A new study published in Solid Earth, the European Geosciences Union’s Open Access journal

By Jean-Baptiste P. Koehl

Norway and Greenland collided ca. 400 Ma, forming a large mountain chain, which remains are observed all over Scandinavia and Svalbard. At the end of the collision, the mountain started collapsing on its own weight, initiating the formation of the so-called Devonian basins in western Norway and Svalbard. However, this phase of collapse is still debated in northern Norway, where no trace of the collapse (e.g., Devonian basins) were found. In the present study, researchers from the Research Centre for Arctic Petroleum Exploration (ARCEx) at UiT the Arctic University of Norway and the University of Oslo provide key evidence just off the coast of Norway, in the Barents Sea, suggesting that the collapse phase actually occurred there as well.

The study is based on the interpretation of offshore seismic data, which are basically equivalent to X-ray diagrams of the Earth. “We used these data to interpret rocks and faults, large cracks in the Earth’s crust bounding topographic depressions called basins. Our seismic interpretation focused on deep reflections possibly representing a major Caledonian shear zone, a thick zone of deformation that formed during the collision of Norway and Greenland, transporting rocks from Greenland over Norway”, said geologist Jean-Baptiste Koehl, lead author of the paper. Thin seismic reflection packages above the shear zone suggest a phase of extension in Devonian-Carboniferous times, thus, strongly suggesting that post-Caledonian collapse occurred in northern Norway as well, and that the thin reflection package represent preserved remnants of Devonian basins.

“The presence of Devonian basins in northern Norway has major implication for the age of hydrocarbon-bearing sedimentary basins, like the Hammerfest Basin in the South-West Barents Sea, which hosts the Snøhvit and Goliat fields” explains Koehl. “Notably, our discovery provides new perspectives on the nature of the rocks located at the bottom of these basins, at the edge of high-quality seismic imaging. Hence, we expect our study to contribute to create new hydrocarbon prospects in the Barents Sea”.

The results may also help to reconstruct the geodynamic history of our planet, for instance the past configuration of moving tectonic plates, and better predict future tectonic movements, i.e., earthquakes.

The study is fully accessible to anyone from anywhere around the world at the following link:

www.solid-earth.net/9/341/2018/

Geologist Jean-Baptiste Koehl studying Carboniferous sedimentary rocks in Odellfjellet, Spitsbergen.