.4°E / -76.9; 159.4
Approximate paleocoordinates60°06′S 46°30′E / 60.1°S 46.5°E / -60.1; 46.5
RegionSouth Victoria Land
Country Antarctica
ExtentUnknow
Type section
Named forMawson Peak
Named byBallance and Watters, 1971[2]
LeToarc181/sandbox is located in Antarctica
LeToarc181/sandbox
LeToarc181/sandbox (Antarctica)

The Mawson Formation is a geological formation in Antarctica, dating to roughly between 182-177 million years ago and covering the Toarcian stages of the Jurassic Period in the Mesozoic Era.[2][3] Vertebrate remains are known from the formation.[4] The Mawson Formation if the South Victoria Land equivalent of the Karoo Large Igneous Province in South Africa (including the upper Clarens Formation desertic interbeds), as well the Lonco Trapial Formation and the Cañadón Asfalto Formation of Argentina.[1]

Geology

[edit]

The thin lacustrine interbeds of the Mawson Formation have received several names in literature, being know as either Carapace Sandstone or Carapace Formation, being a series of Freshwater environments developed during times when the Kirkpatrick Basalt stopped invading the zone.[5] The lava flow deposits of the Kirkpatrick Basalt belong to the Ferrar Large Igneous Province, developed in a linear belt along the Transantarctic Mountains, from the Weddell Sea region to North Victoria Land, covering aprox. 3,500 km in length. [6] This event was linked with the initial stages of the breakup of the Gondwanan part of Pangea, concretely with the rifting of East Antarctica and Southern Africa, developing a magmatic flow controlled by an Early Jurassic zone of extension related to a triple junction in the proto-Weddell Sea region at approximately 55°S.[7] This eruptions phase includes the Dufek Intrusion, the Ferrar Dolerite sills and dikes, extrusive rocks consisting of pyroclastic strata, and the Kirkpatrick Basalt lava flows, with a total thickness variable, but exceding 2 Km in some places.[7] This Volcanism is not limited to the Antarctica, as it was recorded also in Tasmania and New Zealand, suggesting that these area where connected back then.[8]

Paleoenvironment

[edit]
The Mawson Formation was developed in a similar way to modern Waimangu Volcanic Rift Valley of New Zealand, with Lakes Influenced by Hydrothermal vents

The Mawson Formation was described originally subdivided in two sections, that where identified as separate units. This, is due to a clear differenciation of two kinds of deposits: the so called "Mawson Tuffs", representing lithified pyroclastic material and the "Carapace sandstones", alluvial/lacustrine, both deposited in a setting defined by Ballance and Watters (1971) as composed by “shallow, northeast flowing, ephemeral streams on a subsiding alluvial plain”.[2] Beyond alluvial settings, ancient lakes, with hydrothermal influence, where developed thanks to the relationships with the overliying Kirckpatrick Basalt.[1] This deposits mark the know locally as "Mawson Time", a section of the sedimentological evolution of the Ferrar Range, where volcanic material deposited in Allan Hills and Coombs Hills, while the Carapace Sandstones hosted an alluvial plain that recovered all the volcanic detritus, being latter flooded and developing a lacustrine ecosystem.[2][1]

The Formation includes two main locations: Carapace Nunatak in South Victoria Land, representing a deposit of interbeds dominated by sandstones of fluvial to lacustrine origin.[9] The main outcrop of this location is notorious for the presence of a 37 m Hialoclastite, volcanic material accumulated, likely on a local lake of the same depth.[9] This lake layers, called "Lake Carapace", host the only relatively complete fish remains recovered in the whole formation, and was likely feed by seasonal streams that brought the volcanic materials from sources located far away of the alluvial setting.[9] The "Lake Carapace" also shows temporal exposed paleosoils, with and without roots, as well with muds cracks, indicating seasonal drougths. This lacustrine-type deposit is also found on the second main fossiliferous outcrops of the formation, being in the Queen Alexandra Range in the Central Transantarctic Mountains.[10]

Sedimentary interbeds deposited over lava flows of the Kirkpatrick Basalt during the Early Jurassic splitting of Gondwana represent unusual freshwater paleoenvironments, with hotter conditions that allow to the diversification of the microbes (Archea).[11]

According to Barrett, "...the basalt-dominated Mawson Formation and tholeiitic flows (Kirkpatrick Basalt)...are included in the Ferrar Group." The Mawson Formation consists of diamictites, explosion breccias, and lahar flows, evidence of magma entering water-saturated sediments. The Kirkpatrick Basalts (180 Ma) have interbedded lake sediments with plant and fish fossils.[12][13]

Fossil content

[edit]

There abundant Fossils of microorganisms, as members of the group Archea and other who take advantage of the hydrothermal activity[11][5][14]

Crustacea

[edit]
Genus Species Location Stratigraphic position Material Notes Images

Lioestheria[15]

  • Lioestheria doumanii
  • Blizzard Heights
  • Brimstone Peak

All the Sections

Carapaces

A Freshwater member of Diplostraca (Spinicaudatan). Correlated with coeval East African and Indian lioestheriids

Carapacestheria[16]

  • Carapacestheria disgregaris
  • Carapacestheria balli
  • Carapace Nunatak
  • Mackay Glacier

All the Sections

Carapaces

A Freshwater member of Diplostraca (Spinicaudatan). Related to the modern Cyzicus mexicanus and recovered in siliclastic interbeds, representing the most common fossil animal in the unit.[11][5]

Lepidurus[17][18]

  • Lepidurus stormbergensis
  • Carapace Nunatak

All the Sections

Complete Specimens

A Freshwater member of Notostraca. Represented by specimens much bigger than forms (20 mm compared with smaller 10-12 mm breadth) from South Africa

Extant Specimen of the Genus

Protamhisopus[18]

  • Protamhisopus wianamatthensis
  • Carapace Nunatak

All the Sections

Complete Specimens

A Freshwater member of Isopoda. Shows affinities with specimens from the Upper Triassic of New South Wales

Syncarida[19]

  • Syncarida Inderminate
  • Carapace Nunatak

All the Sections

Complete Specimens

A Freshwater member of Syncarida.

Insects

[edit]

Fossil insect wings not described to the genus level are known from the formation.[20]

Genus Species Location Stratigraphic position Material Notes Images

Caraphlebia[21]

Caraphlebia antartica

Carapace Nunatak

Middle Section

Wings

A dragonfly of the family Selenothemidae. Was found to be related with the genus Liassophlebia, but the hind wing has severalweak antenodals in addition to the two strong, primary ones.

Ephemeroptera[22]

Indeterminate

Carapace Nunatak

Middle Section

abdominal segments and paired cerci

Indeterminate Mayfly nymphs

Coleoptera[22]

Indeterminate

Carapace Nunatak

Middle Section

Charred fragmentary beetle elytron

A Beetle with resemblance with archostematids (Schizophoridae, Catiniidae) and some adephagian beetles (Hygrobiidae, Amphizoidae) that have such elytra

Ostracoda

[edit]
Genus Species Location Stratigraphic position Material Notes

Darwinula[18]

Darwinula sp.

  • Carapace Nunatak
  • Mackay Glacier

All the Sections

Valves

Common Early Jurassic Freshwater ostracod. The specimens of this genus cannot be identified to species level, yet bear resemblance with specimens from the same age of South Africa.[11][5]

Fish

[edit]
Genus Species Location Stratigraphic position Material Notes

Oreochima[23]

Oreochima ellioti

  • Storm Peak
  • Carapace Nunatak

Middle Section

  • Various specimens
  • Isolated Scales

A Freshwater archaeomaenid. One of the few fishes from this family recovered outside Australia, represents a genus that likely lived linked with Hydrothermal settings and was very proliferous on the local lacustrine systems. Represents a rather small genus.[23]

Pholidophoriformes[23]

Indeterminate

  • Storm Peak

Middle Section

  • One patch of scales

A Freshwater member of Pholidophoriformes.

Fungi

[edit]
Genus Species Location Stratigraphic position Material Notes Images

Ceratocystis?[24]

Indeterminate

Carapace Nunatak

Middle Section

Hyphae

Parasitic Fungus, probably of the family Ceratocystidaceae. Infestation traces and fungal parasitic interaction on several plants. Morphology and colonization pattern of the fungus are, however, remarkably similar to those of some extant sap-stain fungi, including the dematiaceous hyphomycete Verticicladiella wageneri.[24]

Fungi[25]

Indeterminate

Carapace Nunatak

Middle Section

Hyphae

Parasitic Fungus of uncertain relationships. Infestation traces of thick-walled hypae where recovered on Brachyphyllum-type foliage locally

Plants

[edit]

One of the best preserved fossil flora of the Antarctic. Nearly all the floral remains where recovered from Siliclastic interbeds, being mostly of them Silidified.[26]

Genus Species Location Material Notes Images

Marchantites[27]

Marchantites mawsonii

Carapace Nunantak

Isolated Thalli

A liverwort of the family Marchantiales. Some specimens where reworked from the Hanson Formation to the Mawson Formation. This liverwort is related to modern humid-environment genera.

Example of extant relative of Marchantites, Marchantia

Cladophlebis[27]

Cladophlebis oblonga

Carapace Nunantak

Isolated Pinnae

A Fern of the family Osmundaceae. Some specimens where reworked from the Hanson Formation to the Mawson Formation. Linked with the tree fern genus Osmundacaulis

Polyphacelus[28][29]

Polyphacelus stormensis

Storm Peak

Silicified rachides[28]

A Polypodiopsidan of the family Dipteridaceae. Closely related to Clathropteris meniscoides.

Zamites[30][31]

Indeterminate

Carapace Nunatak

Leaflets

Spermatophyta incertae sedis[11][5]

Example of Zamites specimen

Otozamites[30][31]

Otozamites antarcticus

Carapace Nunatak

Leaflets

A cycadophyte of the family Bennettitales.

Example of Otozamites specimen

Protocupressinoxylon[32]

Protocupressinoxylon sp.

Coombs Hills

Storm Peak

Isolated tree stump

A member of the family Cupressaceae.

Elatocladus[27]

Elatocladus confertus

Carapace Nunatak

Branched Shoots

A member of the family Cupressaceae. Related to specimens found in the Middle Jurassic of Hope Bay, Graham Land. Probably represent belong to the Conifer Austrohamia from the Lower Jurassic of Argentina and China.

Nothodacrium[33]

Nothodacrium warreni

Carapace Nunatak

Storm Peak

Cutinised and fertile material

A member of the family Podocarpaceae. A genus with Resemblance with the extant Dacrydium.[33]

Example of extant Dacrydium specimens, likely closely related with Nothodacrium warreni

Masculostrobus[33][30][31]

Masculostrobus warrenii

Carapace Nunatak

Single cone

A member of the family Podocarpaceae. Originally assigned to the Cheirolepidiaceae, was latter suggested to share affinities with the Podocarpaceae. Likely represents the cone of the same conifer that produced the Nothodacrium foliage, as resembles cones from extant Microcachrys and Dacrydium .[33]

Agathoxylon[34]

Agathoxylon sp.

Carapace Nunantak

Fossil Wood

Affinities with Araucariaceae or Cheirolepidiaceae inside Pinales.

Brachyoxylon[34]

Brachyoxylon sp.

Carapace Nunantak

Fossil Wood

Affinities with Araucariaceae or Cheirolepidiaceae inside Pinales.

Brachyphyllum[30][31][35]

Indeterminate

Carapace Nunatak

Several isolated Branched Shoots

A member of the family Cheirolepidiaceae. Associated with Classostrobus cones.[35]

Classostrobus[35]

Classostrobus elliotii

Carapace Nunatak

Five permineralized pollen cones

A member of the Cheirolepidiaceae. More than five Brachyphyllum-type leaves where found in close association with these cones.[35]

Pagiophyllum[30][31]

Indeterminate

Carapace Nunantak

Single Branched Shoot

A member of the Pinales of the family Araucariaceae. Representative of the presence of arboreal to arbustive flora.

Example of Pagiophyllum specimen

Chimaerostrobus[36]

Chimaerostrobus minutus

Carapace Nunatak

Single Pollen Cone

A conifer pollen cone of uncertain Relationships. Chimaerostrobus is reminiscent of extant Araucariaceae and several extinct taxa such as Kobalostrobus and Voltziales.[36]

See also

[edit]

References

[edit]
  1. ^ a b c d Ross, P. S.; White, J. D.; McClintock, M. (2008). "Geological evolution of the Coombs–Allan Hills area, Ferrar large igneous province, Antarctica: Debris avalanches, mafic pyroclastic density currents, phreatocauldrons". Journal of Volcanology and Geothermal Research. 172 (2): 38–60. Retrieved 24 March 2022.
  2. ^ a b c d Ballance, P.F.; Watters, W.A. (1971). "The Mawson Diamictite and the Carapace Sandstone, formations of the Ferrar Group at Allan Hills and Carapace Nunatak, Victoria Land, Antarctica". N. Z. J. Geol. Geophys. 14: 512–527. Retrieved 7 March 2022.
  3. ^ Burgess, S.D.; Bowring, S.A.; Fleming, T.H.; Elliot, D.H. (2015). "High-precision geochronology links the Ferrar large igneous province with early Jurassic ocean anoxia and biotic crisis". Earth Planet. Sci. Lett. 415 (1): 90–99. Retrieved 7 March 2022.
  4. ^ Elliot, D.H. (2013). "The geological and tectonic evolution of the Transantarctic Mountains: a review". Geol. Soc. Lond. Spec. Publ. 381 (2): 7–35. Retrieved 7 March 2022.
  5. ^ a b c d e Stigall, A. L.; Babcock, L. E.; Briggs, D. E. G.; Leslie, S. A. (2008). "Taphonomy of Lacustrine Interbeds in the Kirkpatrick Basalt (Jurassic), Antarctica". PALAIOS. 23 (6): 344–355. doi:10.2110/palo.2007.p07-029r. Retrieved 7 March 2022.
  6. ^ Fleming, T.H.; Elliot, D.H.; Foland, K.A.; Heimann, A. (1997). "40Ar/39Ar geo chronology of Ferrar Dolerite sills from the Transantarctic Mountains, Antarctica: Implications for the age and origin of the Ferrar magmatic province". Geological Society of America Bulletin. 109 (2): 533–546. Retrieved 9 March 2022.
  7. ^ a b Elliot, D.H.; Fleming, TH (2004). "Occurrence and dispersal of magmas in the Jurassic Ferrar Large Igneous Province, Antarctica". Gondwana Research. 7 (8): 223–237. Retrieved 9 March 2022.
  8. ^ Mortimer, N.; Adams, C.J.; Graham, I.J.; Oliver, P.J.; Palmer, K.; Parkinson, D.; Raine, J.I. (1995). "Ferrar magmatic province rocks discovered in New Zealand: Implications for Mesozoic Gondwana geology". Geology. 23 (1): 185–188. Retrieved 9 March 2022.
  9. ^ a b c Bradshaw, M.A. (1987). "Additional field interpretation of the Jurassic sequence at Carapace Nunatak and Coombs Hills, south Victoria Land Antarctica". N. Z. J. Geol. Geophys. 30 (1): 37–49. Retrieved 7 March 2022.
  10. ^ Tasch, P.; Gafford, E.L. (1984). "Central Transantarctic Mountains nonmarine deposits". Antarctic Research Series. 36 (6): 75–96. Retrieved 9 March 2022.
  11. ^ a b c d e Babcock, LE; Leslie, SA; Elliot, DH; Stigall, AL (2006). "The "Preservation Paradox": microbes as a key to exceptional fossil preservation in the Kirkpatrick Basalt (Jurassic), Antarctica" (PDF). The Sedimentary Record. 4 (2): 4–8. Retrieved 7 March 2022.
  12. ^ Barrett, P.J. (1991). Tingey, Robert (ed.). The Devonian to Jurassic Beacon Supergroup of the Transantarctic Mountains and correlatives in other parts of Antarctica, in The Geology of Antarctica. Oxford: Clarendon Press. pp. 122–123, 129, 145. ISBN 0198544677.
  13. ^ Tingey, R.J. (1991). Tingey, Robert (ed.). Mesozoic tholeiitic igneous rocks in Antarctica: the Ferrar (Super) Group and related rocks, in The Geology of Antarctica. Oxford: Clarendon Press. pp. 159–160. ISBN 0198544677.
  14. ^ Norris, G. (1965). "Triassic and Jurassic miospores and acritarchs from the Beacon and Ferrar groups, Victoria Land, Antarctica". New Zealand journal of geology and geophysics. 8 (2): 236–277. Retrieved 7 March 2022.
  15. ^ Elliot, David H.; Tasch, Paul (1967). "Lioestheriid Conchostracans: A New Jurassic Locality and Regional and Gondwana Correlations". Journal of Paleontology. 41 (6): 1561–1563. Retrieved 9 March 2022.
  16. ^ Yanbin, S. (1994). "Jurassic conchostracans from Carapace Nunatak, southern Victoria Land, Antarctica" (PDF). Antarctic Science. 6 (1): 105–113. Retrieved 7 March 2022.
  17. ^ Haughton, S.H. (1924). "The fauna and stratigraphy of the Stormberg Series". Annals of the South Africa Museum. 12 (2): 323–495. Retrieved 8 March 2022.
  18. ^ a b c Bail, H.W.; Borns, H.W.; Hau, B.A.; Brooks, H.K.; Carpekier, E.M.; Dblbvoryas, T. (1979). "Biota, age, and significance of lake deposits. Carapace Nunatak, Victoria Land, Antarctica". Fourth International Gondwana Symposium Calcutta, India. 3 (1): 166–175. Retrieved 8 March 2022.
  19. ^ Borns, H.W.; Ball, H.W (1972). "Mawson tillite, Victoria Land, east Antarctica: reinvestigation continued" (PDF). Journal of Glaciology. 4 (32): 173–195. Retrieved 8 March 2022.
  20. ^ Bomfleur, B.; Schneider, J. W.; Schöner, R.; Viereck-Götte, L.; Kerp, H. (2011). "Fossil sites in the continental Victoria and Ferrar groups (Triassic-Jurassic) of north Victoria Land, Antarctica". Polarforschung. 80 (2): 88–99. Retrieved 15 November 2021.
  21. ^ Carpenter, F. M. (1969). "Fossil insects from Antarctica". Harvard University. 76 (3): 418–425. Retrieved 8 March 2022.
  22. ^ a b Tasch, P. (1973). "Jurassic beetle from southern Victoria Land, Antarctica". 47 (2): 590–592. Retrieved 8 March 2022. {{cite journal}}: Cite journal requires |journal= (help)
  23. ^ a b c Schaeffer, Bobb (1972). "A Jurassic Fish from Antarctica" (PDF). American Museum of Natural History. 2495 (2): 1–17. Retrieved 7 March 2022.
  24. ^ a b Harper, C. J.; Bomfleur, B.; Decombeix, A. L.; Taylor, E. L.; Taylor, T. N.; Krings, M. (2012). "Tylosis formation and fungal interactions in an Early Jurassic conifer from northern Victoria Land, Antarctica". Review of Palaeobotany and Palynology. 175 (4): 25–31. Retrieved 8 March 2022.
  25. ^ Harper, C. J.; Taylor, T. N.; Krings, M.; Taylor, E. L. (2016). "Structurally preserved fungi from Antarctica: diversity and interactions in late Palaeozoic and Mesozoic polar forest ecosystems" (PDF). Antarctic Science. 28 (3): 153–173.
  26. ^ Bomfleur, B.; Schneider, J.; Schöner, R.; Viereck-Götte, L.; Kerp, H.; Cooper, A. K.; Raymond, C. R. (2007). "Exceptionally well-preserved Triassic and Early Jurassic floras from North Victoria Land, Antarctica". Proceedings of the 10th International Symposium on Antarctic Earth Sciences. 34 (1): 1–4. Retrieved 8 March 2022.
  27. ^ a b c Plumstead, E.P (1964). "Palaeobotany of Antarctica". Proceedings of the 1st International Symposium on Antarctic Geology, Cape Town. Amsterdam, North Holland. 1 (2): 637–654.
  28. ^ a b Yao, X.; Taylor, T. N.; Taylor, E. L. (1991). "Silicified dipterid ferns from the Jurassic of Antarctica". Review of Palaeobotany and Palynology. 67 (3–4): 353–362. Retrieved 8 March 2022.
  29. ^ Bomfleur, B.; Kerp, H. (2010). "The first record of the dipterid fern leaf Clathropteris Brongniart from Antarctica and its relation to Polyphacelus stormensis Yao, Taylor et Taylor nov. emend". Review of Palaeobotany and Palynology. 160 (3–4): 143–153. doi:10.1016/j.revpalbo.2010.02.003. Retrieved 15 November 2021.
  30. ^ a b c d e Plumstead, E. P. (1955). "Fossil Floras of Antarctica, with an appendix on Antarctic fossil wood by Richard Krüusel". Trans–Antarctic Expedition. 9 (1): 1–154.
  31. ^ a b c d e Townrow, J. A. (1967). "Fossil plants from Allan and Carapace Nunataks, and from the Upper Mill and Shackleton Glaciers, Antarctica". New Zealand Journal of Geology and Geophysics. 10 (2): 456–473. Retrieved 8 March 2022.
  32. ^ Garland, M. J.; Bannister, J. M.; Lee, D. E.; White, J. D. L. (2007). "A coniferous tree stump of late Early Jurassic age from the Ferrar Basalt, Coombs Hills, southern Victoria Land, Antarctica". New Zealand Journal of Geology and Geophysics. 50 (3): 263–269. doi:10.1080/00288300709509836. Retrieved 8 March 2022.
  33. ^ a b c d Townrow, (). . In (Vol. , pp. )., J. A. (1967). "Conifer from the Jurassic of east Antarctica" (PDF). Papers and Proceedings of the Royal Society of Tasmania. 101 (2): 137–149. Retrieved 8 March 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  34. ^ a b Toumoulin Anne-Laure DecombeixAnne-Laure DecombeixCarla J. HarperCarla J. HarperShow all 5 authorsEdith TaylorEdith Taylor, Agathe; Decombeix, Anne-Laure; J. Harper, Carla; Taylor, Edith; Serbet, Rudolph (2016). "Early Jurassic permineralised woods from Carapace Nunatak, South Victoria Land, Antarctica: affinities and paleoenvironmental implications". Palynological Congress and X International Organisation of Paleobotany conference. 15 (1): 229. Retrieved 24 October 2021.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  35. ^ a b c d Hieger, T. J.; Serbet, R.; Harper, C. J.; Taylor, E. L.; Taylor, T. N.; Gulbranson, E. L. (2015). "Cheirolepidiaceous diversity: An anatomically preserved pollen cone from the Lower Jurassic of southern Victoria Land, Antarctica". Review of Palaeobotany and Palynology. 220 (3): 78–87. Retrieved 8 March 2022.
  36. ^ a b Atkinson, B. A.; Serbet, R.; Hieger, T. J.; Taylor, E. L. (2018). "Additional evidence for the Mesozoic diversification of conifers: Pollen cone of Chimaerostrobus minutus gen. et sp. nov.(Coniferales), from the Lower Jurassic of Antarctica". Review of Palaeobotany and Palynology. 257 (3): 77–84. Retrieved 8 March 2022.

Category:Geologic formations of Antarctica Category:Jurassic System of Antarctica Category:Pliensbachian Stage Category:Toarcian Stage Category:Mudstone formations Category:Tuff formations Category:Lacustrine deposits Category:Paleontology in Antarctica

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