Reykjafjordur moraines

 

1975 field map of the Reykjafjordur moraines near the Kirkjubol hot springs.  I labelled the outer (northern) moraines O1 and the inner (southern) moraines O2 -- but things might be rather more complicated.......

In the valley of Reykjafjordur, on the eastern flank of Drangajokull in NW Iceland, there are two groups of recessional or readvance terminal moraines.  The older moraines (numbered in the O sequence) are Late Glacial or Neoglacial in age (several thousand years old) and the younger ones all date from the surges or readvances in the Little Ice Age -- within the past 300 years.

These satellite images are useful in seeing the relationships:

The satellite image showing the valley floor where the O1 and O2 moraines are in close proximity.  ......

Annotated image showing what appear to be two morainic loops in close proximity.  In 1975 we labelled these O1 (outer) and O2 (inner).  We also called them the first and second Kirkjubol stages.  The outer one might be the equivalent of the Jokulgardur moraine in Kaldalon, and the inner one might be the equivalent of the Kegsir moraine, which appears itself to be a double moraine in Kaldalon.  Further fieldwork and dating is required to sort out what has been going on here............

This satellite image shows the bend in the valley, with the prominent end moraine ridge projecting from the western valley side out towards the river.

The same image, annotated to show the M1 stage moraine (c 1850) and the associated dry outwash fan.

Kaldalon in its regional context

Vestfirdir -- almost an island, where the growth and retreat of glaciers show some connections with the East Greenland coastal zone and some with the Iceland mainland.  Here the Dranga and Glama plateaux have both supported ice caps that have come and gone, sometimes in sync with the ice masses elsewhere, and sometimes not.......

The Dranga and Glama ice caps, according to various authors.   At intervals following the collapse of the LGM ice cap over Vestfirdir, these two ice caps have coalesced into a single unit.

Landscape types in Vestfirdir.  At times the plateau supported a singe ice cap with two main centres of accumulation and radial ice flow.

I have already flagged up the connections between East Greenland and NW Iceland, but as research proceeds, the wider the scatter of dates there seems to be, for the key glacial events such as glacier extinctions, rejuvenations and surges.  Both Drangajokull and Glamujokull seem to have melted away completely during the Holocene.  Both seem to have been regenerated during the Little Ice Age, but subsequently Glamujokull has disappeared again while Drangajokull has survived.  The three outlet glaciers of Drangajokull -- namely Kaldalonsjokul, Reykjafjardarjokul and Leirufjardarjokul -- have all surged intermittently within the past 300 years, but not entirely in harmony.

These are the dates of the recent (Little Ice age) surges:

Reykjarfjarðarjökull 1846, ~1886, ~1910, 1934–1939, and 2002–2006
Leirufjarðarjökull ~ 1700?, 1846, 1898, 1938–1942, and 1996–2001
Kaldalónsjökull ~1740, 1780?, 1810?, 1820, 1860,1920, 1936–1940, and 1996–2001

These surges are controlled by regional climatic variations, the precise glaciological characteristics of the glacier catchment areas, and by volcanic events and ash clouds (layers of ash on glacier surfaces can have a significant effect in lowering albedo and increasing melting rates.

Ice edge positions following the LGM and preceding the Little Ice Age are difficult to establish with certainty.  The assumption that the big moraines in the Reykjafordur and Kaldalon valleys are of Younger Dryas age are looking a little shaky -- and in now seems (from recent work) that they may have been formed a little later, in the Pre-Boreal period, around 10,300 - 9,000 yrs BP.  They are related to the moraines of the Budi stage in South Iceland, but are not exactly synchronised.

When the outermost moraine in Reykjafjordur was formed, relative sea level seems to have been around 32m asl.  The moraine has a planed top, and there are exposures of washed rock surfaces and washed till in the vicinity.  Was this the equivalent of the Alftanes stage (Older Dryas) in south Iceland?  Quite possibly.  And does the Seleyri moraine in Kaldalon date from the same stage?  That seems logical to me..........

This map of glacier stages in Reykjafjordur is based on fieldwork by the DUVP team in 1975.  Reference -- John 1975.   It shows three major ice front positions in the lower part of the valley.  The more recent research by Brynjolfsson and others concentrates on the moraines in the upper valley which are related to the Little Ice Age.

In this glacial chronology for Reykjafjordur two groups of moraines are identified.  Moraines M1-M4 date from the Little Ice Age.  Moraines O0 - O4 are older, dating from the Late Glacial and Neoglacial glacial episodes.  Ref:  John, 1975

European Glacial Landscapes
The Holocene
2024, Pages 193-224
Chapter 12 - Holocene glacial history and landforms of Iceland
Ívar Örn Benediktsson, Skafti Brynjólfsson, Lovísa Ásbjörnsdóttir, Wesley R. Farnsworth 

https://www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B978032399712600012X?via%3Dihub



Extract from Abstract

Climate amelioration in the Early Holocene was punctuated by the preboreal readvance of the Iceland Ice Sheet (IIS) between c. 11.3 and 10.4 cal ka BP, as manifested by raised shorelines and ice-marginal landforms below and inside Younger Dryas shorelines and moraines, respectively. By about 9 ka BP, most glaciers had become smaller than present and crustal rebound was completed. The Early Holocene retreat of the IIS is widely marked by end moraines in the highlands. Declining temperatures after the Holocene Thermal Maximum (HTM c. 8.5–6.5 cal ka BP in Iceland), during which glaciers were largely absent, resulted in the onset of the neoglaciation and the reformation of ice caps at 5.5–4.4 cal ka BP, with many outlet glaciers reaching their maximum Neoglacial extent at different times until as late as 1.1 cal ka BP. The Little Ice Age maximum glacier extent occurred either in the 1700s or the late 1800s. Since then, Icelandic glaciers have been retreating apart from observed still-stands or readvances from the 1960s–70s until the mid-1990s.

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In 1983 Eggert Larusson, who was a team member of our Durham University Vestfirdir Project in 1973-77, tried to unravel the sequence of glacial events in his 1983 doctorate thesis. He also tried to relate these stages to marine limits and lower terraces and other shorelines. He referred to "Latragrunn stage" when Vestfirdir was completely covered by its own independent ice cap --- during the LGM. Then there was a "Tjaldanes stage" when relative sea-level was around 11-22m asl -- and this must be the equivalent of of the "Jokulgardir stage" in Kaldalon and the Kirkjubol stage in Reykjafjordur. http://etheses.dur.ac.uk/7787/

Larusson, Eggert (1983) Aspects of the glacial geomorphology of the Vestfirdir Peninsula of northwest Iceland with particular reference to the Vestur-Isafjardarsysla area.
Doctoral thesis, Durham University.

Abstract
The evolution of the landscape of Vestfirdir, made almost entirely of volcanic rocks, is traced from the lilocene, when the oldest rocks formed, through the Pliocene and Pleistocene. Volcanic activity ceased first in the north western part leaving a basalt plateau with occasional large volcanoes protruding. Fluvial erosion, guided by a westerly dip of the plateau and tectonic lineaments, left a well developed drainage pattern there by the rime volcanic activity ceased in the southeast. The snowline fluctuated widely during the Plio-Pleistocene. Cirque and valley glaciations were very effective in sculpturing the landscape where the preglacial relief was greatest, in the northwest. Ice sheet glaciations affected the whole peninsula and offshore areas with linear erosion dominant in the northwest and areal scouring elsewhere. The glacial geomorphology of Dyrafjordur and northern Arnarfjordur is mapped. The highest marine limit is in the Nupur area, about 110 m, and shorelines and marine limits higher than 70 m are at 7 other localities at least. At least' two stages of glacial readvances are recognized: The Tjaldanes stage occurred when sea level was between 11 and 22 m and is probably of "Younger Dryas" age; later a readvance occurred in the cirques in the area. On the basis of evidence on cirque distribution, cirque elevation, zeolite zonation, distribution of glacial erosional landscapes, glacial history, marine limits, ice cap profiles and shelf moraine a model of maximum glaciations of Vestfirdir is proposed: The whole of Vestfirdir and the surrounding shelf areas was completely ice covered with no ice free areas. Such a stage of glaciation, the Latragrunn stage, probably prevailed in the Vestfirdir area during the last glaciation.


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See also:


https://www.researchgate.net/publication/377874262_Moraine_stages_in_the_Reykjarfjordur_outlet_glacier_trough

The big moraines of East Greenland and Vestfirdir

Winter satellite image of the Holger Danskes Briller terminal moraine in Kjove Land, East Greenland. This is referred to as a delta moraine, because it is associated on its outer edge with a fluvioglacial terrace at 101m asl.  The lake inside the moraine is to the left of the ridge.

The largest terminal moraine in Vestfirdir, NW Iceland -- in the glacial trough of Kaldalon.  Summer satellite image.  The up-glacier side is to the right.  Sandur and tidal flats to the left, with gravel track and landing strip.  

It is tempting to correlate the big terminal moraine that blocks the eastern end of the Holger Danskes Briller trough in Kjove Land (East Greenland) with the big terminal moraine in Kaldalon which is labelled as Jokulgardur.  They are both significant landscape features, and both represent the stillstands of significant glaciers within glacial outlet troughs.  Well, East Greenland is not so far away from NW Iceland, and the two regions must have experienced broadly similar climatic shifts following the LGM glacial episode.  There are differences, of course; the glaciers associated with Drangajokull are much smaller than those associated with the ice cap in East Greenland, and so might be expected to react more quickly to climatic oscillations.  The histories of relative sea level are very different on both sides of the Denmark Strait.  But there was surging glacier behaviour in East Greenland just as there was in Vestfirdir..........

The Milne Land stage in Greenland is the approximate geological time equivalent of the Búði stage in Iceland. Both represent significant glacial events that occurred during the Late-Glacial period, specifically correlated with the Younger Dryas climatic "event" or possibly a few centuries later.

Milne Land stage (Greenland): This stage refers to a period of significant glacier advance or stillstand in East Greenland, marked by prominent moraine systems. It is primarily dated to the Younger Dryas chronozone, approximately 12,800 to 11,500 years ago (or slightly before this time, in the Pre-Boreal).

Búði stage (Iceland): This stage also represents a major readvance of the ice sheet in Iceland. It is generally correlated with the Younger Dryas cold period, occurring around 11,000 to 10,000 years BP, although some authors now suggest it formed later, during the Pre-Boreal period.

Both stages reflect regional climatic shifts near the end of the last ice age, making them correlative in geological time within the North Atlantic region.

Kaldalon -- the 1820 surge?

 

Traces of the 1820 (?) morainic loop on the floor of the Kaldalon Valley.  These are in the form of low elongated ridges and hummocks, quite subtle but nonetheless noticeable when one walks along on the valley floor towards the glacier.  The kame terrace remnants on the valley side above must be unrelated.  They may be related to the 1780 surge for which no terminal moraine is known (it may have been buried beneath the accumulating sandur).

The photo below (taken from high on the valley side) shows the degraded terminal morainic ridge with a couple of small "inliers" in the sandur, surrounded by gravel and water, further out.

The Trimbilsstadir double moraine

The Kaldalon "valley side esker" (now interpreted as a moraine) seen from the north.  The steep ice contact face is prominent, facing up-valley.  The older, subdued moraine is seen to the right, in contact with the outer slope..  

Satellite image of the Trimbilsstadur moraine / kame complex.  the outer (older) ridge is subdued and well vegetated.  The inner, very prominent, ridge is not grassed over to the same extent, and has a steep up-valley face interpreted as an ice contact slope.  The associated linear kame terraces (or lateral moraines!) are seen right of centre.

Lateral morainic ridge connected to the inner Trimbilsstadir end moraine, which runs steeply downslope.  We see the ice contact face. (View down-valley, with the Younger Dryas terminal moraine in the middle distance.)

This troublesome and confusing landform has been the subject of much debate in the literature, and I think that our 1962 designation of the large curved ridge (on the inside or eastern flank of the subdued green moraine)  as a "valley side esker" was somewhat naive and premature.  Others who have examined the feature more recently seem to be convinced that it is made primarily of till, not fluvioglacial sands and gravels, and that is important information.

David Sugden and I always were a bit worried about an apparent "esker" being formed this high on a valley slope -- especially since eskers always form in tunnels with ice above and on either side of them.  The eskers on the floor of the valley do seem to have been formed in sinuous tunnels beneath a wasting glacier, and they are linked into assorted hummocky dead-ice features and also to an abandoned outwash fan.  But here on the hillside it is difficult to conceive of "containing"  ice on the down-valley flank.  Neither do the conditions exist for classic kame terrace formation, in contrast to other situations further up the valley........

So I now revise my opinion, and think that this feature is a remnant of a terminal moraine with a very sharply defined up-valley ice contact face.  The feature is also much fresher than the subdued well vegetated moraine on its outer edge -- so it has to be younger.

I think we can also say something about the nature of the glacier advance associated with the ridge.  Because there is a substantial "void" on the up-glacier flank, this suggests to me a very rapid and dramatic ice advance involving relatively clean ice.  (If the advance had been more gradual and prolonged, the ice would have been heavily laden with supraglacial and englacial debris, and this load, when dumped, would have left a dramatic expression in the landscape.)

So going with the theory that this moraine was formed around 1740, what do we know about this advance?  Now we would call it a surge.   The old records refer to a great readvance between 1700 and 1756, in which the glacier covered once green meadows and destroyed the farm of Trimbilsstadir.  The ice front moved forward by at least 2 km.  There are also records of a great "glacier burst" or jokulhlaup in Kaldalon in 1741.  This suggests massive quantities of meltwater associated with a catastrophic ice wastage event.

I think we have no option but to argue that there were TWO surge advances here, ending up in virtually the same place.  Coincidence?  Or was there cause and effect?   Of course, it is quite possible that the older moraine was once more extensive, and that it did act as something oif a barrier to the advance that occurred around 1740.

Ages?  From the evidence presented by other workers, it is most likely that the old green moraine is of Neoglacial age, maybe dating to 3500 - 2500 yrs BP, and that the newer moraine segment dates from the Little Ice Age surge that occurred around 1740.

The "matching feature" on the north side of the valley, which I have referred to as the Kegsir Moraine, is even more copmplex, with incorporated distorted peats and other layers demonstrating a bulldozing effect during one or both of the advance phases.

How "Kaldalon Kame Terraces" are formed

The "Kaldalon kame terraces" at the base of the Votubjorg cliff, on the south side of the glacial trough.  In places there are clear trenches or gullies behind them, cut against bedrock exposures. 

They are very prominent features.........

The landforms which are most difficult to explain in the Kaldalon Valley in NW Iceland are the elongated features on the valley sides that are referred to variously by assorted researchers as "lateral moraines" or as "kame terraces".  Some refer ro them as being made predominantly of fluvioglacial sands and gravels, while others say they are made predominantly of till or moraine, and others say that they are essentially made of scree or rockfall debris.  Actually we are all right, because the characteristics of these ridges vary, depending on where you happen to look or where you dig your hole in the ground.

I have been examining some of the archive photos from 1960 and 1974, and from the work we did around the glacier snout one can see what the key processes and development stages are.

Stage 1.  On this satellite image you can see that the meltwater river is tight up against the western rock wall of the trough.  Here, because of enhanced ablation or melting, the glacier cross profile is convex.  This means there is a trough or gully along the glacier edge, into which surface meltwater is channelled.  This meltwater comes from surface streams on the bedrock on the glacier flanks or from surface glacier streams from higher up the glacier.

Stage 2.  As melting proceeds, the surface meltwater streams disappearinto the glacier, and most high-volume flow occurs sub-glacially, in tunnels beneath the ice but still against the rock wall.   View towards the rock wall, showing cascades of meltwater flowing down towards  and then into the glacier.

One of the subglacial drainage routes, now abandoned.

Stage 3.  The ice marginal gully is still visible, but it is dry because all meltwater has now been diverted beneath the ice.  Surface morainic debris (including till and faceted, abraded and striated boulders) begins to accumulate in the abandoned stream gully.  There are additional inputs from rockfall debris and scree cones derived from the high overlooking basalt cliffs.

Simultaneously, fluvioglacial materials accumulate in the main stream discharge routes, within and along the edge of the glacier.

Stage 4.  Deglaciation and glacier retreat leaves high marginal terraces on the valley side composed of fluvioglacial materials below and capped withy a mixture of till and rockfall debris.  This association is NOT the resuklt of ice front oscillations, but simply a consequence of the meltout process. The ridge is broken into segments, but overall the gradient is down towards a past snout position on the valley floor.

PS. Eskers are often capped with morainic debris in open landscape situations, and with rockfall debris in constrained valley situations.  Here we have both.

PPS.  Interesting question  -- why do these features develop in the glacier on the valley side rather than on the valley floor?  One might think that the main meltwater conduits would form right at the base of the glacier.  I suspect that this has something to do with modest meltwater flows and the tendency for very deep conduits to close under ice pressure during the 8 months or so of freezing conditions.  Shallow englacial conduits against the valley rockwall have a much greater chance of staying open, where there are crevasses and water discharge supplements from spring and autumn meltwater streams flowing down the valley side.

Kaldalon -- the big moraine and the Armuli raised marine terrace

 

The Jokulgardur terminal moraine, generally thought to be of Younger Dryas age, c 11,000 yrs BP.  It is by far the most prominent feature on the floor of the Kaldalon Valley. Marine sediments are exposed on its outer (western) edge.

In the latter part of this long article, Bout et al (1955) discuss the relationship between changing ice volumes and the raised marine terraces of Isafjardardjup.  But they do not seem to make a direct link between the big moraine in Kaldalon and the prominent marine tarrace north of Armuli, at the mouth of the Kaldalon trough.  That terrace, referred to as the 15 - 30m terrace by Bout et al, is the same terrace as that described by my colleagues and myself in 1975 as the 14 - 24m terrace. We need to be flexible in our labelling, because there are substantial variations in the altitude of the terrace top, and its edges are in places difficult to define.........

I am now rather convinced that this terrace represents a marine transgression or stillstand that coincided with the Younger Dryas ice expansion in Vestfirdir.  The is referred to as the "Younger Dryas glacial event" -- which may actually have been two events, incorporating the so-called Budi Moraine in south Iceland and other near-contemporaneous features.  Although global sea level was at c -60m at this time, there was also a contemporaneous very great isostatic load on NW Iceland, associated with a detached Vestfirdir ice cap which incorporated both Glamajokull and Drangajokull.  .  Isostatic uplift might have been slowed for maybe a thousand years, with the rate of uplift then approximately equivalent to the rate of eustatic sea-level rise.

Post-glacial (Holocene) sea-level curve, showing the stillstand or "step" near -60m around 11,000 - 12,000 years ago.  This was associated with the Younger Dryas "glacial event".

As David Sugden and I pointed out in 1962, there are marine sediments (including varved clays and bedded sands and silts) on the outer edge of the big terminal moraine called Jokulgardur or Holar.  These features have been missed or ignored by some other workers.  The sandur level adjacent to the western edge of the terminal moraine varies between 12m and 9m asl. The moraine top varies in altitude between 12m and 27m.  The surface is composed of unwashed till with a scatter of striated erratic boulders.  As far as we are aware, there are no marine terraces (with or without marine mollusca) on the inside of the moraine, even though the dry sandur level is at c 13m.  Therefore it is entirely logical to propose that at the time of the formation of the Armuli terrace glacier ice was blocking the valley as far west as the position of the moraine.  This in turn points to a grounded or floating ice edge.

https://www.researchgate.net/publication/262414815_The_Morphology_of_Kaldalon_a_Recently_Deglaciated_Valley_in_Iceland

The big terminal moraine in profile, seen from the southern gap.  Marine sediments are exposed in places on the steep west-facing slope.

Map of the moraine and features immediately up-valley.  From the DUVP 1974 Field Report.

Sketch map from Bout et al (1955) showing some features in Kaldalon and Skjaldfannardalur to the south.  In the latter valley there are abundant dead ice features linked to a delta near the valley entrance.  In 1976 we found traces of a high sea-level at c 30m on the SE flank of Steindorsfell.  We also estimated that at the time of rapid valley glacier ice wastage, relative sea level here was at 17.6m.  

Géomorphologie et Glaciologie en Islande centrale
 Pierre Bout, Jean Corbel, Max Derruau,  L. Garavel,  Charles-Pierre Péguy:
Norois  1955, vol  8,  pp. 461-574

https://www.persee.fr/doc/noroi_0029-182x_1955_num_8_1_1102

In Kaldalon the outermost moraine on the south shore is near the Kalda stream cutting, just to the west of the Seleyri spit (John and Sugden, 1962). Here there is a distinctive vegetation-free mound of till and striated boulders.  Moraine teraces extend for at least 500m along the valley side.  We speculated in 1962 that this might be a remnant of a terminal moraine, laid down on a grounded ice front at a time of relatively high sea level.  Could this be related to the 30m beach traces on Steindorsfell?

It's interesting that according to Hansom and Briggs (1991) the highest shoreline traces on Hornstrandir, 30 km to the north, are around 26m asl (Hjort et al, 1985).  We defined the upper marine limit as 30m in Skaldfannardalur -- and this is the same altitude recognised by Principato and Geirsdottir in 2002 and based on their own evidence.

Principato (2008) does not recognize the presence of the raised marine terrace at 24m - 14m  near Armuli, referring only to fragments of the very low terrace (which is referred to elsewhere as the "Nucella" terrace) and the marine limit near 30m.  I agree that neither of these can be "tied in" to the prominent moraines in Kaldalon.  But as mentioned above, I am convinced that the massive Jokulgardur moraine was formed at the same time as the 24-14m terrace.  A short-lived marine stillstand and a contemporaneous grounded ice front in Kaldalon -- that makes sense.  The delta moraine on the flank of Steindorsfell was formed at the same time, when the valleys of Skjaldfallardalur and Hraundalur were filled with ice.

My field map showing the main depositional features of the Armuli - Melgraseyri area.

The 24-14m terrace neat Melgraseyri, with the entrance to the Kaldalon trough beyond.  The "Nucella terrace" remnants are seen just above the present shoreline.