For another transect of the wonderful Old Red Sandstone basin this is a run along the majestic Kejser Franz Josephs Fjord, from the east edge of the Upper Old Red Sandstone basin to the west end of Gauss Halvo, where we turn into Moskusoksefjord and motor back southeastwards as far as the basin boundary fault at Hogboms Bjerg. 

About 30 km beyond the bow of the Zodiac, is Waltershausen Glacier which calves big bergs into the fjord. Some days there's a lot of pack ice, and then it magically disappears. This is loc 4 on the map.

When the ice is around its dead calm and the boat will run slow, so your feet will get cold. We can stop at Aina Dal and get some amphibian fossils, and probably our hair parted by low-flying long-tailed skuas, which don't like people walking near their chicks.

Locality 1, above, is loaded with geological significance, we are just off Agda Dal at Mt Gunnbjorn. The basin is controlled by syn-sedimentary strike-slip faults and is characterised by rapid changes in formation thickness, and local unconformities. This huge cliff shows the green fluvial sandstones of the Middle Devonian, tilted and eroded with the base Upper Devonian unconformity surface below the main ridge, overlain by pale brown sandstones of the Kap Graah Group. These are only a few hundred metres in thickness here but as we motor along the coast we are going to see them thicken very rapidly, with facies changes and the appearance of a number of formations. The thin red siltstone on top of them is the Aina Dal Formation, and above it is the dark grey Wimans Bjerg Formation which is also made of silts and mudstones, and just at the very top of the mountain ridge is the Britta Dal mudstone sequence. At the west shoulder of the mountain a large fault drops these Upper Devonian units towards us. This huge rock face is probably a fault scarp, and the shoulder fault may be a relay ramp.

Locality 2, this is Britta Dal separating Stensios Bjerg at right from Smith Woodwards Bjerg at left. The Aina Dal Formation red siltstones and overlying grey Wimans Bjerg Formation are brought near to sea level in the syncline, this is a great place for fossil fish and amphibians, but only in the red silstones. The grey sequence is a playa lake and loess deposit with no channel sands, hence fish bones and teeth are rare. In the upper cliff faces, where the red colour returns  (Britta Dal Formation) there are channel sandstones too, and this succession is world famous for amphibians. 

On the top of Mt Stensio we found some wonderful fossils, little skulls with orbits, in a large block of sandstone. Should we leave them, where the weather would destroy them, or try to bring them home? We set to work with our hammers, and managed to collect a fair amount of the bones. Back in Cambridge they went into a drawer for 20 years,  and then some palaeontologist found them and got very excited. They were new genera. 

Not wanting to retrace my route I came down Stensios Bjerg via Britta Dal, which as you can see is a deep ravine. Its not recommended. My field assistant and I kept going because we were following muskox tracks in the scree, and we figured if the agile muskox could make it, so could we. At the top of the falls we found its skeleton, it had fallen: and the last part of the walk we did very carefully, and not saying very much.

West of the syncline, the Kap Graah Group is seen again at locality 3, climbing westwards and its thickness has dramatically increased, and the sequence includes siltstones. We are only a few 10s of kms from Agda Dal, but the changes are remarkable.  Above the KGG we see the Remigolepis Group siltstones. These faces were difficult to climb, to measure the successions in detail, though they aren't as steep as they look in these photos. In the afternoons rocks start to fall in the gulleys, so the screes are very loose.

Locality 5. Motoring round Kap Kolthoff where the first photo in this set was taken, and down into sheltered Moskusoksefjord, here's another huge section: this is Hogboms Bjerg, and its astonishing. Its a transpressional inversion of Middle Devonian rocks over Upper Devonian.

In the left half of the photo you see the Upper Devonian Kap Kolthoff Supergroup, which comprises very thick monotonous grey fluvial sandstones with limited outcrop in the gulleys, and unconformably across them lies the Kap Graah Group, seen in a line of cliffs. The unconformity is spectacular, the Kap Graah sandstones infill a wadi landscape.  (The unconformity disappears westwards, in 10-15 km). Thrust over both these rock units on a huge reverse fault, climbing westwards, are the green Middle Devonian sandstones we saw at Mt Gunnbjorn. This is a strike-slip fault. Notice the pervasive vertical fracturing in the hanging wall. The dark grey rocks right of centre are dolerites, and the red rocks at right are microgranites.

Locality 6. On the opposite side of the fjord is Sederholms Bjerg, and what's happening here? Its another oblique section across the Hogboms Bjerg thrust. The Remigolepis Group makes the top of the ridge, you see the red Aina Dal siltstones and over them the Wimans Bjerg grey siltstones. Under the Aina Dal beds is a thin grey-brown Kap Graah Group sandstone, and then a local unconformity is clearly seen. These uppermost Kap Graah beds are lying across a much thicker Kap Graah Group sequence including a volcanic basalt feeder dyke unit (dark coloured), which is folded;  and the gulley at left is the reverse fault, the leftmost (northern) side of the hill is made of the Kap Kolthoff Supergroup. The fold is due to proximity of the thrust surface.

And that's it. Central East Greenland's Old Red basin is a beautifully exposed model for interpreters in the oil and gas business, working in strike-slip controlled rock systems .

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.