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Biostratigraphy and palaeobiology of Early Neoproterozoic strata of the Kola Peninsula, Northwest Russia

JOAKIM SAMUELSSON

Samuelsson, J.: Biostratigraphy and palaeobiology of Early Neoproterozoic strata of the Kola Peninsula, Northwest Russia. Norsk

Geologisk Tidsskrift, Vol. 77, pp. 165-192. Oslo 1997. ISSN 0029-196X.

Shales and siltstones from the Early Neoproterozoic K.ildinskaya, Volokovaya and Einovskaya Groups and the Skarbeevskaya

Fonnation (Kildin Island, Sredni and Rybachi Peninsulas) and the Chapoma Fonnation (Tiersky Coast) on the Kola Peninsula,

Northwest Russia yielded assemblages of moderately well-preserved organic-walled acid-resistant microfossils (acritarchs, and prob

able cyanobacterial sheaths). The assemblages consist of cosmopolitan taxa recovered from various Early Neoproterozoic (Late and

Terminal Riphean) settings in Scandinavia, Russia, Yakutia, North America and elsewhere. Among the recovered taxa, Lopho

sphaeridium laufeldii Vida) 1976 comb. nov., Satka colonialica Jankauskas, Simia annulare (Timofeev) Mikhailovna, Tasmanites

rifejicus Jankauskas, Valeria lophostriata Jankauskas and Vandalosphaeridium ?varangeri Vida! are regarded as the biostratigraphi

cally most significant. One taxon, Trachysphaeridium laufeldi Vida) is transferred to Lophosphaeridium laufeldii (Vida!) Samuelsson

comb. nov. The units examined herein are all considered to be Late Riphean in age and are correlated with other units of similar

age in northem and southem Scandinavia, Svalbard, East Greenland and the southem Urals.

Joakim Samuelsson, Uppsala University, Institute of Earth Sciences, Micropalaeontology, Norbyviigen 22, S-752 36 Uppsala, Sweden.

Introduction

During the Neoproterozoic, the Baltica palaeocontinent underwent major sedimentological, tectonic and palaeogeographical changes (Kumpulainen & Nystuen 1985; Vidal & Moczydlowska 1995). In the Late Riphean, sedimentological changes occurred that comprised the transition from predominantly non-marine into shallowmarine sedimentation regimes in a number of basins, including passive margin sequences (e.g. the western Baltoscandian basins within the Caledonides; Kumpulainen & Nystuen (1985)) and intracratonic settings (e.g. the Visingso Group; Vidal (1982)). Associated with these sedimentological changes is the initiation of the break-up of a large supercontinent ('Rodinia') in pre-Varangerian time (Storey 1993). Significant pre-Varangerian events include the episodic emp1acement of do1eritic dyke swarms (Kumpulainen & Nystuen 1985; Vidal & Moczydlowska 1995). Palaeomagnetic data show that together with Laurentia, Ba1tica was situated at low to equatorial latitudes during most of the Riphean, but it drifted southward during Vendian times (Gurnis & Torsvik 1994). In Early Vendian ( = Varangerian) time, glacier ice covered wide areas of Baltica. In Late Varangerian time, the melting of the ice sheet resulted in deposition of glacial material, preserved as tillites in, e.g., central East Greenland, Svalbard, the Varanger Peninsula in Norway, the proximity of the Caledonides and the Urals (Kumpulainen & Nystuen 1985; Føyn 1985; Hambrey 1988; Vidal & Moczydlowska 1995).

Acritarchs, cysts of algal protists, have been successfully used for establishing stratigraphy and correlation of

Neoproterozoic strata worldwide (e.g. Vidal 1976a; Vidal

1981a; Knoll 1982a, 1982b; Vidal & Siedlecka 1983; Knoll 1984; Vidal 1985; Knoll et al. 1989; Jankauskas et al. 1989; Vidal & Nystuen 1990a, 1990b; Moczydlowska

1991; Knoll et al. 1991; Knoll 1992). In addition to biostratigraphy, acritarchs have also been widely used for palaeoenvironmental analyses (e.g. Ivanovskaya & Timofeev 1971; Golubic & Hofmann 1976; Knoll et al. 1981, 1991; Mansuy & Vidal 1983; Green et al. 1987, 1988; Palacios Medrano 1989; Moczydlowska & Vidal 1992; Butterfield & Chandler 1992).

Better understanding of the Neoproterozoic evolution of Baltica can be achieved through detailed strati

graphic correlation of all preserved successions on the Baltic Shield. The reviews by Kumpulainen & Nystuen (1985), Føyn (1985), Hambrey (1988) and Vida1 & Moczydlowska (1995) dealt with Neoproterozoic (Late Riphean and Vendian) successions in the northern and western part of Baltica. With the exception of Hambrey (1988), the important Late Riphean deposits of the Kola Peninsula have not been included in these reviews.

In this paper I report on the occurrence of organicwalled microfossils (acritarchs and probable cyanobacterial sheaths) from two areas in the northeastern margin of the Baltic Shield, namely Kil din Island, the Sredni and Rybachi Peninsulas in the Murmansk Coast of the northern Kola Peninsula, and the Chapoma River, lo

cated on the Tiersky Coast in the southern coast of the Kola Peninsula (Fig. 1). The purpose of this work is to complement previously presented data on the biostrati-

166 J. Samuelsson

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NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

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graphy and palaeobiology of these successions that occupy a key position in relation to the East European

Platform and the Varanger Peninsula. Further investigations on stable isotope geochemistry are also in progress (Samuelsson et al. in prep.).

Research history

The geology and stratigraphy of Neoproterozoic successions on the Sredni-Rybachi Peninsula, on the Kildin Island and of the Chapoma River were dealt with in numerous Russian and some Finnish papers (see Siedlecka 1975 and references therein). Timofeev (1969) reported a poor, but typically Upper Riphean microfossil

assemblage from the Kildinskaya Group on Sredni Peninsula. He also reported a taxonomically more diverse assemblage from the Volokovaya Group on Sredni. Negrutsa (1971) outlined the geo1ogy of the Sredni Peninsula and subdivided the Kildinskaya and Volokovaya Groups into several formations. Siedlecka (1975) published a review article (based largely on Russian data) on the Neoproterozoic geology of the northeastern margin of the Fennoscandian Shield including Northern Norway (Varanger Peninsula), the Sredni-Rybachi Peninsulas, the Aynov and Kildin Islands, Kanin Peninsula and the Timan Ridge. Konopleva (1977) discussed the age of the rocks on Rybachi and interpreted them as Middle Riphean. Ragozina & Stepkin (1979) examined the biostratigraphy of rocks on Sredni and Kildin. On mainly biochronological evidence, Vidal & Siedlecka (1983) discussed the possible age relationships of the largely Upper Riphean Barents Sea Group in the Barents

Early Neoproterozoic strata, Kola Peninsula 167

Sea Region in Norway with the successions in Sredni

Rybachi and Kildin. They suggested that the Kildinskaya Group could be time-equivalent with the Kongsfjord and Båsnæring Formations of the Barents Sea Group. In a review paper on the Late Proterozoic Stratigraphy of the Barents Shelf, Hambrey (1988) included a discussion on the geology, age and correlation of the Early Neoproterozoic settings in the Kola Peninsula. Lyubtsov et al. (1989) presented a synthesis on the lithostratigraphy and micropalaeontology of the successions on the Murmansk and Tiersky Coast of the Kola Peninsula. A guide to Neoproterozoic sections on the Murmansk coast and Tiersky Coast was published by the Kola Science Centre, Russia (Lyubtsov et al. 1991a, 1991b). Vidal et al. (1993) discussed the biostratigraphic and time-stratigraphic implications of a Chuaria/Tawuia assemblage and accompanying acritarchs from the

Neoproterozoic of Yakutia and forwarded suggestions upon age relationships with the Kildinskaya Group. Various aspects of the Neoproterozoic of the northeastern part of Baltica in Norway and Russia were dealt with recently in a number of papers in NGU Special Publication 7 (Roberts & Nordgulen, eds. 1995). Drinkwater et al. (1996) evaluated the Late Proterozoic stratigraphy in northern Norway and northern Russia and presented a palaeogeographical reconstruction of these units.

Geological setting

The Baltic Shield comprises northwestern Russia, Finland, parts of northern and southern Norway and almost

RYBACHI PENINSULA SREDNI PENINSULA KILDIN ISLAND

Bargoutnaya Group

• Tsypnavolokskaya Formation

[TI Zubovskaya Formation

� Maiskaya Formation

Einovskaya Group

D Perevalnaya Formation

E::::::J Lonskaya Formation

� Motovskaya Formation

O Skarbeevskaya Formation

\blokovaya Group

9 Pumanskaya Formation

f'� 'd Kuyakanskaya Formation

Kildinskaya Group

ffi Karuyarvinskaya Formation

Jfll Zemlepakhtinskaya Formation

f----1 Poropelonskaya Formation

§ Palvinskaya Formation

f.,. ........ 1 lernovskaya Formation

!IHII Kutovaya Formation

Kildinskaya Group

[JJ] Slantzevoozerskaya Formation

(22l Pridorozhnaya Formation

m Pestzovozerskaya Formation

� Chernorechenskaya Formation

� Bezymyannaya Formation

ITITJ Korovinskaya Formation

� Archaean Basement

Fig. I. Maps showing outcrop areas and sampling localities. A: Map of northern Fennoscandia showing position of map B. B: Map showing the inferred relationship between the Varanger Peninsula, Norway, and the Sredni-Rybachi Peninsula, Russia. C: Geological map of the Sredni-Rybachi Peninsula and Kildin Island. Arrows

and numbers within frames refer to sampled fossiliferous localities. D: Map of the Kola Peninsula showing position of the Sredni-Rybachi Peninsula and the Chapoma

River. Figures JA-C modified from Siedlecka et al. (1995a) and Siedlecka (1995) with permission.

168 J. Samuelsson

all of Sweden with the exception of the Caledonides, southwestern Scania and the southern part of the Baltic Sea. In the area of the western part of the East European Platforrn, the Baltic Shield is overlain by Cambrian and successively younger Phanerozoic strata. Sedimentary Neoproterozoic rocks of the Kola Peninsula and of the Varanger Peninsula in Norway rest disconforrnably on folded and strongly metamorphosed older Proterozoic and Archean rocks (Fig. l C). The Neoproterozoic successions are predominantly terrigenous and contain an abundance of sedimentary structures. The geology of the Sredni Peninsula, the Kildin Island and the Rybachi Peninsula was described by Siedlecka et al. (1995a, 1995b). Below, a short review of the geology of these areas and the Chapoma Forrnation on the Tiersky Coast is given. For completeness, even those units not sampled in the present examination are included in the review.

The Rybachi-Sredni Peninsula is dissected by a northwest-southeast trending fault. The fault has a westward extension on Varanger Peninsula in Northern Norway (Fig. l B). This structural junction between Sredni and Rybachi was interpreted as a reverse fault, where rocks underlying Rybachi have been uplifted and thrust against Sredni (Wegmann 1928, 1929; Lupander 1934; Polkanov 1934, 1936; Keller & Sokolov 1960 and Keller et al. 1963). In contrast, Negrutsa (1971) and Lyubtsov et al. (1989) proposed that there is a stratigraphic relationship between the Kildinskaya Group and the sedimentary succession in Rybachi and they regarded the Rybachi deposits as younger. This interpretation further implies that the Rybachi succession has an age comparable to the Volokovaya Group on Sredni (Lyubtsov et al. 1978). However, re-examination of the key area in the field did not reveal any sedimentary contact and therefore stratigraphic relationship has to be based on other criteria (Siedlecka 1995).

Geology of the Sredni Peninsula

The Kildinskaya Group on Sredni comprises entirely terrigenous deposits referred, in ascending order, to the Kutovaya, Iernovskaya, Palvinskaya, Poropelonskaya, Zemlepakhtinskaya and Karuyarvinskaya Forrnations (Siedlecka et al. 1995a; Fig. 2).

The Kildinskaya Group is unconforrnably overlain in the northwestern part of Sredni by the Volokovaya

Group. This approximately 450 m thick succession is composed of terrigenous rocks. It is not clear if the erosional contact between the Kildinskaya and Volokovaya Groups is an angular unconforrnity, but it is undoubtedly the most conspicuous erosional break within the entire sequence on Sredni (Siedlecka et al. 1995a).

The lowerrnost unit of the Kildinskaya Group on Sredni, the Kutovaya Forrnation, is composed of crossbedded feldspathic sandstones and the overlying Ier

novskaya Forrnation mostly of glauconitic quartz sand-


stones. Both forrnations were previously referred to as the Pjarjajarvinskaya Forrnation (Negrutsa 1971), and were interpreted as deposited in a fiuvial to marine high-energy environment in the lower part, whereas the upper part was probably deposited in a prograding delta (Siedlecka et al. 1995a). The succeeding Palvinskaya Forrnation consists of sandstones and mudstones in its lower part and oncolithic carbonate, dolostone and shale at the top, tentatively interpreted as representing coastal beach and aeolian dune sediments (Siedlecka et al. 1995a). The Poropelonskaya Forrnation rests with an erosional contact on the Palvinskaya Forrnation and

contains a variety of lithologies, including sandstones, conglomerates and muddy and sandy shales. The overlying Zemlepakhtinskaya Forrnation has a somewhat similar composition and, together with the Poropelonskaya Forrnation, was thought to represent a progradational prodelta-delta front (Siedlecka et al. 1995a). The overlying Karuyarvinskaya Forrnation comprises fine-grained terrigenous sediments and carbonates, mainly dolomites. Siedlecka et al. (1995a) interpreted this forrnation as being deposited in a delta plain or a coast of interdistributary bays and lagoons associated with the delta.

The lower part of the Volokovaya Group, the Kuyakanskaya Forrnation, consists of a coarse-grained, poorly sorted polymict conglomerate, overlain by thickbedded quartzitic sandstones, regarded as a succession deposited under fiuvial, coastal marine and, again fiuvial environments (Siedlecka et al. 1995a). The overlying Pumanskaya Forrnation is composed of dark muddy shale with sandy interbeds, displaying a certain cyclicity, interpreted as ba y deposits accumulated as a result of the delta front and beach progradation (Siedlecka et al. 1995a).

Geology of the Kildin Island

The 1ower part of the Kildinskaya Group on Kildin consists of alternating terrigenous and carbonate units, whereas the upper Kildinskaya Group is entirely terrigenous. The succession was interpreted as deposited under transgressive-regressive events (Lyubtsov et al. 1989; Fig. 2).

Approximately 140 m sandstone, siltstones and claystone comparable to the lernovskaya Forrnation on Sredni Peninsula has been found in drill cores from Kildin Island (Lyubtsov et al. 199 l a). The upper Iernovskaya Forrnation crops out only on the southern coast of the island (Fig. IC), where it consists of darkgrey muddy shales. The overlying Korovinskaya Forrnation consists of muddy sandstones and interbeds of stromatolitic carbonates. The entire stromatolitic assemblage on Kildin Island, exclusively represented by bioherrns, was considered as analogous to the Karatavian ( = Upper Riphean R3) type section in the Urals (Raaben et al. 1995). The Korovinskaya Forrnation is con

forrnably overlain by the Bezymyannaya Forrnation,

NORSK GEOLOGISK TIDSSKR!Ff 77 (1997)

composed of siltstones and muddy sandstone with in

terbeds of glauconitic sandstone and oncolithic dolostone

(Lyubtsov et al. 1991a). The succeeding Chernorechenskaya Formation consists of red-coloured, argillaceous rocks, siltstones and limestones. The overlying succession of approximately 180 m thick subgreywackes, muddy sandstones and claystones referred to the Pestzovozerskaya Formation is exposed to the north of the extension area of the previous formations (Fig. l C). The overlying Pridorozhnaya and Slantsevoozerskaya Formations, 600 and 250 m thick respectively, are largely composed of fine- to medium-grained sandstones.

In summary, the Kildinskaya Group is tentatively interpreted as a shallow-marine deposit in the lower 300 m, and as representing parts of prograding deltaic systems in the overlying section (Siedlecka et al. 1995a).

The Korovinskaya, Bezymyannaya and Chernorechenskaya Formations on Kildin Island are thought to correspond to the Palvinskaya Formation on Sredni, whereas the Pestzovozerskaya, Pridorozhnaya and Slantsevozerskaya Formations on Kildin Island are correlated with

the Poropelonskaya and Zemlepakhtinskaya Formations on Sredni (Lyubtsov 1975; Lyubtsov et al. 1989; Fig. 2).

Fig. 2. Simplified

lithostratigraphic sections for

the Sredni and Rybachi

Peninsulas and Kildin

lmst dolomites and limestones

1/) c. :l 2 (!)

a. :::J o "-

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conglomerate

sandstone

siltstone

mudstone and sandstone

sandstone and siltstone

unconformity

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Formations (/) o Q) o c: -"' .r= (.) :E � 1-

Slantsevozerskaya 250

Pridorozhnaya 600

Pestsovozerskaya 1 80

Chemorechenskaya 55 :-:lmst·:· -----------

."..��:v' Bezymyannaya 45 �.l ':l.s�::::

Korovinskaya 55 lmst

lemovskaya 1 40

KILDIN ISLAND


However, no detailed argument for the proposed correla

tion was accommodated by Lyubtsov et al. (1989).

Geology of the Rybachi Peninsula

The bulk of the Rybachi Peninsula is underlain by a Proterozoic succession attaining an approximate thickness of 4000 m, and has been subdivided into the Einovskaya and Bargoutnaya Groups (Fig. 1). The sequence represents a basinal turbidite system overlain by upper slope deposits (Siedlecka 1995; Siedlecka et al. l995b). It shows a higher level of lithification and is more intensely folded than the successions on Sredni Peninsula and Kildin Island (Siedlecka 1975; Roberts 1995). The base of the Einovskaya Group (Fig. 2), the Motovskaya Formation, is mainly composed of coarsegrained deposits including conglomerates and breccias (Siedlecka et al. 1995b). The Motovskaya conglomerate has been altematively interpreted as glacial (W egmann 1928), or as a debris ftow (Siedlecka et al. 1995b). The overlying Lonskaya and Perevalnaya Formations are approximately 2700-m-thick sandstone units that were interpreted as proximal turbidites (Siedlecka et al. 1995b ).

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Formations 1/) o Q) c: o -"' .r= (.) :E � 1-

Tsypnavolokskaya 260 �lmst::::

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Malskaya 250 ;:;r;;;_;;;;;;.

Perevalnaya 2000 .:;-;;;; ;�--��

Lonskaya 700 QQQQQ�

Motovskaya 350 ;ra;;·-;;;·-

Pumanskaya 300 �

Kuyakanskaya 1 50 lill ".11 11 �

Karuyarvinskaya 250 �imst:::: V'-��"'

Zemlepakhtinskaya 500

Poropelonskaya 280

Palvinskaya 1 60

c: .� lemovskaya 200 "'

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Metamorphic basement

Skarbeevskaya Fm

tectonic contact

Island, Murmansk Coast. Figure modified from

Lyubtsov et al. (1989). SRED�-RYBACHUPE�SULA

170 J. Samuelsson

The overlying Bargoutnaya Group is subdivided into the Maiskaya, Zubovskaya and Tsypnavolokskaya Formations. The Maiskaya Formation consists of sandstones, about 250 m thick that are similar to those of the Perevalnaya Formation. It differs, however, by having thick, lens-forming interlayers of block-pebble conglomerate and subordinate shale. The Zubovskaya Formation is a 500-m-thick succession of turbiditic sandstone, conglomerate and shale whereas the Tsypnavolokskaya Formation is made of 200-m-thick sandstone, mudstone and shale.

The Skarbeevskaya Formation underlies the northwest corner of Rybachi Peninsula and is separated from the other formations by a fault. It consists of turbiditic sandstones and siltstones and its stratigraphic position is uncertain.

The changes in sedimentary regimes recorded by various formations on Rybachi were thought to reflect the prograding development of an active continent margin (Lyubtsov et al. 1989). Siedlecka et al. (1995b) considered the sequences on Rybachi Peninsula to represent a proximal turbidite system that developed at the base of an escarpment generated by faulting of the crystalline basement. Furthermore, they viewed the Rybachi succes-sion as deposited at a more active segment of the SE continuation of the Trollfjorden-Komagelva Fault Zone than that accumulated in the northeastern part of the

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Si; El - siltstone ..9 ��1 claystone o -5 :.:i � sandstone and siltstone

Varanger Peninsula in Norway. Fig. 3. Simplified lithostratigraphic section of the Chapoma Formation, Tiersky

Coast. Figure modified from Lyubtsov et al. (1989).

Geo/ogy of the Chapoma River area

A few dispersed Proterozoic rock units, the Turin, Tiersk and Chapoma Formations, occur along the southern coast of the Kola Peninsula (Fig. ID). On palaeontological evidence, the Turin and Tiersk Formations are considered to be Middle Riphean or older (Lyubtsov et al. 1989). The youngest unit, the Chapoma Formation, is exposed along the steep margins of a gra ben on the shores of River Chapoma, on the southeastern coast of the Kola Peninsula (Tiersky Coast; Fig ID). The formation, approximately 250 m in thickness (Fig. 3), consists of red quartz sandstone, siltstone, mudstone and laminated sandy carbonate rocks at the base. The basal mudstones display mudcracks, whereas the carbonates have synaeresis cracks and, additionally, comprise stratiform stromatolites at

some levels. Some carbonate-cemented sandstones with loadcasts and cross-laminated ripples occur at the lower levels of the formation. The top of the formation consists of alternating grey sandstone, siltstone and dark-grey to black shale with halite pseudomorphs (Lyubtsov et al. 1989; pers. obs.). These observations suggest that the Chapoma Formation is a shallow-water sequence.

Chronostratigraphic subdivision

The four-fold subdivision of the Neoproterozoic of Russia includes the Lower {Rl ), Middle (R2) and Upper

Riphean (R3) and Vendian. However, a somewhat different stratigraphic subdivision is also in use (e.g. Chumakov & Semikhatov 1981) which includes an additional unit, Riphean R4 or Kudashian, between the Upper Riphean (R3) and Vendian. The Kudashian (Riphean R4) is defined on the basis of a change in the Riphean R3 assemblage of stromatolites and oncolites. Micropalaeontologically, the Kudashian is rec�gnized by decrease in diversity of the microbiota followed by an increased abundance of tubular microfossils, such as Eomycetopsis psilata (Jankauskas 1982). The type section of the Kudashian R4 strata, the Kudash Group, is situated within the southern Urals and consists of terrigenous, carbonate and sandy-shaly deposits (Chumakov & Semikhatov 1981). In the European part of Russia and in eastern Europe, the Kudashian is closely related to the Upper Riphean R3 (Chumakov & Semikhatov 1981 ). The lower boundary of the Vendian is usually placed where the Laplandian ( = Varangerian) glacial horizon first occurs (e.g. Keller et al. 1977). Sometimes, the base of the Vendian has been defined lower in the sequence, i.e. at the lower boundary of the Kudashian R4 (e.g. Chumakov & Semikhatov 1981; Semikhatov 1991 ), and this has created some confusion. This paper follows Vidal & Siedlecka (1983), who considered beds formerly regarded as Early Vendian in age as

possibly equivalent with Riphean R4 (Kudashian) strata.


As mentioned above, a sedimentological change from

predominantly non-marine fluvial and deltaic into shal

low marine deposits is recorded in numerous successions

in Baltica during Latest Riphean times (e.g. Røe 1975; Siedlecka 1985; Kumpulainen & Nystuen 1985). Often, the change is also observed in the record of microfossil

assemblages (Vidal 1976a, 1981; Vidal & Siedlecka 1983). This event might mark the transition from Upper Riphean R3 to Terminal Riphean R4 age in the Baltica palaeocontinent (G. Vidal, pers. comm. 1996).

Material and methods

Forty-six out of 67 investigated samples of fine-grained siliciclastics and carbonates proved to yield microfossils. Following the name of the formation, the numbers within parentheses refer to the fossiliferous samples within each formation. The microfossils are obtained from the lernovskaya (4), Chernorechenskaya (2), Pestzovozerskaya ( l ), Poropelonskaya (11) and Karuyarvinskaya (2) Formations of the Kildinskaya Group on Kildin Island and Sredni; the Pumanskaya (5) Formation of the Volokovaya Group on Sredni; the Motovskaya (l) and Perevalnaya ( l ) Formations of the Einovskaya Group on Rybachi; and the Skarbeevskaya (4) Formation on Rybachi. Twenty out of 67 investigated samples are from the Chapoma Formation on the Tiersky Coast, of which 15 samples proved to be fossiliferous. Owing to the generally discontinuous nature of the outcrops, neither of the investigated units was sampled in strictly continuous sections.

The microfossils were extracted from the rock samples using the standard palynological technique (Vidal 1988). Strew slides were made using EPOTEK 301 as a permanent mounting medium.

Besides acid macerate, petrographic thin sections were

also made from each sample. Thin sections of mudstones, siltstones, shales and carbonates were cut parallel to bedding. Thin sections of small drill cores of carbon

ate rocks were cut at an approximately 45° angle to the bedding.

Preservation of microfossils (taphonomy)

The majority of the fossiliferous samples derive from black to dark-grey mudstones and shales. The total organic carbon (TOC) content is generally high, with average values of approximately O.l g TOC per g of rock for the Murmansk Coast area (n = 42; Samuelsson; unpublished data). The average H/C ratio for the Murmansk Coast kerogens is 0.49 (n = 13; Samuelsson; unpublished data), a figure that indicates moderate kerogen preservation (Hayes et al. 1983; Strauss et al. 1992), whereas in the Chapoma Formation, the average TOC is 0.14 g per g sample (n = 20; Samuelsson, unpublished data). The corresponding average H/C ratio for the


Chapoma Formation is 0.62, (n = 7; Samuelsson, unpub

lished data). The average TOC and H/C levels indicate

that the microfossils have undergone a modest thermal alteration, and this is further supported by the thermal alteration index (TAl) of kerogens from each sample (see 'Appendix' for details).

The state of preservation of the microfossils from the

Murmansk and Tiersky Coasts is highly variable. As all investigated rocks have undergone thermal alteration, no definitely light-coloured organic matter is found in any of the examined samples. Nevertheless, some samples contain exceptionally well-preserved acritarchs and filamentous sheaths coloured light to dark-brown, with a TAl ranging from 2+ to 3+ (Pearson 1984). Some samples contain kerogenous matter that is significantly more altered, with maximum T AI values. Acritarchs in these thermally altered samples are relatively few and the samples contain quantitatively more structureless sapropellic matter than fossil-rich samples. Additional samples yield microfossils of variegated coloration that indicate variable levels of preservation. Presumably, this could be due to varying levels of structural deformation and/or thermal altera ti on, or alternatively redeposition of microfossils with a different thermal and preservational history. lrradiation from natura! decay of radiogenic isotapes has also been invoked to explain similar characteristics in other sedimentary settings (e.g. Moczydlowska & Vidal 1992).

The taxonomic diversity measured as the total number of taxa in acid-resistant residues is low. The taxonomically richest samples yielded only 12 form-taxa (Fig. 4). This generally corresponds well to most previously reported Upper Riphean microfossil assemblages, although some Late Riphean assemblages show a more diverse taxonomy due to the accounting of microfossils preserved in chert (e.g. the Svanbergfjellet Formation of the Akademikerbreen Group in Svalbard; Butterfield et al. 1994).

Only four taxa, Leiosphaeridia spp., Navifusa majensis, Stictosphaeridium spp. and tubular fossils, Siphonophycus spp., were recovered in examined petrographic thin sec

tions. As with the macerated samples, Leiosph�eridia spp. is also the most common microfossil in the examined thin sections. The specimens of Leiosphaeridia spp. appear to be randomly distributed in all thin sections, an observation that was taken to indicate a planktonic mode of life for these organisms (Vidal & Knoll 1983; Butterfield & Chandler 1992).

Systematic micropalaeontology

The Proterozoic micropalaeontology was impaired by numerous poorly described taxa and burdened with taxonomic inconsistencies. This problem was more recently dealt with in a number of publications (e.g. Xing et al. 1985; Yin 1987; Jankauskas et al. 1989; Fensome et al. 1990; Schopf 1992; Butterfield et al. 1994), resulting in a more unified classification system.

172 J. Samuelsson NORSK GEOLOGISK TIDSSKRIFT 77 (1997)

KILDINSKA VA GRO U P VOLOK EIN lernov C her p Poropelonskaya Kar Pumanskaya M Pe Skarbeev

� .... � .... N ..". Ill < r- 00 "' Q N N .., \C <'l .., .., .., .... <'l =:i 00 "' .... r- 00 "' Ill Q � \C Q '9 '9 '9 '9 ";' ";' ";' ";' ";' \C � � N '? '? � � N � � � � '? ..". .... ";' ";' �

MICROFOSSIL TAXA ";' ,..!. ,..!. 'o:t Ill .., .... ,..!. .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ,..!. .... .... � "' � � "' "' "' � "' "' "' "' "' .... "' "' "' "' "' � "' "' !:n rn rn rn "'

� � � "' � � � � � � � � � "' � � � � � � � < < < < � � �

C/maria circularis • Leiosphaeridia spp. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Lophosphaeridium laufeldii • • Loplwsphaeridium ? laufeldii • • Navifusa majensis • • • • • • • • • • Oscillatoriopsis spp. • • • • Satka sp. • • • • • Satka colonialica • • • • • • Simia sp. • • • • • • • • • Simia annulare • • • • • • • • • • • Sip/wnophycus spp. • • • • • • • • Sphaerocongregus sp. • Sphaerocon�re�us variabilis • Stictosphaeridium spp. • • • • • • • • • • • • • • • • • • • • • • • Symphaeridium spp. • • • • • • • • • • • Tasmanites rife_iicus • Trachysphaeridium laminaritum • • Valeria lophostriata • • Vandalosphaeridium sp. • Vandalosphaeridium ?varangeri • Total forms present 6 6 2 2 1 1 1 7 1 7 5 4 5 7 1 1 8 3 2 1 1 12 4 3 4 5 3 2 1 4 1 2 1

Fig. 4. Stratigraphic distribution of microfossil taxa recovered from Kildin Island and the Sredni and Rybachi Peninsulas. Filled circles denote presence of taxa. For

the geographic position of rock units see under 'Geological setting'. Abbreviations: Volok = Volokovaya Gro up; Ein = Einovskaya Group; Iernov = Iernovskaya

Formation; Cher = Chernorechenskaya Formation; P = Pestzovozerskaya Formation; Kar = Karuyarvinskaya Formation; M = Motovskaya Formation; Pe =

Perevalnaya Formation; Skarbeev = Skarbeevskaya Formation.

Traditionally, pre-Phanerozoic carbonaceous microfossils have been examined in either chemical macerates or petrographic thin sections. Usually, fine-grained detrital rocks were examined in macerates, and phosphorite nodules and cherts in thin sections. In addition, microfossils recovered in phosphorite nodules and cherts are usually hetter preserved, often three-dimensionally (e.g. Moczydlowska & Vidal 1 992 and references therein). These differences might result in taxonomic misidentification when dealing with different lithologies for microfossils (Schopf 1 992). Lately, this problem has attracted increased attention and papers dealing with Proterozoic systematic palaeonto1ogy often incorporate both petrographic thin section and macerate examinations (e.g. Knoll et al. 1991; Butterfie1d et al. 1994; Hofmann & Jackson 1994), although, admitted1y, this demands significant concentrations of microfossils per rock volume, at !east for thin-section examination.

The present material consists of forms referred to 23 form-taxa, consisting of two groups, acritarchs (including possible prasinophytes and clustered forms), and tubu1ar microfossils, most probably abandoned cyanobacteria1 sheaths. The taxa are arranged in a1phabetic order. One previous1y described species is transferred to another form-genus (i.e. Lophosphaeridium laufeldii Vida1 comb. nov.). Taxonomically, the assemb1age includes a

number of taxa previously known from Proterozoic successions in Scandinavia, Svalbard, Greenland, Russia, Yakutia and North America (e.g. Vida! 1976a; Knoll & Swett 1985; Jankauskas et al. 1989; Butterfield et al. 1 994; Hofmann & Jackson 1994).

The wall thickness of acritarchs, particularly of Leiosphaeridia spp., and tubular microfossils is usually expressed as 'opaque', 'trans1ucent' or 'medium-walled', etc., without being properly defined (e.g. Hofmann & Jackson 1 994; Butterfie1d et al. 1 994). These characters are subjective because the wall was not measured. Here, the following criterion has been followed: In light of a virtually constant thermal altera ti on index (TAl), the wall-thickness was expressed in relation to the transparency or translucency of the wall. The term 'opaque' refers to the object being nearly impenetrable to transmitted light, whereas 'translucent' implies an object that to a minimum extent transmits the light. 'Medium-walled' thus indicates an intermediate position between both extremes.

In the descriptions below, size is given with the maximum diameter of the measured specimen. Owing to compression, these values were not obtained accurately in some cases as many specimens were distorted and deformed.

With the exception of figured cerebroid Chuaria, deposited at the Institute of Earth Sciences, Lund Univer-


TIERSKY COAST- SOUTHERN KOLA Chapoma Formation

TAXA �

IN

i i l � l � l � lo

i�

IN I � I ; I � I m l o Q c o o o o � � � � � � � �

l l l l l l l l l l l l l l N N N N N N N N N N N N N N æ m m m m ø ø m m m m m m m � � � � � � � � � � � � � �

Chuariasp. • Chuaria circularis • • • Leiosphaeridia spp. •••••••••••••• Navifusa majensis • Simia sp. • • • Simla annulare •• •• • Siphonophycus spp. • • ••••••• • Stictosphaeridium sp. • ••••• Synsphaeridium spp. ••••••••• • Trachysphaeridium • ?laminaritum

Valeriasp. • Valeria lophostriata • Total forms present 2 1 3 2 9 5 4 4 5 6 5 3 3 4

Fig. 5. Stratigraphic distribution of microfossil taxa recovered from the

Chapoma Formation, Tiersky Coast. Filled circles denote presence of taxa.

sity, Sweden, all figured specimens are deposited in collections of the Institute of Earth Sciences, Uppsala University, Sweden, to which collection numbers make reference and indicate the location of specimens in microscopic slides given by an England Finder. Micrographs of figured specimens were taken under interference contrast microscope, using a Leitz Wetzlar microscope with an automatic Nikon UFX-IIA microphotography attachment, Ilford XP2 black and white film exposed at l 00 ASA.

The results from the microfossil examination are summarized and accounted for in Fig. 4 for the formations on the Murmansk Coast and in Fig. 5 for the Chapoma Formation on the Tiersky Coast.

Group Acritarcha Evitt, 1963

Genus Chuaria Walcott, 1899 emend. Vidal & Ford, 1985

Type species. Chuaria circularis, Walcott, 1899 emend. Vidal & Ford, 1985

Chuaria circularis Walcott, 1899 emend. Vidal & Ford, 1985 Fig. 7A, D

See Vidal et al. (1993, p. 390) for earlier synonymies.

1993 Chuaria circularis (Walcott) Vidal & Ford-Vidal et al., p. 390, figs. 3A-D; 4D 1994 Leiosphaeridia jacutica (Timofeev) Mikhailova & Jankauskas-Hofmann & Jackson, p. 22, figs. 16; 17: 1-4 1994 Chuaria circularis Walcott-Butterfield et al., p. 32, figs. 8G-H; 13: G-I 1994 Cerebrosphaera buickii Butterfield et al., p. 30, figs. 12: A-H


1994 Leiosphaeridia wimanii (Brotzen)-Butterfield comb.

nov. in Butterfield et al., p. 42, figs. 13: D-F

1994 Chuaria circularis Walcott-Yin & Sun, pp. 99-100, fig. 4b 1994 Chuaria circularis Walcott-Steiner, pp. 95-101, figs. 1: 4-17; 3: 1-7; 4: 1-4; 8: 2; 9: l -2; 11: 8, lO; 12: 4, Il 1995 Chuaria circularis (Walcott) Vidal & FordHofmann & Rainbird, p. 724, figs. l: 1-6

Material. - Five complete specimens. One additional deformed specimen is attributed to Chuaria sp .

Description. - Acid-resistant, robust, single-walled, carbonaceous vesicle, flattened and circular to subcircular in outline after compaction. Surface psilate, often shows diagenetically introduced wrinkles, textures and compressional folds .

Dimensions. - Vesicle diameter ranges from 266 to 313 Jim. Mean diameter= 292.5 J..Lm (s.d.= 16.7 Jim, n = 5).

Remarks. - The extremely simple morphology of these flattened spherical microfossils presents a significant problem for sound taxonomic treatment. In this paper, I have attributed all larger (> 250 Jim; Hofmann & Jackson 1994) smooth, spheroidal acritarchs to Chuaria circularis following the emendation of the taxon by Vidal & Ford (1985) where C. circularis is distinguished from the genus Leiosphaeridia on the sole basis of its relatively larger size and, in some cases, its relatively thicker vesicle wall. The current use of C. circularis involves various unrelated, possibly biogenic objects (Vidal et al. 1993), and because the biological affinities of C. circularis are unknown, I have avoided a non-biological form-taxonomy with a finer subdivision into genera and species of these larger smooth spheroidal acritarchs. Admittedly, for a detailed morphological description of fossil microbiota, artificial form-taxonomy might prove useful (e.g. Butterfield et al. 1994).

Larger specimens of Leiosphaeridia jacutica (Timofeev) Mikhailova & Jankauskas described in the literature fall under Chuaria circularis as defined by Vidal & Ford (1985).

Occurrence. - Chuaria circularis is well known from numerous Neoproterozoic settings around the globe, e.g. the Chuar Group, Arizona, USA (Walcott 1899; Ford & Breed 1973; Vidal & Ford 1985); the Visingso Group, Sweden (Vidal 1976a); the Uinta Mountain Group, Utah, USA (Vidal & Ford 1985); the Little Dal Group, Canada (Hofmann & Aitken 1979); the Eleonore Bay Group (Vidal 1979) and the Wolstenholme and Dundas Formations of the Thule Group, Greenland (Vidal & Dawes 1980); Pendjari Formation, Benin and Burkina-Faso, West Africa (Amard 1992); Feishui and Huinan Group, China (Zang & Walter 1992b); Miroedikha, Khatyspyt, Mastakh, Khajpakh and Debengdin Formations, Siberia

(Vidal et al. 1993); Svanbergfjellet Formation, Spitsbergen

174 J. Samuelsson

(Butterfield et al. 1994); Arctic Bay, Fabricius Fiord, Society Cliff, Victor Bay, Athole Point, Strathcona Sound

and the Elwin Formations of the Bylot Supergroup, Canada (Hofmann & Jackson 1994); Wynniat Formation of the Shaler Supergroup, Canada (Hofmann & Rainbird 1994); Dengying Formation, Yangtze Platform and Liulaobei, Jiuliqiao, Xiamaling and Changlongshan Formations and the Changcheng Group, North China Platform, China (Steiner 1994). In the present material C. circularis was found in the Chernorechenskaya Formation of the Kildinskaya Gro up of the Kildin Island and the Chapoma Formation of the Tiersky Coast. One specimen attributed to Chuaria sp. derives from the Chapoma Formation

(Figs. 7, 8).

Stratigraphic range. - Most likely Early Neoproterozoic, but see Vida! et al. (1993) for a discussion on the

biostratigraphical implications of the taxon.

Genus Leiosphaeridia Eisenack, 1958 emend. Turner, 1984.

Type species. Leiosphaeridia baltica, Eisenack, 1958

Leiosphaeridia spp. Fig. 7B, C, E

See Jankauskas et al. (1989, p. 69) for synonymies.

Material. - Thousands of specimens in various stages of preservation. As in many other Early Neoproterozoic settings, this taxon is by far the most abundant taxon within the assemblage.

Description. - Acid-resistant, isolated, circular to subcircular, compressed, commonly folded vesicles. Surface smooth to psilate in most cases, but a variety of sculpture patterns are known (e.g. chagrinate, granulate, verrucate). Opaque, robust-walled, thin-walled, single or double-walled forms occur. Elongated compressional folds often present, thus indicating a somewhat rigid vesicle wall. Median splits observed on some specimens.

Dimensions. - Vesicle diameter 10-249 J.Lm. Mean diameter= 21.7 J.Lm (s.d.= 11.3 J.Lm, n = 100).

Remarks. - The chaotic systematics of acritarchs is especially inextricable among Leiosphaeridia spp. as most of them do not possess any diagnostic features other than surface sculpture, size and wall thickness. Furthermore, taphonomically introduced features have in some instances been taken as diagnostic (Hofmann & Jackson 1994). This has created much confusion, and some recent attempts have been made to revise the systematics of this taxon (Jankauskas et al. 1989; Schopf 1992). However, even though the number of leiosphaerid taxa has substantially decreased, the definition of species of Leiosphaeridia depends often only on two biologically inadequate characteristics; size and wall thickness. Size ranges


chosen in, e.g., Jankauskas et al. (1989) are purely arbitrary. Additionally, transitional forms between different

dimensional clusters and vesicle wall thicknesses do occur. In the present material, specimens belonging to the genus Leiosphaeridia have not been identified to the species level, mainly because of the limited number of

true biogenic characters associated with the taxon and its limited biostratigraphic value (Moczydlowska 1991). Larger leiosphaerid acritarchs, however, are attributed to Chuaria circularis.

Clusters of Leiosphaeridia-Iike microfossils are herein described under the genera Stictosphaeridium spp. Timo

feev and Synsphaeridium spp. Eisenack. (See 'Additional microfossils' below).

Occurrence. - Leiosphaeridia spp. has been reported from numerous and world-wide occurrences (e.g. Vida! & Ford 1985; Jankauskas et al. 1989; Zang & Walter 1992a; Moczydlowska 1991, 1992b; Hofmann & Jackson 1994; Butterfield et al. 1994) and in the present material the taxon occurs in all fossiliferous samples and greatly outnumbers other microfossil taxa (Figs. 4, 5).

Stratigraphic range. - Late Proterozoic to Tertiary (Moczydlowska 1991).

Genus Lophosphaeridium Timofeev, 1959 ex Downie, 1963 emend. Lister, 1970.

Type species. Lophosphaeridium rarum Timofeev, 1959 ex Downie, 1963

Lophosphaeridium laufeldii Vida!, 1976 comb. nov. Fig. 7F, H, I

1976a Trachysphaeridium laufeldi Vida! sp. nov-Vida!, pp. 36-38, figs. 21: A-N

1976b Trachysphaeridium laufeldi Vida!-Vida!, fig. 2A 1985 Trachysphaeridium /aufeldi Vidal-Vidal & Ford, pp. 375-376, figs. 7: A-B; D, F

Material. - Four moderately well-preserved specimens. Three more poorly preserved specimens are here attributed to e.f. Lophosphaeridium laufeldii.

Diagnosis. - A species of Lophosphaeridium with vesicle wall covered by numerous small hair-like spines.

Description. - Acid-resistant vesicle, circular to subcircular in outline. Compactional folds present on some speeimens. The surface of the vesicle displays numerous tightly arranged, small conical spines that are visible as evenly distributed small hairs at the outer edge of the specimens.

Dimensions. - Vesicle diameter 28-51 J.Lm. Mean diameter= 33 J.Lm (s.d. = 3.6 J.Lm, n = 4). The conical projections are approximately l J.Lm long.


Remarks. - In his original designation of the spedes

Trachysphaeridium laufeldi Vidal (1976a) noted that the

vesicle surface is tightly covered with very short, conical spines. These short spines are herein interpreted as small tubercles, part of the texture of the vesicle surface. The genus Lophosphaeridium is characterized by its solid tubercles (Downie 1963). Hence, I transfer the species from the genus Trachysphaeridium to the genus Lophosphaeridium (Trachysphaeridium was earlier placed in synonymy with the genus Leiosphaeridia by Jankauskas et al. (1989, p. 70). The orthography of the specific epithet, laufeldi, is corrected according to ICBN (Tokyo Code) Articles 32.6 and 60.11.

Occurrence. - Lophosphaeridium laufeldii has been reported from the Visingso Group, Sweden (Vidal 1976a); the Eleonore Bay Group, Greenland (Vidal 1976b); the Andersby Formation of the Vadsø Group, Norway (Vidal 1981a); the Awatubi Member of the Kwagunt Formation, Chuar Group, Arizona and the Mount Watson and Red Pine Shale of the Uinta Mountain Group in Utah, USA (Vidal & Ford 1985). In the present material the species was recovered in the Karuyarvinskaya Formation of the Kildinskaya Group on Sredni (Fig. 4).

Stratigraphic range. - Upper Riphean (Vidal & Ford 1985)

Genus Navifusa Combaz, Lange & Pansart, 1967.

Type species. Navifusa navis (Eisenack 1938) Combaz et al., 1967

Navifusa majensis Pyatiletov, 1980 Fig. 7G, J, K

See Hofmann & Jackson (1996, p. 14) for synonymies.

Material. - Thirty well-preserved and measured spedmens, more than 50 specimens observed in macerations. Including those in thin sections, 52 spedmens were mea

sured.

Description. - Solitary, acid-resistant, ellipsoida1, nonseptate, smooth, medium-walled vesicles with rounded tips. They occasionally occur in chain-like clusters, flattened due to compaction.

Dimensions. - Vesicle width 16-60 ,um, and vesicle length 41-120 ,um. Mean width= 24.7 ,um (s.d.= 4.84 ,um, n = 29). Mean 1ength = 67.2 ,um (s.d.= 18.7 ,um, n = 30).

Remarks. - This species has an extremely simple morphology and a smooth surface. Jankauskas et al. (1989) placed the genus within the Order Osdllatoriales. However, given the limited amount of characters presently

known to be associated with Navifusa, all attempts to compare it with recent taxa must be regarded as specula-

E ::l ..c +-' C> c· Q)


140

120 -• l

100 l -- � l •

80 -

� 4 •• 60 - •

. �l • 40 - l 20 - Navifusa majensis

o l l l l l o 10 20 30 40 50 60

width J..Lm Fig. 6. Relationship between vesicle length and width for Navifusa majensis

including thin sections (n =52).

tive. Looking at the two-dimensional size distribution diagram (Fig. 6), all measurements plot within a unimodal, single duster. Therefore, only one species is recognized here. The size range as proposed by Jankauskas (in Jankauskas et al. 1989) suggests that specimens recovered

in the present material fall closest to Navifusa majensis.

Occurrence. - Navifusa majensis is known from the Zilmerdak Formation of the Southern Ural foreland in Bashkiria, Russia (Jankauskas et al. 1989); the Strathcona Sound, Society Cliffs and Arctic Bay Formations of the Baffin Island, Canada (Hofmann & Jackson 1994) and the Dundas Formation within the Thule Group, northwest Greenland (Hofmann & Jackson 1996). The present spedmens derive from the Poropelonskaya and Karuyarvinskaya Formations within the Kildinskaya Group and the Pumanskaya Formation within the Volokovaya Group

(Fig. 4). One spedmen was recovered from the Chapoma Formation in the Tiersky Coast (Fig. 5).

Stratigraphic range. - Jankauskas et al. (1989) report a Late Riphean age for the taxon, although similar forms are known from Mesoproterozoic up to Midd1e Devonian strata (Eisenack et al. 1979).

Genus Satka Jankauskas, 1979.

Type species. Satka favosa Jankauskas, 1979

Satka colonialica Jankauskas, 1979 Fig. 9A, B

1979 Satka colonialica Jankauskas sp. nov., pp. 192-193,

figs. 1: 4, 6 1985 Satka colonialica Jankauskas-Vidal & Ford, p. 369, figs. 6: A-F

176 J. Samuelsson

1985 Satka colonialica Jankauskas-Knoll & Swett, p. 468, figs. 53: 4-6, 8 1992a Satka compacta Zang & Walter sp. nov., p. 93, figs. 69: F-H 1994 Satka colonialica Jankauskas-Yin & Sun, p. 107, figs. 5: G, 7: K-L

Material. - Twenty-nine well-preserved specimens, a number of poorer preserved specimens are attributed to Satka sp.

Description. - Acid-resistant, single-walled, flattened envelopes with variable wall thickness. The overall shape is ellipsoidal, circular or complex with an uneven outline. On parts of the envelope, irregularly distributed separate, contiguous, round, quadrate or tetragonal cell-like structures or imprints of cell-like structures occur.

Dimensions. - Dimensions of envelope 32-200 ,um. Size of cell-like structures 9-41 ,um.

Remarks. - Within the present material, at least two forms of the taxon occur; one that is circular in outline, and a second that shows an irregular contour that is inconsistent and variable among the specimens. The irregular shape is here viewed as being a compressed, deformed and degraded variety of the original spherical form. For this reason, I have chosen to place all specimens belonging to the genus Satka within the same species, S. colonialica Jankauskas.

The species Satka compacta was erected by Zang & Walter (1992a) to comprise Satka-like microfossils with spongy lamellae. Judging from their description and their accompanying illustrations, it seems that the 'sponginess' of the lamellae most probably is due to degradation. The species is here placed in synonymy with S. colonialica Jankauskas.

Occurrence. - Satka colonialica is known from Upper Riphean strata in Bashkiria, Russia (Jankauskas et al. 1989); the Chuar Group, Arizona, USA (Vidal & Ford 1985); the Veteranen Group in Spitsbergen (Knoll & Swett 1985); the Bitter Springs Formation of the Amadeus Basin in Australia (Zang & Walter 1992a) and the Liulaobei Formation in China (Yin & Sun 1994). In the present material, the species is found in the Iernovskaya, Chemorechenskaya, Poropelonskaya and Karuyarvinskaya Formations of the Kildinskaya Group on Kildin Island and Sredni Peninsula. Two specimens attributed to Satka sp. were found within the Chernorechenskaya and Karuyarvinskaya Formation of the Kildinskaya Group on Sredni and within the Pumanskaya Formation of the Volokovaya Group on Sredni (Fig. 4).

Stratigraphic range. - Upper Riphean (Jankauskas et al. 1989).


Genus Simia Mikhailova & Jankauskas, 1989.

Type species. Simia simica Mikhailova & Jankauskas, 1989

Simia annulare ('Fim9feev) Mikhailova, 1989, Fig. 9C-F

1969 Pterospermopsimorpha annulare Timofeev, sp. nov. 1989 Simia annulare (Timofeev), emend. comb. nov. Mikhailova in Jankauskas et al., p. 66, figs. 6: 5-8 1993 Simia annulare (Timofeev) Mikhailova-Vidal et al., p. 395; fig. 5: A

Material. - Thirty-nine moderately well-preserved specimens and an additional twenty, more poorly preserved attributed to Simia sp.

Description. - Acid-resistant, rounded to ovoid vesicle, surrounded by an outer thin, spongy equatorial membrane. The inner body is smooth, not folded, generally opaque, although forms with less pronounced thickness and more translucent walls also occur. The outer membrane is translu�ent, psilate to fine-granular. The outer layer is less dense than the inner and of a somewhat variable thickness among some specimens whose outer layer is thinner.

Dimensions. - The diameter of the inner body is 14-63 ,um, the diameter of the entire vesicle is 23-73 ,um. Mean diameter of inner body= 29.9 .um (s.d. = 10.4 ,um, n = 39). Mean diameter of whole vesicle = 36.7 ,um (s.d.= 10.6 ,um, n = 39).

Remarks. - The genus Simia was introduced by Mikhailova & Jankauskas (in Jankauskas et al. 1989). Their definition of Simia is dose to that of the genus Pterospermopsimorpha Timofeev emend. Mikhai1ova & Jankauskas. After having examined the type material, G. Vida1 (pers. comm. 1996) arrived at the conclusion that the two taxa are separated primarily by the arrangement of the outer envelope. Simia, in principle a double-walled sphaeromorph, is entirely surrounded by the outer wall in all directions, whereas Pterospermopsimorpha has its outer wall on1y present in the equatorial position (compare the planet Saturn with its rings). However, it is sometimes difficult to identify and recognize whether the specimen recorded belongs to Simia or to Pterospermopsimorpha. It may therefore be noted that among the microfossils attributed to Simia annulare herein, some might in fact belong to Pterospermopsimorpha insolita (Timofeev) Mikhailova. Most of the specimens here attributed to S. annulare have a thick inner body ( compare Figs. VI: 7-8 in Jankauskas et al. 1989).

The relationship between the overall ( = outer) diameter and the diameter of the inner body is directly proportional (Fig. 8). All observed Simia fall on the same correlation line, indicating that all of the recovered fossils belong to the same taxonomic unit (Fig. 8).


8

H

K


c

F

l

•

Fig. 7. Chuaria circularis Walcott emend. Vida! & Ford, Leiosphaeridia spp. (Eisenack ) Turner, Lophosphaeridium laufeldii (Vidal ) comb. nov. and Navifusa majensis

Pyatiletov. A, D. Chuaria circularis Walcott emend. Vida! & Ford. A. Eastern Coast of Visingsii Island, Sweden. Middle/Upper Visingsii unit, Upper Riphean.

Specimen V 70-317A-I (C39-4). Specimen showing 'cerebroid' features on part of vesicle (Butterfield et al. 1994). Scale bar = 208 pm. D. Kumlaby borehole. Upper

Visingsii unit. Specimen BV 4: 33-1 (R28-2). Another specimen showing 'cerebroid' features on part of the wall. Scale bar = 210 pm. B, C, E. Leiosphaeridia spp.

(Eisenack ) Turner. B. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-23-l (F 34.-4). Thinwalled Leiosphaeridia spp. Scale bar = 20 pm. C. Kildin Island.

Chernorechenskaya Formation. Specimen K91-04-l (B52-4). Specimen showing median split. Scale bar = 20 pm. E. Sredni Peninsula. Karuyarvinskaya Formation.

Specimen K 91-23-2 (Q30). Thick-walled Leiosphaeridia spp. Scale bar = 13 pm. F; H, I. Lophosphaeridium laufeldii Vida! comb. nov. F. Sredni Peninsula.

Karuyarvinskaya Formation. Specimen K91-22-l (T39). Scale bar = 20 pm. H. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-23-l (T35-3). Scale

bar = 20 pm. I. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-23-2 (C29-l ). Scale bar = 20 pm. G, J, K. Navifusa majensis Pyatiletov. G. Sredni

Peninsula. Pumanskaya Formation. Specimen K91-26-l (H45). Scale bar = 20 pm. J. Sredni Peninsula. Poropelonskaya Formation. Specimen K91-l l -2 (S53-3). Scale

bar = 20 pm. K. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-23-l (042-3). Scale bar = 17 pm.

178 J. Samue/sson

80

70 Simia annulare e ::t 60 J-.4 Q)

..... 50 Q) s ro 40

·� "C 30 --ro 20 J-.4

Q)

o 10

o o 10 20 30 40 50 60 70

Diameter of inner body Jlm Fig. 8. Relationship between the diameter of the inner body and the overall

diameter of 39 measured Simia annulare.

Occurrence. Simia annulare was reported by Jankauskas et al. (1989) from Siberia and the Urals, Russia. Vidal et al. (1993) reported the species from the Khajpakh F ormation, Y akutia. In the present material, Simia annulare was recovered from the Iernovskaya, Chernoreehenskaya, Pestzovozerskaya, Poropelonskaya and Karuyarvinskaya Formations of the Kildinskaya Group on the Sredni Peninsula and Kildin Island and the Pumanskaya Formation of the Volokovaya Group on Sredni (Fig. 4). The taxon was also found within the Chapoma F ormation on the Tiersky Coast. Speeimens attributed to Simia sp. were recovered from the same geologieal units as S. annulare (Fig. 5).

Stratigraphic range. - Upper Riphean (Jankauskas et al. 1989; Vida1 et al. 1993).

Genus Sphaerocongregus Moorman, 1974.

Type species. Sphaerocongregus variabilis Moorman, 1974

Sphaerocongregus variabilis Moorman, 1974 Fig. 9G

See Vidal (1976a) and Palacios Medrano (1989) for earlier synonymies.

1985 Bavlinella faveolata (Shepeleva)-Knoll & Swett, p. 462, figs. 51: 3-4 1987 Bavlinel/a faveolata (Shepeleva) Vidal-Knoll & Swett, p. 910, figs. 5: 2-3 1989 Bavlinel/a faveo/ata Shepeleva-Jankauskas et al., p. 54, figs. 18: 7-8 1990a Sphaerocongregus variabilis Moorman-Vi dal & Nystuen, p. 193, figs. 9: A-B, D-E, G-L


1991 Sphaerocongregus variabilis Moorman-Moczydlowska, p. 126, fig. 15: I 1992a Sphaerocongregus variabilis Moorman-Zang & Walter, p. 106, figs. 65: A-H 1992b Sphaerocongregus variabilis Moorman-Zang & Walter, pp. 310-311, figs. 6: C-J, 14: G

Material. - Twenty-one well-preserved and measured specimens. Twenty additional, poorly preserved spectmens are referred to as Sphaerocongregus sp.

Description. - Acid-resistant, spherical or subspherieal duster of numerous tightly, sometimes irregularly packed micrometer-sized spheroidal vesicles. The vesicles are homogeneous in size and appearance. Some of the dusters are surrounded by a thin membrane.

Dimensions. - Diameter of aggregates ranges 13-26 pm. The diameter of the spheroidal vesicles is 0.5-1.2 pm. Mean diameter of aggregate = 17.3 pm (s.d.= 3.95 pm, n = 2 1).

Remarks. - The specimens of Sphaerocongregus variabilis observed herein oeeur within a single sample, deriving from the Skarbeevskaya Formation, a deposit interpreted as turbiditic (Siedlecka 1975; Lyubtsov et al. 1989; Siedlecka 1995). Interestingly, specimens of S. variabilis observed by Mansuy & Vidal (1983) derive from turbiditie deposits, too, as do other observed S. variabilis (e.g. Vidal 1981a; Vidal & Siedlecka 1983; Palacios Medrano 1989; Vidal & Nystuen 1990a). Thus, the speeimens found in the present material might be interpreted in agreement with the idea set forth by Mansuy & Vidal (1983) and other authors (e.g. Knoll et al. 1981; Palaeios Medrano 1989; Vidal & Nystuen 1990a) that these mierofossils were planktonie and grew under harsh environmental conditions. As an alternative, S. variabilis was interpreted as an anoxygenie photosynthetie bacterium occupying H2 S-rich waters of certain stratified suboxic basins (Vidal & Nystuen 1990a), a view that may gain an additional foothold considering reeent appreciation about the environmental conditions of the Proterozoic (Logan et al. 1995).

Recently, Zang & Walter (1992a) established two new taxa, Sphaerocongregus ediacarus Zang & Walter and Sphaerocongregus pertatatakus Zang & Walter. The speeimens depieted show an irregular aggregate shape suggesting a variable level of degradation, even within a partieular specimen. These two species are here regarded as preservational variants of the type species. Zang & Walter (1992) also illustrated some objects in connection with their description of S. variabilis that clearly do not belong to this taxon, figs. 67H-J (not S. variabilis); figs. 20: M-N (probably a non-biogenie object).

Occurrence. - Sphaerocongregus variabilis is well known from occurrences world-wide. For references see Moorman (1974); Vidal (1976a); Knoll et al. (1981);


B

D E

G H


c

l

•

Fig. 9. Satka colonia/ica Jankauskas, Sphaerocongregus variabilis Moonnan and Vandalosphaeridium ?varangeri Vida!. A, B. Satka co/onia/ica Jankauskas. A. Kildin

Island. Chernorechenskaya Formation. Specimen K91-0l-18 pm-4 (M33-l). Scale bar= 29 pm. B. Kildin Island. Chernorechenskaya Fonnation. Specimen K91-0l-18 pm-3 (L43-2). Scale bar= 56 pm. C-F. Simia annulare (Timofeev) Mikhailova. C. Kildin Island. Chernorechenskaya Fonnation. Specimen K91-0l-18 pm-4 (J42-4). Scale bar= 45 pm. D. Sredni Peninsula. Karuyarvinskaya Fonnation. Specimen K91-22-l (G4 6). Scale bar= 20 pm. E. Kildin Island. Chernorechenskaya Fonnation. Specimen K91-0l-18 pm-3 (Z47-4). Scale bar= 2 0 pm. F. Sredni Peninsula. Karuyarvinskaya Fonnation. Specimen K91-23-l (Q47). Scale bar= 20 pm. G. Sphaerocongregus variabilis Moorman. Rybachi Peninsula. Skarbeevskaya Fonnation. Specimen K91-16B-2 (123-2). Scale bar= 28 pm. H, l. Vandalosphaeridium ?varangeri Vida!. H. Kildin Island. Chernorechenskaya Fonnation. Specimen K9 1-0l-18 ,um-3 (Z37-3). Scale bar= 20 pm. l. Kildin Island. Chernorechenskaya

Fonnation. Specimen K91-0l-18 pm-3 (R38). Scale bar= 20 pm.

Mansuy & Vidal (1983); Knoll & Swett (1987); Palacios Medrano (1989); Jankauskas et al. (1989); Fensome et al. (1990); Vidal & Nystuen (1990a, 1990b) and Zang & Walter (1992b). Within the present material, a single sample from the Skarbeevskaya Forrnation of the Rybachi Peninsula yielded S. variabilis Moorrnan and speeimens referred to as Sphaerocongregus sp. (Fig. 4).

Stratigraphic range. - According to Knoll & Swett (1987), Sphaerocongregus variabilis is characteristic of

Vendian assemblages throughout the Northern hemisphere but it is also found, although more scarcely, in the Upper Riphean (Vidal 1976a; Vidal & Nystuen 1990a) and the Lower Cambrian (Knoll et al. 1981; Knoll & Swett 1987; Vida! & Nystuen 1990b).

Genus Tasmanites Newton, 1875.

Type species. Tasmanites punctatus Newton, 1875


Fig. JO. Tasmanites rifejicus Jankauskas. Valeria Jophostriata Jankauskas and Trachysphaeridium laminaritum Timofeev. A. Tasmanites rifejicus Jankauskas. Sredni

Peninsula. Karuyarvinskaya Formation. Specimen K91-23-2 (K39-4). Scale bar= 52 pm. A'. Detail of vesicle surface showing pores. Scale bar= 1 .36 pm. B, C. Valeria

/ophostriata Jankauskas. B. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-22-2 (G42). Scale bar= Il pm. C. Tiersky Coast. Chapoma Formation.

Specimen K92-06-l (T50-2). Scale bar= 15 pm. D. Trachysphaeridium /aminaritum Timofeev. Kildin Island. Pestzovozerskaya Formation. Specimen K91-04-l (J53-3).

Scale bar = 20 pm.

Tasmanites rifejicus Jankauskas, 1978 Fig. l OA, A'

1978 Tasmanites rifejicus Jankauskas sp. nov.

Jankauskas, p. 914, figs. 1: 6-7 1981 Tasmanites rifejicus Jankauskas-Vidal, pp. 49-50

1983 Tasmanites rifejicus Jankauskas-Vidal & Siedlecka, figs. 5: A-B 1985 Tasmanites rifejicus Jankauskas-Knoll & Swett, p. 465, fig. 53: Il 1989 Tasmanites rifejicus Jankauskas-Jankauskas et al. , p.

131

NORSK GEOLOGISK TIDSSKRIFT 77 (1997) Early Neoproterozoic strata, Kola Peninsula 181

Material. - A single moderately well-preserved specimen. tightly arranged roughly hemispherical shallow deptes-

Description. - Acid-resistant, spherical, thick-walled vesicle. Owing to compaction, the vesicle is flattened and the wall folded. The surface of the vesicle is covered in closely arranged pores, giving the vesicle a wavy appearance. The pores are rounded or slightly elliptical; varying

between 0.5 pm and 1.5 pm in diameter and spaced at 2-3 pm intervals.

Dimensions. - The diameter of the vesicle is 130 pm.

Remarks. - Mainly based on ultrastructural evidence, several authors were able to demonstrate that Tasmanites is in fact a prasinophyte (e.g. Jux 1968, 1969; Boalch & Parke 1971; Guy-Ohlson 1988; Boalch & Guy-Ohlson 1992). Regrettably, no ultrastructural investigations were

hitherto performed on Neoproterozoic specimens. Therefore, Tasmanites rifejicus is here kept within the acritarchs.

Occurrence. - Tasmanites rifejicus occurs in the Inzer

Formation in the southern Urals (Jankauskas 1978); the Klubbnasen and Andersby Formations of the Vadsø Group in East Finnmark, Norway (Vidal 198 la; Vidal & Siedlecka 1983); the Jupiter Member of the Galeros Formation and the Red Pine Shale of the Uinta Mountain Group (Vidal & Ford 1985) and the Veteranen Group, Svalbard (Knoll & Swett 1985). The single specimen recovered here derives from the Karuyarvinskaya Formation of the Kildinskaya Group on Sredni (Fig. 4).

Stratigraphic range. - Upper Riphean sensu stricto (Vidal & Ford 1985).

Genus Trachysphaeridium Timofeev, 1966.

Type species. Trachysphaeridium laminaritum Timofeev, 1966

Trachysphaeridium laminaritum Timofeev, 1966 Fig. JOD

See Vida! & Ford (1985, p. 373) for earlier synonymies.

1989 Leiosphaeridia laminarita (Timofeev) Jankauskas comb. nov. in Jankauskas et al., p. 78, figs. 11: 11-13 1992 Leiosphaeridia laminarita (Timofeev) JankauskasZang & Walter, 1992a, p. 64, figs. 52: H; 54: C 1992 Leiosphaeridia laminarita (Timofeev) JankauskasZang & Walter, 1992b, p. 295 figs. 10: H-J

Material. - Two moderately well-preserved specimens. One poorer preserved specimen is here attributed to Trachysphaeridium ?laminaritum.

Description. - Acid-resistant organic-walled vesicles circular to ovoid in outline. The vesicle is thick and dense

and displays an alveolar wall structure, which consists of

sions.

Dimensions. - Vesicle diameter 25-51 pm.

Remarks. - The most prominent characteristic of Trachysphaeridium laminaritum is the alveolar, pseudo-retic

ular surface texture. Jankauskas (in Jankauskas et al. 1989) transferred the species to the genus Leiosphaeridia. Concerning the alveolar vesicle wall structure, two alternatives are plausible: Either the structure is a taphonomic imprint or a diagnostic feature. In regard to the similarity of the alveolar depressions of these specimens to pores of, for example, Tasmanites, the latter alternative seems to be the most probable. Until a taphonomic origin of the alveolar structure is demonstrated, these palynomorphs should in my opinion not be grouped together with Leiosphaeridia spp., but retained within the original genus Trachysphaeridium Timofeev.

Occurrence. - Trachysphaeridium laminaritum has been reported from the Awatubi Member of the Kwagunt Formation and Red Pine Shale of the Uinta Mountain Group (Vidal & Ford 1985); the Visingso Group (Vidal 1976a); the Vadsø Group, Norway (Vidal 198 l a); the Liulaobei, Shijia and Zhaowei Formations, China and the Gouhou Formation, China (Zang & Walter 1992b). For occurrences within Russia and surrounding areas see Vidal (1976a). The two specimens recovered within the present material derive from the Pestzovozerskaya Formation of the Kildinskaya Group on Kildin Island, and

from the Poropelonskaya Formation within the Kildinskaya Group on Sredni (Fig. 4).

Stratigraphic range. - Upper Riphean and Vendian (Jankauskas et al. 1989).

Genus Valeria Jankauskas, 1982.

Type species. Valeria lophostriata (Jankauskas 1979)

Jankauskas, 1982

Valeria lophostriata (Jankauskas, 1979) Jankauskas, 1982 Fig. JOB, C See Hofmann & Jackson (1996, p. 16) for synonymies.

Material. - Eight well-preserved specimens, and one poorly preserved specimen attributed to Valeria sp.

Description. - Acid-resistant, circular to subcircular, organic vesicles with medium wall thickness. The vesicle is covered in a diagnostic polarly arranged, hemispherical sculptural pattern, which consists of parallel, tightly packed striae. The striae are extremely thin, probably less than 0.25 pm.

Dimensions. - Vesicle diameter is 16-100 pm. Mean

diameter= 70.9 .um (s.d. = 25.9 .um, n = 8).

182 J. Samuelsson

Remarks. - The characteristic surface scu1pture of Valeria lophostriata makes it readi1y recognizab1e and very

significant from a biostratigraphica1 point of view (Butterfie1d & Chand1er 1992). However, among the smaller specimens it is sometimes rather difficult to recognize the individual granulae that seem to build up the

striated pattern on larger, fragmentary specimens.

Occurrence. - Valeria /ophostriata occurs within the Zigalgi and Zigazino - Komarovo Formations, southern Urals, Bashkiria ( Jankauskas 1979); the Klubbnasen and

Andersby Formations of the Vadsø Group, Norway (Vidal 198 1a); the Båsnæring and Båtsfjord Formations of the Barents Sea Group, Norway (Vidal & Siedlecka 1983); the upper Visingso Group, Sweden (Vidal & Siedlecka 1983); the Galeros and Kwagunt Formations of the Chuar Group, Arizona, USA (Vidal & Ford

1985); the Wolstenholme and Dundas Formations of the Thule Group, Greenland (Dawes & Vidal 1985); the Agu Bay Formation of the Fury and Hecla Group, Canada (Butterfie1d & Chandler 1992); the Arctic Bay Formation of the Eqalulik Group, the Fabricius Fiord Formation and the Society Cliffs Formation of the Uluksan Group, all of the Bylot Supergroup, Canada ( Hofmann & Jackson 1994) and the White Pine Shale of the Nonesuch Formation, central USA (Vidal, unpublished data). In the present material, the species is known from two samples from the Karuyarvinskaya Formation of the Kildinskaya Group on Sredni and from one sample of the Chapoma Formation on the Tiersky Coast (Figs. 7, 8). The specimen attributed to Valeria sp. was recovered from one sample from the Chapoma Formation.

Stratigraphic range. - Valeria lophostriata is known from Upper Riphean localities world-wide ( Jankauskas et al. 1 989). Additionally, Hofmann & Jackson (1994) reported it from the somewhat older (1270-750 Ma) Bylot Supergroup, Canada. The correct stratigraphic range is probab1y upper Midd1e Riphean to Upper Riphean (Butterfie1d & Chandler 1992).

Genus Vanda/osphaeridium Vidal, 198 1 .

Type species. Vandalosphaeridium reticulatum (Vidal, 1976) Vidal, 1981

Vandalosphaeridium ?varangeri Vidal, 1981 Fig. 9H, I

1981 Vandalosphaeridium varangeri Vi dal sp. nov.-Vi dal, 1981a, pp. 38-39, figs. 18: A-I

1990 Vandalosphaeridium varangeri Vidal-Vidal & Nystuen, 1990a, pp. 197-198, figs. 12: C-C'

Material. - Two poorly preserved specimens are attributed to Vandalosphaeridium ?varangeri. Another specimen in an extremely poor state of preservation is attributed to Vandalosphaeridium sp.


Description. - Acid-resistant organic microfossil consisting of a thick, massive smooth inner body surrounded by

an outer spongy membrane. The membrane is supported

by simple processes.

Dimensions. - Diameter of inner body is 17-21 fliD. Diameter including membrane 21-22 11m.

Remarks. - Two of the specimens show clear similarities to the type species, Vandalosphaeridium varangeri. Owing to their poor preservation, however, these specimens of Vanda/osphaeridium are uncertainly determined to the species level.

Occurrence. - Vandalosphaeridium varangeri was hitherto reported from the Dundas and Nassiirssuk Formation of the Thule Group in East Greenland (Vidal & Dawes 1980); the Ekkerøy, Dakkovarre and Grasdal Formations in Varanger Peninsula, northern Norway (Vidal 1981a) and the Biskopåsen Formation and Moelv Tillite of the Hedmark Group, southern Norway (Vidal & Nystuen 1990a). The specimens in this material derive

from the Chernorechenskaya Formation within the Kildinskaya Group on Kildin Island (Fig. 4).

Stratigraphic range. - Upper Riphean and Lower Vendian (= Terminal Riphean R4; Vidal & Nystuen 1990a).

Additional microfossils

Clustered sphaeromorphs are common in the present material. Most of them are morphologically simple, and seem to be the clustered counterparts to individually preserved Leiosphaeridia spp. Eisenack (1965) erected the genus Synsphaeridium to incorporate smooth leiospheres

20 18

Ill r:: 16 cu a 14

..... V 12 cu ø. ø 10 -o � 8 cu

..0 6 a = z

4 2 o

o

. robustum Siphonophycus

�S.rugosum l �.kestron

10

l l l l l l l l l

20

S. capitaneum 30 40 50

Measured width of compressed filament (J.llll) Fig. 11. Size distribution of tubular microfossils assigned to Siphonophycus spp.

Subdivision of the taxon to species leve! made according to Hofmann & Jackson

(1994).


that are aggregated without any identifiable order. Other

taxa have been described that also incorporate

sphaeroidal microfossils of the leiosphaerid type (e.g.

Symp/assosphaeridium spp.). Symplassosphaeridium is distinguished from Synsphaeridium on the basis of its relatively smaller spheroids and its more regular overall

appearance (Hofmann & Jackson 1994). Stictosphaeridium Timofeev is another genus consisting of small (20-

80 Jl.m across; Jankauskas et al. 1989), thin-walled aggregated spheroids without surface sculpture (Vidal 1976a; Vidal & Ford 1985). Vidal (1976a) regarded Stictosphaeridium spp. as a wastebasket group. As a consequence, Stictosphaeridium spp. might be regarded as synonymous with Leiosphaeridia spp., as no feature ex-

• cept for the clustering habit of Stictosphaeridium separate the two genera.

Within the present material, aggregates that are made up of thick-walled smooth spheroids with crescentshaped longitudinal folds are attributed to Synsphaeridium spp. (Fig. 14A, B), and aggregates made up of thin-walled smooth spheroids are attributed to Stictosphaeridium spp. (Fig. 12C-E). Whenever the same

spheroids are found isolated they are attributed to Leiosphaeridia spp. The taxon Symplassosphaeridium spp. is here regarded as conspecific with Synsphaeridium spp.

As stated by Hofmann & Jackson (1994), both Synsphaeridium spp. Eisenack and Symplassosphaeridium spp. Timofeev have long stratigraphic ranges which make them of less value for biostratigraphy. However, they are significant components in pre-Varangerian acritarch assemblages and are rare in younger strata (G. Vidal, pers. comm. 1996).

The present assemblage contains numerous tubular microfossils, interpreted as sheaths of a bacterial or cyanobacterial origin. All are compressed and unbranched, and the majority are fragmentary and nonseptate. These are attributed to the form-genus Siphonophycus Schopf 1968 (Fig. 12F, G). Some of the sheaths within the present assemblage are septate (Fig.

12H), and are attributed to the genus Oscillatoriopsis Schopf 1968. Butterfield et al. (1994, p. 56) emended the genus Oscil/atoriopsis Schopf and excluded 'pseudo-septate' filaments. The specimens observed herein, however, show no signs of being anything other than truly septate. In the case of Siphonophycus spp., five different form species were recognized in the Bylot Supergroup, Baffin Island, Canada by Hofmann & Jackson (1994) on the basis of arbitrarily chosen sheath widths (see also Knoll et al. 1991). Butterfield et al. (1994) recognized six different species of Siphonophycus based on somewhat different criteria than Hofmann & Jackson (1994). Zang & Walter (1992b) attributed similar tubular fossils to three different genera, as opposed to different species. In this paper, the division by Hofmann & Jackson is followed. Siphonophycus spp. and Oscillatoriopsis spp. are well

known from Late Proterozoic settings world-wide, and are of limited biostratigraphic importance (Hofmann & Jackson 1994). Therefore, I have only attributed speci-


mens of Siphonophycus within the present assemblages to the species level in the size-distribution diagram of

Siphonophycus spp. (Fig. 11). Specimens of Siphonophycus are common in benthic

mat communities (Hofmann & Jackson 1994). Within the samples examined herein, they are found together with presumably planktonic acritarchs, and are at times

clustered into balls. Thus, they are most probably not in situ, an interpretation that might explain why almost all Siphonophycus spp. are fragmentary.

Palaeoenvironmental distribution of microfossils In the Early Neoproterozoic, the ecosystems were probably already complex, but for taphonomic reasons only a minor part of the contributing taxa is preserved in the fossil record (Vidal 1994). Nevertheless, Neoproterozoic rocks representing substantially all marine sedimentary palaeoenvironments contain well-documented and diverse organic-walled microfossil assemblages, including cyanobacteria (Vidal & Knoll 1983; Knoll 1984; Vidal & Nystuen 1990a; Knoll et al. 1991). Present-day organisms have specific preferences concerning habitat, and this is also inferred to exist in the past and demonstrated by spatia! relationship between the distribution of microfossil taxa and lithologica1 facies (e.g. Vidal & Knoll 1983; Mansuy & Vida! 1983; Knoll et al. 1991; Butterfield & Chandler 1992; Butterfield et al. 1994). This feature must be considered before the biostratigraphic significance of recovered microfossil assemblages can be estimated (Knoll & Swett 1985; Butterfield & Chandler 1992). However, the correlation between microfossil distribution, facies and depositional environment ('palynofacies') is not straightforward. The factors affecting the distribution and preservation of fossil microbiotas can be divided into two broad categories; primary {including physical, chemical and biological effects) and secondary (taphonomic) factors.

In present-day environments, primary factors that affeet the distribution of micro-organisms are related to climatic beits, water depth, co2 and oxygen concentrations, nutrient supply, wave and current actions, intraand interspecific competition and physical barriers. The interaction of these factors is comp1ex, and they certainly were important for the pattern of distributions of micro-organisms in the remote past (Knoll et al. 1991; Moczydlowska & Vidal 1992). Therefore, the evaluation of microfossil distributions (especially planktonic) is associated with considerable uncertainties (Moczydlowska & Vidal 1992). Additionally, the fossil record of bacteria and protists is, and must be, incomplete and severely distorted through burial and preservational factors (Vidal & Moczydlowska 1992; Vida! 1994). For instance, not all micro-organisms produce preservable structures; thus some organisms and parts of organisms are more likely to be preserved than others. Certain organic-walled


A B

D

Fig. 12. Synsphaeridium spp. Eisenack, Stictosphaeridium spp. Timofeev, Siphonophycus spp. Schopf and Oscillatoriopsis spp. Schopf. A, B. Synsphaeridium spp.

Eisenack. A. Kildin Island. Chemorechenskaya Formation. Specimen K91-0l-18 pm-4 (K42). Scale bar= 45 pm. B. Sredni Peninsula. Karuyarvinskaya Formation. Specimen K91-22-2 (H5 1-3). Scale bar= 2 0 pm. C-E. Stictosphaeridium spp. Timofeev. C. Tiersky Coast. Chapoma Formation. Specimen K92-06-l (Z4 1). Scale

bar= 36 pm. D. Sredni Peninsula. Poropelonskaya Formation. Specimen K91-l l-l (J55-l). Scale bar= 12 pm. E. Tiersky Coast. Chapoma Formation. Specimen

K92-12-l (P29-2). Scale bar= 1 6 pm. F, G. Siphonophycus spp. Schopf. F. Tiersky Coast. Chapoma Formation. Specimen K92-06-l (E4 4-3). Scale bar= 26 pm. G.

Kildin Island. Pestzovozerskaya Formation. Specimen K91-04-l (Z42-4). Scale bar= 25 pm. H. Oscillatoriopsis spp. Schopf. Kildin Island. Chernorechenskaya Formation. Specimen K91-0l-94 pm-2 (K31-4). Scale bar= 21 pm.

NORSK GEOLOGISK TIDSSKRIFT 77 ( 1 997)

microfossils are composed of a sporopollenine-like material that is mechanically resistant and chemically inert, except to oxidation and carbonization (Martin 1993). The envelopes of other micro-organisms are made of more perishable materials, such as cellulose, which is less likely to be incorporated in the fossil record. This feature tends to distort the record of microbial life (Vidal 1994). The preservational potential of the palaeoenvironment is another important factor to consider. Certain environments (i.e. anoxic) are more favourable for the preservation of organic-walled micro-organisms and organic matter than others (Farrimond & Eglinton 1990; Knoll et al. 1991). The sedimentation rate is also important for the preservational potential of a sediment (Butterfield et al. 1994). In some instances, the preservation of the sediments themselves is the most constraining factor for survival of buried fossils (Veizer 1992). The preservational potential of different facies is highly variable. For example, recrystallized carbonate-dominated facies usually yield very few or no microfossils (Horodyski 1993; Hofmann & Jackson 1994), whereas siliciclastic facies very often contain both diverse and exceptionally preserved microbiota (Zang & Walter 1992a; Jankauskas et al. 1989; Knoll et al. 1991; Horodyski 1993; Martin 1993). My results are consistent with this observation. It should be noted, however, that diagenetic chert and phosphorites often contain exceptionally preserved microbiotas (see Moczydlowska & Vidal 1992 and references therein). Other taphonomic factors negatively affecting the preservation of micro-organisms include biodegradation, mechanical fragmentation and photolysis (Butterfield et al. 1994). For micro-organisms, none of these taphonomic processes are random or even uniform (Knoll & Golubic 1992).

Despite the uncertainties associated with the estimation of factors affecting the spatia! distribution and preservation of microfossils, it is generally agreed that Proterozoic microfossil assemblages are facies dependent (Knoll & Vidal 1983; Knoll 1984; Knoll & Swett 1985; Vidal & Nystuen 1990a; Knoll et al. 1991; Butterfield & Chandler 1992; Hofmann & Jackson 1994; Butterfield et al. 1994), although some examples are known where no clear lithoand palynofacies relationships can be explained

(Moczydlowska 1991; Moczydlowska & Vidal 1992). The sequences on the Sredni and Rybachi Peninsulas,

the Kildin Island and Tiersky Coast examined here can broadly be categorized into three different depositional environments; deltaic, deep-water turbiditic and shallowmarine. It was on1y the fine-grained siliciclastic samples that yielded microfossils (with the sole exception of a phosphorite; see 'Appendix'). Comparison of assemblages from the three environments was thus influenced by energy level and not affected by other sedimentological parameters.

Generally, microfossil preservation has been observed to be relatively good in deltaic settings (Horodyski et al. 1992 and references therein). Siedlecka et al. (1995a) tentatively interpreted the Late Riphean sequences on the


Sredni Peninsula and Kildin Island as constituting various parts of a deltaic system. The microfossil assemblages recovered from these units (i.e. the Iernovskaya, Poropelonskaya, Karuyarvinskaya and Pumanskaya Formations on Sredni and the Chernorechenskaya and Pestzovozerskaya Formations on Kildin Island) are generally more diverse and derive from more fossiliferous samples than those from the turbiditic and shallow-marine settings (Figs. 4-5). In fossiliferous samples, on average 4.84 microfossil taxa were preserved per sample in the deltaic settings in comparison to 1.83 and 4.00 microfossil taxa on average for the turbiditic and shallow-marine settings respectively. Apart from the dominating taxa Leiosphaeridia spp., the assemblages obtained from the deltaic settings yielded a reasonable, if not large, variety of pteromorphic and sphaeromorphic acritarchs and tubular microfossils. Interestingly, the tubular microfossil Oscilla

toriopsis spp. was exclusively recovered in the deltaic type of setting. The modem Oscillatoriaceaean genus Oscillatoria occupies a wide variety of environments, ranging from planktonic freshwater to marine benthic saltmarshes (Carr & Whitton 1982), but just like other cyanobacteria, individual species generally occur in a relatively restricted range of environments (Knoll & Golubic 1992). It is an open question, however, whether the Oscillatoriopsis spp. recovered herein belong to the same species.

The greatest taxonomic diversity among the sections examined is in the Karuyarvinskaya Formation, interpreted by Siedlecka et al. (1995a) as sabkha-type tidal flats associated with deltaic environments. In the Bylot Supergroup, Canada, Hofmann & Jackson (1994) observed a similar pattern, as microfossil species diversity was greatest in shallow-water, i.e. intertidal to supratidal, evaporitic settings. They interpreted their observations as partly reflecting taphonomic factors such as the preservative effects of saline waters.

The stratigraphic section on the Rybachi Peninsula was interpreted by Siedlecka et al. (1995b) as representing a basinal turbidite system overlain by upper slope deposits. Vidal (1979, 1981b) noted a direct correlation between the state of preservation and the energy of the environment and the associated potential for reworking. Thus, if the turbiditic system on Rybachi represents the

environment with the predominantly high, and by comparison the overall highest energy level, the turbiditic sediments should contain relative1y fewer and more poorly preserved microfossils than the lower energy environments do. Six samples from turbiditic settings, mudstones of the Motovskaya (interpreted as a turbiditeassociated olistostrome) and Perevalnaya Formations of the Einovskaya Group and the Skarbeevskaya Formation on Rybachi yielded microfossils. The recovered microfossils in these samples show few microfossil taxa, in a poor state of preservation. However, this might mainly be due to the stronger lithification and more intense folding of the rocks on Rybachi than the rocks on Sredni, Kildin and Tiersky Coast (see 'Geological setting'). Nevertheless, the nature of the recovered micro-

186 J. Samuelsson

fossils from Rybachi is as the reasoning above predicts, which makes the lithification and falding to be the sole factors affecting the composition less probable. Noteworthy, for example, is the Jack of tubular microfossils in the fossiliferous samples from the turbiditic settings on the Rybachi Peninsula. Well-preserved fossils of this type usually occur in near-shore environments and thus should be absent from turbiditic settings (Knoll et al. 1991; Butterfield & Chandler 1992; Hofmann & Jackson 1994). The Skarbeevskaya Formation, also interpreted as turbiditic, is separated from the Einovskaya Group by a fault and it is uncertain whether it is part of the same turbidite system. One sample from the Skarbeevskaya Formation contained Sphaerocongregus variabilis Moorman, a characteristic fossil from other turbiditic settings (see further discussion under S. variabilis in the section on 'Systematic micropalaeontology').

The Chapoma Formation is tentatively interpreted as an intracratonic shallow-water deposit (see 'Geological setting'). In comparison to the other units examined herein, it contains an intermediate diverse microfossil assemblage (Fig. 5). Same taxa recovered from the deltaic settings on the Sredni Peninsula such as Lopho

sphaeridium laufeldii, Satka colonialica, Tasmanites rifeji

cus and Vandalosphaeridium ?varangeri were not recovered from the Chapoma Formation. A possible exp1anation for this observation can be that the sedimentary conditions of the Chapoma Formation did not favour preservation of these taxa, or that the taxa were simply absent in this particular environment. No taxa were found in the Chapoma Formation that were not also recovered from the other settings.

In summary, the correlation between facies, depositional environment and microfossil distribution is partly in accordance with previous observations and suggested models (Vida! & Knoll 1983; Knoll 1984; Palacios Medrano 1989; Vida! & Nystuen 1990a; Knoll et al. 1991; Butterfield & Chandler 1992; Hofmann & Jackson 1994).

The most general models of palaeoecological distribu

tion of microbiota suggest only that low-diversity assemblages of microfossil taxa occur in inshore coastal environments, while higher diversity assemblages indicate more apen shelf conditions (Vida! & Knoll 1983). Other general models attempt to explain differences between microfossil distribution in basinal non-turbiditic and turbiditic sequences (Palacios Medrano 1989; Vida! & Nystuen 1990a). The most detailed models recognize a number of distinct biofacies zones (Knoll et al. 1991; Butterfield & Chandler 1992). The assemblages examined herein are best compared with the more general models, partly because of the limited number of fossiliferous samples and the preservation of the fossil assemblages.

Microfossil provincialism in the Early Neoproterozoic

As discussed above, the distribution of Late Riphean microfossil assemblages is palaeoenvironment- and fa-

NORSK GEOLOGISK TIDSSKRIFT 77 ( 1997)

eies-dependent. However, in disparate sedimentary basins, the same conditions might occur. The question is thus whether there is a correlation between microfossil distribution and large-scale, palaeogeographic settings in the Early Neoproterozoic.

To illustrate the distribution of microfossil taxa in the Late Riphean, a simplified and taxonomically somewhat revised summary of the microfossils obtained from 42 formations within the proximity of Baltica is illustrated (Fig. 13). The data set is roughly divided into passive 'continental margin' and 'intracratonic settings' respectively. The division was made under the assumption that an intracratonic setting represents a more restricted environment than a continental margin does. Thus, if the Early Neoproterozoic micro-organisms were provincial, the distribution of microfossils should be different in the two types of settings.

However, of the reported taxa in Fig. 13, one-third were recovered from a single formation. Of the remaining two-thirds, only six taxa did not occur in both a passive continental margin and intracratonic settings. Taking into consideration that passive continental margin environments dominate on Baltica in comparison to intracratonic settings, no specific microfossil assemblage can be considered as characteristic of any of the two settings (leaving the possibility apen that certain taxa might be). This observation is in agreement with the inferred cosmopolitan nature of most Late Proterozoic microfossils (Vidal & Ford 1985).

Stratigraphy and correlation

The taxonomic evaluation indicates that the recovered microfossils constitute associations comparable with microbiotas reported from Upper Riphean ( = Riphean 3 and 4) rock units of the North Atlantic region and elsewhere (e.g. Vida! 1976 a, 1979; Dawes & Vidal 1985; Knoll 1981, 1982b; Knoll & Calder 1983; Knoll & Swett

1985; Jankauskas et al. 1989; Butterfield et al. 1994). With but a few exceptions, most other authors that have worked in this area have reported similar ages (e.g. Timofeev 1969; Siedlecka 1975, 1995; Vida! 1981a; Vidal & Siedlecka 1983; Lyubtsov et al. 1989). An outline of the stratigraphic positions of the examined Lower Neoproterozoic strata of the Murmansk and Tiersky Coasts and the correlation with same of the most important Neoproterozoic sequences in the proximity of Baltica are depicted in Fig. 14.

On Sredni Peninsula and Kildin Island, the presence of biostratigraphically significant microfossils in samples from the Kildinskaya Group, i.e. Lophosphaeridium

laufeldii (Vidal) Samuelsson comb. nov., Satka colonial

ica Jankauskas, Simia annulare (Timofeev) Mikhailova, Tasmanites rifejicus Jankauskas, Valeria lophostriata Jankauskas and Vandalosphaeridum ?varangeri Vida!, supports Siedlecka's (1995) interpretation of a Late Riphean R3 age for the Kildinskaya Group. The pres-

NORSK GEOLOGISK TIDSSKRIFT 77 ( 1 997) Early Neoproterozoic strata, Kola Peninsula 187

PASSIVE CONTINENTAL MARGIN INTRACRATON

TAXA Murmansk Coast BSR Ny Friesland Nordaust Greenland EFinnmark Ti S E Nor Swed

Kil din V Ein Bar Sea Veteranen A kad Fran Cels Ro L U Eleonore Vadsø Tana Heamark Visingsi:i

l 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Bracl!yplega•wn klumdanum • CTwaria CJrcularis • •••• •• • ? • ? •••• •••• •• • • •• Cymatiosplraeroides spp. • • Dictvotidium {ullerene •

auosospl�aenawm spp. • • Germinosplraera spp. • I..eiosplraeridia spp. •••• • •• • • • •••• •• •• •• • • •• ••• ••• • ••• • •• Lop�;{,�pl!aeridium laufeldii • •• •• •• Naui 1sa majensis •• • ? • Octoedryxium trzmcatum • •• • Oscu/ospl!aera l!yalina • Peteinospltaeridium reticulatum • Plranerosplraerops capita11s • Podolina minuta •

rotosplraeridi�m tu�erw!y,erum • Pterospernwpszmorpl!a mogzleuzca • • • Pterospernwpszmorplra concmtrzca • Pterospernwpsimorpl!a cf. densicoroiiQta •• • • ••

Satka colonia/ica •••• • •• mua annu are •••• • •

Splraeroconff,regus variabilis • • •• ••• •••• • cf. Stiet osp Jaeridium spp. •••• • • • •• • •• •• • ••• • ••• • • • • �nsplraeridium spp. • ••• ••• • • •• • •••• ••• • • •• asmani les �ifejicus ? •• rac zy zystrzc wspl!aera azmika ••

Traclzysplzaeridium sp. • • • • • Traclzysphaeridium apertum • •• •• • . : . Traclzyspal!eridillm limzinaritum

Tracliyspl!aeridillm Ievis •• • • • ••• ••• Trachysr,haeridium timofeeuii • cf. • • ••• ••• Valerza 'thostriata • • • Valkyria area/is • Vandalosphaeridium uarangeri ? • ••• SPHAEROMORFHS INDET • •••• •••• • •• CLUSTERED SPHERES • ••• SPINY ACRITARCHS • • CHROOCOCCALEAN •• • • TUBULAR FILAMENTS ••• • •••• •• • • • • •

Fig. 13. Diagram showing presence of microfossil taxa in a number of Late Riphean formations in the proximity of Baltica. Filled circles denote presence of microfossil taxa, question-mark uncertainty, e.f. denotes provisional identification. Data have been adopted from various sources. The taxonomy of the reported microfossils from the respective formations has been slightly revised mainly according to Jankauskas et al. ( 1 989) and Hofmann & Jackson ( 1 994). Abbreviations: BSR = Barents Sea Region; Nordaust= Nordaustlandet; Ti= Tiersky Coast; S E Nor= Southeastem Norway; Swed = Sweden; V= Volokovaya Group; Ein = Einovskaya Group; Bar Sea= Barents Sea Group; Akad = Akademikerbreen Group; Fran = Franklinsundet Group; Cels = Celsiusberget Group; Ro = Roaldtoppen Group; L= Lower Eleonore Bay Group; U Eleonore= Upper Eleonore Bay Group; Tanafj =Tanafjorden Group. The numbers on the figure refer to the following formations (reference within parentheses): l . lernovskaya (this paper), 2. Chemorechenskaya (thls paper), 3. Poropelonskaya and Pestzovozerskaya Formations (this paper), 4. Karuyarvinskaya (this paper), 5. Pumanskaya (this paper), 6. Motovskaya (this paper), 7. Perevalnaya (this paper), 8. Skarbeevskaya (this paper), 9. Kongsfjord (Vida! & Siedlecka 1 983), 10. Båsnæringen (Vida! & Siedlecka 1 983), I l. Båtsfjord (Vida! & Siedlecka 1 983), 12 . Kortbreen (Knoll & Swett 1 985), 1 3 . Kingbreen (Knoll & Swett 1 985), 14. Glasgowbreen (Knoll & Swett 1985), 1 5. Oxfordbreen (Knoll & Swett 1985), 16. Svanbergfjellet (Butterfield et al. 1 994), 1 7. Draken (Knoll et al. 199 1 ), 18 . Westmanbukta (Knoll 1 982b), 19. Kapp Lord (Knoll l 982b), 20. Flora (Knoll l 982b), 2 1 . Norvick (Knoll l 982b), 22. Hunnberg + Rysso (Knoll l 982b), 23. Lower Eleonore Bay Group (Vida! 1 979), 24. Quarzite series (Vida! 1 979), 25. Multicoloured series (Vida! 1 979), 26. Lower Limestone-Dolomite series (Vida! 1 979), 27. Upper Limestone-Dolomite series (Vida! 1 979), 28. Klubbnasen (Vida! 198 I a), 29. Andersby (Vida! 1 98 l a), 30. Golneselv (Vida! 198 l a), 3 1 . Ekkerøy (Vida! 198 l a), 32. Stangenes (Vida! 198 l a), 33. Dakkovarre (Vida! 1 98 l a), 34. Grasdal (Vida! 198 l a), 35 . Chapoma Formation (thls paper), 36. Brøttum (Vida! & Nystuen 1990a), 37. Biskopåsen (Vida! & Nystuen 1990a), 38. Biri (Vida! & Nystuen 1 990a), 39. Ring (Vida! & Nystuen 1 990a), 40. Lower Visingso Group (Vida! 1 976a), 4 1 . Middle Visingso Group (Vida! 1 976a), 42. Upper Visingso Group (Vida! 1976a).

ence of less biostratigraphically important taxa, i.e. Stic

tosphaeridium spp. in this unit further corroborates the Late Riphean age. The acritarch Valeria lophostriata deserves special attention, as it most characteristically occurs during the first one-third of the Late Riphean (Butterfield & Chandler 1992). In the Kildinskaya Group, it was recovered only from the stratigraphically youngest unit on Sredni, the Karuyarvinskaya Formation. In a preliminary report, Samuelsson (1995) inferred the Karuyarvinskaya Formation as being of Terminal Riphean ( = Kudashian R4) age. Subsequently, Siedlecka (1995) followed this interpretation. However, the presence of Valeria lophostriata within the Karuyarvinskaya Formation points at a younger, Late Riphean R3 age.

The Pumanskaya Formation of the Volokovaya Group on Sredni yielded biostratigraphically significant acritarchs attributable to Satka sp. and Simia annulare

(Timofeev) Mikhailova. Based on lithostratigraphy, the

earlier proposed Terminal Riphean R4 age for the Volokovaya Group cannot therefore be ruled out (Siedlecka 1995). The presence of these two taxa in the Pumanskaya Formation is here interpreted as indicative of a minimum Late Riphean R3 age for the Volokovaya Group.

Regrettably, the microfossils recovered from the two fossiliferous samples of the Einovskaya Group on Rybachi did not yield any biostratigraphically useful taxa (Fig. 4). The same applies to the microfossil assemblage of the Skarbeevskaya Formation, although the presence of the microfossil taxa Stictosphaeridium spp. and Sphae

rocongregus variabilis Moorman is weakly indicative of a Terminal RipheanjVendian age.

The biostratigraphically significant microfossils recovered from the Chapoma Formation, Tiersky Coast, Simia annulare (Timofeev) Mikhailova and Valeria

lophostriata Jankauskas, suggest a Late Riphean R3 age

188 J. Samuelsson NORSK GEOLOGISK TIDSSKRIFT 77 ( 1 997)

M �onostr SREDNI

a units PENINSULA

KILDIN ISLAND

RYBACHI TIERSKY PENINSULA COAST

BARENTS SEA REGION

TANAFJORD- SOUTH-VARANGER- EAST FJORD NORWAY

SOUTH SWEDEN

�LBARD �;R�ARD

EAST 50\JTHERN

FRIESLAND AUSTLANDE1 GREENLAND URALS

510

560

650

680

000-

VOLOKOVAYA GROUP 830±68

Ma

? SKARilEEV� KAYA

FM

?

? LØKVIKFJELLET GRO UP

>640 Ma

Z BER!.O-� GAISSA i;2 KlSTEDAL "'1-----t � DUOLBAS GAISSA

ALUM SHALE fM

'HOl.MIA SERIES�

OSLO BREEN GRO UP 540-550

Ma

KAPPE SPARKE FORMATION CAMBRDOWOVlCIAN ROCKS

0.. BREIVIKA �1-ST-AP-P0---1

V�ÅS :ii'G� ? Z GlEDDE ill[612±18 i!j DRACOISEN �

., SPIAAL CR ZIGAN �� MOELVFM "' '-' � CANYON �--KUK· § r-----

� � � SVFANOR � ��E � =��L

� �±7 � 8 B �N-;;:- � =uffi!C r------t>==s�==�=o=w�

L��J-��r-�EL�OO�BRE�rn�_EsA� CKA�B��G1FJjuEtv�æø�f��KU RG�� H RING FM UPPER

TANA p.. slRI,...-.., V ISINGSO FJORD ;;;) FM....":;[:"' GROUP GROUP 2 fl 707±37 ? tJ .!... Ma 1--------1 � BLS��åiEN �----i,_Z'TB::-':"A:::CCKL::-':"U::":ND::-1 � RYSS

Ø EKKERØY A FM ::E I.IJ TOPPEN � FORMA TION

o �t-:.lli- i!i W co DRAKEN t TYVJOFJELL :X: � FM e BATS- MIDDLE t'; SvANBERG 9

GSO ::!:: FJELLET < - - -FJORD vg�UP as _ � _ fil 0.. FM §l BRØT- O HUNNBERG

� �;rA Q FORMA nON ..: tJ ffi1-----t UPPER < UK ELEONORE � FORMATJON

c:�iJP 688±10 Ma

MIN'YAR FORMATION CHAPOMA 5 gf-OLN--ES-E-Lv-1 TUM ;2 G�\:i��v FORMATION � KILDIN KILDIN FM P:: Cl PADDEBY FM < fM 680-802 l .GROUP GROUP l-::-:-::==-11----i� BÅSNÆR �� 1-----tiiJ 0i.'i'.",." CELSRJS 1----tB-�-� INGEN .... FIJGLE- � c� ... -.oNw ��"ei": oo: Fo RMAnON

1050-619 1015-849 � FM > BERGET 00: "-+-;:FRAN:::-;:::KUN:-;::--l g---

Ill Ma Ma BARGOUT-M"807±119

1-V-LIS-OIN-WG-ESOR-.. -l� �;;; s=: LOW ER � ��R'�

� �� ? KONGS- K�== ? GROUP �-----+-- -----! ELE�..t;,ORE � PO��.'i�N ,..J � "" FJORD 1-L...;BOTN=��'---=---t--------t ? GROUP :.0: m 'MEWAK

basement basement EINOVS- PORMATION KAYA 810±19 ;•-==� 950-1000 88�Ma � basement lbasement Ma

Fig. 14. Stratigraphic correlation diagram of important Late Riphean-Early Ordovician outcrop areas in the North Atlantic Region. The correlations are based on: this paper for the Tiersky Coast and the Skarbeevskaya Formation (Rybachi Peninsula); this paper and Siedlecka ( 1995) for the Sredi Peninsula, Kildin Island and the Rybachi Peninsula; Siedlecka ( 1995) for the Barents Sea Region and the Tanafjorden-Varangerfjorden Region; Vida) & Moczydlowska ( 1995) for the South Central Norway and South Sweden; Hambrey (1982) for Ny Friesland and Nordaustlandet in Svalbard; Vida) (1979), Vida) & Siedlecka ( 1983) and Vida) ( 1985) for East Greenland; Chumakov & Semikhatov ( 1981) and Semikhatov ( 199 1 ) for the southem Urals.

for this unit. On basis of the presence of V. /ophostriata

in both the Chapoma Formation and the Karuyarvinskaya Formation of the Kildinskaya Group on Sredni, the Chapoma Formation and the upper part of the Kildinskaya Group are interpreted as broadly timeequivalent.

Summary

On basis of the recovered microfossil assemblages, the investigated successions can be broadly correlated with Upper Riphean units in Baltica and elsewhere. All recovered microfossils, with the possible exception of Van dalosphaeridium ?varangeri, are cosmopolitan in their distribution. On the Sredni Peninsula and Kildin Island, samples from the Kildinskaya Group yielded the following acritarchs of biostratigraphical importance: Lopho

sphaeridium /aufeldii, Satka colonialica, Simia annulare,

Tasmanites rifejicus, Valeria /ophostriata and Van

dalosphaeridium ?varangeri. With the exception of Valeria

/ophostriata and Vandalosphaeridium ?varangeri, all of these taxa are exclusively known from the Late Riphean R3. Siedlecka (1995) interpreted the Volokovaya Group

on Sredni as Terminal Riphean R4 in age. Based on lithostratigraphy, her age assignment is not directly in conflict with micropalaeontological data that suggest that the Pumanskaya Formation of the Volokovaya Group is of a minimum Late Riphean R3 age. On the Tiersky Coast, the recovered microfossil assemblage from the Chapoma Formation yielded the biostratigraphically significant Simia annulare and Valeria lophostriata. Of these, V. lophostriata probably has the highest correlative potential (Butterfield & Chandler 1992). Mutual presence of V. /ophostriata has herein served as the basis for a tentative correlation of the Chapoma Formation with the Karuyarvinskaya Formation of the Kildinskaya Group on Sredni. Together with results based on other methods (Siedlecka 1995), the biostratigraphically inferred Late Riphean age of the investigated Kola units is fairly well-constrained. Hence, the deposition of these sedimentary successions predate the Varanger lee Age in the North Atlantic Region.

On basis of its possession of short conical spines, Trachysphaeridium laufeldi Vidal is transferred to Lophosphaeridium laufeldii Vidal 1976, comb. nov.

Palaeoenvironmentally, the successions examined herein are considered as deltaic (Sredni Peninsula and


Kildin Island), deep-water turbiditic (Rybachi Peninsula) and shallow-water (Chapoma Formation). The taxonomic diversity and the preservation of the microfossil assemblages differ between the settings. The highest taxc onomic diversity was obtained from the deltaic setting, whereas the shallow-marine setting yielded an intermediate number of taxa, and the turbiditic settings yielded very few taxa and poorly preserved specimens.

Acknowledgements. - This research would have been impossible without the support and encouragement of Professor Gonzalo Vida! and Dr Malgorzata Moczydlowska-Vidal, Institute of Earth Sciences, Micropalaeontological Laboratory, Uppsala. Professor Vida! also initiated the project and introduced me to the fascinating world of Proterozoic microfossils. Professor Anna Siedlecka and Dr David Roberts, Geological Survey of Norway, Trondheim, are thanked for invaluable help and advice. Dr Ulf Sturesson, Bjom Blix (M. Se.) and Magnus Silfversparre (M. Se.), Uppsala, kindly assisted in preparing some of the illustrations. Dr Graham E. Budd, Uppsala, improved the English in parts of the manuscript. Dr V. V. Lyubtsov and Dr V. Z. Negrutsa, Russian Academy of Sciences, Kola Branch, Apatity, Russia, are thanked for assistance in the field. Professor David L. Bruton, Professor Anna Siedlecka and Dr Nicholas J. Butterfield carefully reviewed and commented on the manuscript. To them, I express my sincere thanks. My research was made possible by grants from the Swedish Institute, Otterborgsfonden and the Swedish Natura! Science Research Council (NFR; grants to G. Vida!).

Manuscript received January 1 996

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Appendix - details of investigated samples m ascending order

Numbers within parentheses refer to Thermal Alteration Index (TAl) according to the scale by Pearson ( 1 984). The lower number represents the minimum value in the sample, the higher num ber maximum value. Most T AI values were obtained on specimens of the Leiosphaeridia spp. Data on the fossil con tent of the respective samples are given in Figs. 4 and 5 .

The majority of the samples from Murmansk Coast used in this study were collected during the summer of 1 991 by Dr M. Moczydlowska-Vidal and Professor G. Vi dal. Samples from this collection round were given identification prefixes K9 1-. The remainder of the samples were collected by Professor A. Siedlecka in the summer of 1 993, and were given the prefix AS-. Two phosphoritic conglomerates from the Kuyakanskaya Formation were collected in 1 990, also by Professor A. Siedlecka. Prefix given was K90-.

K90-01A Kuyakanskaya Fm. Phosphorite. Barren. K90-01B Kuyakanskaya Fm. Phosphatic conglomerate. K91-01 Middle Chernorechenskaya Fm. Southern coast of the eastern part of Kildin Island. Thin layer of black shale at lower part of exposed sequence. Synsphaeridium spp. observed in thin section. (3 - , 3 + ) . K91-02 Middle Chemorechenskaya Fm. Southem coast of the eastem part of Kildin, l km from previous spot. Greenish finely laminated mudstone with calcareous concretions laminated as the mudstone. Barren. K91-03 Middle Chemorechenskaya Fm. Southern coast of the eastern part of Kildin, 2 m above previous sample. Thick-bedded greenish and red shale. (2 + , 3 + ). K91-04 Lower Pestzovozerskaya Fm. Southern coast of the eastern part of Kildin, at cliff section of previous locality. Shale. (3, 4- ). K91-05 Upper lemovskaya Fm. Southem coast of the eastern part of Kildin. Thin-bedded mudstone with 'trails'. (3 + ). K91-06 Upper Bezymyannaya Fm. Southern coast of the eastern part of Kildin. Oncolithic and oolithic dolostone. K91-07 Iernovskaya Fm. Sredni, Kutovaya Bay. Mudstone within unclear part of unit. Synsphaeridium spp. observed in thin section. (3 - , 3). K91-08 lemovskaya Fm. Sredni, stream section running into Kutovaya Bay. Mudstone. Synsphaeridium spp. observed in thin section. (3, 3 + ). K91-09 Upper lernovskaya Fm. Sredni, stream section running into Kutovaya Bay. Thin bed of shale between sandstone. (2 + , 4- ; on kerogen). K91-10 Poropelonskaya Fm. Sredni, inland outcrop. Shale. (3). K91-11 Poropelonskaya Fm. Sredni, inland outcrop. Shale. (3 - , 3 + ) . K91-12 Poropelonskaya Fm. Sredni, inland outcrop. Shale. Siphonophycus spp. observed in thin section. (3 - , 3 + ). K91-l3 Zemlepakhtinskaya Fm. Sredni, inland outcrop. Conglomerate with intraformational phosphorite conglomerate. K9t-14 Poropelonskaya Fm. Sredni, Bolshoe Ozerko Bay. Mudstone. Synsphaeridium spp. observed in thin section. (2 + , 4- ). K91-15 Poropelonskaya Fm. Sredni, Bolshoe Ozerko Bay. Mudstone. (3 - , 3 + ). K91-16A Poropelonskaya Fm. Sredni, Bolshoe Ozerko Bay. Mudstone. (3, 3 + ). K91-16B Skarbeevskaya Fm. Northern coast of Rybachi at Cape Kijski near the Skarbeevskaya River. Mudstone within the conglomeratic part of the formation. (4 - , 5; on kerogen, Sphaerocongregus TAl = 3, 3 + ). K91-17 Skarbeevskaya Fm. Northem coast of Rybachi at Cape Kijski near the Skarbeevskaya River. Phosphatic pebble in conglomerate facies. Barren. K91-18 Skarbeevskaya Fm. Northern coast of Rybachi at Cape Kijski near the Skarbeevskaya River. Thin laminated mudstone. Barren. K91-19 Skarbeevskaya Fm. Northern coast of Rybachi at Cape Kijski near the Skarbeevskaya River. Thin bedded mudstone. Barren. K91-20 Skarbeevskaya Fm. Northern coast of Rybachi at Cape Kijski near the Skarbeevskaya River. Mudstone. Barren. K91-21 Skarbeevskaya Fm. Northern coast of Rybachi at Cape Bezimienny. Thin layer of phosphorites. Barren. (5 on kerogen). K91-22 Karuyarvinskaya Fm. Northwestem part of Sredni, opposite the Aynov Islands. Black micaceous shale. (3, 3 + ). K91-23 Karuyarvinskaya Fm. Northwestern part of Sredni, opposite the Aynov Islands. Black micaceous shale. (3, 4 - ).

192 J. Samuelsson

K91-24 Upper Kuyakanskaya Fm. East of Mt. Pummanki, near military installations above cliff, Sredni. Shales and phosphate clasts. Barren. K91-25 Upper Kuyakanskaya Fm. East of Mt. Pummank:i, near military installations above cliff, Sredni. Phosphatic pebbles. Barren. K91-26 Pumanskaya Fm. East of Mt. Pummanki, near military installations above cliff, Sredni. Black siliceous mudstones. Siphonophycus spp. observed in thin section. (3, 4 - ). K91-27 Poropelonskaya Fm. Near Ozerko village, Korobielnyi stream, Sredni. Mudstone. (3 + ). K91-28 Upper Poropelonskaya Fm. A few metres above sample K9 1 -27. Mudstone. (3, 3 + ). K91-29 Poropelonskaya Fm. Coast near to Cape Vestnik, Sredni. Mudstone. (3, 4 - ). K91-30 Poropelonskaya Fm. Coast near to Cape Vestnik, Sredni. Phosphorite. (3, 4 - ). K91-31 Motovskaya Fm. Cape Vestnik area, Sredni. Mudstone in olistrostome. (3, 5). K91-32 Poropelonskaya Fm. Eina Bay, Zelezny Stream, Rybachi. Mudstone. (3 + , 4- ). AS 2/93 Middle Pumanskaya Fm. Exposures in cliffs 1 . 5 km SSW of Cape Zemljanoy, Sredni. Mudstone. (3 + , 4 - ). AS 3/93 Middle Purnanskaya Fm. Exposures in cliffs 1 . 5 km SSW of Cape Zemljanoy, Sredni. Mudstone. (3, 4- ). AS 4/93 Lowermost Pumanskaya Fm. Coastal exposures at a ba y WSW of Cape Zemljanoy, Sredni. Mudstone. Siphonophycus spp. and Navifusa majensis observed in thin section. (3, 3 + ). AS 5/93 Lowermost Pumanskaya Fm. Coastal exposures at a ba y WSW of Cape Zemljanoy, Sredni. Mudstone. Siphonophycus spp. and Navifusa majensis observed in thin section. (3 + , 4- ).

AS 10/93 Zubovskaya Fm. E of Little Cape Skarbeevsky, Rybachi. Mudstone. Barren. (5, on Kerogen). AS 14/93 Upper Perevalnaya Fm. Cape Sharapov, Rybachi. Mudstone. (5).

All samples from the Chapoma Formation on the Tiersky Coast were collected by myself and Professor Vida! during the summer of 1992, and have been given the prefix K92-. The samples were laken at the same locality, the Chapoma River, a few kilometers upstream from the mouth of the river at the White Sea.


K92-0I Altemating red and greyish mudstone. Almost barren. No organic matter observed in thin section. (3). K92-02 Altemating red and greyish mudstone, about l m above previous. Leiosphaeridia spp. observed in thin section. (2 +, 3 - ). K92-03 Thinly laminated organic-rich shale with pyrite, l m above previous. Leiosphaeridia spp. observed in thin section. (3 - , 3 + ). K92-04 Thinly laminated organic-rich shale with pyrite, 120 cm above previous. Leiosphaeridia spp. observed in thin section. (3 + ). K92-05 Laminated carbonate-cemented sandstone (strike N32'W; dip I l 'E). Barren. K92-06 Greyish laminated shale. Leiosphaeridia spp. observed in thin section. (3, 3 + ). K92-07 Carbonate. Pyrite abundant in thin section. K92-08 Carbonate. Pyrite abundant in thin section. K92-09 Stromatolite oriented perpendicular to shoreline N30'W. No organic matter observed in thin section. (3, 3 + ). K92-10 Mudstone, about l m above the stromatolites. Leiosphaeridia spp. observed in thin section. (3, 3 + ). K92-11 Locality 784 in Lyubtsov et al. ( 1991) . Grey shale in altemating mudcracked mudstone; inter bed of a bo ut 1 60 m thickness. (3 - , 3 + ). K92-12 Same as previous, on top of bed. (3 - , 3 + ). K92-13 Locality as previous. Carbonate cemented sandstone. Some parts phosphoritic. K92-14 Locality as previous. Carbonate, 60 cm above previous. Pyrite abundant in thin section. Phosphoritic parts. No organic matter observed in thin section. K92-15 Locality 785 in Lyubtsov et al. (199Jb). Carbonate. K92-16 Locality as previous. Dark grey shale. Pyrite and hematite observed in thin section. (2 + , 3 + ). K92-17 New locality. Thinly bedded dark-grey shale. Leiosphaeridia spp. and organic matter observed in thin section. (3, 3 + ). K92-18 Locality as previous. Black shale interbed. Phosphoritic parts. Pieces of larger sphaeromorphic acritarchs observed in thin section (3, 4- ). K92-19 Locality as previous. Black shale. Leiosphaeridia spp. observed in thin section. Phosphoritic parts. K92-20 Locality as previous. Phosphate. Leiosphaeridia spp. and abundant organic matter observed in thin section. (3 - , 3 + ).

biostratigraphy and palaeobiology of early neoproterozoic ... · biostratigraphy and palaeobiology...

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