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Dinoflagellate Cysts and Acritarchs from Franz Josef Land, Arctic Soviet

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Dinoflagellate Cysts and Acritarchs from Franz Josef Land, Arctic Soviet Bathonian and Callovian (Middle Jurassic) dinoflagellate cysts and acritarchs from Franz Josef Land, Arctic Soviet MORTEN SMELROR Smelror, M. 1987: Bathonian and Callovian (Middle Jurassic) dinoflagellate cysts and acritarchs from Franz Josef Land, Arctic Soviet. Polar Research 5 n.s., 221-238. Well preserved dinoflagellate cyst and acritarch assemblages are recorded from Upper Bathonian and Callovian deposits on Northbrook Island, Franz Josef Land. More than 45 species have been identified. Two new species are proposed: Parvocysta bjaerkei sp. nov., and Meiourogonyaulax spongiosa sp. nov. The recorded marine microfloras are compared with assemblages reported from contemporaneous strata Morten Smelror, Continental Shelf and Petroleum Technology Research Institute Ltd.. P. 0. Box 1883 Jarlesletta, N-7001 Trondheim, Norway; March 1987 (revised August 1987). Franz Josef Land is a group of about 75 islands blages with time-equivalent assemblages recorded situated in the northeastern part of the Barents from the Svalbard archipelago in the western Sea (Fig. 1). Geologically the group bears a close Barents Sea region. relation to eastern Svalbard, whereas it is distinctly different from Novaya Zemlya. The samples included in this study are from North- The Jurassic strata of Northbrook brook Island, one of the southernmost islands Island within the archipelago. Jurassic and Early Cretaceous palynomorph The Jurassic deposits are chiefly situated in the assemblages have been recorded from Franz Josef southern part of the Franz Josef Land group. A Land by Romanovskaya (in Dibner & Shulgina stratigraphic survey of the marine Middle and 1960) and Smelror (1986). Romanovskaya Upper Jurassic deposits in Franz Josef Land was described assemblages characterized by high given by Dibner & Shulgina (1960). At Cape abundance of conifer pollen and large quantities Flora on Northbrook Island the Middle Jurassic of Bennetittalean and Ginkgophytes pollen from strata reach a maximum thickness of 157111. A argillaceous rocks containing Arcficoceras sp. sketch of the Cape Flora section was published (Mucrocephdites sp.). Only the spore-pollen already in 1900 by F. Nansen (Fig. 2). However, composition of these Middle Jurassic deposits on Dibner & Shulgina (1960) argued that some of Hocker Island were listed, and no marine paly- the fossils of the Nansen collection from Cape nomorphs were mentioned. Smelror (1986) listed Flora were misidentified by Pompeckj (1900), 41 species of dinoflagellate cysts, acritarchs, and consequently that the proposed ages for the pollen, and spores contained in six samples from strata were erroneous. Cape Flora and Windy Gully on Northbrook On Cape Flora, Upper Aalenian and Bathonian Island. However, this study had no stratigraphic deposits rest with small angular unconforrnity on control of the Jurassic erratic samples which the continental arenaceous sediments of Lower Jur- author suggested were of Callovian and possibly assic age (Dibner & Shulgina 1960). The light- Lower Oxfordian age. The objectives of the grey Aalenian alearolites and aleuropelites show present study have been to elucidate more data a visible thickness of 3 m. Apparently resting concerning the marine microflora (partly immediately on these deposits is soft clay with recovered from well-dated strata) from the Late nodules of sandy mark exposed at an interval 7- Middle Jurassic of Franz Josef Land, and to com- 10 m above sea level (Nansen 1900; Dibner & pare the dinoflagellate cyst and acritarch assem- Shulgina 1960). From these deposits a fossil fauna 222 Morten Smelror Fig. i. Map of the Barcnt, Sca Region. Location of Northbrook Idand within the Franr Josef Land archipelagu is indlcated by arrow Fig. 2. Sketch of the Cape Flora section. I. Thin alternating strata of band with black car- boniferous seams. ?. Lower- \ - 350m most fossiliferous horizon of soft clay with nodules of sandy 7 -?Z-l marl. 3. Middle fossiliferous 6 horizon of soft stratified clay with hands of phosphatic and calcareous nodules. 4. Upper -ZJJm fossiliferous horizon of soft C clay. with hand of nodules of clav-sandstone. 5. Horizon of soft clay. 6 and 7. Plant-hearing beds of shale and sandstone between hcds of shale and sand- \ stone between the successive Bathonian and Callovian dinoflagellate cysts 223 containing Lingula beani, Discina reflexa, together with Pseudocadoceras nanseni, are more Oxytoma (Pseudomonotis) jacksoni, and Hibol- likely to indicate an early Upper Callovian age. ites (Belemnites) cf. beyrichi is recorded. Pom- Just beneath the lowermost basalt, Nansen peckj (1900) suggested a Lower Bajocian age for (1900) recognized two thin non-fossiliferous bands this unit, but Dibner & Shulgina (1960) argued of black shale. A specimen of the Upper Callovian that since these listed fossils occur together with ammonite Quenstediceras Iamberti was found Aalenian species, these forms should be classed enclosed in the basalt. and a specimen of Quen- as Aalenian. steakeras uertumnum was found in the scree close From about 10 to 113m the section at Cape to the uppermost sedimentary layers and the Flora IS covered by scree, but the succeeding 24 m basalt covering them (Nansen 1900). consist of soft, stratified horizontal clays packed According to Newton & Teal1 (1897), the Jur- with phosphoritic concretions and calcareous nod- assic strata found at Cape Gertrude, 34km east ules. The concretions contain fossil faunas con- of Cape Flora, show great similarities to those at sisting basically of bivalves and, to a lesser degree, Cape Flora, even though some more sandy beds ammonites and belemnites. Unidentifiable plant occur (Horn 1932). Windy Gully is located remains also occur. Among the fauna recorded between Cape Flora and Cape Gertrude, but G. from this unit, Pompeckj (1900) identified Macro- Horn who collected the examined material from cephalites kaettlitzi, M. ishamea var. arctica, M. Windy Gully gave no descriptions of the sedi- pila, Cadoceras frearsi, Cadoceras sp., and Bel- mentary strata in that area. emnites sp. According to Pompeckj, these fossils date the clays as Lower Callovian. Later these fossils were reexamined by Spath (1932), who Material and methods placed the ammonites described as Macro- cephalites within the Bathonian genus Arcto- The samples investigated in the present study are cephalites, and also questioned the identification from Cape Flora and Windy Gully on Northbrook of the ammonites described as Cadoceras by Pom- Island. The samples from Cape Flora were col- peckj (1900). According to Spath (1947), the lected by Dr. F. Nansen in 1896 at the end of the genus Arctocephalites is characteristic of the Norwegian North Polar Expedition 1893-96. The Upper Bathonian, while Arkell (1956) regarded samples from Windy Gully were collected by G. both Arctoceplzalites and Cranocephalites as Horn during the Norwegian Expedition to Franz Lower Callovian forms. However, the definition Josef Land in 1930. All samples were later of Arctocephalites as distinctly Upper Bathonian deposited in the collections of Paleontologisk seems to be widely accepted (Dibner & Shulgina Museum, Oslo. Details of stratigraphic levels and 1960; Smith et al. 1976), and the described inter- proposed ages of the samples investigated are val from 113-137 m above sea level at Cape Flora given in Table 1. is here regarded as Upper Bathonian. The samples were prepared by standard tech- The next mappable sedimentary strata are seen niques (see Barss & Williams 1973) at IKU in at a height of 15tL172m a.s.l., above the scree Trondheim. Slides with the figured specimens are that has covered the Bathonian deposits. Here kept in the collections of Paleontologisk Museum, clays are exposed with numerous structures of the Oslo. ‘cone-in-cone’ variety and intercalations of large arenaceous concretions (Nansen 1900; Dibner & Shulgina 1960). From these beds, Pompeckj Dinoflagellate cyst and acritarch (1900) identified the bivalves Pseudomonotis cf. ornata, Pecten lindstroemi, Pecten cf. demissens, assemblages Lima cf. duplicata, Leda cf. nuda, and the All processed samples yielded well preserved ammonites Cadoceras tschefkini, Cadoceras sten- palynomorphs. In general, terrestrially derived oloburn, Pseudocadoceras nanseni, Cylindro- palynomorphs are the most common, exczpt in teuthis subextensa and Pachyteuthis panderi. the samples CF-2 and CF-U from Cape Flora, This fauna was placed in the Middle Cal- where dinoflagellate cysts dominate the total lovian by Pompeckj (1900). but V. I. Bodylyevsky microflora. The number of marine species rec- (Dibner & Shulgina 1960, p. 73) later suggested orded in each sample varies from between 15 and that species assignable to the genus Cadoceras, 32, except in the uppermost sample WG-3 from 224 Morten Smelror Table I. Stratigraphic levels and proposed ages of the investigated samples. Proposed ages Sample Locality Macrofossil assemblage Pornpeckj 1900 Dibner & Shulgina 1960 This study WG1 Windy Gully. 99 rn Upper Bathonian WGZ Windy Gully. 151 rn Upper Bathonian WG? Windy Gully. 165 rn Callovian CFI Cape Flora, 130 rn Arcrocephalires kaerflirzi Lower Upper Upper A. pilaeformis Callovian Bathonian Bathonian CF2 Cape Flora. 135 m A. ellepricur CF3 Cape Flora. 168 rn Cadocerm rrchefhirti Middle Early Upper Early Upper Cadoceras stenolobum Callovian Callovian Callovian Pseudocadoreras nanseni CFC' Cape Flora. crratic Early Upper Callovian Windy Gully, which yielded only three dino- samples. terrestrial palynomorphs are the most flagellate cyst species and two species
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