Project aims

Our planet tells a story of mobile continents with a dynamic history, of continents still in motion today. The surface of the Earth is actually made of many rigid plates (seven large, 10⁸ km²; six intermediate, 10⁶-10⁷ km²; and more than 20 smaller plates, 10⁵-10⁶ km², known as microplates). These plates and microplates move away from, towards, over, and under each other, creating the mountains and oceans of our planet. The motion of these plates may cause fragments of one plate to be transferred to another. Fragments of rock which are not genetically related to the region in which they are found are known as exotic terranes.

Svalbard is geologically interesting because it contains several exotic terranes. Traditionally, these exotic terranes have been regarded as fragments of east Greenland which have been moved hundreds of kilometers north and assembled at their new location before about 400 million years ago (Andresen, 2001; Harland, 1969). Recently, however, it has been suggested (Gee & Tebenkov, in press) that these exotic terranes are little displaced from their original locations, coming from nearby north Greenland.

Our work attempts to unravel the long and complicated convergent and collisional history of the greater circum-Arctic region (see Pease, 2002; Gee & Pease, 1999; Gee, 1998) in an effort to understand the plate tectonic processes that have led to the development of our planet as we know it today. Within the wider context of circum-Arctic paleogeography, we are investigating the older exotic terranes of northwest Spitsbergen in order to determine where they have come from. This investigation constitutes the PhD. project of C.H. Pettersson at Stockholm University, under the supervision of V. Pease.

Field season 2003

Transported by the Norwegian vessel “Lance”, the Swedish team (V.P. and C.H.P.) arrived at our first base camp in Raudfjord, northwest Spitsbergen, on 1 July. Our international team consisted of Norwegian, French, and Russian colleagues. On 21 July our colleagues departed and the Swedish team relocated via helicopter to our second base camp west of Flathuken. We spent the remainder of our field season working from this location. We camped (in tents and sleeping bags) and collected data and samples by foot (typically requiring 10-15 km of hiking/day) or zodiac boat.

The expedition experienced generally fine weather and we achieved all of our scientific objectives. In addition, we experienced the abundance of Svalbard’s fauna and flora, including the polar bear and fox, Svalbard’s unique reindeer, walrus, seal, birds, and a beautiful Arctic wild-flower display! After 5 weeks in the field we returned to “civilization” by helicopter, to long-anticipated hot showers and a fine meal…

Preliminary results

Base camp 1

At base camp 1 (BC1 on figure 2) on the east side of Raudfjord, our sampling mainly focused on sediments overlying Precambrian (> 545 million years old) crystalline rocks. We assume that these sediments were derived from the crystalline rocks (basement) exposed and being eroded at the surface of the Earth at the time the sediments formed. Thus, by sampling these Silurian-Devonian (about 420-400 million years ago) sediments and determining the age of radiogenic minerals in them, we gain some insight into the age of basement exposed in the region about 400 million years ago. We also sampled the basement currently exposed in the region (Richarddalen and Montblanc complexes) in order to compare their ages and chemical compositions. Correlations between fossil-bearing sedimentary rock sequences are much easier to make than those associated with crystalline rocks. For the latter, as for our basement samples, we use age and chemical compositions to define “fingerprints” in order to make correlations. The “fingerprints” of our basement samples will be compared with those found in the overlying sediments, further constraining the source of the sediments.

Base camp 2

Base camp 2 (BC2 on figure 2) was located just west of Flathuken. West of Raudfjord, the basement is dominated by Precambrian rocks intruded by Silurian granites. The Precambrian units were the focus of our sampling programme. We were much more dependent on the vagaries of the wind and tides at this location because 1) the majority of our targets were on the coast and exposed to the Atlantic and Arctic Oceans, and 2) we were more dependent on the zodiac for mobility. In spite of this, we were able to establish three important regional traverses: one east-west across chaotic, partially melted rocks (migmatites), a north-south traverse in the migmatites along Raudfjord, as well as a north-south traverse in the older (>1.5 billion years old) deformed and metamorphosed complexes (gneisses) along Smeerenburgfjord.

We collected samples of the migmatite and gneiss complexes in order to determine their ages and high-temperature evolution, as well as their geochemistry. This information, in addition to evaluating the extent of their participation in Silurian-Devonian sediment genesis about 400 million years ago, also provides us with the necessary tools for correlating these rocks to those of Greenland. Consequently, we hope to be able to determine whether or not northwest Spitsbergen’s basement rocks are truly “exotic”, having been transported great distances along strike-slip faults from east Greenland, or whether they come from the relatively nearby northeast Greenland margin.