Mineralogy and Geochemistry of Shales from the Late Jurassic-Early Cretaceous Transition

NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 65

Fine-grained epicontinental Arctic sedimentation – mineralogy and geochemistry of shales from the Late Jurassic-Early Cretaceous transition

Henning Dypvik & Victor Zakharov

Dypvik, H. & Zakharov, V.: Late Jurassic-Early Cretaceous fine-grained epicontinental Arctic sedimentation – mineralogy and geochemistry of shales ­from the Late Jurassic-Early Cretaceous transition. Norwegian Journal of Geology, Vol 92, pp. 65-87. Trondheim 2012, ISSN 029-196X.

Late Jurassic and Early Cretaceous fine-grained siliciclastic formations from key Arctic localities have been analysed. In this study their mineral­ ogical and geochemical (major, trace, REE elements) affinities have been compared and put into a sedimentological context. Compared to other regions the studied sections represent more ventilated and less anoxic conditions than other Late Jurassic black shale formations. The overall mineralogical­ and geochemical composition is rather similar in the studied sections. This homogeneous appearance reflects the well-developed circulation of the shallow epicontinental sea of the region. The suspended material was repeatedly homogenised before final deposition and appears today to be relatively similar in composition over this wide area. In contrast, a basaltic source rock component (Siberian Traps?) is evident in the Siberian section (Nordvik). On large parts of the sea floor anoxic conditions prevailed, and in the Nordvik region this, in combination with slow and very fine-grained clastic sedimentation and high algal production, resulted in the formation of phosphate concretions.

Henning Dypvik, Department of Geosciences, University of Oslo, P.O.Box 1047, Blindern, NO 0316 Oslo, Norway. E-mail: [email protected]. no; Victor Zakharov, Geological Institute, Russian Academy of Sciences. Pyzhevskij 7, Moscow, 109017 Russia. E-mail: [email protected]

Introduction consisted of three Siberian branches which were sepa- rated by the Urals, the Novaya Zemlya islands and Tai- The Late Jurassic epicontinental sea covered large parts myr Island (Zakharov et al. 2002). These depositional of the present Arctic basin. In this paper, field sections basins are presently named the Barents Sea Basin, West of shale from the remote Nordvik area (North Siberian Siberian Basin and North Siberian Basin, where Nordvik Basin) will be compared with a composite of selected, is located (Figs. 2, 3a and 3b). The widespread fauna was more closely spaced locations from the Barents Sea dominated by, e.g., stenohaline molluscs, brachiopods, region (North Greenland, Svalbard and the southern foraminifers, radiolarians and dinoflagellates with high Barents Sea drillcore 7018/05-U-01) (Figs. 1 and 2). taxonomic diversity. Such fauna could only be kept in The aim is mainly to disclose compositional similari- balance in very large masses of water, of relatively stable ties or differences in order to shed light on basinal devel- salinities and temperatures (Zakharov et al. 2002). opments along with variations in weathering, sedimen- tation, geometry and tectonics of the area (Figs. 2, 3a Dypvik (1992), Zakharov et al. (1998) and Mørk & and 3b). The search for possible geochemical signals of Smelror (2001) demonstrated several eustatic, sequence- the Late Jurassic Mjølnir impact has also been an issue stratigraphic signals in the Jurassic and Lower Cretaceous ­ (Zakharov et al. 1993; Dypvik, et al. 1996; Dypvik and successions, important controlling factors in the sedi- Zakharov 2010). mentation of the Arctic basins at that time. During this period, sedimentation in the Siberian basins took place Geological background information in a wide range of environments; from alluvial plains and lacustrine swamps in Early and Mid Jurassic time Overview and into open marine conditions in the Late Jurassic and The Jurassic to Cretaceous transition can be fairly well Early Cretaceous (Shurygin et al. 2000). The Lower and correlated in the area, forming the natural stratigraphical Middle Jurassic formations of Western Siberia are domi- base of this study (Figs. 3a and 3b). nated by sandy horizons with interlayered beds of clay- stone and shale. The number of marine beds generally The Mesozoic successions of the North Greenland, Sval- increases from south to north, and in the Upper Jurassic­ bard, Barents Sea, Kara Sea and Siberian Arctic represent sections marine claystones dominate in the region. A few the wide epicontinental paleo-Arctic sea. This seaway glauconitic sands are found dispersed in the lower part 66 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Figure 1. Map of the present- day Arctic. The 7018/05-U- 01 locality is represented by a shallow core, the Svalbard sample comes from the Janus- fjellet section, whilst the North Greenland localities are a = East Peary land and b= Kilen. The Mjølnir impact structure (star) is also marked on the map.

a North Greenland b Nordvik

Svalbard

Mjølnir 7018/05-U-01

150 Ma (Kimmeridgian-Volgian) Figure 2. A simplified Late (absolute frame) 150 Ma (Kimmeridgian-Volgian)Jurassic paleogeography of (absolute theframe) Arctic, based on the plate reconstructions of Lawver

v v v v et al. (1990). Arrow along v7 v v v v the North Greenland paleo- NORTH SIBERIAN BASIN v v v v Figure 1 7 coastline shows the major Nordvik v v v v v v v vv v v v v NORTH SIBERIANDypvik BASIN and Zakharov, 2011 coast-parallel current trans- v Nordvikv v v v vv v v v v v v v Taimyr port direction measured v v v v v v v v v Taimyr (towards SE). Possible tidal v v v channel transportation direc- tions towards the south have been measured at right angles WEST SI BERI AN BASI N to this. Same locations as in WEST SI BERI AN BASI N Figure 1. Novya Zemlya Ural Novya Zemlya Ural Svalbard BARENTS SEA BASI N Svalbard Mjølnir a BARENTS SEA BASI N b Mjølnir a North Greenland 7018/05-U-01 b

North Greenland 7018/05-U-01 Mjølnir impact structure Land Mjølnir impact structure Scandinavia Land Volcanics/ Scandinavia volc. clastics Volcanics/ v v v v Siberian traps volc. clastics Marine/ Lagoonal/v v v v Siberian traps Shallow marine Marine/ Lagoonal/ Shallow marine NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 67

a STAGES NORTH GREENLAND SVALBARD BARENTS SHELF NORTH SIBERIA

East Peary Land Kilen Central Spitsbergen Bjarmeland Platform Nordvik C ? ? Albian Kap Rigsdagen Gåseslette R beds Group ? ? E Aptian L Caroline ellet a Formation T d Kolmule A e Formation Barremian g ? Helvetia ellet C å ? Galadriel Formation r Fjeld E Hauterivian R Ullaberget Kolje d Formation u Member Formation s O Lichen Ryg r Valanginian å Sand- Formation i Klipp- Knurr U e k Wiman - sk Fm. Fm. stone ellet Rya- n Member Dromledome f. S Formation Member Berri- zan- ian F Fm. H Paksa asian e < < < < < < < < < < < < < < < < < < < < < < < < Formation o Kuglelejet k r Formation A Slottsmøya Krill J k Tithon- Volg- m Splitbæk g Member i a n Member U ian ian a Formation t r g Birkelund d Oppdal- e i R Kimmeridgian Fjeld h såta Mb. n o Formation f. A n Lardy- F Alge ? Member Oxfordian F ellet Mb. m. S o Callovian r Oppdalen S m. Member Fuglen Formation I Bathonian Kapp Toscana C Group b Figure 3a Dypvik and Zakharov, 2011 9 2008) w

unschensis .

Figure 3a and 3b. 3a. Stratigraphic comparison figure with correlations between the N.Greenland, Svalbard, Barents Sea and East Siberian Basin - Nordvik stratigraphy. General lithological information is presented in standard signatures, while the thick black lines show sample levels. 3b. Correlation chart of the zonal successions around the Jurassic-Cretaceous boundary of Nordvik and Svalbard.Figure Not 3bto scale. Dypvik & Zakharov 2011

of the Upper Jurassic formations. In latest Jurassic time, It should be noted that the studied Jurassic and turbidites were deposited in the prodeltaic and deeper Cretaceous­ basins of North Greenland, Svalbard and the offshore regions of western and northern Siberia. The Barents Sea are rather closely located compared to the marine shelf sedimentation continued into the earliest Nordvik section. They were highly influenced by their Cretaceous. proximity to the tectonically active regions along the 68 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY neighbouring plate boundaries towards the Mohns and Oxfordian, black, silty claystones with carbonate con- Knipovich ridges in the south and west, in addition to cretions and an overall apparent thickness of 11 m. The the eustatic sea- level changes at the time (Lawver et al. rocks contain abundant pyrite nodules and glauconitic 1990; Faleide et al. 1993). grains. Taphocoenoses of bivalves show signs of both autochthonous and allochthonous burial, suggesting sed- Siberia imentation within the storm-wave zone. The well-known Bazhenov Formation of Western Sibe- ria is of Volgian (Tithonian) to Berriasian age, and made In the Nordvik Peninsula, Kimmeridgian overlies the up of black to brown, organic-rich shales (Vyshemirsky Oxfordian section at a sharp but conformable contact. 1986; Gavshin & Zakharov 1996a; 1996b). This confined The Kimmeridgian is represented by dark grey, silty clay- 5-6 million year period of dark grey, black to dark brown, stones with grains of glauconite and chlorite ; the over- organic-rich clay sedimentation is commonly repre- all thickness is 32 m. The middle part of the Kimmeridg- sented by 25 to 30 m-thick beds, which vary between 10 ian beds enclose carbonate concretions up to 1 m across. and 60 m in thickness. This famous petroleum source Macrofossils are dominated by rostra of belemnites. rock covers more than 1 mill km2, is normally buried Ammonites and bivalves are scarce in these lower sub- beneath 2000 to 3000 m of younger sediments and con- littoral sediments. In the Kheta River basin, the Upper tains on average 8 % TOC (Gavshin & Zakharov, 1996b), Oxfordian and Lower Kimmeridgian deposits are litho- typically with type II organic matter (Kontorovich et al., logically similar, with a gradual internal transition (Saks 1997). It can be correlated with formations outside the 1969; Zakharov et al. 1983). basin that contain a different quality of organic matter, e.g., the Hekkingen Formation of the Barents Sea and the In both the Nordvik Peninsula and the Kheta basin, Vol- Paksa Formation of the Nordvik area, which are studied gian deposits unconformably overlie the Kimmeridgian here (Figs. 2, 3a and 3b) (Shurygin et al. 2000). beds. The break was also recorded in the Pechora River basin, West Siberia, Lower Yenisei depression, and lower The most complete exposures of the Upper Jurassic and Lena basin (Mesezhnikov 1983). In the Nordvik sec- Lower Cretaceous successions are located on the Nord- tion, the entire Lower Volgian substage and a large part vik Peninsula and in the Kheta River basin, representing of the Middle Volgian substage are missing (Figs. 3a and coeval deposits of different depositional environments 3b). Stratigraphically above a well-developed succession (Saks 1969; Zakharov et al. 1983) (Figs.1, 2 and 4). From of ammonitic zones related to parts of the Middle Vol- the Late Jurassic to Valanginian, the Nordvik region rep- gian and Upper Volgian substages, Ryazanian/Berriasian, resented the central parts of the basin (Fig. 4). The Kheta Lower Valanginian and parts of Lower Hauterivian beds River section, in contrast, was located proximal to the old are present (Figs. 3a, 3b and 5). In northern Russia the paleo-shoreline (Zakharov & Yudovny 1974). overlying Hauterivian are of continental origin.

The oldest deposits of the Nordvik Peninsula (the Volgian and Lower Valanginian deposits constitute Urdyuk-Khaya Cape Formation) are Middle - Upper the Paksa Formation (Figs. 3a, 3b, 5 and 6), which is

Figure 4. Distribution of marine facies at Jurassic­-Cretaceous boundary time at the Northern Siberian­ sea region. Land in yellow colour. Roman numerals – sublittoral marine facies marked in blue colours; I – Lower (relative deep water), II – Middle (modera- tely deep water), III – Upper (relatively shal- low water). The samples in this study come from site marked star. B. Nikitenko­ (pers. comm. 2012). NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 69 composed of alternating dark grey and brown mud- dark-grey shales and sandstones of Kimmeridgian to stones and bluish-grey massive claystones with numer- Aptian age (Birkelund Fjeld, Splitbæk, Kuglelejet, Drom- ous interbeds of phosphate/carbonate concretions. The ledome, Lichen Ryg and Galadriel Fjeld formations). The total thickness of the Paksa Formation is 137.5 m with lowermost 40 m of the shallow-marine Kuglelejet For- the TOC contents of the Middle Volgian through Middle mation is made up of several 5 to 20 m-thick, coarsen- Ryazanian/Berriasian interval varying from 1.0 to 3.5%. ing-upwards successions, whereas the uppermost, more The TOC values drop to an average of about 0.5% in the fine-grained, 50 metres of the formation are composed siltier Upper Ryazanian/Berriasian and Lower Valangin- of 1-2 m-thick, coarsening-upwards intervals. The cen- ian beds (Zakharov & Yudovnyi 1974). tral part of the Kuglelejet Formation (level 125 m in Fig. 7) comprises several cross-stratified, channellised beds in In the Kheta Basin (Fig. 4), Volgian sediments over- a 6 m-thick unit, exhibiting well-developed southeasterly lie Kimmerigian successions with an erosional contact, paleo-current directions (Fig. 2). The common erosional and two Lower Volgian zones are missing. The Volgian bases carry grains of glauconite in lag conglomerates. beds are lithologically heterogeneous and the upper zone The dark grey to black, marine shales of the succeeding (Pectinatites­ pectinatus) of the Lower Volgian Substage Dromledome Formation (70 m in thickness) show only is represented by 2.3 m of sandy siltstones. It is only the faint bioturbation, but a few traces of Zoophycos have upper zone (Epivirgatites variabilis) of the Middle Vol- been observed. This offshore formation contains Buchia gian Substage that is present (thickness 4.5 m) and it is and normally comprises parallel-laminated shales. The composed of glauconitic-chloritic siltstones with phos- uppermost part is composed of a 2.5 m-thick, fine, mica- phoritic nodules. Thus, the stratigraphic gap embraces ceous sandstone bed with well-developed hummocky four ammonitic zones. In the Kheta Basin the Upper Vol- cross-stratification. The Dromeldome Formation is gian Substage is represented by the zones of Craspedites overlain by the well-sorted, medium- to coarse-grained, okensis (with three subzones), C. taimyrensis and Cheta- light-grey sandstones of the 30 to 50 m-thick Lichen Ryg ites chetae. They constitute 50.5 m of transgressive silt- Formation (Figs. 3a and 7). stones (Zakharov & Yudovnyi 1974). The Ladegårdsåen Formation (>250 m thick) of East North Greenland Peary Land (Fig. 3a) is composed of shallow -marine The Mesozoic successions of the Greenland - Barents shales, siltstones and sandstones, dating from Mid Sea region are dominated by a siliciclastic sedimenta- Oxfordian to Early Cretaceous. In the lower part of the tion of sand, silt and clay. During the Jurassic and Cre- formation, well bedded to parallel-laminated, dark-grey taceous, clay and silt sedimentation dominated in the shales and shaly sandstones, commonly containing plant basinal areas, whilst sand deposition took place along fragments, form 10 to 30 cm- thick upward-coarsening the margins of the basin (Mørk et al. 1999; Dypvik et al. units (Dypvik et al. 2002). The silty and sandy shales in 1991a; 1991b; Dypvik et al. 2002) (Fig. 1). In Late Juras- the middle parts of the Ladegårdsåen Formation are suc- sic and earliest Cretaceous time, fine-grained sedimenta- ceeded by a very prominent, cemented, cross-stratified, tion in central parts of the epicontinental paleo-Barents light-grey, probably more than 100 m-thick sandstone Sea was sporadically disrupted by storm and storm-gen- unit of Valanginian age (Figs. 3a and 7) (Håkansson et al. erated currents, causing shifts from anoxic to hypoxic 1991; 1993). This sandstone may be correlated with the sea floor conditions. Such shale and siltstone dominated Lichen Ryg Formation of the Kilen sections. Glendon- lithologies today form the Hekkingen Formation (Fig. ites are commonly occurring in the Lower Cretaceous of 3a). In the marginal areas of the paleo-Arctic basin (e.g., North Greenland, but have so far not been reported from North Greenland), there were shallow-marine to deltaic comparable stratigraphical horizons in the other sites of environments of wave and tidally dominated settings this study. (Dypvik et al. 2002; Heinberg & Håkansson 1994; Wors- ley et al.1988; Leith et al. 1993; Mørk et al. 1999). Svalbard and the Barents Sea The uppermost Triassic and Lower Jurassic succession The key Jurassic and Cretaceous sedimentary succes- of Svalbard (upper part of the Kapp Toscana Group) sions of North Greenland are located in East Peary Land is dominated by shallow-marine sediments, depos- and Kilen (Figs. 1 and 2) (Håkansson et al. 1981; 1991; ited during a period of reduced clastic influx and sev- 1994; Heinberg & Håkansson 1994; Dypvik et al. 2002). eral stratigraphical breaks (Fig. 3a). These beds are suc- In both areas, Oxfordian / Kimmeridgian to Albian ceeded by the basal strata of the Janusfjellet Subgroup of deposits are present, but a formal stratigraphy has only the Adventdalen Group (the Agardhfjellet, Rurikfjellet, been established for the Kilen locality (Fig. 3a). Helvetiafjellet and Carolinefjellet formations) (Fig. 3a) showing initiation and advancement of the major Batho- In Kilen, the Mesozoic succession (>1500 m in thick- nian - Callovian transgression in the area (Bäckström & ness) has a Late Oxfordian to Early Kimmeridgian base, Nagy 1985, Nagy et al. 1990). The transgressive devel- and the succession is more continuous than in East opment continued well into the Oxfordian, as reflected Peary Land (Figs. 1, 2 and 3a). The lowermost 350 m of in the lithological transition from the widespread, basal the Kilen succession is made up of highly bioturbated, phosphatic conglomerate of the Brentskardhaugen Bed 70 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY to the succeeding black, organic-rich, finely laminated dominated, especially during deposition of the Hekkin- shales of the Lardyfjellet Member of the Agardhfjellet gen Formation, which can be correlated with the Agard- Formation (Dypvik et al. 1991a; 1991b). In Late Oxford- hfjellet Formation on Svalbard (Mørk et al. 1999; Dypvik ian / Early Kimmeridgian time, a transgressive develop- et al. 2006; Smelror & Dypvik 2006; Smelror et al. 2001). ment can be seen in the black, organic-rich claystone on The Hekkingen Formation has been subdivided into Svalbard and in the Barents Sea (Hekkingen Fm.) (Fig. Alge and Krill members (Fig. 3a). The organic-rich Alge 3a). A comparable transgressive development is repre- Member forms its lower part and is characterised by sented in the Jurassic shallow-marine sandstones (Lade- high gamma kicks and black, paper shales. The overly- gårdsåen and Birkelund Fjeld formations) of the North ing Krill Member contains greyish-coloured shales with Greenland localities. This configuration, with a shallow- some few carbonate beds. The Krill Member represents water, sandstone-dominated setting in North Greenland more ventilated, open marine conditions compared to and a more fine-grained, basinal setting in Svalbard, con- the restricted conditions of the Alge Member below. tinued into the Kimmeridgian (Fig. 3a). Open marine sedimentation continued into the Early Svalbard and Barents Sea depositional conditions were Cretaceous in the Barents Sea, as seen in the Knurr For- dominated by anoxic to hypoxic sedimentation dur- mation. The greyish mudstones of the Knurr Forma- ing the Oxfordian and Kimmeridgian (Lardyfjellet, tion form the basinal setting with the time-equivalent Oppdalsåta and Slottsmøya members) (Dypvik 1980; carbonate platform deposits of the Klippfisk Formation 1985; Nagy et al. 1988; 1990). Periods with high wind (Mørk et al. 1999). The Jurassic and Cretaceous Barents and storm activity and deposition of offshore sand bars Sea succession is made up of deep- to shallow-marine locally disrupted the sedimentation of organic-rich clays shelf deposits (Mørk et al. 1999). (the Upper Kimmeridgian-Lower Volgian Oppdalsåta Member) (Dypvik et al. 1991a). Generally North-north- westward-directed storms reworked the prodeltaic and Samples and methods shelf deposits, which originally were fed from the north (Dypvik et al. 1991b; 1992), creating widespread offshore The outcrop samples from Nordvik, Svalbard and North bars and sublittoral sheet sands. Greenland were from 200 to 500 g in size and taken from fresh outcrops, whereas the core samples of the 5 The upward-coarsening development of the Slottsmøya cm-diameter Barents Sea core (7018/05-U-01) weighed Member culminates at the contact between the Agard- about 20 - 40 g. hfjellet and Rurikfjellet formations, marked by the so- called Myklegardfjellet Bed. The base of this bed repre- Four shale samples from the 18 m-thick section of the sents a transgressive surface, possibly correlative with the Paksa Formation of Nordvik, Siberia, have been ana­ contact between the Kuglelejet and Dromledome forma- lysed (Figs. 3a, 5 and 6). Three of the four, dark-grey tions of North Greenland (Dypvik et al. 2002). shale samples are located at level 12.10-13.20 m and one at level 0.25 m. In the related concretion study (Dypvik After a maximum transgressive phase at about the Ryaza- & Zakharov 2010), 42 samples from 7 concretions (phos- nian - Valanginian transition (Wimanfjellet Mb.), an phate/carbonate) have been analysed mineralogically upwards-shallowing, regressive development took place and geochemically. during Valanginian and Hauterivian times (Fig.3a). Fifteen shale samples from North Greenland (Drom- The progradational deltaic developments in the Svalbard ledome Formation at Kilen and Ladegårdsåen Forma- region terminated in the Barremian, with the deposi- tion at East Peary Land) (Figs. 3a and 7) and 11 samples tion of the up to 30 m-thick, coarse-grained, fluviodeltaic from the Janusfjellet section on Svalbard (Slottsmøya Festningen Sandstone Member of the Helvetiafjellet For- Member, Agardhfjellet Formation) (Fig. 3a) have been mation (Major & Nagy 1972; Edwards 1976; Steel 1977; analysed. Fourteen samples from drillcore 7018/05-U- Steel et al. 1981; Nemec et al. 1988; Nemec 1992; Gjelberg 01 (IKU, SINTEF Petroleum Research) (the Krill Mem- & Steel 1995). ber of the Hekkingen Formation) (Fig. 3a) were analysed from the Barents Sea. The North Greenland shales have Compared to these published profiles from Svalbard, the a more silty/sandy composition compared to those from Jurassic Barents Sea sections generally show more dis- Svalbard and the Barents Sea , but they are all classified tal, open marine conditions, dominated by fine-grained as grey to black shales. Stratigraphical, mineralogical clastic sedimentation. The Adventdalen Group of the and geochemical developments of the Svalbard, North Barents Sea consists in its lowermost part of shales with Greenland and Barents Sea sections have been described dispersed thin limestones and sandstones (Fuglen and elsewhere (Dypvik et al. 1992; Dypvik et al. 2002; Dypvik Hekkingen formations) ( Fig. 3a). The dark-brown to et al. 2004). The mineralogy and TOC values from Sval- black shales represent marine shelf conditions, with the bard (Janusfjellet section) were determined by Kalleson thickest sedimentary successions towards the southern (1998). parts of the basin. Partly anoxic to dysoxic conditions NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 71

Sc, Be, Co, Ga = 1 ppm; Sr, Y, Rb = 2 ppm; Ba = 3 ppm; Zr = 4 ppm; V, As = 5 ppm; Cu = 10 ppm; Cr, Ni = 20 ppm; Zn = 30 ppm

La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb =0.1 ppm; Lu = 0.04; Pr, Eu, Tm = 0.05 The shales and phosphates were studied in thin-section and by SEM before being crushed and analysed by XRD and by ICP-MS.

The samples have been run through standard correla- tion programs, and the main results are shown in Table 5. Due to the restricted number of samples from each locality, factor analysis and principal component ana­ lysis were evaluated to be of limited importance and were consequently not performed. Evolutinella emeljanzev Evolutinella emeljanzev

phosphate/ phosphate/ micritic phosphatelayer calcite micritic phosphatelayer calcite Figure 5. The detailed stratigraphical section of the Jurassic- Cretaceous ­boundary beds (Paksa Formation) on the Nordvik peninsula (Urdyuk-Khaya cape), Laptev Sea. The succession repre- sents relatively deep-water, marine environments.

FigureFigure 5 5 DypvikDypvik and and Zakharov, Zakharov, 2011 2011 The samples have texturally and mineralogically been analysed in thin-section (15 to 30 µm-thick slides) and by X-ray diffraction. The X-ray diffraction analyses (XRD) were executed on rock powder samples on a Phil- ips X’Pert system at the University of Oslo, with detec- tion limits of about 5%. The values presented in Table 1 are semi-quantitative XRD % , calculated from the peak area of the main peaks in the X-ray diffractograms and should not be confused with real concentrations. The clay mineralogical analyses were done according to the standard methods of Carrol (1970); untreated, ethylene glycolation, heating to 550 °C and slow scan across the 3.55 Å area, in order to separate the smectitic, chloritic and kaolinitic components.

The geochemical analyses (Tables 2, 3, and 4) have been performed at Activation Laboratories LTD (ACT LAB, Canada) by their programs Element Fusion ICP-MS by (Code 4LITHO (11+) Major Elements Fusion ICP (WRA)/Trace Elements Fusion ICP/MS (WRA4B2). ACT LAB runs routinely 20 international rock standards for quality control. The following detection limits are valid for the geochemical analyses:

SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, P2O5, LOI Figure 6. Photograph of the studied section (Paksa Formation) (loss of ignition) = 0.01 % at Nordvik, showing the common appearance of black shales and

; MnO, TiO2 = 0.001 % phosphatic/carbonate concretionary beds. 72 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Table 1: X-ray diffraction analyses of shales from Nordvik, Svalbard, North Greenland and the Barents Sea. The mineral values given represent semiquantitative calculations of peak counts from X-ray diffractograms. Svalbard values from Kalleson (1998). Region Sample 14Å % 12Å % 10Å % 7Å % 4,26Å % 3,24Å % 3,18Å % 3,03Å % 2,89Å % 2,79Å % 2,71Å % Sum

113130 0 0 3 5 81 8 2 1 0 0 0 100

113131 0 0 4 5 78 9 0 2 0 2 0 100

North Greenland 113132 0 3 5 9 66 14 0 0 0 3 0 100

113133 0 1 3 4 81 8 3 0 0 0 0 100

113134 0 0 0 2 82 11 0 5 0 0 0 100 113064 3 2 10 4 57 4 9 6 3 2 0 100 113068 2 2 5 2 15 0 2 13 0 57 2 100 113072 4 1 20 9 47 5 10 0 0 4 0 100 113077 4 3 13 6 48 7 10 0 0 5 4 100 113082 4 4 22 6 38 4 8 3 4 3 4 100 113087 5 3 23 8 37 5 9 3 0 4 3 100 113092 3 2 15 7 53 4 12 0 0 4 0 100 113098 3 2 17 6 49 4 8 0 0 7 4 100 113100 0 0 15 7 54 8 12 0 0 4 0 100 113101 0 0 9 5 67 4 12 0 0 3 0 100

Svalbard JAN-96-72 3 5 8 4 53 7 12 2 2 3 0 100 JAN-96-75 1 1 1 1 4 0 1 0 3 84 4 100 JAN-96-77 3 5 7 3 56 6 11 3 0 6 1 100 JAN-96-79 0 0 0 0 4 0 1 93 1 0 1 100 JAN-96-80 2 4 6 4 53 6 11 9 1 4 0 100 JAN-96-84 3 5 7 7 57 5 11 2 0 2 0 100 JAN-96-88 3 4 5 4 57 6 15 2 1 3 0 100 JAN-96-92 2 4 5 6 52 5 9 1 2 11 3 100 JAN-96-98 2 5 7 7 50 5 9 8 2 2 4 100 JAN-96-100 3 6 8 6 48 7 12 4 0 5 0 100 JAN-96-104 3 3 6 5 52 4 10 1 0 10 5 100

Barents Sea Well 79 2 4 16 7 37 12 8 0 1 3 10 100 ”7018” 84 1 5 15 10 37 9 5 0 5 3 11 100 86,25 2 6 17 9 31 8 10 0 2 7 9 100 87,33 1 7 11 8 28 6 8 1 2 12 15 100 87,58 1 6 14 7 29 8 4 1 1 13 15 100 87,93 1 5 15 11 39 11 5 0 2 3 8 100 88 1 6 14 12 32 10 10 0 2 4 9 100 88,22 1 7 11 6 32 10 4 1 15 3 9 100 89 2 6 8 7 34 7 2 0 3 13 20 100 89,25 1 5 10 8 35 9 3 0 3 6 19 100 90,05 1 5 11 10 29 13 6 1 3 8 13 100 91,5 1 3 10 9 20 8 6 1 22 16 4 100 97,5 2 3 8 5 35 7 8 0 4 15 12 100 100,63 2 4 11 9 40 8 9 0 4 4 8 100

Nordvik shale NV0.25 14 7 8 6 28 0 30 2 0 0 5 100 samples NV12.10 15 5 4 5 32 0 32 1 0 0 8 100 NV12.60 11 2 5 6 24 0 36 0 0 0 16 100 NV13.20 18 7 6 5 17 0 38 4 0 0 5 100 NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 73

Figure 7. The lithological section at Kilen con- sists of alternating black shales and sandstones. Kilen A photograph of the typical black shales of the Dromledome Formation of Kilen is shown next to the measured section. 550

500

450

400

350 Galadriel Fjeld Fm.

300

250 Ryg Lichen

200 Fm. Dromledome

150 Fm. upper

100 lower Kuglelejet Split -bæk 50

Birkelund Fjeld Fm. 0 metre c ss

Results and discussion and chlorite contents distinguish these shales from the studied­ sections ­in western Arctic (North Greenland, Mineralogy Svalbard and Barents Sea).

The Nordvik section In the black shale succession (18 m in thickness) of the The analysed Nordvik shales are very finegrained, well- Nordvik section, 5 to 12 cm-thick, more or less continu­ laminated and contain pellets, and some few dispersed ous concretionary beds of phosphates and carbonates are grains of glauconite were seen in thin-section. They con- present (Figs. 3a and 6). Zakharov et al. (1993) identi­ tain fewer coarser grains of quartz and feldspar as com- fied large Ir anomalies from one of these beds, which pared to the shales analysed from the western Arctic is located at the base of the Ryazanian; subsequently, (North Greenland, Svalbard and Barents Sea) (Fig. 8). Dypvik & Zacharov (2010) re-sampled and analysed The Nordvik shales, in addition, contain microsparitic these beds and surrounding shales but were not able to calcite, framboidal pyrite and clay minerals but are poor detect any Ir-enrichments. in apatite. North Greenland, Svalbard and Barents Sea samples The X-ray diffraction analyses (Table 1) show the The sampled localities from comparable stratigraphical four shale samples to be rich in quartz, plagioclase, beds in the western Arctic (North Greenland, Svalbard, mica and clay minerals (chlorite, mixed-layered smec- and Barents Sea) sections are relatively closely spaced tite-illite, illite and possibly some kaolinite), whilst compared to remote Nordvik and have partly been smaller amounts of calcite, pyrite and potash feld- described earlier (Kalleson 1998; Salvigsen 2004; Dypvik spar (< 1%) have been detected. The high plagioclase et al. 2006); consequently they will be mentioned only 74 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Figure 8. Photomicrographs (ordinary light) of shales from Siberia, Nordvik (#NV 025) and shales from western Arc- tic (North Greenland) (# NG 113082). The North Greenland sample is clearly more coarser grained and homogeneous, whe- reas the Siberian shale is very finely laminated and much finer grained .

briefly here . The samples are finely laminated shales, in analysed samples from the different sections (Table 5) some parts silty (grains of quartz and feldspar) with dis- (tables of correlation coefficients are available by con- persed framboidal pyrite, calcite and siderite. Only a few tacting the senior author). In the shales from the four traces of bioturbation are seen and the samples give an study areas, somewhat comparable associations appear; a overall laminated impression. They are generally coarser dominating clastic association (e.g. quartz, Si, Al) against grained than the Nordvik shales (Fig. 8). In the XRD some diagenetic (e.g., sulphides) and biogenic fractions analyses, the western Arctic shales are relatively rich (e.g., high LOI and calcite) is the general rule. Internal in quartz, contain moderate amounts of clay minerals variations are found within the clastic fractions, possi- (mica, chlorite, smectite, illite, smectite/illite mixed-lay- bly controlled by their clastic grain-size variations and ered and kaolinite) and plagioclase, and minor amounts related dilution effects. of potash feldspar and small amounts of calcite, dolo- mite, siderite and pyrite (Table 1). The clay minerals are In the most fine-grained samples (with only a minor dominated by illite and chlorite, and the quartz content is coarse fraction), quartz and clayminerals are associated higher and the feldspar amounts dramatically lower than with SiO2, Al2O3, Sc, Ba, V, Y, Zr, Cr, Ga, Rb, Nb, Cs, Ta, in the analysed Nordvik section. Hf, Ta, W, Tl, Th, U, Na2O, K2O, Ge, As and rare earth elements (REE). In sandy and silty shales the higher

Geochemistry quartz contents (SiO2) impose a dilution effect on the clastic clay minerals and feldspars, and consequently the The complete geochemical results of the analysed geochemical affinities appear differently in the coarse- shales are displayed in Tables 2, 3, 4, 5, 6 and 7. Here, and fine-grained fractions. only selected stratigraphical geochemical variations are presented, after the mineral- geochemical correla- In the carbonate fraction, calcite and siderite are nor- tions shown below. Student t-tests of the different sam- mally associated with CaO, Fe2O3, MgO, MnO, Sr, P2O5 ple groups (North Greenland, Svalbard, Barents Sea and and LOI (loss on ignition); calcite (CaO, Sr, LOI) and sid-

Nordvik) have been performed, but display no large geo- erite (Fe2O3, P2O5, MgO, MnO). chemical differences between the shales from the differ- ent localities. The coarser grained, quartz-rich, North Comparison of mineralogical composition and major Greenland shales, however, stand out in a few cases and trace elements within the different shale formations (t-test results are available by contacting the senior (North Greenland, Svalbard, Barents Sea, Nordvik) author). The shale formations of the Barents region (Figs. 9, Correlations 10, 11, 12, 13, 14 and 15) (North Greenland, Svalbard, Correlation coefficients have been determined for the Barents­ Sea) are dominated by quartz and clay minerals NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 75

Table 2: Major element analyses of shales from Nordvik, Svalbard, North Greenland and the Barents Sea. LOI= loss on ignition. TOC analyses for Svalbard, Barents Sea and Nordvik are presented; the North Greenland samples have not been analysed (na).

Region Sample SiO2 % Al2O3 % Fe2O3 % MnO % MgO % CaO % Na2O % K2O % TiO2 % P2O5 % LOI % Total % TOC %

113130 74.25 8.00 2.29 0.00 0.39 0.29 0.14 2.37 0.55 0.07 11.30 99.64 na

113131 70.80 9.50 2.09 0.00 0.48 0.13 0.12 2.78 0.68 0.06 13.22 99.86 na

North 113132 62.27 13.17 1.95 0.01 0.66 0.05 0.12 3.23 0.85 0.09 17.06 99.45 na Greenl­and 113133 75.28 9.20 1.80 0.00 0.39 0.06 0.10 2.59 0.59 0.05 8.85 98.91 na

113134 83.91 5.29 1.45 0.01 0.22 0.77 0.04 1.70 0.33 0.06 5.96 99.75 na 113064 68.64 14.19 4.69 0.02 1.01 0.29 0.41 3.35 0.84 0.10 5.89 99.44 na 113068 24.81 4.19 31.82 0.12 4.60 7.22 0.20 1.12 0.28 0.42 25.11 99.89 na 113072 72.03 13.95 2.73 0.01 1.19 0.26 0.50 3.41 0.83 0.07 4.79 99.76 na 113077 60.99 18.12 5.37 0.03 1.35 0.30 0.33 4.24 0.96 0.19 7.50 99.38 na 113082 60.94 16.93 7.01 0.03 1.29 0.42 0.41 3.90 0.88 0.20 7.88 99.89 na 113087 62.15 15.71 6.86 0.04 1.23 0.31 0.45 3.71 0.88 0.18 7.51 99.03 na 113092 65.00 13.87 5.39 0.03 1.12 0.63 0.47 2.86 0.86 0.16 8.59 98.98 na 113098 59.75 17.00 6.25 0.03 1.32 0.90 0.33 3.45 0.99 0.16 9.16 99.34 na 113100 62.04 16.01 5.34 0.02 0.86 0.21 0.34 3.20 1.02 0.17 10.73 99.95 na 113101 59.91 18.01 5.40 0.03 0.93 0.45 0.46 3.28 1.11 0.28 10.08 99.96 na

Svalbard JAN-96-72 58.68 18.19 5.46 0.01 1.66 0.19 0.47 3.88 0.89 0.08 10.54 100.00 1.84 JAN-96-75 14.66 5.05 36.17 0.14 7.19 5.22 0.16 1.01 0.25 1.37 28.23 99.46 0.4 JAN-96-77 58.98 16.48 6.53 0.02 1.66 0.20 0.64 3.54 0.87 0.09 10.23 99.23 0.59 JAN-96-79 14.70 3.73 1.80 0.02 1.84 41.68 0.18 0.88 0.17 0.33 34.15 99.50 0.2 JAN-96-80 59.02 17.31 6.21 0.01 1.52 0.30 0.63 3.61 0.87 0.08 10.20 99.76 0.4 JAN-96-84 58.84 16.38 8.03 0.01 1.75 0.14 0.39 3.31 0.85 0.10 9.80 99.60 0.72 JAN-96-88 60.78 16.00 5.95 0.01 1.63 0.11 0.45 3.43 0.83 0.09 9.66 98.95 0.83 JAN-96-92 55.53 16.14 9.44 0.06 2.30 0.36 0.42 3.08 0.71 0.06 10.64 98.72 0.78 JAN-96-98 55.79 17.46 5.77 0.02 1.75 0.49 0.35 3.27 0.74 0.13 13.98 99.75 4.1 JAN-96-100 55.25 16.07 7.12 0.01 1.42 0.15 0.60 3.33 0.73 0.11 14.46 99.24 3.15 JAN-96-104 50.45 14.24 14.38 0.04 1.85 0.84 0.30 2.95 0.61 0.10 13.81 99.58 0.51

Barents 79 53.65 15.40 5.13 0.02 1.82 0.44 1.06 3.59 0.68 0.17 17.64 99.60 5.43 Sea Well ”7018” 84 53.12 14.44 5.82 0.02 1.78 0.68 1.06 3.28 0.63 < 0.01 18.54 99.36 6.07 86,25 54.67 15.25 5.11 0.02 1.73 0.48 1.12 3.50 0.65 0.06 17.16 99.73 4.7 87,33 53.93 13.82 6.95 0.05 1.60 2.67 0.87 3.23 0.65 1.54 13.93 99.25 3.4 87,58 55.16 15.05 6.25 0.05 1.84 0.56 0.94 3.64 0.73 0.21 14.59 99.01 3.5 87,93 57.07 15.12 4.40 0.01 1.65 0.38 0.90 3.43 0.69 0.06 15.75 99.46 4.2 88 56.72 14.72 4.89 0.02 1.61 0.43 0.91 3.34 0.67 0.05 15.86 99.19 4.5 88,22 53.00 15.06 5.94 0.03 2.36 2.02 0.96 3.64 0.66 0.12 15.56 99.34 3.3 89 55.18 15.68 5.94 0.07 1.74 0.56 0.98 3.74 0.69 0.02 14.96 99.52 3.9 89,25 51.17 14.19 8.05 0.11 1.59 1.49 0.85 3.23 0.64 0.81 17.11 99.24 4.2 90,05 54.74 15.06 7.25 0.03 1.61 1.00 0.87 3.66 0.71 0.54 13.82 99.30 2.6 91,5 30.08 8.60 10.06 0.13 7.62 14.22 0.40 2.00 0.41 0.56 25.02 99.11 2.1 97,5 30.34 8.16 30.83 0.06 0.86 3.01 0.52 1.75 0.36 0.69 23.33 99.90 3.3 100,63 55.72 14.43 5.22 0.02 1.67 0.35 1.10 3.42 0.69 0.06 16.86 99.53 4.7

Nordvik NV0.25 48.62 18.50 9.30 0.03 2.45 1.07 1.65 2.53 1.09 0.35 13.54 99.13 3.64 shale samples NV12.10 46.32 16.02 12.68 0.03 2.52 0.51 1.27 2.58 0.82 0.18 16.15 99.07 3.49 NV12.60 54.36 18.81 7.32 0.03 2.96 0.33 1.41 3.03 1.07 0.11 9.94 99.36 0.99 NV13.20 24.73 8.49 29.76 0.31 5.72 2.66 0.71 1.44 0.42 0.23 24.60 99.06 3.72 76 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY U ppm 3,5 3,1 3,2 4,3 6 3,8 3,2 3,8 1,6 6,9 2,3 4,6 4 2,9 0,9 1,9 3,9 2,7 4,3 3 5,5 4,2 5,2 3,2 5,3 3,1 7,1 3 5,7 2,6 3 Th ppm 13 12,2 7,2 11,9 13,6 12,2 14,4 8 4,3 12 13,5 10 13,4 6,8 3,2 4 15,2 13,7 13,9 11 11,8 14,3 17,9 16,5 19,1 15,1 9,8 14,2 19,5 11,9 14,5 Pb ppm < 5 21 < 5 8 6 < 5 < 5 < 5 < 5 < 5 6 < 5 15 10 < 5 < 5 18 10 18 < 5 12 16 13 9 < 5 19 7 6 9 6 < 5 Tl ppm 1,1 0,6 0,3 0,5 0,9 0,3 0,5 0,6 0,2 0,9 0,3 0,2 0,6 1,1 0,1 0,3 0,7 0,5 0,8 0,2 0,7 0,6 0,6 0,6 0,7 0,7 0,9 0,5 0,8 0,5 0,5 Ta ppm 0,9 2,4 0,7 1,4 1 0,8 2,2 0,8 0,4 0,8 1 1 1,3 0,7 0,3 0,4 1,4 1,2 1,3 2,6 1,2 1,1 0,9 1,5 1,1 1,4 1,2 1,4 1 1,5 1,7 Hf ppm 3,1 5,8 7,1 4,4 3,5 3,6 7,2 8,2 1,5 3 3,6 8,5 4,7 6,1 1,2 5,8 5,3 7,9 4,8 4,4 4,8 8,2 4,3 6,6 4,6 6,8 4,5 6,7 4,4 8,5 8,1 Cs ppm 9,2 9,6 5,8 10,8 10,5 8,8 9,4 8 2,6 8 10,8 10,8 10,1 6,7 2,3 2,3 10,2 5,9 11,1 1,4 10,8 6,5 8 8,5 9,7 8,5 10,3 7,5 8,3 5,9 8 Sb ppm 4 0,6 0,5 0,5 2,5 0,9 < 0.5 0,6 0,7 5,5 0,9 0,5 0,6 0,8 0,8 < 0.5 1 0,5 1,6 0,8 1 1,1 1 < 0.5 2 1,4 1,2 1 0,5 0,7 0,6 Mo ppm 19 < 2 < 2 4 13 2 < 2 < 2 < 2 23 2 < 2 < 2 < 2 < 2 < 2 < 2 < 2 6 < 2 10 < 2 3 < 2 12 < 2 42 < 2 11 < 2 < 2 Nb ppm 12 34 8 20 14 13 34 10 6 11 14 13 19 9 4 4 20 16 18 15 18 15 14 21 15 20 17 20 14 21 26 Rb ppm 128 114 78 154 141 131 116 98 40 118 150 122 149 88 39 43 156 104 149 29 139 106 119 134 137 128 143 118 124 91 115 As ppm 37 7 6 8 5 21 8 < 5 < 5 47 9 < 5 13 < 5 < 5 < 5 16 10 20 < 5 23 9 46 14 53 17 14 31 45 17 10 Ga ppm 21 11 24 19 19 23 14 7 17 20 19 23 19 13 5 6 24 19 23 6 22 19 20 24 23 22 23 21 21 18 22 Zn ppm 80 < 30 60 540 90 50 < 30 40 270 90 < 30 90 700 < 30 < 30 70 110 70 90 < 30 70 50 220 50 30 90 60 40 90 60 30 Cu ppm 20 10 20 40 30 < 10 20 < 10 60 30 20 10 60 10 20 < 10 20 20 20 < 10 10 30 70 30 80 20 20 20 10 20 20 Ni ppm 20 < 20 < 20 50 < 20 < 20 < 20 < 20 60 30 < 20 < 20 70 < 20 20 30 < 20 30 < 20 < 20 < 20 30 70 40 20 40 < 20 40 30 < 20 20 Co ppm 15 2 6 10 16 14 2 3 9 14 2 7 10 1 < 1 7 9 10 7 4 6 10 21 17 6 15 5 15 15 11 11 Cr ppm 110 60 120 170 120 120 90 30 150 140 100 90 150 70 20 40 90 90 110 40 130 90 120 100 230 100 210 90 140 100 100 Zr ppm 270 156 120 134 256 298 71 106 132 306 168 118 220 36 282 179 287 170 170 172 297 166 231 152 231 153 239 154 304 291 208 Y ppm 22 23 32 40 29 27 18 28 21 33 24 14 20 8 24 24 28 21 20 21 25 33 29 26 28 21 30 24 28 30 21 Sr ppm 63 143 86 194 124 64 144 78 91 70 137 76 60 425 44 143 78 93 156 173 72 91 96 116 96 170 85 131 110 120 133 Ba ppm 297 576 461 626 423 329 500 452 468 372 483 442 331 320 248 434 313 458 177 528 443 422 411 538 370 392 341 425 312 329 377 V ppm 71 139 537 280 122 83 44 550 321 124 150 543 69 30 25 165 120 143 112 163 130 152 156 247 153 236 146 152 117 120 129 Be ppm 1 3 4 3 3 2 1 4 3 3 3 4 1 1 < 1 3 2 3 1 3 2 4 3 3 3 3 3 4 2 2 2 Sc ppm 7 17 13 14 14 8 9 12 12 10 20 12 6 4 3 21 13 17 9 19 12 26 16 21 14 21 14 27 11 14 13

113130 JAN-96-72 79 Sample 87,33 113101 113131 JAN-96-75 84 87,58 113132 JAN-96-77 86,25 113133 JAN-96-79 113134 JAN-96-80 113064 JAN-96-84 113068 JAN-96-88 113072 JAN-96-92 113077 JAN-96-98 113082 JAN-96-100 113087 JAN-96-104 113092 113098 113100

”7018”

­and Greenl North Svalbard

Well Sea Barents Table 3: Trace element analyses of shales from Nordvik, Svalbard, NorthNordvik, Svalbard, from analyses of shales element Barents Sea. the and Greenland Trace 3: Table Region NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 77

(chlorite, illite/smectite mixed layered clay minerals, illite and kaolinite) in varying amounts. In addition, minor 7 6,4 6,6 9,5 3,9 7 2,5 4,4 10,1 3,6 1,9 2,3 5,1 amounts of potash feldspar and plagioclase are present, along with carbonates and pyrite (Table 1). The sandy 14,7 11,4 12,4 9,9 11,5 8,4 11,5 4,4 14,5 13,3 7 6,2 12,6 shales sampled from North Greenland are, as expected, in particular rich in quartz and illite (and mica) and rel- < 5 0 < 5 8 7 8 6 5 8 < 5 8 33 < 5 atively low in pyrite compared to the other, more fine- grained, Barents region shales. A high quartz content is 1,2 0,2 1,2 2,6 0,5 0,7 0,4 0,2 0,5 0,2 0,3 < 0.1 0,5 seen in elevated SiO2 concentrations in the North Green- land shales (Figs. 9, 10 and 14). The higher sand fraction 1 0,9 0,9 0,7 0,9 0,9 1 0,4 0,7 0,9 0,5 0,4 0,9 is also reflected in the enriched Zr values (Figs. 11, 13 and 14). The Svalbard and Barents Sea well 7018 shales 3,6 4,1 3,3 3,6 3,1 3,8 3,2 1,9 3,3 3,5 2,1 2 3 have comparable amounts of clay minerals, but some- what higher concentrations of plagioclase and carbon- 8,9 7,6 8,3 8,1 9,1 9,7 9,6 4,4 8,9 8,7 5,5 4,7 9,2 ates (calcite, siderite) than the other Barents Sea locali- ties (Table 1). This is evident in increased carbonate and 1,9 4,4 1,3 0,7 3,9 7,3 2 1,4 1,6 0,5 0,8 2,9 2,1 CaO concentrations (Figs. 9 and 10). The samples from core 7018/05-U-01 in the Barents Sea are relatively high 31 3 38 19 5 0 3 0 7 < 2 < 2 5 6 in illite and kaolinite, contain relatively large amounts of feldspar (equal amounts of potash feldspar and plagio- 13 12 12 10 12 12 13 6 11 13 8 8 13 clase) and are rich in dolomite, siderite and pyrite com- pared to the other Barents region localities (Table 1). In 130 108 126 107 133 123 137 57 127 134 75 70 132 well 7018/05-U-01 clay minerals of mixed - layered illite/ smectite and kaolinite composition dominate.

< 5 77 28 97 27 11 18 17 12 16 8 50 25 Compared to these shales, the Nordvik shale mineral- ogy (Figs. 9 and 10; Table 1) is somewhat different with 19 24 19 21 18 22 18 11 18 19 11 10 18 less quartz and much more chlorite that the Barents Sea samples. The high chlorite concentrations are reflected 1220 56 590 395 140 417 80 89 130 120 60 130 110 in Fe2O3 and MgO enrichments in the Nordvik samples (Figs. 10 and 13). 60 90 60 116 30 71 40 29 40 < 10 20 30 40 The Nordvik shales are very high in plagioclase, low in 60 69 80 189 30 119 30 36 30 < 20 < 20 80 40 carbonate ­and contain fairly abundant pyrite compared to beds from the Barents Sea region. The low carbonate values­ 9 19 10 160 13 69 14 25 16 15 9 34 10 in the Nordvik samples may reflect their high-­latitude location, and possibly reduced carbonate production, 140 185 130 130 130 112 140 65 140 120 70 80 140 compared ­to the shales from the West Arctic localities.

119 142 112 127 108 141 112 70 106 133 76 76 110 The major element geochemistry of the analysed samples (Fig. 10) is rather homogeneous, except for the above- 19 59 19 53 24 28 16 44 81 22 20 54 22 mentioned SiO2 enrichments in the North Greenland­ samples and the Fe2O3 enrichments in the Nordvik 70 292 72 141 100 156 92 129 142 245 175 129 88 samples­. The high Fe2O3 contents together with the chlo- rite and plagioclase enrichments reflect a source area 423 657 421 496 476 525 480 435 533 862 485 408 466 enriched in basaltic/amphibolitic volcanic rocks, possibly ­ the Siberian Traps. 462 434 445 422 412 326 400 210 396 280 133 130 338 The trace element and REE compositions of the Arctic­ shales are comparable to those of average shales in the 3 4 3 3 4 3 4 3 3 2 1 1 3 literature (Table 7). Differences exist for some elements ­ (e.g. V, U, Zn, Cu, Ni and Co), generally reflecting­ 12 27 12 27 22 29 12 16 16 11 9 18 12 different­ degrees of ventilation. The Arctic shales contains­ on the average somewhat lower concentrations of these elements, showing better ventilation and overall

less reducing ­conditions. 87,93 NV0.25 88 NV12.10 88,22 NV12.60 89 NV13.20 89,25 90,05 91,5 97,5 100,63

samples ”7018” (contined) ”7018”

shale Nordvik Barents Sea Well Well Sea Barents The different shales analysed display overall comparable trace element concentrations (Figs. 11, 12, 13, 14 and 15). 78 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Table 4: Rare earth element (REE) analyses of shales from Nordvik, Svalbard, North Greenland and the Barents Sea. La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Region Sample ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm

113130 30 51.3 6.27 23.1 4.2 0.87 3.2 0.5 3.3 0.7 2.2 0.35 2.4 0.36

113131 33.5 58.6 7.01 25.2 4.6 1.01 4 0.7 4.2 0.9 2.7 0.43 2.8 0.43

113132 41 73.2 8.86 32 5.8 1.19 5 0.8 5 1 3.2 0.5 3.3 0.49

113133 28.6 49.8 5.95 21.4 3.7 0.76 3.1 0.5 3 0.6 2 0.31 2.1 0.32

113134 16.5 31.2 4.05 17 3.7 0.88 3.6 0.6 3.2 0.6 1.8 0.27 1.7 0.27 113064 39.1 93.2 9.46 33.9 6.3 1.36 5.2 0.9 4.9 1 2.9 0.45 3 0.43 113068 16.8 49.4 4.74 18.8 4.4 1.28 4.1 0.7 3.4 0.6 1.9 0.27 1.7 0.26 113072 37.9 104 9.41 34.3 6.4 1.36 5.2 0.9 4.9 0.9 2.8 0.42 2.7 0.4 113077 50.7 126 12.1 42.4 7.5 1.62 5.6 1 5.2 1 3 0.47 2.9 0.42 North Greenl ­ and 113082 45.2 116 11.1 40.2 7.5 1.7 5.9 1 5.5 1 3.1 0.48 3 0.44 113087 45.7 112 11.2 41.2 7.5 1.73 6.2 1 5.5 1 3 0.46 2.8 0.41 113092 40.6 91.6 9.58 35 6 1.38 5 0.8 4.7 0.9 2.8 0.43 2.7 0.41 113098 47 108 11.3 40.1 6.9 1.59 5.6 0.9 5.2 1 3 0.46 2.9 0.41 113100 47.4 95.5 10 32.9 5 1.09 3.4 0.6 3.5 0.7 2.2 0.35 2.3 0.34 113101 46.9 95.1 10.3 36.5 6.4 1.5 5.3 0.9 4.9 0.9 2.8 0.43 2.7 0.39

JAN-96-72 40.9 93.3 9.13 32.1 4.6 0.92 2.8 0.5 3.5 0.8 2.4 0.38 2.5 0.38 JAN-96-75 17.2 37 3.94 14.5 2.7 0.76 2.5 0.4 2.3 0.5 1.4 0.22 1.5 0.22 JAN-96-77 41.4 96.7 9.71 33.2 5.3 1.14 3.5 0.6 3.9 0.8 2.5 0.39 2.6 0.39 JAN-96-79 9.6 22.2 2.3 8.5 1.6 0.4 1.3 0.2 1.2 0.2 0.7 0.1 0.6 0.09 JAN-96-80 46.2 106 10.9 38.1 6.3 1.38 4.4 0.7 4.2 0.8 2.6 0.41 2.7 0.4 JAN-96-84 38 83.3 8.71 30.2 4.8 0.96 3.4 0.6 3.6 0.7 2.2 0.34 2.2 0.33

Svalbard JAN-96-88 35.6 79.7 7.92 27.2 4.1 0.84 3.1 0.5 3.2 0.7 2.1 0.34 2.3 0.34 JAN-96-92 43.1 104 12.1 47 10.2 2.39 8.8 1.4 7.3 1.3 3.6 0.52 3.3 0.48 JAN-96-98 41.5 87.7 10.4 37.5 6.6 1.39 5 0.8 4.6 0.9 2.7 0.42 2.7 0.4 JAN-96-100 39.6 74 8.13 24.7 3.2 0.69 2.6 0.4 2.9 0.7 2.3 0.38 2.7 0.43 JAN-96-104 46.4 126 12.8 47.7 8.7 1.83 6.2 0.9 5 0.9 2.6 0.38 2.6 0.36

79 39 89.3 9.79 37.1 7.1 1.65 6.4 1.1 5.7 1.1 3.2 0.49 3.1 0.42 84 34.7 82.1 8.92 33.1 6.2 1.47 5.4 0.8 4.8 0.9 2.7 0.39 2.4 0.35 86.25 25.2 48.5 5.01 17.5 2.9 0.62 2.3 0.4 2.1 0.4 1.4 0.26 1.9 0.28 87.33 44.6 127 11 41.4 7.7 1.81 6.4 1.1 6.1 1.2 3.5 0.53 3.3 0.48 87.58 26.7 51.9 5.4 18.8 3.3 0.71 2.7 0.5 2.7 0.6 1.9 0.33 2.3 0.37

87.93 33.5 76.4 8.09 28.5 5.1 1.11 3.9 0.6 3.4 0.7 2.1 0.34 2.3 0.34 88 31.2 69.3 7.39 26.7 4.8 1.02 3.7 0.6 3.2 0.6 2 0.33 2.3 0.32 88.22 33.8 76.3 7.41 26.2 4.9 1.16 4.2 0.7 3.7 0.7 2.3 0.38 2.4 0.36 ”7018” 89 27.3 52.6 5.18 17.9 3 0.65 2.4 0.4 2.3 0.5 1.6 0.3 2.1 0.34 Barents Sea Well Well Barents Sea 89.25 65.3 246 25.1 106 23.3 5.79 21.1 3.3 16.8 2.8 7.2 0.92 5.1 0.65 90.05 35.2 101 8.27 30.9 5.9 1.31 4.5 0.8 4.2 0.8 2.2 0.33 2.2 0.32 91.5 22.1 57.2 5.03 18.6 3.4 0.81 3 0.5 2.9 0.6 1.8 0.26 1.7 0.26 97.5 27.9 81.4 7.57 30 6.3 1.64 6.9 1.2 7.1 1.5 4.5 0.63 3.8 0.54 100.63 41.7 100 10.1 37.5 6.5 1.45 5.2 0.8 4.1 0.7 2.2 0.34 2.3 0.33

61.7 116 12.8 46.4 9 2.47 8.7 1.5 8.8 1.7 4.7 0.69 4.4 0.66 3,64 53.2 110 11.9 44 8.6 2.47 9 1.5 8.2 1.6 4.5 0.64 4.1 0.66 3,49 33.1 70.8 7.29 25.6 4.9 1.34 4.5 0.8 4.5 0.9 2.7 0.4 2.6 0.43 0,99 samples

Nordvik shale Nordvik 31.3 62.5 6.66 25.9 5.5 1.62 6 1 5.9 1.2 3.3 0.47 3 0.47 3,72 NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 79

Table 5: Summary table of the correlation associations displayed in the correlation coefficients from the four areas studied. A short summary is given along the lower part of the table. The original table can be obtained by contacting the senior author. Svalbard Association 1: Si, Al, Sc, Be, V, Y, Zr, Cr, Ga, Rb. Siliciclastics Nb, Cs, Ta, Hf, Ta, W, Tl, Th, U, Na, K, Ge, As and REE Association 2: Ni, Cu, Co, Zn Sulphides Association 3: Ca, Sr, LOI Calcite Association 4: Fe, P, Mn, Mg, LOI Siderite, phosphates North Greenland­ Association 1: Na, As, Th , REE, Al, Sc, V, Co, K, Ti, Be, Ba, Cr, Cu Ga, Rb, Cs Siliciclastics without quartz Association 2: Si Quartz with some positive relations to K-feldspar Association 3: Mn, Mg, Fe, Ca, P, LOI, Sr, Ta Carbonates; Calcite and siderite Barents Sea Association 1: Si, Al, Na, K, Ti, P, Be, V, Cr, Zr, Ga, Rb, Nb, Cs, Hf, Ta, Th Siliciclastics Association 2: Fe, LOI, Co Siderite? Association 3: V, U, Te Association 4: Ca, LOI Calcite? Association 5: Ni, Co, Zn, Mo Sulphides Association 6: REE, U, K Clay minerals Nordvik Only four shale samples have been analysed. The main correlation associations found are: Association 1: Si, Al, Na, K, Sc, V, Ba, Zr, Cr, Co, Ni, Cu, Ga, As, Rb, Nb, Quartz and heavy minerals Mo, Sb, Hf, Ta, Tl, Th, U and REE Association 2: Fe, Mn, Mg, Ca, LOI , P, Y (Be, Sr). Smectite, chlorite, illite and calcite? Association 3: Si, Al, Na, K, Ti, TOC, Sc, Zr, Zn, Ga, Rb Nb, Cs, Hf, Pb, Co, Kaolinite and K-feldspar Ni, Tl Association 4: Cs, K and pyrite

It looks like the quartz and heavy minerals fraction (association 1) are related to kaolinite and in contrast to plagioclase and calcite. The clay minerals smectite, chlorite, illite and a few main and minor elements (association 2) are varying against quartz of association 1 and kaolinite and K-felspar of association 3. It should be remarked that only 4 Nordvik samples are analysed.

A few differences are found between the same elements, contents of planktonic organisms and higher pyrite con- but the variations in Ba, Ga, Tb, Nb, Pb, Th, U, Ta, Tl, centrations in the Nordvik area (Co, Ni, Cu), as demon- Mo, Sb and Cs are similar in all the studied Arctic sec- strated above. tions. In order to reduce dilution effects in the distributions The sandy to silty North Greenland shales are, however, (e.g., from varying amounts of secondary carbonates depleted in Sr, Cr and V and enriched in Zr and Hf com- and high amounts of quartz and silica) when compar- pared to the other shales (Table 1, Figs.11, 13, 14 and ing the different formations, selected trace element ratios 15). This can be related to variations in heavy-mineral are used in the comparisons. A few key ratios and ele- contents (Zr, Hf) and more oxidising depositional con- mental relations have been picked out (Figs. 13, 14 and ditions (Cr, V depletion). It is evident that the North 15). The Sc/Al2O3, K2O/Al2O3, Ba/Al2O3, Cu/Al2O3, Zn/ Greenland sections represent a shallow-marine, coastal Al2O3, and V/Cr ratios are similar in the different shale position in more oxidised depositional conditions than locations (Fig. 15). These ratios may disclose informa- the other sections studied. tion on parameters such as sedimentary source areas

and grain sizes (Sc/Al2O3, K2O/Al2O3), diagenetic reac- The V and Zn concentrations are somewhat enriched in tions and authigenic minerals (K2O/Al2O3, Ba /Al2O3, the Nordvik and Barents Sea samples compared to the Cu/Al2O3), and reducing and sulphur-enriched environ­ North Greenland shales (Figs. 11, 13, 14 and 15), pos- ments (Zn/Al2O3, V/Cr) (Taylor 1965; Martin & Knauer sibly reflecting their more distal, less ventilated, basinal 1973; Dypvik & Harris 2001; Perkins & Foster 2004). position (more anoxic depositional conditions). The Such related distributional trends and comparable ratios Nordvik samples in addition display high Sc, Y, Co, Ni, conse­quently indicate generally similar depositional Cu and As values compared to the other Arctic locations conditions of well reworked and partly mixed sedi- (Figs.11, 13 and 14). This may be a response to different ments in the Arctic basin at that time, with an additional clastic (ultramafic, volcanic?) source areas (Sc,Y) (Tay- basalt­ic component in the Nordvik samples and a higher lor 1965) and possibly more reducing conditions, higher sand/silt content in the North Greenland samples. 80 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Table 6: Geochemical ratios from the shale samples analysed (raw data from Tables 2 and 3).

Region Sample Sc/Al2O3 K2O/Al2O3 Ba/Al2O3 Cu/Al2O3 Zn/Al2O3 V/Cr V/Cu Cr/Cu Mo/Cu Mo/Zn Cu/Zn Th/U

113130 0.88 0.30 37.13 1.25 3.75 1.18 7.10 6.00 0.20 0.07 0.33 2.25

113131 0.84 0.29 34.63 2.11 3.16 0.92 4.15 4.50 0.10 0.07 0.67 2.11

113132 0.76 0.25 28.25 1.52 2.28 1.24 6.20 5.00 0.10 0.07 0.67 2.17

113133 0.65 0.28 35.98 1.09 3.26 0.99 6.90 7.00 0.20 0.07 0.33 2.34

113134 0.57 0.32 46.88 1.89 13.23 0.63 2.50 4.00 0.20 0.03 0.14 2.11 113064 0.92 0.24 22.06 1.41 4.93 1.33 6.00 4.50 0.10 0.03 0.29 5.07 113068 2.15 0.27 42.24 2.39 7.16 2.80 11.20 4.00 0.20 0.07 0.33 3.67 113072 0.86 0.24 31.76 2.15 3.58 1.44 4.33 3.00 0.07 0.04 0.60 3.40 113077 0.88 0.23 22.68 1.66 2.76 1.56 5.20 3.33 0.07 0.04 0.60 5.16 North Greenl ­ and 113082 0.83 0.23 21.85 1.18 5.32 1.53 7.65 5.00 0.10 0.02 0.22 4.87 113087 0.89 0.24 21.71 1.27 2.55 1.62 7.30 4.50 0.10 0.05 0.50 4.73 113092 0.79 0.21 22.49 1.44 4.33 1.17 5.85 5.00 0.10 0.03 0.33 4.58 113098 0.82 0.20 19.35 1.18 1.76 1.20 6.00 5.00 0.10 0.07 0.67 4.83 113100 0.81 0.20 23.55 1.25 5.00 1.17 6.45 5.50 0.20 0.03 0.25 3.94 113101 0.78 0.18 23.49 0.56 2.78 1.02 12.20 12.00 0.20 0.04 0.20 4.50

JAN-96-72 0.93 0.21 31.67 1.10 3.30 1.16 6.95 6.00 0.10 0.07 0.33 2.77 JAN-96-75 1.78 0.20 99.01 1.98 7.92 1.47 4.40 3.00 0.20 0.05 0.25 2.69 JAN-96-77 1.21 0.21 29.31 0.61 5.46 1.67 15.00 9.00 0.20 0.02 0.11 3.35 JAN-96-79 1.07 0.24 85.79 5.36 8.04 1.50 1.50 1.00 0.30 0.07 0.67 3.56 JAN-96-80 1.21 0.21 25.07 1.16 6.35 1.83 8.25 4.50 0.50 0.02 0.18 3.90 JAN-96-84 1.04 0.20 27.96 1.22 5.49 1.30 7.15 5.50 0.15 0.07 0.22 3.23

Svalbard JAN-96-88 1.19 0.21 33.00 0.63 4.38 1.25 16.30 13.00 1.20 0.14 0.14 2.15 JAN-96-92 1.61 0.19 26.15 4.34 13.63 1.27 2.17 1.71 0.60 0.01 0.32 3.44 JAN-96-98 1.20 0.19 30.81 4.58 1.72 1.07 3.09 2.88 0.14 0.40 2.67 3.60 JAN-96-100 1.31 0.21 24.39 1.24 3.73 1.12 11.80 10.50 0.65 0.70 0.33 1.38 JAN-96-104 1.90 0.21 29.85 0.70 6.32 1.09 15.20 14.00 2.30 0.12 0.11 3.42

79 0.84 0.23 29.94 2.60 35.06 3.16 13.43 4.25 0.48 0.02 0.07 2.27 84 0.83 0.23 31.30 4.16 18.70 3.67 9.17 2.50 0.03 0.09 0.22 1.74 86.25 0.79 0.23 28.98 3.93 45.90 3.62 9.05 2.50 0.03 0.03 0.09 3.71 87.33 1.01 0.23 45.30 2.17 6.51 2.33 9.33 4.00 1.03 0.02 0.33 3.21 87.58 0.80 0.24 31.10 1.99 5.98 2.29 10.70 4.67 1.27 0.02 0.33 5.87

87.93 0.79 0.23 27.98 3.97 80.69 3.30 7.70 2.33 0.08 0.03 0.05 2.10 88 0.82 0.23 28.60 4.08 40.08 3.42 7.42 2.17 0.05 0.06 0.10 1.88 88.22 ”7018” 1.46 0.24 31.61 1.99 9.30 3.17 13.73 4.33 0.23 0.04 0.21 2.95 89 Barents Sea Well Well Barents Sea 0.77 0.24 30.61 2.55 5.10 2.86 10.00 3.50 0.05 0.04 0.50 4.60 89.25 1.13 0.23 37.56 2.82 9.16 2.83 9.90 3.50 0.05 0.05 0.31 1.44 90.05 0.73 0.24 57.24 0.66 7.97 2.33 28.00 12.00 0.50 0.02 0.08 3.69 91.5 1.05 0.23 56.40 2.33 6.98 1.90 6.65 3.50 0.30 0.03 0.33 3.68 97.5 2.21 0.21 50.00 3.68 15.93 1.63 4.33 2.67 0.00 0.04 0.23 2.70 100.63 0.83 0.24 32.29 2.77 7.62 2.41 8.45 3.50 0.00 0.05 0.36 2.47

NV0.25 1.46 0.14 35.51 4.86 3.03 2.35 4.82 2.06 0.03 0.05 1.61 1.78 NV12.10 1.69 0.16 30.96 7.24 24.66 3.25 3.64 1.12 0.16 0.05 0.29 1.04 NV12.60

samples 1.54 0.16 27.91 3.77 22.17 2.91 4.59 1.58 0.00 0.00 0.17 1.20

Nordvik shale Nordvik NV13.20 1.88 0.17 51.24 3.42 10.48 3.23 7.24 2.24 0.00 0.00 0.33 1.00 NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 81

Figure 9. Mineralogical com- parison of average XRD shale 6600 6600 analyses from the sections at mineralogicalmineralogical composition composition North Greenland, Svalbard, X-rayX-ray diffraction diffraction results results the Barents Sea and Nordvik. 5500 5500 Related distributions appear in the four regions, but plagioclase 40404040 and chlorite enrichments are SN GreenlanderSNi eGreenlandesri1es1 well developed in the Nordvik SSvalbarderSSvalbardieesri2es2 samples and quartz enrichments 30303030 are seen in the North Greenland SBarentserSiBarentsee sSeari3e sSea3 samples. The values are semi- SNordvikerSiNordvikeesri4es4 quantitative XRD percentages. 2200 2200 14Å = smectite + chlorite, 12Å concentration in % concentration in % = smectite/illite mixed-layered 10 10 clay minerals, 10Å = illite, 7Å = 10 10 chlorite and kaolinite. 0 0 141 Å14 1 Å 12 2 Å 12 2 Å 10 3 Å 10 3 Å 7 4 Å 7 4 Å Quartz 5 Quartz5 K-fspr.6 K-fspr.6 Plag.7 Plag. 7 Cal. 8 Cal. 8 Dol. 9 Dol. 9 Sid. 1 0 Sid.1 0 Pyrite 1 1 Pyrite11

FigureFigure 9 9 Figure 10. Average major ele- DypvikDypvik and and Zakharov, Zakharov, 2011 2011 ment geochemistry of the 70.0700 analysed shale samples from main element geochemistry North Greenland, Svalbard, the Barents Sea and Nordvik. The 60.0600 compositions are compar­able, con- but somewhat higher Fe2O3 50.0500 tents in Nordvik and more SiO 2 N Greenland in the studied North Greenland Series1 40 samples are apparent. 40.00 SSvalbarderies2 LOI = loss on ignition. Barents Sea 30.0300 Series3 SNordvikeries4 20.0200

concentration in % 10.0100

0.00 SiO12 Al2O3 Fe32O3 MnO4 MgO5 CaO6 Na72O K28O TiO9 2 P12O05 LOI11

Figure 10 Dypvik and Zakharov, 2011 In the studied localities (North Greenland, Svalbard, The Ce-anomaly values calculated for the sediments are Barents Sea well 7018/05-U-01 and Nordvik), com- above one in all the studied shales. This reflects water parable REE contents with rather flat, non-fraction- masses with more oxidising than reducing conditions ated REE distributions are found (Table 4, Fig. 12), with (Byrne & Sholkovitz, 1996), above a possibly reducing only minor, positive Eu-anomalies in few plagioclase- depositional seafloor normally dominated by dark, finely enriched samples from Svalbard, North Greenland and laminated, organic rich clays. In all the Nordvik shale Nordvik. The analysed samples show great similarities samples, weak positive Ce-anomalies are found, which to the average North American Shale composite (Table according to Murthy et al. (2004) possibly reflect mainly 7). The average­ REE patterns of the Nordvik shales, dysoxic basinal conditions. Ohta et al. (1999) showed and shales analysed from the Barents region localities negative Ce-anomalies to occur in pelagic formations are rather similar­. The Nordvik samples, however, show when precipitated from Ce-depleted sea water. In the the highest and most clear-cut Eu-enrichments. This Arctic localities this is not the case; the Ce-anomalies likely reflects their higher contents of clastic, basalt- are on average greater than one, probably reflecting a derived plagioclase compared to the other shales anal- somewhat more oxidising sea water above a partly anoxic ysed. Murthy­ et al. (2004) claim Eu-anomalies to occur basinfloor as seen in the finely laminated clays. Possible only during extremely reducing, early diagenetic condi- geochemical zonation due to position in the deposit­ional tions. In plagio­clase, however, Eu-anomalies commonly basin is difficult to detect , but in coastal and marginal­ exist (Wildeman & Haskin, 1973), which in Nordvik is marine environments (North Greenland) some geo- support­ed by the relative high clastic feldspar content of chemical differences should be expected. Davranche the shale samples. et al. (2005), however, did not find any clear-cut

82 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Table 7: Average trace element and rare earth element compositions from the Arctic localities compared to the average shales and some typical black shale formations. REE values from Condie (1991) (Upper Continental Crust values - UCC), Vital et al. (1999) (Amazon clays) and Haskin & Frey (1966) and Gromet et al. (1984) (North American Shale Composite), Kimmeridge Clay values from Tribovillard et al (1994), while average shales values (Norwegian black shales, CTBE – Cenomanian Turonian boundary event - black shales and average shales) were compiled by Lipinski et al. (2003). Selected elements Element N Greenl. Svalbard BarentsS Nordvik Kimm. Norweg. CTBE Average shales shales shales shales shales b.shales b.shales shales Ba 338 461 500 528 268 492 645 580 Co 9 9 14 68 21 17 33 19 Cr 87 117 130 123 125 158 137 90 Cu 20 28 42 77 71 106 188 45 Mo <2 <2 13 6 n.d. 62 145 1.3 Ni 31 35 51 103 104 138 162 68 Sb 0.8 1 2.6 2.1 n.d. 10.5 15.4 1 Tl 0.5 0.6 0.6 0.9 n.d. 3.5 3.5 0.68 U 3 4 5 7 7 13 18 3 V 112 147 373 348 166 864 739 130 Zn 59 86 305 239 119 944 1213 95 Rare Earth Elements N Greenl. Svalbard BarentsS Nordvik Amazon NASC UCC shales shales shales shales clays La 37.8 36.3 34.9 44.8 53.4 39 30 Ce 83.6 82.7 89.9 89.8 122 76 64 Pr 8.76 8.73 8.88 9.96 13.8 10.3 7.1 Nd 31.6 30.97 33.59 35.48 52.83 37 26 Sm 5.73 5.28 6.46 7 10.56 7 4.5 Eu 1.29 1.15 1.51 1.98 2.07 2 0.88 Gd 4.69 3.96 5.58 7.05 8.62 6.1 3.8 Tb 0.79 0.64 0.91 1.2 1.25 1.3 0.64 Dy 4.43 3.79 4.94 6.85 6.86 5.75 3.5 Ho 0.85 0.75 0.94 1.35 1.3 1.4 0.8 Er 2.63 2.28 2.76 3.8 3.66 4 2.3 Tm 0.41 0.35 0.42 0.55 0.5 0.58 0.33 Yb 2.6 2.34 2.66 3.53 3.31 3.4 2.2 Lu 0.39 0.35 0.38 0.56 0.48 0.6 0.32

Ce-anomalies in their experimental studies, indicating floor, whilst the overlying water column must have been that the Ce-anomaly can be an unreliable proxy of redox well mixed and oxidising. conditions in organic-richwaters. Only small differences are displayed in the regional A common diagenetic development is not very likely REE distributions when studied in detail. The Svalbard over such a wide area and consequently not applicable as and North Greenland shale samples display more varia- an explanation for the comparable REE distributions in tions in the LREE parts of their diagrams compared to the four areas. The comparable REE patterns are most the other sections (Table 4). This is most likely a source- likely the response of good ocean circulation and mixing related phenomenon, but it could be a grain-size effect or over an extensive area. Consequently, we think the REE of local diagenetic origin, e.g., in association with dia­ distributions show that the Arctic basin was dominated genetic carbonate precipitation. by dysoxic (to anoxic) depositional conditions on the sea NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 83

Figure 11. Average trace ele- ment concentrations of the ana- 660000 lysed sections at North Green- trace element geochemistry land, Svalbard, the Barents Sea 550000 and Nordvik. Some variations are found in the different trace element distributions, in parti- 404000 SN Greenlanderies1 cular the V, Zr and Zn concen- SSvalbarderies2 trations. 330000 SBarentserie sSea3 SNordvikeries4 220000

concentration in ppm 110000

00 Sc Be V Ba Sr Y Zr Cr Co Ni Cu Zn Ga As Rb Nb Mo Sb Cs Hf Ta Tl Pb Th U 1 3 5 7 9 11 13 15 17 19 21 23 25 Figure 11 Dypvik and Zakharov, 2011 Figure 12. Normalised (average Upper Continental Crust values 4.5 - UCC; Condie 1991) REE distri- 44 bution of average values of shales from Nordvik, and shale samples 3.5 from North Greenland, Svalbard and the Barents Sea. The Nord- 3 vik shales display enrichments 2.5 in the heavy REE (HREE) com- Nordvik shales pared to the samples from the 22 Barents Sea region. Here, the Core 7018 Barents Sea average values are given for com- 1.5

parison purposes; individual (ppm) / UCC CONCENTRATION 1 sample element contents are pre- North Geenland shales sented in Table 4. 0.5 Janusfjellet Sbgp, Svalbard 00 1La Ce2 Pr3 Nd4 Sm5 Eu6 Gd7 Tb8 Dy9 1 Ho0 1 Er1 1 Tm2 Yb1 3 Lu1 4 ATOMIC NUMBER

Figure 12 Dypvik and Zakharov, 2011

The REE distributions in the Nordvik shales are weakly different areas, but they have yet to be determined. Mur- enriched in HREE as compared to the other sections thy et al. (2004) claimed MREE to be distally enriched in the (Fig. 12). The REE patterns of the North Greenland depositional basin due to MREE co-precipitation with phos- and Svalbard ­samples are more varied than the Nordvik phates. In our study we have not observed any MREE enrich- shales , but they all display generally flat-lying trends. ments and the La values are much more varied and higher This relative HREE enrichment in some of the Nordvik compared to the analyses presented by Murthy et al. (2004). samples along with the Eu-anomaly may possibly reflect a basaltic source rock component in the provenance area (?Siberian traps) (Fig. 2) (Ronov et. al. 1972; Arndt et al. Conclusions 1998; Saunders et al. 2005). In the Barents Sea region, a clastic REE control is seen in the positive REE-clastic Fine-grained sediments of the Arctic, from the west element­ relationships (e.g., SiO2, Al2O3, TiO2). (North Greenland, Svalbard, Barents Sea) and the east (Nordvik in North Siberia), have been studied by sedi- The overall mineralogical and geochemical compositions mentary logging and using mineralogical and geochemi- are rather similar for all the analysed shales, as reflected in cal analyses, supported by detailed stratigraphical infor- their selected trace element ratios (against Al2O3) and in mation. The stratigraphical comparisons of the mineral- their homogeneous, un-fractionated REE patterns (Figs. ogical and geochemical distributions are possible due to 12 and 15). Flat REE patterns in shales indicate units com- the presence of fairly well established lithostratigraphical posed mostly of terrigeneous material (Toyoda & Masuda units which can be correlated across the Late Jurassic to 1991). Any diagenetic changes were most likely minor in the Early Cretaceous, Arctic epicontinental sea. 84 H. Dypvik & V. Zakharov NORWEGIAN JOURNAL OF GEOLOGY

Zr Na2O + K2O

Legend

North Greenland Svalbard Barents Sea Nordvik

Sc + Cr Cu + Zn Fe2O3+MgO+MnO SiO2

Figure 13. Triangular plots of key geo­chemical relationships. The left diagram (Sc+Cr, Zr, Cu+Zn) displays variations mainly due to differen- ces in source rock characterisation and depositional conditions of the shales. The right diagram (Fe2O3+MgO+MnO, Na2O+K2O, SiO2) to some extent illustrates grain-size and source-rock variations in the shale samples.

5 4 The wide paleo-Arctic epicontinental sea of Late Juras- % K2O 3 + sic to Early Cretaceous age was characterised by water % Na2O 2 depths of about 300 to 600 m and a generally low relief 1 in the surrounding landmasses. In the Late Jurassic there were no global glaciations and no large global ocean 0 current systems were active. In this paper it is shown 0 20 40 60 80 100 that deposition of well-weathered sedimentary parti- % SiO2 cles took place through highly productive, oxygen-rich, upper water masses before deposition in more dysoxic to anoxic depositional environments on the sea floor. Dark organic-rich claystones and shales were commonly 30 deposited in central parts of the basin, whilst along the paleo-coastlines there were more silty/sandy sediments ppm 20 Sc (North Greenland), as reflected in their mineralogi- cal and geochemical compositions. The sediments dis- 10 play comparable compositions reflecting deposition of general­ly well-mixed material, with only minor compo- 0 sitional variations within the different subenvironments 0 100 200 300 400 500 600 (Barents Sea region vs Nordvik). The analysed black ppm V shales generally represent more ventilated, less anoxic conditions than other Late Jurassic black shale forma- Legend tions as, e.g., the North American Shale composite, Kim- meridgeNorth Clay Greenland and the Cenomanian- Turonian bound- 300 ary eventSvalbard shales. The compositional differences seen between Nordvik and the Barents Sea region indicate a ppm Barents Sea Zr 200 more basaltic, albite- and chlorite-rich source area in the east, possiblyNordvik the Siberian Traps. The mineralogical and 100 geochemical differences in the source areas, along with the grain -size differences in the formations, controlled 0 the overall shale composition. 0 5 10 15 20 25 ppm Th In the Nordvik area, the most fine-grained sedimenta- tion took place in combination with a high organic and Legend algal production and/or some possible upwelling. These North Greenland conditions resulted in well-developed phosphate pre- Figure 14 cipitation, confined to thin, organic-rich, finely lami- Figure 14. Geochemical cross plots of shale con- Svalbard centrations as measured in the samples from Barents SeaDypvik and natedZakharov beds 2011 intercalated in the succession. The phos- North Greenland, Svalbard, Barents Sea and Nordvik phate concretions are the result of low clastic sedimen- Nordvik. tation, excess organic production and deposition, and a NORWEGIAN JOURNAL OF GEOLOGY Fine-grained epicontinental Arctic sedimentation 85

Figure 15. The general distribu- 45.00 tion of different key geochemical geochemical ratios ratios (average values) of the 40.00 four locations studied (see Table 6). 35.00 North Greenland 30.00 Svalbard 25.00 Barents Sea 20.00 Nordvik 15.00

10.00

5.00

0.00 Sc/Al2O3 Ba/Al2O3 Zn/Al2O3 V/Cr V/Cu Cr/Cu Mo/Cu Mo/Zn Cu/Zn Th/U K2O/Al2O3 Cu/Al2O3

Figure 15 succeeding diagenesis in shelf environments under pre- Sassen­fjorden areas, Central Spitsbergen.Dypvik & Zakharov, Norsk 2011 Polar Institutt vailing oxygen-deficient conditions. In the Barents Sea Skrifter 1980, 79-134. regions, periods with a lower clastic accumulation are Dypvik, H. 1985: Jurassic and Cretaceous black shales of the Janus­ fjellet Formation, Svalbard. Norway. Sedimentary Geology 41, 235- represented by thin carbonate beds of calcite, dolomite or 248. siderite, partly reflecting a lower paleo-latitude position. Dypvik, H., Nagy, J., Eikeland, T.A., Backer-Owe, K., Andresen, A., Haremo, P., Bjærke, T., Johansen, H. & Elverhøi, A.1991a: The Janusfjellet Subgroup (Bathonian to Hauterivian) on Central Spits- Acknowledgments. - The comments of A. Mørk on an earlier version of bergen: a revised lithostratigraphy. Polar Research 9(1), 21-43. the manuscript are highly appreciated. Referees E. Håkansson and N. Dypvik, H., Nagy, J., Eikeland, T.A., Backer-Owe, K. & Johansen, H. Harris gave valuable comments which improved the quality of the paper. 1991b: Depositional conditions of the Bathonian to Hauterivian IKU/SINTEF Petroleum Research kindly made the core available and Janusfjellet Subgroup, Spitsbergen. Sedimentary Geology 72, 55-78. the late Øystein How is thanked for valuable assistance in the core lab at Dypvik, H. 1992: Sedimentary rythms in the Jurassic and Cretaceous Dora, Trondheim. This study has been supported by RFBR grant 12-05- of Svalbard. Geological Magazine 129, 93-99. 00380. Dypvik, H., Gudlaugsson, S.T., Tsikalas, F., Attrep, M. Jr., Ferrell, R.E.,Jr., Krinsley, D.H., Mørk, A., Faleide, J.I. & Nagy,J. 1996: The Mjølnir structure - an impact crater in the Barents Sea. Geology 24, References 779 - 782. Dypvik, H. & Harris, N.B. 2001: Geochemical facies analysis of fine- Arndt, N., Chauvel, C., Czamanske & Federenko, V. 1998: Two mantle grained siliciclastic using Th/U, Zr/Rb, and (Zr+Rb)/Sr ratios. sources, two plumbing systems: tholeiitic and alkaline magmatism Chemical­ Geology 181, 131 – 146. of the Maymecha River basin, Siberian flood volcanic province. Dypvik, H., Håkansson, E. & Heinberg, C. 2002: Jurassic and Creta- Contributions to Mineraogy and. Petrology 133, 297 – 313. ceous paleogeography and stratigraphic comparison in the North Basov, V.A., Vasilenko, L.V., Sokolov, A.R. & Jakoleva, S.P.,1989: Zonal Greenland – Svalbard regions. Polar Research 21, 91 - 108. subdivision of marine Mesozoic deposits of the Barents Basin. In: Dypvik, H., Mørk, A, Smelror,M., Sandbakken, P.T., Tsikalas, F., Stages of zonal scales of the Boreal Mesozoic SSSR. Trudy Instituta Vigran, J.O., Bremer, G.M.A., Nagy, J., Gabrielsen, R.H., Faleide, Geologii I Geofiziki Sibirskoe Otdelenie, Akademiya Nauk SSSR J.I., Bahiru, M. & Weiss, H. 2004: Impact breccia and ejecta from 772, 60 -74. (in Russian). Mjølnir crater in the Barents Sea – The Ragnarok Formation and Bäckstrøm, S.A. & Nagy, J. 1985: Depositional history and fauna of a Sindre Bed. Norsk Geologisk Tidskrift 84, 143-167. Jurassic phosphorite conglomerate (the Brentskardhaugen Bed) in Dypvik,H., Smelror, S., Sandbakken P.T., Salvigsen, O. & Kalleson, E. Spitsbergen. Skrifter Norsk Polarinsitutt 183, 1-61. 2006: Traces of the marine Mjølnir impact event. Palaeogeography, Byrne, R.H. & Sholkovitz, E.R. 1996: Marine chemistry and geoche- Palaeoclimatology, Palaeoecology 24, 621–636. mistry of the lanthanides. In: K.A.gschneider Jr & L.Eyring (eds): Dypvik, H. & Zakharov, V. 2010: Late Jurassic / Early Cretaceous Handbook of the Physics and chemistry of rare earths. Volume 23, phosphates of Nordvik, North Siberian Basin. Polar Research 29, Elsevier, 498-493. 235- 249. Carrol, D. 1970: Clay Mineral: A Guide to their X-ray identification. Edwards, M.B. 1976: Depositional environments in Lower Cretaceous Geological Society of America Special Paper 126. regressive sediments, Kikutodden, Sørkapp Land, Svalbard. Norsk Condie, K.C. 1991: Another look at rare-earth elements. Geochimica Polarinst. Årbok 1974. 35 – 50. Cosmochimica Acta 55, 2527 – 2531. Faleide, J. I., Vågnes, E. & Gudlaugsson, S. T. 1993: Late Mesozoic- Davranche, M., Pourret, O., Gruau, G., Dia, A. & Le Coz-Bouhnik, Cenozoic evolution of the southwestern Barents Sea in a rift-shear

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