Fossilised tree?

[devon TWiG]

Coincidently I was at the coast the other day, and where there is usually just shingle , there appeared to be bed rock exposed ( or so I thought !) on closer inspection it was peat ! with wood encased/ preserved in it , it has been uncovered by the winter storms .

[se7enthdevil]

That wouldn't explain the complete circles, I have seen sedimentary rock folded before but on a much bigger scale.

 

I would imagine the rings are exposed because a tree trunk was fossilised and once it had formed rock it them cracked giving a fairly clean break.

 

It could be a stromatolite maybe??

 

 

they are not complete rings...

 

 

it starts on the left goes all the way round on the right and folds back on itself and goes left again..

 

it's a fold of rock...

 

 

concentric ring can be formed on flat fossils as they are the remains of fossilised mud pools representing where the gas bubbled up.

[Tom D]

Cool Bog oak..

 

The rings are concentric, the photo doesn't show it well, I had the advantage of seeing it in the flesh, there is another rock where you want to put the camera, I am going to take the stihl saw down and cut a bit off, then look with a lens and see if that shows anything.

[se7enthdevil]

well if your happy to take a saw to it then it cant be rock...

 

 

should it be sliced and diced???

 

can we not leave it an enigma as it probably is a tree...

[edwood]

Its in a band of sandstone that lies under limestone exposed by the sea, there are a lot of fossils in the other rocks around there, the rings form a cylinder, like a tree, I should have taken more pictures really. I just can't think of a way in which concentric cylindrical rings could form without some kind of life being involved.

 

 

 

The rocks are Dinantian which is early carboniferous, they are about 350 million years old.

 

 

I don't know anything about rocks and fossils and stuff so correct me if I'm wrong but sedimentary rock is formed by sediment falling on the sea bed floor right, so surely if their was a rock on the sea bed floor the sediment would land evenly on it, eventually the sediment would rise higher than the rock.

Their would still be a Lump on the sea bed made up where the sediment has landed on top of the rock, if you sliced this lump off and looked at the flat edge it would have round lines like this.

Sorry if that makes no sense!

 

 

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[Tom D]

I see what you mean but that wouldn't give a cylinder, i.e. if you cut through the rock a couple of feet further down you would see the same rings.. With this stone I think you would, I'll make further investigations....

[Bren.]

Looks like the face you have photographed is slightly domed out towards the camera lens. If so then a sedimentary rock would have several layers exposed on the face giving you the appearance of rings.

Rock.

[daltontrees]

I see what you mean but that wouldn't give a cylinder, i.e. if you cut through the rock a couple of feet further down you would see the same rings.. With this stone I think you would, I'll make further investigations....

 

If you know for sure that it's Dinantian, that makes an explanation even easier.

 

Whereas sedimentary layers are generally laid down horizontally and then lithified (squeezed, baked and turned to rock), not all rocks preserve a perfect stratified form.

 

In the Carboniferous period, the centre of Scotland was essentially a large rift valley, a descending mass of crust between two even bigger masses of crust that were separating slowly. The land to the north, currently the highlands, was a source of sediments. The land to the south, currently the southern uplands, was also a source of sediments. However, the main character of the central lowlands was that it was at sea level. For a while it would be just below sea level and would have been rich with life, particularly coral reefs and silty lakes or seas where sealife debris like shells and reefs that were very calcium rich resulted in limestones. As these areas bult up to sea level, they became choked with silt and sand, giving us mudstones, sandstones and siltstones. Some of these yield fossils of bivalves. In time, the area would become stably terrestrial and would have been characterised by swamps with primitive plants and trees. These are the source of scotland's coals.

 

But back to that rift valley. With an intermittent, juddering descent of the central block downward, the areas of 'land' were periodically submerged and became shallow seas. After a dump of new sediment, the area again teemed with marine life, and the commencement of the next layer of future limestone was underway.

 

This happened in the scottish lowlands cyclically many many times. A look at the stratigraphic record shows a more or less perfect conformable cycle of limestones, sandstones, coal measures, thin sediments, limestones, sandstones, coal measures etc.

 

So in this context you need to think of recently disturbed sediments, still in a quasi-liquid state, being subjected regularly to earthquakes that were probably on a San Andreas Fault scale. The central lowlands is riddled with smaller faults too, what is known as syndepositional faulting that happened during rather than after sedimentation. Local topography would result in underwater and terrestrial landslides. But you can often find an even simpler phenomenon in scottish carboniferous rocks called 'dewatering structures'. This is where the otherwise clean planar structure of the sediments has been bent, billowed, slumped, folded or sheared, while the sediments were still soft.

 

On the Fife coast in carboniferous rocks I have seen almost spherical plumes of rocks which have been cut through by weathering to give concentric circles. Maybe you are seeing something similar, i.e. lamina distorted before lithification.

[Tom D]

Interesting, sounds possible but I am fairly sure that all the rings formed a cylinder 3-4' long, do you think thats possible? The other rocks surrounding don't seem to show this..

[daltontrees]

Interesting, sounds possible but I am fairly sure that all the rings formed a cylinder 3-4' long, do you think thats possible? The other rocks surrounding don't seem to show this..

 

Your pictures are a wee bt vague, I am trying to imagine what you have seen...

 

In the meantime here's a thought. There is a superficial similarity between rocks and trees in cross section.

 

The rock formed from sediments. If you get a handful of dirt and shake it in a bottle then stand it still to stettle, in a few hours you will see that the largest particles (pebbles, coarse sand) settle out first, then fine sands and silts, finally clays. Some stuff will hardly settle out at all. This is what happens in nature, a blast of sediment comes into a lake or shallow sea from a storm in the mountains, and a layer of sediment going from coarse to fine forms. Next time another layer is laid on top of it. The layers can represent one year, as the bulk of sediments coming into the lake or shallow sea can be in spring with melt-water.

 

The tree forms from vascular vessels and woody cells. In spring the tree comes out from dormancy, flushes its leaves and draws huge amounts of water up the stem for transpiration and photosynthesis. The ring-porous trees in particular develop very big xylem vessels for water transportation in the first couple of months of the growing year. Then the tree settles down for the rest of the year and puts on smaller vascular vessels. This accounts for the ring structure of wood.

 

Trees and rocks therfore both have the same characteristics, each layer or year's growth starts with large vessels or partiles and grades into smaller particles or sells then stops for the year or season.

 

Manys a time on the beach I have been stunned by the similarity between sedimenraty structures and wood structures.

 

I will dig a bit deeper and see if I have a few photos in my collection to illustrate. Before I was a full-time tree-bore I was a part-time rock bore.