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PietAlberts

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Slide 1

I recently started reading up on stromatolites after I learnt that we have stromatolite formations and living tufa cyanobacteria colonies in the rocky beaches of Port Elizabeth, South Africa. The cyanobacteria found here are unique, their habitat is the semi-freshwater pools where freshwater from springs meet the sea where they line and grow on the submerged surfaces of the pools. The stromatolites have irregular forms and my observation is that quite often they are concave plates opposed to the more well known dome shaped forms. Here is a photo I took at Schoenmakerskop this morning. The cyanobacteria colony is in the centre and the stromatolite formations in the background

Picture 1

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I was wondering how it is that the reefs are often arranged in straight and parallel lines, some drama must have played off here over millions of years!

Here is an example of the convex shaped plates (How old are they?)

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Slide 2

Cyanobacteria growing at the freshwater seepage spot

Picture 3

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Slide 3

The freshwater – seawater interface pools where cyanobacteria from ancient origin are still living and building stromatolites. One can call this pic “work in progress”. In these pools the cyanobacteria are protected from mollusk and other creatures grazing on them. There are not many environments like this left in the world; cyanobacteria are declining rapidly since the Cambrium.

Picture 4

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Slide 4

The tufa building cyanobacteria in these pools are unique; they seem to grow at any angle as long as they can catch the sun. These stromatolites were probably formed in a pool with little interference and turbulence. The microbial mats were aligned vertically and the stromatolites expanded in a horizontal direction, the mats are quite neatly arranged in a parallel manner.

Picture 5

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Slide 6

But during the ages, through different environments and cyanobacteria species operating, vastly varying structures of stromatolite were formed. In the photo below it is clear that this column was formed in tumultuous marine conditions and probably different cyanobacteria. These porous structures have very irregular laminations. There are large deposits of calcite in the cracks and pores and the appearance of the stromatolites is dark grey against the light colored ones above.

Picture 7

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Slide 7

Here is a remnant of a once massive stromatolite column; through the cross section one can see the greatly irregular layers

Picture 8

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Slide 8

A view from the top of the structure above shows the floor of the now demolished column, the forces of the ocean playing a major role in the destruction.

Picture 9

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Slide 9

A different view from the top of the beachfront showing the ruins of the column above.

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Slide 10

Stromatolites grow at roughly 0.5mm per year depending on the environment and the cyanobacteria species present. So they can get pretty big and heavy over a few thousand years. In this picture one can see that the horizon tilted a few times during the formation of this column probably due to the compression of the base material.

Picture 10

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Slide 11

The bedrock where the stromatolites are based on is mostly quartzitic sandstone from the Peninsula Formation (from the Table Mountain Group, from the Cape Supergroup). The bedrock is exposed here again at this spot amidst the aging stromatolites.

Picture 11

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Slide 12

The stromatolites around here often have dramatic forms, everyone tells a story

Picture 12

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(I noticed the scour marks on the rock on the right after looking at this pic, must go and check it out)

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Slide 13

Stromatolite warped by the elements as it was forming

Picture 13

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Slide 14

In this region the elements are currently demolishing stromatolites at a greater rate than they are replenished, there are still some huge structures left over. My fellow stromatolite hunter is dwarfed by this huge stromatolite boulder, but eventually it will be reduced to sand, that is just the way the “rock factory” works.

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The column below is obviously losing the battle against the elements, hanging on by a thread! (The height of this section is about 2 m)

Picture 15

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Slide 15

In this pic one can see the mayhem from the point of view of the stromatolites

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This leftover stromatolite pillar below must have toppled over recently

Picture 17

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Slide 16

Unfortunately not much is known yet about the stromatolite formations here along the coast in Port Elizabeth. The cyanobacteria colonies were only discovered around the year 2000 and the local university is currently doing research.

Here is a link to a research article of the NMMU (I am not associated to):

http://www.sajs.co.za/sites/default/files/publications/pdf/Perissinotto_Research%20Article_0.pdf

Google map view of the Schoenmakerskop area where I took the photos in this article

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Google map coordinates:

-34.041679, 25.536060

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Very, very interesting; I am glad to see this ancient biological process getting some in-depth atention!

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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Stromatolites have a lot of different morphologies. When massive reefs of Stromatolites were prevalent, it must have somehow been advantageous to have been arranged like that because of there environment. Nowadays things are different, so we have a much more limited array of stromatolites in a few niche environments. They've been declining for hundreds of millions of years- They peaked in the mesoproterozoic which is getting close to the end of the precambrian. In the Cambrian they were not nearly as diverse as they were before and there is much less of them now.

Keep in mind to that some geologic occurrences can end up looking almost identical to stromatolite fossils, so if some of the fossils that you have shown have not been studied all that much there's a chance that they could be geologic. Generally speaking, its really hard to pin down the origin of anything made of rock seeing as none of us were there when it was made. some stromatolites not being biologic in origin could attribute to a lot of the differences you see between old forms and modern ones. To make things more convoluted, a lot of fossilized stromatolites just look like weirdly layered sedimentary rock to begin with. Yay science!

Looks like you've put a lot of time and energy into this, so I thought Id give you some food for thought

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I appreciate the comment and agree that it is not straightforward science (and I am an amateur scientist on top of that) to identify and classify rock formations and deciding if they are biogenic or not. I did quite a bit of reading up and investigating and feel reasonable confident about the info I presented here, but I will not feel offended nor be surprised if I am corrected by a more scientific investigation and finding. One of the motives of my article above is to express my concern that little is known about the stromatolite formations around here and to express a desire that their scientific study should be prioritized. It is like throwing a stone in the bush to see what will come out.

So it is a bit of a challenge, I would be happy if I could be proven right or wrong in my observations above :)

The methodology for my conclusions in this article was to make assumptions based on my investigations and the information that I gathered and then look for evidence that would contradict or question that. I am still looking for more evidence and would welcome any inputs.

My conclusion at this stage is that most of the visible rock formations around Schoenmakerskop near sea level are stromatolitic.

One point of interest (mentioned in other topics too), in South Africa it is illegal to own, sell, handle, possess or interfere with fossils without a permit. I would have dearly liked to cut and polish some samples to investigate closer but I do not have a permit to do so.

I will of course continue my investigations and attempt to refine my knowledge of the Stromatolite formations around here. Even though I can not cut and polish samples I can photograph and study fragments of which there are an endless supply. Watch this space for more photos and info in the near future.

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I think you're doing a great job- you seem very thorough. Do you know the age of the strata that your specimens are in?

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Slide 17

The stromatolite formations around Schoenmakerskop described in this article are laid down on quartzitic sandstone called the Peninsula Formation (aka Table Mountain Sandstone). The Peninsula Formation was formed about 500 ma on top of Precambrian substrate and is up to 2 km thick. It is interesting that the bedrock formation here at Schoenmakerskop is the same formation as the top 600 m of Table Mountain. A very informative article about the Cape Fold Belt including this formation can be found on Wikipedia:

http://en.wikipedia.org/wiki/Cape_Fold_Belt#Table_Mountain_Group

I copied one of the diagrams, a north-south cross section, here with permission of the author (Oggmus)

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In the diagram the ocean is on the south (left) side of the diagram. It seems that here at Schoenmakerskop near the coast there is only Precambrian earth below the Peninsula Formation and above that the stromatolite formations and some recent deposits. At this stage it is still an interesting question how old these stromatolite formations are.

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Core-sampling and sequencing the paleomagnetic reversals (if preserved and measurable) might be able to date the structures. Wouldn't that be fun!

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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Slide 18

Going back to the structure previously described in slide 7 picture 8. I scrutinized it some more to get a better understanding of its origin and identification. Here is a “frontal” picture of the structure. One can see the wavy and twisting laminae with intrusions of sandstone and calcite layers. The porous intrusion in the middle left could possibly be lava, see further down for more evidence of possible magma outflow near this spot. The next picture shows a close-up of the area in the yellow rectangle.

It is much like a book with many pages written in a foreign language

Picture 18

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Slide 19

Here is a close-up of the layers showing considerable variation in shape. Anybody have any ideas?

Picture 19

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