GeologyRocks

If stromatolites are biogenic that is, and not primarily sedimentary. Even the authors mention this:

"The formation was described almost three decades ago as a partly
evaporitic, shallow-water succession containing conical structures of
possible microbial origin (stromatolites)[1,2]. However, subsequent
research indicated that abiogenesis could not be excluded [3]"

Look at http://www.nature.com/nature/journal/v441/n7094/pdf/nature04764.pdf for more details...

For the best stromatalite outcrop in this country if not the europe go to Ford Quarry, Newcastle. They are extremely well developed and probably about 50 foot in thickness. However watch out for people from the council houses above, at the top of the quarry, chucking petrol bombs and bricks. Take your hard hat!! People HAVE been injured.

I was under the impression that Stromatolites were almost certainly biological. Sure, they create sediment mats but they are the cause of the mat rather than an end result, or later effect. Isn't this quite clearly displayed in the living stromatolites in Australia and the Caribbean?

Not exactly.

As we know today, stromatolites are the result of the microbials and their natural activities.

I mean, Cyanobacteria are mucilaginous, they have natural filamentous which trap and bind sedimentary particles to produce laminated sediment (stromatolite).

So, the stromatolite then is in part microbial and sediment, altogether.

My impression is that the researchers in this case could not give a conclusive biological & sedimentary formation process to the sedimentary formation that they found. Although it looks very much stromatalitic, it might not be in the biological sense. In other words it could have been entirely physical or chemical and further study (i.e. we need more cash) is required.

So, yes, modern day stromatalites are biological (and sedimentolgical) in origin, it's tricky to say this exclusively about ancient ones unless you can definitively say that there are signs of microbial activity.

Does that make any sense?

Stromatolites are some of my favorite things. As I was taught, they are formed by mats of living things (bacteria, microbes, what have you) that are covered with sediment as it rolls in. The microbes don't appreciate being covered with sediment, so they move up through the layer above so that they can sit on top once again. This forms the layers we can see, which may either just be the thickness that the microbes allow to accumulate before they move up, or different storm deposits.

I like that explanation anyways. There was just a show on the stromatolites in Australia on the Discovery channel or National Geographic or something just a few days ago that I watched. They went to the bay as well as a location on land. They said they couldn't reveal the location of the landward deposit for fear that it would be destroyed by people coming to have a look.

Maybe this is a touch flippant, but if we can observe the way that present stromatolites behave, would it not be a fair assumption to apply this to past stromatolites, after all 'the present is the key to the past'.

Not exactly, KU.

The microbes have a vital cycle in which they catch and bind the sediment, then they died, and finally other microbes appear just over the last layer (microbe+sediment).

This vital cycle could be dairy or not (the green algae grow up during the day taking advantage of the sun=photosynthesis; and then during the dark night they die). This cycle is continous along the time and finally it´s just that makes the stromatolites up.

That makes sense too. I was just influenced by that article when it said that they found very little life within the old stromatolites. So I wondered where the microbes could have gone if they died within their layer, because I figure the overlying sediment would hold them in to be lithified with the sediment?

KU, Stromatolites are made by a synchrononic repetition of a couple of layers: biological (dark)/sedimentary (light).However, another kind of organisms could take part of the biological life, for instance diatoms, fungi and so on.

Javi