Log, Rock & Scissors: Nature's RPS

[Andre]

Roshambo is the name for a popular two-person hand game. It may also be referred to as Paper, Rock, Scissors. Rock blunts scissors, scissors cut paper, paper folds around rock. Nature plays it too. But instead of paper it uses logs:

Log folds around rock:

http://gallery.myff.org/gallery/177736/log3-tn.JPG

Picture courtesy of a geology studying friend

Location: Sharonville Creek Road stream, Ohio

It's mystery solving time again. What the *bleeb* happened here?

 

[matthyaouw]

I'd say landslide, debris flow or something of the sort. Hard to say without seeing it first hand.

 

[Andre]

The soil is glacial till. Answers a question but that should also raise more questions.

 

[matthyaouw]

Where is it? I've seen wood in not too bad shape in late tertiary deposits. Perhaps the glacier stirred up some earlier sediment. Any idea on the type of tree?

 

[Andre]

I'll ask about the species. Since the log is still in situ, stirring up earlier sediment is highly unlikely. That would have disrupted the scenery. But would the stirring up have caused the folding? No, because you can't bent old dead wood like like that. It would shatter. This log was folded when the wood was still alive. Now, what kind of problems would that give?

Incidentely the age of the log is beyond the carbon dating limit of about 55,000 years and the till is illinoian. >130.000 years

edit/ update: the species is spruce (Picea). The location is given in the opening post, Ohio, is in the bank of a creek, which may have erode away the till to expose the log again.

 

[matthyaouw]

Since the log is still in situ, stirring up earlier sediment is highly unlikely.

How can you tell it's in situ?

But would the stirring up have caused the folding? No, because you can't bent old dead wood like like that. It would shatter. This log was folded when the wood was still alive. Now, what kind of problems would that give?

I've never worked very much so I'll take your word that it isn't ordinarily possible, even if waterlogged. Things behave pretty strangely under pressure though. Ever seen http://www.hull.ac.uk/php/chsmjh/kiln1.jpg in till? That picture isn't a great example, but you can get folds of chalk and till reminiscent of the rock folds you see in the alps, all from the weight and movement of an ice sheet. I wouldn't be surprised if wood would do some strange things in that circumstance.

edit-some good pictures and info to be found here:
http://www.geog.soton.ac.uk/users/hartj/papers/roberts.pdf

 

[Andre]

Well, I guess that folding rocks or wood are two different things. But it would surely be worth while to find out if fossil water logged wood could still bend that way. nevertheless, it's proposed by scholars of the Cincinnaty Uni that the wood was bend alive. If that is correct then we would have a life spruce forest overrun by an advancing ice mass. Possible? probable?

 

[matthyaouw]

Got a link to any more info?

 

[Andre]

No it's ungoing investigation. No publications around. But the nagging question for me indeed is the feasibility of life forest overrun by glaciers.

For instance the Picea treeline runs roughly from North Alaska to the southerly shore of the Hudson Bay around 59N lattitude, the closest permanent snow/ice on Baffin Island is around 70N, that's more than 700 miles that a hypothetical ice sheet would have to advance before reaching the Picea forest. How fast would that have to happen for the the Piceas to be still alive or fresh; As the treeline also moves south at comparable rates with the ice.

 

[matthyaouw]

Its a bit of a puzzle it seems. Is this tree one of many then? If so, how far do they extend? Is there any evidence of soil horizons? Trees don't just grow on 'fresh' till. I'd expect a podsol for coniferous forest.

 

[Andre]

Yes several other similar logs have been found in the same area. Not sure about the soil conditions. Additinal to the physics of the wood bending, we also have to consider that this may have had to happen under freezing conditions. Frozen wood is likely rather britle. So what is wrong with the story?

 

[J77]

Couldn't the wood have been bent when it was wet...?

 

[matthyaouw]

Yes several other similar logs have been found in the same area. Not sure about the soil conditions. Additinal to the physics of the wood bending, we also have to consider that this may have had to happen under freezing conditions. Frozen wood is likely rather britle.

There is often water at the base of an ice sheet due to geothermal heat & pressure melting. Till can often be saturated.

So what is wrong with the story?

I'm not even convinced we have enough of a story to work with yet.

 

[jim mcnamara]

Here is a paper on Picea bending, fresh (green) wood:
http://heronpublishing.com/tree/freetext/27-1229.pdf

Also note in the picture that there are splits in the wood. Split wood is far easier to bend, and is a standard technique (lamination or lathing) employed to bend green wood.

IMO what you see is the result of green wood under constant stress for a long period. There is no way to rule out krummholz or avalanche starting effects as far as I can see.
In other words you cannot say definitely how much bending happened before or after burial of the wood. However, it is more difficult to bend any further already stressed and bent wood because of reaction wood. That is, to bend it without breaking it.

Taunton Press has a book on Wood Bending, which includes bending green wood.
Small diameter (~3cm and smaller) stems can be made into horseshoe shapes. Green Salix is a piece of cake to bend...

Example picture:
http://www.aroundthebendwillowfurniture.com/seating.html

 

[Andre]

Thanks Jim The essential question here are how long (order of magnitude 1-10-100-1000 years) could the wood have been death before it was bend. That would say something about the time between the treeline passing south and the glacial over run. If trees are left dead 100 years the wood would be rather stiff and more brittle. It would not bend easily without breaking.

I have questioned the current condition of the wood. It's damp (the creek) and firm but seemed in good condition. The appearance was it to be not that old at all, which seems confirmed by the picture. This hints on perfect conservation deep in the till before the creek washed the soil away.

The bends are definitely flexible and over there they don't doubt that it was bend when *alive*, J77, old Picea wood is not that flexible at all even when soaking wet.

If the bending took place under great pressure, Matt, like your chalk example, then you would expect the wood cellular structure to be destroyed, that seems not to be the case.

So the scenario seems that there was a normal spruce parcel that got overrun by a glacier when the wood was still fresh. I would not have a problem with that if we were talking mountain glaciers, advancing some meter per day to a week, which would not melt in the valley anymore due to the extreme ice age cold.

But there are no mountains in Ohio and in the horizontal plane there are many hundreds of miles of treeless tundra between the northermmost piceas and the souternmost permanent snow areas.

So that's why I still think something doesn't add up and this publication doesn't make that better:

Heuser et al 2002 Late Wisconsin periglacial environments of the southern margin of the Laurentide Ice Sheet reconstructed from pollen analyses, JOURNAL OF QUATERNARY SCIENCE (2002) 17(8) 773–780

Assuming that the pollen spectra represent regional vegetation of the southern margin of the Miami lobe of the Laurentide Ice Sheet, we conclude the following:

1 ...;

2 at the same time, Picea was present on the southern margin of the Miami lobe of the Laurentide Ice Sheet, even though pollen percentage values do not reach levels that indicate the local presence of spruce before ca. 17 500 14C yr BP; (Andre: ~20600 calendar years ago)

3 ...

4 climatic amelioration inferred from the development of spruce parkland with oak ca. 15 000(A: ~18.500 Calendar years ago) was terminated by the ca. 14 500 14C yr BP ice advance. (A: ~17,500 calendar years ago)

(Date calibration mine (INTCAL04) Very aggravating that carbon date calibration still isn't mandatory nowadays)

Apparantly it was rather common that ice and spruce were much closer together (horizontally) than today. So I repeat, what is wrong with this picture?

 

[jim mcnamara]

If the trees were either submerged or subsumed by wet soils, they could remain 'bendable' essentially as long as there were no major chemical changes to the lignin - the compound that glues cellulose fibers together. In fact, there is a Lake Superior project in the US which is salvaging submerged logs left over from the massive tree cutting of the 1850-1880's. The wood is essentially perfect, especially for getting wide pieces of straight grained spruce for violins, cellos, etc. FWIW Stradivarius and violin makers of the 17th & 18th C used the same procedure - letting logs sink into a pond to keep them usable for a long period of time.

Unless this is a construction site or a dump or anything else to link what we see to human activity, then there is nothing wrong with the picture. IMO.

What I'm saying - consider this scenario
tree slumps off wet hill into a bog or stream and is submerged. Several hundred years later the glacial till covers it and the compression phase begins. Falling and bending do not have to happen at the same time. If the water is not hard or laden with metal salts, then mineralization of the wood will not occur. Leaving the wood flexible for long periods of time.

If you are trying to use this for dating something, you have a bad assumption. IMO. Tree death date != bending date is the assumption I am making. You are assuming that bending and tree death are nearly concurrent, it seems. Correct me where I am wrong.

You are also saying there is no carbon dating data to clear things up.

 

[Andre]

I am not assuming anything. Just trying to figure out what could have happened logically. If there are natural ways to keep wood flexible for a prolongued period then that would seem very feasible. However, as posted earlier, based on dated pollen records, Heuser et al 2002 also suggest that...

..Picea was present on the southern margin of the Miami lobe of the Laurentide Ice Sheet..

So my question is, (if this is correct) why didn't the treeline move south when the ice did?

 

[LURCH]

'Bout time the dang trees hugged something!

 

[jim mcnamara]

Directly: there are ways to keep wood flexible for long periods of time. I mean long in human terms - hundreds of years at least. Not geologic time. As long as the wood does not mineralize from dissovled salts. The most common way is to submerge the wood in fresh water with low dissolved solids, not peat bogs either. Bog wood has different properties, and it is not as flexible as green wood -- commonly used by woodturners in Britain and the US.

If you mean remain flexible like green wood for several thousands of years, I do not know any way for that to happen.

If you need scientific information about wood properties written for non-engineers then
the book 'Understanding Wood' by R. Bruce Hoadley is a great choice.

 

[hypatia]

Trammel Fossil Park is in Sharonville, a great site for finding fossils in near perfect shape. I have been there more then once. I believe it was once considered outside of the Hartwell Moraine, and it was the carbon dateing of trees which has now included it in the southern limit of the Wisconsin glaciation.

 

[Bystander]

... it's proposed by scholars of the Cincinnaty Uni that the wood was bend alive. (snip)

Follow the fiber (grain) through the bend; tree trunks and limbs don't ordinarily exhibit growth patterns of joining fibers at a point on the fiber axis followed by bifurcation (branching) further along the axis.

How long does wood remain flexible? It's found in siderite concretions from the Mesozoic --- not a lot of strength left, but still flexible (Chesapeake and Delaware Canal, at least Cretaceous in age, maybe into Jurassic).

Temperature dependence of wood strength? http://www.fpl.fs.fed.us/documnts/pdf2001/green01d.pdf

 

[jim mcnamara]

Bystander - that's interesting - siderite, hmm. Is it as flexbile as green wood?

My approach was to look for a way to preserve fully green wood flexibility, on the idea that if green wood is slowly compressed it will bend quite a bit over time. I think the picture shows a lot of radial fracturing, which means the "laths" actually being bent were smaller than the bole.

Basically it is impossible to really see anything in the picture. Much less make a semi-decent hypothesis about what is going on. Andre's problem is that he needs a way to keep wood "on ice" so to speak, between the time the tree fell, and when it was covered by glacial till. And, based on what he wrote, he is looking for probably several thousand years between tree fall and bending, which is hard to come by.

 

[jim mcnamara]

After reading the FPL paper, it is based on ASTM stnadards where "green" is defined as 25% moisture. This is not real world, except in the lumber industry.

This is closer to real world: http://www.sankey.ws/wetwood.html
Picea is in the +100% to 120% w/w for green wood.

 

[Bystander]

Bystander - that's interesting - siderite, hmm. Is it as flexbile as green wood?
(snip)

"Fresh" from a concretion that is "fresh" from the matrix (soaking wet), it's very much like cheap (poorly washed) al dente pasta --- a crumbly limp noodle. Calling it wood is a bit of a stretch; appears to be more the lignin residue from hydrolysis and leaching of the cellulose from the splinters and shards that were buried, but still exhibits wood grain and "splinters" along the grain like wood.

 

[NileQueen]

That's my picture FYI.

The fact that the wood is bent around that rock seems to indicate that it was green and supple when the glacier moved in. The age is deduced from stratigraphy. There were other logs in a higher (younger) unit (at a different location along this creek) that were Wisconsinan, and still rooted and upright. That unit had been carbon-dated and is correlatable to this outcrop. Below the Wisconsinan spruce unit is a sandy unit (not over .3 m), a loess (not over 10 cm) , and then a large paleosol unit. Apparently paleosols take a long time to form.
The logs (including the picture with the wood wrapped around the rock) in the lower unit are likely Illinoian, and there were 3 of them in situ that we could see, in a newly exposed outcrop on an unnamed creekbank off Creek Road in Cincinnati.

There is no problem as far as I am concerned, with there being no mountains in this area.
Ice sheets advance as their mass builds, and retreat with a net loss between evaporation in summer and annual accumulation.

The wood looked fresh. However some samples I had that dried completely could be crushed to powder in your fingers.

Submerged trees would soon die, Jim. It is not a construction site but a high bank cut by a creek. If trees slumped off a hill into a bog, we would see bog sediments. We see only till so your scenario can be ruled out. The glacier appears to have run over this forest, and the logs seem to be beyond the range of radiocarbon dating.

 

[jim mcnamara]

NQ - Most of a living tree is already dead. Until microbial action or or mineralization changes wet submerged wood, it retains "green" properties. This can be a long time in human terms, but not geological times.

 

[NileQueen]

jim, if you are trying to say the wood got bent thousands of years later, I think that is unlikely. Probably the bending action occurred at the time of the glacial overrun, when the till was deposited. I know that most of the tree's water uptake is through the cambrium layer just under the bark, but I don't think you can call heartwood "dead" unless it is decayed.