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During the Neoproterozoic, a supercontinent commonly referred to as Rodinia, supposedly formed at ca. 1100 Ma and broke apart at around 800–700 Ma. However, continental fits (e.g., Laurentia vs. Australia–Antarctica, Greater India vs. Australia–Antarctica, Amazonian craton [AC] vs. Laurentia, etc.) and the timing of break-up as postulated in a number of influential papers in the early–mid-1990s are at odds with palaeomagnetic data. The new data necessitate an entirely different fit of East Gondwana elements and western Gondwana and call into question the validity of SWEAT, AUSWUS models and other variants. At the same time, the geologic record indicates that Neoproterozoic and early Paleozoic rift margins surrounded Laurentia, while similar-aged collisional belts dissected Gondwana. Collectively, these geologic observations indicate the breakup of one supercontinent followed rapidly by the assembly of another smaller supercontinent (Gondwana). At issue, and what we outline in this paper, is the difficulty in determining the exact geometry of the earlier supercontinent. We discuss the various models that have been proposed and highlight key areas of contention. These include the relationships between the various ‘external’ Rodinian cratons to Laurentia (e.g., Baltica, Siberia and Amazonia), the notion of true polar wander (TPW), the lack of reliable paleomagnetic data and the enigmatic interpretations of the geologic data. Thus, we acknowledge the existence of a Rodinia supercontinent, but we can place only loose constraints on its exact disposition at any point in time.

We use new data from the southern Weddell Sea continental shelf to describe water mass conversion processes in a formation region for cold and dense precursors of Antarctic Bottom Water. The cruises took place in early 1995, 1998, and 1999, and the time series obtained from moored instruments were up to 30 months in length, starting in 1995. We obtained new bathymetric data that greatly improve our definition of the Ronne Depression, which is now shown to be limited to the southwestern continental shelf and so cannot act as a conduit to northward flow from Ronne Ice Front. Large-scale intrusions of Modified Warm Deep Water (MWDW) onto the continental shelf occur along much of the shelf break, although there is only one location where the MWDW extends as far south as Ronne Ice Front. High-Salinity Shelf Water (HSSW) produced during the winter months dominates the continental shelf in the west. During summer, Ice Shelf Water (ISW) exits the subice cavity on the eastern side of the Ronne Depression, flows northwest along the ice front, and reenters the cavity at the ice front's western limit. During winter the ISW is not observed in the Ronne Depression north of the ice front. The flow of HSSW into the subice cavity via the Ronne Depression is estimated to be 0.9 ± 0.3 Sv. When combined with inflows along the remainder of Ronne Ice Front (reported elsewhere), sufficient heat is transported beneath the ice shelf to power an average basal melt rate of 0.34 ± 0.1 m yr−1.

We investigated the use of an automated routine to determine moment magnitudes from the displacement spectra of local and regional earthquakes. Two algorithms, a genetic algorithm and a converging grid search, were developed and tested with earthquake data from Mexico, Norway, and Deception Island (Antarctica). It was found that compared with manual analysis, the algorithms give reliable automatic moment magnitude (Mw) estimates in the range -1 < M < 8. The converging grid search appeared to be more cost-effective than the genetic algorithm. Mw at local and regional distances seems superior to amplitude-based magnitudes that saturate for large earthquakes. The application of the automated algorithm in near real time may help to obtain a nonsaturated magnitude estimate in the case of a large earthquake immediately after the earthquake has occurred. Also, the method can be useful for processing large amounts of data.

The Jutulsessen nunataks (72°00′S; 2°30′E), Gjelsvikfjella, Dronning Maud Land (DML), consist mainly of migmatites of two types. A heterogeneous banded amphibolite facies gneisses and a more homogeneous part. In the more homogeneous part, partial melts form along axial planes to tight folds. Numerous pegmatitic dykes occur in both migmatites. The homogeneous part of the migmatite has a granodiorite composition. It displays the depletion of Nb–Ta typical for rocks from destructive plate margins and a strongly fractionated REE pattern, specially in LREE (La/Lu ratios varying between 500 and 800). SIMS dating of zircon from the homogeneous migmatite and two pegmatite dykes resulted in two age groups. A concordant age of 1163±6 Ma is calculated from zircon crystals with no rim/core structure and from cores from structurally complex crystals. This age represents the age of the protolith of the migmatite. A Cambrian age of 504±6 Ma is obtained from zircon rims and from sector-zoned zircons. This age represent the time of migmatisation. Sm–Nd depleted mantle model ages range from 1390 to 1770 Ma and suggest that the protolith to the migmatites contained components of older crust (pre-1163 Ma). An igneous complex consisting of a syenite plug (Stabben syenite), gabbroic rocks and aplitic dykes intrudes the metamorphic complex. The syenite and the aplitic dykes are neither deformed nor migmatised or penetrated by pegmatitic dykes. These rocks have elevated LREE and LILE concentrations with an La/Lu ratio of 450 and an Nb–Ta trough. The gabbroic rocks range in composition from melagabbro to monzogabbro and host numerous pegmatitic dykes. SIMS zircon U–Pb data from the Stabben syenite give an age of 500±8 Ma. This age is regarded as the intrusive age of the Stabben syenite. By the single zircon–Pb evaporation method an age of 495±14 Ma is obtained from the aplitic dykes. Sm–Nd depleted mantle model ages between 1800 and 2220 Ma indicate that the dykes formed from a Paleoproterozoic source. A Mesoproterozoic volcanic arc setting of DML and a correlation with the Natal Province, as suggested by several authors, is supported by data in this study. The studied area has consequently been a part of the Kaapvaal/Kalahari craton since Mesoproterozoic time. The Cambrian migmatisation and the intrusions are interpreted as a result of post-collision activity related to the collision between the Kalahari craton and the combined block of Antarctica and Australia during the final assembly of Gondwana. This collision is suggested to be included in the Kuunga Orogeny introduced by Meerat and Van der Voo [J. Geodynam. 23 (1997) 223].

A detailed and comprehensive map of the distribution patterns for both natural and artificial radionuclides over Antarctica has been established. This work integrates the results of several decades of international programs focusing on the analysis of natural and artificial radionuclides in snow and ice cores from this polar region. The mean value (37±20 Bq m−2) of 241Pu total deposition over 28 stations is determined from the gamma emissions of its daughter 241Am, presenting a long half-life (432.7 yrs). Detailed profiles and distributions of 241Pu in ice cores make it possible to clearly distinguish between the atmospheric thermonuclear tests of the fifties and sixties. Strong relationships are also found between radionuclide data (137Cs with respect to 241Pu and 210Pb with respect to 137Cs), make it possible to estimate the total deposition or natural fluxes of these radionuclides. Total deposition of 137Cs over Antarctica is estimated at 760 TBq, based on results from the 90–180° East sector. Given the irregular distribution of sampling sites, more ice cores and snow samples must be analyzed in other sectors of Antarctica to check the validity of this figure.

Longlines that sink fast reduce the time available to seabirds to attack baited hooks and are important in efforts to minimise seabird by-catch in longline fisheries. We measured sink rates in still seawater of longlines commonly used in the world’s demersal fisheries. Lines with integrated weight (lead cores) sank two to three times faster (45–52cm/s) than conventional (unweighted) lines. Conventional 9mm diameter lines made from polyester sank at 23cm/s compared to 18cm/s for 9mm Silver lines (blend of polyester, polyethylene and polypropylene). Samples of lines set by hand in still water sank significantly faster than longlines set from a fishing vessel, presumably because of the effect of the sea swell and upwellings from the propeller on the line set from the vessel.

In this study laboratory experiments of sea ice formed on a vertical surface with initial temperature of −30 to −50°C are presented. The ice formation is rapid, and in 300 s >5 mm of sea ice is formed. Ice formation cooled and salinified the water, and induced a vertical down wards flow of ∼5 mm/s with a boundary layer about 5 mm thick. This ice has a structure with columnar crystals that have small circular cross sections (0.2–1.0 mm) and sea ice salinities are between 24 and 32. A simple model approach indicate that the thermal conductivity of such ice is lower than for other types of sea ice.

We present mid-Pliocene (4.3–2.6 Ma) benthic stable oxygen and carbon isotope data from Ocean Drilling Program Site 1092 (ODP Leg 177) drilled in the sub-Antarctic sector of the Southern Ocean. The results are compared with the stable isotope results from nearby Site 704 (ODP Leg 114). Oxygen isotope data show that minimum values are about 0.5‰ less than those of the Holocene, which is consistent with the results from Site 704, indicating only minor deglaciation of Antarctica during the studied interval. Oxygen isotope data from both Site 1092 and Site 704 are slightly higher relative to Pacific values during several intervals which could be related to the contribution of warm, saline North Atlantic Deep Water (NADW). Comparisons of benthic carbon isotope gradients between sites located in the North Atlantic, sub-Antarctic sector of the Southern Ocean, and Pacific indicate that at times, the gradient between the Southern Ocean and the Pacific evolved differently than the Atlantic–Pacific gradient. This suggests that variations in NADW strength alone might not be responsible for the observed carbon isotope values in the Southern Ocean.

Livets opprinnelse er et mysterium. Ikke desto mindre er mange forskere beskjeftiget med å forsøke og rekonstruere dette. Moderne forskning på livet under ekstreme betingelser på Jorda som f.eks. i dyphavet, i en innsjø under isen i Antarktis eller i en gruppe sjeldne meteoritter, har ført til en viss optimisme når det gjelder å finne liv på planeten Mars og på Jupiters månesatelliter Europa, Callisto og Ganymede.

The spleens of several seals from both the Arctic and the Antarctic were isolated and weighed when contracted. Spleens of the crabeater, leopard, and Weddell seals formed 0.23%, 0.39%, and 0.86% of the seals' body weights; those of the hooded and harp seals formed 0.56% and 0.35% of the seals' body weights. In these 5 phocids, a contracted spleen relates to the seal's body weight according to the equation (in which weights are in kilograms; n=26; r2=0.65): contracted spleen=0.006 (body weight)-0.11. Further, using the criterion reported in the literature that contracted spleens of hooded seal and harp seals weigh 80% less than when dilated, the sizes of dilated spleens were estimated for the 5 phocids of the study, plus that of the southern elephant seal. Dilated spleens ranged from 1 to 4% of the seal's body weight, which is in agreement with determinations of dilated spleens reported in the literature (harbor, 0.8–3.0%; harp, 1.5%; hooded, 2.2–4.0%). The general correlation among dilated spleens and the 6 phocids' body weights is: dilated spleen=0.026 (body weight)-0.39(where weights are in kilograms; n=31; r2=0.70). The size of the spleen (either contracted or dilated) from the different species of seals in this study appeared to be correlated with the diving capacity of the phocids, as given in the literature. The phocids with greater diving capacities are the ones with the larger spleens.

Precambrian granitoid gneisses and Cambrian syenites occur in Mülig-Hofmann- and Filchnerfjella, Dronning Maud Land, Antartica. The nunataks of Dronning Maud land are characterized by alternating dark and light decolourised rocks. This phenomena is observed all along the mountain range for minimum 150 km length and occur in different rock types. The dark parts contain granulite facies mineral assemblages including perthite, plagioclase, orthopyroxene, garnet, biotite and cummingtonite. The light zones contain amphibolite facies minerals typically microcline, amphibole, biotite and titanite. The light zones are restricted to halos around aplite and pegmatite dykes. The widths of the halos range from cm to several meters. In the 800 m high wall of Rakekniven three sets of decolouration zones are observed. Decolouration along dykes is the typically occurrence of the phenomena, however in many places only small remnants of the dark coloured rocks occur and some nunataks are completely decolourised. In mineral scale the feldspars of light rocks are fractured and microveins occur filled by albite and white mica. The veins are irregular but occur in 2-3 main directions. Microstructures are studied towards the central dyke of decolouration zones; fracture density in the feldspars increase, perthite is transformed to microcline and plagioclase recrystallises to small grains of albite and white mica. We interpret the decolouration to be caused by fluid emanated from aplites and pegmatites interacting with the granulites. During the fluid infiltration granulite facies rocks are transformed to amphibolite facies rocks. Fracturing on mineral scale is the important mechanism for transporting fluids out into the wall rock from the dykes. The resulting recrystallisation allows for further fluid transport during breakdown of minerals and production of new grain boundaries. The process is thorough as whole nunataks are affected by the transformation. The frequent distribution of decolouration zones throughout the mountain range indicates a regional importance of the fluid infiltration process.

Grain-size is an important but not well-known characteristic of snow at the surface of Antarctica. In the past, grain-size has been reported using various methods, the reliability, reproducibility and intercomparability of which is not warranted. In this paper, we present and recommend, depending on available logistical support, three techniques of snow-grain sampling and/or imaging in the field as well as an original digital image-processing method, which we have proved provides reproducible and intercomparable measures of a snow grain-size parameter, the mean convex radius. Results from more than 500 samples and 3000 images of snow grains are presented, which yield a still spatially limited yet unprecedentedly wide picture of near-surface snow grain-size distribution from fieldwork in Antarctica. In particular, except at sites affected by a very particular meteorology, surface grains in the interior of the ice sheet are uniformly small (0.1–0.2 mm). The climate-related increase of grain-size with depth through metamorphism is, as expected, not spatially uniform. Our Antarctic snow grain-size database will continue to grow as field investigations bring new samples, images and measures of snow grain.