ISSN 0869-5938, Stratigraphy and Geological Correlation, 2007, Vol. 15, No. 6, pp. 577Ð609. © Pleiades Publishing, Ltd., 2007. Original Russian Text © E.B. Pestchevitskaya, 2007, published in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2007, Vol. 15, No. 6, pp. 28Ð61.

Dinocyst Biostratigraphy of the Lower Cretaceous in North Siberia E. B. Pestchevitskaya Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia Received June 28, 2006; in final form, March 6, 2007

Abstract—The described scheme of the Lower Cretaceous (BerriasianÐBarremian) stratigraphic subdivisions is elaborated based on palynological study of sections in the Khatanga depression, Ust-Yenisei region, PurÐTaz interfluve, and around the Ob River latitudinal segment, the North Siberia. Stratigraphic distribution of micro- phytoplankton studied in detail is used to distinguish 10 biostratigraphic units in the rank of dinocysts zones. Stratigraphic position of the zones is determined with confidence using data on the Lower Cretaceous reference sections in the Khatanga depression, which were principal ones by constructing the Boreal standard zonation. In majority, boundaries of the dinocysts beds are of a high correlation potential and can be regarded as reliable stratigraphic markers, as they are recognizable not only in Siberia, but also in northern Europe and America. DOI: 10.1134/S0869593807060020

Key words: Lower Cretaceous, stratigraphy, dinocysts, Siberia, correlation, northern regions of Eurasia and America.

INTRODUCTION Natural outcrops of the Lower Cretaceous in the Khatanga depression are of special importance for Organic-walled microphytoplankton is widespread elaboration of the Siberian dinocyst scale. The respec- in the Lower Cretaceous deposits of western and cen- tive sections bearing diverse paleontological remains tral Siberia, as experts in palynology noted repeatedly. facilitated construction of the Boreal standard zona- This group of very diverse microfossils includes tions (Zakharov et al., 1997), and the distinguished dinoflagellate cysts (dinocysts), acritarchs, Chloro- palynostratigraphic units have been correlated with phyceae and Zignemataceae remains. A considerable zonal subdivisions of macro- and microfauna. In the stratigraphic potential of dinocysts well studied in tax- Berriasian, Valanginian and Hauterivian intervals of onomic aspect is confirmed by a great amount of data sections in the Nordvik Peninsula, the Anabar Bay east- on their stratigraphic and lateral distribution in Europe, ern coast, their stratigraphic position has been con- Asia and America. At present, dinocysts are broadly in trolled by data on ammonites, belemnites, bivalves and use for a high-resolution subdivision of the Lower Cre- foraminifers (The reference Section…, 1981; Bogo- taceous in West Europe and Canada. In contrast, spe- molov et al., 1983; Zakharov et al., 1983; Bogomolov, cialized investigations of dinocysts from the Lower 1989; Shenfil’, 1992; Marinov and Zakharov, 2001; Cretaceous of Siberia with parallel assessment of strati- Nikitenko et al., 2004). Foraminifers and ammonites graphic value of separate taxa are comparatively rare. have been also identified in borehole section Severo- Hence, new data in this sphere of biostratigraphy are of Vologochanskaya 18 (Nikitenko et al., 2004), while ammonites, foraminifers and bivalves have been a great interest. detected in the lower Valanginian of borehole section Presented in this work are the results of palynologi- Romanovskaya 140 (Zakharov et al., 1999). In bore- cal study of the Lower Cretaceous sections in the north hole section Gorshkovskaya 1017, age of deposits is of western and central Siberia (Fig. 1) and the analysis defined by palynological data only, as faunal remains of stratigraphic distribution of Early Cretaceous have not been found here. dinocysts in northern areas of Eurasia. The results of palynological analysis are used to subdivide in detail MATERIAL AND INVESTIGATION METHODS the respective North Siberian sections, to establish gen- eral succession of the Lower Cretaceous dinocysts This study is based on palynological analysis of the zones, and to define correlation levels recognizable far Lower Cretaceous marine sections extending one beyond Siberia in northern Europe, Greenland and another in vertical direction with partial overlap (Fig. 2). Canada. In total, the analyzed sections span stratigraphic inter-

577

578 PESTCHEVITSKAYA

50° 60° 70° 80° 90° 100° 110° 75° Nordvik section

Anabar R.

Anabar KARA SEA section

Khatanga 70°

Borehole Severo-Vologochanskaya 18

Dudunka

Taz R. 65° Nadym R. Pur R.

Yenisei R.

Borehole Romanovskaya 140

Ob R. Borehole Gorshkovskaya 1017 Surgut 60°

Nizhnevartovsk

0 400 km

Fig. 1. Geographic localities of the studied sections. val from the Berriasian up to the lower Barremian are represented by dark gray shales and sandstones inclusive. In the Khatanga depression, the most com- (Fig. 2). plete succession has been studied in sections of the Nordvik Peninsula, where the Berriasian and Valangin- The lit-par-lit palynological analysis is performed ian deposits are represented by gray clays and aleurites for the majority of sections (Fig. 2). Core samples have (Fig. 2). Sands prevailing in the Hauterivian Stage are been selected for analysis with interval of 0.5 to 2 m intercalated with subordinate aleurite and clay interlay- depending on composition of the rocks: preference was given to clayey and silty sediments usually containing ers of lesser thickness. In section of the Anabar Bay most representative assemblages of palynomorphs. eastern coast, there is exposed only a lower part of the Before palynological analysis, rock samples have been Valanginian. Silty calcareous clays prevailing in this treated in hydrochloric and nitric acids, and in sodium section are intercalated with sandstone interlayers. In pyrophosphate solution. The cadmium liquid (CdI + the Ust-Yenisei region, the upper BerriasianÐlower KI) with specific gravity 2.25 was used to separate Hauterivian succession studied in borehole section heavy fraction of sediments. Not less than 200 grains Severo-Vologochanskaya 18 is composed of gray aleu- were counted in each slide to determine percentage of rites with thin clay and sand interlayers (Fig. 3), and individual taxa relative to total amount of microphyto- there is a general tendency of sandy material increase fossils (spores, gymnosperm pollen, microphytoplank- upward in the section. In the northwestern Siberia, the ton). Boundaries of palynostratigraphic units are sub- Lower Cretaceous successions are studied in borehole stantiated using the following criteria: first and last sections Romanovskaya 140 (BerriasianÐValanginian) occurrences of species and genera, the grown diversity and Gorshkovskaya 1017 (HauterivianÐbasal Barre- of certain genera and families, and increasing percent- mian). The first of these sections is composed of dark- age of particular taxa (as additional indication). A spe- colored shales in its lower part and of alternating silt- cial attention was paid to stratigraphic distribution of stones and sandstones in the upper one (Fig. 4). The taxa most important for determination of biostrati- HauterivianÐBarremian deposits of the second section graphic boundaries. First or last occurrence of such a

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007

DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 579 taxon at the boundary of biostratigraphic unit corre- Zakharov et al., 1999), and around the latitudinal seg- sponds respectively to its oldest or latest datum level ment of the Ob River (Pestchevitskaya, 2005a). not only in North Siberia, but also in other regions. Comprehensive study of the dinocysts’ morphology To detect taxa of this kind, distribution of nearly was used to clarify characterization of certain taxa, to 300 dinocyst species have been analyzed in Lower Cre- analyze their facies and paleogeographic distribution, taceous sections of Siberia (data on the studied sec- and to describe new species (Pestchevitskaya, 2001, tions), northern Europe and America (published data). 2003, 2006a, 2006b). Stages of dinocysts’ development Species of greatest interest for the Lower Cretaceous in the Cretaceous seas of Siberia were identified, lateral stratigraphy of Siberia are listed in Fig. 5 and figured in radiation of microphytoplankton assemblages and Plates I and II. Consequently, boundaries of distin- diversity dynamics of some taxonomic and morpholog- guished dinocysts zones are in most cases the important ical groups depending on evolution of environments in stratigraphic markers of a great correlation potential. the Siberian paleobasin were detected (Lebedeva and Pestchevitskaya, 1997; Pestchevitskaya, 2002, 2003). INVESTIGATION HISTORY OF LOWER The succession of the BerriasianÐBarremian dinocyst CRETACEOUS DINOCYSTS IN SIBERIA zones has been considered earlier (Pestchevitskaya, 2005a, 2006). Description of these zones is presented Systematic investigations of Lower Cretaceous below for the first time. microphytofossils from Siberia commenced in the ter- minal 1980s. Il’ina (1988) was first to study microphy- toplankton from the JurassicÐCretaceous boundary DINOCYST ZONES OF THE LOWER deposits in the Nordvik Peninsula, and Fedorova et al. CRETACEOUS IN NORTH SIBERIA (1993) examined the Berriasian dinocysts of the Boyarka River section. Dinocyst assemblages from PareodinioideaeÐBatioladinium varigranosumÐ particular ammonite zones have been described how- Cassiculasphaeridia reticulata Zone (dinocyst ever without distinguishing independent stratigraphic assemblage 1 (DZ1) (Figs. 2, 5) subdivisions substantiated by dinocysts. Timoshina Characteristic taxa. Dinocysts of simple morphology et al. (1999) described for the first time the freshwater (Batiacasphaera norvikii Burger, Escharisphaeridia microphytoplankton from the Hauterivian, Barremian psilata Kumar, Sentusidinium spp.), typical of the beds and Aptian deposits of the Khatanga depression, while occur in association with Sirmiodinium grossii Alberti, Lebedeva and Nikitenko (1998, 1999) established Jansonia spp., Microdinium opacum Brideaux, Sirmio- almost continuous succession of dinocysts zones in the diniopsis orbis Drugg, Tubotuberella apatela (Cookson Yatriya River section (Subpolar Urals) beginning from et Eisenack) Ioannides, T. rhombiformis Vozzhenni- the upper Volgian up to the lower Hauterivian inclusive. kova, Chlamydophorella nyei Cookson et Eisenack, In the last works, the distinguished biostratigraphic Ambonosphaera spp., Occisucysta wierzbowskii units have been correlated with the Boreal dinocyst Poulsen, and Wrevittia helicoidea (Eisenack et Cook- zonations of Europe and Canada, and basic trends of son) Helenes et Lucas-Clark. Abundance of the first microphytoplankton distribution depending on sedi- three taxa can be significant. An important feature is mentary facies have been elucidated. A few works are persistent diversity of the subfamily Pareodinioideae dedicated to the same approach used for stratigraphic (Paragonyaulacysta ?borealis (Brideaux et Fisher) subdivision of the Lower Cretaceous deposits recov- Stover et Evitt, Pareodinia ceratophora Deflandre, ered by drilling in unexposed areas of West Siberia P. minuta Wiggins, P. arctica Wiggins, Pluriarvalium (Mchedlishvili, 1971; Multidisciplinary Study…, 1978; osmingtonense Sarjeant, Evansia evittii (Pocock) Jan- Lebedeva and Pestchevitskaya, 1998; Kirichkova et al., sonius and others). Genera Dingodinium, Fromea, Wal- 1999; Basel et al., 2002). lodinium, Cribroperidinium, Tubotuberella, and Apteo- Limited data on dinocysts from the study region dinium are diverse as well. Stratigraphically important have been obtained by N. Aarhus (see in Shul’gina species are Cyclonephelium cuculliforme (Davies) et al., 1994) who studied these fossils in the JurassicÐ Aarhus, Stanfordella exanguia (Duxbury) Helenes et Cretaceous boundary beds and the lower Berriasian of Lucas-Clark, Cassiculasphaeridia reticulata Davey, the Nordvik Peninsula. The upper Berriasian has not Achomosphaera neptunii (Eisenack) Davey et Will- been investigated, whereas the Valanginian and Hau- iams, Dingodinium ?spinosum (Duxbury) Davey, Bati- terivian intervals have been sampled here at random. oladinium varigranosum (Duxbury) Davey, Athigmato- My own data characterize palynology of these intervals cysta aff. glabra Duxbury, and Spiniferites ramosus more exactly (Pestchevitskaya, 2002; Nikitenko et al., (Ehrenberg) Monteil. Also characteristic of the zone is 2004). In addition, successions of microphytoplankton occurrence of Horologinella anabarensis Pestche- assemblages have been established in the Lower Creta- vitskaya, Dingodinium minutum Dodekova, D. tubero- ceous sections of the Anabar Bay eastern coast sum (Gitmez) Fisher et Riley, D. subtile Pestche- (Pestchevitskaya, 1999, 2000), Ust-Yenisei region vitskaya, Cassiculasphaeridia magna Davey, Apteod- (Nikitenko et al., 2004; Pestchevitskaya, 2005b), PurÐ inium granulatum Eisenack, A. grande Cookson et Taz interfluve (Lebedeva and Pestchevitskaya, 1998; Hughes, A. maculatum Eisenack et Cookson, Circulod-

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007

580 PESTCHEVITSKAYA

Anabar Bay eastern Borehole Borehole coast, exp. 1A Gorshkovskaya 1017 Romanovskaya 140 Biostr. unit Formation Depth, m Thickness, m Lithology Formation Depth, m Thickness, m Lithology Nordvik Peninsula, Biostr. unit Boreal zonal standard (Zakharov et al., 1997) Dinocyst zone

13.0 exp. 35, 36 6.2 2343-2330 20–21 Zone DZ8 Zone DZ3 ? 19 2.5 upper 18 2.5 Zone 13.0 2628–2615 17 1.5 Formation Depth, m Thickness, m Lithology DZ8 Biostr. unit Zone 15 3.5 Zone DZ7 DZ5 ? lower Substage Zone DZ4 10-14

14.0 16 17 2642–2628

? 9 RMN1 ramulicosta beani Tigyansk Higher, 14.0 15 3.9 Zone DZ6 ?

correlation 2656–2642 Zone 14 2.5 with the bojarkensis DZ7 5-8 Boreal Borehole Severo- standard 13 9.4 4.6 6.3 15.0 7.9 2.4 Vologochanskaya 18 is not performed because of Zone 12.0 1 3.0 DZ6 2750–2738 fauna absence ?

in section 6.2 Zone 42-43 of Borehole Akh Cherkashino 12 DZ5 ? 41 3.0

Gorshkovskaya 13.0

1017 2763–2750 40 5.5

lower upper ? 39 4.0 DZ4

Homolsomites ramulicosta beani 11 38 4.5 10.8 11.4 bojarkensis Nordvik Peninsula, 37 4.0 Paksinsk

DZ5 exp. 33

Zone 36 3.8 10 8.6 35 2.0 Dichotomites bidihotomus 9.3 Zone DZ3

32-34 9 5.1

lower ? Formation Depth, m Thickness, m Lithology Biostr. unit 31 6.0 8 7.7 64 2.1

Polypty- Paksinsk 4.1 chites 61–63 30 11.0

beani Zone DZ2 7 8.9 3.2 59–60 29 3.0 Siberites Zone DZ VLG3 DZ4 Sibirites Zone

4.8 28 2.8 55–58

ramulicosta ramuli- ? quadrifidus astieriptychus quadrifidus astieriptychus 6 7.8 costa 27 4.2

5.6 26 2.5 Euryptychites 52–54 astieriptychus 25 5.0 5 4.5 DZ3 Zone

4.6 4 2.9 49–51

lower 4.9

Euryptychites 23-24 3 3.4 22 3.0 quadrifidus 4.4

Zone 45–48 2 1.8 DZ2 Paksinsk 21 3.0 44 Neotollia 2.0

5.5 Zone DZ2 tolli klimovskiensis 1 10

klimovskiensis 4.3 18-20 klimovskiensis Zone DZ2 Zone DZ3 43a–b Zone 42 klimovskiensis 3.1 Zone DZ1

Tollia tolli DZ RMN1 7.5

Bojarkia 39,40,41a,b 1 4 7 10 13 meseznikowi 38 4.5 Berriasian Valanginian Hauterivian Barremian Stage

lower 2 5 8 11 14 37 meseznikowi 3.3 Zone DZ1 Zone DZ2 Zone DZ VLG3

Surites Zone DZ1 analogus 3 6 9 12 5.2 31–36 analog

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007

DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 581 inium spp., Cleistosphaeridium spp., Cribroperidinium lia klimovskiensis ammonite zones), which is recogniz- tensiftense Below, Tanyosphaeridium magneticum able in subpolar regions of Canada and Siberia (Bride- Davies, and Leberidocysta spinose Pestchevitskaya. aux and Fisher, 1976; Pocock, 1980; Davies, 1983; Lower boundary is defined in the Nordvik Penin- Il’ina, 1988; Riding et al., 1999; Lebedeva and sula only (Nikitenko et al. 2004) at the first occurrence Nikitenko, 1998, 1999; Nikitenko et al., 2004). Oldest level of Batioladinium varigranosum, Cassiculas- specimens of Achomosphaera neptunii have been phaeridia reticulata, and Tanyosphaeridium magneti- found at the Berriasian Stage base in Boreal regions of cum. Canada (Williams et al., 1974; Jenkins et al. 1974; Bujak and Williams, 1978) and not far away from Mos- Remarks. Basic taxa of the assemblage, representa- cow (Iosifova, 1996). In many sections of Greenland tives of the subfamily Pareodinioideae inclusive, are and western Europe, this species has been found in the widespread not only in the Berriasian of North Eurasia, upper Berriasian and Valanginian (Duxbury, 1977; but in the Upper Jurassic as well (Brideaux and Fisher, Davey, 1979; Piasecki, 1979; Fisher and Riley, 1980; 1976; Fisher and Riley, 1980; Rawson and Riley, 1982; Duxbury et al., 1999). In the studied sections, persistent Davey, 1982; Davies, 1983; Van Helden, 1986; Lebe- occurrence of Dingodinium subtile has been observed deva and Nikitenko, 1998; Riding et al., 1999). On the only in the upper Berriasian, whereas its specimens are other hand, the assemblage includes stratigraphically extremely rare at higher levels. important species, first occurrence of which is recorded in the Berriasian of Canada and northern Europe. First In the PurÐTaz interfluve (Borehole Romanovskaya occurrence of Batioladinium varigranosum in mid- 140), where the zone DZ1 have not been detected, I dis- Berriasian strata is known in northwestern Europe tinguished zone DZ RMN1 of the wider upper Berria- (Davey, 1982) and Newfoundland (Van Helden, 1986). sianÐlower Valanginian stratigraphic range. Oldest Cassiculasphaeridia reticulata forms are found Type section: the Nordvik Peninsula; Exposure 33, at the base of the Bojarkia payeri Zone in the Subpolar beds 31Ð59 of argillite-like silty splintery clays bluish Urals (Lebedeva and Nikitenko, 1998). In northern to dark gray, with subordinate interlayers of brownish Europe, species Tanyosphaeridium magneticum has gray flaggy clay of lesser thickness and with thin lentic- been observed until present only in the Valanginian, ular intercalations and concretions of limestone (Basov Hauterivian and Barremian dinocyst assemblages et al., 1970; Zakharov et al., 1983). (Davies, 1983; N¿hr-Hansen, 1993; Prössl, 1990). An important component of the assemblage is D. ?spino- Distribution: Khatanga depression (middle part of sum, the characteristic Berriasian taxon regarded by the Paksa Formation); Ust-Yenisei region (uppermost some researchers as zonal index species (Fisher and Nizhnyaya Kheta and basal Sukhaya Dudinka forma- Riley, 1980; Rawson and Riley, 1982). Species Tubotu- tions). berella rhombiformis, Paragonyaulacysta ?borealis Stratigraphic position: Upper BerriasianÐbasal and Cyclonephelium cuculliforme are reported only Valanginian interval corresponding to extent of the from the Subpolar Urals (Lebedeva and Nikitenko, Surites analogus and basal Neotollia klimovskiensis 1998), Khatanga depression (Il’ina 1988; Shulgina et ammonite zones; established based on direct correla- al., 1994; Riding et al., 1999) and Arctic Canada tion with zones of the Boreal standard in section of the (Brideaux and Fisher, 1976; Davies, 1983) and can be Nordvik Peninsula (Basov et al., 1970; Zakharov et al., considered as characteristic taxa of subpolar regions in 1983). Siberia and Canada. In the studied sections, the persis- tent occurrence of Tubotuberella rhombiformis is lim- ited by the top of zone DZ1. The first occurrence level Paragonyaulacysta sp.ÐBatiacasphaera sp. Zone of Cyclonephelium cuculliforme is an important strati- with DZ RMN1 (Fig. 2) graphic indication, as in Arctic Canada this taxon is one of index species of the respective Berriasian zone Characteristic taxa. Dinocysts are of extremely (Davies, 1983). Paragonyaulacysta ?borealis wide- low taxonomic diversity, represented by Paragonyaul- spread in the Upper Jurassic and Berriasian deposits is acysta sp., Batiacasphaera sp., and by poorly preserved accepted to be the index species of the Paragonyaula- proximate and chorate forms. cysta ?borealisÐDingodinium ?spinosum dinocyst zone Lower boundary is tentatively defined at the sec- (within the extent of Craspedites okensisÐbasal Neotol- tion base.

Fig. 2. Correlation chart of the studied sections based on the established dinocyst zones in the north of Western and central Siberia. The lit-par-lit division of sections is done using the following works: Nordvik Peninsula—Basov et al., 1970; Zakharov et al., 1983; Bogomolov, 1989; Anabar Bay eastern coast—Bogomolov et al., 1983; Bogomolov, 1989; Borehole Severo-Vologochanskaya 18— Nikitenko et al., 2004; Borehole Romanovskaya 140—Zakharov et al., 1999; Borehole Gorshkovskaya 1017—unpublished data of V.A. Kazanenkov and O.O. Savchenkova. Lithology: (1) sands, sandstones; (2) sandy aleurolites; (3) sandy aleurites; (4) aleurites; (5) silty clays; (6) clayey aleurolites; (7) argillites; (8) clays; (9) pebbles; (10) calcareous interlayers and concretions; (11) ammo- nites; (12) bivalves; (13) fucoids; (14) sampling levels for palynological analysis.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 582 PESTCHEVITSKAYA

Found macrofauna, Abridged lithologic characterization foraminiferal assemblages Interval, m Stage, substage Formation Thickness, m Lithology Dinocyst zone

Interlayering dark gray aleurites and gray sandy aleurites; bioturbation marks; layer of dark gray siderite 12.5 Cribrostomoides concretions at the base infracretaceous,

854.8–842.3 ë. sinuosus Aleurites, gray, vaguely laminated, sometimes sandy with clay ooids (in lower part) and rare interlayers of dark 12.0 gray clayey aleurites; bioturbation marks

Fine interlayering of light gray sandy aleurites, aleurites and dark gray clayey aleurites; occasional interlayers of dark gray vaguely-laminated clay and light gray, sometimes greenish sand; 18.1 bioturbation marks ?

Interlayering of gray sandy aleurites, dark gray clays and greenish sands; bioturbation marks; 12.1 a bed of gray sideritic aleurite at the base

Aleurites, greenish gray, often sandy, with laminae of gray sandy aleurite and dark gray silty clay; 13.2 bioturbation marks; bed of gray sideritic sandstone at the base

Aleurites, gray to greenish gray, sandy, with horizontal, cross and lenticular lamination; interlayers of gray to light gray and greenish sands in the upper part; bioturbation marks; bed of gray sideritic aleurolite 20.3 at the base 930.5–910.2 910.2–897.0 897.0–884.9 884.9–866.8 866.8–854.8 Sukhaya Dudinka

Interlayering of dark gray silty horizontally-laminated 9.0 Valanginella clays and greenish gray sandy aleurites; bioturbation marks

939.5 – 930.5 tatarica Lower Valanginian Upper Valanginian-lower Hauterivian Interlayering light gray sands and gray sandy aleurites of the lower half grade upward into dark gray to greenish sandy aleurites with laminae of dark gray clayey aleurite; bioturbation marks; dark gray bed of sideritic sandstone at the base 22.0

Aleurites, gray to dark gray, sandy, with horizontal or lenticular lamination, locally with lenticles and laminae of light gray sand; bioturbation marks 20.4 Neotollia klimovskiensis 981.9–961.5 961.5–939.5

Nizh- Zone DZ1Aleurites, dark gray, with lenticular bedding, Zone DZ2 enclosing interlayers Zone DZ VLG3 yaya 6.7 Gaudryina gerkei, Tro- of gray sandy aleurite and rare pebbles 988.6– 981.9 Berri- asian Kheta chammina rosaceaforrnis

Fig. 3. The Lower Cretaceous section recovered by Borehole Severo-Vologochanskaya 18 (additional data from Nikitenko et al., 2004; symbols as in Fig. 2).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 583

Abridged Found macrofauna, lithologic foraminiferal assemblages characterization Dinocyst zone Interval, m Thickness, m Lithology Sandstone, fine-grained, 4.0 clayey-silty,

2751– 2747 bioturbated;

Aleurites, light gray, 7.0 2753.5 clayey, sandy Astarte veneriformis Zakh., in upper part Discina sp. indet.

Clayey aleurite with sandy laminae 7.0 Zone DZ3 2765–2758 2758–2751 Interlayering 3.0 2765.5 of silty sandstones Striatomodiolus sibiricus (Bod.) 2768– 2765 and argillites Neotollia klimovskiensis (Krymh.), Euryptychites quadrifidus (Kemp.)

assemblage of foraminifers Aleurolites, highly Lower Valanginian6.0 Stage, substage 2772Astarte veneriformis Zakh. clayey, splintery

SortymPinna sp. indet. Formation

10.0 Sandstone, Evolutinella grandis fine-grained, massive

2784–2774 2774–2768 ?

Argillite, gray, 4.5 foliated 3016 3020.5–

3023 Argillite, black, Buchia sp. indet. Berriasian– 6.5 foliated lower Valanginian Zone DZ RMN1 3027–3020.5

Fig. 4. The Lower Cretaceous section recovered by Romanovskaya 140 (additional data from Zakharov et al., 1999; symbols as in Fig. 2).

Remarks. Because of a very low diversity of Escharisphaeridia spp.ÐOligosphaeridium spp.Ð dinocysts, it is impossible to define precisely strati- Circulodinium spp. Zone (DZ2, Figs. 2, 5) graphic position of the zone. Occurrence of Paragon- yaulacysta sp. facilitates determination of their upper Characteristic taxa. Diversity of dinocysts is com- paratively low. Main components of the assemblage are boundary only. As is established, representatives of this forms of simple morphology (Escharisphaeridia spp., genus do not occur above the Neotollia klimovskiensis Batiacasphaera spp., Sentusidinium spp.) and poorly Zone in sections of the Nordvik Peninsula and the Ana- preserved proximate dinocysts. Persistently occurring bar Bay eastern coast. The upper boundary is tenta- species are Dingodinium spp., D. minutum, Oli- tively defined in the upper Berriasian. gosphaeridium spp., Cleistosphaeridium spp., some- Type section: Borehole Romanovskaya 140, depth times Chlamydophorella spp., Cassiculasphaeridia interval 3027Ð3020.5 m; sediments are represented by reticulata and Jansonia spp. Species Sirmiodinium grossii, Circulodinium Tubotuberella apatela, Tri- black foliated argillites 6.5 m thick. spp., chodinium spp., Horologinella anabarensis, Cribrope- Distribution: PurÐTaz interfluve (lower part of the ridinium exilicristatum (Davey) Stover et Evitt, C. aff. Sortym Formation). sarjeantii (Vozzhennikova) Helenes, some other Cribro- peridinium forms, Apteodinium maculatum, A. granula- Stratigraphic position: upper BerriasianÐbasal tum, A. ?vescum Matsuoka, and A. cf. grande occur fre- Valanginian. quently. An important feature is the declined diversity

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 584 PESTCHEVITSKAYA

Northern regions Basic palynological Stratigraphically important dinocyst species of Eurasia and America, criteria of from North Siberia and other where the same boundary Characteristic species boundaries „northern regions of Eurasia and America criteria are established Dinocyst Lower boundaries of beds zone

Nelchinopsis kostromiensis Northwestern Europe DZ8

Aprobolocysta eilema Northwestern Europe Latest finds lowerDZ8 upper Substage Batioladinium ?exiguum, Wallodinium krutzschii Cassiculasphaeridia magna

First occurrence of Vesperopsis fragilis South England Muderongia staurota, M. crucis, M. tetracan- Apteodinium spongiosum tha, M australis, Batioladinium jaegeri, B. Last occurrence of DZ7 Tenua americana Northern Germany longicornutum, B. ?exiguum, Gardodinium First occurrence of Aprobolocysta trabeculosum, Cribroperidinium confossum, Northwestern Europe DZ7 eilema ë. ?edwardsii, ë. ?muderongense, Cassicu- lasphaeridia reticulata, Dingodinium cervi- DZ6 culum, Circulodinium distinction, Pseudoce- DZ6 First occurrence of Aptea anaphrissa Barents Sea shelf, Subpolar Urals ratium pelliferum, Hystrichodinium voigtii, H. pulchrum, Oligosphaeridium complex, staffiiensis DZ5 ? First occurrence of Hystrichodinium Nelchinopsis kostromiensis DZ5 solare Subpolar Urals Muderongia simplex, Cassiculasphaeridia

reticulata, Wrevittia helicoidea, Nelchi- Circulodinium compta First abundance peak of ? Only in the north nopsis kostromiensis, Stanfordella ?creta- Dingodinium cerviculum upper DZ4 of Central Siberia cea, Batioladinium varigranosum, Din-

Aldorfia sibirica Ambonospliaera godinium cerviculum, Circulodinium dis- tinctum Chlamydophorella nyei, Wallodi- DZ4 Dingodinium cerviculum Arctic Canada, Siberia nium luna, Apteodinium granulatum, Tri- Oligosphaeridium Everywhere in the north of chodinium ciliatum, Apteodinium spon- Endoscrinium pharo DZ3 DZ3 , , rrence of complex Eurasia and America giosum Oligosphaeridium diluculum First occu- Dingodinium tuberosum O. ?asterigium, Heslertonia heslertonensis Ambonosphera delicata lower DZ2 DZ2 Last occurrence of Paragonyaula- Arctic Canada, Greenland, Tubotuberella rhombiformis cysta ?borealis Norway, Siberia Cassiculasphaeridia magna,Wallodinium DZ1 Last occurrence of Digodinium Northwestern Europe krutzchii, Dingodinium ?albertii, D. minu- borealis ?spinosum tum, D. tuberosum, Pareodinia cerato- ? phora, Fromea amphora, Tubotuberella apatela, Sirmiodinium grossii, Sirmiodi-

First occurrence of Batioladinium Canada, northwestern Dingodinium minutum varigranosum Europe niopsis orbis

middleDZ1 lower upper

First occurrence of Cassiculaspha- Ocissucysta wierzbowskii

Berriasian Valanginianeridia reticulata Hauterivian BarremianSubpolar Stage Urals Paragonyaulacysta lower upper

Fig. 5. Palynological substantiation of dinocyst zones, their stratigraphic position and generalized stratigraphic extents of strati- graphically important dinocysts (stratigraphic analysis and palynological comparison of Siberian, European and Canadian biostrati- graphic units are performed using original and published data from works cited in the text and Table 4). of Pareodinioideae represented by Pluriarvalium spp., and Pareodinia minuta become extinct somewhat P. osmingtonense, Pareodinia spp., P. arctica, and lower. P. ceratophora, which occur irregularly. New forms occurring are Nelchinopsis kostromiensis (Vozzhennik- Remarks. The last occurrence of Paragonyaula- ova) Wiggins, Sentusidinium granulatum (Courtinat) cysta ?borealis in the Valanginian basal interval is established in Arctic Canada, Greenland, Norway and Stover et Williams, Circulodinium brevispinosum Siberia, i.e., in the circum-Arctic regions, and the (Pocock) Jansonius, Aprobolocysta sp., and Trichodin- respective level is therefore a reliable stratigraphic ium ciliatum (Gocht) Eisenack et Klement. marker (Aarhus et al., 1986; Aarhus et al., 1990; Shul- Lower boundary defined in sections of the Nord- gina et al., 1994; Lebedeva and Nikitenko, 1998; vik Peninsula and Borehole Severo-Vologochanskaya Nikitenko et al., 2004). The last occurrence level of 18 marks the last occurrence of Pagaronyaulacysta D. ?spinosum, which is practically coincides with the spp. and P. ?borealis, the diversity decrease of Pareod- Berriasian top in northern regions of western Europe inioideae, and persistent presence of Oligosphaeridium (Duxbury 1977; Davey, 1979; Fisher and Riley, 1980; A Stratigraphic…, 1992; Duxbury et al., 1999), is the spp. In the Nordvik Peninsula, Tubotuberella spp. and other important marker. Dingodinium subtile occur at random above this level and T. rhombiformis disappears from the assemblage. It is likely that the beds are thicker in Exposure 35 Species Wallodinium krutzschii and Wrevittia heli- (Nordvik Peninsula) and span lower part of the Euryp- coidea do not occur above this level in Borehole tychites quadrifidus Zone (Fig. 2), but having no sam- Severo-Vologochanskaya 18; Dingodinium ?spinosum ples from this part of the section for palynological anal-

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 585

Stratigraphically important dinocyst species from North Siberia and other northern regions of Eurasia and America Odontochitina operculata Cyclonephelium intonsum Vesperopsis fragilig Aprobolocysta eilema Aprobolocysta neista Aptea anaphrissa (Arctic regions) (Arctic (Arctic regions) (Arctic Hystrichodinium solare Gardodiniuni ordinale Dapsilidinium multispinosum Muderongia asymmetrica Muderongia staurota Cyclonephelium brevispinatum Kiokansium polypes ?muderongense

Cauca parva “tomaszovensis” Muderongia tetracantha Batioladinium longicornutum Discorsia nanna Downiesphaeridium aciculare Aprobolocysta galeata Muderongia cruris Muderongia australis Cribroperidinium orthoceras Dingodinium cerviculum Oligosphaeridium complex Gardodinium trabeculosum (Boreal regions) (Boreal ?exiguum

Muderongia Oligosphaeridium albertense Cribroperidinium ?muderongense Cribroperidinium (Boreal regions) (Boreal Cassiculasphaeridia reticulata Nelchinopsis kostromiensis Batioladinium varigranosum Batioladinium Tanyosphaerdium magneticum Batioladinium jaegeri ?spinosum

Cyclonephelium cuculliforme Dingodinium subtilis Athigmatocysta glabra Gardodinium trabeculosum Dingodinium Heslertonia heslertonensis Endoscrinium campanula Circulodinium distinctum Apteodinium maculatum Dingodinium cerviculum Achomosphera neptunii Spiniferites ramosus Muderongia brevispinosa

Fig. 5. (Contd.) ysis I failed to define precisely the upper boundary Oligosphaeridium complexÐDingodinium cerviculum position here. Zone (DZ3, Figs. 2,5) Type section: the Nordvik Peninsula; Exposure 33, beds 60Ð64 of dark gray, argillite-like, silty splintery Characteristic taxa. The grown diversity of clays and clayey aleurites with interlayers of limestone dinocysts, persistently occurring among which are Cas- concretions; thickness 7.7 m; Exposure 35, beds 18Ð22 siculasphaeridia magna, Sirmiodinium grossii, of dark gray silty clay with lens-like limestone concre- Chlamydophorella nyei, Oligosphaeridium ?asteri- tions; thickness 12.5 m (Basov et al., 1970; Zakharov gium (Gocht) Davey et Williams, Fromea amphora, et al., 1983; Bogomolov, 1989). F. fragilis, Pareodinia ceratophora, Wallodinium luna, Dingodinium minutum, Muderongia simplex Alberti Distribution: Khatanga depression (middle part of emend. Riding et al., and representatives of genera Din- the Paksa Formation); Ust-Yenisei region (lower part of godinium, Oligosphaeridium, Cleistosphaeridium, the Sukhaya Dudinka Formation without very basal Escharisphaeridia, Sentusidinium, and Circulodinium. interval). A high diversity of the genus Oligosphaeridium is espe- Stratigraphic position: the basal Valanginian, cially remarkable. In West Siberia, diversification of the ammonite zones Neotollia klimovskiensis without its genus Muderongia is established. Of prime importance lowermost part and Euryptychites quadrifidus in its is appearance of new species Dingodinium cerviculum lower part; established based on direct correlation with Cookson et Eisenack emend. Khowaja-Ateequzzman the Boreal standard zones in sections of the Nordvik et al., Muderongia cruces Neale et Sarjeant, M. austra- Peninsula (Basov et al., 1970; Zakharov et al., 1983; lis Helby, Gardodinium trabeculosum (Gocht) Alberti, Bogomolov, 1989) and of the Anabar Bay eastern coast Oligosphaeridium complex (White) Davey et Williams, (Zakharov et al., 1983; Bogomolov, 1989). O. albertense (White) Davey et Williams, O. diluculum

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Plate I

3 1 2 4 5

6 7 8 9

11 10 12 13 14

18 15 16 17 19

22

21 24 23

20 25 26 27 28 29

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Davey, Circulodinium distinctum (Deflandre et Cook- Siberia in northern Europe and Canada. In western son) Jansonius, Aprobolocysta galeata Backhouse, Europe, the first occurrence of Dingodinium cervicu- Canningiopsis colliveri (Cookson et Eisenack) Back- lum is established at the level of the upper Volgian Sub- house, Cribroperidinium ?muderongense (Cookson et stage (Davey, 1979), whereas in northern regions of Eisenack) Davey, C. orthoceras (Eisenack) Davey, Canada and Siberia this species occurs beginning from Wrevittia cassidata (Eisenack et Cookson) Helenes et the basal Valanginian (McIntyre and Brideaux, 1980; Lucas-Clark, and Trichodinium speetonense Davey. Davies, 1983; Lebedeva and Nikitenko, 1998). In Lower boundary is defined at the first occurrence northern sections of Eurasia and America, the first level of Oligosphaeridium complex and Dingodinium occurrence level of Oligosphaeridium complex is prac- cerviculum in section of the Anabar Bay eastern coast tically isochronous, corresponding approximately to only. the base of the Buchia keyserlingi Zone, thus being a Remarks. Taxa always present in the assemblage good stratigraphic marker (Duxbury, 1977, 2001; are also widespread in underlying deposits, the Upper Bujak and Williams, 1978; Piasecki, 1979; Davey, Jurassic strata inclusive (see description and remarks to 1979; McIntyre and Brideaux, 1980; Davies, 1983; DA1 and DA2). However, newly appeared taxa of DA3 Aarhus et al., 1986; A Stratigraphic…, 1992). First are stratigraphically important being known from the occurrences of Muderongia crucis and Cribroperidin- Lower Cretaceous dinocyst assemblage far beyond ium ?muderongense are established in the lower Val-

Plate I. Dinocysts of the Lower Cretaceous from northern areas of Siberia. Collection no. 842, is stored at the Central Siberian Geo- logical Museum, Trofimuk Institute of Petroleum geology and Geophysics, Siberian Division, Russian Academy of Sciences, Novosibirsk. (1) Barbatacysta brevispinosa (Courtinat) Courtinat. Nordvik Peninsula, Exposure 33, Bed 31, Sample 31.1, Specimen no. 107.1/11, Paksa Formation, Berriasian, Surites analogus Zone, × 420; (2) Apteodinium granulatum Eisenack. Nordvik Penin- sula, Exposure 33, Bed 31, Sample 31.1, Specimen no. 107.2/36, Paksa Formation, Berriasian, Surites analogus Zone, × 450; (3) Pluriarvalium osmingtonense Sarjeant. Nordvik Peninsula, Exposure 33, Bed 32, Sample 32.1, Specimen no. 110.1/30, Paksa For- mation, Berriasian, Surites analogus Zone, ×450; (4) Aldorfia sibirica Pestchevitskaya. eastern coast of the Anabar Bay, Exposure 1A, Bed 20, Sample 31, Specimen no. 31.1/13, Paksa Formation, lower Valanginian, Siberites ramulicosta Zone, beani Subzone, ×450; (5) Batioladinium jaegeri (Alberti) Brideaux. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.5/6, Cherkashino Formation, upper Hauterivian, ×420; (6) Athigmatocysta aff. glabra Duxbury. West Sibe- ria, Borehole Severo-Vologochanskaya 18, depth 988.6 m, Sample 47, Specimen no. 1763.1/20, Nizhnyaya Kheta Formation, Ber- riasian, ×470; (7) Cribroperidinium tensiftense Below. West Siberia, Borehole Severo-Vologochanskaya 18, depth 950.2 m, Sample 80, Specimen no. 1733.1/8, Sukhaya Dudinka Formation, lower Valanginian, ×400; (8) Apteodinium grande Cookson et Hughes. Nordvik Peninsula, Exposure 33, Bed 31, Sample 31.1, Specimen no. 107.2/28, Paksa Formation, Berriasian, Surites analogus Zone, ×350; (9) Endoscrinium vellum Pestchevitskaya. Nordvik Peninsula, Exposure 33, Bed 51, Sample 51.1, Specimen no. 135.1/10.a, Paksa Formation, Valanginian, Neotollia klimovskiensis Zone, ×500; (10) Muderongia brevispinosa Iosifova. Nor- dvik Peninsula, Exposure 36, Bed 11, Sample 11.2, Specimen no. 1090.3/8, Paksa Formation, Hauterivian, Homolsomites bojarken- sis Zone, ×250; (11) Aprobolocysta neista Duxbury. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.2/45, Cherkashino Formation, upper Hauterivian, × 320; (12) Muderongia endovata Riding et al. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.1/16, Cherkashino Formation, upper Hau- terivian, ×270; (13) Endoscrinium sp. Nordvik Peninsula, Exposure 35, Bed 35, Sample 35.1, Specimen no. 1075.1/5, Paksa For- mation, lower Valanginian, Euryptychites astieriptychus Zone, ×480; (14) Muderongia australis Helby. eastern coast of the Anabar Bay, Exposure 1A, Bed 20, Sample 30, Specimen no. 30.1/9, Paksa Formation, lower Valanginian, Siberites ramulicosta Zone, Beani Subzone, ×480; (15) Batiacasphaera sp. Nordvik Peninsula, Exposure 33, Bed 32, Sample 32.1, Specimen no. 110.1/19, Paksa Formation, Berriasian, Surites analogus Zone, ×400; (16) Taleisphaera sp. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.5/20, Cherkashino Formation, upper Hauterivian, ×490; (17) Evansia evittii (Pocock) Jansonius. Nordvik Peninsula, Exposure 33, Bed 32, Sample 32.1, preparation 110.1, Specimen 20, Paksa Formation, Ber- riasian, Surites analogus Zone, ×300; (18) Dingodinium minutum (Gitmez) Fisher et Riley. Nordvik Peninsula, Exposure 33, Bed 37, Sample 37.1, Specimen no. 115.1/8, Paksa Formation, Berriasian, Bojarkia meseznikovi Zone, ×400; (19) Apteodinium ?vescum Matsuoka. Nordvik Peninsula, Exposure 33, Bed 46, Sample 46.1, Specimen no. 128.1/11, Paksa Formation, Berriasian, Tollia tolli Zone, ×300; (20) Tubotuberella rhombiformis Vozzhennikova. Nordvik Peninsula, Exposure 33, Bed 41, Sample 41.1, Specimen no. 123.1/2, Paksa Formation, Berriasian, Tollia tolli Zone, ×420; (21) Pareodinia minuta Wiggins. West Siberia, Borehole Severo- Vologochanskaya 18, depth 984.3 m, Sample 50, Specimen no. 1760.1/9, Nizhnyaya Kheta Formation, Berriasian, ×450; (22) Chlamydophorella nyei Cookson et Eisenack. eastern coast of the Anabar Bay, Exposure 1A, Bed 12, Sample 18, Specimen no. 18.4/8, Paksa Formation, lower Valanginian, Euryptychites astieriptychus Zone, ×320; (23) Horologinella anabarensis Pestchevitskaya. eastern coast of the Anabar Bay, Exposure 1A, Bed 12, Sample 18, Specimen no. 18.1/26, Paksa Formation, lower Valanginian, Euryptychites astieriptychus Zone of ammonites, ×550; (24) Gardodinium ordinale Davey. West Siberia, Borehole Gorshkovskaya 1017, interval 2615Ð2628 m, Sample 58, Specimen no. 1423.1/15, Cherkashino Formation, upper Hauterivian, ×360; (25) Dingodinium subtile Pestchevitskaya. Nordvik Peninsula, Exposure 33, Bed 42, Sample 42.1, Specimen no. 124.1/10, Paksa Formation, Berriasian, Tollia tolli Zone, ×350; (26) Cleistosphaeridium sp. Nordvik Peninsula, Exposure 33, Bed 37, Sample 37.1, Specimen no. 115.1/11, Paksa Formation, Berriasian, Bojarkia meseznikovi Zone, ×400; (27) Spiniferites ramosus (Ehren- berg) Monteil. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.4/15, Cherkash- ino Formation, upper Hauterivian, ×290; (28) Paragonyaulacysta ?borealis (Brideaux et Fisher) Stover et Evitt. Nordvik Peninsula, Exposure 33, Bed 31, Sample 31.1, Specimen no. 107.1/26, Paksa Formation, Berriasian, Surites analogus Zone, ×470; (29) Oli- gosphaeridium complex (White) Davey et Williams. eastern coast of the Anabar Bay, Exposure 1A, Bed 21, Sample 34, Specimen no. 34.1/7, Paksa Formation, lower Valanginian, Siberites ramulicosta Zone, Beani Subzone, ×390.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 588 PESTCHEVITSKAYA

Plate II

1 2 4 3 5

8

6 7

9 10

12 17 14

11

13 16 18 15

19 20

21 22 23

24 25

26 27 28 29 30

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 589 anginian of northern Europe, Arctic Canada and Subpo- tunity to analyze samples from lower part of the Euryp- lar Urals (Davey, 1979; Davies, 1983; Aarhus et al., tychites quadrifidus Zone I was unable to define with 1986; Lebedeva and Nikitenko 1998). Species Mud- precision the position of lower boundary here (Fig. 2). erongia australis, Aprobolocysta galeata and Cannin- This subdivision is undetectable in the Ust-Yenisei giopsis colliveri constantly occur in the Hauterivian region, and there is established zone DZ VLG3 span- (Iosifova, 1996; Prössl, 1990; Nøhr-Hansen, 1993; ning upper part of the lower Valanginian, upper Valang- Aarhus et al., 1986, 1990). Consequently, dinocysts inian, and presumably basal Hauterivian. inherited from the Jurassic communities and taxa char- acteristic of the Lower Cretaceous are already of equal Type section: eastern coast of the Anabar bay, significance in the assemblage that is its important fea- Exposure 1A, beds 6Ð15: beds 6Ð13 are composed of ture. dark gray silty clay with calcareous concretions; beds 14, 15 of gray clayey to sandy-clayey aleurites with cal- Zones DZ3 are probably of a greater thickness in careous concretions; total thickness 76.1 m (Bogo- section of the Nordvik Peninsula, but having no oppor- molov et al., 1983; Bogomolov, 1989).

Plate II. Dinocysts of the Lower Cretaceous from northern areas of Siberia. Collection no. 842, is stored at the Central Siberian Geological Museum, Trofimuk Institute of Petroleum geology and Geophysics, Siberian Division, Russian Academy of Sciences, Novosibirsk. (1) Aptea anaphrissa (Sarjeant) Sarjeant et Stover. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 35, Specimen no. 1400.1/1, Cherkashino Formation, lower Hauterivian, ×300; (2) Achomosphaera neptuni (Eisenack) Davey et Will- iams. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 36, Specimen no. 1401.1/2, Cherkashino For- mation, lower Hauterivian, ×420; (3) Occisucysta wierzbowskii Poulsen. West Siberia, Borehole Severo-Vologochanskaya 18, depth 984,3 m, Sample 50, Specimen no. 1760.1/12, Nizhnyaya Kheta Formation, Berriasian, ×370; (4) Cribroperidinium aff. janinae Gyrka. Nordvik Peninsula, Exposure 35, Bed 34, Sample 34.4, Specimen no. 1074.2/26, Paksa Formation, lower Valanginian, Euryptychites astieriptychus Zone, ×440; (5) Batioladinium longicornutum (Alberti) Brideaux. West Siberia, Borehole Gorshk- ovskaya 1017, interval 2628Ð2642 m, Sample 30, Specimen no. 1395.1/11, Cherkashino Formation, lower Hauterivian, ×320; (6) Hystrichodinium solare Pestchevitskaya. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Spec- imen no. 1403.1/40, Cherkashino Formation, upper Hauterivian, ×300; (7) Hystrichodinium voigtii (Alberti) Davey. West Siberia, Borehole Gorshkovskaya 1017, interval 2615Ð2628 m, Sample 58, Specimen no. 1423.2/5, Cherkashino Formation, upper Hau- terivian, ×360; (8) Leberidocysta spinosa Pestchevitskaya. Nordvik Peninsula, Exposure 35, Bed 39, Sample 39.3, Specimen no. 1081.2/3, Paksa Formation, lower Valanginian, Siberites Zone, ×380; (9) Mendicodinium sp. West Siberia, Borehole Gorshkovskaya 1017, interval 2615Ð2628 m, Sample 59, Specimen no. 1424.1/2, Cherkashino Formation, upper Hauterivian, ×340; (10) Cymosos- phaeridium “?phoenix” (Duxbury) Fauconnier. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 36, Specimen no. 1401.1/4, Cherkashino Formation, lower Hauterivian, ×570; (11) Muderongia mcwhaei Cookson et Eisenack. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 34, Specimen no. 1399.1/7, Cherkashino Formation, lower Hauterivian, ×420; (12) Pseudoceratium pelliferum Gocht. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.6/1, Cherkashino Formation, upper Hauterivian, ×300; (13) Nelchinopsis kostromiensis (Vozzhen- nikova) Wiggins. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.5/3, Cherkashino Formation, upper Hauterivian, ×440; (14) Aprobolocysta cornuta Pestchevitskaya. West Siberia, Borehole Gorshk- ovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.6/15, Cherkashino Formation, upper Hauterivian, ×360; (15) Aprobolocysta galeata Backhouse. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 40, Specimen no. 1405.1/9, Cherkashino Formation, upper Hauterivian, ×330; (16) Oligosphaeridium aff. totum Brideaux: West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 33, Specimen no. 1398.1/6, Cherkashino Formation, lower Hauterivian, ×450; (17) Aprobolocysta eilema Duxbury. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.1/14, Cherkashino Formation, upper Hauterivian, ×360; (18) Tanyosphaeridium isocalamum (Deflandre et Cookson) Davey et Williams. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.2/12, Cherkashino Formation, lower Hauterivian, ×430; (19) Cassiculasphaeridia reticulata Davey. West Siberia, Borehole Severo-Vologochanskaya 18, depth 950,2 m, Sample 80, Specimen no. 1733.1/8, Sukhaya Dudinka Formation, lower Valanginian, ×490; (20) Batioladinium reticulatum Stover et Helby: West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.4/4, Cherkashino Formation, upper Hauterivian, ×390; (21) Cyclonephelium brevispinatum (Millioud) Below. West Sibe- ria, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 37, Specimen no. 1402.1/18, Cherkashino Formation, upper Hauterivian, ×330; (22) Florentinia sp. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 38, Specimen no. 1403.3/16, Cherkashino Formation, upper Hauterivian, ×260; (23) Vesperopsis mayi Bint. West Siberia, Borehole Gorshk- ovskaya 1017, interval 2615Ð2628 m, Sample 58, Specimen no. 1423.2/6, Cherkashino Formation, upper Hauterivian, ×400; (24) Pseudoceratium aff. expolitum Brideaux. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 37, preparation 1402.1, Specimen 12, Cherkashino Formation, upper Hauterivian, ×450; (25) Spiniferites aff. hyperacanthus (Deflandre et Cookson) Cookson et Eisenack. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 32, Specimen no. 1397.1/2, Cherkashino Formation, lower Hauterivian, ×300; (26) Dingodinium cerviculum Cookson et Eisenack emend. KhowajaÐ Ateequzzman et al. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 40, Specimen no. 1405.2/1, Cherkashino Formation, upper Hauterivian, ×350; (27) Batioladinium varigranosum (Duxbury) Davey. Nordvik Peninsula, Expo- sure 35, Bed 35, Sample 35.1, Specimen no. 1075.2/26, Paksa Formation, lower Valanginian, Euryptychites astieriptychus Zone, ×300; (28) Chytroeisphaeridia sp. Nordvik Peninsula, Exposure 35, Bed 35, Sample 35.1, Specimen no. 1075.1/2, Paksa Formation, lower Valanginian, Euryptychites astieriptychus Zone, ×450; (29) Muderongia cruces Neale et Sarjeant. West Siberia, Borehole Gorshkovskaya 1017, interval 2615Ð2628 m, Sample 41, Specimen no. 1406.2/5, Cherkashino Formation, upper Hauterivian, ×300; (30) Muderongia tetracantha (Gocht) Alberti. West Siberia, Borehole Gorshkovskaya 1017, interval 2628Ð2642 m, Sample 32, Specimen no. 1397.1/8, Cherkashino Formation, lower Hauterivian, ×410.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 590 PESTCHEVITSKAYA

Distribution: Khatanga depression (middle part of tant species Nelchinopsis kostromiensis, Cassiculas- the Paksa Formation); PurÐTaz interfluve (middle part phaeridia reticulata, Oligosphaeridium complex, Din- of the Sortym Formation. godinium cerviculum, Sepispinula ?“huguoniotii” Stratigraphic position: lower Valanginian; ammo- (Cookson et Eisenack) Islam, Aldorfia sibirica nite zones Euryptychites quadrifidus (lower part), Pestchevitskaya, Aprobolocysta galeata, Gardodinium Euryptychites astieriptychus, and lower part of Siber- sp., and Trichodinium speetonense. Persistent presence ites ramulicosta Subzone; established based on direct of Sirmiodinium grossii, Pareodinia spp., Circulodin- correlation with the Boreal standard zones in sections ium spp., Cleistosphaeridium spp., and Oligosphaerid- of the Nordvik Peninsula (Basov et al., 1970; Zakharov ium spp. is characteristic. et al., 1983; Bogomolov, 1989) and the Anabar Bay Lower boundary defined in sections of the Nordvik eastern coast (Zakharov et al., 1983; Bogomolov, Peninsula and Anabar Bay eastern coast is not very dis- 1989). tinct, marked by the grown abundance of Dingodinium cerviculum although not persistently. Aldorfia sibirica appears at this level in the Anabar section, Aprobolo- Sentusidinium spp.ÐApteodinium spp. Zone cysta galeata in the Nordvik peninsula. (DZ VLG3, Fig. 2) Remarks. In West Siberia (Borehole Roma- Characteristic taxa. Most frequently occurring in novskaya 140), Aprobolocysta galeata appears lower, the assemblage are Sentusidinium spp., in upper part of the Euryptychites quadrifidus Zone Escharisphaeridia spp., Apteodinium spp., and Cassic- probably because of southerly position of the section. ulasphaeridia reticulata. The other characteristic forms In the Moscow syneclise and northwestern Europe, this are Sentusidinium granulatum, Dingodinium spp., taxon regularly occurring in the Hauterivian is Chlamydophorella sp., Sirmiodinium grossii, Fromea unknown from underlying deposits (Iosifova, 1996; fragilis, Lithodinia sp., Nelchinopsis kostromiensis, Prössl, 1990). A considerable abundance rate of D. cer- Microdinium ornatum Cookson et Eisenack, Jansonia viculum is characteristic of the upper Valanginian in the spp., Tubotuberella rhombiformis, Circulodinium Subpolar Urals (Lebedeva and Nikitenko, 1998). It is compta (Davey) Helby, and Oligosphaeridium ?asteri- remarkable that the assemblage consists predominantly gium. The subfamily Pareodinioideae is not diverse, of the Cretaceous taxa. represented only by species of the genus Pareodinia. Upper boundary is not established, being tentatively Lower boundary is defined at the level of a consid- defined at the section top. erable diversity decline (Borehole Severo-Vologochan- Type section: eastern coast of the Anabar Bay, skaya 18). Disappearing above this level are genera Exposure 1A, beds 16Ð21; beds 16Ð18 are composed of Cribroperidinium, Wallodinium, and species Occi- gray clayey to sandy-clayey aleurites with calcareous sucysta wiersbovskii, Tubotuberella apatela, Sirmiod- concretions, Bed 19 corresponds to gray clayey sand- iniopsis orbis, Pluriarvalium osmingtonense and some stone with calcareous concretions, Bed 20 to sandy others. aleurite with lenticular sand interlayers, Bed 21 to gray Remarks. Dinocysts of the assemblage represent cross-bedded sandstone; total thickness 29.7 m (Bogo- mostly taxa of wide stratigraphic ranges, and the zone molov et al., 1983; Bogomolov, 1989). is dated with reference to results of micropaleontologi- Distribution: Khatanga depression (upper part of cal analysis (Nikitenko et al., 2004). Nevertheless, data the Paksa Formation). on dinocysts reliably determine position of the lower boundary (Pestchevitskaya, 2005b), whereas the upper Stratigraphic position: lower Valanginian, Siber- one is tentatively defined at the section top. ites ramulicosta Zone (upper part of the ramulicosta Subzone and lower part of the beani Subzone); estab- Type section: Borehole Severo-Vologochanskaya lished based on direct correlation with the Boreal stan- 18, depth interval 909.6Ð842.3 m of recovered gray dard zones in sections of the Nordvik Peninsula (Basov sandy to clayey aleurites with interlayers of clay, sider- et al., 1970; Zakharov et al., 1983; Bogomolov, 1989) itic sandstone and aleurolite; thickness 67.3 m. and the Anabar Bay eastern coast (Zakharov et al., Distribution: Ust-Yenisei region (upper part of the 1983; Bogomolov, 1989). Sukhaya Dudinka Formation). Stratigraphic position: upper part of the lower Val- anginian, upper Valanginian, and probably basal Hau- Hystrichodinium solareÐMuderongia spp. Zone terivian. (DZ5, Figs. 2, 5) Characteristic taxa. Persistent components of the assemblage are Dingodinium spp., Oligosphaeridium Aldorfia sibirica–Aprobolocysta galeata Zone spp., Muderongia spp., Sentusidinium spp., (DZ4, Figs. 2, 5) Escharisphaeridia spp., Batioladinium spp., Cribrope- Characteristic taxa. Dominant taxa are Dingodin- ridinium spp., Cleistosphaeridium spp., Jansonia spp., ium spp. (up to 5%) and D. cerviculum (up to 5.5%) and abundance of the first three species may be signifi- occurring in association with stratigraphically impor- cant. The other characteristic forms are Muderongia

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 591 staurota Sarjeanti, M. tetracantha (Gocht) Alberti, istic is presence of Nelchinopsis kostromiensis, Hystri- M. simplex, M. pariata Duxbury, M. australis (up to chodinium solare, H. voigtii (Alberti) Davey, H. pul- 9%), M. “tomaszowensis” Alberti emend. Riding et al., chrum Deflandre, Oligosphaeridium ?asterigium, M. brevispinosa Iosifova, Nelchinopsis kostromiensis, O. cf. intermedium Corradini, Spiniferites ramosus, Batioladinium varigranosum, Oligosphaeridium com- Achomosphaera neptunii, Aprobolocysta spp., Gardod- plex, Aprobolocysta sp., Tenua ?americana (Pothe de inium trabeculosum, and Tenua ?americana. First Baldis et Ramos) Prössl, Gardodinium trabeculosum, occurrences of Pseudoceratium sp., Aptea anaphrissa and Cassiculasphaeridia reticulata. Stratigraphically (Sarjeant) Sarjeant et Stover, Batioladinium longicor- important features are the diversity of the genus Mud- nutum, and Oligosphaeridium aff. totum Brideaux are erongia and first occurrence of Hystrichodinium solare stratigraphically important. Pestchevitskaya. Lower boundary is conventionally defined in bore- Lower boundary is defined tentatively at the first hole section Gorshkovskaya 1017 at the beginning of occurrence level of Hystrichodinium solare and the interval 2656Ð2642 m (above the missing core interval, increased diversity and abundance of the genus Mud- Fig. 2). The characteristic dinocyst assemblage gets erongia (there is a hiatus in exposures of the Nordvik suddenly the greater diversity at this level, and Oli- Peninsula and the borehole section Gorshkovskaya gosphaeridium aff. totum, Aptea anaphrissa, Batiola- 1017 has not been sampled with gaps). dinium longicornutum, and single Pseudoceratium sp. Remarks. The diversity of the genus Muderongia appear here. and occurrence of Hystrichodinium solare are charac- Remarks. In northern areas of western Europe, the teristic of the lower Hauterivian dinocyst assemblages oldest occurrence level of Aptea anaphrissa is estab- from the Subpolar Urals (Lebedeva and Nikitenko, lished in upper part of the lower Hauterivian (Aarhus 1998). In Australia (Helby et al., 1987) and northern et al., 1990). Morphologically similar dinocysts present Europe (Aarhus et al., 1990; N¿hr-Hansen, 1993), per- as well in the lower Hauterivian assemblages of sistent occurrence of Muderongia australis and its microphytoplankton in the Subpolar Urals (Lebedeva abundance in particular have been observed beginning and Nikitenko, 1998). The diversity of the genus from the Hauterivian. Pseudoceratium are characteristic of the upper Hau- The upper boundary of beds with DZ5 is defined terivian and Barremian of Canada (Bujak and Williams, conventionally at the section top in the Nordvik Penin- 1978) and several northern regions of Europe (Prössl, sula: in borehole Gorshkovskaya 1017 there is a sam- 1990; N¿hr-Hansen, 1993; Iosifova, 1996; Smelror pling gap (Fig. 2). et al., 1998). Data on their occurrence in Lower Creta- Type section: Nordvik Peninsula, Exposure 36, Bed ceous of Siberia have not been published, but according 11 of gray silty sandstones 4 m thick (Zakharov et al., to oral communication of A.F. Fradkina, dinocysts of 1983). this genus are found in Hauterivian deposits of central West Siberia. Distribution: Khatanga depression (lower part of the Tigyan Formation) and around latitudinal segment Type section: Borehole Gorshkovskaya 1017, inter- of the Ob River (upper part of the Akh Formation). val 2656Ð2630.55 m of argillaceous deposits; thickness 25.45 m. Stratigraphic position: lower Hauterivian, middle part of the Homolsomites bojarkensis Zone; established Distribution: region of the Ob River latitudinal seg- based on direct correlation with the Boreal standard ment (lower part of the lower Cherkashino Subforma- zones in section of the Nordvik Peninsula (Zakharov tion). et al., 1983). Stratigraphic position: upper part of the lower Hauterivian. Aptea anaphrissaÐOligosphaeridium aff. totumÐBatioladinium longicornutum Zone Aprobolocysta eilemaÐA. neistaÐOdontochitina spp. (DZ6, Figs. 2, 5) Zone (DZ7, Figs. 2, 5) Characteristic taxa: Dinocyst diversity increases. Characteristic taxa: Dinocyst diversity is increased In addition to taxa of wide stratigraphic ranges further. Dominant species are Escharisphaeridia spp. (Escharisphaeridia spp., Leberidocysta spp., Cassicu- and Muderongia spp. Common species are Sentusidin- lasphaeridia magna, Chlamydophorella spp., Jansonia ium spp., Fromea spp., Mendicodinium spp., Leberi- spp., Oligosphaeridium spp., Circulodinium spp., Cleis- docysta spp., Dingodinium spp., D. cerviculum, Cassic- tosphaeridium spp.), the assemblage constantly includes ulasphaeridia magna, Jansonia spp., Apteodinium Cassiculasphaeridia reticulata, Oligosphaeridium com- spp., Aptea anaphrissa, and Circulodinium spp. Fre- plex, Batioladinium varigranosum, and B. longicornu- quently occurring forms are Cassiculasphaeridia retic- tum (Alberti) Brideaux. Diversity of the genus Mud- ulata, Pareodinia spp., Odontochitina spp., O. opercu- erongia spp. increases (M. tetracantha, M. australis, lata (O. Wetzel) Deflandre et Cookson, and Hystri- M. endovata Riding et al., M. simplex, M. mcwhaei chodinium spp. (H. voigtii, H. pulchrum). Very Cookson et Eisenack, M. staurota). The very character- characteristic is diversity of genera Aprobolocysta,

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 592 PESTCHEVITSKAYA

Pseudoceratium, Muderongia, and Batioladinium rep- (Harding, 1986). Species Pseudoceratium expolitum, resented by the following taxa: Aprobolocysta galeata, Gonyaulacysta ?kleithria, Cyclonephelium intonsum, A. neista Duxbury, A. eilema Duxbury, A. cornuta Gardodinium ordinale, and Vesperopsis mayi, which Pestchevitskaya, Pseudoceratium cf. pelliferum Gocht, are present in zone DZ7, are widespread and persis- P. expolitum Brideaux, Muderongia tetracantha, tently occurring in the Barremian, being abundant M. simplex, M. staurota, M. extensiva Duxbury, sometimes (N¿hr-Hansen, 1993; Iosifova 1996; Smel- M. mcwhaei (up to 2%), M. “tomaszovensis,” M. cru- ror et al., 1998). cis (up to 2%), M. australis, M. asymmetrica Aarhus, Upper boundary has not been observed. It was Batioladinium ?exiguum (Alberti) Brideaux, B. vari- impossible to study compositional changes of dinocysts granosum, B. jaegeri (Alberti) Brideaux, B. longicor- from transition between DZ7 and overlying subdivision nutum (Alberti) Brideaux, and B. reticulatum Stover et because of sampling gap (Fig. 2). Helby. Important species are Wrevittia helicoidea, Nelchinopsis kostromiensis, Oligosphaeridium com- Type section: Borehole Gorshkovskaya 1017, inter- plex, Vesperopsis mayi Bint, V. fragilis (Harding) Har- val 2630.55Ð2615 m of argillites; thickness 15.55 m. ding, Gardodinium trabeculosum, G. ordinale Davey, Distribution: region of the Ob River latitudinal seg- Gonyaulacysta ?kleithria Duxbury, Cyclonephelium ment (lower Cherkashino Subformation, upper part). intonsum Duxbury, and Cymososphaeridium ?phoenix (Duxbury) Fauconni. Stratigraphic position: lower part of the upper Hauterivian. Lower boundary. Taxonomic composition of dinocysts changes to a considerable extent at this boundary that marks the diversity increase in genera Canningia spp.ÐNelchinopsis kostromiensis Zone Aprobolocysta, Muderongia, and Batioladinium. The (DZ8, Figs. 2,5) boundary is marked by first occurrences of Odonto- chitina Dux, O. operculata, Aprobolocysta neista, A. Characteristic taxa. Diversity of dinocysts is eilema, A. cornuta, Pseudoceratium expolitum, Gon- sharply decreased. Dominant taxa are Escharisphaeridia yaulacysta ?kleithria, and Cyclonephelium intonsum; spp. and Mendicodinium spp. Common taxa are Leberi- species Vesperopsis spp., V. mayi, and V. fragilis appear docysta spp. and Canningia spp. Single specimens of somewhat higher. Dingodinium spp., D. cerviculum, Wallodinium sp., W. krutzschii, Endoscrinium sp., and Mendicodinium spp. become commonly occurring, Ovoidinium sp., Batioladinium spp., B. ?exiguum, whereas Hystrichodinium solare, Tenua americana, Aprobolocysta spp., A. galeata, A. eilema, A. cornuta, Oligosphaeridium aff. totum, O. ?asterigium, Chlamy- Apteodinium spp., Nelchinopsis kostromiensis, Cyclo- dophorella spp. Disappear from the assemblage. Spe- nephelium intonsum, and Sentusidinium spp. are identi- cies of the genus Oligosphaeridium are of a lesser fied as well. diversity and do not occur regularly in the assemblage. Lower boundary has not been observed because of Remarks. Single specimens of Odontochitina oper- incomplete core recovery and is defined tentatively culata have been found in the upper Valanginian of based on occurrence of the characteristic dinocyst Arctic Canada (Davies, 1983). This species occurs assemblage that is of sharply declined diversity. All the more frequently in the upper Hauterivian of northwest- species of genera Muderongia, Hystrichodinium, Oli- ern Europe and Australia (Helby et al., 1987; Aarhus et gosphaeridium, Vesperopsis, Cassiculasphaeridia, al., 1990; Prössl, 1990). Diversity and persistent occur- Odontochitina, Pseudoceratium, and Gardodinium dis- rence of the genus Odontochitina is established in the appear from the assemblage along with Aptea Barremian deposits of Canada and northern Europe, anaphrissa, Cyclonephelium intonsum, Wrevittia heli- where its species are sometimes fairly abundant (Bujak coidea, and other forms. and Williams 1978; Davey, 1979; Duxbury, 1980, 2001; Remarks. Decreasing abundance and diversity of Aarhus et al., 1986; N¿hr-Hansen, 1993; Iosifova, microphytoplankton could be to a consequence of gen- 1996; N¿hr-Hansen, McIntyre, 1998; Smelror et al., eral regression in the West Siberian paleobasin (Pale- 1998). Constant presence and diversity of Pseudocera- olandscapes…, 1968; Gol’bert, 1987). tium forms is typical of the upper Hauterivian and Bar- remian dinocyst assembalges (Bujak and Williams, Dinocysts are represented mostly by taxa of wide 1978; Prössl, 1990; Nøhr-Hansen, 1993; Iosifova, stratigraphic ranges. The highest occurrence of 1996; Smelror et al., 1998). In northwestern Europe, Aprobolocysta eilema and Nelchinopsis kostromiensis first occurrence of Aprobolocysta neista is detected in is known in northwestern Europe up to the basal Barre- middle part of the lower Hauterivian (Davey, 2001), mian only, being unknown from higher strata whereas A. eilema appears at the base of the upper Hau- (A Stratigraphic…, 1992; N¿hr-Hansen, 1993; Smelror terivian (A Stratigraphic…, 1992; Duxbury, 1977, et al., 1998; Aarhus et al., 1990). Upper boundary has 2001). In northern areas of Germany, disappearance not been observed. level of Tenua ?americana corresponds to the boundary Type section: Borehole Gorshkovskaya 1017, inter- between substages (Prössl, 1990). Oldest specimens of val 2343Ð2330 m of argillites with insignificant inter- Vesperopsis fragilis have been found at the same level layers of silty argillites; thickness 13 m.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 593

Distribution: region of the Ob River latitudinal seg- assemblages from nearby (Subpolar Urals, Moscow ment (upper Cherkashino Subformation, lower part). basin) and remote regions (western Europe, Canada, Stratigraphic position: lower part of the lower Greenland) contain many species in common, except Barremian. for sections of the Barents Sea shelf, where Berriasian and Valanginian assemblages contain each only one taxon occurring in the studied Siberian sections (Table 2). COMPARATIVE ANALYSIS OF LOWER Similarity between North Siberian and Canadian CRETACEOUS DINOCYST ASSEMBLAGES dinocyst assemblages decreases in Hauterivian depos- FROM SIBERIA, CANADA AND NORTHERN its. The most different are the assemblages from Arctic AREAS OF EUROPE Canada. The lower Cretaceous dinocyst zonations are elabo- The Barremian assemblages of dinocysts from rated for the Subpolar Urals, Greenland, and northern northern regions of Siberia are of a low taxonomic regions of Europe and Canada. Successions of dinocyst diversity. In the Barremian Age, area of the West Sibe- zones are established for separate regions and general- rian paleobasin became considerably reduced (Pale- ized scale is suggested for Canada and northwestern olandscapes…, 1968; Gol’bert, 1987), and the assem- Europe (Table 1). In respective works, principal atten- blages likely consisted of taxa, which were able to sur- tion is paid to boundaries of biostratigraphic units and vive unstable environments in the habitat basin, where to consideration of criteria, which define with confi- depths and salinity often changed. In Europe, the Bar- dence stratigraphic positions and ranges of dinocyst remian dinocyst assemblages are known from sections zones. In majority of works, these zones are distin- of normal marine facies, and accordingly their guished based on changes in taxonomic composition of dinocysts are extraordinary abundant and diverse (Aar- dinocyst assemblages, i.e., on first or last occurrences hus et al., 1990; Prössl, 1990; Smelror et al., 1998; of certain taxa and on their acme in particular sections, Duxbury et al., 1999; Duxbury, 2001). which are commonly of local significance. Strati- It is remarkable that concurrent dinocyst assem- graphic ranges of the same taxa in other regions are blages from northern regions of Eurasia and America sometimes omitted from considerations, and conse- contain species in common, which are informative in quently their stratigraphic significance is improperly terms of stratigraphy, because their first occurrence is evaluated. Accordingly, only some of them can be confined to particular level in different regions. The regarded as appropriate for determination of bound- oldest specimens of a certain species are usually known aries between dinocyst zones: the appearance level of from one region, whereas in the other sections this such species in the section corresponds to their oldest taxon can be found in higher horizons (Table 3). On the occurrence or their inceptions can be recognized at the other hand, there is a series of species whose first or last same level in different regions (Table 1). As a result, occurrence is recorded practically at the same level in boundaries of concurrent biostratigraphic units are several northern regions of Eurasia and America defined sometimes based on different criteria. In such a (Table 3). These species exactly are regarded in this case, correlation is possible by means of comparative work as palynological criteria determining boundaries analysis of general taxonomic composition of micro- of biostratigraphic units in Siberian succession of phytoplankton assemblages. This laborious approach is dinocyst assemblages (Table 4). It is remarkable there- certainly inappropriate for correlation of palynostrati- with that the dinocyst zones distinguished in the upper graphic units of a narrow extent, but for a wider strati- Berriasian, Valanginian and lower Hauterivian of North graphic interval it is possible to define a group of char- Siberia are directly correlated with the Boreal standard acteristic species occurring in most regions of North zonations (Zakharov et al., 1997), being studied in stra- Eurasia and America. The Lower Cretaceous dinocyst totype sections of the Khatanga depression. Conse- assemblages from northern regions of Siberia contain quently, boundaries of the North Siberian dinocyst quite a number of respective species (Table 2). In gen- zones are important stratigraphic markers in most cases eral, they appear in lower stratigraphic intervals and, owing to this correlation. being widespread Lower Cretaceous, define the “face” of corresponding assemblage. As dinocyst zones are defined based on inceptions The general tendency by transition from the Berria- and extinctions of species at certain stratigraphic levels sian to Hauterivian consists in growing significance of not only in Siberia, but also in the other northern chorate dinocysts, species of the family Ceratiaceae, regions of Eurasia, their boundaries are recognizable and in compositional changes of the family Pareodini- over vast territories (Fig. 5, Table 4). In some cases, it aceae (Table 2). The Berriasian dinocyst assemblages is possible therefore to correlate directly the dinocyst most similar to assemblages of North Siberia are biostratigraphic subdivisions of North Siberia with described from the Boyarka River sections (the units of dinocyst zonations in Western Europe and Can- YeniseiÐKhatanga depression; Fedorova et al., 1993), ada. Subpolar Urals (Fedorova et al., 1993; Lebedeva and The Berriasian and two lower Valanginian levels are Nikitenko, 1998), and Moscow basin (Iosifova, 1996). recognizable in northern regions of Canada, Europe The situation changes in the Valanginian: dinocyst and Siberia (Fig. 5, Table 4). The first occurrence of

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 594 PESTCHEVITSKAYA subzone ? Subzone reticulata cretacea Subzone Subzone Subzone Subzone Subzone Canningia cf. Batioladinium Nexosispinium longicornutum simplicispinum magna Aptea anaphrissa Palaeoperidinium

vetusculum Cassiculasphaeridia Kleithriasphaeridium

operculata terrula Zone Zone

Dinocyst zones Zone

(Harding, 1986) South England Odontochitina Subtilisphaera nanna Discorsia zo- nes chei bilis ctum noid natus tatum tatum gotts- kmani varia- nensis biden- regale margi- ambly- speeto- gonium elegans rudenc- fissicos- rarocin- inversus noricum Ammo------, - Wre Wre , subsp. Aprobo ; Circulodini Tehamadini Endoscrini appears , , , Discorsia ; last occurrence Nematosphaerop ; Zone E Zone C Zone B Zone D Papuadinium Zone (?) appears at the appear in the , Hystrichodinium and diutina (Duxbury, 1977) East England LB ? Papuadinium apiculatum

um campanula um distinctum apiculatum locysta eilema in the upper Hauterivian Oligosphaeridium complex Spriniferies ramosus primaevus nanna middle furcatum Hauterivian boundary Canningiopsis “tabulata” LB: first occurrence of LB: first occurrence of LB: first occurrence of sis scala LB: first occurrence of Zone A: first occurrence of um evitii vittia appears in upper part Subtilisphaera terrula vittia perforobtusa K. einoides of Occisucysta tentorium

Zone -

heir first or last occurrence is recorded at the given level

Phoberocysta neocomica Phoberocysta nuciforme Zone

? Apteodinium Zone dinium Arthur Ctenido panneum et al., 1982

, -

Zone ,

,

-

elegantum elegantum

, Subzone

Ctenidodinium Ctenidodinium Zone johnewingi Biorbifora Aptea Aptea acme of Jenkins peak Zone et al., 1974 anaphrissa anaphrissa neocomica presence of P. neocomica Pseudocerati um nudum Spriniferites dentatus A. neptunii Systemato phora orbifera Phoberocysta - - -

A. , Nel , , ; last , Batio , Newfoundland ? Amphorula me C. arthuriae A. delicata , Sentusidinium rioultii , Assemblage Zone Assemblage Zone Assemblage Zone Van Helden, 1986 Amphorula metaelliptica Phoberocysta neocomica Endoscrinium campanula LB: first occurrence of Cantulodinium arthuriae chinopsis kostromiensis occurrence of taelliptica ladinium varigranosum Sentusidinium rioultii LB (the Portlandian base), Amphorula metaelliptica delicata presence of Oppel Zone Oppel Zone Cyclonephelium ; last occurrence of ; Oppel Zone. LB: first ? ? T. magneticum, Apteod- Oppel Zone cuculiforme Arctic Canada (Davies, 1983) V. atlanticum Trichodinium erinaceoides – Cyclonephelium cuculliforme – Tetrachacysta spinosigiberrosa Muderongia simplex LB: first occurrence of soidictyum cinctum, Escharisphaeridia rudis, Paragonyaulacysta borealis Tanyosphaeridium magneticum Oppel Zone LB: first occurrence of glutinata, L. episomum, M. tomaszowensis, O. inium apiatum, Cribroperidinium muderongense, Kallosphaeridium ?circulare, Batiacasphaera ag- albertense, O. complex, totum, operculata Valvaeodinium atlanticum Ellip occurrence of Apteodinium apiatum, Batiacasphaera agglutinata, S. crystallinum, Prolixosphaeridium spissum, Lep- todinium episomum, C. cuculliforme, T. rhombiformis ,

- – , Zone Zone Aptea Phobero Eastern Canada pelliferum Peak Zone neocomica (Williams elegantum anaphrissa et al., 1974) Phoberocysta Ctenidodinium Pseudoceratium LB: acme – Ap- tea anaphirissa, Subtilisphaera perlucida LB: first occurren- ce of cysta neocomica Achomosphaera neptunii Systematophora complicata - - , - , - - ; ------, Cyc- Li Circu Phobe , , Biorbi- Rhyn , B. joh- Coroni , (acme), Circulo Achomo , , , Surculosp Ctenidodi , , longifurcatum ? Canada ; Peak Zone neocomica Southeastern Phoberocysta Correlation of Lower Cretaceous dinocyst zonations established in northern regions Eurasia and America Calaiosphaeridium Aptea anaphrissa Assemblage Zone Aptea polymorpha LB: first occurrence of A. anaphrissa Pseudoceratium re- gium last occurrence of Rhynchodiniopsis serrata ,

onephelium vannophorum

Ctenidodinium elegantum Assemblage Zone (Bujak et Williams, 1978) asymmetricum LB: first occurrence of lodinium attadalicum l Cribroperidinium orthoce ras haeridium Subtilisphaera perlucida newingi, I. kondratjevi last occurrence of

nium elegantum LB: first occurrence of rocysta neocomica fera johnewingi sphaera neptunii dinium distinctum chodiniopsis serrata thosphaeridium siphoni fera oceanica phorum upper upper lower upper lower upper middle lower Substage lower

Stage Barremian Hauterivian Valanginian Berriasian Table 1. Notes: (LB) lower boundary; (UB) upper stratigraphically important taxa listed in the table are printed bold, if t in different regions, and regular type, if the designated section only.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 595 -

, ; Pse - , N. kostro- Din- Subzone. reticulata A. anaphrissa sp. A ? cf. spinosum toveae ? Pseudoceratium Subzone Subzone Greenland Nelchinopsis kostromiensis ; acme of Northeastern Zone. acme of (Nohr-Hansen, 1993) Pseudoceratium toveae

Subzone. LB: first occurrence of Subtilisphaera terrula Ophiobolus Canningia

Aptea anaphrissa Pseudoceratium pellife LB: first occurrence of rum udoceratium pelliferum last occurrence of godinium E. pharo LB: last occurrence of miensis Batioladinium longicornutum Batioladinium Zone - Sub- sp. A Zone ” sp. A eticulata sp. A Subzone. cf. r Subzone Gardodinium Subzone Subzone Aptea anaphris Subzone culum Zone Subzone Europe simplicispinum Nexosispinium vetus- “ Cannosphaeropsis

Northwestern Canningia

(Davey, 1979)

Kleithriasphaeridum

LB: last occurrence of Egmontodinium Cannosphaeropsis

terrula zone. LB: last occurrence

Endoscrinium pharo of

opressus )

Spiniferites ramosus ( Carpodinium granulatum

Gardodinium trabeculosum Subzone. LB: acme of trabeculosum

; last occurrence of sphaera

Zone Cassiculasphaeridia magna level mid-Portlandian the at LB

Palaeoperidinium cretaceum Subzone. LB: first occurrence of

Aptea anaphrissa LB: acme of sa Nexosispinium vetusculum Subtili-

Discorsia nanna nanna Discorsia Odontochitina operculata Odontochitina Zone Gochteodinia villosa Gochteodinia LB: first occurrence of Zone Oligosphaeridium complex Pseudoceratium pelliferum - - , - - - - - , Endo , Phobe Dingodi Diacanth Subzone , Pseudoce pinosum , Heslertonia s Papuadinium , , ?

;occurrence last Ctenidodinium Papuadinium , ? Paragonyaulacy , Biorbifera johne , , Subzone Subzone Canada, Egmontodinium toryna ?spinosum

, Muderongia extensiva Pareodinia antennata Dingodinium Northwestern Europe

(Fisher et Riley, 1980) LB: first occurrence of Muderongia extensiva

Endoscrinium pharo sta capillosa ?schizoblatum apiculatum LB: last occurrence of LB: last occurrence of nium ratium pelliferum scrinium campanula rocysta neocomica Achomosphaera neptunii wingi of apiculatum um hollisteri heslertonensis Occisucysta tentorium LB: last occurrence of LB: last occurrence of

Phoberocysta neocomica Phoberocysta Zone - - LB: last ;occur- last Dingodini Rotosphaerop Daveya boresphaera ? B. radiculatum, O. diluculum Dichadogonyaulax culmula , Batioladinium “pomum” UB: last occurrence of Circulodinium compta Duxbury et al., 1999 C. gigas, Leptodinium arquatum ;of acme Rotosphaeropsis thule (LKP2) Zone Circulodinium compta (LKP1) Zone ?spinosum

LB: first occurrence of rence of LKP5 Zone. um Muderongia simplex (LKP4) Zone. occurrence of LB: acme of sis thule LKP3 Zone. LB: last occurrence of

- - -

- - - - - cf. Subzone

spp.

trabeculosum

sp. A Subzone Gardodinium Aptea apatela Subzone Subzone Subzone Subzone Subzone Subzone Subzone Subzone extensiva reticulata um toryna licispinum anaphrissa Dichadogo Muderongia Plaeoperidi nyaulax ropsis ridium corru ridium simp Cannosphae Egmontodini Canningia N. vetusculum Tubotuberella nium cretacea gatum Kleithriasphae Kleithriasphae 1982

-

grossii Zone

Discorsia nanna Discorsia neocomica Phoberocysta ?spinosum Dingodinium Zone Zone Zone Rawson, Riley, Sirmiodinium

Zone

Subtili terrula

sphaera

Zone oeLKP17 Zone LKP16 ,

, ; ; LKP7 - - spinosum spon ? LKP11 Zone England, North Sea ? Desmocysta Oligosphaeri Nelchinopsis Spiniferites Spiniferites Aprobolocysta neista Systematophora Dingodinium Aprobolocysta LKP20 Zone, LKP21 Zone Achomosphaera ramulifera Aprobolocysta extrema Hystrichodinium ramoides ? appears inside zone Cribroperidinium cornutum Oligosphaeridium junctum Cymososphaeridium validum H. arborispinum UB: Scriniodinium barremianum LKP25 Zone; LB: last occurrence of Aptea anaphrissa LB: last occurrence of LB: last occurrence of LB: last occurrence of Ascodinum fissilum Dinocyst zones Duxbury, 2001 LB: acme of LB: acme of LB: acme of LB: last occurrence of first occurrence of acme of last occurrence of LB: last occurrence of ; first occurrence of LB: last occurrence of LB: last occurrence of Zone; LB: last occurrence of Canningia duxbury Systematophora scoriacea a , , LKP6 Zone; 7.1 Subzone; 7.2 Subzone; palmul giosus Oligosphaeridium complex LKP8 Zone; kostromiensis simplex LKP16.2 Subzone dium junctum eilema LKP12 Zone LKP10 Zone primaevus LKP17.1 Subzone; LKP15 Zone; LKP14 Zone; LKP13 Zone; LKP9 Zone; LKP17.2 Subzone; LKP16.1 Subzone; LKP19 Zone; LKP25 Zone LKP24 Zone LKP23 Zone LKP22 Zone; last occurrence of LKP18 Zone; (Contd.) noid zones

Ammo-

tum rudenck- mani elegans fissicosta- tum rarocinc- tum variabilis margina- tus gottschei speeto- nensis inversus regale noricum amblygo- nium unnamed pitrei dichoto- mites polypty- chites paratollia albidum stenom- phalus icenii kochi runctoni bidenta-

middle lower upper middle upper lower upper lower upper Substage lower

Stage Barremian Hauterivian Valanginian Berriasian Table 1.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 596 PESTCHEVITSKAYA - - - , , - zones , , zones Batio- , spp., spp., – Aptea Oligo- Oligospha Aprobolo

– ?borealis

spp. zones spp. zones Dingodinium totum , spp. zones ?spinosum

Odontochitina oper aff. , Vesperopsis fragi Aprobolocyta eilema Aprobolocysta neista Oligosphaeridium Escharisphaeridia and Circulodinium Odontochitina Oligosphaeridium complex Aptea anaphrissa Muderongia Dingodinium cerviculum Hystrichodinium solare a bit higher; ast occurrence of ladinium longicornutum sphaeridium LB: first occurrence of anaphrissa eridium complex cerviculum LB: first occurrence of Dingodinium Paragonyaulacysta LB: last occurrence of LB: first occurrence of Hystrichodinium solare culata lis Tenua americana cysta eilema LB: first occurrence of - - - zones , Cassicu- Tany Batiola- Batioladi , , , Cassicu , zones zones , Nelchi- Sirmiodiniopsis spp. zones ? ? ? ? ? – DZ5 DZ3 DZ2 DZ8 DZ7 DZ6 DZ4 spp., orbis Paragonyaulacysta Pareodinioideae analogus cappilosa

Aldorfia sibirica

DZ1: dinium varigranosum LB: first occurrence of nium varigranosum lasphaeridia reticulata lasphaeridia reticulata osphaeridium magneticum

Canningia ?spinosum ?spinosum Dingodinium Zone

nopsis kostromiensis

?borealis Paragonyaulacysta – Aldorfia sibirica LB: first occurrence of UB: last occurrence of Nelchinopsis kostromiensis Aprobolocysta eilema 004 up to Aprobolocysta galeata North Siberia, lower

and higher from this work

Berriasian after Nikitenko et al., 1997) al., et (Zakharov

zones Ammonoid tolli kochi sibiricus analogus bojarkensis quadrifidus ramulicosta bidihotomus meseznikowi astieriptychus klimovskiensis - , zones – zones ) zones Hystri – Cribro solare – zones zones ?albertii

? sp. A ( deposits Continental of the upper Dingodinium (LB: upper part ?borealis cerviculum Volgian Substage) Tenua americana Paragonyaulacysta dinocyst zones LB: first occurrence of chodinium Dingodinium Subpolar Urals Tenua americana LB: first occurrence of

Ambonosphaera delicata

peridinium muderongense Muderongia simplex Nelchinopsis kostromiensis Ambonosphaera delicata LB: first occurrence of Gardodinium trabeculosum

insolutus analogus (Lebedeva and Nikitenko, 1998) ramulosus zo- nes skii noid color kochi versi- kensis bojar- payeri ammo- michal- - - - , Zone Zone - Canin LB: ac- a, Exiguis Stephodi Gonyaulacysta Zone. Zone Ellipsoidictum , ? ; last occurrence ?magnoserratus

Zone ssl, 1990) ö Protoellipsodinium ; last occurrence of Germany , Muderongia tetracantha Northwestern (Pr cornutum a, Apteodinium comptum Batioladinium longi , Coronifera oceanic Exiguisphaera plectilis of Spiniferetis Cymososphaeridium validum Pterodinium premnos phaera plectilis of Cassiculasphaeridia magna LB: first occurrence of gia pistic Coronifera oceanica me LB: first occurrence of teichos reticulatum densispinum nium spinulosum LB: first occurrence of Impagidinium alectophorum - - - - Hystri Pseudo Subzone Zone Subzone ; last occur- arborispinum Circulo Callaiospha- , asymmetri- ? Stanfordella cf. , Tanyosphaeridi- Zone Subzone cf. Denmark Hystrichodinium , Subzone. LB: first occur- Dichadogonyaulax (Davey, 1982)

Rotosphaeropsis thule

Batioladinium longicornu tum rence of um boletum eridium cum furcatum ordocavata (Contd.) Zone

LB: last occurrence of Endoscrinium pharo Rotosphaeropsis thule

Spiniferites ramosus Amphorula expirata LB (the upper Portlandian base): acme of dinium compta LB: first occurrence of Batioladini- um pomum, Aldorfia dictyota Pseudoceratium pelliferum Discorsia nanna Discorsia Gochteodinia villosa Gochteodinia Zone

LB: first occurrence of

LB: first occurrence of rence of ceratium pelliferum culmula

chospaeridium

upper upper lower upper lower Substage lower middle lower upper

Stage Barremian Hauterivian Valanginian Berriasian Table 1.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 597 , , , Cas- , , (near Cassicu- ; , ?spinosum longicornu- longicornu- . . . ; ; ; Cassiculas- D B B , , , , ?borealis Hystrichodinium Hystrichodinium

(above the middle), ?cretacea , ,

Pseudoceratium pel- , ; ; ?albertii ?albertii

Cribropereidinium con- Sirmiodinium grossii Trichodinium ciliatum ; Tubotuberella apatela , Stanfordella ; , Gardodinium trabeculosum ; , ; Batioladinium jaegeri Batioladinium jaegeri Paragonyaulacysta Dingodinium Gardodinium trabeculosum Dingodinium ; Circulodinium distinctum Circulodinium distinctum Circulodinium distinctum 1993, Hakansson et al., 1981) Muderongia simplex Muderongia simplex Muderongia simplex ?edvardsii pulchrum pulchrum . . . Oligosphaeridium complex Oligosphaeridium complex Achomosphaera neptunii Oligosphaeridium complex C H H ; Greenland (Piasecki, 1979; Nohr-Hansen, , , , ; ; ?asterigium . Proximate Gonyaulacoideae: fossum Pareodinioideae: tum Ceratiaceae: liferum Aeroligeraceae: chorate: voigtii siculasphaeridia magna phaeridia magna Aeroligeraceae: chorate: O the base); Ceratiaceae: other proximate: Aeroligeraceae: chorate: voigtii lasphaeridia magna Pareodinioideae: tum Ceratiaceae: other proximate: Proximate Gonyaulacoideae: Tubotuberella apatela other proximate: Cassiculasphaeridia magna chorate: Proximate Gonyaulacoideae: Heslertonia heslertonensis Sirmiodinium grossii Pareodinioideae: ; exiguum ; Batioladini- Batioladini- ; . ? ; ; ; ; , , Muderongia B , , (above the middle), ; ; Nelchinopsis kostromien- 1974) ; ; ; Batioladinium jaegeri Pareodinia ceratophora Pareodinia ceratophora Dingodinium cerviculum Dingodinium cerviculum Circulodinium distinctum Circulodinium distinctum Senoniasphaera jurassica Circulodinium distinctum Pseudoceratium pelliferum Muderongia simplex Muderongia simplex Oligosphaeridium complex Oligosphaeridium complex Achomosphaera neptunii Oligosphaeridium complex ; Boreal Canada (McIntyre, Brideaux, 1980; Davies, 1983; Van Helden, 1986; Jenkins et al., Lithodina stoveri ?asterigium , . Pareodinioideae: Ceratiaceae: simplex Aeroligeraceae: other proximate: chorate: Ceratiaceae: Pareodinioideae: chorate: Aeroligeraceae: Proximate Gonyaulacoideae: sis pareodinioideae: um varigranosum Aeroligeraceae: chorate: um varigranosum Ceratiaceae: other proximate: chorate: O Aeroligeraceae: Taxa in common with dinocysts from North Siberian sections , , ; , (from Dingo- Dingo- Nel- , , , Paragon- Paragon- muderon- , , ?asterigium ? Muderongia . ; ; spongiosum , O . A , ?cretacea

; Sirmiodinium grossii Zone), Tubotuberella rhombi- Tubotuberella rhom- , Wallodinium luna Wallodinium luna Heslertonia heslertonensis , Cribroperidinium Wallodinium luna Stanfordella , Davies, 1983) ; , s (at the base) ; Oligosphaeridium complex ; Batioladinium jaegeri Pareodinia ceratophora Pareodinia ceratophora Cyclonephelium cuculliforme Oligosphaeridium complex Circulodinium distinctum Buchia keyserlingi ?borealis ?boreali

Apteodinium granulatum Arctic Canada (Williams et al., 1974; Oligosphaeridium complex , Microdinium opacum ; , ; Bideaux, Fisher, 1976; Bujak, Williams, 1978; albertense . dinium cerviculum chorate: other proximate dinocysts: UnstudiedPareodinioideae: Unstudied Unstudied Pareodinioideae: Proximate dinocysts: chorate forms: formis yaulacysta Aeroligeraceae: biformis Proximate Gonyaulacoideae: Wrevittia helicoidea chinopsis kostromiensis Sirmiodinium grossii yaulacysta O simplex other proximate dinocysts: dinium cerviculum chorate dinocysts: the base of Ceratiaceae: Pareodinioideae: gense Comparison of the Lower Cretaceous dinocyst assemblages from northern regions Eurasia and America Stage, substage Lower Barremian Upper Hauteri- vian Lower Hauteri- vian Berriasian Proximate Gonyaulacoideae: Lower Valan- ginian Table 2.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 598 PESTCHEVITSKAYA

, voig- voig- Sir- , longi- . . , reticu- reticu- reticu- Oligo- . H H . . . , B ; C C C ; , M. extensi- , , , ; ; , ?albertii . Tubotuberella , D ; , crucis crucis ; . . (abundant), (abundant), ; M M M. crucis , , , ; ; ; Nelchinopsis kostromien- Sirmiodinium grossii Wrevittia helicoidea Fromea amphora , Spiniferites ramosus Oligosphaeridium complex Aldorfia dictyota ?edvardsii ,

(sometimes abundant) ?albertii Trichodinium ciliatum

, Aproblocysta neista Batioladinium varigranosum Batioladinium varigranosum Cassiculasphaeridia magna Cassiculasphaeridia magna Dingodinium minutum Cassiculasphaeridia magna Cassiculasphaeridia magna , Muderongia simplex Muderongia simplex Muderongia simplex ; Heslertonia heslertonensis Hystrichodinium pulchrum Hystrichodinium pulchrum Oligosphaeridium diluculum , Gardodinium trabeculosum Dingodinium Cribroperidinium ; , , Pseudoceratium pelliferum ?spinosum , , (sometimes significant), (sometimes significant), . Pareodinioideae: Proximate Gonyaulacoideae: sis tii va other proximate: lata chorate: tii lata chorate: (sometimes abundant) Unstudied chorate: Ceratiaceae: sphaeridium complex Proximate Gonyaulacoideae: cornutum Ceratiaceae: Pareodinioideae: Proximate Gonyaulacoideae: miodinium grossii apatela Tubotuberella apatela other proximate: Ceratiaceae: D Pareodinioideae: other proximate: other proximate: lata , ; ; Apro- , Gardo- Gardod- , , ; Cassiculasphae- ; , (from the middle ; Tubotuberella apatela Hystrichodinium voigtii , Cribroperidinium confos- Nelchinopsis kostromien- Nelchinopsis kostromien- Nelchinopsis kostromiensis ; ?spinosum

neista ; chorate: . ; A Batioladinium longicornutum Cassiculasphaeridia magna Cassiculasphaeridia magna Cassiculasphaeridia magna , ) Muderongia tetracantha ; Dingodinium Achomosphaera neptunii Oligosphaeridium complex Oligosphaeridium complex Nelchinopsis kostromiensis , North Sea (Duxbury et al., 1999; Duxbury, 201) Northwestern Europe (Davey, 1979, 1982) Heslertonia heslertonensis Paratollia (lower part) , Pareodinioideae: bolocysta eilema Proximate Gonyaulacoideae: sum other proximate: dinium trabeculosum Oligosphaeridium complex sis Proximate Gonyaulacoideae: Ceratiaceae: other proximate: Proximate Gonyaulacoideae: sis other proximate: Proximate: ridia magna chorate: inium trabeculosum chorate: chorate: of Taxa in common with dinocysts from North Siberian sections

, ; cru- Gar- Gar- Din- lon- ; . , , , . Stan- Apro- M Pseudo- B , , , , , ; ; Dingodinium Pseudocera- , , krutzschii krutzschii krutzschii . . . staurota staurota crucis Hystrichodinium Hystrichodinium . . . W W W , , , , , M M M , , , Trichodinium ciliatum Cribroperidinium confos- Tubotuberella apatela Tubotuberella apatela ; , ; ; ; Davey, 2001) neista Vesperopsis fragilis Nelchinopsis kostromiensis ; . , , ; ; A Batioladinium longicornutum Batioladinium varigranosum Batioladinium varigranosum Wallodinium luna Wallodinium krutzschii Wallodinium luna Wallodinium luna , Circulodinium distinctum ; Muderongia simplex Muderongia simplex Muderongia simplex ?spinosum . ; pulchrum pulchrum ?albertii D

. . Achomosphaera neptunii Oligosphaeridium complex Oligosphaeridium complex , ?edvardsii H tetracantha H . , , . C England (Duxbury, 1977, 1980; Harding, 1986; , M , dodinium trabeculosum chorate: voigtii other proximate: tium pelliferum Unstudied Proximate Gonyaulacoideae: Heslertonia heslertonensis Proximate Gonyaulacoideae: sum fordella ?cretacea cis Proximate Gonyaulacoideae: Pareodinioideae: bolocysta eilema Ceratiaceae: dodinium trabeculosum chorate: voigtii Pareodinioideae: gicornutum Ceratiaceae: aeroligeraceae: godinium Pareodinioideae: Ceratiaceae: other proximate: ?albertii chorate: ceratium pelliferum other proximate: other proximate: (Contd.) Stage, substage Lower Barremian Lower Valan- ginian Upper Hauteri- vian Berriasian Proximate Gonyaulacoideae: Lower Hauteri- vian Table 2.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 599

, , , , stau- . ?mud-

M , ; (at the very ; Nelchinopsis Dingodinium , , crucis . M ?borealis ?edvardsii ,

. C Chlamydophorella nyei Chlamydophorella nyei Chlamydophorella nyei , , , , Cribroperidinium spongiosum , . ; A , ; Hystrichodinium pulchrum , ; ; ; (~from the middle) reticulata reticulata reticulata staurota . . . Oligosphaeridium complex . ; C C C Chlamydophorella nyei ; ; , M Paragonyaulacysta , , , , , , Muderongia simplex Gardodinium trabeculosum , ; ; voigtii ; O. complex . Spiniferites ramosus crucis , , ?borealis H .

Sirmiodinium grossii , , M , ; ; Wallodinium krutzschii (persistent), , Cribropereidinuum confossum Apteodinium granulatum Sirmiodinium grossii Wallodinium krutzschii Wallodinium krutzschii , , Dapsilidinium multispinosum , Wallodinium krutzschii , Batioladinium varigranosum Batioladinium varigranosum Paragonyaulacysta Cassiculasphaeridia magna Cassiculasphaeridia magna Cassiculasphaeridia magna Cassiculasphaeridia magna Batioladinium varigranosum Circulodinium compta Circulodinium distinctum Circulodinium distinctum Wrevittia helicoidea , Muderongia simplex Muderongia simplex Aptea anaphrissa Fromea amphora , Oligosphaeridium complex ; , Spiniferites ramosus Oligosphaeridium diluculum Hystrichodinium pulchrum Cauca parva Pseudoceratium pelliferum ; , Unstudied Ceratiaceae: Pareodinioideae: Ceratiaceae: Pareodinioideae: Ceratiaceae: Proximate Gonyaulacoideae: base) other proximate: other proximate: erongense Pareodinioideae: rota other proximate: H. voigtii ?spinosum chorate: Aeroligeraceae: Fromea amphora chorate: Gardodinium trabeculosum Aeroligeraceae: chorate: kostromiensis Gardodinium trabeculosum Aeroligeraceae: chorate: other proximate: Pareodinioideae: , tetra- tetra- ?mud- . . . multis- Nelchi- M M Dapsili- Stanfor- C Cassicu- Cassicu- ; ; , , , , “ , , , , luna luna . . simplex simplex W W . . , , M M ?edvardsii ?edvardsii , , . . Gardodinium trabecu- Gardodinium trabecu- C C Dapsilidinium , , , , Aprobolocysta neista , , Taxa in common with dinocysts from North Siberian sections jaegeri complex . Circulodinium distinctum Circulodinium distinctum . Endoscrinium campanula , , B , Oligosphaeridium complex O , ; ; , , Wallodinium krutzschii Wallodinium krutzschii Muderongia australis Muderongia australis , , , , voigtii ?diutina voigtii ;

; . . H H , , Dingodinium cerviculum Dingodinium cerviculum , , Wrevittia Cribropereidinium confossum Cribropereidinium confossum , Northern Germany (Prössl, 1990) Norway (Aarhus et al., 1986) ” reticulata reticulata . . C C Odontochitina operculata ; , , , ; exanguia ; . Batioladinium longicornutum Batioladinium longicornutum Aprobolocysta eilema Chlamydophorella nyei Wallodinium krutzschii Chlamydophorella nyei S Cyclonephelium brevispinatum Cyclonephelium brevispinatum , Pseudoceratium pelliferum Pseudoceratium pelliferum Nelchinopsis kostromiensis staurota staurota ordinale , . . ; multispinosum . Hystrichodinium pulchrum Hystrichodinium pulchrum ” M M “ G , , , ; ?cretacea

eilema . chorate: lasphaeridia magna losum Aeroligeraceae: cantha other proximate: cantha other proximate: Proximate Gonyaulacoideae: della chorate: dinium lasphaeridia magna losum Aeroligeraceae: A Ceratiaceae: other proximate: nopsis kostromiensis Pareodinioideae: pinosum erongense Pareodinioideae: Ceratiaceae: Proximate Gonyaulacoideae: Pareodinioideae: Unstudied Proximate Gonyaulacoideae: (Contd.) Stage, substage Upper Hauteri- vian Lower Hauteri- vian Lower Barremian Berriasian Unstudied Proximate Gonyaulacoideae: Lower Valan- ginian Table 2.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 600 PESTCHEVITSKAYA ;

, ; ; ; (in the orbis Nelchinop- . , S ; , ; Dingodinium tetracantha , Imbatodinium . Nelchinopsis kos- , (at the very base) ; , M magna , . Tenua americana C Cassiculasphaeridia re- , Dingodinium cervicu- Dingodinium cervicu- C. nyei , , , , , Microdinium opacum Cassiculasphaeridia reti- longicornutum , crucis ?borealis ?borealis , . .

; B M , , muderongense grossii . ? Stanfordella exanguia Tubotuberella rhombiformis Apteodinium maculatum S , W. krutzschii , Hystrichodinium solare Apteodinium granulatum varigranosum apatela , , . . ; Wallodinium krutzschii T Paragonyaulacysta Paragonyaulacysta B Chlamydophorella nyei Wallodinium krutzschii Chlamydophorella nyei ; , Circulodinium distinctum Cyclonephelium cuculliforme , orbis . e in the designated interval. Muderongia simplex S ; magna complex Cribroperidinium . . , Cassiculasphaeridia reticulata C Oligosphaeridium diluculum O , ?albertii , Gardodinium trabeculosum et al., 1999; Riding Beizel' 2002) . , D Wallodinium luna , , rhombiformis Subpolar Urals and Siberia (Il'ina, 1988; Fedorova et al., 1993; . Shulgina et al., 1994; Lebedeva and Nikitenko, 1998; Kirichkova chorate: ticulata Pareodinioideae: tromiensis culata Pareodinioideae: Proximate Gonyaulacoideae: T kondratjevii other proximate: lum other proximate: Pareodinioideae: Ceratiaceae: Proximate Gonyaulacoideae: sis kostromiensis lum Aeroligeraceae: other proximate: chorate: Proximate Gonyaulacoideae: lower part), Unstudied Aeroligeraceae: ?albertii , , , , , , , ?al- ; ; . D , , , ; ; ; ; simplex ; varigrano- . cylindricum . ; trabeculosum . ; ; ; ; M . B W , krutzschii krutzschii Stanfordella fas- G. trabeculosum , G , krutzschii . . , , , . amphora Fromea amphora ; Hystrichodinium Hystrichodinium . , W W W , , F , , ?staffiensis ,

nyei ,

; ; Gardodinium trabeculo- eilema ; ; Sirmiodinium grossii , , . Apteodinium maculatum Apteodinium maculatum Apteodinium maculatum Apteodinium maculatum krutzschii . A , W , reticulata T. speetonense Sirmiodinium grossii . , , Spiniferites ramosus C reticulata

luna , , . Ambonosphaera Pareodinia ceratophora Batioladinium jaegeri Batioladinium varigranosum Pareodinia ceratophora Wallodinium luna Wallodinium luna W Wallodinium luna , Circulodinium distinctum Senoniasphaera jurassica Circulodinium distinctum Chlamydophorell Chlamydophorell nyei nyei Chytroeisphaeridia chytroides , , . , Pseudoceratium pelliferum Muderongia simplex Muderongia simplex C Moscow basin (Iosifova, 1996) , neptunii H. voigtii H. voigtii . , , A Oligosphaeridium complex Oligosphaeridium complex Taxa in common with dinocysts from North Siberian sections Tubotuberella apatela Chlamydophorella nyei , Cassiculasphaeridia reticulata , Aprobolocysta neista , , cylindricum cylindricum ?albertii campanula . . . . Proximate Gonyaulacoideae: Tubotuberella apatela W Proximate Gonyaulacoideae: Pareodinioideae: E Pareodinioideae: sum Ceratiaceae: other proximate: Proximate Gonyaulacoideae: Proximate Gonyaulacoideae: Aeroligeraceae: Aeroligeraceae: chorate: other proximate: Unstudied Unstudied Trichodinium ciliatum tigiata pulchrum chorate: W Cassiculasphaeridia reticulata Aeroligeraceae: chorate: pulchrum N. kostromiensis Pareodinioideae: Ceratiaceae: Cassiculasphaeridia D Pareodinioideae: other proximate: Ceratiaceae: other proximate: bertii sum , , , , , , ; Mu-

, , , ?borea- Dapsili- Cymo-

Cribrop- , , , australis . ?exiguum ; M. staurota

M (from the up- , , Endoscrinium Wrevittia heli- ; (up to the middle) Cymozosphaeridi- ?cretacea

” ; ; ,” ; M. australis ; ; ; Paragonyaulacysta Batioladinium jaegeri Batioladinium jaegeri Batioladinium , Gardodinium trabeculosum Gardodinium trabeculosum phoenix Circulodinium distinctum Circulodinium distinctum tetracantha M. asymmetrica . , “ Barents Sea shelf Aptea anaphrissa Pseudoceratium pelliferum M ” Stanfordella , ?edvardsii ,

Muderongia simplex multispinosum Oligosphaeridium complex Oligosphaeridium complex “ phoenix staurota “ longicornutum longicornutum (Aarhus et al., 1990; Smelror al. 1998) . . . lis um other proximate: Chlamydophorella nyei Aeroligeraceae: Aptea anaphrissa chorate: dinium derongia simplex B M. tetracantha Ceratiaceae: ereidinium Pareodinioideae: Proximate Gonyaulacoideae: campanula Proximate Gonyaulacoideae: coidea other proximate: Chlamydophorella nyei Aeroligeraceae: chorate: sosphaeridium M B Ceratiaceae: per part), Pareodinioideae: Pareodinioideae: Nelchinopsis kostromiensis (Contd.) Stage, substage Berriasian Pareodinioideae: Upper Hauteri- vian Lower Valan- ginian Lower Hauteri- vian Lower Barremian Note: first or last occurrenc have in bold or underlined, when they Names of species in common with North Siberian taxa are given Table 2.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 601 , , , (SC); : (SC) (AC) : (AC); , (SC) , : (AC); : (SC) rioultii aff. Pilosidinium filiatum , Biorbifera , : (AC); : (AC); : (SC); Lanterna sportula , Prolixosphaeridium “spissum,” atiacasphaera agglutinata Systematophora orbifera Leptodinium mamilliferum Moesiodinium raileanui , circulare Amphorula metaelliptica Cantulodinium arthuriae Sentusidinium Circulodinium hirtellum , B Trichodinium erinaceoides (ûä) , ? Scriniodinium crystallinum scissum , , ? Lithosphaeridium siphoniphorum : (SC) , merica , , Ctenidodinium elegantum , Rhynchodiniopsis serrata Kallosphaeridium Valvaeodinium atlanticum Ctenidodinium : (SC) Leptodinium episomum Tubotuberella rhombiformis Apteodinium apiatum Biorbifera johneingii , Caligodinium aceras , , Imbatodinium kondratjevii Ellipsoidictium cinctum rope, (NE) South England and northern regions in bold are species found the studied sections : (AC) Gochteodinia judilentinae , Systematophora complicata , Recognizable in Canada only (SC) Odontochitina operculata

Subtilisphaera perlucida Cribroperidinium spinoreticulatum ” Leptodinium episomum , , : (AC) (SC, AC) , , Subtilisphaera Batioladinium jaegeri , (SC) , Cribroperidinium sepimentum Fromea senilis (AC); , , Batiacasphaera agglutinata , ?circulare Pseudoceratium retusum

, ?exiguum : (SC); ?scissum

Rhynchodiniopsis serrata “tomaszowensis Surculosphaeridium

, , Circulodinium hirtellum johnewingii Hystrichosphaeridium recurvatum Batioladinium Batioladinium varigranosum Fromea triquetra Endoceratium dettmanae Pseudoceratium “regium” ?pirnaensis ?longifurcatum Cylonephelium vannophorum Circulodinium attadalicum Apteodinium apiatum Ctenidodinium Muderongia Cribroperidinium saetigerum Kallosphaeridium Oligosphaeridium albertense (G, NE) (G, NE) (BS, MB) Palynological events (G, NE, BS) (NE, AC, SC); (SC, S); (NE, SR, S) (BS,G) (SR, MB); : (G, NE); spinosum ? Spiniferites primaevus (everywhere except for Russia); Gonyaulacysta eisenackii Cassiculasphaeridia magna Nelchinopsis kostromiensis (SR, MB); (G, NE, SR); Dingodinium Paragonyaulacysta capillosa Nelchinopsis kostromiensis Gonyaulacysta jurassica Aptea anaphrissa : (SC, G) (G, MB); Tanyosphaeridium boletus , acme of Kleithriasphaeridium “simplicispinum” Egmontodinium toryna Phoberocysta neocomica piniferites alatus (MB, S) Kiokansium polypes (SC, BS, G); (SR); Recognizable in different regions of North Eurasia , (NE, SR, MB) (NE, BS, MB) (everywhere except for MB) Endoscrinium campanula

, (every where except for Russia); (SR, NE, MB); (SC, AC, MB); (G, BS, MB) (NE, SR, G, S); (G, NE, MB); S ?gochtii

(SR, S); Aptea anaphrissa

Lithodinia pertusa Cassiculasphaeridia reticulata Oligosphaeridium diluculum Oligosphaeridium complex Batioladinium Cauaca parva Cribroperidinium confossum Ellipsoidictyum imperfectum Cribroperidinium orthoceras . First and last occurrence of the Lower Cretaceous dinocyst species established in different northern regions Eurasia A acme of Circulodinium distinctum Ellipsoidictyum sagena Batioladinium pelliferum Occisucysta tentorium Protoellipsodinium clavulum

Epoch late early middle late early late early late early

Age Barremian Hauterivian Valanginian Berriasian regions of Germany, France and Denmark, (SR) subpolar regions, (BS) Barents Sea shelf, (MB) Moscow basin, (S) Siberia; printed Notes. – first occurrence, – last occurrence(SC) southern and southeastern Canada, (AC) Arctic (G) Greenland, West Eu of North Siberia. Table 3

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 602 PESTCHEVITSKAYA Egmonto- , Dapsilidinium , Egmontodinium toryna Batioladinium pelliferum Endoscrinium granulatum Pseudoceratium pelliferum

; Kleithriasphaeridium corrugatum Cribroperidinium exilicristatum Heslertonia heslertonensis

, Recognizable in Greenland only Batiacasphaera spumosa, Prolixosphaeridium Batioladinium pelliferum, Cribroperidinium ?edvardsii dierense, Sentusidinium verrucosus, Wallodinium elongatum Cribroperidinium exilicristatum warrenii dinium toryna Desmocysta plecta , - , , (NE - (NE) (NE) (NÖ) (NE) (NE) (SR) (SR); : (NE) : (NE) : (BS) Pterodi (NE, BS) , (NE, SR); pongiosus , s ?

Systematophora (NE; BS) Spini-

, , S. scoiacea

Canningia grandis : (NE) , Stiphrosphaeridium Kalyptea diceras , : (BS) Spiniferites

Cribroperidinium colum piniferites fenestratus , Rotosphaeropsis thule Tehamadinium daveyi: Endoscrinium h‡rÓ Amphorula expirata Rhynchodiniopsis cladopho Sentusidinium separatum Lagenorhytis delicatula , Oligosphaeridium junctum ?diutina , ribroperidinium ?cornutum

, , Riguadella aemula (NE); S Stiphrosphaeridium arbustum , Desmocysta simplex Trichodinium scarburghense

Aprobolocysta eilema , Egmontodinium polyplacophorum Mendicodinium groenlandicum Wrevittia Canningia duxburyi

, , Systematophora palmula, (NE, BS); C Ascodinium fissilum , : (NE); Papuadinium apiculatum Aprobolocysta extrema, , , Exiguisphaera phragma (NE, BS); Gochteodinia verrucosa Circulodinium compta , Batiacasphaera mica Kleithriasphaeridium porosispinum Leptodinium subtile Muderongia aequicorna , , Dapsilidinium , Tanyosphaeridium magneticum ,” ,” Australisphaera fragilis, areolata Cymososphaeridium validum, Wallodinium cylindricum Aprobolocysta neista , Hystrichodinium ramoides Subtilisphaera perlucida , , , Palynological events diaphanum “ : (NE); ?cingulatus : (NE) “ Tetrachacysta spinosigibberosa Dichadogonyaulax culmula : (NE); Muderongia asymmetrica , Aprobo- , , , ra ferites alatus Microdinium opacum Cribroperidinium fragilis Nexosispinum vetusculum nium Leptodinium millioudii : (NE); (SR) , : (BS) (SR) , : (CE); Cribroperidinium ?schizablata , : (NE);

Florentinia interrupta (BS); , Hystrichodinium furcatum

Tanyosphaeridium salpinx , , Tehamadinium evitti Ellipsodinium reticulatum , , , Muderongia aequicora Wrevittia cassidata Aptea anaphrissa ); Protoellipsoidinium spinosum , dictyophorum , Nexosispinum vetusculum SR ) Ctenidodinium , : (NE) NE (SR) : (SR); : (NE); (NE, ( Muderongia pariata ) Systematophora palmula : (NE) Impagidinium diversum , Impagidinium alectophorum , : (SR); NE Cometodinium ?comatum ) , Nematosphaeropsis vetuscula , ?conutum ( Gardodinium ordinale Cymososphaeridium ?phoenix

, : (NE) , , BS (NE) Stanfordella ordocavata : (èÖ); ( M. tetracantha , Muderongia imparilis , Diacanthum hollisteri Taleisphaera hydra , , Downiesphaeridium aciculare , Hystrichodinium compactum (NE, SR); , Recognizable only in northwestern Europe and Barents Sea shelf Muderongia extensiva (NE, SR); (NE, SR); , ) Cribroperidinium K. eoinodes , Carpodinium granulatum BS Muderongia staurota Gonyaulacysta compta ,” Florentinia mantellii

(NE) Cribroperidinium boreas , ); Atopodinium polygonale (NE) Dapsilidinium multispinosum Gardodinium trabeculosum multifurcata ” ( ,” Sepispinula ancorifera Muderongia crucis Gonyaulacysta dualis Oligosphaeridium fenestratum , , Lagenorhytis delicatula Prolixosphaeridium granulosum ?sarmentum (SR) , , Spiniferites speetonensis

Rhynchodiniopsis fimbriata Impletosphaeridium tribuliferum: , , , , , Circulodinium brevispinosum Palaeoperidinium cretaceum (NE, BS) (NE) NE, BS : (NE); , , Coronifera oceanica Subtilisphaera terrula subsp. ( , , tabulata alveolatum comptum Exiguisphaera plectilis Exochosphaeridium phragmites “ “ ?tenuiceras (NE, SR); , “

, ?pannosa Downiesphaeridium multispinosum

, , abundance of ?diutina

?perforobtusa

Canningiopsis Kleithriasphaeridium Achomosphaera ramulifera, Nyctericysta Batiacasphaera mica Pterodinium premnos Apteodinium reticulatum Cerbia tabulata

Fromea quadrugata

Nematosphaeropsis scala Discorsia nanna Systematophora silybum Exiguisphaera phragma . (Contd.) Gochteodinia verrucosa Stiphrosphaeridium arbustum Fromea complicata Vesperopsis fragilis Cribroperidinium Aprobolocysta eilema: locysta neista Cymososphaeridium validum Gonyaulacysta anglese Gochteodinia villosa Subtilisphaera terrula Wrevittia Rhynchodiniopsis aptiana laminaspinosum Pseudoceratium nudum Cribroperidinium Canningiopsis colliveri Wrevittia Kleithriasphaeridium fasciatum Hystrichosphaeridium arborispinum Cribroperidinium

Epoch late early middle late early late early late early

Age Barremian Hauterivian Valanginian Berriasian Table 3

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 603 ) - - Go NE, SC , Hystri ( , : (NÖ, MB); (NE, MB) ) ); Isthmocystis SC, NE SC, NB (NE, MB) ( distincta

” ( Pseudoceratium , Recognizable in Boreal gochtii nyaulacysta teichos chogylon stolidota Callaiosphaeridium asymmet- ricum Phoberocysta Aprobolocysta neista “ tabulata neptunii Achomosphaera Spiniferites dentatus - , (AC, S) (AC, S) (G, NE); (AC, G, S) , (NE, S) Batioladi Apteodinium Trichodinium

, ?vitrea (AC, S) Cyclonephelium

(AC, G, SR, NE) Paragonyaulacysta ?borealis (AC, G) : regions only province only reticulatum : (AC, NE); tum cuculliforme Recognizable in subpolar Batioladinium longicornut- castanea nium longicornutum Cribroperidinium muderongense uncinata Nyctericysta Pseudoceratium toveae Tubotuberella Cyclonephelium cuculliforme Spiniferites ramosus , , ,

, , Achomosphaera Pareodinia hallosa , Escharisphaeridia rudis Leptodinium eumorphum Aprobolocysta galeata Cribroperidinium globatum , Muderongia brevispinosa Ambonosphaera delicata verdieri Dingodinium tuberosum Cribroperidinium granulatum F. fragilis ” , Trichodinium speetonense , , , , Cyclonephelium intonsum , Cribroperidinium , huguoniotii F. amphora “ , ? Recognizable in Siberia only

Stanfordella exanguia tensiftense Tanyosphaeridium variecalamus T. magneticum Muderongia australis Aprobolocysta galeata Athigmatocysta glabra P. expolitum Vesperopsis mayi abaculum Druggidium jubatum Oligosphaeridium Tenua americana Achomosphaera verdieri Pareodinia hallosa Sepispinula Ambonosphaera delicata Palynological events , , , Apteodi- , Hystrichogy- , Gonyaulacysta

Chitroeisphaeri- Senoniasphaera , , , Systematophora ovata ?staffinensis Gonyaulacysta dentata

, , Wallodinium luna Lithodinia arcanitabula- Apteodinium granulife- , , , , Prolixosphaeridium conulum Cribroperidinium cooksoniae Protobatioladinium rossicum Cometodinium whitei, Lithodinia , , Epitricysta vinkensis ?brevispinosa

, , teichos Gardodinium lowii, Ambonosphaera Surculosphaeridium cribrotubiliferum Tubotuberella apatela nium deflandrei N. corniculatum , , Apteodinium gerasimovii , Gardodinium lowii Warrenia , , , , , Stanfordella fastigiata rum Microdinium densigranulatum , Cribroperidinium , , , Impagidinium orocaviopse , Canningia reticulata Protoellipsodinium mugatae Lithodinia perforata , , , Cyclonephelium maugaad , Trichodinium discus ?brevispinosa

Impagidinium ordocaviopse , , Trichodinium discus , Kiokansium prolatum Lithodinia perforata Lithodinia diaphana , Heslertonia pellucida , Protoellipsodinium seghire yclonephelium maugaad , , , Warrenia ta dia cerastes jurassica lon membraniforum Neodiacrodium brevispinosum Canningia grandis Apteodinium gerasimovii , C Prolixosphaeridium parvispinosum , , , , Pseudoceratium iveri Recognizable in the Moscow basin only , Pseudoceratium aulaeum ?hadrum ,

Microdinium densigranulatum Rhombodella vesca , Epitricysta vinkensis , ,

Apteodinium granuliferum volkovae Protobatioladinium rossicum Tehamadinium daveyi Muderongia brevispinosa . (Contd.) Subtilisphaera cheit N. timofeevii Gardodinium attenuatum Cribroperidinium cooksoniae Hystrichogylon membraniforum P. touile Leptodinium diaphana Apteodinium deflandrei Cometodinium whitei Cyclonephelium hexalobosum Apteodinium maculatum Gardodinium trabeculosum

Epoch late early middle late early late early late early

Age Barremian Hauterivian Valanginian Berriasian Table 3

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Table 4. Palynological substantiation of dinocyst reference level established in North Siberia

Dinocyst levels Palynological event Regions, where palynological events are recognized

Lower boundary: First occurrence of Hystricho- Subpolar Urals, beginning from the lower Hauterivian (Lebedeva and Ni- Hystrichodinium solare, Mude- dinium solare kitenko; 1998) rongia spp. (DA5); lower Hauterivian, middle Ho- First occurrence of Muderongia Barents Sea shelf, beginning from the upper Valanginian (Aarhus et al., 1986) molsomites bojarkensis staurota Northwestern Europe, beginning from the upper Hauterivian (Duxbury, 1977; Harding, 1986; A Stratigraphic…, 1992) First occurrence of Muderongia Barents Sea shelf, beginning from the Hauterivian (Aarhus et al., 1990; Smel- tetracantha ror et al., 1998); Northwestern Europe, beginning from the upper Hauterivian (Duxbury, 1977; Davey, 1979; N¿hr-Hansen, 1993); crucis/tetracantha: in northwestern Europe since the upper part of the lower Valanginian (Polyptychites) (A Stratigraphic…, 1992); in the Subpolar Urals since the upper Valanginian (Lebedeva and Nikitenko; 1998) Diversification of the genus Valanginian assemblages commonly include two species M. simplex + M. Muderongia cruces and M. tomaszovensis or M. perforata for the lower substage (Bujak and Williams, 1978; Davey, 1979; Davies, 1983; A Stratigraphic…, 1992) and + M. extensiva or M. staurota for the upper one (Duxbury, 1977; Fisher and Riley, 1980; Aarhus et al., 1986); lower Hauterivian: 4 species M. tetracantha, M. asymmetrica, M. aequicorna, and M. australis in the Barents Sea shelf (Aarhus et al., 1990); upper Hauteriv- ianÐBarremian: 2Ð4 species in northwestern Europe and Greenland (Duxbury, 1977, 1980, 2001; A Stratigraphic…, 1992; Nøhr-Hansen, 1993) LB Aldorfia sibirica, Apro- First abundance peak of Dingo- Persistent abundance is more typical of the upper Valanginian and Hauterivi- bolocysta galeata, (DA4): mid- dinium cerviculum an: Norway (Aarhus, 1986), Subpolar Urals (Lebedeva and Nikitenko, 1998) dle ramulicosta Lower boundary Oligosphae- First occurrence of Mude- Northern areas of West Europe (Daveey, 1979; A Stratigraphic…, 1992) ridium complex, rongia cruces (borehole Ro- Dingodinium cerviculum manovskaya) (DA3): lower Valanginian, middle Euryptychites quadrifi- First occurrence of Oligo- First occurrence practically isochronous in the lower part of the lower Valang- dus sphaeridium complex inian: Canada (Bujak and Williams, 1978; Brideaux and McIntyre, 1980; Davies, 1983), Greenland (Piasecki, 1979), northwestern Europe (Duxbury, 1977, 2001; Davey, 1979; Aarhus et al., 1986; A Stratigraphic…, 1992) First occurrence of Dingodin- In West Europe first occurrence in the upper Volgian Substage (Davey, 1979); ium crviculum In Arctic Canada and Siberia first occurrence in lower part of the lower Val- anginian (Brideaux and McIntyre, 1980; Davies, 1983; Lebedeva and Nikiten- ko, 1998) Lower boundary Eschari- Last occurrence of Dingo- Practically isochronous last occurrence at the Berriasian top: northern areas of sphaeridia spp., Oligosphae- dinium ?spinosum somewhat West Europe (Duxbury, 1977; Davey, 1979; Fisher, Riley, 1980; A strati- ridium spp., Circulodinium spp. lower (Severo-Volo- graphic…, 1992; Duxbury et al., 1999) (DA2): lower Valanginian, gochanskaya) lower part of Neotollia kli- movskiensis Last occurrence of Pargo- Last occurrence in lower part of the lower Valanginian: Arctic Canada (McIn- nyaulacysta ?borealis tyre, Brideaux, 1980), Greenland (Hakansson et al., 1981), Norway (Aarhus et al., 1986), Siberia (Lebedeva and Nikitenko, 1998) Sharply decreased diversity of Ð Pareodinioideae Loer boundary Pareodinioide- First occurrence of Batiola- First occurrence in the mid-Berriasian: Newfoundland (Van Helden, 1986), ae, Cassiculasphaeridia reticu- dinium varigranosum northwestern Europe (Davey, 1982); last occurrence in the mid-Barremian of lata, Batioladinium varigrano- the Barents Sea shelf (Smelror et al., 1998); sum (DA1); upper Berriasian, Characteristic component of Valanginian and Hauterivian assemblages in Surites analogus base northwestern Europe (Duxbury, 1977; A Stratigraphic…, 1992; Davey, 2001) and Moscow basin (Iosifova, 1996) First occurrence of Cassicu- First occurrence at the base of the Bojarkia payeri Zone in the Subpolar Urals lasphaeridia reticulata (Lebedeva and Nikitenko, 1998); Characteristic component of Valanginian, Hauterivian and Barremian assem- blages in northwestern Europe (Duxbury, 1977; Aarhus et al., 1986; A Strati- graphic…, 1992; Davey, 2001) and Moscow basin (Iosifova, 1996) First occurrence of Tanyo- The lowerÐmiddle Valanginian of Arctic Canada (Davies, 1983); the lower sphaeridium magneticum upper Valanginian of the Barents Sea shelf (Smelror et al., 1998); The Hauterivian–lower Barremian of northern Germany (Prössl, 1990)

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 DINOCYST BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS IN NORTH SIBERIA 605

Table 4. (Contd.) Dinocyst levels Palynological event Regions, where palynological events are recognized Canningia spp.ÐNelchinopsis Presence of Nelchinopsis kos- The latest specimens are discovered in lower part of the lower Barremian in kostromiensis Beds (DA8): tromiensis Greenland and northwestern Europe (Nöhr-Hansen, 1993) lower part of the lower Barre- Presence of Aprobolocysta The latest specimens are discovered in lower part of the lower Barremian in mian eilema northwestern Europe (Duxbury, 1980, 2001; A Stratigraphic…, 1992) Lower boundary, Aprobolocys- First occurrence of Aprobolo- First occurrence at the base of the upper Hauterivian (Duxbury, 1977, 2001; A ta eilemaÐA. neistaÐOdonto- cysta eilema Stratigraphic…, 1992) chitina spp. assemblage (DA7): First occurrence of Aprobo- First occurrence in upper part of the lower Hauterivian (Duxbury, 2001) the upper Hauterivian base locysta neista First occurrence of Odonto- First occurrence in the Valanginian of Arctic Canada (Davies, 1983) and since chitina operculata the upper Hauterivian in the Barents Sea shelf and northern Germany (Aarhus et al., 1990; Prössl, 1990 First occurrence of Psedo- First occurrence of Psedoceratium expolitum in the lower Barremian of Mos- ceratium expolitum, Gonya- cow syneclise (Iosifova, 1986); Gonyaulacysta ?kleithria and Cyclonepheli- ulacysta ?kleithria, Cyclo- um intonsum unknown from the BerriasianÐBarremian of North Eurasia and nephelium intonsum America are described from the AptianÐAlbian of South England (Duxbury, 1983) First occurrence of Vesperop- First occurrence of Vesperopsis fragilis in the upper Hauterivian of South En- sis fragilis, V. mayi somewhat gland (Harding, 1986), V. mayi in the upper Barremian of Arctic Canada higher (Nöhr-Hansen, 1993) Last occurrence of Hystrichod- In the Subpolar Urals, forms of similar morphology are established in the low- inium solare er Hauterivian only (Lebedeva and Nikitenko, 1998) Last occurrence of Oligo- Last occurrence in the Turonian of northern Germany (Prössl, 1990); up to the sphaeridium ?asterigium Aptian in Canada (Bujak and Williams, 1978; McIntyre and Brideaux, 1980) and up to the Barremian in Greenland and Barents Sea shelf (Piasecki, 1979; Aarhus et al., 1990; Nöhr-Hansen, 1993; Smelror et al., 1998) Last occurrence of Tenua Last occurrence in the mid-Hauterivian of northern Germany (Prössl, 1990) Americana Diversification of the genus See DK5 “diversification of Muderongia” Muderongia Diversification of the genus In Volgian, Berriasian and Valanginian stages usually 1Ð2 species; in the Hau- Batioladinium terivian and Barremian 1Ð5 species; a sharp diversity increase is established in the lower Hauterivian of Greenland (Piasecki, 1979) and Barents Sea shelf (Aarhus et al., 1990); in the middle Barremian of the Barents Sea shelf (Smel- ror et al., 1998 Diversification of the genus Single dinocysts of this genus are known from the Berriasian and Valanginian Aprobolocysta of northwestern Europe (Davey, 1982; Duxbury, 2001); beginning from the upper Hauterivian, several species (A. eilema, A. neista, A. trycheria, A. gale- ata, and others) persistently occur in England (Duxbury, 2001), Barents Sea shelf (Smelror et al., 1998), and Moscow basin (Iosifova, 1996) Diversity decrease in the genus The genus diversity is highly variable in vertical and lateral directions Oligosphaeridium Lower boundary, Aptea First occurrence of Aptea First occurrence in the mid-lower Hauterivian of the Barents Sea shelf (Aarhus anaphrissaÐOligosphaeridium anaphrissa et al., 1990) and Subpolar Urals (Lebedeva and Nikitenko, 1998); since the up- aff. totumÐBatioladinium longi- per Hauterivian in Norway (Aarhus et al., 1986); significant since the Barre- cornutum assemblage (DA6): mian in Canada (Williams et al., 1974; Jenkins et al., 1974; Bujak and Will- the mid-lower Hauterivian iams, 1978), Greenland (Nöhr-Hansen, 1993), and northwestern Europe (Dav- ey, 1979; Duxbury, 1977, 1980, 2001; A Stratigraphic…, 1992) First occurrence of Banutiola- First occurrence in the lower Hauterivian of Norway (Aarhus et al., 1986); in dinium longicortum the Subpolar Urals since the upper Valanginian (Lebedeva and Nikitenko, 1998); in Greenland and northwestern Europe since the Hauterivian (Piasecki, 1979; Davey, 1979, 2001; A Stratigraphic…, 1992) First occurrence of Pseudo- In Greenland, P. pelliferum since the Berriasian (Piasecki, 1979); in England ceratium sp. and North Sea shelf, P. pelliferum since the mid-Ryazanian (Davey, 1979; Duxbury et al, 1999; A Stratigraphic…, 1992); in Boreal Canada and Norway, P. pelliferum since the Valanginian (Bujak and Williams, 1978); in the Mos- cow syneclise, P. pelliferum since the Hauterivian (Iosifova, 1996); diversity is characteristic of the Barremian in Canada (Bujak and Williams, 1978; Nöhr- Hansen, McIntyre, 1998), Greenland (Nöhr-Hansen, 1993), Barents Sea shelf (Smelror et al., 1998), and Moscow basin (Iosifova, 1996) First occurrence of Oligo- Oligosphaeridium totum since the Valanginian in Arctic Canada (Davies, sphaeridium aff. totum 1983) Note: Events observed at the same stratigraphic level in Siberia and different regions of north Europe and America are in bold.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 6 2007 606 PESTCHEVITSKAYA

Batioladinium varigranosum in the mid-Berriasian deva and Nikitenko, 1998). Species Aptea anaphrissa provides opportunity to correlate directly the base of appearing at the base of the Aptea anaphrissaÐBatioladin- the PareodinioideaeÐBatioladinium varigranosumÐ ium longicornutumÐOligosphaeridium aff. totum Zone Cassiculasphaeridia reticulata Zone with the lower marks the same level in the Subpolar Urals and Barents boundary of the Endoscrinium campanula Zone (Van Sea shelf (Fig. 5, Table 4). Of a considerable stratigraphic Helden, 1986; Table 1). Owing to occurrence of Cyclo- and correlation potential is the lower boundary of the nephelium cuculiform and Paragonyaulacysta ?borea- Aprobolocysta eilemaÐA. neistaÐOdontochitina sp. Zone lis in the Berriasian assemblage, these zones of Siberia (Fig. 5). This level is marked by essential changes in taxo- can be correlated with the concurrent Cyclonephelium nomic composition of dinocysts: it marks at once the first cuculliformeÐParagonyaulacysta ?borealis Zone of occurrences and extinctions of several species and Canada (Davies, 1983; Table 1). The base of the increased diversity of genera Muderongia, Aprobolocysta, Escharisphaeridia spp.ÐOligosphaeridium spp. Zone, corresponding to the upper boundary of the Paragon- and Batioladinium. Some of the palynological events are yaulacysta ?borealisÐDingodinium ?spinosum Zone in readily recognizable in northwestern Europe as well Siberia (Nikitenko et al., 2004; Table 1) is of a circum- (Table 4) that is important. Arctic geographic extent (Fig. 5, Table 4). Disappear- ance level of Dingodinium ?spinosum in Siberian sec- tions does not coincide with that boundary, being CONCLUSIONS recorded somewhat lower at the BerriasianÐValangin- ian boundary. It is of interest that in northwestern This study yielded new data on palynological char- Europe the youngest specimens of this species have acterization of Lower Cretaceous deposits in northern been found at the same level. Consequently, disappear- regions of West and Central Siberia. The results ance of Dingodinium ?spinosum can be regarded as obtained and published data, which have been ana- important criterion by defining the Berriasian upper lyzed, are used to define more precisely stratigraphic boundary. ranges of about 130 dinocyst species and to distinguish groups of stratigraphically important taxa, which The first occurrence of Oligosphaeridium complex appear at practically concurrent levels in several north- at the base of the Oligosphaeridium complexÐDingod- inium cerviculum Zone (Fig. 5) is an important indica- ern regions of Eurasia and America (Table 3). Levels of tion as well. In northern regions of Europe and Canada, their first or last occurrence can be regarded as impor- this event was practically isochronous, being recorded tant stratigraphic markers. Characteristic species of at the base of the Buchia keyserlingi bivalve zone (Dux- dinocysts, which become widespread in particular bury, 1977, 2001; Bujak and Williams, 1978; Piasecki, stratigraphic intervals and determine the “face” of 1979; Davey, 1979; McIntyre and Brideaux, 1980; respective assemblage, give an important information. Davies, 1983; Aarhus et al., 1986; A Stratigraphic…, Ten biostratigraphic subdivisions ranked as dinocyst 1992), i.e., at the same level as in Siberia. Oli- zones are distinguished in the BerriasianÐBarremian gosphaeridium complex, as a zonal index species, is deposits in northern regions of Siberia based on first mentioned only for the Tanyosphaeridium magneticum occurrences of stratigraphically important taxa, higher Zone in Canada and Zone C in England (Table 1) that or lower diversity degree of certain genera and families, provides the direct correlation of their lower boundaries and on compositional changes in groups of characteris- with the base of Siberian zone. tic dinocyst species. In majority, boundaries of these Stratigraphic extent of the Tanyosphaeridium mag- beds are of a great correlation potential and can be neticum dinocyst zone is defined as corresponding to regarded as reliable stratigraphic markers recognizable the lower Valanginian and lower part of the upper Val- not only in Siberia, but also in northern regions of anginian (?), although the precise position of its lower Europe and Canada. The dinocyst zones of the upper boundary has not been established (Davies, 1983). The Berriasian, Valanginian, and lower Hauterivian are con- performed stratigraphic analysis and correlation with fidently correlated with the Boreal standard zones the corresponding palynostratigraphic subdivision of (Zakharov et al., 1997) and can be used, when neces- Siberia, position of which is reliably defined in the sary, for subdivision and dating the deposits in Siberia. Boreal standard (Zakharov et al., 1997), suggest that The established biostratigraphic succession supple- this boundary is approximately at the base of the ments and specifies the dinocyst zonation substantiated Buchia keyserlingi Zone, i.e., at a somewhat higher in the Subpolar Urals (Lebedeva and Nikitenko, 1998) level than the Valanginian base. and extends upward the succession of dinocyst bio- The Hauterivian and lower Barremian correlation lev- zones characterizing the Upper JurassicÐlower Berria- els are recognizable in Siberia and Western Europe. Char- sian section of the Nordvik Peninsula (Nikitenko et al., acteristic components of the lower Hauterivian dinocyst 2004; Table 1). The suggested subdivision scheme of assemblages (presence of Hystrichodinium solare and the Lower Cretaceous based on dinocysts is included increased diversity and abundance of the genus Muderon- into the new regional stratigraphic chart for West Sibe- gia) are known besides from the Subpolar Urals (Lebe- ria (Regional …, 2007).

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ACKNOWLEDGMENTS 13. R. J. Davey, “A Summary of the Palynology of the Lower Hauterivian (Lower Cretaceous) from Speeton, East I am grateful to N.K. Lebedeva, V.A. Zakharov, England,” N. J. Geol. Paläontol. 219, 83Ð93 (2001). B.L. Nikitenko and G.N. Aleksandrova for construc- 14. E. H. Davies, “The Dinoflagellate Oppel-Zonation of the tive criticism and valuable comments to the manu- JurassicÐLower Cretaceous Sequence in the Sverdrup script. I thank also Yu.I. Bogomolov, V.A. Kazanen- Basin, Arctic Canada,” Bull. Geol. Survey Can., kov, V.A. Marinov, L.A. Glinskikh and O.O. Savchen- No. 359, 1Ð59 (1983). kova who donated samples for palynological analysis. 15. S. Duxbury, “A Palynostratigraphy of the Berriasian to The work was supported by the Russian Foundation for Barremian of the Speeton Clay of Speeton, England,” Basic Research, project nos. 06-05-64224 and 06-05- Palaeontographica. Ab. B 160, 17Ð67 (1977). 64291. 16. S. 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