Mauritia: Another Ancient Microcontinent

Claims of new “lost microcontinents” – often associated in the media with Atlantis – seem to be everywhere lately. For instance we have the recent Brazilian discovery of potentially continental rocks in the Atlantic ocean. Today ICR geologist Timothy L. Clarey has a beef with “Mauritia,” an Indian Ocean microcontinent under what is now Mauritius whose existence was proposed back in Febuary – he writes Outlandish Claims for Missing ‘Continent’.

A group of European scientists have announced the “discovery” of a small continent in the middle of the Indian Ocean that doesn’t exist on any known map. What is this proclamation based on? It’s based on the age estimates of some beach sand and a belief that the “absolute dates” the researchers determined are reliable and factual.

Clarey is not fond of this claim at all. Around 70 or 80 million years ago the Indian subcontinent separated from Madagascar and the rest of the rapidly-disintegrating supercontinent of Gondwana before heading on a collision course with Asia. According to the model proposed in this paper there existed a piece of continent, which they call Mauritia, which lay between India and Madagascar at this time and was torn into ribbons by the continental separation. One part of this microcontinent now makes up a chain of underwater mountains linking the island of Mauritius with the Seychelles on the African plate, while another runs from Chagos to the Indian coast via the Maldives and the Laccadives.

A couple of articles explain the concept in more detail such as this Nature news article, a press release, and a Sci-News article (the original paper, along with an accompanying news article in Nature Geoscience, are behind paywalls). One implication of this discovery is that there may be many similar microcontinents littering the oceans – the press release quotes the authors as saying:

We see what may be five or six other micro-continent fragments under the Indian Ocean. More research needs to done to confirm this. We also see similar features in the Atlantic and Arctic Oceans.

Clarey should not have any problem with this conclusion – young-Earth creationists tend to claim these days that much of the more recent (i.e. post-pangaea) continental rearrangements did take place, but impossibly quickly during the year of the Flood. But the first line of evidence for the microcontinent was the discovery of 20 zircon crystals in the sand of an isolated beach in Mauritius which gave a wide range of radiometric dates, all of which were in the order of hundreds of millions of years or above. Geologist YECs may be fine with microcontinents, at least in theory, but radiometric dating is their sworn enemy and Clarey appears to damn the whole idea based on this alone.

Zircons are nigh indestructible, and are capable of surviving trips into the upper mantel and inclusion into new rocks. The idea here is that rock from the Mauritia microcontinent were melted by the nearby Réunion hotspot, and zircons from this were part of the magma that erupted from the associated volcano. The solidified lava then weathered into the sand on the beach, which was collected and analysed.

Clarey mentions the use of sand twice – once in the above quoted paragraph, and again in the concluding paragraphs – and in both cases it is dismissively (“This paper presented no concrete evidence for this presumed continent other than some out-of-place zircon age dates from a few handfuls of sand!” being the other mention). Sand was actually used to avoid the possibility of contamination from rock-crushing equipment should they have elected to examine an outcrop directly.

Their derived dates fell into widely variable clusters. One grain showed an age greater than 1,971 million years, another group of grains clustered between 1,400 and 900 million years old, and a third group indicated an age between 840 and 660 million years. The wide range of dates should have been the scientist’s first clue that something was amiss. The authors of the report appearing in Nature Geoscience admitted some of the variability in the numbers could be due to contamination.

I can’t see where in the paper contamination is referenced in this context. I also don’t think that we should expect all of the dates to be the same – the zircon groups that Clarey mentioned could each have different origins at different times, only meeting up to form Mauritia and eventually land on this beach.

One of the big problems with these grains, assuming for argument that one of their evolutionary ages is correct, is that there is no known source for these “old” zircon grains within 550 miles. The oceanic crust in the vicinity of Mauritius has been dated at a mere 65.5 million years. The study authors wrote, “There is no clear-cut geochemical or isotopic signature of continental crust in the Mauritian basalts…”

Clarey doesn’t say where he got the 65.5 million year figure from – it’s not in the paper – though judging from the paper’s depiction of the timeline the oceanic crust near the island may well have been produced around this time. But this has nothing to do with their point, which is that the grains came from continentinental crust.

Similarly, the quote-mine in the above paragraph is also irrelevant. In more context they are saying:

There is no clear-cut geochemical or isotopic signature of continental crust in the Mauritian basalts, although some of their variability in ε_Nd values could indicate variable crustal contamination. We suggest that a crustal signature need not be detectable in basaltic lavas that carry xenocrystic zircons.

So they don’t have a “clear-cut” signal, but some of the variablity in neodymium isotopes (?) could be explained by “contamination” from said crust and they don’t think the signal needs to be detectable in this situation. That’s got nothing to do with the age of the nearby oceanic crust, at least so far as I can tell.

There is another line of evidence beyond these zircons, however: gravity measurements reveal that the crust where they would place their microcontinent is unusually thick for a patch of ocean. Clarey introduces it like this:

With no tangible evidence of a “lost” ancient continent to supply the zircons, the scientists invoked gravitational variations within the Indian Ocean to explain their supposed old ages. Gravity can vary slightly across the Earth because of differences in the density of the underlying rock.

The study authors interpreted the gravity data to suggest a double-thickness crust depth beneath the island of Mauritius. They speculated that deeply submerged continental crust broke apart as the modern Indian Ocean formed, resulting in the thicker portion.

He thinks he has a better explanation:

However, this thickened area shows evidence of more extensive lava flows compared to most areas of sea floor crust. Plus, it resides near the Reunion Hotspot, similar to the thickened crust upon which the islands of Hawaii sit. The increased lava output from the hot spot could easily account for the thickened crust in the area.

Like other hotspots, Réunion has moved relative to the crust above it. 65.5 million years ago it was under India, and was responsible for the creation of the Deccan Traps – a huge pool of now-solid lava more than 2 kilometres thick that has been proposed as an alternative explanation for the demise of the dinosaurs. But the thickened crust here is 10 to 20 kilometres thicker than it ought to be, and much of this extra thickness seems to lie underneath, not piled on top by volcanoes. We also know the path of the Réunion hotspot, and while it did cover some of the area it cannot possibly explain it all.

So while yes, there is hotspot-derived crust on top of Mauritia, this does not rule out that there is also older continental crust beneath and nor does it seem to be capable of explaining the thick crust by itself.

Here’s an interesting paragraph:

Thus, they are suggesting a “scientific” tale of a missing continent that mysteriously sank into the sea based primarily on out-of-place age dates. If the zircons had shown dates of 65.5 million years, there would be no suggestion of a missing continent.

What he’s basically saying is that if the evidence did not support the existence of Mauritia they would not be proposing it, which is true – but there’s nothing wrong with that. The reason why he’s complaining is that he thinks that radiometric dates cannot be trusted. He concludes:

Scientific papers are supposed to be published for their merit, and include reasonable assumptions based on newfound data. This paper presented no concrete evidence for this presumed continent other than some out-of-place zircon age dates from a few handfuls of sand!

Evolutionary scientists will not admit that their determined age dates are filled with errors and are often misleading. Instead, they hold on to these dates as fact, even to the point of telling a story of a long, lost continent.

They are following the evidence where it leads – and they have more than the one line of evidence at that. According to a recent YOM article this is supposed to be one of the freedoms of creation science (hah!) but here we have Clarey condemning his opponents for doing that very thing.