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Neoproterozoic Sedimentation on the Rybachi and Sredni Peninsulas and Kildin Island, NW Kola, Russia

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Neoproterozoic Sedimentation on the Rybachi and Sredni Peninsulas and Kildin Island, NW Kola, Russia 52 Anna Siedlecka NGU. BULL 427. 1995 Neoproterozoic sedimentation on the Rybachi and Sredni Peninsulas and Kildin Island , NW Kola , Russia ANNA SIEDLECKA Anna Siedlecka. Norges geologiske undersokelse, Post Box 3006-Lade, 7002 Trondnelm, Norway. Lithostratigraphy and sedimentary Volokovaya Group is missing on Kildin Island facies of the Rybach i and Sredni where the Kildinskaya Group reaches c.1300 m in thickness. The lower Kildinskaya on Kildin Peninsulas and Kildin Island Island is terrigenous-dolomitic and comprises The stratigraphic section of the Rybachi Penin­ several levels with columnar stromatolites. sula represents a c. 4000 m-thick succession subdivided into two groups and several formati­ ons (Fig.2). The bottom of the succession is not Age and stratigraphic relationship exposed, and the top is erosional with no more between the Rybach i and Sredni record preserved . The succession represents a successions basinal turbidite system overlain by upper slope It had been realised for several decades that a deposits . This Rybachi Turbidite System (RTS) fault zone separates the Rybachi and Sredni consists of turbidites, debrites and deposits Peninsulas. It has also been concluded on the accumulated by traction currents and represents basis of postulated field evidence that the a major retrogradat ional succession (Siedlecka Rybachi succession rests unconformably upon et al. 1995 a). Typical for the RTS is the presen­ the Kildinskaya Group of Sredni and is therefore ce of extrabasinal pebbles to boulders of crystal­ stratigraphicaliy younger and probably equiva­ line rocks in turbidites and debrites and in an lent to the Volokovaya Group (Negrutsa 1971 ). olistostrome in the lowermost part of the strati­ The contact between the Rybachi and Sredni graphic section, suggesting an active, faulted rocks is faulted (Roberts 1995, Roberts & Karpuz margin of the basin with nearby exposed, older 1995). There is, however, no field evidence that Precambrian rocks. The abundance of fragments the Rybachi succession is unconformably overly­ of leucocratic granite in the olistostrome , which ing the Kildinskaya Group. Therefore, the are absent in the adjacent basement, suggests Rybachi-Sredni stratigraphic correlation cannot that not only downfaulting but also lateral transla­ be suggested on the basis of field observations tion was involved in the formation of the faulted (Siedlecka et al. 1995 a, b). margin. Transport of the clastic material, as Microfossil assemblages from the pre-Karu­ shown by palaeocurrents, was within the norther­ yarvinskaya part of the Kildinskaya Group sug­ ly quadrant with a predominant easterly deflecti­ gest a Late Riphean (R3) age while the fairly rich on. The Skarbeevskaya Formation is also turbidi­ assemblage of the Karuyarvinskaya Formation tic in its development. It is everywhere in tectonic indicates a Latest Riphean (R4) age for this parti­ contact with the remainder of the Rybachi rocks cular formation (Samuelsson 1995). A Late and therefore can only loosely be compared with Riphean age was also suggested for the the upper parts of the main Rybachi succession Volokovaya Group by Lyubtsov et al. (1989). (Siedlecka et al. 1995 a). More recently, the assemblage recovered from The success ion of the Sredni Peninsula is up to 2000 m thick. It is subdivided into the Kildinskaya and Volokovaya Groups and into BARENTS SEA several formations (Fig. 2). It is predominantly terrig enous , rests unconformably o n the o lder Precambrian crystalline substratum and its top is erosional with no more record preserved . Fluvial, coastal marine and deltaic facies have been recognised (Siedlecka et al. 1995 b). There are several unconform ities in the lower Kildinskaya Group and there is a major subaerial unconfor­ mity with a pronounced topographic relief betwe­ Fig. 1. Location map. en the Kildinskaya and Volokovaya Groups. The NGU - BULL 427. 1995 Anna Siedlecka 53 the Pumanskaya Formation, although poor, yiel­ are of Late Riphean age (Raaben et al. 1995). ded Sitka sp. suggestive of a Latest Riphean All but one of the K-Ar ages on glauconite (R4) age (Samuelsson 1995). Rybachi rocks from the lower Kildinskaya Group are pre­ have yielded a poor microfossil assemblage with Vendian (1050-670 Ma and 619 Ma, all dates are no diagnostic forms preserved (Samuelsson to be found in Siedlecka et al. 1995 b, FigA). A 1995). Lyubtsov et al.(1989) suggested a Late Pb-Pb age of phosphorite concretions present in Riphean age for the Rybachi strata, close to the the basal part of the Volokovaya Group was Riphean-Vendian boundary. On Kildin Island, reported to be 827-860 Ma (V.Z.Negrutsa, writ­ stromatolites in the lower Kildinskaya Group and ten comm. 1989). The concretions are probably Ayno 'll' Islands \ \ "'km, RYBACHI PENINSULA SREDNI PENINSULA KILDIN ISLAND BARGOUTNAYA GROUP VOLOKOVAYA GROUP KILDINSKAYA GROUP h/t ::::;:;:;:;:;:;: ::::::1 Tsypnavolokskaya Fm. §§§§~ Pumanskaya Fm. 111111111111Slanlzevooz ersk aya Fm. I: :::::::::::::::::j Zubovskaya Fm. r ,"":: ' ~';,\-?~I Kuyakanskaya Fm. ~ Prido rozh aya Fm. o 60 ro 0 °0 ° 0 °0°04 Maiskaya Fm. KILDINSKAYA GRUOP F:::0 '0:-::;..:;;j Peslzovozerskaya Fm. EINOVSKAYA GROUP 11 i 11i 11i j 11 Karuy arvlnskaya Fm. I: I: I: I Cherno reche nskaya Fm. ~ 1. • '1 Perevaln aya Fm. F.;. .... •... Zemlepakhtinskaya Fm. I...... A ,.... r"I ...... I Bezy myannaya Fm. ~ ;~ ::;:::; Lonskaya Fm. E--- --:J Poropelonskaya Fm. I~ I : : ~ ~: : ; : ; I ; ,I Korov inskay a Fm. J cr:~:i::: ·:·:·J Motovskaya Fm. b to 1...('I'" Palvinskaya Fm. f: .:.:.:.:·1 lernovskaya Fm. Pjarja· 1:;:;:;:;;;;;:;:;:;;;;;:; 1 /0 0 0 0 0 0 1 KutovayaF rn. } jarvi Fm. Fig. 2. Bedrock geology and lithostratigraphy of the Rybachi and Sredni Peninsulas. The geolo gy is modified from that shown in Negrutsa (1971) and redrafted onto an outline map derived from a Landsat-TM satellite image (Roberts & Karpuz 1995). 54 Anna Siedlecka NGU • BULL 427. '995 redeposited from the Kildinskaya Group . Rb-Sr­ Correlation with the Neoproterozo ic dated detrital illite in the Volokovaya Group is sections of the Varanger Peninsula c.900 Ma and diagenetic iIIites from the The previously suggested continuation of the Kildinskaya and Volokovaya Groups show a Trollfjorden-Komage lva Fault Zone (TKFZ) of the Vendian age of c.610-620 Ma (Gorokhov et al. Varanger Peninsula across the isthmus betwee n 1995). In summary, the radiometric ages suggest Rybachi and Sredni is well documented by new a Late Riphean rather than Vendian time of sedi­ evidence (Roberts 1995, Roberts & Karpuz mentation . CHR0- BARENTS TROLLFJ.- TVR & GAISSA RYBACHI SREDN I KILDIN Ma NOSTR SEA REGION L.MOLVIK NAPPE CPX PENINSULA PENINSULA ISLAND ci e>: BERLO· er: Cl GAISSA o z a w p10± f-- ? ...J 0 I :::> N I :::l Z a: KISTEDAL a I W UJ < I Cl -c a: I is DUOLBAS· ...J CI) J GAISSA <c, :::E I (Eroded) < ? o L0 KVIK· , BREIVIKA 'E FJELLET , 0 __ __ 1 __ __ c, 40± GROUP Cl STAPPo- ~ -c GIEDDE Z z « 0 -c VESTER· ...a: '-4ORTENSHES '" c 0 TANA w Z ~ 1111 11 111 111 111 11 UJ GROUP w > > NYBORG SMALFJORD '" 'E 50± 8 \1111 Will ~ -<t \ 0 a: c TANA· 'E o Z TANA· 0 -c FJORDEN FJORD. u - UJ GROUP GROUP ~ I VOLOK0- a n, 0 VAYA N a: c GRO UP ...J a -c EKKEA0YA FM. EKKER0YA Z a: ~ TYVJOFJ. UJ a: UJ FM. f- f- II1II II III III a BATSFJ TYVJOFJ & FM. BATSFJ FMS. f-- EQUIVALENTS p80± a: ~ a.. Q. ~ :x.NESELVA a Q. Cl :::> UPPER PADOEBY BASNIl:R· UJ 1f BASHIl:R- ~ Cl INGEN FM c Z INGEN , « ANDERSBY M -c FM , > a: w r KIL- KIL- (/) I FUGLE· DINSKAYA DINSKAYA z (/) ? BERGET < ...z GROUP GRO UP UJ w (not exposed) I a: KLUBBNASEN BARGOUT- 0- ~ NAYA er: VEIONES· BOTN GROUP UJ f- < KONGS· I11 11 I1I I11 I11 ...J FJOR0 EINOVSKAYA FM. GRO UP OOOi r-- ? basement ? basement basement Fig. 3. Slral igraphic correlation table of areas from Varanger Peninsula in the northwest to Kildin Island in the southeast. NGU - BULL 427, 1995 Anna Siedlecka 55 1995). The Rybachi Turbidite System is broadly fall in the time interval between the Kildinskaya comparable to and stratigraphically correlative and Volokovaya and in pre-Ekkeroya time, and a with the Upper Riphean Kongsfjord Submarine possible reactivation of the marginal fault, were Fan of the Barents Sea Region (BSR) of followed by a new period of onlapping, shallow Varanger Peninsula (Figs. 1, 3). sedimentation on Sredni and in the TVR. Correlation of the stratigraphic succesion of Sredni with that of the Tanafjorden-Varanger­ Acknowledgement fjorden Region (TVR) of Varanger is not straight­ The author is grateful to Johan Petter Nystuen for his critical forward.Traditionally, the Volokovaya Group was comments on the manuscript. correlated with the Varangerian glacial record, primarily because of the pronounced unconfor­ References Gorokhov, I.M" Turchenko, T.L., Baskakov, A,V" Kutyavin, mity at the bottom of both succesions. The Late E.P., Melnikov, N.N. & Sochava, A.A. 1995: ARb-Sr stu­ Riphean age of the Kildinskaya and Volokovaya dy of multistage illite generation in shales of the Groups makes this correlation questionable, Pumanskaya and Poropelonskaya Formations, Sredni Correlation between the bulk of the Late Riphean Peninsula, NWKola Region. (Extended abstract). Nor.geol.unders. Special Publ. 7, 00-00. Vadse Group of the TVR and the Kildinskaya Lyubtsov, V.V., Mikhailova, N.S. & Predovsky, AA 1989: Group is suggested instead, and the pre­ Uthostratigraphy and rnicrotossils of the Late Precambrian Ekkeroya and pre-Volokovaya stratigraphic bre­ of the Kola Peninsula. AN SSSR , Kola Branch, 129 pp. (in aks are considered equivalent. This means that Russian). Negrutsa, V.Z.1971: Straligraphy of the Hyperborean deposits the Volokovaya Group might be broadly correlati­ of the Sredni and Rybachi Peninsulas and the Kildin Island. ve with parts of the Tanafjorden Group (Fig. 3). In: Problems of Precambrian Geology of the Baltic Shield A previously suggested correlation between and the Russian Platform cover.
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