Stromatolites

| 19 Comments

Photograph by James Kocher.

Photography contest, finalist in the “Minerals” category.

Kocher_GunflintStroms_1.JPG

Stromatolites – Fossilized colonies of filamentary cyanobacteria (blue-green algae) and other microbes. Gunflint formation, approximately 1.9 billion years old. Microscopic fossils are sheaths and external cellular secretions/coverings very much like modern cyanobacteria, which may be survivors from Gunflint time. Whitefish River, Lybster Township, Ontario, August, 1992.

19 Comments

Freakin’ orsum. What’s the magnification on this? Just how big are stromatolites?

I really like this one. I want a high res version to use as wallpaper.

fnxtr said:

Freakin’ orsum. What’s the magnification on this? Just how big are stromatolites?

There are some columnar formations in Utah that are about 5 meters high, formed by a period of rising water levels in the Jurassic. I’ve heard of still-living stromatolites in Turkey that are tens of meters high, helped along by a lot of calcite precipitated from the very alkaline waters in which they reside. Those are all exceptionally big, I think. The one’s I’ve seen on TV are usually sized somewhere between a cow pat and a large picnic basket.
Mostly they only still thrive in places where other life can’t live to eat them, like super-salty lagoons.

I ain’t no kin to no stromatolite.

I found some in the Numees formation of South Africa just above tillites. Sadly I was unaware of late P-C fossils a little bit higher but no one suspected then.

What are stromatolites doing in “Minerals”? They’re biological in origin.

Next thing we’ll be hearing Kent Hovind saying (in a cassette smuggled out of The Joint in a Bible hollowed out for the purpose by removing the bits about bearing false witness and rendering unto Caesar) that the evilutionists at The Thumb have admitted that stromatolites aren’t the record of extremely ancient life but merely rocks.

So what category do (other) fossils fall into, then?

fnxtr said:

So what category do (other) fossils fall into, then?

In Britain we’d be called pensioners. Here in the US, retirees.

or simply old farts

Wheels said:

I’ve heard of still-living stromatolites in Turkey that are tens of meters high, (snip) Mostly they only still thrive in places where other life can’t live to eat them, like super-salty lagoons.

That’d be the Stromatolia region of Turkey, then? I hear there’s a growing separatist movement there…

In a rock shop, I was fortunate enough to discover a 7” diameter stromatolite sphere, reasonably priced. It sits here in front of my computer and I never tire of looking at it.

There are plenty of living stromatolites in parts of Shark Bay along the western coast of Australia, where the water is shallow, hot and very salty.

In the Ottawa region, there are fossil stromatolites visible when the water of the Ottawa river is low (as at this time of year) just to the west of the north end of the Champlain Bridge across the Ottawa River.

I’m having a bit of trouble understanding this image, particularly the scale and orientation. It looks like a top-down view of eroded, layered rock to me. Which parts are the actual stromatolites? Are the bright orange and green colors natural?

According to the photographer, the width of the picture (horizontally) is approximately 3 cm. He gives this additional information, which is Greek to me:

Colonies of filamentrous cyanobacteria (blue-green algae) and other microbes. Allochems (peloids, oolites) with oncolites & intercolumnal detritus, anthraxolite (dark), chert & chalcedony (matrix), hematite (red), ankerite (white/light colored rhombohedra), algal laminae are all visible in image. Vertical section; older layers at bottom-left.

Note especially that it is a vertical section.

I’m sure this is a rock specimen that has been cut on a diamond-lapidary saw.

Thank you for that extra information. It helps give the photo more context. I would’ve never thought it was such a narrow close-up. I think all of the photos should include a short description like that.

So, if I’m parsing it correctly, the red color is from hematite in the matrix, while most of the colored blobs and filamentary structures are stromatolites of various types; except for the white ones, which are ankerite.

Cool.

I don’t think this is quite correct. Strictly speaking, stromatolites are generally not body fossils, but trace fossils (evidence of the activity of an organism). Other trace fossils include egg shells, burrows, and of course footprints. The bacteria are often not preserved, which led to some confusion when stromatolites were discovered. IIRC, it wasn’t conclusively shown that they were organic in nature until the Shark Bay stromatolites were discovered.

The layers form when the filaments of cyanobacteria trap sediment to form the layers. The cyanobacteria then grow through that layer, which then expose the filaments to trap another layer. As a result, stromatolites can have a variety of mineralogies (although calcite is most common). In this example, I think the stromatolites are made of several different minerals, including hematite, and probably chert as well. Some of this may be original, and some may be replacement. Most geologists I know would call the entire rock a “stromatolite”, rather than trying to point to any particular part of the rock.

Altair IV said:

So, if I’m parsing it correctly, the red color is from hematite in the matrix, while most of the colored blobs and filamentary structures are stromatolites of various types; except for the white ones, which are ankerite.

These links provide more information on the Gunflint Formation stromatolites (and stromatolites in general):

http://gsc.nrcan.gc.ca/paleochron/05_e.php

http://en.wikipedia.org/wiki/Gunflint_Chert

http://stromatolites.blogspot.com/

http://en.wikipedia.org/wiki/Stromatolite

Yet another link regarding Gunflint chert & stromatolites:

http://press.princeton.edu/sample_c[…]hopfch2.html

This is a chapter from William Schopf’s book on Precambrian paleobiology - The Cradle of Life.

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This page contains a single entry by Matt Young published on August 13, 2009 12:00 PM.

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