Mistaken Point Formation
Stratigraphic range: (Ediacaran)
TypeFormation
Unit ofConception Group[1]
UnderliesTrepassey Formation[2]
OverliesDrook Formation[2]
Location
Region Newfoundland
Country Canada

Outcrop occurrence of the Mistaken Point formation in southeast Newfoundland

The Mistaken Point Formation[3] is a geologic formation in Newfoundland and Labrador. It is recognized as a Lagerstätte preserving fossils dating back to the Ediacaran period. It contains a stratum dated to 565 ± 3 million years ago.

Geology

Mistaken Point Formation includes many fine ash-beds, which are a good source of zircons used in the uranium-lead method of radiometric dating, allowing the site to be confidently dated to approximately 565 million years old.

These fine-grained volcanic ash beds also preserve finely detailed fossils.[4][5]

Fossils

cone shaped organism Thectardis

Mistaken Point contains some of the oldest ediacaran biota in an Avalon-type assemblage. They are commonly categorized as Spindle-shaped (Fractofusus), Frond-shaped (Charniodiscus), or Bush-like / Radiating (Bradgatia) in form. Spindles are the most common fossils in the assemblage. Other forms do exist, such as the conical Thectardis.

Some of the forms here appear to survive until the extinction of the Ediacaran biota at the base of the Cambrian. The evolutionary history of these forms is unknown, though hypotheses exist.[6]

comb shaped organism Pectinifrons

Discovery of Ediacaran fossils in the Avalon Peninsula

In the summer of 1967, Shiva Balak Misra, an Indian graduate student (1966–69) at Newfoundland's Memorial University discovered a rich assemblage of imprints of soft bodied organisms on the surface of large rock slabs, while mapping the Conception Group of Avalon Peninsula of Newfoundland near Cape Race, at a place called Mistaken Point.[7]

These unusual impressions of previously unknown soft-bodied sea animals on the surfaces of argillites (mudstone) included coelenterates and other metazoa of the Ediacarian period, 575 to 560 million years ago.[8] These fossils are records of the oldest known complex life forms that existed anywhere on Earth.[8] Misra was the first to prepare and present a systematic geological map of the region, to classify and describe the rock sequence of the area and to work out the depositional history of the rocks.

The description of the fossil assemblage together with their mode of occurrence, the cause of sudden death, ecological conditions and chronological position form part of Misra's detailed thesis submitted for the degree of Master of Science. The discovery was reported in a 1968 letter to Nature.[9] Misra described the Mistaken Point fauna in detail in 1969, in a paper published in the Bulletin of the Geological Society of America.[10] He sorted the fossil assemblage into five groups, namely spindle-shaped, leaf-shaped, round lobate, dendrite like, and radiating. Each group was defined in terms of distribution and form, sub-categories and biological affinity.[7]

The geological environment of the fossil-bearing rocks and the ecology of the animals that lived and died in the Conception Sea were described by Misra in two of his subsequent papers published in the Bulletin of the Geological Society of America in 1971[11] and in the Journal of the Geological Society of India in 1981.[4] Mistaken Point Ecological Reserve is a 5.7-square kilometer area of the coast that protects the fossils.[8]

The sudden appearance of Ediacaran soft bodied organisms in the Mistaken Point assemblage has been called the 'Ediacaran Explosion' or 'Avalon Explosion' [12]

See also

References

  • Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.
  1. ↑ A.G. Liu; D. McIlroy (September 2014). "Horizontal Surface Traces from the Fermeuse Formation, Ferryland (Newfoundland, Canada), and their Place within the Late Ediacaran Ichnological Revolution" (PDF). Geological Association of Canada - Special Paper (9).
  2. 1 2 http://geoatlas.gov.nl.ca/Default.htm
  3. ↑ Williams, H.; King, A.F (1979). Trepassey map area, Newfoundland (Report). Geological Survey of Canada.
  4. 1 2 Misra, S.B. (August 1981). "Depositional Environment of the Late Precambrian Fossil-Bearing rocks of Southeastern Newfoundland, Canada". Journal of Geological Society of India. 22 (8).
  5. ↑ Erwin, Douglas (2008). "Wonderful Ediacarans, Wonderful Cnidarians?". Evolution & Development. 10 (3): 263–4. doi:10.1111/j.1525-142X.2008.00234.x. PMID 18460087. S2CID 205674433.
  6. ↑ Misra, S.B. (2010). "ORIGIN AND GROWTH OF THE EDIACARAN FAUNA AT MISTAKEN POINT, NEWFOUNDLAND, CANADA: A HYPOTHESIS". Journal of the Palaeontological Society of India. 55 (2): 177–182.
  7. 1 2 "Mistaken Point, Newfoundland". www.ucmp.berkeley.edu. Retrieved 2017-07-16.
  8. 1 2 3 "Mistaken Point Ecological Reserve". Newfoundland and Labrador, Dept. of Environment and Conservation.
  9. ↑ Anderson, M. M.; Misra, S. B. (16 November 1968). "Fossils found in pre-Cambrian Conception Group of southeastern Newfoundland". Nature. 220 (5168): 680–681. Bibcode:1968Natur.220..680A. doi:10.1038/220680a0. S2CID 4170629.
  10. ↑ Misra, S.B. (November 1969). "Late Precambrian(?) fossils from southeastern Newfoundland". Geological Society of America Bulletin. 80 (11): 2133–2140. doi:10.1130/0016-7606(1969)80[2133:LPFFSN]2.0.CO;2.
  11. ↑ Misra, S.B. (April 1971). "Stratigraphy and Depositional History of Late Precambrian Coelenterate-Bearing Rocks, Southeastern Newfoundland". Geological Society of America Bulletin. 82 (4): 979–988. Bibcode:1971GSAB...82..979M. doi:10.1130/0016-7606(1971)82[979:SADHOL]2.0.CO;2.
  12. ↑ Shen, Bing; Dong, Lin; Xiao, Shuhai; Kowalewski, Michal (2008). "The Avalon Explosion: Evolution of Ediacara Morphospace". Science. 319 (5859): 81–84. Bibcode:2008Sci...319...81S. doi:10.1126/science.1150279. PMID 18174439. S2CID 206509488.
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