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Friday, 18 December 2015

Thanks to the Archaeologists

I may not like the assumptions and the interpretations of the archaeologists who have been digging at Craig Rhosyfelin, but I do like the fact that we now have about 50 radiocarbon and OSL dates spread over a long history of intermittent occupation at the dig site.  That is a fantastic resource in its own right, and I suspect that in the long run the research of Prof MPP and his team will be remembered not because of quarries but because of what it tells us about settlement history and climate change in the area.

I'm still trying to unravel the stratigraphy as it is portrayed in the "Antiquity" paper, and to relate it to the stratigraphy as we observed it and as it is represented in our paper in "Archaeology in Wales."  All will become clearer in due course.  But it is already clear that the dates all come from the horizons which we refer to as "stratified slope deposits", colluvium and modern soil -- in some places these sediments are over 2m thick.  I really hope that the archaeologists have had some palynologists on board -- it will be fascinating to see what the pollen analyses tell us when they are published.

Some time needs to be spent on examining the contexts of those dated remains -- are there more papers on the way?


Brian John, Dyfed Elis-Gruffydd and John Downes.  2015. OBSERVATIONS ON THE SUPPOSED “NEOLITHIC BLUESTONE QUARRY” AT CRAIG RHOSYFELIN, PEMBROKESHIRE".  Archaeology in Wales 54, pp 139-148. (Publication 14th December 2015)

Mike Parker Pearson, Richard Bevins, Rob Ixer, Joshua Pollard, Colin Richards, Kate Welham, Ben Chan, Kevan Edinborough, Derek Hamilton, Richard Macphail, Duncan Schlee, Jean-Luc Schwenninger, Ellen Simmons and Martin Smith (2015). Craig Rhos-y-felin: a Welsh bluestone megalith quarry for Stonehenge.   Antiquity, 89 (348) (Dec 2015), pp 1331-1352. 


Dave Maynard said...

There is a lot of data in those radiocarbon dates that takes a bit of teasing out. Figure 4 for example, has a set at the base of the section of 7460-7180BC, then a series running from 740-390BC to AD810-1030 through a metre of hillwash. What is odd here is why there are no deposits for the intervening 6000 years in that area.

Was something holding back the hillwash during the intervening period, or has something removed those deposits? The shape of the cwm and available sources of material could have a lot to do with it. Could the back of the cwm have held this 6000 years of hillwash which then gradually moved forward?

Or is the case that Iron Age, Roman and Post-Roman farmers ploughed the area heavily, allowing the soil to erode and move into the cwm, something which had not happened in the previous periods?

This answer may not help Brian's views, but it certainly shows the complexity of the sediments that need to be fully understood.


BRIAN JOHN said...

Yes, I agree Dave that there is a lot in there which is very difficult to interpret. All of the problems (or at least some of them) stem from the fact that the stratigraphy is nowhere properly described; and we cannot tell which dates are stratigraphically secure because there are no descriptions of the sediments or places from which the samples were taken. Some of the dates in Fig 7 are shown as insecure -- shown in red and green -- because of disturbance or redeposition. I wonder how many of the other dates are really secure? It seems to me that the authors were themselves more than a little confused, and were not at all sure how to relate the dates to the story they were seeking to tell. I suspect the whole thing became far more complex than it needed to be, because of the ongoing attempts to relate all the organic remains and dates to a "history of quarrying."

BRIAN JOHN said...

Between layer 98 ( buried soil with Early Mesolithic oak remains dated to c 7500 BC) and layer 81 (lower topsoil with hazel remains dated to only about 1,000 BC) there is as you say an enormous hiatus of over 6000 years. With no apparent stratigraphic unconformity. The authors of the article have not even drawn attention to that -- so that's a sign of great confusion. The hiatus is of no use whatsoever to the quarrying hypothesis, since why would any quarrymen working here want to remove large quantities of sediment during their operations, if what they were looking for was much easier to obtain by levering stones off the cliff face (which is the scenario MPP and his colleagues talk about)? Doesn't make sense. No -- there must be problems with the samples and the dates.