Central East Greenland's Old Red Sandstone Basin: 

a strike-slip dominated deposystem

Here's a field trip to the fjords of Central East Greenland, at 73 degrees north. The geology and the wildlife are fantastic, its one of the most beautiful and least visited places on Earth.  

Two minutes to download this page, I'm afraid, if you have a slow modem, but I hope the wait will be worthwhile.

Key literature to read on this area includes these three items:

John Haller, 1971. Geology of the East Greenland Caledonides. Wiley and Sons. This book is one of the finest regional geological studies ever published, it summarises the work of hundreds of people in Greenland and is magnificently illustrated with photos and maps. Essential, inspirational.

Haller, J., 1965. Tectonic Map of East Greenland. Medd. Gronland 171 (5).

Koch, L. and Haller, J., 1971. Geological Map of East Greenland, 72-76 N Lat. 1:250,000.  Medd. Gronland 183.

Looking at the geological maps of East Greenland, an association of features immediately signals strike-slip tectonics as a dominant post-Caledonian structural style. In this respect East Greenland resembles other North Atlantic Devonian basins. 

What’s characteristic about strike-slip faulting?

Hudson Land in the north displays the older ORS sequences, and the structural history of Old Red depocentres is quite beautifully shown there, see Haller's super air photos. The overall geometry indicates left-lateral movement. As the major faults swing to the NNE in the northern part of the basin they mostly become high-angle reverse faults, compressional given the left-lateral deformation sense of the basin, whilst northerly trends are strongly oblique dip-slip extensional. Sequences change very quickly from place to place, in thickness and sedimentary style: you can go from one mountain to another, across a narrow fjord, and find that correlating the successions in detail is impossible.   Especially in the deeper Devonian, there are few sequences which persist from place to place. Adding to the sedimentary variety, there are numerous local basalt and rhyolite volcanic centres.

If we drew a section west-east along Kejser Franz Josephs Fjord, for example, the Upper Old Red geometry would look something like the yellow unit. The east side of the Upper ORS outcrop is a huge strike-slip fault and to the west of it the sequence is changing thickness and facies abruptly across a series of blocks, some of which are reverse-fault bounded. The whole basin is flexed, an element of the geometry which this model doesn't show.

The Old Red major sedimentary units are these:

This field trip will take us from Mestersvig northwards to Ella Island, then some 50 km east along Sofia Sund to Celsius Bjerg. It’s a west to east transect of the southern part of the Old Red Sandstone basin, showing huge unconformities, vast sequences of fluvial and lacustrine sediments, and large-scale post-Devonian folding and thrusting. We shall also note a close link with Norwegian North Sea tectonics: the Jurassic-Cretaceous pull-apart of the Voring Basin was strongly expressed here.

This journey will give you a good idea of how the Old Red basin is built, and provide some analogs for working elsewhere.

Logistics

No one lives here. The fjords are frozen until June-July and by September it’s getting bitterly cold again. How do you even get here? 

Well, we fly in, and we bring all our food and fuel. By plane Iceland is only a few hours from the nearest hub airstrip suitable for our trip: Mestersvig. Back in the summers of 1968-70 when I worked in the Old Red Sandstone basin as a Cambridge student, we would fly from Reykjavik north to Mestersvig which was then an emergency strip, and a support centre for a local mine and for the Danish Army dog-sledge teams which patrolled the coast in Winter. Then we took a Royal Danish Air Force amphibious Catalina flying boat for the short hop north again to Ella Island, where we could land on open water and disperse to our field areas in Zodiac inflatables. The fuel and food for this operation was dumped the year before, by an ice-strengthened ship called Nella Dan which left the supplies for us at Ella. At the end of the field seasons, in early September, the main fjords were all clear of ice and we could motor down to Mestersvig without the need for the flying boat again.

A few of the thousands of Catalinas which were built in the 1940s are now in museums, although most of them didn't last long enough to be so honoured. After retirement by the RDAF in 1970, for example, L-686 went to work in the USA and crashed in 1984.  Here's one of those planes:

Now, it’s rather simpler. Greenland is an independent country interested in tourism, and since 1974 our chosen area is a magnificent National Park. Actually it’s the largest National Park on earth. To support a 2-week trip we might charter a Twin Otter from an operator like Air Iceland, for a couple of flights into the field via Mestersvig. From there, these planes have big soft tyres and can put down on a rough tundra strip or cleared beach of which there are quite a few on places like Traill Island, in our area of interest, and then we’ll boat around the fjords. A couple of Zodiacs will go into a Twin Otter broken into their packages along with outboards, plus our food, petrol and tents etc for the fortnight, and 3-4 people will go on the first trip to set things up: the second trip will carry the rest of our team. Check out the Internet, you’ll find lots of pictures of Twin Otters operating in Greenland.

Field Trip:  Mestersvig to Celsius Bjerg

So we got here, lets get the boats inflated, load some supplies, and head north. Oh, did I mention the mosquitoes? Let's hope for a cold spell in early August to finish them off, meantime slap on the cream. And no, this man didn't forget to put the base boards in, its just easier to insert them when there's some air giving shape to the Zodiac.

Here's where we are going:

On the way north from Mestersvig to Ella O, we can detour and see some fabulous geology in Lyells Land. 

Just down the Segelsalskapet Fjord is Berzelius Bjerg which has an amazingly colourful and laterally persistent sequence belonging to the PreCambrian Eleonore Bay Group. The mountain is about 1800 metres high. At the western end here, by the entrance to Polhemsdal, the main part of the cliff is the Quartzite Series. Using the terminology of the geologists who worked here in the 1950s, this comprises 500 or so metres of dark shaly bed 3; then unit 4 is the 400-metre yellow and then grey sequence of quartzites; bed 5 is the 250 metre dark red shale unit above; bed 6 is the 50 metre yellow to grey quarzite unit about half way up the face. Next comes the Multicoloured Series: 200 metres of red shales of bed 7 into which many faults detach; the yellow and grey dolomite beds 8, 9, each about 150 metres; bed 10 is at the top, a complex of red and yellow dolomitic shales. There is a huge contrast between the continuity of these marine transgressive beds and the locally highly-variable fluvial sequences of the Old Red Sandstone, these marine units can be followed all the way up the west side of the fjord region for hundreds of kilometres.

The big extensional faults of Berzelius Bjerg formed in a marginal flexure zone along the west side of the Old Red basin, in the crustal pull-apart process which made way for the younger granites to be injected. One such fracture, running down the east side of Alpefjord, has a throw of more than 2000 metres.  

Deep underneath the Eleonore Bay Group superstructure sediments are the granites of the Staunings Alper, which you can see in stupendous outcrops by the Sefstroms Gletscher in Alpefjord just to the south, and that’s the place to go to see intrusion tectonics in the crystalline core of the Caledonides. “Late Orogenic” granites make the peaks and form an outer, younger core to granite gneisses which flowed into place in gigantic batholiths. Its fun to motor along the front of the glacier, but not too close, watch for waves from pieces detaching.

As we travel north from Mestersvig the colossal cliffs of Kongeborgen on Traill Island are an impressive introduction to the Old Red Sandstone, showing a 2000-plus metres sequence of Middle-Upper Devonian, in remarkable contrast to the Eleonore Bay rocks on the opposite side of the fjord. This section doesn’t look highly disturbed but it is: its been thrust-translated westwards, much of it is resting on vast detachment surfaces near the base of the cliffs which are more or less bedding-parallel in this hangingwall section, the rocks have been pushed towards us. You wouldn’t suspect this until we turn the corner into Vega Sund or Sofia Sund and see the dip sections, in which repeat sequences on thrusts are evident. More on this shortly, but for the moment reflect on the scale of these outcrops and think about how you might begin to establish the stratigraphy here.

How could you measure sequences in vast cliffs like these? Air photography is clearly vital, we’re looking from the Catalina blister in this photo and the view is marvellous, especially as it could be partly opened (pilots like to know you are doing this). In similar vein the 1930s expeditions used Heinkel float planes with a huge camera rig bolted onto the rear fuselage, and later on the Norseman was used until the late 1950s, when helicopters took over the support work.  

On the south side of Ella O in Narhvalsund we see the west margin of the Old Red Sandstone basin, represented by a most remarkable unconformity. Here about 1000 metres of Middle Devonian conglomerate are piled against Cambro-Ordovician limestones. I prefer to think of this surface as a syn-sedimentary local basin boundary fault. 

It looks very much the same as the Devonian basin margin fault at Posten in Hudson Land. I think this depocentre is a local pullapart "trapdoor" basin bounded to the south by a huge fault beneath Narhvalsund, forming a sidewall to strike-slip transtensional faulting beneath Kong Oscar Fjord, like this:

The fragments of rock in these huge fans of conglomerate include not just local material but also Eleonore Bay Group dolomite, Multicoloured Series red shales, and eventually, at the top of the sequence, metamorphic rocks showing that the central crystalline Caledonian complex was finally unroofed by Devonian erosion. The footwall shows wadi incision, probably karst topography, into the limestones and the infill of these ravines was probably by debris flows.  

This photo shows more of the Old Red succession, its possible to make out some subtle convex-up bedding surfaces which are a response to extension on the curving floor fault which I infer as linking with the Kong Oscar shear zone. The geological map suggests that the main detachment steps down into the Ordovician. Overall the sediment just seems to have poured onto a high-relief topography.

We now head north into Sofia Sund.

Refering back to the geological map of the basin, you’ll see a family of fold axes trending more or less north south and locating closer together in Traill O. These broad, huge folds correspond to post-Devonian, pre-late Carboniferous regional compression in renewed transtensional basin development, a deformation called the Ymers O Phase. At the west edge of the basin the shortening is expressed in a series of spectacular thrusts, which we’ll see on Svedenborg and Rodebjerg.  This is Rodebjerg, on Sofia Sund, it looks like a thrusted fault-propagation fold:

And this is Svedenborg, on the south shore of Sofia Sund. Svedenborg has some important west-vergent thrusts, trending more or less north-south, detaching in the Old Red sequence.

Southeastern Celsius Bjerg shown below, is a lovely place, south-facing and sunny with big spreads of tundra covered by flowers, you'll see huge flocks of barnacle geese, small groups of musk oxen, maybe a polar bear if you are very lucky, and on the ridges you can walk up through the Kap Graah Group into the type sections of the Mt Celsius Supergroup and collect stunning fish fossils. In places there are so many fossils, you can just collect only the best Holoptychius and Remigolepis, and maybe you'll find skull bones of the ichthyostegids, early amphibians just below the grey unit at the skyline.  This is the Gronlandaspis Group, the youngest beds in the basin.

West of that photo, this is the central part of Mt Celsius:

And on the south side of Sofia Sund, opposite Celsius Bjerg, is Rudbecks Bjerg on Geographical Society O:

Looking due south across Sofia Sund from the summit of Celsius Bjerg, we see that  Rudbecks Bjerg is made of Kap Kolthoff Supergroup beds folded in the mid Carboniferous Ymers O phase, prior to deposition of late Carboniferous molasse sediments. The anticline axis is the same one as we are standing on in Celsius Bjerg. Note the steep-dipping Tertiary basalt intrusions, there are two obvious ones, the second is half way down the left skyline, and a third exists at the left edge of the picture. Just outside the picture is a major down to the east fault which marks the end of the Old Red outcrop.

This, I'm afraid, is the best I can do for a photo of Laplace Bjerg, 30 km to the southeast of us here, but it deserves inclusion as that mountain is quite remarkable. This shot is from the summit plateau of Celsius Bjerg.

In the early Cretaceous plate reconstruction, Central East Greenland lies only about 200 km northwest from the Voring Basin . It shared in the tectonic events which shaped the pull-apart of the North Sea Jurassic-Cretaceous basins. More than that, there are some exhumed giant oil fields here, and Laplace Bjerg is one of them. The details are given by Price and Whitham (1997) in the AAPG Bulletin.

Laplace Bjerg's top is Tertiary basalt   The upper part with patches of snow is Triassic west (rightward)-dipping sandstone with a Cretaceous sequence on its west side, and under thin Albian-Cenomanian mudstone caprock is a mid Jurassic sand impregnated with a column of solid bitumen.

Another major bitumen-impregnated Jurassic sand is seen near Mestersvig, on Traill O at Svinhufvudsbjerg. Are these analogs for the giant fields in Lower-Middle Jurassic reservoirs of the Brent province in the North Sea ?   Price and Whitham have shown that indeed they are, and have described four of the fault blocks of Geographical Society O and Traill O as former oil traps. Laplace Bjerg was a billion-barrel field.

Summary of tectonic events

To summarise, the sequence of main events seems to be like this:

-mid Devonian left-handed transtensional basins established

-various U Devonian extensional phases with local basins, local compression and unconformities, fast facies changes

-latest Devonian through mid Carboniferous extension (Ymers O Phase)

-late Carboniferous-Permian extension, erosion of Traill O

-early Triassic Jameson Land rifting, start of North Sea basins pull-apart

-mid Jurassic to early Cretaceous rifting, Volgian breakup of larger fault blocks, and rapid subsidence

with 2500-metre marine wedges, 1+ km of erosion from crests of blocks

-onlap in the thermal subsidence phase, Cretaceous, with late Cretaceous extension

-early Tertiary rifting 55 Ma, oceanic crust starts to form. And again as Jan Mayen separates, syenite at 35 Ma

- compression of Traill O, uplift, removal of 1.5 – 3 km cover in mid-late Tertiary

We have a second field trip here, which is a tour along the coasts of Gauss Halvo and Moskusoksefjord.

Meantime, I hope you enjoyed this one!

This article and photos are copyright to Highland Geology Limited.  We make no representation that the remote places described here are freely or safely accessible.