Project leader: David G. Gee, Department of Earth Sciences, Uppsala University 

The aim of the project

SWEDARCTIC work on the bedrock geology of the Svalbard archipelago primarily concerns the Precambrian and Caledonian tectonic evolution of eastern terranes and their relationships to other parts of the European and Greenland high Arctic. The early years of research concentrated on the Caledonian tectonics of Ny Friesland, with two Ph.D. programmes (Patrik Witt-Nilsson and Fredrik Hellman). With the fieldwork for these Ph.D. programmes completed, the focus of our work has moved eastwards to Nordaustlandet and the neighbouring areas of the Barents Shelf. Stefan Sandelin is working with tectonics and Alexander Larionov with isotope age and provenance studies (Figure 1). Having recently established that the Nordaustlandet Terrane is dominated by a Grenvillian age (c. 950 Ma) basement, unconformably overlain by Neoproterozoic successions, attention is now focused on defining the degree of Caledonian tectonothermal overprinting and its variation from west to east towards Kvitøya. Our work on Svalbard is incorporated in a wider context within EUROPROBE’s TIMPEBAR project (Gee and Ziegler 1996). The latter concerns the lithosphere of the Barents and Kara Seas and fringing terranes. Support for some of our Russian colleagues in the TIMPEBAR project is being provided by the INTAS funding agency in Brussels.

The fieldwork

In 1998, our field studies started in the central part of Nordaustlandet (July 21st), which was reached by helicopter (Bell 212A) from Longyearbyen. From a field base at Lake Svartauga Sandelin, Tebenkov and Andersson worked on three topics:

  1. To establish the stratigraphy of the Grenvillianmetamorphosed, deep water sediments in the Helvetesflya Fm.
  2. To study the contact between the Helvetesflya Fm and the c. 950 Ma granite that cuts these metasediments west and north of the camp.
  3. To find out if the basal part of Murchisonfjorden Supergroup, overlying the Helvetesflya Fm in central Nordaustlandet, is involved in the migmatization, south of Innvika, in the innermost part of Duvefjorden.

The mainly stratigraphical work on the sedimentary rocks was supplemented by collection of samples for research on provenance, using detrital zircons. The magmatic rocks were sampled for additional isotopeage analyses. On 3rd August, Lorenz flew by Bell 212A, together with a zodiac, from Longyearbyen to Westmanbukta on the northeastern coast of Storsteinhalvøya; thereafter the helicopter transferred Sandelin, Tebenkov and Andersson to the same location. This new camp presented excellent opportunities to study the basal part of Murchisonfjorden Supergroup from the Meyerbukta Fm through the Persberget, Westmanbukta and Kapp Lord formations. The zodiac made it possible to visit Lagøya and observe the type locality for the Meyerbukta Fm. It also proved possible to reach inner Lady Franklinfjorden and map the basal Kapp Hansteen unconformity on Gerardodden.

On 18th August, the field party withdrew by helicopter to Norsk Polarinstitutt’s ship Lance and joined the cultural sciences expedition for their studies of northern and eastern Nordaustlandet, Kvitøya and areas of eastern and southern Spitsbergen. During this trip, short stops were made at Sjuøyane and Foynøyane (north of Nordaustlandet), Isispynten (the easternmost part of Nordaustlandet) and Kvitøya (east of Nordaustlandet). These places consist of granites, augen gneisses and migmatites which were sampled for zircon age analysis. The 1998 field season was favoured by early snow melting and fair but sometimes cold weather, so little time was wasted due to the elements. We have collected a wide range of metasedimentary and magmatic rocks for laboratory analysis.

Results

In western Ny Friesland, recent work has shown that the thick Caledonian succession comprises a W-vergent antiformal stack, with thrust intercalation of Palaeoproterozoic basement (mainly granites and subordinate metasedimentary rocks) and younger (probably Mesoproterozoic) sedimentary successions. By contrast, Nordaustlandet is composed of a late Mesoproterozoic basement complex of metasedimentary rocks, variously intruded by c. 950 Ma granites and unconformably overlain by volcanic suites of similar age. The classical Neoproterozoic and Early Palaeozoic sedimentary successions (Murchisonfjorden and Hinlopenstretet Supergroups) unconformably overlie these ”basement” units. Separating the west Ny Friesland from the Nordaustlandet terranes is a thrust packet of flyschoid metasedimentary rocks (Planetfjella Group) of Neoproterozoic or Early Palaeozoic age).

The 1998 field season helped establish correlation of the Murchisonfjorden Supergroup strata of central Nordaustlandet with similar formations in the northwestern type areas. It also obtained evidence that the Murchisonfjorden Supergroup and underlying Grenvillian-age complex in central Nordaustlandet are influenced by Caledonian migmatization.