Rodinia Supercontinent Jigsaw Puzzle
Thursday, 17. July 2008, 13:19:07
Piecing together Earth's tectonic past is an extremely tricky business. There is, however, some evidence that supercontinents have formed periodically during Earth’s history.
The supercontinent Rodinia is thought to have existed about 1000 million years ago. A quick Google Image search, however, discloses a large variety of ideas about what this Rodinia looked like. For instance Trond Torsvik wrote about his ideas on the break-up of Rodinia in an article in the journal Science of 30 may 2003, that he quite properly titled “The Rodinia Jigsaw Puzzle”.
One of the most prominent models is the SWEAT hypothesis. SWEAT stands for the southwest United States–East Antarctica. In a paper titled "Southwest U.S.–East Antarctica (SWEAT) Connection: A hypothesis“ in the journal Geology of May 1991 E. M. Moores presented what he then called a provocative hypothesis that a late Precambrian fit of western North America with the Australia-Antarctic shield region permits the extension of many features through Antarctica and into other parts of Gondwana. Although geological and isotopic data support such a fit, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China.
In a study presented in the journal Science of 11 July 2008 (A Positive Test of East Antarctica–Laurentia Juxtaposition Within the Rodinia Supercontinent) Goodge et al. provide geological, geochronological, and isotopic data from Antarctica that address a key piece in the Rodinia puzzle in order to test the SWEAT model. The map shows a general Rodinia reconstruction at ~800 to 750 Ma consistent with SWEAT. The Transarctic Mountains of Antarctica are marked in red.
One of the most distinctive elements of Laurentian crust is a belt of ~1.4-billion-year-old rapakivi granites that extends from the Fennoscandian shield in Baltica across Laurentia to the southwestern U.S. If the SWEAT model for Rodinia is correct, traces of this belt, as well as Archean and Paleoproterozoic crust that hosts it, should be evident in East Antarctica. And indeed the authors state that a.o. isotopic data from a rapakivi granite boulder in East Antarctica demonstrate these distinctive Laurentian basement belts extend into Antarctica.
Typical of Rapakivi granites (rapakivi textures) are round to oval balls with a core of kali feldspar (orthoclase) overgrown with (a rim of) plagioclase. The largest "ball" on the picture has a diameter of about 5 cm. Rapakivi is often used as monumental stone. My picture is from a local building.
The supercontinent Rodinia is thought to have existed about 1000 million years ago. A quick Google Image search, however, discloses a large variety of ideas about what this Rodinia looked like. For instance Trond Torsvik wrote about his ideas on the break-up of Rodinia in an article in the journal Science of 30 may 2003, that he quite properly titled “The Rodinia Jigsaw Puzzle”.
One of the most prominent models is the SWEAT hypothesis. SWEAT stands for the southwest United States–East Antarctica. In a paper titled "Southwest U.S.–East Antarctica (SWEAT) Connection: A hypothesis“ in the journal Geology of May 1991 E. M. Moores presented what he then called a provocative hypothesis that a late Precambrian fit of western North America with the Australia-Antarctic shield region permits the extension of many features through Antarctica and into other parts of Gondwana. Although geological and isotopic data support such a fit, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China.
In a study presented in the journal Science of 11 July 2008 (A Positive Test of East Antarctica–Laurentia Juxtaposition Within the Rodinia Supercontinent) Goodge et al. provide geological, geochronological, and isotopic data from Antarctica that address a key piece in the Rodinia puzzle in order to test the SWEAT model. The map shows a general Rodinia reconstruction at ~800 to 750 Ma consistent with SWEAT. The Transarctic Mountains of Antarctica are marked in red. One of the most distinctive elements of Laurentian crust is a belt of ~1.4-billion-year-old rapakivi granites that extends from the Fennoscandian shield in Baltica across Laurentia to the southwestern U.S. If the SWEAT model for Rodinia is correct, traces of this belt, as well as Archean and Paleoproterozoic crust that hosts it, should be evident in East Antarctica. And indeed the authors state that a.o. isotopic data from a rapakivi granite boulder in East Antarctica demonstrate these distinctive Laurentian basement belts extend into Antarctica.
Typical of Rapakivi granites (rapakivi textures) are round to oval balls with a core of kali feldspar (orthoclase) overgrown with (a rim of) plagioclase. The largest "ball" on the picture has a diameter of about 5 cm. Rapakivi is often used as monumental stone. My picture is from a local building.
WIDGETIZE
galanga # 19. July 2008, 22:24
I also enjoy the picture "from a local building". It looks like an abstract modern painting. I also imagine people who saw you taking that picture, and how they should have been surprised... There's sometimes art and surrealism in the most rigourous science.
nielsol # 20. July 2008, 06:44
Ole
nadams # 8. March 2009, 02:17
As to Rodinia; Were you aware of the fact that no one has come forward with clear (Or unclear) Evidence that Rodinia began it's breakup into continents at any PARTICULAR time, much less,700 MYA.
How does one measure WHEN granitic rock rifted and split apart.
In 'fact' if I said Rodinia began deep rifting and spreading apart beginning 180 MYA, there would be NO EVIDENCE TO THE CONTRARY. In fact the deep oceanic explorations by the geological community and the U.S. Navy that led to the "Crustal Age Map" shows the spreading of continental plates began to spread 180 MYA!
It may seem contrary to current theory, but all evidence indicates a 180 MYA beginning of the breakup. You can see the original breakup point in the Western Pacific, clear as can be.
Not only does the magnetic reversals support this but the incredible maps that pretend to present this Rodinia and it's progressions are so distorted and surreal that they boggle the mind.
You KNOW the broken Continental plates are GRANITIC and between 30 and 70 km thick and quite brittle. That is they would shatter and break, before they would BEND.
Look at any of the proported Geological maps going back in time, Try this simple task. Follow and keep track of ASIA!
Silly Putty.
Regards
Neal adams
nealadams.com
nielsol # 8. March 2009, 11:43
Pangea is the most recent supercontinent and probably reached its maximum extent about 250 million years ago. Rodinia was an earlier supercontinent of which, of course, less is known.