Stromatolites

The World’s Oldest Fossils Are 3.7 Billion Years Old says the headline. They were discovered in Greenland. Apparently some Aussie paleontologists went all the way to a just as uninhabitable part of the earth as the Australian Outback–just colder–to find fossils of lifeforms older than anything in their own country.  And it’s not like they were looking for them–I have no idea what they were looking for, actually, it doesn’t say–they just happened to look closely at some rocks poking out of the melting snow (you rarely hear paleontologists complaining about global warming) and immediately recognized the distinctive shapes held therein. Stromatolites!  And if there is one place on earth with rocks older than Australia, it’s Greenland. Both are mostly craton–that is big pieces of ancient land that have sort of wandered about the globe with the tectonic currents, not being ground up by continental plates and belched back up as new igneous rock formations in the mid open trenches that stitch the ocean floor. Iceland, the whole island, is part of that grinding and belching process that somehow is above sea level. As such, Iceland is about as opposite from Australia or Greenland as any place on the surface of the globe can be. There are no fossils on Iceland, it is far too new and the rock was all basically molten not long ago. Australia and Greenland, though, were in large part land that was formed maybe four billion years ago, when land was first invented, and in Australia at least there is still some of it in virgin condition (we can’t see most of Greenland yet, it’s still ice and snow covered). Both the Australian and Greenlandic cratons contain incredibly ancient rocks, and where sedimentary rock was laid down a couple billion years ago in ancient shallow seas, you will find incredibly ancient fossils. The land today is so untouched in places that in the depths of Australia there is a famous fossilized beach, you can even see the ripples left in the sand by the waves. Groovy, in an incredibly ancient kind of way.

Of course, we are not talking dinosaurs here. We are billions of years before dinosaurs fossils, before almost anything even. Fossils from that far back are few and far between. Mainly, if not exclusively, they are stromatolites. There were untold jillions of stromatolites then, vast immobile herds of stromatolites luxuriating in the young planet’s overheated waters. Indeed, Earth was a young planet full of stromatolites with no one to eat them. It was sort of a vegan paradise. Since then, though, predators were invented and stromatolites have sheltered in the less hospitable places on earth, overheated and hypersaline. There they thrive, ignored, virtually unevolving. Were we to zap one of the fossil stromatolites with a time machine gun, it wouldn’t look much different than they do today. Hence they call today’s stromatolites living fossils, like coelacanths and horseshoe crabs and cycads and the Rolling Stones.

Australia had the oldest fossilized stromatolites in the world, nearly three and a half billion years old. Or they did until the Australians I mentioned above went wandering about the ancient rocks of Greenland and found the new oldest fossils. Two hundred and twenty million years older, in fact. To give you an idea of how big a span that is, two hundred and twenty million years ago we mammals had just been invented. We were just squirmy little shrew like things, not very appealing. And birds hadn’t been invented at all. That’s how big a span of time two hundred and twenty million years is. And these Australian paleontologists found stromatolites in Greenland that were two hundred and twenty million years older (3.7 billion years old) than the celebrated 3.48 billion year old stromatolites from the Marble Bar Formation in the Pilbara region of way the hell out there Western Australia. Imagine having your oldest fossils rendered penultimate, just like that. By your own countrymen, no less. What a blow to the Australia paleontological ego, if not the body politic itself. The Government of Western Australia’s website even has a whole page boasting of “the world’s oldest known examples of fossil stromatolites (3.45 billion years old), found near Marble Bar in the Pilbara.” Ahem. Our trio of Australian paleontologists–we’ll leave them unnamed–will be a very popular bunch in the roadhouse in Marble Bar, the metropolis in the Pilbara closest to the now second oldest fossils, that’s for sure. No more free beers. Though they did push back the evolution of life on Earth even further than had been imagined. If relatively complex (by bacterial standards) stromatolites were flourishing 3.7 billion years ago, then bacteria itself must have been around much earlier than that. And the planet itself is only 4.5 billion years old. Life started here much earlier than we thought possible. I doubt, though, that would impress the locals at the roadhouse in Marble Bar. Their metropolis (population 208) was famous for one thing, and one thing only, the world’s oldest fossils. And now you’ve told everybody that they are the second oldest?

But even though the Pilbara stromatolites are a mere 3.48 billions years old, Australians can still brag (“some of the best examples of living microbialites“) that they have living stromatolites, if you call that living. Because several hundred miles to the southwest of Marble Bar, as the emu flies, is Shark Bay, and in the hottest, saltiest part of Shark Bay is a thriving stromatic metropolis. Probably the world’s most famous living stromatolites, actually, even David Attenborough paid a visit. Life forms just like this, he said with breathless and beautifully enunciated excitement, came to be in the Pre-Cambrian. He didn’t touch one. They’d feel like a slimy lichen. Which is sort of what they are, big stacks of slimy lichens, mostly made of cyanobacteria, and nowhere near as cuddly as the wallaby Attenborough had doubtless been cavorting with a day or two before.

However, despite their sliminess, these living stromatolites mean that Australia has had conceivably the longest continuous stretch of communal living on the planet. Even as the Australian craton wandered about the earth, bumping into other cratons and slowly bouncing off again, it had stromatolites. Even when the planet was wrapped in ice–the Snowball Earth hypothesis, a scary one if correct–some Australian stromatolites clung to some little saline hotspot. And they are still there, building up into stromatolites a couple feet high mat by microbial mat, like those layers of lichen you see on rocks but with little grains of sand worked in and held fast by slimy bacterial excretions to provide the structure the way we use girders to build our skyscrapers. Though to a cyanobacteria a two foot high stromatolite would be millions of times taller than the Empire State Building. They link their little flagella together somehow too, like holding tiny bacterial hands, and then they sit there and metabolize. That’s about it. That is what stromatolites so. No scurrying about like in an ant colony or a beaver dam or Los Angeles. Just four billion years of stromatolites doing essentially nothing, but doing it together. There are so many possible jokes here I can’t decide on just one so never mind.

Meanwhile, Greenland gave up on stromatolites permanently (or at least until the next super continent congeals in a half billion years or so) when Pangaea broke up and Greenland scooted pole-ward. Way too cold for stromatolites up there–they like their water hot–and not enough hypersalinity. So while Greenland has the oldest stromatolites, if Greenlanders want to see their living equivalents they have to go nearer the equator–Mexico, Brazil, the Bahamas. Or about as far away as a Greenlander can go, Western Australia, which is where those Aussie paleontologists are now, being yelled at by drunken Pilbarrans angry about being the second oldest. There goes all that tourist money.

Anyway, many years ago, back in my own personal Pre-Cambrian era, I decided that one day I’d write something about stromatolites. Now I did. I thought then that there would be more of a sense of achievement, of completion. Instead I feel empty and stromatoloid. Some bucket list this is.

stromatolites

Shark Bay stromatolites. Feel the drama.

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