Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click

Tuesday, 16 December 2014

North Sea Mammoth

Mammoth skull being taken ashore in the Netherlands, having been fished up from the floor of the North Sea.  Apparently there are lots of bits and pieces out there........ fishermen keep on dredging them up....

(BJ Note:  the dating of this find seems to be entirely speculative........)


Fossil hunters searching for ancient relics have found the skeleton of a 40,000-year-old woolly mammoth in North Sea.
The team of archaeologists, salvagers and palaeontologists trawled the waters off the east coast of Britain at a depth of 100 feet.
North Sea Fossils, who are based in Urk, Netherlands, include an expert they call "Mr Mammoth" and are in search of the remains of extinct animals in the dark depths.
Bones of animals including woolly rhinos, Irish elks and parts of the male skeleton of an 11-foot tall woolly mammoth, including its skull and tusks, have all been brought up and collected.
A prehistoric skull of a European bison, also known as a Wisent, was also discovered lying on the North Sea bed.
Carbon dating tests revealed the bones belonged to a mammoth that roamed the planet around 40,000 years ago.
Markus Broch, who works at North Sea Fossils, said it is "extremely rare" to find and later assemble a complete mammoth skeleton.
Mr Broch said: "During the Ice Age there was no sea between Holland and England and these great beasts roamed and died there.
"That is why their bones are still found by boats fishing in the North Sea.
"My father-in-law, who is a fisherman, started collecting these bones at young age because he was fascinated by them, and has now assembled a very large collection
"We started selling duplicates from his collection online some years ago, which went so well that our business have grown and grown.
"Most weeks we go to the fishing ports to meet the fishing vessels and buy the fossils they caught.
"Sometimes we charter a boat of our own and go for special 'fossil hunting' expeditions.
"Because we see so many fossils we work very closely with the leading experts in the field, such as Dick Mol, who is the world's leading authority on mammoths.
"We have assembled a number of complete skeletons of mammoths, something very few companies in the world can do."
The salvagers have managed to piece together the entire mammoth skeleton after initially discovering the skull and tusks of the animal in 2012.
The firm travelled out to sea and recovered a stash of other mammoth fossils using deep sea trawler nets before piecing them together at their base in Urk.
Other items found by the firm include parts of sabre-toothed tigers, the skull of a woolly rhino and the cranium of a reindeer.
Mammoths were first described in 1799 by Johann Friedrich Blumenback, a German scientist.
He gave the name Elephas primigenius to elephant-like bones found in Europe.
The bones belonged to the woolly mammoth which was later considered to be a distinct genus and renamed Mamuthus primigenus.
The species found by North Sea Fossils were known to roam through parts of Central Europe around 40,000 years ago.

Monday, 15 December 2014

Malaspina Glacier, Alaska

I thought this was worth sharing -- a fantastic image of the famous Malaspina Glacier in Alaska -- a classic example of a piedmont glacier in which the ice has poured out from a narrow trough in the mountains and has expanded into a great lobe on the marine foreland.  This glacier has been surging too -- as we can see from the zig-zag pattern of moraines on the ice surface.

The definition on this one (made from Landsat imagery) is amazing -- click to enlarge.

Interview with Jamie Owen

 In case you wondered, this is what happens when a big iceberg rolls.  You don't want to be anywhere in the vicinity when all hell is let loose, especially if you are in a flimsy canvas canoe and have no survival gear.......

I did a very amiable interview with Jamie Owen this morning, on his Sunday radio programme on BBC Radio Wales -- about the new novel called "Acts of God." You can listen to it via this link -- from about 41 mins to 50 mins. Enjoy! Long drive up to Cardiff and back, but a face-to-face interview is so much easier than doing things via that little hell-hole of a studio in Pembs College at Haverfordwest. So the journey was well worthwhile -- especially since I was able to meet up with son Steve after doing the live interview, and enjoy a simple lunch-time repast in the Norwegian Church cafe.....

You can listen here (probably in the UK only):

Cool book on Kindle giveaway

This has nothing whatsoever to do with Stonehenge, but maybe a little bit with the Ice Age........  My new novel entitled "Acts of God", set in East Greenland during the Cold War, is available free (just for 15th and 16th December) in the Kindle version.  You have to download it from the Amazon web page, here:

Here are some of the early review comments:

"I finished the book last night.  Brilliant!"  Gill
A wonderful, intriguing, spellbinding book.  Loved it!"  JB"Couldn't put it down!  I loved the characterisation of the key players in the story, and the interplay between them as the mystery deepened."  Vanya "The plot builds like a great web of deceit and intrigue, weaving around the heroes, drawing them ever onwards and deeper into peril."  Allison "Most enjoyable!  Brian John gives a new meaning to Cold War."  Barrie
The denouement in the final scene was priceless...... I really enjoyed your detailed and descriptive writing style."  Janet
"The cold, clinical, cynical and brutal violence perpetrated by both sides and depicted here is shocking, but honest...... The dangers faced by the expedition members become more than risks of natural disaster, and the story becomes compelling."  Philip

.......and here's a funny thing. When I was making my web site for the new novel, I was hunting for a suitable domain name and came across this one:  Given the topic and the story's location, I had to have it!  So in exchange for a few quid, I am now the proud owner, and my web site has the following URL:

Tuesday, 9 December 2014

The Carn Meini "Bluestone Quarry" -- Oh no it isn't! Oh yes it is!

Here we go again.  After the recent work by geologists Rob Ixer and Richard Bevins which suggested that the spotted dolerites at Stonehenge have probably NOT come from Carn Meini (Menyn), but from Carn Goedog and other outcrops, Profs Darvill and Wainwright have produced a new paper which suggests that the geologists have got it all wrong, and that there was indeed a quarry here.  I venture to suggest that this might well cause some fun and games........

Here is the key info about the paper.

Beyond Stonehenge: Carn Menyn Quarry and the origin and date of bluestone extraction in the Preseli Hills of south-west Wales
Timothy Darvill & Geoff Wainwright
ANTIQUITY 88 (2014): 1099–1114

Recent investigations at Stonehenge have been accompanied by new research on the origin of the famous ‘bluestones’, a mixed assemblage of rhyolites and dolerites that stand among the much taller sarsens. Some of the rhyolite debitage has been traced to a quarry site at Craig Rhosyfelin near the Pembrokeshire coast; but fieldwork on the upland outcrops of Carn Menyn has also provided evidence for dolerite extraction in the later third millennium BC, and for the production of pillar-like blocks that resemble the Stonehenge bluestones in shape and size. Quarrying at Carn Menyn began much earlier, however, during the seventh millennium BC, suggesting that Mesolithic communities were the first to exploit the geology of this remote upland location.

Let's bring a little critical scrutiny to bear on the text of the paper.  On a first reading, these are the things that come to mind:

1.  In the very first sentence, the authors refer to the "80 or so" bluestone pillars at Stonehenge which originated over 220 km away in the Preseli Hills.  How many times must we repeat that there is only evidence for 43 stones?  And how many times must we repeat that not all of them have come from Preseli?

2.  Quote:  "In July 2012 the authors excavated a trench on the southern flanks of Carn Menyn, Mynachlog Ddu, to investigate evidence of stone quarrying and a dolerite-working area. The investigation revealed a well-preserved stratigraphic sequence spanning the period from before 5000 BC through to 1000 BC that provides secure evidence for pre-Neolithic stone quarrying in the region and absolute dates for the extraction of dolerite pillars from a source outcrop high in the Preseli Hills."  Right.  That's a pretty spectacular and confident claim -- let's see how well founded it is.

3.  The authors cite two key findings from the SPACES project in North Pembrokeshire.  First, ".......throughout the study area prehistoric communities had a close relationship with local stone, variously selecting and manipulating blocks for the construction of monuments including portal dolmens, chambered tombs, circles, standing stones, and sometimes just lifting slabs out of the ground as ‘propped rocks’. "  Well, that's a statement of the obvious.  Every community that used stone in megalithic structures had a close relationship with stone.  Nothing special there.  Second, "......within the eastern part of the study area our fieldwork supports a suggestion by Richard Bradley (2000: 92–96) that the arrangement of various bluestone lithologies used in the later stages of Stonehenge broadly replicates in microcosm the actual arrangement of stone types across the landscape of the Preseli Hills and surrounding areas. Thus, the dolerites of the Bluestone Horseshoe in the centre of Stonehenge derived from the central Preseli Ridge, while the various rhyolites and tuffs present in the Outer Bluestone Circle originated at outcrops within a wider catchment ......."  We can't prove things one way or the other, but this seems to me to be fanciful twaddle.  The stones that we know about -- all 43 of them -- were moved about all over the place, and they stood in a variety of settings before the one whose traces we see today.  It is far more likely that the use of dolerites in the bluestone horseshoe was a practical matter related to HARDNESS, with the more crumbly and flaky (inferior) stones relegated to the bluestone circle.  I find it very hard to believe that every stone at Stonehenge was known to the builders -- many generations after their first use on the site -- as having come from specific Preseli locations.

4.  On the matter of dolerite / spotted dolerite origins, the authors take issue with Bevins and Ixer:  "......further informed sampling is needed, and Bevin et al’s recent publication can be taken as an alternative rather than a revised interpretation of the Open University’s datasets (Bevins et al. 2014: 181, 192). Moreover, as only around 55 per cent of the 21 Stonehenge samples in the study (including unattributed debris as well as identified extant pillar-stones) can be attributed to a source at Carn Goedog (Bevins et al. 2014: 189), any claim that this was the main source for the Stonehenge bluestones must be treated with extreme caution."  I will leave it to the geologists to sort out that particular issue.  Plenty of other issues to examine....

5.  Quote:  "Archaeologically, our surveys show that Carn Menyn was the focus of a great deal of activity in the later Neolithic and early Bronze Age. Burial cairns have been recorded at either end, standing stones on the outcrops, a walled enclosure around the highest point, and natural springheads elaborated through the creation of pools and the occasional application of rock art on the southern side."  As I have said before on this blog, I disagree with all of that.  Carn Menyn (Meini) was not a focus of any sort, and there is nothing in the landscape to suggest that it was.  There are scattered megalithic and other archaeological features right across this landscape in eastern Preseli, and in all compass directions away from Carn Meini.  The springheads and "pools" are equally fanciful, and I have seen no convincing evidence that they were either fashioned or modified  by human beings, or revered........

6.  Quote:  "The surveys found that on the southern flanks of Carn Menyn there was a scatter of broken or abandoned dolerite pillar-stones of the same size and proportion as the stones present in the two visible structures at Stonehenge today (see Figure 2), as well as occasional hammer stones."  There is an extraordinary diagram -- Figure 2 --  purporting to support this hypothesis, on which stone widths and thicknesses are plotted, but not stone lengths.  There is, as you would expect, a wide scatter -- but the most extraordinary feature of the diagram is the plotting of the dimensions of abandoned pillar-stones (some broken) on the slopes of Carn Menyn.  This is about as unscientific as you can get.  Who chose these stones?  Where were they?  How many were sampled and how many others were ignored because they were "inconvenient"?  As far as I am concerned, this whole exercise is nonsensical.

7.  Now we come to the "Carn Menyn Quarry Sequence" -- on page 1103.  Note that it is designated as being a quarry before we have even looked at any evidence which might inform our opinions.  That appears to be common fault among quarry hunters -- including our friends from the rival tribe who have been digging at Rhosyfelin.

8.  With reference to the key "quarrying" site at SN 143324, the authors claim that "....shallow hollows suggestive of quarry pits were also recognised and, on the basis of surface evidence, seemed to be for the extraction of a fine, light-grey coloured meta-mudstone (Darvill et al. 2008). Surface evidence including a broken pillar-stone, intercutting quarry pits and indications of dolerite extraction on a terrace on the southern slopes of Carn Menyn at an altitude of 310m asl........"  A 30 sq m pit across the terrace is claimed to show three main periods of activity associated with the working of meta-mudstones and spotted dolerites.  It is claimed that the first workings on the site were for the extraction of meta-mudstones, and that there are at least a dozen pits along the edge of a dolerite dyke which are associated with this phase.  Darvill and Wainwright claim that fire-setting was a part of the extraction process, and they present four radiocarbon dates on the "abundant charcoal from oak stick-wood" found in the holes.  There are two radiocarbon dates from the deepest part of the pit -- 7987 yrs BP and 7711 yrs BP -- which are surprisingly old, and two others, one from 6170 yrs BP and the other from 6396 yrs BP.  The authors also claim to have discovered hammer stones and flakes from the quarrying operations, although we are not shown any evidence in support of this contention.  On the plan of the site, the authors show stone piles / small cairns (?) and also a spread of meta-mudstone knapping waste and two low-walled huts or shelters (?).  They also show three broken dolerite pillar stones and two complete dolerite pillar stones, in an area where scores of stones could have been represented if they had chosen to do so.  What should one make of all this "evidence"?  Personally, I am not convinced that we are looking at any evidence of quarrying activity in the period 8,000 - 6,000 yrs BP.  There are undulations and pits everywhere in this landscape -- as far as I am concerned, they are not noteworthy.  We know that parts of these uplands were wooded during the early part of the Holocene, before climate change and grazing caused the woodland edge to retreat downslope.  The name "Carn Goedog" means "Woodland Crag" -- and that's rather suggestive of quite a late woodland survival.  Could the charcoal have come from natural fires or man-made clearance fires in the woodlands on the ridge crest?  Perfectly feasible.  Alternatively, we may be looking at charcoal left in fire pits which were used at Mesolithic or early Neolithic camp sites established here in the vicinity of the Carn Meini crags.  Why would anybody want to use fire to extract slabs of meta-mudstone when it is so broken and shattered anyway in this area that you just have to walk along and pick it up......?

9.  Next, the authors claim to have evidence for "the working of dolerite" in the later third millennium BC.  They claim to have found a shallow socket once used for a standing stone, which lies "fallen to the south."  They also claim to have exposed packing-stones around the base of the stone, and illustrate this in Figure 7.  The base of this stone also supposedly shows a "half-sectioned socket" -- whatever that may be.  I find none of this convincing.  The "socket" appears to be entirely natural, and the "packing stones" -- carefully left in place while other stones have been removed -- seem to be in quite the wrong positions to have been packed into a socket holding a standing stone.  I think we are looking here at yet another archaeological artifice, like those created by Prof MPP and colleagues at Rhosyfelin.  "Oak stick-wood charcoal" from the fill of the socket gave three radiocarbon dates of 4188 yrs BP, 3797 yrs BP, and 3724 yrs BP.  (Note that these dates are generalised -- the margins of error are cited in the paper.)  So what does this tell us?  Not a lot, except that there seems to have been a pit here with occasional fires over a few centuries around 4,000 years ago.

10.  Next, we have the so-called evidence of dolerite quarrying.  Quote:  "An area of preserved old ground surface towards the southern end of the trench (see Figure 4 for position) contained a scatter of spotted dolerite flakes and hammer stones with evidence of burning directly associated with it."  Once again, we are not shown the evidence -- we are just told that it exists.  Not good enough.  There are three more dates from this area from oak charcoal, namely 3685 yrs BP, 3673 yrs BP, and 3567 yrs BP.  The authors say:  "These are the first secure dates for prehistoric dolerite working in the Preseli Hills and clearly indicate that Carn Menyn was being actively exploited in the late third millennium BC."  I'm sorry, but I see no evidence at all which supports that contention.  All I see -- in the evidence on the ground and in the photos figured in the paper -- is a chaotic jumble of dolerite fragments and "meta-mudstones" dramatically affected by frost shattering and other natural processes, with occasional evidence for the use of fire -- possibly in association with camp sites.  We do not know whether the evidence of fires in pits is unique to this area, or whether it occurs in close proximity to all the other rocky outcrops in eastern Preseli.

11.  Quote:  "The third and final period of activity represented in the Carn Menyn Quarry sequence again relates to the extraction of meta-mudstone. The earlier quarry was more or less silted- up by the end of the second millennium BC, but a new pit appears to have been dug to the south, partly overlapping its ancient predecessor." No evidence is provided by the authors as to the characteristics of these layers, and it is impossible to ascertain whether they are natural or man-made.  The assumption seems to be that they are man-made because they are on top of other layers that are also deemed to be man-made -- and we end up in a classic circular argument.  There are two charcoal dates from this supposed late phase of meta-mudstone working:  2979 yrs BP and 2871 yrs BP.  These are deemed to be related to two other dates -- one from the "large cairn" investigated at the western extremity of Carn Meini (3073 yrs BP) and a date from Croesmihangel not far from Foel Drigarn (3509 yrs BP). 

12.  In their discussion of the results (p 1109) the authors demonstrate that they have several problems to cope with.  They state:  "The main stratigraphically determined periods of activity described above appear to be more or less discrete episodes spatially connected by the power of place."  Excuse me, but what is that supposed to mean?  The assumption is that there were two very early phases of meta-mudstone extraction -- around 9000-8000 years ago and 7800-6000 years ago.  Quote:  "These early dates make the Carn Menyn Quarry the earliest-recorded securely dated stone extraction site in Britain."  I think we will beg to differ on that one, pending the presentation of some convincing evidence.  Quote:  "On a wider front, the discovery of formal quarrying in the British late Mesolithic adds significantly to the growing list of monuments and structures from this period."  A rather grandiose claim based upon the flimsiest of evidence.  The authors then seek to link these early dates with similar dates from the Stonehenge landscape:  "The extension of the cultural sequence at Carn Menyn back into the sixth and fifth millennia BC brings the pattern of activity there into close accord with what is known of the Stonehenge area, and begins to flesh out the bare bones of parallel but connected developments in the two areas."

13.  Quote:  "The second main period of activity at the Carn Menyn Quarry also divides into two phases: the erection of a standing stone and dolerite-working. Modelling suggests that the standing stone was set up before the dolerite-working took place....".   The modelled date for the assumed erection of the standing stone is between 6,000 yrs BP and 4640 yrs BP --  far too wide a span to be meaningful.  The modelled date for dolerite working is between 4,000 yrs BP and 3,800 yrs BP, also with much uncertainty.  It will not go unnoticed that this very late date for dolerite working does nothing whatsoever to support the thesis that this was a quarry used for spotted dolerites destined for Stonehenge.  While there are subtle differences in interpretation, it now seems to be widely accepted that the bluestones were present in the Stonehenge landscape before 5,000 years BP.

14.  Quote:  "These findings finally lay to rest the theory that the bluestones arrived on Salisbury Plain through glacial action (Kellaway 1971), an idea that has been remarkably persistent and periodically revived (e.g. John 2008) despite being comprehensively discredited by geologists, geomorphologists and glaciologists more than a decade ago (Green 1997: 264; Scourse 1997; Clark et al 2004; Bowen 2005: 147–48)."  Excuse me, chaps, but that is utter nonsense.  Which geologists and glaciologists have "comprehensively discredited" the idea of glacial transport?  Not one, that I can think of.  The only glaciologists who have expressed a view have come down with a statement that glacial transport would have been perfectly feasible. The cited authors are all geomorphologists, and with the best will in the world they have not done any comprehensive discrediting of anything.  They have expressed their views, and I respect them, but in my view their arguments are not well supported. Trust me -- I'm a geomorphologist too.

15.  The authors argue that there is some significance in the "re-working" of the Carn Menyn site, and in the construction of the Carn Menyn cairn and the Croesmihangel round barrow at the western and eastern ends of the dolerite outcrops.  Another extraordinary flight of fancy.......

16.  I'll quote the whole of the final paragraph of the paper:
"Many explanations as to why the bluestones were considered sufficiently important and meaningful to move from Wales to Wiltshire can be proposed, and there may be more than one reason. The demonstrable antiquity of stone extraction on Carn Menyn, long before the building of Stonehenge began, tells us something about the ancestral significance and power of the landscape from which the bluestones were taken. Perhaps Mynydd Preseli was the home of the gods: the Mount Olympus of Neolithic Britain. But we also believe that the association between bluestones and healing springs in the Preseli Hills was important (cf. Jones 1992), and something that resonates with long-standing oral traditions that were first written down in the thirteenth century AD (Piggott 1941). Springs were a significant and persistent feature of the Stonehenge landscape, as the recent work at Blick Mead shows (Jacques et al. 2012). Soon after the bluestones were installed at Stonehenge (Stage 2) the central structure was linked by an Avenue to Stonehenge Bottom and the River Avon (Stage 3), thereby fixing and formalising the relationship to water (Darvill et al. 2012a: 1035). The idea that powerful stones were moved from their source outcrops on a special, ancestral or sacred place to ‘franchise’ distant shrines and temples finds parallels in West African societies and elsewhere (Insoll 2006). We propose that, after the earthwork enclosure at Stonehenge ceased to be a major cremation cemetery sometime about 2500 BC, bluestones from Carn Menyn and other nearby outcrops in west Wales were brought to Stonehenge and set up within a temple whose structure had already been built from sarsen stones. From that time onwards, pilgrims and travellers were drawn to Stonehenge because of the special properties that had empowered Stonehenge to provide pastoral and medical care of both body and soul: tending the wounded, treating the sick, calming troubled minds, promoting fecundity, assisting and celebrating births and protecting people against malevolent forces in a dangerous and uncertain world. The bluestones hold the key to the meaning of Stonehenge,
and Preseli was the special place from whence they came at a high cost to society in labour and time, as befitted such important talismans."

The authors are still wedded to the healing springs and healing stones idea, in spite of the fact that there is no evidence in local folklore or archaeology to support the hypothesis, and no evidence of spotted dolerite being specially revered and preferentially used in megalithic structures in North Pembrokeshire. 


Some interesting dates, but whatever went on at Carn Meini, it certainly had nothing whatsoever to do with Stonehenge.

Thursday, 27 November 2014

Flat Holm Erratic Hunt (8): some interesting pebbles

Have a good look at these, folks.  Picked up on the beaches of Flat Holm by Linda, Sid, Chris and myself -- and all now being analysed by Sid and some of his colleagues.

Some of them look very interesting indeed, suggesting either W Pembs or Anglesey in the frame as possible provenances.  Click to enlarge.  Watch this space............

Wednesday, 19 November 2014

Flat Holm Erratic Hunt (7): the geomorphology

 Flat Holm seen from the NW -- in this photo the west side of the island is on the right -- note the overall roche moutonnee form.

As mentioned in earlier posts, Flat Holm is a relatively low island, almost circular, and just over 600m in diameter.  There is a gentle slope from the more exposed western shore up towards the eastern cliffs -- and it is on the east that the highest land on the island is to be found.  The highest point is only 32m above sea-level, but because the tidal range is so large here -- up to 15m on some spring tides -- the island expands and contracts rather spectacularly every day.......

As noted in earlier posts, the island has an ideal roche moutonnee form which matches perfectly the passage of ice across the island, moving from west towards east on several occasions during the Ice Age.  However, it would be a mistake to attribute the form of the island entirely to glacial processes, since the main geological features are a series of pitching anticlines and synclines running broadly NE-SW -- and these features, above all else, explain "the lie of the land."  There are extensive exposed bedrock surfaces on the western side of the island between the tide marks.  Scrambling about beneath the cliffs is more difficult on the south coast, and more difficult still on the east side of the island, where cliffs and thick vegetation make exploring an occasionally hazardous occupation.

The western side of the island is a geological paradise, with abundant fissures, faults, folds, thrusts and anticlinal and synclinal structures easily accessible -- alongside many variations in rock type.  The rocks all belong to the Carboniferous series, but in addition to "classic" hard grey limestones there are also mudstones, cherts, oolites and also veins of calcite and post-Carboniferous weathering and residual products exposed particularly in fissures and gullies in the cliff face. 

The most famous surface features are the large ripple marks exposed on the shore platform to the west of the farmhouse.  They have been exposed as a result of the breaking up and stripping off of overlying strata -- partly by glacial processes and partly by wave action.

Some of the large ripple structures on the west side of the island.  A perfectly preserved Carboniferous sea floor......

 Steeply dipping bedrock (mudstones, shales and sandy layers as well as interbedded limestones) near the SW corner of the island.  The upper 2m or so of the bedrock exposure is broken up by periglacial and slope processes;  there are signs of frost heave features.  At the top of the cliff is a thin sandy loam incorporating windblown material.  This is probably Holocene.  In the gully in the middle distance there is a plug of reddish material which may be of Triassic age; but there is much debate about this.......

Around the whole coast of the island there are traces of a raised beach platform -- or more likely, several of them.  Structural controls are so dominant that these fragments are difficult to identify with any certainty -- but they occur at all sorts of altitudes from mean tide level up to about 3m above extreme spring HWM.  Trying to match these traces with the raised beach platforms of Pembrokeshire (for example) is very difficult, because of the vast tidal range here in the Severn Estuary.  The best preserved raised beach platform is about 2m - 3m above extreme HWM, on the cliffs at the SE corner of Coal Beach.  The platform extends towards Point Bay.  This is what it looks like:

Sid Howells on the raised beach platform which runs for almost 100m along the cliffs near the eastern extremity of the island.  The surface is irregular, but it is a well-pronounced 
feature up to 4m wide.

There is also a modern wave-cut platform which is occasionally more than 100m wide, cut by a combination of marine solutional processes and  abrasion as blocks and pebbles are moved about by waves and tidal rises and falls. Parts of this platform are well covered with rocky debris and pebbles, but occasionally it might be exposed, as in this photo of Point Bay, as seen from the clifftop near the Foghorn.

Because the whole island is made up of calcareous rocks with complex structures and abundant fissures, it is inevitable that there are tunnels, caves and solutional hollows and collapses all over the place.  Some of these have been used for the exploration of past inhabitants for lead and other minerals -- and indeed for the exploitation of mineral finds.    Above the raised beach rock platform between Coal Beach and Point Bay, there are two tunnel entrances.  It's thought that one of them is natural and the other man-made -- but to me it looks as if both might be natural but maybe enlarged by those in search of mineral wealth.  This is the entrance to one cave.  It looks very similar to the caves of Gower, South Pembrokeshire and Caldey Island -- and it is quite possible that prehistoric layers might be present and worthy of examination.

Castle Rock is a spectacular double stack with an old cave system at its centre.  It is being whittled away by marine processes, and at any moment -- probably during some storm bringing big waves in from the north -- the tops of both stacks will slide into the sea, along old bedding planes which can easily be seen from the beach below.

 Finally. a word about the solutional features which are particularly prominent around the southern shores of the island where the massive limestone beds of the Birnbeck Limestone are exposed.  We can refer to these features as "karren".  They incorporate jagged raised surfaces and complex and intertwining channels which are sometimes almost a metre deep.  mechanical abrasion does not seem to be very active in most cases-  these are straightforward solutional features.  The edges of the ridges are often razor-sharp -- capable of ripping boot soles to shreds, not to mention hands, if you are unwise enough to lose your balance when hopping around on the ridges........

Conclusion:  Plenty of geomorphology to get your teeth into here, not to mention classic geological features.  Interestingly enough, Sid, Chris and I did not identify a single in situ glacial or fluvio-glacial deposit on the island cliffs.  That confirms, in my mind, that Devensian ice probably did not reach Flat Holm.  But there are erratics everywhere, and in several places we see deposits that look like very ancient glacial deposits that have been eroded and modified over a long period of time.  The best guess is that they are Anglian in age, and that it was the Anglian Glaciation that carried those thousands of erratics from the far west into the vicinity.