ATIAHARA - Excavations

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The ATIAHARA Trench - July 1994

The first charcoal sample from ATIAHARA to be radiocarbon dated, came from this section of the trench wall where there was a very wide separation between the upper main occupation layer and the middle occupation layer.

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first beta results

From the enlargement of this photo we can see that the sample came from a point only a few centimeters from the top of the middle layer, we do not see the lower layer which at this point may be merged with the middle layer. I would say that there is a good chance that the charcoal was from the middle layer. Beta returned a date of 580 BP plus or minus 50 years. I was hoping for a much earlier date, and continued to search for a better charcoal sample and or artifacts within the trench walls. Finally on the 19th of September I discovered large pearl-shell scraper and the next day another, along with a complete well finished adze and terebra shell chisel, all within a space of a few meters, all found in the lowest layer, and these were probably only a few meters from where the first test sample was recovered (see these details in Volume 25 ).

second beta result

After finding these artifacts I set about to try to recover charcoal from the same layer, only a small amount was found and I could not be absolutely certain that it came from the lower layer. Beta returned the results by early November and they proved to be very similar to the first. I was not convinced by these results and continued to search for a good sample, one that I was sure of, one that was from the 4th layer

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Square C 1.5 -2m


Finally in June of 1995 while excavating the C squares, I discovered a pocket of charcoal that appeared to be below the third layer. You will notice in the enlargement that the upper layer, merges with and obscures the middle layer however the lower (third) layer is continuous right to the corner where we can see a fourth layer below it. In this same square we had already found a number of important early artifacts, and so carefully extracted a sample for yet another radiocarbon analysis. This time, however I would opt for the more expensive AMS technique. AMS (Accelerator Mass Spectrometry) radiocarbon dating is a way to obtain radiocarbon dates from samples that are far smaller than that needed for standard radiocarbon dating. Standard c14 dates require amounts of between 1 and 10 grams of charcoal; AMS can use as little as 1-2 milligrams, and under special circumstances to samples as small as 50-100 micrograms. In standard radiocarbon dating, scientists perform a limited or proportional count of the decaying C14 atoms. In AMS dating, researchers use an accelerator-based mass spectrometer to count all the C14 atoms, rather than just those atoms which are decaying. AMS dates are therefore more precise and require smaller samples.

AMS result

Here at last was a result more in line with my expectations, a date demonstrating that the ATIAHARA settlements could easily be earlier than the Wairau bar burials!

calibrated results

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Go to Comparative Implementology go to ATIAHARA.ORG