Identifying Wood

[BAJR]

I want this book!

Having been learning about the need for C14 samples to be carefully inspected to ensure they are not from HEartwood, which in long lived trees is a BAD THING!

anyway...

[ATTACH=CONFIG]1079[/ATTACH]

If you do want it...

http://www.amazon.co.uk/Identifying-Wood...0942391047

For years I agonised over what trees were made from.

Then I came across this book and my mind was opened to wonder that is Wood.

Trees = Wood

My Table = Wood

That chair I like to sit on = Wood

Thanks to this book, I can now look at many objects and say to myself, "Yup, that's wood". :face-approve:

Go on/..... treat yourself

[Dinosaur]

Having been learning about the need for C14 samples to be carefully inspected to ensure they are not from HEartwood, which in long lived trees is a BAD THING!

Still pretty handy though for finding out if your pit is Neolithic or Medieval.... :face-stir:

[BAJR]

Note to self: Write a book called, Medieval polished axes and other humorous stories

[pdurdin]

Having been learning about the need for C14 samples to be carefully inspected to ensure they are not from HEartwood, which in long lived trees is a BAD THING!

Why is it a bad thing?

[BAJR]

Best way to describe it is this.... from this forum. where they also discuss in more detail

but basically the interior of a long lived tree is already 'dead' so therefore any sample from that will be decades if not centuries earlier than the outer 'living' part of the tree However it all depends on what you want from your sample. but if you can recover twigs (recent in time to deposition) or bone/other organic frag (good because it is going to be a short lived organism like us) then that is better

http://www.bautforum.com/archive/index.php/t-72836.html

The answer may be as simple as the way in which a tree absorbs c-14. Trees grow from the centre outwards, rendering the centre or 'heartwood' of the tree effectively dead tehreby unable to absorb further c-14 isotopes. The youngest part of the tree are the outer rings which will be larger than the inner rings thus absorbing larger quantities of c-14 isotopes than the inner heartwood. A single tree then - depending on its age - can provide an array of dates. If a 1,000 year old tree was felled today it will produce c-14 dates ranging from 2008AD to 1008AD. Thus we would find more c14 data with 2008 dates because the rings of the tree are larger. We would also find lower quantities of 1008 c14 dates because the rings would have been smaller whent he tree was much younger. So, it is entriely possible for one tree to produce a wide range of c14 dates.

[Dinosaur]

Note to self: Write a book called, Medieval polished axes and other humorous stories

Currently engaged in large (and expensive) exercise finding the 'Neolithic Landscape' in an area where most of the pits etc have jack in them (he gets about, doesn't he!), so basically site-finding-by-C14ing-those-'undated'-features-everyone-always-ignores.....hopefully the rsults might embarass a few people.... }

pdurdin - wood charcoal is dangerous stuff for dating, especially if you can't show that it came from the outermost few rings (ie the ones nearest to the date the tree was felled). 'Wild' trees can live for a very long time, that bit of oak they burned to produce your radiocarbon sample could have come from tthe middle of a 1000-year old tree, so would give you a C14 date 1000 years earlier than when the tree was felled. Even worse, the wood could also have spent another 1000 years in the roof of a church or the like before getting burnt, which would put you 2000 years wrong....

I've currently got a wierd one where I've got a c.1700BC pit (definite, well dated using other materials, multiple agreeing dates) where for some reason the wood charcoal derives from wood coming in at around 5500BC. Best guess is that they were drying out waterlogged old wood from an adjacent swampy area...take that as a warning. For exactly the same reason, always be suspicious of a lot of carbonised plant material (including wood charcoal) if you've any reason to think they may have been burning peat for fuel on your site - usually there are indicator plants that give the game away.

Try to avoid things like carbonised grain unless there's lots of it, single grains are especially suspect. They seem to fit rather neatly down worm-holes, and in my experience have been responsible for more duff dates than anything else. And be aware that carbonised hazelnut shell is near-indestructible and hence tends to turn up residually in later features. Ivory is dangerous since it could be mammoth ivory and turn out to be 100 000 years older than your Anglo-Saxon purse-ring....

C14 is a minefield!

If it's there, always go for carbonised residue on the inside of pots (stuff on the outside could be from the fuel, which could be eg old peat!) or articulated bone in preference to almost anything else. If bones were buried articulated it means the beast/person can only have died a short time before burial, which means that the carbon sample is likely to date from within a very few years of the context you're dating.

[pdurdin]

Thanks BAJR and Dino!

Sounds like useful info to go into that Handbook for New Diggers.

[Dinosaur]

The bottom line is to always think about what exactly it is you're sampling and how it got there, and if there's any doubt, don't use it (unless there's nothing else), or if you do, make it quite clear in the report what any problems/doubts are that might be attached to the resulting date.

Oh, a good time to use wood charcoal is where you get a posthole with a nice burnt post in the bottom (sometimes you just get a charcoal ring) - always try and get seperate sub-samples from the outside rings big enough for C14 and keep them seperate, I could scream the number of times I've seen people just shovel the whole lot into a sample tub.... :face-crying:

Sorry for duplicating a lot of BAJR's post, for some reason it didn't come up when I first opened this thread page so have only just seen it, glitch in the system somewhere....

[kevin wooldridge]

- wood charcoal is dangerous stuff for dating...... that bit of oak they burned to produce your radiocarbon sample could have come from tthe middle of a 1000-year old tree, so would give you a C14 date 1000 years earlier than when the tree was felled....

Um no...cos the c14 date would be derived from the decayed carbon relative to its half-life, beginning from the the date the tree died, not when it started growing.....C14 dating isn't of the object itself but of the time period since it ceased taking in carbon atoms through photosynthesis....

[BAJR]

Ah... the stuff we need to know... it is vast. And still more and more.

Nice thing about the Neolithic landscape.

I have started at last to organise Library of Everything. so each subforum is where people can put info on different subjects. LISTtastic! Either WEb Link - Book - Guide or Article

Anyway... this will I hope all fit into the book Martin suggests. I also have a cunning idea. Cartoon Reality illustrates it - to make it more visually appealing than just a text book.

Now. beware the Charcoal. and get good dates