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Sunday, 17 March 2013

Strontium isotope ratios


The standard BGS geological map of Great Britain and Ireland. Strontium isotopes in the environment (and in cattle teeth) are related above all else to bedrock geology -- but might the pattern also be distorted in areas where there is, for example, thick till in the areas where cattle are grazing?


The simplified strontium ratio map -- five categories only


The more detailed strontium ratio map -- eight categories.

Thanks for various contributions on this -- including those from Geo and Myris.  Even given the difference in the groupings involved in the two strontium isotope maps, there are discrepancies that are difficult to interpret.  However, it does seem clear that there is no way you could differentiate the teeth from cattle raised in the Orkneys from those which were raised in many parts of Southern England within twenty or thirty miles of Stonehenge.  Even in areas with higher ratios, I cannot see how you could claim that ANY of the cattle tested could have come from Scotland, given that there are many areas of Palaeozoic rocks much closer to Stonehenge, for example in South Wales and in Devon and Cornwall.

It appears that Prof MPP has now acknowledged (in Leicester the other day) that the "Orkney connection" with Durrington Walls and Stonehenge had better be abandoned.






15 comments:

TonyH said...

Many thanks for producing these maps, Brian, as well as any assistance given by Myris & Geo. I will peruse them after my Sunday lunch.......

BRIAN JOHN said...

First things first. Settle down and read the Sunday paper on that most excellent rugby match yesterday......

TonyH said...

Wrong - shaped ball!! More concerned with what Cardiff City did to a North Country team who retain my affections...

Anonymous said...

Get 'em up, ride 'em in, move 'em out, Rawhide!

An Old Cowhand

geocur said...

Ii can't find link to this but Janet Montgomery who works with Jane Evans says "Food and water have 87Sr/86Sr values that
reflect their geographical origin because strontium weathers from the host rock into groundwater , river water and overlying soils and is ultimately transferred with negligible
fractionation into plants and animals."

BRIAN JOHN said...

Here is the explanation of how it all works, from the NERC web site:
---------------------
The application of isotope analysis in tooth enamel to the study of population migration and movement

Strontium isotopes
Strontium has four naturally occurring isotopes, of which three are stable, and one (87Sr) forms by the decay of 87Rb. Strontium is chemically similar to calcium, and enters the biosphere primarily through the uptake of Sr by plants. The isotope composition of Sr in the biosphere is controlled by the isotope composition of the leachable component of the soil on which the plants grow. This, in turn, varies depending upon a combination of factors which include the age of the underlying rocks, the rubidium content, weathering conditions and the susceptibility of different minerals in a heterogeneous rock to weathering processes.
Strontium isotopes provide a powerful tool for studying the movement of humans and animals across isotopically different terrains because strontium is absorbed by the body and deposited, with calcium, in teeth and bones. Tooth enamel forms during the early years of life and its composition is not altered subsequently; hence, it constitutes a recoverable archive of childhood diet.

In archaeological skeletal remains, enamel is also the tissue most resistant to post-mortem contamination, thus retaining its isotopic integrity over thousands of years. Once incorporated into plants, Sr passes up the food chain unfractionated.

Sr-isotope analysis of tooth enamel provides a tool to differentiate between people or animals based on where they obtained their food and water at the time of tooth mineralisation. Combined with oxygen analysis, which is related to climate zones (see below), these isotopes can provide powerful constraints on the childhood origin of individuals, and can be used to assess population heterogeneity and track migration.
--------------

I should have mentioned that -- as Geo points out -- rainfall statistics can also have an effect on the levels of Sr recorded in the environment. It's one of the variables fed into the calculations.

TonyH said...

A mistaken conclusion was drawn in 2010 about the birthplace/ early life of a 14/15 - year-old boy whose bones were found aroud 2005 on Boscombe Down, east of Amesbury on land acquired for military housing.

Emblazoned across the press releases, he was claimed as a 'Mediterranean Boy'. There was, for example, an article in Mike Pitts' British Archaeology, November/ December 2010, by Alistair Barclay of Wessex Archaeology. The boy was wearing amber beads. Srontium analysis and research had been carried out by Jane Evans and Ms Chenery of the NERC.

Another news item appeared on the BBC Science site at:-

http://www.bbc.co.uk/news/science-environment-11421593

"Stonehenge boy was from the Mediterranean"

What is interesting is that I heard MPP himself say to a Salisbury audience they no longer claimed he was of Mediterranean origin, and was very likely to have been a local; however, nowhere have I seen a printed disclaimer from Wessex Archaeology or from NERC or Jane Evans. Too embarrassed? Not very scientific. Anyone else heard of the issue of a disclaimer?

BRIAN JOHN said...

All these dating and "origination" techniques start off with a great fanfare and any number of outrageous claims of accuracy -- but then reality kicks in, as more and more variables are found to affect the lab results. It happened with radiocarbon dating, and with chlorine dating -- I recall the fun and games associated with Prof DQ Bowen's dates for the bluestones some years ago. Then we get a period when reality kicks in -- and a lot of old results are either recalibrated or dumped altogether.

See this post:

BRIAN JOHN said...



Oops -- here it is:

http://brian-mountainman.blogspot.co.uk/2011/11/those-famous-chlorine-36-dates.html

geocur said...

Tony ,in the MPP Stonehenge book p214 he mentions the calibration problem connected with liquid diet having a previously unrealised major effect on oxygen isotopes .It was only when all the isotopes were examined was it realised that there was a problem with the oxygen isotope .

Anonymous said...

Respect Brian
Wrong shaped balls or not, It was a superb performance from the welsh team. The less said about England the better.

Said through gritted teeth.

Yours cringingly
Alex Gee

BRIAN JOHN said...

All credit to the English boys -- they played their hearts out too. It's just that the Welsh boys wanted it more and were more skilful on the day -- and after all, the Millennium Stadium was filled to overflowing with adrenalin.

Anonymous said...

MPP and I obvioulsy think the same way.

The same way that meant when my mother caught me with my mouth covered in chocolate, my hypothesis that someone else ate my younger brothers Easter egg, better be abandoned.

Cheers
Alex

TonyH said...

Thanks, geocur:

I'd forgotten MPP's piece on pages 214 -215 of his latest book, which includes mention of our at - first - declared - Mediterranean - boy, who then turns out to be much more local. My point is that no-one, that is, apart from MPP in his book, has bothered to correct the misleading statements emblazoned across the country's mass circulation newpapers (or even the BBC's blogsite, etc, etc).

BRIAN JOHN said...

Well, and all credit to him, MPP does show that he can change his mind if the evidence stacks up strongly enough -- or if evidence in favour of his hypothesis evaporates. I was pleased to see the ditching of the theory that there was once a gigantic bluestone circle at Waun Mawn, on the flank of Preseli, following the search for stone holes which turned up nothing at all....