One of the most bizarre features of the glacial transport / human transport debate is the insistence of the HT advocates that the Stonehenge bluestones are freshly quarried monoliths that just happen to be somewhat weathered. Their narrative requires quarrying from special places -- but of course there is no evidence at all that Rhosyfelin or Carn Goedog were "special places" in Neolithic times, and neither foliated rhyolite or spotted dolerite were ever used preferentially in West Wales by the builders of the megalithic structures. And as for the evidence of quarrying, we all know that it is so thin that it cannot withstand scrutiny, as Dyfed Elis-Gruffydd, John Downes and I demonstrated in two papers in 2015. (For a decade, these highly inconvenient papers have been entirely ignored by MPP and his associates. Make of that what you will.) Indeed, our careful analysis of the "quarrying features" showed them to be entirely natural and unexceptional. The sedimentary sequences at the two sites, and the radiocarbon age determinations, also fail to demonstrate that there ever were obvious "quarrying episodes" in the time frame desired by MPP and his colleagues.
Now the narrative appears to incorporate other Neolithic quarries and other stone circles as yet undiscovered, at sites that are deemed (by modern archaeologists) to have been sacred or special. Fantasy rules, at every stage of the narrative.
The stone provenancing work by Ixer, Bevins and associated colleagues is interesting in demonstrating a "North Preseli" connection with Stonehenge, but it is a good deal less definitive than they would have us believe, and it tells us nothing at all about how boulders, smaller stones, cobbles and fragments of many different rock types may have travelled from A to B. It is one of the most unfortunate features of this debate that the geologists from an early stage decided to side with the HT proponents and to promote the view that GT was impossible. It is even more unfortunate that they decided to support the view that the bluestone monoliths were taken from Neolithic bluestone quarries rather than being collected as boulders from an erratic-strewn landscape.
So what about the Stonehenge bluestone monoliths? As night follows day, they are obviously NOT freshly quarried blocks. Some of them have been tooled and shaped, like the dolerites in the Bluestone Horseshoe, but to pretend that the other boulders, blocks and slabs were transported as targetted and freshly quarried blocks is to deny everything we know about weathering and erosional processes. The facets, the abraded edges and the weathering characteristics all indicate glacial entrainment, transport in a dynamic sub-glacial or englacial environment, and long exposure to weathering processes. By this I mean tens of thousands of years at the very least.
It is disingenuous of the HT brigade to pretend that the rounding and weathering of the Stonehenge bluestones might gave occurred over the last 5,000 years or so, and that in scale and character it is similar to that displayed on rock surfaces at Rhosyfelin and Carn Goedog and on the surfaces of the Stonehenge sarsens. In arguing that way, they are making my point for me, since the bedrock surfaces, and the surfaces of the sarsens, are the results of very long exposure to the elements. HH Thomas accepted this point a century ago, when he argued that the Stonehenge bluestones were not quarried but picked up from an erratic scatter somewhere on the south side of Preseli.
It is really rather weird that the earth scientists who belong to the "group of eleven" who have so recently attacked me and my work on the Newall Boulder should apparently be so naive about the physical processes that operate on rock surfaces. They claimed that the Newall Boulder was simply the broken off top of a rhyolite monolith which has subsequently suffered from a certain amount of weathering. As I have demonstrated, it is a great deal more complicated than that, with both weathering and erosional features demonstrating a complex transport and emplacement history in which glacier ice almost certainly played a part. The apparent lack of clear glacial striations on the boulder cannot be used as part of an argument against glacial transport, as every glacial geomorphologist knows.
As I have indicated in my recent publications, the shapes and surface characteristics of the Stonehenge bluestones are entirely consistent with glacial entrainment, glacial transport, dumping in locations still te be determined, and then long exposure to atmospheric weathering processes. The boulders might even have been entrained, transported and dumped on multiple occasions. There is a vast literature on glacially transported clasts, as demonstrated by stone shape, sphericity, surface roughness and other measures. See the work of Prof David Evans and many others. These are quotes from my 2024 Newall Boulder paper:
https://doi.org/10.5194/egqsj-73-117-2024
Clasts occupy a wide range of positions in mobile subglacial till (Evans et al., 2016, 2018). They are subject to complex transport histories that involve variable amounts of dragging, rolling and lodging, during which they are subject to surface modification through inter-clast collisions and contacts. Any single clast may be reworked numerous times during successive glaciations. Because clasts will tend to take the line of least resistance to the flow of the surrounding deforming till matrix, facetted and bullet or wedge shapes are developed. Whenever a clast is disrupted from its lodged position, it can be subject to fresh fracturing, gradually changing its overall shape to one of a block (Boulton, 1978; Benn and Evans, 1996; Evans, 2018). Although not all glacially transported clasts display such bullet or flat-iron shapes, such an appearance is diagnostic of significant subglacial transport (Evans, 2018; Evans et al., 2006).
............. Overall, the surface characteristics of this boulder suggest that it is a discrete erratic that has been transported for much if not all of the time in a subglacial position (Benn and Ballantyne, 1994; Lukas et al., 2013; Benn and Lukas, 2021).
It should be noted that most of the 43 bluestone “monoliths” at Stonehenge are not elongated elegant pillars (as portrayed in most reconstructions) but heavily abraded unremarkable boulders and elongated slabs. There are clearly defined facets, some of which are rough and others smooth. There are few sharp edges. The stones would not be out of place in the morainic accumulations around any glacier snout in the world (Benn and Evans, 2010, and references therein). They look like glacial erratics, and they are heavily weathered as a result of prolonged exposure (Fig. 14). On some weathered surfaces segments of the crust have peeled away and have been lost. It is probable that Stonehenge was built where the stones were found, as suggested by Judd (1903) and Field et al. (2015), and this is supported here by the preliminary analysis of the Newall Boulder.
In addition, I have done post after post on this blog, making the point that most of the Stonehenge bluestones are not pillars, and neither are they sharp-edged quarried blocks:
If they were quarried, they would look like the blocks in these wondrous artists impressions. The upper one was drawn to illustrate the Rhosyfelin "quarry" with the approval of MPP, for a Stonehenge exhibition in Belgium in 2018.
Whatever the flights of fancy and scale distortions might have been in these reconstructions, the detail relating to the extracted block edges is quite correct: they are always sharp and clearly defined.
Next, let's look in more detail at the methods employed by geomorphologists in defining clast shapes. In my paper on the Newall Boulder I referred to the scheme developed by Powers (1953):
Powers, M. C.: New roundness scale for sedimentary particles, J. Sediment. Res., 23, 117–119, 1953
(after Krumbein and others)
The shape of blocks, pillars and slabs extracted from bedrock outcrops will vary according to fissures and fracture patterns within the rock; some rocks are massive and coherent, with few internal weaknesses, while others (like shales, mudstones and maybe even foliated rhyolite) will break down into slabs, sheets and plates such as we see on slate quarry spoil heaps. We must also take account of surface roughness in assessing clast origins. In general, quarried blocks and slabs will be classified, on this scheme, as angular, on the left edge of this diagram. But the stonehenge bluestones occupy quite different positions on the diagram, mostly in roundness categories 0.7 (rounded) and 0.9 (well rounded) but with some fresher and rougher facets such as those observed on glacial erratics.. This is not a consequence of weathering, but an indicator of travel distance, breakage and erosion.
Finally, there are three pieces of evidence that allow us to reject the quarrying hypothesis without further ado.
1. If Parker Pearson and his colleagues are to be believed, the rounding and abrasion which we see on the standing bluestones today are the result of "weathering" in the time that has elapsed between stone extraction and the present day. That involves a fundamental misunderstanding of the word "weathering", but we'll let that pass for now. More to the point, all of the excavations which have revealed fallen and buried bluestones suggest that they are just as abraded, rounded and weathered below ground as above ground, with some rougher surfaces on facets such as we see on glacial erratics close to current glacier fronts. That means that (with the exception of a few worked stones) their shapes were already established prior to erection in the stone settings. That means they were not installed as fresh quarried blocks, but gathered up as weathered and abraded boulders from the landscape as suggested by HH Thomas, Kellaway, Thorpe et al, and Field. The MPP claim that the bluestones were pre-used in lost stone circles does nothing to support the quarrying hypothesis.
The "proto-orthostst" at Craig Rhosyfelin. The sediments that have accumulated around and above the slab since the Early Bronze Age are clearly displayed.
2. The famous 8-tonne proto-othostat found at Rhosyfelin and flagged up as "intended for Stonehenge" was discoverd through radiocarbon dating to have been emplaced during or later than the Bronze Age. Some charcoal found beneath it was radiocarbon dated to the Early Bronze Age. So it cannot possibly have had anything to do with Neolithic quarrying at the site. But because it is a rockfall slab which has crashed down from the higher part of the rock outcrop, and because it has been there for more than 3,000 years, its condition is of considerable importance. I have analysed it in detail:
https://brian-mountainman.blogspot.com/2015/05/the-famous-rhosyfelin-proto-orthostat.html
It is very fresh in its appearance, with very little rounding off of sharp edges or other weathering traces in spite of exposure to the atmosphere and to other processes during and after burial by slope deposits. This reinforces the view that the Stonehenge bluestones carry surface features that are not just 5,000 years old but are the result of tens or hundreds of thousands of years of exposure.
Rock surfaces on the Pentre Ifan cromlech. It is now suggested that the pillars and capstone were not buried for any great length of time. After thousands of years of exposure to weathering, the smoothed and abraded faces, and those damaged by fracturing, are remarkably fresh.
3. It is instructive to examine the surfaces of the capstones and supporting pillars of Pembrokeshire cromlechs like Pentre Ifan, Carreg Samson and Carreg Coetan Arthur. The stones used by the builders were all large erratics of rather local origin and collected in the neighbourhood. The stones are weathered but in places seriously damaged by fracture scars -- in other words, the features attributable to glacial processes and periglacial modification (frost damage) are beautifully preserved. These cromlechs are approximatelt the same age (or maybe somewhat older) as the bluestone stone settings at Stonehenge. Over 5,500 years or so of exposure, there has been weathering, but there is no sign at all of weathering on the scale which Bevins et al (2025) require for the creation of the facets and smoothed surfaces of the Newall Boulder.
To sum up, the bluestone quarrying hypothesis is not worth the paper it is written on, and neither is the contention that smoothed rock surfaces are the result of post-Neolithic weathering processes.
No comments:
Post a Comment