The volume of glacial sediment observed offshore is much more than what can be accounted for by fjord erosion. This indicates that erosion must also have occurred in the areas above the fjords, on top of the flat surfaces.
Professor Ritske Huismans
A paper which appeared in Nature Geoscience
last week has presented evidence to contradict generally accepted theories about the geodynamics of the Scandinavian region.
Scientists from the Department of Earth Sciences at the University of Bergen
(UiB) worked alongside colleagues from ETH Zurich
to examine the onshore and offshore geology of the area and form a new model of its topographical history. It was the combination of the two disciplines, usually considered separately, which allowed them to settle the hundred-year debate on exactly how repeated ice sheets over the last 2.8 million years affected the Norwegian landscape.
Professor Ritske Huismans, head of the project and co-author of the paper, and first author Dr Philippe Steer, a postdoctoral fellow at UiB spoke to ScienceOmega.com
to shed more light on this hot scientific topic and discuss the findings of their research. Dr Steer began by describing the data which formed the basis of the study.
"The most important dataset used in our study is probably the topography of the Scandinavian landscapes," he said. "Indeed, it is now well-recognized that Earth’s modern topography results from the combined effect of past tectonic, climatic, and land-surface events. Therefore, detailed investigation of landscapes can help to unravel the secrets of geologic history.
"In the case of the Scandinavian landscapes, repeated glaciations during the last 2.8 million years have left very clear erosional imprints on the topography – in the form of the very deep Norwegian fjords – and some more controversial imprints, such as the elevated flattish surfaces found between and close to the fjords."
The main motivation behind the research project was to better understand the origin of these imprints. A second complementary dataset was also used, consisting of records of the sediment deposited off the shores of Norway during these glaciations.
It was fundamental to assessing the history of the Scandinavian landscape that this sediment record be understood, because onshore erosion ultimately results in offshore sedimentary deposits.
"The amount of offshore sediment resulting from glaciations during the last 2.8 million years has been compared to the maximum amount of erosion that has occurred in the fjord areas for the whole of western Scandinavia," Professor Huismans explained. "The volume of glacial sediment observed offshore is much more than what can be accounted for by fjord erosion. This indicates that erosion must also have occurred in the areas above the fjords, on top of the flat surfaces."
The study’s findings demonstrate that the high-elevation flat surfaces so characteristic of the Norwegian landscape are actually very young in geological terms, challenging previous assumptions about the geological history of the fjords and the elevated surfaces between and around them.
"This discovery contradicts previously accepted views for Scandinavian geodynamics, where high-elevation parts of the landscape were thought to be left almost untouched by the repeated ice sheets," Dr Steer remarked. "In these views, even the fjords were only partly eroded during the glaciations. With the erosion versus sediment budget, we clearly demonstrate that both the fjords and the elevated flattish surfaces are products of glacial erosion and are young morphological imprints."
Professor Huismans described the implications of these geological revelations for our understanding of the tectonic history of Scandinavia as a whole and, by extension, of the landscapes of other regions shaped by glacial activity.
"The Scandinavian elevated flattish surfaces were classically interpreted as being the results of an old, perhaps Mesozoic, planation event of topography down to sea level, followed by several uplift events that put these surfaces to their modern high elevation. However, this interpretation is mostly based on conceptual models, and no strong evidence exists to support it.
"On the other hand, the approach that we use is much simpler and only considers the now well-established abilities of glaciers and ice sheets to carve both flattish surfaces at high elevation and deep fjords at low elevations. Overall, our conclusion supports the idea that the mountain range in western Scandinavian as seen today is a remnant of the more than 400 million year old Caledonian mountain range and has been at high elevations ever since."
The results may also illuminate the tectonic and geological history of other high-latitude glacial landscapes, such as that of Greenland. Most of the data, especially in terms of drill cores and seismic profiles, were obtained by Statoil and other companies. Indeed, the study’s findings will have considerable implications for oil and gas exploration off the coast of Norway.