Platysolenites, other animal fossils, and the Precambrian-Cambrian transition in Norway SVEN FØYN & MARTIN F. GLAESSNER Føyn, S. & Glaessner, M. F.: Platysolenites, other animal fossils, and the Precambian-Cambrian transition in Norway. Norsk Geologisk Tidsskrift, Vol. 59, pp. 2�6. Oslo 1979. ISSN 0029-196X. The late Precambrian and Lower Cambrian autochthonous sedimentary sequences in northern Norway and adjoining areas and their fossils are reconsidered, and the available specimens are re-described. One Lower Cambrian foraminiferal fossil (Spirosolenites spira/is) and one Late Precambrian medusoid coelenterate (Kullingia concentrica) are named as new genera and species. The thickness changes and breaks in sedimentation in the platform cover compared with the 'miogeosynclinal' Digermul section are demonstrated. Possible biostratigraphic zones, age determinations, and correlations with the Late Precambrian and Early Cambrian fossiliferous rocks of the East European Platform are suggested. S. Føyn, Norges geologiske undersøkelse, Oslo-kontoret, Drammensveien 230, Oslo 2, Norway. M. F. Glaessner, Centre for Precambrian Research, University of Adelaide, Adelaide, South Australia 5000. .The autochthonous or para-autochthonous Late particularly the occurrence of breaks in deposi­ Precambrian-Cambrian sedimentary deposits of tion. Their palaeogeographic and geodynamic Norway may broadly be divided into the follow­ evaluation will have to await further studies on a ing four kinds: wider scale which are beyond the scope of this Miogeosynclinal sediments of eastern Finn­ contribution. mark, northern Norway, ranging from Riphean Tubes of Platyso/enites antiquissimus Eich­ through Vendian and Cambrian to Tremadocian. wald were found early in this century in the Two tillite formations occur. Dividal Group in Norrbotten (Moberg 1908), · The Dividal Group, formerly also called the Troms (Vogt 1918) and Finnmark (Holtedahl 'Hyolithus Zone', a relatively thin sequence of 1918). Vogt (1924) found Platysolenites antiquis­ platform sediments resting with erosional con­ simus Eichwald in Lower Cambrian beds above tact on the Precambrian crystal-line basement. the sparagmite sequence at Ringsaker in the The Group occurs along the margin of the Mjøsa district of southern Norway (Fig. l, loe. Caledonian mountain range in the districts of l). Norrbotten (Sweden), Enontekis (Finland), Because of the thrust plane, the Dividal Group Troms and Finnmark (Norway). It is everywhere is not geographically continuous with the confined upwards by thrust planes of Caledonian miogeosynclinal sediments of the Laksefjorden, age. Tanafjorden and Varanger areas. The four infor­ The 'sparagmite' sequence of southern Nor­ mal members I, Il, Ill and IV of the Dividal way, considered to be deposited mainly in basins Group at Halkkavarre (FØyn 1967) have - formed by faulting. One glaciogenic unit occurs, member to member - a striking resemblance to the Moelv Tillite, generally accepted as an equi­ the three members of the Stappogiedde Forma­ valent of the Upper Tillite of Finnmark. The tion and the lower part of the Breivik Formation. sparagmite sequence is overlain by beds contain­ The lowermost member of the Stappogiedde ing Lower Cambrian fossils. Formation, the Lillevatn Member (Banks 1970), Cambrian strata resting with erosional contact follows the Mortensnes Tillite Formation ('Up­ on the Precambrian crystalline basement of per tillite') with transitional beds. Guided by the southern Norway. lithologies, Føyn in 1966 succeeded in finding We have attempted to add detail and clarity to Platysolenites antiquissimus Eichwald in the this agreed broad stratigraphic framework and to Breivik Formation at Kunes (Fig. l, loe. 6, see indicate by means of stratigraphic and also Føyn 1%7). The correlation thus made was palaeontological evidence the possibilities of later confirmed by Banks' work on trace fossils dating and correlation of its subdivisions and (Banks 1973). 26 S. Føyn & M. F. Glaessner NORSK GEOLOGISK TIDSSKRIFT l (1979) Fig. l. Localities on the Scandinavian Peninsula represented on Figs. 2 and 3 and in the text. The thick line indicates the eastern erosional border of the Caledonides. Symbols: M-Mjøsa, D-Dividal, P-Porsangerfjorden, L-Laksefjorden, T-Tanafjorden, V-Varangerfjorden. I-Ringsaker, 2-Tornetrask, 3-Ruogooaive and Dorrovarre, 4-Avevagge, 5-Halkkavarre, 6-Kunes, 7-Di­ germul halvøya, 8-Eastern Tana. The localities 2-5 represent the Dividal Group. In 1967 Føyn found Platysolenites also at The Platysolenites speeimens eolleeted by eastern Tana (east of Tanafjorden, Fig. 1, loe. 8) Føyn at Halkkavarre (Fig. l, loe. 5) and Kunes (FØyn 1967, 'Addendum': 78) and in 1969 Banks in 1966 were deseribed by Hamar (1967). The found Platysolenites on Digermul halvØya (loe. eolleetion of fossils made in l %7 from Kunes 7) on the west side of Tanafjorden (Banks and eastern Tana is examined and deseribed by 1970). In both those areas the Platysolenites Glaessner in the present paper, together with horizon is situated about 150 m above the base of most of Vogt's speeimens. Some speeimens de­ the Breivik Formation. seribed by Hamar have been re-examined. NORSK GEOLOGISK TIDSSKR!Ff l (1979) Platysolenites and other animalfossils 27 sp., and Lingulella sp.', thus corresponding to Stratigraphy the uppermost part of the Lower Cambrian of southern Scandinavia. The alum shale formation Th e Dividal Group - a link between is considered to be of Middle Cambrian age Finnmark and southern Scandinavia (Kulling 1964: 142). The total thickness of the four units of the Of very great importance are the fossils found Dividal Group at Halkkavarre (loe. 5) is 230 m. It by Kulling during the years 1959 to 1966 in the decreases towards the southwest through Finn­ Middle sandstone formation (C) in the mark and Troms to Norrbotten, being at Ave­ Tornetrask area and identified by him as 'Sprig­ vagge (loe. 4) 80 metres (Vogt 1967) and at gia annulata Southcott' (Kulling 1972, figs. 113 Tornetdisk (loe. 2) 50 m (Kulling 1964 , 1972, and 114) . He also records trace fo ssils in the Vogt 1967) . The 'four units' pattern, however, is same unit C and in the underlying unit B. A persistent. 'Problematicum' fo und by Moberg (1908 , pl. l, According to Kulling's and Vogt's description fig. l) in the Lower shale formation (B) has been of the lithologies and to the occurrence of determined by Vida! (1976 b) to be algae of the Platysolenites , the following correlations are genus Vendotaenia Gnilovskaya, considered to evident: be of Vendian age . Vida! mentions that Ven­ Kul/ing Vogt Føyn dotaenia occurs also in unit C. We conclude that Middle shale formation Niveau D Member !V most of the unit C of the Dividal Group at Middle sandstone formation Niveau C Member Ill Tornetrask is of Late Precambrian age, and Lower shale formation Niveau B Member Il consequently also Member Ill at Halkkavarre Lower sandstone fo rmation Niveau A Member l and fu rther the lowermost part of the Mann­ For convenience, Kulling's four informally draperelv Member. named fo rmations as well as Vogt's 'niveaus! will in the following be referred to as units A, B, Th e Precambrian-Cambrian transition in C, and D of the Dividal Group. eastern Finnmark The decrease in thickness towards the south­ west especially applies to the three lowermost The succession of sedimentary rocks on Di­ units. The deposition of the basal unit may have germul halvøya west of Tanafjorden (Fig. l, loe . been moderately diachronous, the beds young­ 7) seems to have been deposited continuously ing during the transgression towards the south fr om the Upper Tillite, including the transition and southwest. from the tillite to the next member. No signs of Platysolenites antiquissimus Eichwald occurs any stratigraphical break have been observed. in unit D. From the same unit Kulling (1964) The stratigraphical distance between the Upper reported the occurrence of Platysolenites Tillite and the Platysolenites horizon is 650 to 700 lontowa Opik, Volborthella tenuis Schmidt, and m, and above this horizon the Lower Cambrian Hyolithes sp. It is not known whether these beds comprise around 1000 m. Transitional beds fossils occur together in the same bed. The trace spanning the Precambrian-Cambrian boundary fo ssil Monocraterion reported fr om the lower­ should be present. most beds is now stated by Kulling to have come Based on trace fossils and on the Platysole­ fr om the overlying 'Upper sandstone formation' nites horizon, Banks suggests that the transition (pers. comm. to .M.F.G.). In addition, Vogt beds comprise the Manndraperelv Member and reports from Iocalities farther to the northeast the part of the Breivik Member below the Torellella sp. and a gastropod 'Straparolina ' sp. Platysolenites horizon (Banks 1970, Banks et al . This fauna zone thus belongs to the lower part of 1971). The base of the Breivik Member seems to the Lower Cambrian. be preferred as the local Precambrian-Cambrian In Norrbotten and Troms the succession con­ boundary , as the Manndraperelv Member is tinues upwards with the following three units of marked as 'Precambrian and ?Cambrian' whilst Kulling (Vogt's terms in brackets): the Breivik beds below the Platysolenites hori­ 'Upper sandstone formation' (E), 'Upper zon are marked 'Cambrian and ?Precambrian'. shale formation' (F), and 'Alum shale formation' Similary, Daily ( 1972) finds it 'logical to extend (G). The upper shale formation (F) has yielded the Lower Cambrian boundary to at !east the the ft>ssils 'Strenuella linnarssoni Kiær, El­ base of the Breivik Formation', as the trace lipsocephalus nordenskioldi Linnarsson, Obolus fo ssil Phycodes pedum · Seilacher is first seen 28 S. Føyn & M. F. Glaessner NORSK GEOLOGISK TIDSSKRIFT l (1979) U Scole Paradoxides :I Metres l Skolitflos Diplo- 1600 i crat erion i Syringo- " 1 morpfla o 1 Cruz iana 0 1500 i Holmia sp. � i � � l .. .. .,o.c 1400 l l :Jg;: ·- oe o u l t----- � ., 1300 Diplo- .oo .. l cra t�rion c; � l Cruziana � -.J l .. 1200 � l o i _, l i 1100 i i l 1000 trace / fossits l " i o 900 l .. _c: thrust rocks / • o o thrust rocks � E ·� => .