The Panda's Thumb Legacy Archive — pandasthumb.net

Stromatolites

Posted 13 August 2009 by Matt Young

↗ The current version of this post is on the live site: https://pandasthumb.org/archives/2009/08/stromatolites.html

Photograph by James Kocher. Photography contest, finalist in the "Minerals" category.
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

fnxtr · 13 August 2009

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

Iason Ouabache · 13 August 2009

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

Wheels · 13 August 2009

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.

The Curmudgeon · 13 August 2009

I ain't no kin to no stromatolite.

Michael Roberts · 13 August 2009

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.

Mike from Ottawa · 13 August 2009

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.

fnxtr · 13 August 2009

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

Mike Elzinga · 13 August 2009

fnxtr said: So what category do (other) fossils fall into, then?
In Britain we’d be called pensioners. Here in the US, retirees.

Michael Roberts · 13 August 2009

or simply old farts

fnxtr · 13 August 2009

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...

Flint · 13 August 2009

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.

Mike from Ottawa · 14 August 2009

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.

Altair IV · 14 August 2009

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?

Matt Young · 14 August 2009

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.

JimboK · 15 August 2009

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

Altair IV · 15 August 2009

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.

GvlGeologist, FCD · 15 August 2009

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. ...

JimboK · 17 August 2009

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

JimboK · 20 August 2009

Yet another link regarding Gunflint chert & stromatolites:

http://press.princeton.edu/sample_chapters/schopf/schopfch2.html

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