Minaret Formation

The Minaret Formation is a Late Cambrian limestone formation of the Heritage Group of Antarctica. The age of the formation is established to be Guzhangian to Cambrian Stage 10 (or Merioneth to Dresbachian in the regional stratigraphy), dated at ranging from 500 to 488 Ma.[1]

Minaret Formation Stratigraphic range: Guzhangian-Cambrian Stage 10 (Merioneth-Dresbachian) ~500–488 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Minaret Formation (Antarctica)
Type	Geological formation
Unit of	Heritage Group
Underlies	Crashsite Group  Howard Nunataks Formation
Overlies	Liberty Hills & Springer Peak Formations
Thickness	Up to 600 m (2,000 ft)
Lithology
Primary	Limestone
Location
Coordinates	79.4°S 84.8°W
Region	Ellsworth Land
Country	Antarctica
Extent	Ellsworth Mountains, Yochelson Ridge & Heritage Range
Paleogeography of the Cambrian with the supercontinent Pannotia and Antarctica south of the paleo-equator

The formation has provided the first known Late Cambrian archaeocyathid,[2] and Knightoconus antarcticus, an ancestor to the cephalopods.[3]

Description

The Minaret Formation forms a discontinuous limestone unit exposed from Webers Peaks in the northern Heritage Range to the Independence Hills in Horseshoe Valley of the Ellsworth Mountains. At Mount Rosenthal, at the head of Horseshoe Valley, the Minaret Formation is formed predominantly of white to pale grey micritic limestone with thin, discrete interbeds of oolitic and oncolithic grainstones.[4]

The Minaret Formation is the uppermost formation of the Heritage Group, overlying the Liberty Hills and Springer Peak Formations. The formation is overlain by the Howard Nunataks Formation of the Crashsite Group.[5] The formation reaches a thickness of 600 metres (2,000 ft) in the south of its extent.[6] The formation ranges from shallow to deep marine.[7] The Minaret fauna contains the first known Late Cambrian archaeocyathid.[2] During the final stages of Gondwanian deformation, structureless and stratified post-cleavage breccia bodies formed in the carbonate lithologies of the Minaret Formation, due to cave-like dissolution processes and contemporaneous low temperature hydrothermal activity.[8]

Fossil content

The reefal limestones of the formation have provided fossils:[1]

• Antarcticocyathus webersi[9]
• Gastropods
  • Strepsodiscus splettstoesseri[10]
• Conodonts
  • Furnishina furnishi[11]
  • F. quadrata[12]
  • F. ?asymmetrica[11]
  • Proacodus tenuis[12]
  • Phakelodus sp.[12]
  • Westergaardodina bicuspidata[12]
  • W. moessebergensis[13]
  • W. tricuspidata[13]
• Tergomya
  • Aremellia batteni[10]
  • Ellsworthoconus andersoni[10]
  • Kirengella pyramidalis[10]
  • Knightoconus antarcticus[10]
  • Proconus incertis[10]
  • Proplina rutfordi[10]
• Rostroconchia
  • Apoptopegma craddocki[10]
  • Cosminoconella runnegari[10]
• Paragastropoda
  • Matherella antarctica[10]
  • Ribeiria australiensis[10]
  • Scaevogyra thompsoni[10]
  • ?Kobayashiella heritagensis[10]

See also

• List of fossiliferous stratigraphic units in Antarctica
• Geology of Antarctica
• Shackleton Limestone, Cambrian fossiliferous limestone of Antarctica

References

1. Minaret Formation at Fossilworks.org
2. Webers & Splettstoesser, 2007, p.5
3. Yochelson et al., 1973
4. Curtis & Lomas, 1999, p.66
5. Curtis & Lomas, 1999, p.65
6. Webers & Splettstoesser, 2007, p.3
7. Curtis & Lomas, 1999, p.71
8. Curtis & Lomas, 1999, p.64
9. Debrenne et al., 1984
10. Webers et al., 1992
11. Buggisch et al., 1992, p.170
12. Buggisch et al., 1992, p.172
13. Buggisch et al., 1992, p.173

Bibliography

• Webers, G.F., and J.F. Splettstoesser. 2007. Review of the geology and paleontology of the Ellsworth Mountains, Antarctica. USGS and The National Academies; USGS OF-2007-1047, Short Research Paper 107. 1–5. Accessed 2020-07-11.
• Curtis, Michael L., and Simon A. Lomas. 1999. Late Cambrian stratigraphy of the Heritage Range, Ellsworth Mountains: implications for basin evolution. Antarctic Science 11. 63–77. Accessed 2020-07-11.
• Buggisch, Werner; Gerald F. Webers; John E. Repetski, and Linda Glenister. 1992. Cambrian conodonts from the Springer Peak and Minaret Formations, Ellsworth Mountains, West Antarctica. Geological Society of America Memoir 170. 169–179. Accessed 2020-07-11.
• Webers, G.F.; J. Pojeta, and E.L. Yochelson. 1992. Cambrian Mollusca from the Minaret Formation, Ellsworth Mountains, West Antarctica. Geological Society of America Memoir 170. 181–248.
• Debrenne, F.; A. Y. Rozanov, and G. F. Webers. 1984. Upper Cambrian archaeocyatha from Antarctica. Geological Magazine 121. 291–299.
• Yochelson, E.L.; R.H. Flower, and G.F. Webers. 1973. The bearing of the new Late Cambrian monoplacophoran genus Knightoconus upon the origin of the Cephalopoda. Lethaia 6. 275–309. doi:10.1111/j.1502-3931.1973.tb01199.x