Dataset may resolve questions about the configuration of supercontinent Rodinia

October 29, 2018 by Steve Carr, University of New Mexico
Credit: University of New Mexico

A new paper recently released in Geology by researchers Jacob Mulder, Karl Karlstrom, and other Australian colleagues provides a new dataset that may resolve the more than three decades-long debate about which continents were adjacent to southwestern USA within the 1 billion year old supercontinent of Rodinia.

Funded by an Australian fellowship, Mulder, from the School of Earth, Atmosphere and Environment at Monash University (Australia), spent one year of his Ph.D. studies at The University of New Mexico and accompanied Karlstrom, a professor in UNM's Department of Earth and Planetary Sciences, in a Grand Canyon research trip. Their research, "Rodinian devil in disguise: Correlation of 1.25–1.10 Ga strata between Tasmania and Grand Canyon," aimed to test models for geologic connections between the rocks of southwestern USA and Australia.

"The supercontinent hypothesis is that all of Earth's continents come together about every 700 million years into supercontinents, then rift apart into separate continents only to get reconfigured into later supercontinents," said Karlstrom. "Right now, the Atlantic ocean is spreading and continents are dispersing whereas 300 million years ago, all the continents were together in the supercontinent of Pangea, which is well documented by the match of South America and African coastlines, and the sea floor magnetic stripes in the Atlantic ocean that record the opening of the Atlantic and the breakup of Pangea."

Rodinia, a Russian term for "motherland," was the next older supercontinent; it came together about 1 billion years ago and rifted apart about 750 million years ago. Its existence is well agreed upon, but its configuration has been controversial for more than two decades. The scientists noticed that the Tasmanian Rocky Cape Group and Grand Canyon's Unkar Group have uncanny bed-by-bed similarity.

Credit: University of New Mexico
"We started this work by looking at Mesoproterozoic (~1 billion years old) sedimentary rocks in Tasmania, a small island off southeast Australia," said Mulder. "These rocks had puzzled us for a long time because they didn't look a lot like the nearby Mesoproterozoic rocks in Australia. We wanted to know where the ancient sedimentary rocks in Tasmania were sourced from so we analysed sand-sized grains of the mineral zircon, which makes up a small proportion of the sedimentary rocks."

By grinding up the sandstones from each place, the scientists found and dated hundreds of sand grains of zircon in each succession to compare their "fingerprints." The ages and the hafnium compositions of the zircons from both places match very well and the authors suggest the two areas were adjacent to each other from 1.25 to 1.1 billion years ago.

To fit this into the Rodinia supercontinent debate, they hypothesize that these sediments were both eroded from a continent collision called the Grenville Mountains that was similar to the modern Himalayan collision. Tasmania and Grand Canyon were both "out front," in a foreland basin, and rivers carried sand grains from high mountains that existed in what is now the Texas area. Fragments of those mountains can also be traced to the colliding Kalahari block, now in Africa.

"The new correlation was not enough on its own," said Karlstrom. "Given the long controversy about Rodinia's configuration, we also synthesized all paleomagnetic data for the USA, Australia, Kalahari, and East Antarctica to see if the Rodinian jigsaw puzzle could be solved this way. We found that the Tasmania—Grand Canyon connection could reconcile past (competing) models for Rodinia."

Credit: University of New Mexico
"Not only do the rocks in Grand Canyon look similar to those in Tasmania and are the same age, the detrital zircons in the Grand Canyon sedimentary rocks (and related rocks in central Arizona and Texas) also share the same geochemical fingerprint as the zircons in the Tasmanian Mesoproterozoic sequences," said Mulder. "Together, these different lines of evidence support the interpretation that the in Tasmania were once a part of the same Mesoproterozoic basin system that is now exposed in Grand Canyon. Therefore, we concluded that although now on the opposite side of the planet, Tasmania must been attached to the western United States in the Mesoproterozoic."

The scientists propose a new evolving plate configuration that was similar to the AUSMEX model (Australia and Mexico as neighbors) about 1.1 billion years ago, to the AUSWUS model (Australia and Western U.S. as neighbors) about 1.0 billion years ago, and to the SWEAT model (SW U.S. and East Antarctica as neighbors) about 0.9 billion years ago.

"The study is important for understanding the paleogeopgrahy of Rodinia because we were able to show that the crustal block that makes up Tasmania, together with a series of small, similarly enigmatic blocks now exposed in Antarctica and submerged beneath the ocean south of Tasmania, provide key geological links between the larger continents of Australia, Antarctica, and the U.S, which together make up a significant part of Rodinia," said Mulder.

"Thus, the new paper shows Tasmania to be a key puzzle piece within Rodinia," said Karlstrom. "In science, the devil is always in the details, and this new "Tasmanian devil" seems to have unlocked secrets of the Rodinian supercontinent that have remained mysterious for decades. The paper also re-emphasizes the power of international collaborations in resolving geologic debates."

Explore further: Cambrian Sixtymile Formation of Grand Canyon yields new findings

More information: Jacob A. Mulder et al. Rodinian devil in disguise: Correlation of 1.25–1.10 Ga strata between Tasmania and Grand Canyon, Geology (2018). DOI: 10.1130/G45225.1

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16 comments

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TeeSquared
1.3 / 5 (12) Oct 29, 2018
More evidence that a world wide catastrophic flood deposited layers over wide areas.
rrwillsj
5 / 5 (8) Oct 29, 2018
TS, your opinion would be more accurate, certainly more correct, if you had written:

"More evidence that endless numbers of world wide catastrophic floods deposited multitudes of varying layers over wide areas. In addition to billions of years of tectonic activity including volcanic activity and rifting crust. Mountain ranges rearing up out of the oceans, to erode down and submerge again. With random asteroidal strikes to stir the batter."

A consistently active process as recent and foreseeable future tragedies well prove.
Nik_2213
5 / 5 (7) Oct 29, 2018
RRW, Thanks ;-))

TS, if you're referring to the mythical Noachian flood, remember it was blatantly plagiarised from the significantly older 'Epic of Gilgamesh' river floods...
Old_C_Code
3 / 5 (1) Oct 29, 2018
I accidentally gave TeeSquared's insane stupid creationist comment a 5... meant to be a 1.
Mal Adapted
5 / 5 (1) Oct 29, 2018
More evidence that a world wide catastrophic flood deposited layers over wide areas.


Maybe, but it's not the most parsimonious hypothesis!

The scientific principle of parsimony ('Occam's razor') demands an intersubjectively-verifiable answer to such questions as where the flood waters could have come from, without reference to a divine and thus unverifiable source. "Genesis 7:11" isn't a sufficient answer, since neither 'the fountains of the great deep' nor 'the windows of heaven' can be verified to exist.

Absent theistic presupposition, those "layers over wide areas" are more parsimoniously explained by modern Geology and Geophysics, from the totality of *verifiable* evidence.

TeeSquared
1 / 5 (6) Oct 29, 2018
TS, if you're referring to the mythical Noachian flood, remember it was blatantly plagiarised from the significantly older 'Epic of Gilgamesh' river floods...


The Gilgamesh Epic has close parallels with the account of Noah's Flood. Its close similarities are due to its closeness to the real event. However, there are major differences as well. Everything in the Epic, from the gross polytheism to the absurd cubical ark, as well as the worldwide flood legends, shows that the Genesis account is the original, while the Gilgamesh Epic is a distortion.
TeeSquared
1 / 5 (7) Oct 29, 2018
In addition to billions of years ...


That has yet to be proven.
Phyllis Harmonic
5 / 5 (4) Oct 29, 2018
More evidence that a world wide catastrophic flood deposited layers over wide areas.

For some values of "world." While there is evidence of events that register in the global context (the iridium layer, for instance), a flood that covered the entire planet has no such evidence.

But you don't care- you're a pathological believer, so are lost to myth and fantasy.
TeeSquared
1 / 5 (6) Oct 29, 2018
Absent theistic presupposition, those "layers over wide areas" are more parsimoniously explained by modern Geology and Geophysics, from the totality of *verifiable* evidence.


Evidence of something that supposedly happened billions of years ago? Really?
Mal Adapted
5 / 5 (4) Oct 29, 2018
RRW, Thanks ;-))

TS, if you're referring to the mythical Noachian flood, remember it was blatantly plagiarised from the significantly older 'Epic of Gilgamesh' river floods...


Heh. The current consensus of Geophysics for the origin of Earth's water as ice grains in the nascent solar system, subsequently out-gassed to the fiery proto-atmosphere during the accretion and differentiation phases, then rained out on the Hadean surface as it cooled, and dynamically redistributed by plate tectonics and the solar-powered planetary heat engine of climate ever since, feels way more 'epic' to me 8^).

The modern scientific model of Earth's history may seem incredible, but it's really just a matter of scale. One must first adopt the 'deep time' (wikipedia.org/wiki/Deep_time) view, to be sure. 4.55 billion years might sound like a fearsomely long time, TeeSquared, but it all happened one day after the next, just like your life.
Mal Adapted
5 / 5 (1) Oct 29, 2018
Evidence of something that supposedly happened billions of years ago? Really?

Yes, really. For you to make sense of my supporting links, however, you'll need more of what Texas State Climatologist John Nielsen-Gammon calls "scientific meta-literacy" (blog.chron.com/climateabyss/2013/02/scientific-meta-literacy) than you've demonstrated. That is, you need to be able to tell good geophysical science from bad. I'm afraid it's rather apparent your research skills are inadequate 8^(. I'm happy to be proved wrong, but you'll have to do better than the argument from ignorance, or as Dawkins called it "the argument from personal incredulity."

IOW, Google Galileos are wasting energy. For genuine skeptics, OTOH, I recommend "The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet" by Robert Hazen ($14.99 for the Kindle version). It's concise but thorough, and highly readable if you've got some college Earth Science, if only "Rocks for Jocks".
TeeSquared
1 / 5 (4) Oct 29, 2018
Heh. The current consensus of Geophysics for the origin of Earth's water as ice grains in the nascent solar system, subsequently out-gassed to the fiery proto-atmosphere during the accretion and differentiation phases, then rained out on the Hadean surface as it cooled, and dynamically redistributed by plate tectonics and the solar-powered planetary heat engine of climate ever since, feels way more 'epic' to me 8^).


Assumptions at best. The scientific method is based on observation,measurement, testing, repeat-ability. To be done in real-time. Anything else is hypothesis.
TeeSquared
1 / 5 (5) Oct 29, 2018
More evidence that a world wide catastrophic flood deposited layers over wide areas.

For some values of "world." While there is evidence of events that register in the global context (the iridium layer, for instance), a flood that covered the entire planet has no such evidence.

But you don't care- you're a pathological believer, so are lost to myth and fantasy.


https://creation....ry-rocks
rrwillsj
5 / 5 (1) Oct 30, 2018
This is the real problem with the superstitious. They are always trying to dictate their vapid nonsense as if it were a commamdment from an imaginary deity.

As they do not have to offer any proof. They got faith! All the evidence to the contrary is to be disregarded and violently suppressed.
Mal Adapted
5 / 5 (2) Oct 31, 2018
The scientific method is based on observation,measurement, testing, repeat-ability. To be done in real-time. Anything else is hypothesis.

Where'd you get that idea? I trained to the 'semi-doctoral' level in the earth and biological sciences, before realizing I didn't want to work that hard for a living. I spent the next 30 years working closely with full-time scientists. I attest there's more to actual science than you assert.

To begin with, yours is at best a highly simplistic definition of 'empiricism', just one of science's two methodological requirements. The other is 'intersubjective verification', or 'peer review' broadly defined, because "The first principle [of science] is that you must not fool yourself - and you are the easiest person to fool. " (R Feynman). It's why every scientist's work must pass collective review by his trained, competitively skeptical specialist peers, beginning well before publication: they won't let him get away with fooling himself!
torbjorn_b_g_larsson
1 / 5 (1) Nov 04, 2018
Convenient link for those who do not know how dating works (but speculates in theological "assumption"):

"... Deeper back in time, we can work through movements of supercontinents that no longer exist, the formation of the Earth's first rocks, and (using some off-world samples) even the start of the Solar System.

This process doesn't work with every rock and every isotope, but there are ways we can build confidence in the dates we have for rocks that are over four billion years old. To find out how, watch the video."

https://arstechni...ars-old/

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