I’m pleased to feature some paleontology today from reader John Scanlon. In case you didn’t know, stromatolites are layered accretions of microorganisms, usually cyanobacteria (“blue-green algae”), and they represent some of the oldest fossils on earth: about 3.5 billion years old—only about a billion years after the Earth was formed. But these accretions are still formed today by living bacteria, and exist in a few spots on the planet that have extremely salty water, including Australia, Brazil, and Mexico.
Shark Bay, Australia, which John mentions below, is one of these places, and I’ll put a photo of living stromatolites below his photos. His notes:
My phone generally doesn’t do justice to actual fauna, but might do for some nice palaeobiology on a recent working trip in the Hamersley Range (Pilbara, Western Australia). The area’s well known for its banded ironstone formations (BIF; formed as the dissolved iron in the oceans rusted out, keeping the level of toxic oxygen low for a while), but also has extensive basalt flows (also dikes and sills) and outcropping granite/greenstone basement, ranging from Archaean into Proterozoic. The tectonic stability of the area is shown by the fact that most of the stratified rocks are still nearly horizontal , though there are also some very attractively folded BIFs around the edges.The attached photos show something I haven’t often seen in the Pilbara: really well preserved stromatolites (in the Carawine Dolomite). They have the same range of sizes and shapes as the ones forming today in Hamelin Pool at Shark Bay, not very far away. The stromatolitic carbonates formed in shallow parts of the basin at the same time as the BIFs were accumulating in the deeper areas. The vertical and horizontal jointing and differential etching of the rock make them outstandingly clear examples, and also full of crevices so I had good reason to spend time looking at the rock while searching for animals. In one pic, wave ripples on a horizontal surface have been polished by Euro (JAC: waleroos, a marsupial: Macropus robustus) using the overhang as a sleeping shelter.
Ref: Rasmussen et al. (2005, doi: 10.1130/G21616.1) date these rocks to about 2.63 Ga. [JAC: 2.6 billion years old!]
The remnants of ancient life:
Wave ripples polished by sleeping wallaroos!:
Here are some living stromatolites being formed today in Shark Bay, Western Australia (picture from Wikipedia). They look just like their fossil forebears.
Here’s a cross-section of a living stromatolite, showing its similarity to the ancient ones (source here):
Wow, really cool stuff! I love that “sectioned” stromatolite in the second-to-last photo.
We have a small (polished) stromatolite fossil, about 1.1 byo, I think from Australia, somewhere.
That one (shape suggesting a crown) seems to be what Simonson et al. call a rosette-type structure in a flat pebble conglomerate. These are where bits of a mineralised layer get broken up (e.g. by wave action) and redeposited in a nearby depression; a bit like rip-up clasts of clay or mudstone, but in this case the hard platey bits end up packed together and sometimes (as here) standing on edge.
Then a whole new stromatolite grows over the top!
Very cool!
How astonishing that these critters have been around, just doing their thing, for 2.6 BILLION years. And we think we’re so special…
Fantastic photos!
Looks like puff pastry. Now I’m hungry.
More seriously, very cool.
Very very very cool.
How old are these particular stromatolite fossils? I know there is a wide range of ages, including some of the oldest fossils.
It’s in the post, Mark: 2.6 billion years old.
To elaborate on PCC’s point, my stromatolite fossils (from Scotland) are a mere 1.1- 1.2 billion years old. These are conservative organisms.
Nice post! I hope it is OK with John Scanlon if I use these pictures in my BIOL111 lecture.
Well, you should ask him here, and certainly credit him.
OK! I am trying to get in touch with him.
Sure, Avis, you’re welcome. Please consider them CC BY.
There are pics of similar specimens from the same formation in B.M. Simonson et al.(1993), Precambrian Research 60: 287-335. But they’re in monochrome, and Elsevier owns them for ever.
John, Thanks!! I love your photographs.
Deep time always makes me gasp. Good to know you can reach out a touch it. First I have to get to AU.
Why? There are probably fossil stromatolites closer to you, and quite likely living ones too. They’re not *common*, but they’re not vanishingly rare either.
A quick Wikipedia search – Bahamas and British Columbia, are the closest. There’s a chance then.
Thanks John and Jerry, very^very cool! (Time for another thread on how we are running out of super^superlatives…)
By the way, I have learned that stromatolites, arguably because they may lack the tell tale layering [ https://en.wikipedia.org/wiki/Thrombolite ], are found not only in very salty environments. Similar structures are also found in nutrient poor environments where they can – I assume – avoid predation/grazing by eukaryotes. Here is the first (?) example:
“Discovery of large conical stromatolites in Lake Untersee, Antarctica.
Lake Untersee is one of the largest (11.4 km(2)) and deepest (>160 m) freshwater lakes in East Antarctica. Located at 71°S the lake has a perennial ice cover, a water column that, with the exception of a small anoxic basin in the southwest of the lake, is well mixed, supersaturated with dissolved oxygen, alkaline (pH 10.4) and exceedingly clear. The floor of the lake is covered with photosynthetic microbial mats to depths of at least 100 m. These mats are primarily composed of filamentous cyanophytes and form two distinct macroscopic structures, one of which–cm-scale cuspate pinnacles dominated by Leptolyngbya spp.–is common in Antarctica, but the second–laminated, conical stromatolites that rise up to 0.5 m above the lake floor, dominated by Phormidium spp.–has not previously been reported in any modern environment.”
[ http://www.ncbi.nlm.nih.gov/pubmed/21504538 ]
More on extant freshwater (and cave/mine!) stromatolites here:
https://en.wikipedia.org/wiki/Stromatolite#Modern_freshwater_stromatolites
This excerpt is amazing:
“Laguna Bacalar in Mexico’s southern Yucatán Peninsula in the state of Quintana Roo, has an extensive formation of living giant microbialites (that is, stromatolites or thrombolites). The microbialite bed is over 10 km (6.2 mi) long with a vertical rise of several meters in some areas. These may be the largest sized living freshwater microbialites, or any organism, on Earth.”
Fascinating.
So how old are the current stromatolites in Shark Bay? Can you figure their age by layers of material like we do with corals or tree rings?
That is a good question. From which you can infer that I don’t know the answer.
I have certainly seen people trying to do dating analysis of “rhythmite” deposits across the geological record, in particular looking for the interplay between smallest-scale cycles (inferred to be “daily”) and larger scale cycles (inferred to be “monthly”), but of course you can’t rely on there being 24 hours in a day, or 27.something days in a month, once you go back more than a few tens of MA, because the torque the Moon applies to the Earth, and that the Earth applies to the Moon gives us the direction of change in the system, but the rate is probably largely controlled by the area of shallow seas which are perpendicular to the … to the … now, would it be the Equator, the Ecliptic, or the trace of the sub-Lunar point.
It is a good question. I remember reading up on it a few years ago, but having just stuffed my gullet on steak pie and stuffed jalapenos, I can’t be bothered remembering. But there are certainly a number of people who study the fossil record (using “rhythmites”) as a way of understanding the tidal evolution of the Earth-Moon system.
I think I got onto the topic by looking at Earth’s “other” “moon”, Cruithne.
Thanks for the added info…much to ponder.
great pics, John! I’ve always been fascinated by stromatolites.
I wish this were a Yahoo! article: it would draw creationist commenters like flies to fresh dung and then I could have my fun with them!
I can hear their strident cries:
“No, they’re NOT 3.5 billion years old” (this is of the, “Well, I guess that settles that” category-)
“Carbon dating has been shown to be completely inaccurate” (this, the, “Let me act like I understand science, for a minute” type)
Then there’s the type that’s becoming increasing common as they run out of arguments:
“LOL!” What idiocy! You sheeple are completely taken in by the atheist scientists’ hoax! These organisms are EXACTLY like the ones today; PROOF of creation! Fools!”
I did read a great reply from a rational person the other day:
“Why do young-earth creationists even BOTHER to write replies? All they need to do is write, ‘comment hidden due to low rating’!”
I don’t know what your Carbon Dating is like, but my Date from Ashley Madison sounds great – computer programmer for the last decade, photos that look like a porn starlet before she starts disrobing for her screen test/couch … what could possibly go wrong?
I’ll have to try that some time. I suspect it’ll get a high rating.
Do you ever get any feedback from Yahoo News comments? My withering sarcasm all seems to fall into a black hole.
I get a smattering of, “spot-on!s” and “LOL!s”- the creatards, of course, once they’ve been bested, never come back: I’ve asked several in the last week to explain the two conflicting creation stories in Genesis; never heard from them again!
I always tell people, though, that I’m not debating these people to try to convince THEM of anything; their programming is much too deep for that- I’m doing it so that those who are observing and are still, “on the fence” might learn something.
What’s that saying? “It’s useless to try to use reason to budge someone from a position that was not acquired through reason.”
Stromatolites are so cool! I’ve never forgotten a Dawkins documentary that included the ones at Shark Bay.