Transitional submarine fan deposits from the late Precambrian Kongsfjord Formats submarine fan, NE Finnmark, N. Norway

ABSTRACT Three transitional submarine fan environments are recognized in the late Precambrian, 3-2 km thick Kongsfjord Formation in NE Finnmark, North Norway, namely: (1) middle to outer fan; (2) fan lateral margin, and (3) fan to upper basin-slope deposits. Middle to outer fan deposits have a high proportion of sandstones, typically showing Bouma T _bede with T _a in the thicker beds. Deposition was mainly from sheet flows with rare shallow channels. Middle to outer fan deposits are an association of sandstone packets less than 10 m thick but commonly only a few metres thick, interpreted as channels or lobes. Interchannel and fan fringe deposits occur as discrete packets of beds between the thicker bedded and coarser grained channel or lobe deposits. Fan lateral margin deposits are recognized on the basis of their stratigraphic position adjacent to inner/middle fan deposits. They are characterized by: (a) a relatively high proportion of fine-grained sandstone/siltstone turbidites compared to other major fan environments; (b) relatively small channels oriented at various angles to the regional basin slope; (c) lobes associated with channels, and (d) abundant clastic dykes and other soft-sediment deformation. Fan lateral margin deposits are distinguished from the outer fan/basin plain successions on account of the very high proportion of siltstone turbidites comparable with middle fan inter-channel deposits. Fan to upper basin-slope deposits occur at the top of the formation as an alternation of sandstone turbidites, most of which are laterally discontinuous, and very thin-bedded upper basin-slope siltstones with slide deposits.     

Possible retrogressive flow slide deposits from the Kongsfjord Formation: a Precambrian submarine fan, Finnmark, N. Norway

Three thinning and fining-upward turbidite sequences are described from the Precambrian Kongsfjord Formation, a 3.5 km thick flysch succession. Their thicknesses range between about 2 and 5 m. They show a progressive upward decrease in bed thickness, bulk mean grain size and the ratio of the higher to lower energy division of the Bouma sequence. In one case, however, there is an initial upward bed thickness and grain size increase, with an increase in the proportion of the higher energy division. The absence of structureless mud of the Bouma E division and the presence of wavy interfaces between beds, together with similar palaeo-currents within each sequence suggest that these sequences resulted from related depositional events. These sequences are interpreted as the deposits of retrogressive flow slides, as an alternative to the classic mechanism of channel fill after abandonment.     

Petrography and petrogenesis of nephelinized metagabbros from Finnmark,Northern Norway

Plagioclase in olivine metagabbros metasomatized by nepheline syenite magmas was replaced by intergrowths of nepheline and vesuvianite or salite together with smaller amounts of calcic amphibole. Olivine was simultaneously replaced by diopside. The survival of the gross features of protolith textures and clustering of line intersections in composition-volume diagrams suggest that nephelinization took place at approximately constant volume and oxygen content. Nephelinization involved the introduction of Na, K and Fe³⁺ in an infiltrating peralkaline fluid and depletion of Fe²⁺ and Fe^tot and was promoted by the primary mineral parageneses of the protoliths. Concurrent fenitization of quartzo-feldspathic gneiss without the generation of feld-spathoids shows that the processes of nephelinization and fenitization may result from the same fluid.     

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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Further analyses of radiogenic minerals from the Bidjovagge gold-copper deposit,Finnmark, Northern Norway

Summary We recently reported U/Pb and Sm/Nd dates on davidite from albitic felsites hosting the gold-copper mineralization of the Bidjovagge gold-copper deposit of northern Norway (69°17N, 22°29E). Isotopic dating of the north-south trending Proterozoic Kautokeino greenstone belt host rocks is sparse and confirmation of the dates was desirable, since the U/Pb data in particular were highly discordant and therefore somewhat uncertain.We have now supplemented the earlier measurements with U/Pb dating of uraninite from the felsites. The new uraninite data yield a well defined upper intersection with the concordia at 1837 ± 8 Ma, somewhat younger than the age of 1885 ± 18 Ma obtained on the davidites. The fact that the two minerals are apparently different in age lends support to the suggestion of a metamorphic origin of this deposit since a rather long period of cooling subsequent to metamorphism is indicated.

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Weitere Analysen von radiogenen Mineralen aus der Bidjovagge, Gold-Kupfer Lagerstätte, Finnmark, Nord-Norwegen

Zusammenfassung Wir haben erst kürzlich über U/Pb and Sm/Nd Daten von Davidit aus Albit-reichen, felsischen Gesteinen, in denen die Gold-Kupfer Mineralisation der Bidjovagge GoldKupfer Lagerstätte in Nord-Norwegen (69°17N, 22°29E) aufsitzt, berichtet. Es gibt wenige Isotopen-Datierungen der Gesteine, des N-S streichenden, proterozoischen Kautokeino Greenstone Belt. Außerdem ist eine Bestätigung der existierenden Daten wünschenswert, denn die bisherigen U/Pb Daten sind sehr widersprüchlich und unklar.Nun konnten wir die früheren Messungen mit U/Pb Daten von Uraninit aus den felsischen Gesteinen ergänzen. Die neuen Daten ergeben einen gut definierten Schnitt mit der Konkordia bei 1837 ± 8 Millionen Jahre, und sind damit etwas jünger als das von den Daviditen stammende Alter von 1885 ± 18 Millionen Jahre. Die Tatsache, daß diese beiden Minerale ein offensichtlich unterschiedliches Alter zeigen, unterstützt die Ansicht, daß die Lagerstätte metamorphen Ursprungs ist, wobei eine lange Periode der Abkühlung nach der Metamorphose zu vermuten ist.

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Late Precambrian tidal-flat deposits and algal stromatolites in the Båtsfjord formation,East Finnmark,North Norway

The Annijokka Member of the Late Precambrian Båtsfjord Formation consists of about 300 m of siliciclastic and carbonate deposits which accumulated on tidal flats, and includes several horizons of stromatolite biostromes. Seven main lithofacies are arranged in fining-up cycles a few metres thick. The cycles are terrigenous in the lower part and carbonate-rich higher up and are interpreted as reflecting shallowing-up conditions of deposition. Lithofacies distribution in the member as a whole also shows an upward decrease in the terrigenous component and grain size and increase in carbonates, thus suggesting that the Annijokka Member is regressive.The stromatolite biostromes of the member contain domal forms composed of calcite while the non-stromatolitic, though possibly in part algal-laminated, carbonate-rich beds of the member are dolomitic. This contrasting mineralogy suggests (1) penecontemporaneous supratidal dolomitization, and (2) a possibly freshwater-influenced origin of the domal stromatolites.     

Tide- and wave-dominated inshore and shoreline sequences from the late Precambrian, Finnmark, North Norway

The Late Precambrian Ekkerøy Formation of Finnmark, northern Norway represents a 40 m thick coarsening upward, prograding deltaic sequence. The upper 6 m of this formation consists of two small-scale fining upward sequences representing two contrasting shoreline environments. These two sequences have been the focus of a detailed facies analysis based on grain size, bed thickness and sedimentary structures. The study area comprises a series of horizontally bedded rocks which are continuously exposed for 3 km enabling individual facies and sedimentary structures be to traced-out laterally. The lower sequence exhibits a wide variety of tidal features including directional bimodality of both large-scale and small-scale cross-stratification, herringbone cross-stratification, various sandstone-mudstone alternations including lenticular and wavy bedding, and a general fining upward tendency. A detailed field analysis of the internal structures within the large-scale cross-stratified unit is presented and is interpreted as a sub-tidal channel complex. The associated sandstone-mudstone facies represents intertidal flats built up by tidal and storm-generated currents. The upper sequence displays a wide variety of wave-formed structures including wave-ripples and swash-lamination. Palaeocurrent data indicates a dominance of shoreward migrating megaripples and wave-ripple crests oriented approximately parallel to the inferred shoreline with a distinct longshore component. The sequence is interpreted as a beach-shoreface environment. In terms of sedimentary structures, palaeocurrent patterns and facies distributions, the sequence bears a remarkable similarity to the high-energy, non-barred shoreline of the modern Oregon coast U.S.A., described by Clifton, Hunter & Phillips (1971).     

Finger structures in the Lille Kufjord layered intrusion,Finnmark, Northern Norway

Highly irregular contacts are developed between peridotite and troctolite in layers forming the uppermost part of a transition zone between two of the cyclic units of the Lille Kufjord intrusion. The upwardly-directed peridotite fingers crosscut both the feldspar lamination and the feldspathic xenoliths in the troctolite and are interpreted as the result of the replacement of troctolite by peridotite. Similar structures are developed in the Rhum ultrabasic pluton. Replacement may have been caused by the migration of a more hydrous and magnesian magma trapped initially in olivine or olivine-clinopyroxene cumulates into plagioclase-olivine cumulates precipitated from a basaltic liquid.     

New Isotopic data from davidites and sulfides in the bidjovagge gold-copper deposit,Finnmark, Northern Norway

Summary The Bidjovagge gold-copper deposit (69°17'N, 22°29'E) occurs in the north-south trending Proterozoic Kautokeino greenstone belt. The greenstone belt consists of shallow marine sediments and mafic to ultramafic volcanites, which are intruded by diabase sills and granitoids. The sequence can be correlated with the 1930 to 2200 Ma Kiruna greenstone belt. Svecokarelian intrusions took place in two phases between 1880–1890 Ma and between 1860-1870 Ma.The deposit occurs in the stratigraphically lower part of the belt along a north-south trending anticlinal structure on the border between greenschist and amphibolite grade metamorphism within the Baltic-Bothnia megashear zone. The deposit is related to shear zones and hosted by albitic felsite, a metasomatic rock formed along the contact with the diabase sills.The only ore minerals of economic significance are native gold and chalcopyrite. Other common ore minerals are pyrite and pyrrhotite. Marcasite, magnetite, ilmenite, hematite, tellurides, rutile, sphalerite, galena, davidite and pentlandite occur in accessory amounts. A total of 10 samples of davidite, 14 sulfides and 4 samples of albitic felsite were analyzed for their isotopic compositions. Our best estimate for the age of the davidites (1885 ± 18 Ma) is based on the upper intersection of a U/Pb concordia diagram and is identified as the time of davidite (and gold) mineralization. This age is confirmed by a Sm/Nd date of 1886 ± 88 Ma on the same material. At 1339 ± 8 Ma, a metamorphic or metasomatic event disturbed the U/Pb system in some of the davidite samples and completely reset the U/Pb ratios in the albitic felsites. The sulfide minerals, containing trace U and Pb, were strongly disturbed during galena formation at about 500–550 Ma but apparently were initially formed at the same time as, or shortly after, the davidite. Based on an estimated time of formation of galena during the development of the early Paleozoic peneplain in the area, the Pb/Pb data are interpreted as a two-stage isochron with an initial age of 1876 ± 15 Ma.The relation between the mineralization and shear zones, the correspondence between the age of the mineralization and the Svecokarelian orogeny and the initial ratios of the radiogenic isotopes of the ore forming solutions, all support a metamorphic/metasomatic origin for the gold and copper mineralization.

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Neue Isotopendaten von Davidit und Sulfiden aus der Bidjovagge Gold-Lagerstätte, Finnmark, N.-Norwegen

Zusammenfassung Die Bidjovagge Gold-Kupfer-Lagerstätte (69°17'N, 22°29'E) liegt in dem N-S streichenden proterozoischen Kautokeino Grüngesteinsgürtel. Er besteht aus marinen Flachwassersedimenten, sowie mafischen und ultramafischen Vulkaniten, die von Diabas-Sills und von Granitoiden intrudiert werden. Diese Gesteinsabfolge kann mit dem 1930–2200 Ma alten Kiruna Grüngesteinsgürtel verglichen werden. Sveko-karelische Intrusionen erfolgten zweiphasig, zwischen 1880–1890 Ma und zwischen 1860 und 1870 Ma.Die Lagerstätte liegt in den stratigraphisch tieferen Anteilen diese Grüngesteinsgürtel entlang einer N-S streichenden Antiklinalstruktur im Übergangsbereich zwischen der Grünschiefer und Amphibolitfazies innerhalb der baltisch-bothnischen Mega-Scherzone.Sie ist an Scherzonen und an Albit-Felsite, einem metasomatisch am Kontakt mit den Diabas-Sills gebildeten Gestein, gebunden.Gediegen Gold und Kupferkies sind die wirtschaftlich wichtigsten Erzminerale. Pyrit und Magnetkies sind häufig. Markasit, Magnetit, Ilmenit, Hämatit, Telluride, Rutil, Zinkblende, Bleiglanz, Davidit und Pentlandit kommen akzessorisch vor. 10 Proben von Davidit, 14 Sulfide und 4 Proben von den Albit-Felsiten wurden auf ihre Isotopenzusammensetzung hin untersucht.Der obere Schnittpukt im U/Pb Concordiadiagramm ergab die beste Altersabschätzung für die Davidite (1885 ± 18 Ma). Dieses Alter wird als Zeitpunkt der Davidit (und Gold)-Mineralisation betrachtet. Ein Sm/Nd-Alter von 1886 ± 88 Ma bestätigt dieses. Ein metamorphes oder metasomatisches Ereignis, datiert mit 1339 ± 8 Ma störte das U/Pb System in einigen Daviditproben und führte zu einer vollständigen Reequilibrierung der U/Pb Verhältnisse in den Albit-Felsiten. Die Isotopenverhältnisse der Sulfide, die Spuren von U und Pb enthalten, wurden während der Bildung von Bleiglanz um etwa 500–550 Ma ebenfalls massiv gestört; die Sulfide wurden aber offensichtlich gleichzeitig, oder aber kurz nach Davidit, gebildet. Basierend auf einer Abschätzung des Bleiglanz-Bildungsalters im Zuge der Entwicklung einer altpaläozoischen Peneplain in diesem Gebiet, werden die Pb/Pb Daten als Zweistufen-Isochrone mit einem Ursprungsalter von 1876 ± 15 Ma interpretiert.Die Bindung der Mineralisation an Scherzonen, die Übereinstimmung des Mineralisationsalters mit dem der Sveco-karelischen Orogenese und die Isotopeninitiale der erzbildenden Lösungen belegen einen metamorph/metasomatischen Ursprung der Gold-und Kupfervererzungen.

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Evidence for currents associated with waves in Late Precambrian shelf deposits from Finnmark, North Norway

Abundant wave ripples with wavelengths of up to 0.3 m, top-surface granule lags and tabular sand-stone beds suggest that the interbedded sandstones and siltstones of the Skaergårdnes Formation are shallow marine deposits. A simple orthogonal relationship between crestal trends of wave ripples and trough axes/cross-bed dip directions indicates that bottom currents and surface waves were closely related, suggesting that wind-drift currents were responsible for deposition. Interbedding of the tabular sandstones with siltstone is more probably due to the patchy nature of sand cover on the sea floor than to episodic sand derivation from the coast. The top-surface granule lags indicate local, temporary excess of sand removal over supply, and were probably formed by both wave-winnowing and non-depositional megaripple migration. The well developed lags in this and similar ancient sediments suggest that winnowing, leading to bed armouring and sediment bypassing may be an important shallow marine process.     

Linnaeite from the Precambrian Raipas group of Finnmark,Norway

The previously described minerals of the linnaeite series occuring in the Borras and Raipas deposits near Alta, Finnmark, have been re-examined, mainly with the help of the electron microprobe. — As an introduction, a survey is made of the chemistry of the linnaeite series from published data and a new diagram is presented to show the relative variations of the four possible metallic elements. — The analyses confirm the respective chemical natures of the linnaeites from the two deposits and show a rather even chemistry within each deposit. Individual grains show inhomogeneities in element contents from outsides to centres and the forms of the inhomogeneities appear to vary depending on the relative abundance of the element concerned. The most abundant element in each case is relatively depleted in a very narrow outer zone or rim, whereas the minor elements show a more gradually diminishing (often irregular) content from grain boundary to centre. The intermediate elements show varying forms of distribution. The rim zones in the case of the major elements may be the result of diffusion out into the surrounding minerals, whereas the minor element distribution is possibly a primary one related to the growth of the linnaeite grains. — Results from one large, fractured linnaeite grain in the Raipas ore indicate considerable replacement by bornite along the internal fractures, though not at the original grain boundaries.

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Zusammenfassung Die früher beschriebenen Mineralien der Linneit-Serie, die in den Lagerstätten Borras und Raipas in der Nähe von Alta, Finnmark, vorkommen, wurden erneut untersucht, besonders mit der Elektronen-Mikrosonde. — Zunächst wird eine Übersicht der Daten über die Chemie der Linneit-Serie gegeben und ein neues Diagramm konstruiert, um die Variationsbreiten der vier metallischen Elemente von Linneit zu zeigen. — Die Analysen bestätigen die chemische Zusammensetzung der Linneite von den zwei Vorkommen, und zeigen eine weitgehende Übereinstimmung innerhalb jedes Vorkommens. Die Einzelkörner weisen Inhomogenitäten in der Elementverteilung vom Rand zur Mitte auf und ihre Form scheint mit der relativen Häufigkeit der betreffenden Elemente zu variieren. Das häufigste Element ist in jedem Fall in einer schmalen äußeren Zone relativ verarmt, während die untergeordneten Elemente eine mehr stufenweise Abnahme von Korngrenze bis Zentrum zeigen. Die intermediären Elemente zeigen wechselnde Verteilungsformen. Im Fall der Hauptelemente mag die verarmte äußere Zone ein Ergebnis von Diffusion in die umgebenden Mineralien sein, wogegen die Verteilung der untergeordneten Elemente möglicherweise primär, also an das Wachstum der Linneitkörner geknüpft ist. — Untersuchungen an einem großen aufgespaltenen Linneit-Korn aus dem Raipas-Erz deuten auf beträchtliche Verdrängungen durch Bornit entlang den inneren Spaltrissen, nicht aber entlang den ursprünglichen Korngrenzen.

     

Sedimentation of submarine fan deposits in the Pindos foreland basin,from late Eocene to early Oligocene,west Peloponnesus peninsula,SW Greece

Turbidite facies distribution and palaeocurrent analysis of submarine fan evolution in the Pindos foreland basin of west Peloponnesus peninsula (SW Greece) indicate that this part of the foreland was developed during Late Eocene to Early Oligocene in three linear sub‐basins (Tritea, Hrisovitsi and Finikounda). The basin fill conditions, with a multiple feeder system, which is characterized by axial transport of sediments and asymmetric stratigraphic thickness of the studied sediments, indicate that the Pindos Foreland Basin in this area was an underfilled foreland basin. Sediments are dominated by conglomerates, sandstones and mudstones. The flow types that controlled the depositional processes of the submarine fans were grain flows, debris flows and low‐ and high‐density turbidity currents. The sedimentary model that we propose for the depositional mechanisms and geometrical distribution of the turbidite units in the Tritea sub‐basin is a mixed sand‐mud submarine fan with a sequential interaction of progradation and retrogradation for the submarine fan development and shows a WNW main palaeocurrent direction. The Hrisovitsi sub‐basin turbidite system characterized by small‐scale channels was sediment starved, and the erosion during deposition was greater than the two other studied areas, indicating a more restricted basin topography with a NW main palaeocurrent direction. The Finikounda sub‐basin exhibits sand‐rich submarine fans, is characterized by the presence of distinct, small‐scale, thickening‐upward cycles and by the covering of a distal fan by a proximal fan. It was constructed under the simultaneous interaction of progradation and aggradation, where the main palaeocurrent direction was from NNW to SSE. Copyright © 2012 John Wiley & Sons, Ltd.     

A late Precambrian tidal shelf deposit, the Lower Sandfjord Formation, Finnmark, North Norway

The Lower Sandfjord Formation is a 1.5 km thick late Precambrian sandstone. It is a remarkably homogeneous unit consisting largely (98%) of cross-bedded, texturally and mineralogically mature, coarse or medium sandstone, and is interpreted as a shallow marine deposit. This interpretation is based on the maturity, the exclusively tabular bed geometry, occasional sets of herring-bone cross-bedding and most importantly, the abundance of sheet-like pebble layers only 1–5 grain diameters thick and sometimes overlain by thin siltstone drapes. Various different types of compound cross-bedding, all of which show evidence of reversing currents, are interpreted as sub-tidal sandwaves. These sets range in thickness from 0.5 to 14 m, and in conjunction with the overall abundance of cross-bedding probably indicate strong tidal currents. A tide-dominated current regime is also considered essential to explain the derivation of such large quantities of sand from the contemporary coasts. It is suggested that sand transport offshore took place during the erosional transgression of abandoned delta lobes. However, the predominance of a single, easterly, mode in the palaeocurrent patterns suggests that the tidal currents were reinforced by some other current system. The predominantly unimodal palaeocurrent patterns and the coarse, sand-rich nature of the succession, taken together with the thickness do not superficially seem likely characteristics for a shallow marine sequence. Nevertheless this study appears to demonstrate that such deposits were formed on tidal shelves in at least late Precambrian time.     

Sedimentation and water escape structures in some late Precambrian shallow marine sandstones from Finnmark, North Norway

Water escape structures are abundant in the Grønnes Formation, a tectonically undeformed, late Precambrian shallow marine sandstone deposit in North Norway. Trough cross-bedded sandstones of the current-dominated shallow marine environment were frequently liquefied, presumably due to recurring seismic shocks. Subsequent dewatering resulted in deformation of the cross-bedding and the formation of convolute lamination. A three-fold upward vertical sequence developed where liquefaction occurred below the sediment-water interface: convoluted bed → passively deformed bed → undeformed bed. The passively deformed bed resulted from differential subsidence of a relatively plastic bed above a liquefied bed. It is characterized by anticlinal ridges and sand volcanoes at the sites of vertical sediment extrusion, and synclinal troughs at the sites of lateral sediment movement. Liquefaction may have been induced by either tectonic (earthquake shocks) or non-tectonic (storm-induced microseisms) trigger mechanisms, or a combination of both. The restriction of such a high frequency of water escape structures to deposits immediately above a gentle regional unconformity lends support for a tectonic trigger mechanism.     

辽宁陆东凹陷前河油田水下扇沉积粒度特征及水流强度分析

前河油田九佛堂组为一套水下扇沉积。通过对不同层位取心井粒度资料分析及对比,分析其差异的原因,确定各层位搬运方式及沉积作用形式,并运用霍姆斯水流强度图分析从湖盆边缘向湖盆内的水流强度变化。根据岩性组合及测井曲线特征,识别出扇根、扇中前缘及扇端3种微相。并认为沿水流及砂体发育方向为部署有利区带。     

Coarse-grained submarine fan and slope apron deposits in a Cretaceous back-arc basin, Antarctica

The Cretaceous of west James Ross Island, Antarctica represents the proximal fill of a late Mesozoic back-arc basin that was probably initiated by oblique extension during the early development of the Weddell Sea. The succession records sedimentation in two contrasting depositional systems: a laterally persistent slope apron flanking the faulted basin margin interrupted both spatially and temporally by coarse-grained submarine fans. Slope apron deposits are dominated by thinly interbedded turbiditic sandstones and mudstones (mudstone association), interspersed with non-channelized chaotic boulder beds, intraformational slump sheets and isolated exotic blocks representing a spectrum of mass-flow processes from debris flow to submarine gliding. Localized sand-rich sequences (sandstone-breccia association) represent sandy debris lobes at the mouths of active slope chutes. The submarine fan sediments (conglomerate association) are typified by coarse conglomerates and pebbly sandstones, interpreted as the deposits of high-density turbidity currents and non-cohesive debris flows. Three assemblages are recognized and are suggested to represent components of the inner channelled zone of coarse-grained submarine fans, from major fan channels through ephemeral, marginal channels or terraces to levee or interchannel environments. The occurrence of both slope apron and submarine fan depositional systems during the Early and Mid-Cretaceous is attributed to localized input of coarse arc-derived sediment along a tectonically active basin margin. Periods of extensive fan development were probably linked to regional tectonic uplift and rejuvenation of the arc source region; cyclicity within individual fan sequences is attributed to migration or switching of fan channels or canyons. Slope apron sedimentation was controlled largely by intrabasinal tectonics. Local unconformities and packets of amalgamated slide sheets and debris flow deposits probably reflect episodic movement on basin margin faults. Differential subsidence across the basin margin anchored the basin slope for at least 20 Myr and precluded basinward progradation of shallow marine environments.     

Modern pollen spectra from lake sediments in Finland and Finnmark, north Norway

Absolute (APF) and relative surface pollen spectra from 67 moderate-sized lakes in Finland and Finnmark are presented as pollen diagrams and isopoll maps and analysed by multidimensional scaling. The results are applicable to problems of regional vegetational history through comparisons of pollen spectra and the use of R-values. It is shown that relative spectra can discriminate the major vegetational regions. APFs give better resolution among northern forest regions and low APFs characterize tundra. Gradients of tree-pollen percentages in south and central Finland are related quantitatively to the major forest gradients, which are azonal, mainly related to soils, and affected but not obscured by human influence. Forest clearance is reflected in frequencies of various non-tree pollen types. Non-tree pollen and spores also provide vegetational and climatic information in the far north.     

Structures associated with superimposed inhomogenous shearing of basic dykes from Finnmark, Norway

Metadolerites within the Olderfjord Nappe of the Kalak Nappe Complex of North Norway show a wide range of structural relationships. During D₂ simple shear rotated the dykes from an initially orthogonal relationship towards parallelism with the sedimentary layering and boudinaged those dykes that rotated to within 25° of the sedimentary layering. During D₃ dykes which had been rotated to within 5° of the layering were folded; those lying between 5° and 25° were boudinaged whilst those at angles between 25° and 75° had folds developed against their margins. At higher angles of discordance little evidence of D₂ or D₃ deformation has been observed.In other thrust sheets within the Kalak Nappe Complex metabasites have generally been sheared into parallelism with the compositional banding. By comparison with the Olderfjord Nappe the average D₂ shear strain within the Kalak Nappe Complex ranges between 5 and 10. The anomalous preservation of high angle discordant relationships in the Olderfjord Nappe reflects the preservation of a large scale low-strain block (mega-boudin) within the nappe; samples taken from the mega-boudin are more suitable for geochemical analysis for tectonic setting discrimination.     

浊流沉积研究的新进展:鲍马序列、海底扇的重新审视

本文在总结前人对浊流沉积研究的基础上,分析前人对浊流与浊积岩、浊流沉积与浊流相模式的对应关系之间的认识,并对鲍马序列进行重新审视。在海底扇研究过程中,鲍马序列已经不能充分反映浊流沉积的全过程。鲍马序列所反应的沉积模式其实是由碎屑流、浊流、底流等多种形式流体组合和改造后的结果,海底扇沉积模式不能笼统归结为浊流沉积作用的结果。在完善重力流、底流等沉积作用的同时,建立一个与沉积作用相互联系的深海沉积系统,以对深海研究提供更好地指导和预测。