Isostatic recovery, Bathurst Inlet

Worth sharing -- two beautiful images of raised marine features (including raised beach ridges and washed surfaces) in Bathurst Inlet, Arctic Canada

Hudson Bay isostatic uplift

The rate of isostatic uplift  / recovery in the inner reaches of Hudson Bay turns out to be far in excess of what I anticipated. According to Lajeunesse and Allard, the rate of uplift immediately following deglaciation was around 7m per century.  You can see this on the steep part of the curve, associated with the initial ice melt around 8600 years ago. This rapid rate gradually fell off over the following millennia.  Note that the curve shown on the graph above shows an initial rate of about 2.5m per century.  But that shows the RELATIVE sea-level curve, after taking into account the fact that there was a quite rapid eustatic sea-level rise going on at the same time, associated with global ice melting and the return of vast quantities of meltwater to the world's oceans.  So sea-level was rising, but the land was rising even faster..........

Géographie physique et Quaternaire

Volume 57, numéro 1, 2003, p. 65-83

Late Quaternary Deglaciation, Glaciomarine Sedimentation and Glacioisostatic Recovery in the Rivière Nastapoka Area, Eastern Hudson Bay, Northern Québec

Patrick Lajeunesse et Michel Allard

http://www.erudit.org/revue/gpq/2003/v57/n1/010331ar.html?vue=figtab&origine=integral&imID=im17&formatimg=imPlGr

Raised shorelines, Polar Bear Provincial Park, Ontario

 

Polar Bear Provincial Park lies on the corner of James Bay, where it opens out into Hudson Bay proper.  This area has one of the highest rates of present-day isostatic recovery / land uplift anywhere in the world -- thought to be about 1.2m per century.  Not surprisingly, this low-lying landscape, at least in the coastal zone, is dominated by raised marine features.  

In the top photo (a vertical satellite image) we can see beach ridges galore and even old spits with arcuate tips. I'm not sure what the altitude of the marine limit is here, but I would guess it to be 100m at least......

In the lower photo, an oblique aerial photo, you can see to the right an area which is above the marine limit, with no raised marine features, and on the left a landscape dominated by beach ridges -- hundreds of them, following the contours of the landscape and stepping down all the way to present sea-level.

==================

Postscript, 17th August 2014.   I underestimated the altitude of the marine limit pretty drastically.  Not far away, in the Rivière Nastapoka area, eastern Hudson Bay (Quebec) the marine limit is at 248m, and there are abundant signs in the landscape of a dramatic inundation by the sea particularly beneath an altitude of 205m.  See this paper:

Géographie physique et Quaternaire

Volume 57, numéro 1, 2003, p. 65-83

Late Quaternary Deglaciation, Glaciomarine Sedimentation and Glacioisostatic Recovery in the Rivière Nastapoka Area, Eastern Hudson Bay, Northern Québec

Patrick Lajeunesse et Michel Allard

http://www.erudit.org/revue/gpq/2003/v57/n1/010331ar.html?vue=figtab&origine=integral&imID=im17&formatimg=imPlGr

Coastal Geomorphology of High Latitudes

  

One of the illustrations from the paper, showing that in the inner reaches of Hudson Bay, which is where the central and thickest part of the Laurentide ice sheet was located, the land is still rising at about a metre per century.  The coastline there is a good place to invest in real estate, since your assets keep on expanding.....

 Multiple raised beaches on a shoreline on Hudson Bay -- a classic illustration of what happens when a shoreline is rising inexorably......

Further to my recent note about Researchgate and the publication of assorted old research papers of mine which have previously not been available in digital formats, this one might be of interest to geomorphology / high latitude buffs:

Coastal Geomorphology of High Latitudes
Brian John, David E Sugden
Progress in Geography 7 (1975), pp 53-132.   01/1975; 7:53-132.

https://www.researchgate.net/publication/262414487_Coastal_Geomorphology_of_High_Latitudes?ev=prf_pub

David and I were asked to do this for the PIG series, which published up-to-date summaries of geographical research findings with the intention of keeping the research / teaching community up to speed on developments.  As far as I know, although it is somewhat dated, this is still the most comprehensive review of the factors that affect coastal development on the high-latitude coasts (Arctic and Antarctic) of the world.

You can either read the article online, or download it -- but because it is a hefty piece of work (more than 80 pages), that might take some time.......

More rubbish about Stonehenge and glaciers

 Craig Rhosyfelin.  No peer review, no reports, and everything shrouded in secrecy.......

It's funny, isn't it, the way that total rubbish, if repeated often enough, becomes accepted as the truth, at least by those of us who have a gullible disposition?   I'm not suggesting that everything in Mike Pitts's latest article on Stonehenge (in Focus magazine, July 2014) is total rubbish, but some of it is, and you get my drift.....

The article purports to bring us up to date on the latest developments, and there is a strong emphasis on the geological work centred on Craig Rhosyfelin. But let's get two things straight here.  

(1)  The geologists have published several papers on Craig Rhosyfelin and the Stonehenge debitage in recent years, in peer-reviewed journals.  

(2)  As far as the archaeologists are concerned, they have worked for three field seasons at Rhosyfelin (2011, 2012, 2013) and there has not been a single peer-reviewed article relating to their findings, and as far as I know, not a single field report or any other description of the work done or the interim findings.  As we are reminded often enough on this blog, none of the radiocarbon dates from the site has been reported, and neither have any of the other technical findings.  So all we have is MPP's description of some of the Rhosyfelin "discoveries" in Ch 17 of his latest book, flagged up as being definitive evidence of quarrying activity and a link with Stonehenge, and presumably not peer-reviewed by anybody.  And then a number of popular articles in glossy magazines, lectures and talks, designed to cement the "quarry" hypothesis but not actually subjected to any critical scrutiny by anybody.........

I'm not saying that the "quarry hypothesis" is wrong.  I'm just saying that it has never been subjected to proper scientific scrutiny or peer review, or demonstrated to be anything other than a fantasy. 

People like Mike Pitts should know better than to simply trot out all this unsupported nonsense and pretend that it is all true.  He is perpetrating the myth, and he knows exactly what he is doing.  I don't want to go through the whole paper with a toothcomb, but I'll give you a flavour:

1.  Pitts says this:  "But what if the bluestones, key to this interpretation, were not brought to Salisbury Plain by people at all, but millennia before, by glaciers? It’s an old idea, dismissed by mainstream science but still championed by a few."  That is complacent, condescending nonsense.  There is no other way to describe it.  The glacial transport hypothesis has NOT been dismissed by "mainstream science" -- whatever that is.  A few geologists and geomorphologists  (for example Scourse, Green and Bowen) have expressed their doubts about the glacial hypothesis in print, and others (for example Williams-Thorpe, Kellaway, Jackson, and yours truly) have written in support of it.  The debate goes on.

2.  Pitts says this:  "........the team found a further precise source at Carn Goedog for Stonehenge’s famed ‘spotted dolerite’.  Significantly, these new sources are on slopes facing north, towards the Irish Sea. The discredited sources faced south, towards the Bristol Channel - which they would need to do if the stones had been carried towards Wiltshire by glaciers."  Oh dear -- fundamentally wrong.  Carngoedog is indeed the preferred source for some of the spotted dolerites at Stonehenge, but the geologists have never said that it is THE place where all the spotted dolerites have come from, and other sites are still in the frame.  And where on earth does the nonsense come from regarding the "discredited sources" facing south, where they would need to be located in order to be picked up by glaciers?  Our esteemed author has this totally screwed up, as he would know if he had bothered to read my article written with Lionel Jackson a few years ago, or if he had just searched this blog for the term "entrainment", or if he had read any geomorphology text book.  Just to put it on the record again:  the preferred locations for the deep glacial quarrying and entrainment of bedrock slabs, monoliths and other debris when the Preseli Hills were deeply inundated by ice would have been the NORTH SLOPES, and not the south-facing ones.  Plucking does take place on the down-glacier slopes of roches moutonnees of various sizes, and indeed we cannot discount the possibility that erratics from these southern slopes will be identified at Stonehenge -- but where a mountain barrier is transverse to glacier flow, that flow becomes compressive,  shearing happens, and the dynamics operating on the glacier bed change quite dramatically.  Thrust planes are one consequence.  It's a bit complicated, and it has everything to do with glaciological theory, but don't blame me for the laws of physics........

3.  Here we go again on the periglacial stripes.......... Quote:  "Such ‘periglacial stripes’, as
they are known, usually form a branching network.  What might account for the long, straight lines?
Again for reasons that are not yet clear, but probably due to the local geology, there are three
barely visible parallel ridges in the chalk at just this site. These, suggests Allen, would have channelled water to flow straight downhill, eroding the grooves. When people first returned to Britain after the Ice Age, the stripes would have been visible on the barely vegetated ground, and later remained so, as plants grew thicker and darker over the silt-filled grooves.  The significance of this, says Allen, is the “astonishing, coincidental” fact that the banks and stripes are aligned on the solstice axis....."    Nobody has ever provided any convincing evidence that they are periglacial or that they have anything to do with permafrost conditions.  Where we do see periglacial stripes in the cold regions, they do not form branching networks.  Just three stripes and ridges?  There are hundreds of them, all over the Stonehenge landscape.  But at least Mike Allen refers to the work of water -- so maybe he is coming round to the idea that they are solutional rills, as I have suggested over and again on this blog.  But as for the "uniqueness" of these features, I fear that I am not convinced.  And as for that word "astonishing" -- shall we say that I am less than astonished........

For those who are suckers for punishment, here is an extract:

Secrets of the stones
Archaeologists think they have
finally solved the mystery of
why Stonehenge is where it
is, reveals Mike Pitts

Focus, July 2014, pp 48-52
www.thetimetravellers.org.uk/StoneHenge2.pdf

Extract:

So Stonehenge is in the centre of Wessex because
that is where, over many generations, a local group
grew to be more powerful and ambitious than its
neighbours. But what if the bluestones, key to this
interpretation, were not brought to Salisbury Plain
by people at all, but millennia before, by glaciers?
It’s an old idea, dismissed by mainstream science but
still championed by a few. To prove this wasn’t the
case, someone needed to confirm not only that the
stones really did come from the Preselis, but
also that they had been moved by people. It was
a challenge that Richard Bevins, a geologist at
the National Museum of Wales, and Rob Ixer,
a petrographer at UCL, took up with gusto.
In the 1980s an Open University project had
sampled many of the standing stones, and
matched some to Preseli sources; the scientists
concluded that the bluestones reached
Wiltshire in glaciers.

Bevins and Ixer wanted more detail. Over the past
decade they have been analysing the different rock
types at Stonehenge, including pieces from new
excavations, and in Pembrokeshire. The outcome
was a surprise. “Almost everything we believed
about the bluestones has been shown to be partially
or completely incorrect,” said Ixer.

Aided by Bevins’s expertise in the local geology,
they have identified precise bluestone outcrops,
some just a few metres across. This encouraged
Parker Pearson to seek prehistoric quarries, and in
excavations at Craig Rhos-y-felin, a small rhyolite
outcrop, he believes he has found just that - complete
with an unfinished megalith. Working with Nick
Pearce, a geology professor at Aberystwyth University,
the team found a further precise source at Carn
Goedog for Stonehenge’s famed ‘spotted dolerite’.
Significantly, these new sources are on slopes
facing north, towards the Irish Sea. The discredited
sources faced south, towards the Bristol Channel
- which they would need to do if the stones had
been carried towards Wiltshire by glaciers. The new
geology also questioned two further recent claims
about bluestones, that they had been selected either
for their imagined healing powers, or their ability to
ring musically when struck with stone hammers.
The supposed healing springs, and the outcrops
that had been tested for ringing, are at places now
seen not to have supplied Stonehenge megaliths.
I f Parker Pearson’s confidence in his quarry, as yet
undated, proves correct, then his bluestone theory is
currently the most convincing. A “powerful polity”
in southwest Wales, he argues, already raising
impressive stone circles, forged links with another
in Wiltshire, through the strongest medium at their
disposal - they shared their ancestral monuments.

Mount Thor, Baffin Island

Mount Thor is a mountain peak that has been effectively chopped in half by glacial erosion.  It lies on the flank of the Akshayuk Pass, an extraordinary through valley that runs across the southern part of Baffin Island, coast to coast -- Cumberland Sound to Davis Strait.  It's 97 km long, and is reminiscent of the through troughs found in East Greenland.  Probably it was cut by ice flowing from the Laurentide Ice Sheet -- and its age is uncertain.  It might have been deepened more and more over a sequence of glacial episodes.  Certainly the trough, and the peak, have little to do with the local mountain glaciation which is much in evidence today.  The more modern glaciers and much smaller than that which cut the trough and cut Mount Thor in half -- one of these glaciers can be seen in a "hanging trough" in some of the photos above.  On the overhanging mountain face overlooking the pass, the free rock wall is over 1 km high.  The location is shown by the marker "A" on the satellite image below.

From Wikipedia:

Mount Thor, officially gazetted as Thor Peak, is a mountain with an elevation of 1,675 m (5,495 ft) located in Auyuittuq National Park, on Baffin Island, Nunavut, Canada. The mountain is located 46 km (29 mi) northeast of Pangnirtung and features the Earth's greatest vertical drop of 1,250 m (4,101 ft), with the cliff overhanging at an average angle of 15 degrees from vertical.[2] Despite its remoteness, this feature makes the mountain a popular rock climbing site.

The Trango Towers, Karakoram, Pakistan

These are truly extraordinary rock pinnacles in the Karakoram range, on a narrow mountain ridge flanked by glaciers.  The bedrock is apparently granite, but the real reason for the survival of the pinnacles must have something to do with intense vertical downcutting by glaciers over millions of years, combined with efficient evacuation of rock debris and maybe a minimal production of slabs and larger clasts by periglacial processes.  What is remarkable is the lack of screes -- and in most upland areas screes do of course mask many of the lower slopes of peaks like these.  Some types of granite just break down into sandy debris -- maybe that has something to do with it.  And this area is rather arid too.  An interesting geomorphological dilemma.......

From Wikipedia:

The Trango Towers are a group of tall granite spikes located on the north side of the Baltoro Glacier, in Baltistan, a region of the Gilgit-Baltistan territory in northern Pakistan. They are part of the Baltoro Muztagh, a sub-range of the Karakoram range. The Towers offer some of the largest cliffs and most challenging rock climbing in the world. The highest point in the group is the summit of Great Trango Tower at 6,286 m (20,608 ft). The east face of the Great Trango Tower features the world's greatest nearly vertical drop.

Structure of the group

All of the Trango Towers lie on a ridge, trending northwest-southeast, between the Trango Glacier on the west and the Dunge Glacier on the east. Great Trango itself is a large massif, with four identifiable summits: Main (6,286 m), South or Southwest (circa 6,250 m), East (6,231 m), and West (6,223 m). It is a complex combination of steep snow/ice gullies, steeper rock faces, and vertical to overhanging headwalls, topped by a snowy ridge system.

Just northwest of Great Trango is the Trango Tower (6,239 m), often called "Nameless Tower". This is a very large, pointed, rather symmetrical spire which juts 1000 m out of the ridgeline. North of Trango Tower is a smaller rock spire known as "Trango Monk." To the north of this feature, the ridge becomes less rocky and loses the large granite walls that distinguish the Trango Towers group and make them so attractive to climbers; however the summits do get higher. These summits are not usually considered part of the Trango Towers group, though they share the Trango name. Trango II (6,327 m) lies northwest of the Monk, and the highest summit on the ridge, Trango Ri (6,363 m), lies northwest of Trango II.

Just southeast of Great Trango (really a part of its southeast ridge) is the Trango Pulpit (6,050m), whose walls present similar climbing challenges to those of Great Trango itself. Further to the south is Trango Castle (5,753 m), the last large peak along the ridge before the Baltoro Glacier.