The Holocene fossil marine macrofauna of the Vestfold Hills, East Antarctica

The Holocene (< 10,000 years old) fossil marine macrofauna (molluscs, polychaetes, mammals and birds) of the Vestfold Hills, Antarctica (68°30'S, 78°00'E) is described. All species are extant, with circumantarctic or wider distributions and wide depth ranges. At Heidemann Bay, Pleistocene-age (> 30 ky old) shell fragments occur in a Holocene moraine. These are interpreted as being glacially reworked fossil shells. Holocene benthic estuarine and coastal molluses and serpulid worm tubes are abundant on the flanks of terraces above saline and hypersaline lakes. Extensive radiocarbon dating gives a chronology of these deposits which were not synchronous. Mummies of seals and penguins, which are concentrated on the shores of the saline lakes and scattered across the Hills, are of no use in dating geomorphological events. Marine fossils in moraines are difficult to interpret because they can be glacially-transported live or fossil shells, or deposited after wind transport. The fossil fauna has such a wide ecological range that it indicates only in general terms that for part of the Pleistocene and most of the Holocene, climatic conditions were broadly similar to the present.     

Early Weichselian peat at Brumunddal, southeastern Norway

Stratigraphical investigations of an inter-till peat in Brumunddal suggest a major interstadial of Early Weichselian age. The insect fauna and the pollen composition indicate a mean July temperature 2–3C lower than today during the climatic optimum. Larch and spruce immigrated at the end of the interstadial, which is tentatively correlated to the Jamtland Interstadial.     

Low-sulfide PGE mineralization in layered intrusion ring,Vestfold Hills,Antarctica

This paper presents results of the study of norite complex from the Vestfold Hills (East Antarctica) containing a low-sulfide type of mineralization. The ore mineralization occurs in specific rock types and along the contact of norites the host rocks. Three mineralization types: Fe–Ni–Cu sulfide, oxide, and PGE-bearing are known. PGE mineralization is represented by palladium–bismuth tellurides of the michenerite–merenskyite series. A model of ore-formation succession and a concept of the origin of low-sulfide PGE mineralization by means of crystallization and subsequent evolution of monosulfide and intermediate solid solutions have been developed.     

Economical Potential of An Ultramafic Rock at The Kval ya Island,North Norway

A low-grade metamorphic ultramafic rock at the Kval ya Island, North Norway, shows Ni content up to 5 600 ppm, and an average content of 2 500 ppm Ni. Olivine is absent from the rock, and Ni is principally bonded in pentlandite, violarite and millerite. The rock might be considered as a low-grade ore, with 0.2wt%– 0.56wt% Ni. Other metals that might be of economic interest to extract from the rock include Co (from pentlandite and violarite), and Cr and Fe (from magnetite).     

Metamorphism of basic and pelitic rocks at Sulitjelma,Norway

The Sulitjelma area of the Scandinavian Caledonides consists of a variety of metasedimantary units with small basic intrusions, and a large ophiolitic complex of predominantly basic composition. All units underwent prograde greenschist facies to amphibolite facies regional metamorphism during the Scandinavian phase of the Caledonian orogeny. The resultant mineral assemblages and relationships are consistent with the presence of a miscibility gap in the actinolite-hornblende series under greenschist facies conditions; a garnet forming reaction in pelites involving the consumption of carbonate in order to produe the observed grossular content; some conflict between low-baric and medium-baric pressure estimates from equilibria involving Ca amphibole bearing assemblages in metabasites.     

Late Weichselian sea level changes at Sotra, Hordaland, western Norway

Sediments from twenty-eight basins were surveyed; ten of these basins with a representative lithostrati-gfaphy wee studied to determine their isolation from the sea during Late Weichselian. Diatom analysis was used to determine salinity changes, which were dated by pollen analysis and the radiocarbon method. The area was deglaciated in the early Boiling, and a regression of about 5 m followed. A transgression of more than 10 m started in late Boiling and terminated in middle Younger Dryas, with a transgression maximum between 38.2 and 40 m above present sea level. All the investigated basins were finally isolated in late Younger Dryas/early Preboreal, during a rapid regression. Repeated cycles of chinophilous/ chinophobous plant communities in the area reflect climatic changes in the period. No evidence of an Older Dryas ice readvance was found.     

Vein Metasomatism in Peridotite at Kalskaret near Tafjord, South Norway

Enstatite, anthophyllite, tremolite, and chlorite are developedin a zoned sequence as a vein cross cutting a peridotite bodylocated within the basal gneiss region of southern Norway. Theyare believed to have formed during the main regional metamorphicevent at temperatures around 700 °C and P_total in excessof 6 kb. It is thought that metasomatic reaction occurred by means of(and to a lesser extent directly involved) a pore fluid phaserich in alkali halides. The zonal sequence now found representsthe results of incomplete reaction of the peridotite body withpore fluids derived from the acid gneiss country rocks. Eachzone illustrates partial attainment of equilibrium one componentat a time. Local equilibrium was maintained between the fluidphase and the various silicates during reaction. Questions ofcomponent ‘mobility’ are considered. There appears to be no doubt that enstatite developed by metasomaticreaction on this small scale. This raises interesting possibilitiesof metasomatic development on a larger scale: enstatite occursas a major constituent of some ultrabasic bodies in this regionof southern Norway.     

Weichselian sediments containing redeposited interstadialhnterglacial fossils at Slettaelva, North Norway

The following stratigraphy was found at Slettaelva, near Troms (from bottom to top): greenish basal till (unit A), laminated c lay (unit B), fossitiferous basal till (Unit C). Unit A probably derives from an early Weichselin local glaciation, Unit B comprises lacustrine sediments which were apparently deposited in an early Weichselian tundra-like enivironment, Unit C, which contains reworked fossils of moulluscs, palynomorphs and foraminifera, was deposited by a continenntal ice shcet. Amino acid ratios of Mya truncata and plaaeontological evidence indicate that unit Ccontains a mixed fossil assemblage, probably of Eemian and Weichselian interstadial age.     

Podzol development, vegetation change and glacier variations at Haugabreen, southern Norway

¹⁴C dating and pollen analysis of the surface organic (LFH) horizons of several humo-ferric podzol profiles forming a soil catena close to the 'Little Ice Agc' outer moraine ridge of Haugabreen, southern Norway, are used to examine the timing and nature of podzol development at the low-/sub-alpine margin of the Jostedalsbreen area. Comparison with results from a palaeosol buried beneath the outer moraine shows that FH horizon development began as early as 5,265 ± 65 B.P., but that it was not synehronous across the profiles, the latest profile having a date of 3,590 ± 65 B.P. It is argued that surface organic horizons developed as a response to a deterioration of climate and possibly the recrudescence of the Myklebustbreen ice cap at c . 5,000 B.P., and that the dates for horizon initiation vary according to local topographic and soil-hydrologic conditions. It is still uncertain whether the hump-ferric podzols were preceded by brown earths or weakly podzolised sub-alpine podzolic soils, but at all sites where pollen evidence is available it appears that FH initiation took place beneath Betula woodland.     

Late Archaean granulite facies metamorphism in the Vestfold Hills,East Antarctica

Granulites of the Vestfold Hills record a pulsed end-Archaean to early Palaeoproterozoic M1–M2 evolution that is distinct from other Archaean areas in East Antarctica and cratonic domains placed adjacent to East Antarctica in Gondwana reconstructions. Pressure and temperature conditions of the end-Archaean to earliest Palaeoproterozoic (2501–2496 Ma) M1 granulite facies metamorphism in the Vestfold Hills have been constrained from mineral assemblages and thermobarometry of Fe-rich paragneisses. Reintegrated compositions of exsolved subcalcic clinopyroxenes and pigeonites in a metaironstone yield temperatures of 895 ± 35 °C, whilst reintegrated compositions of perthitic feldspars in semipelitic paragneisses give minimum estimates of 860 ± 30 °C. These results rule out the extreme ultrahigh temperature (UHT) conditions previously proposed for M1 in the Vestfold Hills. Pressures of metamorphism during M1 are estimated as 8.1 ± 0.9 kb at 850 ± 40 °C from hercynite + sillimanite + almandine + corundum and retrieved Fe–Mg–Al relations in orthopyroxene coexisting with garnet. A second metamorphic event, M2, occurred at 600–660 °C and 6–8 kb based on thermometry of recrystallised pyroxene neoblasts and thermobarometry applied to M2 garnet–quartz symplectites formed on orthopyroxene and garnet. The intervening emplacement of the magmatic Crooked Lake Gneiss Group precursors occurred at similar or shallower pressures prior to D2–M2, an event that caused tectonic interleaving and reactivation of the Vestfold Hills basement at mid-crustal depths in the earliest Palaeoproterozoic, prior to its unroofing to shallower levels (3–5 kb) by 2470 Ma. The lack of correlative Archaean histories in areas that were formerly adjacent in Gondwanan reconstructions is consistent with the Vestfold Hills region either being exotic to the East Antarctic Shield until the final (Neoproterozoic to Cambrian) amalgamation of Gondwana, or being accreted to part of East Antarctica in a Proterozoic event distinct from the Rayner–Eastern Ghats tectonism that united much of India with Antarctica at 1000–900 Ma.     

Lateglacial vegetation and environment at the mouth of Hardangerfjorden, western Norway

This article is a detailed pollen analysis and accurate AMS chronology of the Lateglacial of two coastal sites in western Norway. The area was deglaciated around 14 600 cal. yr BP or shortly before. The earliest vegetation was open, with a pioneer mosaic of vegetation on mineral soils, including snowbed communities, and plants on wind-blown ridges. Later, more stable vegetation developed with Empetrum as an important constituent. Scattered tree birches were established in the area in the last part of the Bølling/Allerød (GI-1). The pollen record from Vassnestjern indicates three short-lasting cold periods: c . 14 050 to 13 900, 13 800 to 13 700 and 13 150 to 13 000 cal. yr BP. It has been suggested that the last-mentioned period, detected at both sites, corresponds with the Gerzensee/Killarney Oscillation. From about 12 750 cal. yr BP, the vegetation was affected by the Younger Dryas (GS-1) cooling, which caused the vegetation to break up and humus-soil communities to disappear. In the early Holocene, the humus-soil communities re-established and open birch forests developed. This Lateglacial vegetation development is broadly similar to the reconstructed vegetation development in other parts of southwestern Norway.     

Inverted isograds at Sulitjelma, Norway: the result of shear-zone deformation

Abstract At Sulitjelma, Norway, there is a major inversion of metamorphic isograds beneath an inverted but undisrupted ophiolite. The flysch-like Furulund schist in which the inverted isograds occur is also inverted and the early folds in it are downward facing. The isograds cut across the axial surfaces of early folds and across the schistosity. These relationships are explained as the consequence of metamorphism during the progressive development of a large overfold. The inverted limb of the overfold is regarded as a major, thick, gently-dipping shear zone, separating the lower-grade, lower part of the Caledonian allochthon below from the higher-grade upper part of the allochthon above. The association between stratigraphical inversion, downward-facing of syn-schistosity folds and metamorphic inversion is explained by the progressive development of the shear zone. It is suggested that the presence of such shear zones is a common feature of orogenic belts formed by continental collision.     

An investigation of subglacial processes at the microscale from Briksdalsbreen, Norway

The subglacial processes at Briksdalsbreen, Norway, are examined by a combination of sedimentology, thin section and scanning electron microscope (SEM) analysis of till samples from an exposed subglacial surface and from beneath the glacier. Studies of a fluted surface indicate that subglacial deformation is occurring on a field scale with flutes forming behind most clasts 0·6 m high. At the thin section scale (0·014–2·0 mm) it is seen that deformation is by rotation and attenuation and is dependent on till texture. At the SEM scale (0·1–0·4 mm) it is seen that erosion is controlled by abrasion and percussion which produces distinct grain ‘styles’ as part of an erosional continuum. Overall it is shown that rotation and attenuation is a dominant process at all scales and that the clast interactions associated with different scale perturbations within the shear zone control erosion and deposition, as well as landform and fabric production.     

The deglaciation between Skjerstadfjord and Svartisen, north Norway

Six successive zones with distinctive marginal moraines are recognized. Based on radiocarbon dates the ages of the three oldest zones are believed to be: older than 11,100 years B.P. (Vasdal event), about 10,900 B.P. (Glomfjord-Straumöy events), and between 10,400 and 9500 B.P. (Skjerstad event). The three youngest zones are Preboreal. Corresponding marine sediments, shorelines, glaciation limits and other glacial features are described.     

The Bidjovagge copper-gold deposits of Western Finnmark,Norway

The Bidjovagge copper-gold deposits occur in the Svecokarelian Caskias Group. The rocks in the mineralized district consist of greenstones, carbonate rocks, albite felsite and graphite felsite. Four ore bodies are found in albite felsite and graphite felsite over a strike length of 2.5 km. The ore bodies represent remobilizations from syngenetic, stratabound mineralization. Ore minerals of economic significance are chalcopyrite and native gold. An assemblage of gold and tellurides in the country rock occurs as a late stage mobilization product.

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Zusammenfassung Das Bidjovagge Kupfer-Gold-Vorkommen liegt in der Svecokarelischen Caskias-Gruppe. Die Gesteine innerhalb des mineralisierten Distriktes bestehen aus Grünsteinen, Karbonatgesteinen, Albitfelsiten und Graphitfelsiten. Vier Erzkörper wurden innerhalb der Albitfelsite und Graphitfeisite über eine streichende Länge von 2,5 km gefunden. Die Erzkörper repräsentieren Remobilisate von syngenetischen, schichtgebundenen Mineralisierungen. Erzmineralien von wirtschaftlicher Bedeutung sind Kupferkies und Gold. Verwachsungen von Gold mit Telluriden findet man in den Nebengesteinen als Mobilisationsprodukte einer späteren Phase.

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Résumé Les gisements de cuivre et d'or de Bidjovagge se trouvent dans le groupe svécokarélidien de Caskias. Les roches de ce district minier consistent en roches vertes, roches carbonatées et felsites albitiques et graphitiques. Quatre gisements de minerai ont été trouvés dans les felsites albitiques et graphitiques sur une distance de 2,5 kilomètres. Ces gisements représentent des remobilisations d'une minéralisation syngénétique sédimentaire. La chalcopyrite et l'or sont les seuls minéraux d'importance économique. Des émissions d'or et de tellurures dans les épontes paraissent être le produit d'une phase de mobilisation tardive.

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Late Weichselian vegetation, climate, and floral migration at Sandvikvatn, North Rogaland, southwestern Norway

Pollen analysis from Sandvikvatn has elucidated the local Late Weichselian vegetational and climatic history since deglaciation about 14,000 B.P. The pleniglacial period, the first of three climatic main periods and ending c. 13,600 B.P., is an Artemisia -dominated pioneer vegetation on disturbed mineral soils. The Late Weichselian Interstadial (13,600-11,000 B.P.) comprises a Salix -shrub consolidation phase and, from 12,900 B.P., a birch-forest optimum phase. In the Younger Dryas Stadial (11,000–10,100 B.P.) the Artemisia -dominated pioneer vegetation returns. Three climatic oscillations are demonstrated at intervals of about 500 years within the Interstadial. The oldest two, about 12,500 and 12,000 B.P., could both have been connected with the 'Older Dryas'. Cold winters and strong winds, causing soil erosion and drought, are suggested as important factors during the climatic periods unfavourable to woody vegetation. In the pleniglacial and Younger Dryas periods the winds are assumed to be katabatic. During the whole Late Weichselian southern species dominate locally. A northwards spread is demonstrated for the majority of the local late-glacial taxa, including the endemic Primula scandinavica and also Papaver radicatum and Aconitum , both previously discussed as part of the hypothesis of Weichselian ice-free refugia.     

Late Weichselian vegetation,climate, and floral migration at Liastemmen,North Rogaland,south-western Norway

Palynological results from Liastemmen indicate a tripartite division of the Late Weichselian. In the pleniglacial period, from deglaciation ca. 14000 BP to ca. 13000 BP, Artemisia-dominated pioneer vegetation on disturbed, mineral-soil was strongly influenced by cold winters and katabatic winds. The Late Weichselian Interstadial (ca. 13000 BP-ca. 11000 BP) comprises a Salix-shrub consolidation phase, and from ca. 12700 BP a tree-birch phase. In the last 500 years of this period July and January means are estimated to about 16°C and between ?2°C and ?6°C, respectively. In the Younger Dryas Stadial (ca. 11000 BP-ca. 10200 BP) Artemisia-dominated vegetation returns. Three brief climatic deteriorations (ca. 12 250 BP, 11 700 BP, and 11 300 BP), unfavourable to woody vegetation on humus soils, are demonstrated within the interstadial. Critical climatic factors include cool winters and strong winds, exposing vegetation and soil to frost, drought, and erosion. The oldest and strongest oscillation, probably involving local deforestation, is correlated with the ‘Older Dryas deterioration’. Boreal-circumpolar, eurasiatic, and arctic-alpine plants dominated the late-glacial flora. For the majority of the late-glacial taxa a northward migration is demonstrated. This may also apply for Papaver radicatum, Pinguicula alpina, and Primula scandinavica, all with bicentric distributions in Norway today.     

Contemporary terminal-moraine ridge formation at a temperate glacier: Styggedalsbreen, Jotunheimen, southern Norway

Terminal-moraine ridges up to 6 m high have been forming at the snout of Styggedalsbreen for two decades. Based on intermittent observations during this period, combined with a detailed study of ridge morphology, sedimentary structures and composition during the 1993 field season, a model of terminal-moraine formation that involves the interaction of glacial and glacio-fluvial processes at a seasonally oscillating ice margin is presented. In winter, subglacial debris is frozen-on to the glacier sole; in summer, ice-marginal and supraglacial streams deposit sediments on the wasting ice tongue. The ice tongue overrides an embryonic moraine ridge during a late-winter advance and a double layer of sediment (diamicton overlain by sorted sands and gravels) is added to the moraine ridge during the subsequent ablation season. Particular ridges grow incrementally over many years and exert positive feedback by enhancing snout up-arching during the winter advance and constraining the course of summer meltwater streams close to the ice margin. The double-layer annual-meltout model is related to moraine formation by the stacking of subglacial frozen-on sediment slabs (Krüger 1993). Moraine ridges of this type have a complex origin. are not push moraines, and may be characteristic of dynamic high-latitude and high-altitude temperate glaciers.