Marine Impacts and Environmental Consequences—Drilling of the Mjølnir Structure, the Barents Sea

In September 2007, thirty-three scientists attended an international workshop in Longyearbyen (Svalbard, Norway) to discuss impacts of extraterrestrial bodies into marine environment and to prepare for the drilling of the 142-Ma-old Mjølnir impact structure in the Barents Sea (Fig. 1; Gudlaugsson, 1993; Dypvik et al., 1996, Tsikalas et al., 1998). A field trip visited the ejecta layer in the Janusfjellet Mountain in Isfjorden, just outside Longyearbyen (Fig. 2). The workshop focused on two topics: 1) mechanisms of marine impact cratering including ejecta formation and distribution, geothermal reactions, and the formation of tsunami, and 2) environmental effects of marine impacts. Both topics are highly relevant to the Mjølnir event and the geological evolution of the Arctic, as well as to the biological changes at the Jurassic-Cretaceous boundary. Against thisbackground were a) concrete drilling targets formulated, b) plans outlined for compiling data from existing geological and geophysical surveys as the basis for Integrated Ocean Drilling Program (IODP) and International Continental Scientific Drilling Program (ICDP) drilling proposals, and c) a steering group and science teams established for compiling old and new material as a foundation for the developmentof drilling proposal

Shaking and splashing—A case study of far-field effects of the Mjølnir asteroid impact on depositional environments in the Barents Sea

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Bathonian and Callovian (Middle Jurassic) dinoflagellate cysts and acritarchs from Franz Josef Land, Arctic Soviet

Well preserved dinoflagellate cyst and acritarch assemblages are recorded from Upper Bathonian and Callovian deposits on Northbrook Island, Franz Josef Land. More than 45 species have been identified. Two new species are proposed: Parvocysta bjaerkei sp. nov., and Meiourogonyaulax spongiosa sp. nov. The recorded marine microfloras are compared with assemblages reported from contemporaneous strata in Svalbard

Palynostratigraphy, Palynofacies, T-R Cycles and Paleoenvironments in the Middle Jurassic–Early Cretaceous Ramså Basin, Andøya, Northern Norway

Palynostratigraphy and palynofacies analyses are applied to identify transgressive-regressive sequences and changes in paleoenvironment through the Middle Jurassic–Early Cretaceous succession of the Ramså Basin on Andøya. The conglomerate, the succeeding lacustrine-swamp deposits of the Hestberget and Kullgrøfta members (Ramså Formation) and the overlying terrestrial to marginal marine deposits of the lower Bonteigen Member (Ramså Formation), comprise the Bajocian T-R sequence. Bathonian–Oxfordian strata appear to be missing in the studied boreholes, and the second T-R cycle spans the Kimmeridgian to Berriasian open marine deposits of the upper Bonteigen Member and the Dragneset Formation (Breisanden, Taumhølet and Ratjønna members). The overlying Nybrua Formation comprises a condensed marine succession of Valanginian–Early Barremian calcareous sandstone and marl, followed by brownish-red siltstone. The upper T-R sequence (Skarstein Formation) consists of marine transgressive Barremian dark siltstones, silty shales and mudstones, followed by dark mudstone and shale. Marine palynomorphs recovered in these stacked marine slope turbidite sediments are of Late Barremian age, but possibly the youngest T-R cycle also includes Aptian deposits elsewhere in the basin

The Bajocian to Kimmeridgian (Middle to Upper Jurassic) ammonite succession at Sentralbanken High (core 7533/3-U-1), Barents Sea, and its stratigraphical and palaeobiogeographical significance

Ammonites recovered from Upper Bajocian to Upper Kimmeridgian strata in a core drilled at Sentralbanken High in the northern Barents Sea are described and chronostratigraphically interpreted. The lower part of the core comprises Upper Bajocian to Upper Callovian deposits of the Fuglen Formation with ammonites of the genus Cranocephalites near the base, and Longaeviceras in the upper part. The overlying Oxfordian to Kimmeridgian deposits of the Hekkingen Formation are thin and condensed. The Hekkingen Formation is dominated by Boreal cardioceratid ammonites (Cardioceras, Amoebites, Euprionoceras, Hoplocardioceras), with numerous Subboreal aulacostephanid ammonites (Rasenia, Zenostephanus) at two levels. The occurrences of Boreal and Subboreal ammonites are discussed in relation to the palaeogeography and fluctuations of ammonite faunas within the Boreal Realm during the Kimmeridgian with special attention to levels rich in Subboreal ammonites whose appearance has been controlled by tectonic and climatic factors. The uppermost part of the succession deposited during a time of maximum flooding in the Late Kimmeridgian is dominated by Boreal ammonites

Table1. Strontium isotope data from investigated wells

The Molo Formation represents a characteristic depositional unit on the inner Mid-Norwegian continental shelf and extends along the coast for about 500 km from Møre to Lofoten. It was deposited by coastal progradation in a wave-dominated environment with extensive long-shore drift. The age and stratigraphic relationships have been heavily debated since it was discovered and first described nearly forty years ago. Based on new age information from exploration wells in the Draugen Field on the Trøndelag Platform, the Molo Formation is now determined to be of Late Miocene to Early Pliocene age. It is interpreted to be the proximal equivalent to the deeper marine Kai Formation in the Norwegian Sea and a lateral equivalent to the Utsira Formation in the North Sea. These formations were all deposited as a result of the compression and uplift of mainland Norway in mid Miocene time. In this paper we describe and document the datings and formally define the Molo Formation as a new stratigraphic unit

Northern Svalbard Composite Tectono-Sedimentary Element

The Northern Svalbard Composite Tectono-Sedimentary Element (CTSE) comprises Proterozoic, Early Paleozoic, and Devonian sedimentary rocks preserved in northern Svalbard and on the adjacent shelf margin. Here, the sedimentary strata of the CTSE are preserved between complexes of metamorphic and crystalline basement rocks. The Northern Svalbard CTSE covers four main tectonostratigraphic elements: Tonian syn-rift, Neoproterozoic to Cambrian post-rift, Ordovician passive margin, and late Silurian?/Devonian syn-extensional basins. The oldest documented sedimentary strata are greywacke and shale deposited after the Greenvillian Orogeny and assumed to be younger than 980-960 Ma. The present CTSE further includes Cambrian-Ordovician sedimentary rocks in Ny-Friesland and Nordaustlandet, while the dominant part of the CTSE are continental Old Red Sandstone sediments of the late Silurian?/Early Devonian Red Bay and Siktefjellet groups and the Early-Late Devonian Andreé Land Group onshore northern Spitsbergen. Locally, the Cambrian-Ordovician formations contain petroleum source rocks with moderate total organic carbon contents and relatively high hydrogen index values, suggesting a good potential for oil generation. There are possible reservoirs, seals, and traps in some of the basins, but the CTSE generally holds a very limited potential as a petroleum province, particularly as the region is under strict environmental protectio

Late Jurassic and Cretaceous palynostratigraphy of the onshore Rovuma Basin, Northern Mozambique

Late Jurassic and Cretaceous palynomorph assemblages were recovered from the Macomia, Pemba, and Mifume formations from the onshore Rovuma Basin, northern Mozambique. These assemblages provide new evidence for an Aptian–Albian age for the Macomia Formation and the upper member of Pemba Formation, and confirm that these two stratigraphic units are coeval and laterally continuous. The lower member of the Pemba Formation contains Kimmeridgian–Tithonian palynomorphs, thus documenting for the first time the existence of Upper Jurassic strata north of Nacala in the onshore Rovuma Basin. The rich and diverse dinoflagellate cyst assemblage recovered from the Mifume Formation is of late Campanian age. This indicates an early Late Cretaceous hiatus between the sandstones of Pemba Formation, and the marls of the overlying Mifume Formation. The hiatus corresponds to a break in sedimentation prior to a rapid, global marine transgression, recognised in the Rovuma and Mozambique basins, during the middle Campanian, associated with the onset of Gondwana fragmentation. Earlier, Late Jurassic faulting produced local half-grabens filled with continental debris, for example the N’Gapa Formation of northern Mozambique