Chlorine 36 dating method
An increase of residence time is observed up to about 500 km from the recharge zone.
For most of the samples collected along the main flowpath, a significant decay effect was observed.And to say anything sensible, you need at least two different dating techniques, based on the characteristics of the rock. This was pointed out by Olwen Williams-Thorpe and others some years ago. Thus a Chlorine-36 date may reflect either recent exposure of a surface due to processes such as frost shattering, or an original exposure date. Professor Bowen and colleagues have obtained a date of c. This difficulty of interpretation is why Chlorine-36 dating is normally done on boulders or lava surfaces whose erosional history is known (e.g. 14,000 years exposure time for the fragment from Stonehenge. This finding was widely purported in the media to demonstrate conclusively that glaciation could not have moved the bluestones to Stonehenge. It does not even support the human transport theory.
Prof Bowen's dating exercise -- also involving other dates, with two from Carn Meini, has been heavily criticised by other geologists.
After that, it will be available by post and through good bookshops everywhere. To order, click I've been looking at the film called "Stonehenge -- Secrets of the Stones." Thanks to Pete for drawing attention to it.
I'll put up another post with a You Tube link on it, in case anybody is interested.
The value of the measured ratio depends on the natural Cl concentration in the sample: the higher the natural Cl in the sample (i.e.
the taller the two dark brown columns, while they always keep their proportions) the closer the measured ratio gets to the natural ratio 3.1.
Chlorine-36 analyses were performed on groundwater samples mainly collected along this flowpath. In order to evaluate the epigene production, measurements were also performed on chloride extracted by leaching from a soil profile, near the recharge zone.