"Chips off the old block: the Stonehenge debitage Dilemma", by Rob Ixer and Richard Bevins, Archaeology in Wales 52 (2013), pp 11-22
Within this century there has been a renewed interest in the lithology of the Stonehenge bluestones, both for the standing orthostats and also for the vast numbers of broken bluestone material, now referred to as debitage. Increasingly it has been recognised that there are a number of interesting problems associated with this debitage found within the ‘Stonehenge Landscape’, most notably their original geographical provenance, their internal Stonehenge provenance (matching debitage to parent orthostat), the reason for their presence and ﬁnally explanations for the apparent mismatch between the lithologies of the (above-ground) bluestone orthostats and the debitage both in terms of type and numbers. A fundamental initial step in answering most of these questions is to try to match debitage fragments from well constrained contexts to their parent orthostat.
So the debitage (c 4000 rock fragments and c 100 thin sections examined) is the focus here.
The authors also state, with respect to origins:
In relation to the explanation for the debitage, amongst the main anthropogenic contenders are the following: (a) that it is wastage from the dressing of the orthostats, (b) that it is true debitage associated with the later reuse of the orthostats as ‘quarries’ for axe manufacture, (c) that it is made up of ‘knock-offs’ from later souvenir hunters or amulet collectors. The favoured non-anthropogenic explanation is that some of it comes from (glacial) erratic background material, some of which was not incorporated into the Stonehenge stone settings (John, 2008). Of course, it is quite possible that all of these explanations are partly correct; they are not mutually exclusive.
With resepect to the main Stonehenge bluestone lithologies, they say:
The main bluestone orthostat lithologies are either spotted or non-spotted dolerite (the authors suggest 3 groups -- BJ) but within the outer bluestone circle there are 12 non-dolerite bluestones (used here in the sense of any non-sarsen, proven or potential, Stonehenge orthostat material), including both standing orthostats (SH38, 40, 46 and 48) and buried stumps (32c, 32e, 33e, 33f, 40c, 40g, 41d, 42c) (Atkinson, 1979). Of these, 32e is described as a rhyolite, 40c as a calcareous ash, 40g and 42c as micaceous sandstones and 32c, 33e, 33f and 41d as altered, dark olive-green ash (Atkinson, 1979; Thorpe et al 1991). In addition the Altar Stone is a calcareous sandstone of probable Devonian age and unlike any other lithic from Stonehenge (Ixer and Turner, 2006).
The bluestone debitage comprises spotted and non-spotted dolerite, a restricted set of rhyolite and rhyolitic tuffs, informally known as ‘rhyolite with fabric’ and more formally as Rhyolite Groups A –E (Ixer and Bevins, 2011b), a variety of argillaceous and calcareous tuffs (informally known as ‘volcanics with sub-planar texture’), and a numerically far smaller group of sandstones including (Lower) ‘Palaeozoic sandstone’ and ‘micaceous sandstone’. Other non-bluestone lithologies are very rare and mainly restricted to disturbed or modern contexts and are not discussed further.
The authors are circumspect, but from previous work there appear to be at least 15 different lithologies in the frame. There appear to be nine different rhyolites -- represented in the orthostats and in the debitage. The Altar Stone (Devonian sandstone) is unique among the orthostats, and there are just 3 debitage fragments that appear to match it. All the other sandstone debitage fragments are from other sandstones -- probably Lower Palaeozoic, and possibly from North Pembrokeshire........
Rhyolite orthostats 38, 40 and 46 appear to be different, and unusual in that there appears to be no debitage related to them. Orthostat 48 (made of Group E rhyolite) does have some debitage related to it. There are abundant fragments of debitage in Rhyolite Groups A-C -- assumed to have come from Craig Rhosyfelin, but as yet no related orthostat has been found. The authors speculate in this paper, not for the first time, that there may be a match either in stump 32d or 32e.
The conclusion of the paper is as follows:
Although the evidence is very incomplete the hypothesis is, that, for the non-dolerite bluestones, above-ground orthostats have no debitage and so have suﬀered little systematic removal of material, (the recent observation by Abbott and Anderson-Whymark (2012, 25) that the bluestone circle bluestones are largely undressed partially supports this suggestion) whereas the most abundant classes of debitage belong to (now buried) ‘slighted’ orthostats and are the result of a purposeful destruction possibly by those with an axe to grind. But here is the rub; most of the ‘slighted’ orthostats comprise ashes, tuffs (‘volcanics with sub-planar texture’) and sandstones, ‘soft’ lithologies that would be difficult to work into tools. These proposals can, should and will be further tested.
As for the future, the authors say:
Sampling that would provide longer term provenancing data should begin with buried orthostats SH40g and SH42c, noted by Atkinson as micaceous sandstone. This would allow comparison of these two orthostats with the Altar Stone and with the (Lower) ‘Palaeozoic sandstone’ debitage to determine if either is the parent for any of the sandstone debitage. This should then be followed by sampling buried orthostats 32c, 33e, 33f and 41d, noted by Atkinson as altered, dark olive-green ash. This would allow comparison of these with two or more classes of ‘volcanic with sub-planar texture’ debitage, again to establish any relationship. Finally, sampling the remaining standing and buried dolerite orthostats would allow for new petrographical and geochemical analyses to complement the on-going programme of sampling in situ Preseli sources.
All in all, another interesting piece of work, confirming the very large number of lithologies represented among the bluestone orthostats and the bluestone debitage, and confirming the point that much of the debitage has not apparently come from the dressing of stones still present in the bluestone settings. Quite reasonably, the authors therefore suggest that many stones might have been completely smashed up, and that the debitage comes largely from those. I would have liked more discussion of non-anthropogenic origins for the debitage -- maybe we would have had it if the paper had been submitted to a geological journal instead of an archaeological one. From where I stand, I still see an assemblage of erratic materials that have come largely from West wales. I also see considerable areas of the Stonehenge landscape that have not yet been excavated -- and I assume that new and undiscovered rock types may well be represented in these areas. The number of lithologies represented in the Stonehenge landscape seems to be going up all the time, and there is a lot of provenancing still to be done. And EH must get up off its backside and accept that if some of the major problems surrounding the bluestones ever are going to be answered, there MUST be a proper sampling programme on the bluestone orthostats themselves. ALL OF THEM!