ABSTRACT The Nordaustlandet terrane of Svalbard plays a critical role in evaluating strike-slip displacements in the Caledonian orogen. Comparison of Silurian and Tonian magmatism in Nordaustlandet, East Greenland, and the Pearya terrane on Ellesmere Island provides a means to evaluate models of large-scale versus minimal displacements. Augen gneiss with an emplacement age of 972 ± 5 Ma demonstrates that the Tonian granite suite is coeval with the calc-alkaline Kap Hansteen volcanic rocks. Zircon from Silurian leucosomes, leucogranites, and granites is dominated by xenocrystic components, making it analytically difficult to isolate magmatic versus inherited age domains. Zircon systematics from a relatively undeformed Silurian granite (431 ± 5 Ma) resemble those of similar granites interpreted to be Tonian in age (e.g., Kontaktberget granite). Assuming less deformed granites of Nordaustlandet are Silurian, synemplacement or syntectonic deformation of Tonian augen gneiss and volcanic rocks is no longer required. Tonian magmatic rocks of Svalbard share a common origin with basement rocks of the Pearya terrane within a continental arc system, but are distinctly older than Tonian igneous and metamorphic rocks of East Greenland. Migmatite complexes and granite intrusions in Nordaustlandet, with ages ranging from 440 to 425 Ma, are coeval with granites in East Greenland that record the combined effects of subduction beneath Laurentia and mid-crustal melting. Migmatites in East Greenland are juxtaposed with low grade rocks by syn-contraction normal faults whereas migmatites show gradational contacts into lower grade rocks on Nordaustlandet. These differences in basement age and structural setting preclude proximity of the Nordaustlandet terrane with East Greenland during the 440–400 Ma continent-continent collision phase (Scandian) of the Caledonian orogen. Similarly, differences in depositional, magmatic, and metamorphic history between the Pearya terrane basement and Nordaustlandet terrane argue against simple offset of crustal fragments. The Pearya and Nordaustlandet terranes likely were not involved in the main phase of crustal thickening directly related to collision of Baltica and Laurentia, but rather resided on a convergent boundary north of the Scandian continent-continent collision zone, consistent with models of Gee and Teben’kov (2004) and Johansson et al. (2005).

Abstract This paper considers the lithospheric structure and evolution of the wider Barents–Kara Sea region based on the compilation and integration of geophysical and geological data. Regional transects are constructed at both crustal and lithospheric scales based on the available data and a regional three-dimensional model. The transects, which extend onshore and into the deep oceanic basins, are used to link deep and shallow structures and processes, as well as to link offshore and onshore areas. The study area has been affected by numerous orogenic events in the Precambrian–Cambrian (Timanian), Silurian–Devonian (Caledonian), latest Devonian–earliest Carboniferous (Ellesmerian–svalbardian), Carboniferous–Permian (Uralian), Late Triassic (Taimyr, Pai Khoi and Novaya Zemlya) and Palaeogene (Spitsbergen–Eurekan). It has also been affected by at least three episodes of regional-scale magmatism, the so-called large igneous provinces: the Siberian Traps (Permian–Triassic transition), the High Arctic Large Igneous Province (Early Cretaceous) and the North Atlantic (Paleocene–Eocene transition). Additional magmatic events occurred in parts of the study area in Devonian and Late Cretaceous times. Within this geological framework, we integrate basin development with regional tectonic events and summarize the stages in basin evolution. We further discuss the timing, causes and implications of basin evolution. Fault activity is related to regional stress regimes and the reactivation of pre-existing basement structures. Regional uplift/subsidence events are discussed in a source-to-sink context and are related to their regional tectonic and palaeogeographical settings.

Abstract The margins of the North Atlantic rift are covered by an extensive succession of volcanic rocks, with up to 5 km of continental flood basalts, hyaloclastites and interbedded sedimentary rocks. The volcanic succession deteriorates seismic imaging and has hampered petroleum exploration in these areas. Focused research and pioneering exploration activity, however, has improved the understanding and development of new play models in volcanic-influenced basins. In 2004, the Rosebank discovery finally proved that intra-volcanic siliciclastic sandstones of the Flett Formation may form attractive hydrocarbon reservoirs in the Faroe–Shetland Basin. The Kangerlussuaq Basin in southern East Greenland offers a unique opportunity to study the interaction of siliciclastic sediments with lavas and various volcaniclastic units. It is demonstrated that: (1) laterally extensive siliciclastic sedimentary units are present in the lower part of the volcanic succession; (2) the morphology of the lavas controlled variations in sandstone geometry and thickness; and (3) deposition of the interbedded sediments and lavas occurred in a low-relief environment close to sea level. The mineralogical composition of the intra-volcanic sediments is highly variable, ranging from siliciclastic to purely volcaniclastic. Diagenetic studies suggest that the nature of the volcanic component in volcaniclastic sandstones is more important to reservoir properties than the relative concentration.

Abstract During Late Paleocene–Early Eocene times, the modern Rosebank structure was located at the juxtaposition of the easterly advancing Flett volcanic system and the northerly prograding Flett delta. As a result, the Rosebank reservoir sandstones are interstratified with volcanic and volcaniclastic rocks, offering challenges for reservoir imaging, depth prediction and reservoir characterization. These challenges have driven the application of Ocean Bottom Node (OBN) seismic technology. OBN data have yielded improved velocity models for depth conversion, better reservoir definition and key insights to aid the modelling of sand distribution from seismic attributes. Spectral decomposition of the OBN seismic data has facilitated the extraction of distinct volcanic subunits, whilst spectral enhancement has enabled visualization of complex stacking patterns within individual igneous layers. To complement the seismic analysis, detailed geological analogue studies have been undertaken in volcanic provinces such as the Palaeogene volcanic district of SE Greenland and the Columbia River Flood Basalt Province, USA. No single outcrop provides a definitive analogy to Rosebank, but each offers insights that provide an important link to understanding and managing the main subsurface uncertainties associated with field development. Integration of these multiple workflows have improved the reservoir characterization and provided the foundation for the optimization of the field development plan.