Pannotia was centred on the South Pole, hence its name.
Pannotia (from Greek:pan-, "all",-nótos, "south"; meaning "all southern land"), also known as theVendian supercontinent,Greater Gondwana, and thePan-African supercontinent, was a relatively short-livedNeoproterozoicsupercontinent that formed at the end of thePrecambrian during thePan-African orogeny (650–500Ma), during theCryogenian period and broke apart 560 Ma with the opening of theIapetus Ocean, in the lateEdiacaran and earlyCambrian.[1]Pannotia formed whenLaurentia was located adjacent to the two major South Americancratons,Amazonia andRío de la Plata. The opening of theIapetus Ocean separated Laurentia fromBaltica, Amazonia, and Río de la Plata.[2] A 2022 paper argues that Pannotia never fully existed, reinterpreting thegeochronological evidence: "the supposed landmass had begun to break up well before it was fully assembled".[3] However, the assembly of the next supercontinentPangaea is well established.
J. D. A. Piper was probably the first to propose a Proterozoic supercontinent precedingPangaea, today known asRodinia.[4][5] At that time he simply referred to it as "the Proterozoic super-continent",[6] but much later he named this "symmetrical crescent-shaped analogue of Pangaea" 'Palaeopangaea' and in 2000 he still insisted that there is neither a need nor any evidences for Rodinia or its daughter supercontinent Pannotia or a series of other proposed supercontinents sinceArchaean times.[7]
The existence of a late Proterozoic supercontinent, much different from Pangaea, was first proposed byMcWilliams 1981 based onpaleomagnetic data, and the break-up of this supercontinent around 625–550 Ma was documented byBond, Nickeson & Kominz 1984.[8] The reconstruction of Bond et al. is virtually identical to that ofDalziel 1997 and others.[9]
Another term for the supercontinent that is thought to have existed at the end of Neoproterozoic time is "Greater Gondwanaland", suggested byStern 1994. This term recognizes that the supercontinent ofGondwana, which formed at the end of the Neoproterozoic, was once part of the much larger Neoproterozoic supercontinent.[10]
Pannotia was named byPowell 1995,[11] based on the term "Pannotios" originally proposed byStump 1987 for "the cycle of tectonic activity common to the Gondwana continents that resulted in the formation of the supercontinent."[12]Young 1995 proposed renaming the older Proterozoic supercontinent (now known as Rodinia) "Kanatia", theSt. Lawrence Iroquoian word from which the name Canada is derived, while keeping the name Rodinia for the latter Neoproterozoic supercontinent (now known as Pannotia).[13] Powell, however, objected to this renaming and instead proposed Stump's term for the latter supercontinent.
An artist's impression of Pannotia, about 600 million years ago, in theEdiacaran period
Pannotia 545 Ma, view centred on the South Pole, afterDalziel 1997[14]
The formation of Pannotia began during thePan-African orogeny when theCongo Craton was lodged between the northern and southern halves of the previous supercontinentRodinia some 750 Ma. The peak in this mountain building event was around 640–610 Ma, but these continental collisions may have continued into the early Cambrian some 530 Ma. The formation of Pannotia was the result of Rodinia turning itself inside out.[15]
When Pannotia had formed, Africa was located at the centre surrounded by the rest of Gondwana: South America, Arabia, Madagascar, India, Antarctica, and Australia. Laurentia, which 'escaped' out of Rodinia,Baltica, andSiberia kept the relative positions they had in Rodinia. TheCathaysian andCimmerian terranes (continental blocks of southern Asia) were located along the northern margins of east Gondwana. TheAvalonian-Cadomian terranes (later to become central Europe, Britain, the North American east coast, and Yucatán) were located along the active northern margins of western Gondwana. Thisorogeny probably extended north into theUralian margin of Baltica.[15]
Pannotia formed bysubduction of exterior oceans (a mechanism called extroversion)[16] over ageoid low, whereas Pangaea formed by subduction of interior oceans (introversion) over a geoid high[17] perhaps caused bysuperplumes andslab avalanche events.[18]The oceanic crust subducted by Pannotia formed within theMirovia superocean that surrounded Rodinia before its 830–750 Ma break-up and were accreted during the late Proterozoicorogenies that resulted from the assembly of Pannotia.[19]
One of the major of these orogenies was the collision between eastern and western Gondwana or theEast African Orogeny.[20] TheTrans-Saharan Belt in West Africa is the result of the collision between theEast Saharan Shield and theWest African Craton when 1200–710 Ma volcanic and arc-related rocks were accreted to the margin of this craton.[19]Between 600 and 500 Ma, two Brazilian interior orogens were highly deformed and metamorphosed between a series of colliding cratons:Amazonia, West Africa-São Luís, andSão Francisco-Congo-Kasai. The material that accreted included, 950–850 Ma,mafic meta-igneous complexes and younger arc-related rocks.[19]
Pannotia formed as Proto-Laurasia was added to Gondwana c. 600 Ma (left) and broke up 550 Ma (right) when Laurasia broke apart. View centred on the South Pole.
The break-up of Pannotia was accompanied by sea level rise, dramatic changes in climate and ocean water chemistry, andrapid metazoan diversification.[20]Bond, Nickeson & Kominz 1984 found Neoproterozoicpassive margin sequences worldwide—the first indication of a Late Neoproterozoic supercontinent but also the traces of its demise.[21]
The Iapetus Ocean started to open while Pannotia was being assembled, 200 Ma after the break-up of Rodinia. This opening of the Iapetus and other Cambrian seas coincided with the first steps in the evolution of soft-bodied metazoans, and also made a myriad of habitats available for them; this led to the so-called Cambrian explosion, the rapid evolution ofskeletalized metazoans.[22]
Trilobites originated in the Neoproterozoic and began to diversify before the break-up of Pannotia 600–550 Ma, as evidenced by their ubiquitous presence in the fossil record, and the lack ofvicariance patterns in their lineage.[21]
^For a more detailed description of the concept(s) of the supercontinent cycle see:Nance, Murphy & Santosh 2014, Indications of pre-Pangean supercontinents, pp. 6, 8
^Piper 1976, Geological and Geophysical implications, p. 478
Bond, G. C.; Nickeson, P. A.; Kominz, M. A. (1984). "Breakup of a supercontinent between 625 Ma and 555 Ma: new evidence and implications for continental histories".Earth and Planetary Science Letters.70 (2):325–45.Bibcode:1984E&PSL..70..325B.doi:10.1016/0012-821X(84)90017-7.
McWilliams, M. O. (1981). "Palaeomagnetism and Precambrian tectonic evolution of Gondwana". In Kröner, A. (ed.).Precambrian Plate Tectonics. Developments in Precambrian Geology. Vol. 4. pp. 649–87.doi:10.1016/S0166-2635(08)70031-8.ISBN978-0-08-086903-2.
Powell, C. McA. (1995). "Are Neoproterozoic glacial deposits preserved on the margins of Laurentia related to the fragmentation of two supercontinents? Comment".Geology.23 (11):1053–55.doi:10.1130/0091-7613(1995)023<1053:ANGDPO>2.3.CO;2.
Stump, E. (1987). "Construction of the Pacific margin of Gondwana during the Pannotios cycle". In McKenzie, G. D. (ed.).Gondwana Six: Structure, tectonics and geophysics. American Geophysical Union Monograph. Vol. 40. pp. 77–87.Bibcode:1987GMS....40...77S.doi:10.1029/GM040p0077.ISBN978-1-118-66448-3.
