Dinocyst Biostratigraphy of the Upper Cretaceous of Northern Siberia N

ISSN 0031-0301, Paleontological Journal, 2006, Vol. 40, Suppl. 5, pp. S604ÐS621. © Pleiades Publishing, Inc., 2006.

Dinocyst Biostratigraphy of the Upper Cretaceous of Northern Siberia N. K. Lebedeva Troﬁmuk Institute of Petroleum and Gas Geology, Siberian Division, Russian Academy of Sciences, pr. Koptyuga 3, Novosibirsk, 630090 Russia e-mail: [email protected] Received February 22, 2006

Abstract—A stratigraphic chart is developed of the Upper Cretaceous deposits of northern Siberia based on dinocysts. It covers the period from the Upper Cenomanian to the Maastrichtian, including 15 biostratigraphic units (beds with characteristic assemblages or local zones), and is correlated with the inoceram zonation. DOI: 10.1134/S0031030106110086 Key words: Dinocysts, Upper Cretaceous, Cenomanian, Turonian, Coniacian, Santonian, Campanian, Maas- trichtian, northern Siberia, biostratigraphy.

INTRODUCTION they are tested within closed territories. Thus, groups of fossil remains that in the least degree depend on In the Late Cretaceous, Western Siberia was a vast facial conditions are of particular importance. epicontinental basin. Upper Cretaceous deposits are Dinoflagellate cysts (Pls. 5, 6) are a relatively poorly covered almost everywhere by Cenozoic deposits. understood group of microfossils. The purpose of the Upper Cretaceous natural outcrops are found in the present investigation was to perform a detailed subdivi- Ust’-Yenisei and Khatanga regions, on the eastern sion of the Upper Cretaceous deposits of northern Sibe- slope of the Ural Mountains, and in the Polar Fore- ria based on the changes revealed in the taxonomic Urals. These sections are enriched with fossils and composition of dinocyst assemblages. serve as standards for parallel biostratigraphic zonation based on various faunal and floral groups. However, their facial composition may differ significantly from MATERIAL AND METHODS that of beds of inner regions of Western Siberia, where Dinocysts from the sections of Ust’-Yenisei and the major accumulations of oil and gas are situated. Khatanga regions, the Polar Fore-Urals, and boreholes Therefore, zonations that are developed on the basis of of Western Siberia and the Kara Sea shelf were studied reference sections can be used successfully only after (Fig. 1). The Upper Cretaceous reference section (Cen-

Explanation of Plate 5 Fig. 1. Chatangiella bondarenkoi (Vozzhennikova) Lentin et Williams, preparation TsSGM, no. 1212, Upper Santonian. Fig. 2. Chatangiella chetiensis (Vozzhennikova) Lentin et Williams, preparation TsSGM, no. 1227, Lower Santonian. Fig. 3. Chatangiella ditissima (McIntyre) Lentin et Williams, preparation TsSGM, no. 1192.4, Lower Campanian. Fig. 4. Isabelidinium rectangulatum Lebedeva, preparation TsSGM, no. 1212, Upper Santonian. Fig. 5. Chatangiella granulifera (Manum) Lentin et Williams, preparation TsSGM, no. 1219.1, Upper Santonian. Fig. 6. Chatangiella tanamaensis Lebedeva, preparation TsSGM, no. 1226, Lower Santonian. Fig. 7. Chatangiella spectabilis (Alberti) Lentin et Williams, preparation TsSGM, no. 1227.2, Lower Santonian. Fig. 8. Cerodinium diebelii (Alberti) Lentin et Williams, preparation TsSGM, no. 47.4, Coniacian. Fig. 9. Canningia macroreticulata Lebedeva, preparation TsSGM, no. 315.3, Upper Coniacian. Figs. 10 and 11. Cauveridinium membraniphorum (Cookson et Eisenack) Masure, preparation TsSGM, no. 380.3, Upper Cenomanian. Fig. 12. Heterosphaeridium difficile (Manum et Cookson) Ioannides, preparation TsSGM, no. 1228.2, Upper Coniacian. Fig. 13. Achomosphaera ramulifera (Deflandre) Evitt, preparation TsSGM, no. 1219.1, Upper Cantonian. Fig. 14. Chlonoviella agapica Lebedeva. TsSGM, no. 379.2, Lower Turonian. Fig. 15. Rhyptocorys veligera (Deflandre) Lejeune-Carpentier et Sarjeant, preparation TsSGM, no. 1219.2, Upper Santonian. Figs. 1Ð7, 12, 13, 15. Upper Cretaceous deposits on the Seida River (Polar Fore-Urals). Fig. 8. Upper Cretaceous deposits on the Tanama River (Ust’-Yenisei Region). Fig. 9. Upper Cretaceous deposits on the Yangoda River (Ust’-Yenisei Region). Figs. 10, 11, 14. Upper Cretaceous deposits on the Nizhnyaya Agapa River (Ust’-Yenisei Region). Magnification, ×500.

S604

DINOCYST BIOSTRATIGRAPHY OF THE UPPER CRETACEOUS OF NORTHERN SIBERIA S605

Plate 5

12 3 4

567 8

91011

15 12 13

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S606 LEBEDEVA

54 60 66 72 78 84 90 96 102 PECHORA SEA 8 Belyi Island Karskie Vorota Strait 68 Vaigach Island

Naryan-Mar Taimyr Peninsula 9 Yenisei Gulf Pyasina Pura 4 Pura Khatanga Yamal Peninsula 3 Khatanga Gydanskii Peninsula 72 Usa Kheta Kotui 5 Dudylta Vorkuta 2 7

12 of Ob 6 Usa 1 LakePyasina Pyasino Ob Dudinka 1. Nizhnyaya Agapa River Salekh Norilsk Gulf 2. Yangoda River 64 ard Yenisei 3. Vorontsovo village 11 4. Chaika River 0 100 200 km Taz 5. Tanama River Nadym Pur 6. Romanikha River Igarka 7. Maimecha River Kureika 8. Borehole Leningradskaya 1 9. Borehole Bovanenkovskaya 2 10. Borehole Yuzhno-Russkaya 113 11. Borehole Berezovskaya 23k 12. Seida River (Polar Fore-Urals)

Fig. 1. Geographical position of the sections studied. omanian–Maastrichtian) of the Ust’-Yenisei Region is of continental sedimentation. This fact is accounted for the section in northern Siberia where sequences of by the position of the Ust’-Yenisei Gulf in the marginal inoceram and dinocyst zones and local zones are most zone of the West Siberian Paleobasin, which was most complete. However, even this section contains numer- strongly affected by sea level ﬂuctuations. The study of ous gaps because either some constituents do not over- central and northern sections of Western Siberia was lap, or deposits are absent, or there were short periods supposed to ﬁll certain informational gaps.

Explanation of Plate 6 Figs. 1 and 2. Fromea chytra (Drugg) Stover et Evitt, preparation TsSGM, no. 1192.1, Lower Campanian, ×1250. Fig. 3. Fromea chytra (Drugg) Stover et Evitt, preparation TsSGM, no. 1192.2, ×1250. Fig. 4. Oligosphaeridium pulcherrimum (Deﬂandre et Cookson) Davey et Williams, preparation TsSGM, no. 245.4, Lower Coniacian. Figs. 5, 6. Dorocysta sp. A., preparation TsSGM, no. 235.6, Upper Turonian. Fig. 7. Chatangiella vnigrii (Vozzhennikova) Lentin et Williams, preparation TsSGM, no. 1192.4, Lower Campanian. Fig. 8. Eurydinium saxoniense Marshall et Batten, preparation TsSGM, no. 380.1.4, Upper Campanian. Fig. 9. Geiselodinium cenomanicum Lebedeva, preparation TsSGM, no. 362.5, Upper Cenomanian. Fig. 10. Alterbidinium “daveyi” (Stover et Evitt) Lentin et Williams, preparation TsSGM, no. 362.2, Upper Cenomanian. Fig. 11. Pierceites pentagonus (May) Habib et Drugg, preparation TsSGM, no. 367.4, Upper Cenomanian. Fig. 12. Spinidinium echinoideum (Cookson et Eisenack) Lentin et Williams, preparation TsSGM, no. 1228.2, Upper Coniacian. Fig. 13. Spinidinium uncinatum May, preparation TsSGM, no. 1209.3, Upper Santonian. Fig. 14. Chlamydophorella nyei Cookson et Eisenack, preparation TsSGM, no. 364.4, Upper Cenomanian. Fig. 15. Laciniadinium rhombiforme (Vozzhennikova) Lentin et Williams, preparation TsSGM, no. 1202.1, Lower Campanian. Fig. 16. Trithyrodinium sp. A, preparation TsSGM, no. 1228.2, Upper Coniacian. Fig. 17. Isabelidinium microarmum (McIntyre) Lentin et Williams, preparation TsSGM, no. 16.8, Campanian. Fig. 18. Chatangiella spinata Lebedeva, preparation TsSGM, no. 26.3, Campanian. Fig. 19. Chatangiella manumii (Vozzhennikova) Lentin et Williams, preparation TsSGM, no. 1209.4, Upper Santonian. Fig. 20. Chatangiella cassidea Lebedeva, preparation TsSGM, no. 1227.2, Lower Santonian. Fig. 21. Laciniadinium arcticum (Manum et Cookson) Lentin et Williams, preparation TsSGM, no. 1194.1, Lower Campanian. Fig. 22. Spinidinium sverdrupianum (Manum) Lentin et Williams, preparation TsSGM, no. 218.2, Lower Coniacian. Fig. 23. Chatangiella serratula (Cookson et Eisenack) Lentin et Williams, preparation TsSGM, no. 1217.3, Upper Santonian. Fig. 24. Dorocysta litotes Davey, preparation TsSGM, no. 1228.1, Upper Coniacian. Fig. 25. Membranosphaera maastrichtica Samoilovitch, preparation TsSGM, no. 1230.1, Upper Coniacian. Figs. 1Ð3, 7, 12, 13, 15, 16, 19Ð21, 23Ð25. Upper Cretaceous deposits on the Seida River (Polar Fore-Urals). Figs. 4Ð6, 22. Upper Cretaceous deposits on the Yangoda River (Ust’-Yenisei Region). Figs. 8Ð11, 14. Upper Cretaceous deposits on the Nizhnyaya Agapa River (Ust’-Yenisei Region). Figs. 17, 18. Upper Cretaceous deposits on the Tanama River (Ust’-Yenisei Region). Magniﬁ- cation, is ×500.

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DINOCYST BIOSTRATIGRAPHY OF THE UPPER CRETACEOUS OF NORTHERN SIBERIA S607

Plate 6

3 1 2 4

5678 9

10 11 12 13 14 15

16 20 17 18 19

24 25 21 22 23

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S608 LEBEDEVA

As a dinocyst-based biostratigraphical investigation transgression, marine deposits of the Mutino Formation of the Upper Cretaceous of Siberia was carried out for were accumulated. Layer-by-layer lithological, macro- the first time, the following procedure of zonation was faunal, and palynological characteristics of the section as used. For each section, the sediments were subdivided well as inoceram and dinocyst zonations were previously on the basis of successive changes in dinocyst assem- published (Khomentovskii et al., 1999). blages. Particular beds with dinocysts were revealed, representing comprehensively grounded biostratigraphic units. In reference sections, they were corre- Western Siberia lated with zones and local zones based on other groups Borehole Bovanenkovskaya 2 of fossil organisms. The boundaries of the biostrati- Borehole Bovanenkovskaya 2, which is situated in graphic units were defined predominantly on the basis the Yamal Peninsula, in the region of Kharasavei Penin- of the first and last appearances of particular dinocyst sula (Fig. 1), shows a continuous succession of the taxa; the epiboles of particular species and the list of Gan’kino and Tibeisale formations. I studied samples characteristic forms were used for the substantiation of from a depth of 503.0Ð408.8 m. Lebedeva (2006) pro- dinocyst local zones. Then, these particular zonations vided the palynological characteristics of the section. were correlated with each other and with the dated reference succession of beds with dinocysts of the Upper Cretaceous section of the Ust’-Yenisei Region. Borehole Yuzhno-Russkaya 113 Collection no. 1086 is kept at the Central Siberian Borehole Yuzhno-Russkaya 113 was drilled in near- Geological Museum (TsSGM) of the Joint Institute of roof region of the Yuzhno-Russkaya positive structure Geology, Geophysics, and Mineralogy of the Siberian of the Pur-Taz interfluve (Fig. 1). It outcrops the upper Division of the Russian Academy of Sciences, Novosi- Pokurskaya, Kuznetsovo, and the lower Berezovo for- birsk. mations. The study of microphytofossils allowed Lebe- deva et al. (2004) to recognize three palynological units CHARACTERISTICS and four beds with dinocyst, correlated with the Ust’- OF THE SECTIONS STUDIED Yenisei zonation. Ust’-Yenisei Region Within the Ust’-Yenisei Depression, the most com- Borehole Berezovskaya 23k plete sections of the Upper Cretaceous outcrop, with all Borehole Berozovskaya 23k is situated in north- six stages present: sections along the Nizhnyaya Agapa western peripheral part of Western Siberia, in the inter- (CenomanianÐMiddle Turonian), Chaika (Turonian), fluve of the Severnaya Sos’va, Khulga, and Kempazh Yangoda (Upper TuronianÐConiacian), and Tanama rivers (Fig. 1) and outcrops the upper Uvat and Kuz- rivers (SantonianÐMaastrichtian) and near the village netsovo formations. The palynological study of the of Vorontsovo (Upper Coniacian) (Fig. 1). The Upper borehole was accomplished by Denisyukova (1994), Cretaceous composite section is compiled on the basis who described from the interval of 219.0Ð173.0 m a of these five main sections, each is represented by doz- pollen-and-spore assemblage that is analogous to Turo- ens of outcrops in particular isolated regions. The geo- nian palynological assemblages from the Kuznetsovo logical age of exposures of Upper Cretaceous marine Formation of various regions of Western Siberia. Sam- deposits in the Ust’-Yenisei Region (from the Cenoma- ples from the same interval contain unidentifiable nian to Santonian) was substantiated by numerous finds microphytoplankton. Denisyukova also mentioned a of inocerams and relatively rare ammonites. The sec- rich assemblage of SantonianÐCampanian palynomor- tions were described, and their composite characteris- phs from the interval of 145.0Ð65.0 m of depth, in tics were given elsewhere (Stratigraphy of Upper Cre- which she determined several dinocyst taxa. Unfortu- taceous Deposits…, 1986, 1989; Zakharov and Kho- nately, this portion is absent from our borehole mate- mentovskii, 1989; Zakharov et al., 1989, 1991, 1998, rial. All the samples studied contained diverse assem- 2003). The stratigraphic zonation of the Upper Creta- blages of microphytofossils: spores and pollen grains ceous deposits of the Ust’-Yenisei Region based on of higher plants, dinoflagellate cysts, acritarchs, and dinocysts, spores, and pollen grains is correlated with prasinophytes. The successive change of dinocyst the inoceram chart provided by Ilyina et al. (1994) and assemblages made it possible to reveal the following Zakharov et al. (1997, 2002). biostratigraphic units (local zones) (Fig. 2).

Khatanga Region Beds with Rhiptocorys veligeraÐOligosphaeridium Within the Khatanga Depression, natural outcrops poculum show the most complete and paleontologically full sec- Characteristic assemblage. Chlonoviella agapica, tion of the Mesozoic. The Upper Cretaceous deposits Rhiptocorys veligera, Microdinium spp. (M. ornatum, along the Kheta River are mostly of the continental and M. glabrum, M. setosum, and M. distinctum), Chlamy- lagoonal origin. Only during the SantonianÐCampanian dophorella discreta, C. nyei, and Palaeohystrichophora

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 DINOCYST BIOSTRATIGRAPHY OF THE UPPER CRETACEOUS OF NORTHERN SIBERIA S609 . ramosus spp. ssp sp. granosus multibrevis granomembranaceus sp. A sp. sp. sp. sp. ssp. ssp. ssp. sp. Series Stage Substage Formation Beds with dinocysts Depth, m Lithology Samples Eurydinium saconiense Isabelidinium magnum Chatangiella Chatangiella tripartita Laciniadinium Oligosphaeridium poculum Downiesphaeridium aciculare Fromea chytra Cribroperidinium exilicristatum Trichdinium castaneum Surculosphaeridum longifucatum Circulodinium distinctum Cyclonephelium densebarbatum Cyclonephelium vannophorum Oligosphaeridium albertense Subtillisphaera pirnaesis Cauverdinium membraniphorum Eyrydinium Alterbidinium minus Alterbidinium acutulum Kallosphaeridium ? helbyi Impletosphaeridium Cometidinium obsurum ?Subtilisphaera hyalina Membranosphaera maastrichtica Oligosphaeridium comples Palaeotetradinium silicorum Spiniferites Spinferites ramosus Kallosphaeridum ?ringnesiorum Kallosphaeridum ?circulare Chlonoviella agapica Palaeohystrich. infusorioides Rhiptocorys veligera Chlamydophorella nyei Chlamydophorella discreta Microdinium ornatum Trithyrodinium suspectum Alterbidinium "daveyi" Odontochitina operculata Glyphanodinium facetum Pterodinium cingulatum Dorocysta S. ramosus Cassiculasphaeridia reticulata Spindinium Kiokansium polypes Florentinia buspina Florentinia ferox Exochosphaeridium Heterosphaeridium difficile S. ramosus S. ramosus Ellipsodinium rugulosum Elytrocysta circulata Chatangiella spectabilis Chatangiella victorinsis Chatangiella bondarenkoi Achomosphaera reticulata Spinferites scabrosus Achomosphaera crassipellis Isabelidinium cretaceum Wallodinium lunum 91 155 90 Upper 160 89

88 165 Heterosphaeridium diffcile Chalangoella spectabilis- 87 170 86 85 84

hyalina 175 83 Subtilisphaera

180 82 - 81 Turonian 185

190 80 Upper Cretaceous 79 dinocyst percentage: Middle Kuznetsovo Chlamydophorlla nyei 195 78 clays 77 200 76 - 75 aleuritic clays 74 205 73 72 sands 210 71 70 69 Designations: Rhiptocorys veligera 215 68 Oligosphaeridium poculum Chatangiella tripartita 67 0–5% 66 5–10% 220 65 > 10% U Uvat Ceno- manian

Fig. 2. Stratigraphic range of dinocysts in the Upper Cretaceous section of borehole Berezovskaya 23k. Designations: (Palaeohys- trich.) Palaeohystrichophor; (S.) Spiniferites. infusorioides are dominants. Eurydinium saxoniense, Lower boundary. Chatangiella tripartita increases Alterbidinium “daveyi,” and Trithyrodinium suspectum in number; and Eurydinium saxoniense, Oligosphaerid- play a signiﬁcant role. Pterodinium cingulatum, Cyclo- ium albertense, O. poculum, Cauveridinium membra- nephelium vannophorum, Circulodinium densebarbatum, niphorum, and some other taxa disappear. Cribroperidinium exilicristatum, Odontochitina opercu- Locality. Borehole Berezovskaya 23k, 197Ð174 m lata, Oligosphaeridium albertense, O. poculum, and Cha- of depth, sample nos. 197Ð174. tangiella tripartita are accompanying elements. Locality. Borehole Berezovskaya 23k, 220Ð197 m Beds with Subtiliasphaera hyalina of depth, sample nos. 66Ð77. Characteristic assemblage. Impletosphaeridium sp. is a dominant. Subtilisphaera hyalina is a characteristic member. Cometodinium obscurum, Coronifera stri- Beds with Chlamydophorella nyeiÐChatangiella olata, Surculosphaeridium longifurcatum, Chatang- tripartita iella sp., Laciniadinium arcticum, Palaeohystrichophora Characteristic assemblage. Chlamydophorella nyei infusorioides, Trithyrodinium sp., Microdinium sp., prevails. Chatangiella tripartita is a characteristic ele- Subtilisphaera pirnaensis, Membranosphaera maas- ment of the assemblage. Chlonoviella agapica, trichtica, and diverse Spiniferites are present. Microdinium ornatum, Rhiptocorys veligera, Palaeo- Lower boundary is marked by the appearance of hystrichophora infusorioides, and Chlamydophorella Subtilisphaera hyalina and some other taxa. discreta are accompanying elements. Alterbidinium Locality. Borehole Berezovskaya 23k, 178Ð164.6 m acutulum and A. minus appear. of depth, sample nos. 83Ð87.

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 S610 LEBEDEVA

Ust’-Yenisei section Inoceram zones (Khomentovskii, 1998) Series Stage Substage Formation Beds with dinocysts Lithology Borehole Yuzhno-Russkaya 113 Borehole Berezovskaya 23k Lower Lithology Beds with dinocysts Formation subinvolutus Coniacian Volviceramus Spinidinium

Spinidinium spp. spp. Spinidinium Berezovo - Depth, m Formation Substage Stage Lithology Beds with dinocysts

Upper 155 Ch. bondaren-

koi Upper Ch. serratula, Beds with Ch. bondarenkoi 160 Chatangiella serratula

H. difficile Nasonovo 165

Ch. biapertura, Ch. spectabilis, Ch. spectabilis-Heterosph. difficile 170 Beds with P P Ch. tanamaensis H. difficile P E. saxoniense Kuznetsovo In. (In.) lamarcki (s.l.) Turonian 175 Chatangiella Olig. pul- Ch. bondarekoi P

Upper Cretaceous P 180 - ? In. (In.) lamarckii (s.s.) Volviceramus inaequivalvis Ch. vic

Middle spp. 185 Chatangiella C. membraniphorum E. saxoniense - 190 Middle

- Chatangiella spp. E. saxoniense Kuznetsovo poculum veligera Turonian Rhiptocorys

Oligosphaeric. 195 In. (In.) cf. cuvieri G. cenomanucum 200 P Chlonoviella agapica toriensis spectabilis-cherrimum Pierceites pentagonus sverdrupianum Chlamydophorella nyei labiatus

Lower 205 P In. (Mytiloides) Amphidiadema sp. A P

. 210 . X. blastema

Dorozhkovo P L. siphoniphorum

Eurydin 215 Rhiptocorys veligera- Chlamydophorella nyei- Subtilisphaera Chat. spectabilis- saxonien Oligosphaeridium poculum Chatangiella tripartita hyalina Hetersp. difficle . .

In. (In.) pictus 220 Pokurskaya Upper U Geiselod cenoman Uvat Ceno manian Cenomanian Dolganskaya

P phosphate concretions plant macroremains appearance siliceous P disappearance deposits

leptochlorite biostratigraphic correlation presence

calcic concretions geological correlation no observations

Fig. 3. Correlation of boreholes Yuzhno-Russkaya 113 and Berezovskaya 23k and the Upper Cretaceous reference section of the Ust’-Yenisei Region. Designations: (Berez.) Berezovo; (U) Upper; (Ch.) Chatangiella; (Olig., Oligosphaerid.) Oligosphaeridium, (Eurydin. saxonien., E. saxoniense) Eurydinium saxoniense; (Geiselod. cenoman., G. cenomanicum) Geiselodinium cenomanicum; (In.) Inoceramus; (L. siphoniphorum) Litosphaeridium siphoniphorum; (X. blastema) Xenascus blastema; (H. difficile, Heterosph. difficile) Heterosphaeridium difficile; (C. membraniphorum) Cauveridinium membraniphorum; for other designations, see Fig. 2.

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 DINOCYST BIOSTRATIGRAPHY OF THE UPPER CRETACEOUS OF NORTHERN SIBERIA S611 sp. sp. sp. sp. sp. sp. sp. sp. sp. A sp. Series Stage Substage Formation Dinocyst assemblages Depth, m Lithology Sample Kallospharidium ?ringnesiorum Kallosphaeridium ?helbyi Alterbidinium “daveyi” Subtilisphaera Subtilisphaera inafecta Pterodinium cingulatum Geiselodinium cenomanicum Ovoidinium Ginginodinium evittii Xenascus Alterbidinium minus Apteodinium maculatum Glyphanodinium facetum Muderongia tetracantha Chlamydophorella discreta Chlamydophorella nyel Alterbidnium acutulum Trithyrodnium suspectum Trithyrodinium rhomboideum Subtilisphaera prinaensis Lotosphaeridum siphoniphorum Wallodinium luna Isabelidinium magnum Eurydinium saconiese Circulodinium distinctum Downiespharidium aciculare Oligosphaeridium complex Odontochitina operculata Kiokansium polypes Chatangiella Microdinium ornatum Microdinium glabrum Spiniferites ramosus Dorocysta Fromea chytra Trichodinium castaneum Apteodinum Chlonoviella agapica Cyclonephelium vannophorum Palaeohystrichophora infusoricides Spindinum uncinatum Fromea laevigata Chatangiella vrigrii Laciniadinium Laciniadinum rhombiforme Exochosphaeridium bifidum Spindinium Isabelidinium Fromea amphora Chatangiella granulifera Laciniadinium arcticum Spinidnium echinoideum Oligosphaeridium Oligosphaeridium pulcherrimum Dorocysta litotes Cerodinium 22 aff. medcalfii 450 21 500 Gan’kino Maastrichtian 550

600

650 ? no core 700 samples 750

800 Upper Cretaceous 850

Upper Berezovo Subformation 20 900 19 spp.

spp.- 18 spp.- 950 17 16 Coniacian Subformation 1000 15 Spindinium Chatangiella Laciniadinium Lower Berezovo 14 2 1050 13 Middle sovo ? 1–5 6–12 Kuznet- Turonian 1 1100 sale anian Marre- Upper Cenom- 1150

Fig. 4. Stratigraphic ranges of dinocysts in the Upper Cretaceous section of borehole Leningradskaya 1. Designations: (1) assemblage with Eurydinium saxoniense Marshall et Batten; (2) assemblage with Dorocysta sp. A; (Lower Berez.) Lower Berezovo Sub- formation; (Kuz.) Kuznetsovo (Mid.) Middle; (Spiniferites ram.) Spiniferites ramosus; for other designations, see Figs. 2 and 3.

Beds with Chatangiella spectabilisÐ Chatangiella victoriensis from the Middle Turonian Heterosphaeridium difficile section on the Chaika River. Beds with Chatangiella spectabilisÐHeterosphaeridium difficile from borehole Characteristic assemblage. Spiniferites spp. pre- Berezovskaya 23k are reliably correlated with those of vails. Dorocysta sp. A, Heterosphaeridium difficile, borehole Yuzhno-Russkaya 113 and, correspondingly, Chatangiella spectabilis, C. victoriensis, C. bondaren- with beds with Chatangiella spectabilisÐOligosphaerid- koi, Ellipsoidinium rugulosum, Achomosphaera cras- ium pulcherrimum of the Ust’-Yenisei section (In. (In.) sipellis, Elytrocysta circulata, and others are typical. lamarckii and Volviceramus inaequalis zones, MiddleÐ Lower boundary is determined by the appearance Upper Turonian) (Fig. 3). Chatangiella bondarenkoi of Heterosphaeridium difficile, Florentinia buspina, appears in the upper portions of these beds. In general, F. ferox, and others and by the increased diversity of the association of Dorocysta sp. A, Chatangiella spect- members of Chatangiella. abilis, and C. bondarenkoi is typical of beds with Cha- Locality. Borehole Berezovskaya 23k, 164.6Ð149.3 m tangiella bondarenkoiÐPierceites pentagonus from the of depth, sample nos. 88Ð91. Yangoda River section (Volviceramus inaequalis Zone). A similar succession of dinocyst assemblages The taxonomic composition of beds with Rhiptoc- was found in borehole Yuzhno-Russkaya 113. orys veligeraÐOligosphaeridium poculum from borehole Berezovskaya 23k is similar to that of borehole Yuzhno-Russkaya 113, which is dated Middle Turonian KARA SEA SHELF (Fig. 3). The characteristic combination of Cyclo- nephelium vannophorum, Cauveridinium membra- Borehole Leningrandskaya 1 is situated on the Kara niphorum, Eurydinium sp., Alterbidinium “daveyi,” Sea shelf, 200 km northwest of the northern extremity Subtilisphaera pirnaensis, and Chatangiella tripartita of Belyi Island (Fig. 1) and exposes the Marresale, suggests a correlation between beds with Chlamy- Kuznetsovo, Berezovo, and Gan’kino formations. dophorella nyeiÐChatangiella tripartita and beds with Remains of microphytoplankton appear in sample 6

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 S612 LEBEDEVA ramosus granosus brevifucatus ssp. ssp. sp. sp. sp. medcalfii sp. . ssp. sp. A sp. aff. Series Stage Substage Formation Dinocyst assemblages Depth, m Lithology Sample Florentinia ferox Membranosphaera maastrichita Chatangiella ditissima Cerodinium Cerodinium diebelii Palaeoperidinium cretaceum Palaeocystodinium Thalassiphora pelagica Leberidocysta chlamydata Fromea fragilis Spinniferites ramosus Spinniferites ramosus Spiniferites multibrevis Achomosphaera crassipellis Florentinia mantelli Chatangiella bondarenkoi Chatangiella serratula Chatangiella tanamaensis Chatangiella chetiensis Chatangiella spectabilis Chatangiella ?madura Palaeoperidinium pyrophorum Dinogymnium Dinogymnium kazachstanicum Dinogymnium sibricum Dinogymnium denticulatum Florentinia laciniata Hystrichosphaeridium tubiferum Trithyrodinium Dapsilidinium laminaspinosum Exochosphaeridium phragmites Hystrichosphaeridium salpinogophorum Odontochitina costata Chatangiella victoriensis Chatangiella triparita Chatangiella biapertura Cracpedodinium Heterosphaeridium difficile Senoniasphaera rotundata Cribroperidinum wilsonii Prolixosphaeridium Achomosphaera Spiniferites ram Cerodinium 22 aff. medcalfii 450 21

500 Gan’kino Maastrichtian 550

600

650 ? no core 700 samples 750

800 Upper Cretaceous

Upper Berezovo Subformation 850 20 900 19

spp. 18 spp.-

spp.- 17 950 16 Coniacian Subformation

Lower Berezovo 1000 Spindinium Chatangiella Laciniadinium 15 14 2 1050 13 Middle sovo Kuznet- –21–5 6–12

Turonian ? 1 1100 sale anian Upper Marre-

Cenom- 1150

Fig. 4. (Contd.)

(Fig. 4). As the samples were collected from narrow sp., Microdinium glabrum, Microdinium ornatum, Dor- disconnected intervals, it is impossible to establish ocysta sp. A, Trichodinium castanea, Cyclonephelium dinocyst zones. Therefore, characteristics of the vannophorum, and others appear for the ﬁrst time. dinocyst assemblages given below describe one or several palynospectra. Assemblage of Spinidinium spp.ÐChatangiella spp.ÐLaciniadinium spp. (Lower Berezovo Subforma- Assemblage of Eurydinium saxoniense (Mar- tion, 1010Ð900 m of depth, sample nos. 14Ð20). Dom- resale Formation, 1107.3Ð1099.25 m of depth, sample inant is Trithyrodinium suspectum. Subdominants are nos. 6Ð12). The following taxa are found: Alterbidin- Chatangiella spp. and Exochosphaeridium biﬁdum. ium “daveyi,” A. minus, A. acutulum, Subtilisphaera Spinidinium spp., Chatangiella vnigrii, C. granulifera, sp., S. pirnaensis, Pterodininium cingulatum, Geiselo- C. bondarenkoi, C. serratula, C. tanamaensis, C. che- dinium cenomanicum, Ginginodinium evittii, Xenascus tiensis, C. spectabilis, C. madura, C. biapertura, C. tri- sp., Apteodinium maculatum, Chlamydophorella dis- partita, C. victoriensis, Laciniadinium sp., L. rhombi- creta, C. nyei, Trithyrodinium rhomboideum, T. suspec- forme, L. arcticum, Oligosphaeridium pulcherrimum, tum, Litosphaeridium siphoniphorum, Isabelidinium Dorocysta litotes, Spiniferites ramosus ssp. granosus, magnum, Euryidinium saxoniense, Oligosphaeridium S. ramosus ssp. ramosus, S. multibrevis, Achomo- complex, and others. sphaera crassipellis, Florentinia ferox, F. mantelii, Assemblage of Dorocysta sp. A (Kuznetsovo For- F. laciniata, Dinogymnium spp., Hystrichosphaeridium mation, 1050 m of depth, sample no. 13). Some taxa tubiferum, Dapsilidinium laminaspinosum, Exochos- persist from the interval described below. Chatangiella phaeridium phragmites, Hystrichosphaeridium salpin-

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 DINOCYST BIOSTRATIGRAPHY OF THE UPPER CRETACEOUS OF NORTHERN SIBERIA S613 gophorum, Palaeoperidinium pyrophorum, Odonto- tures of the assemblage from beds with Chlamy- chitina costata, Heterosphaeridium difficile, Senonias- dophorella nyeiÐChlonoviella agapica (dominated by phaera rotundata, and other taxa are present. Chlamydophorella nyei and Chlonoviella agapica and Assemblage of Cerodinium aff. medcalfii (Gan’- including Eurydinium saxoniense, Litosphaeridium sp., kino Formation, 460Ð420 m of depth, sample nos. 21 Isabelidinium magnum, and Cauveridinium membra- and 22). Chatangiella ditissima, Cerodinium diebelii, niphorum) with the appearance of isolated Chatang- C. aff. medcalfii, Palaeoperidinium cretaceum, Palae- iella. Members of this genus become more numerous ocystodinium sp., Thalassiphora pelagica, and others and diverse upward in the section. The data on appear- appear. ance and disappearance of certain taxa in the succession of dinocyst assemblages of the Ust’-Yenisei section and above-mentioned boreholes suggest to place POLAR FORE-URALS the beds with this assemblage between beds with During the field trips of 1999, researchers of the Chlamydophorella nyeiÐChlonoviella agapica and Institute of Petroleum and Gas Geology of the Siberian with Chatangiella victoriensis (Fig. 5). Beds with Cha- Division of the Russian Academy of Sciences studied tangiella victoriensis is correlated with the beds with natural outcrops of the ConiacianÐCampanian age Chlamydophorella nyeiÐChatangiella tripartita and with along the Seida and Usa rivers (Fig. 1). Detailed Subtilisphaera hyalina of borehole Berezovskaya 23k on palynological and micropaleontological analyses of the the basis of co-occurrence of Cyclonephelium vanno- section were accomplished; macrofaunal remains were phorum, Eurydinium sp., Alterbidinium “daveyi,” Sub- also collected. Marinov et al. (2002) and Lebedeva tilisphaera pirnaensis, and Chatangiella tripartita. (2005) published results of studies of belemnites, Beds with Chatangiella spectabilisÐOligosphaeridium bivalves, foraminifers, and dinocysts. pulcherrimum (Ust’-Yenisei Region) were also recorded in boreholes Yuzhno-Russkaya 113 and Berezovskaya 23k. All the three assemblages are characterized by the CORRELATION OF THE SECTIONS STUDIED first appearance of Chatangiella spectabilis, C. tan- AND DINOCYST ZONATION OF THE UPPER amaensis, and C. biapertura and the presence of Doro- CRETACEOUS OF NORTHERN SIBERIA cysta sp. A. Dinocyst assemblages from these boreholes The correlation of all the sections studied allowed contain more diverse chorate dinocysts, including taxa the author to evaluate the content of some dinocyst bio- that are important in terms of stratigraphy, such as Sur- stratigraphic units, which were established in the refer- culosphaeridium longifurcatum and Heterosphaerid- ence Ust’-Yenisei section, to supplement them with ium difficile. The appearance of the latter species is reg- missing units and, hence, to reconstruct the most com- istered in the Upper Turonian in many regions of the plete succession of beds with dinocyst, which is pro- Northern Hemisphere (Williams et al., 1993). Oli- posed here as a standard dinocyst zonation of the Upper gosphaeridium pulcherrimum occurs in borehole sections Cretaceous of northern Siberia (Fig. 5). as isolated specimens, therefore, this stratigraphic unit is named beds with Chatangiella spectabilisÐHet- The earliest unit is beds with Geiselodinium cen- erosphaeridium difficile in the standard dinocyst zonation. omanicum of the Upper Cenomanian, which are only recorded in the Ust’-Yenisei Region. Beds with Eury- Analogues of beds with Spinidinium sverdrupianum dinium saxoniense are observed in borehole Leningrad- were recorded in boreholes Yuzhno-Russkaya 113 and skaya 1. The assemblages are similar in the presence of Leningradskaya 1. Early Coniacian assemblages are Eurydinium saxoniense, Geiselodinium cenomanicum, characterized by the increased number and diversity of Litosphaeridium siphoniphorum, Pterodinium cingula- Spinidinium and Chatangiella. tum, Ginginodinium evittii, Xenascus sp., and Isabeli- Beds with Canningia macroreticulata were found in dinium magnum. Beds with Chlamydophorella nyeiÐ the Ust’-Yenisei Region, the Polar Fore-Urals and Cir- Chlonoviella agapica are only found in the Ust’- cumpolar Trans-Urals (Beizel’ et al., 1996; Chlonova, Yenisei Region. On the Chaika River, the section is 1996). Canningia macroreticulata is a supposed vicar- continued by continental deposits, which are overlaid ious species of Canningia reticulata, which is a charac- by marine deposits. The stratigraphic scope of the gap teristic species of the Coniacian of northwestern is apparently rather short, since the succession of inoc- Europe. The assemblage shows a combination of Can- eram zones is not broken; however, boundary deposits ningia macroreticulata, Dorocysta litotes, and Het- between the Inoceramus (I.) cuvieri and I. (I.) lamarcki erosphaeridium difficile. The last species is abundant in zones in the marginal portion of the West Siberian the ConiacianÐLower Santonian of the North Sea Basin are missing in the section. Beds with Chatang- (Costa and Davey, 1992). Beds with Chatangiella che- iella victoriensis show significant changes: characteris- tiensis, first found on the Tanama River (Ust’-Yenisei tic Cenomanian species disappear, and the stratigraphi- Region), are similar in their characteristic members to cally important genus Chatangiella becomes a constant the unit with the same name in the section of the Polar component of the assemblage. Boreholes Yuzhno- Fore-Urals (Lebedeva, 2005). The genus Chatangiella Russkaya 113 and Berezovskaya 23k contain a dominates mostly due to C. chetiensis, C. tanamaensis, dinocyst assemblage that combines characteristic fea- and C. cassidea.

PALEONTOLOGICAL JOURNAL Vol. 40 Suppl. 5 2006 S614 LEBEDEVA Substage Stage Beds with Ust’-Yenisei Region Borehole Bovanenkovskaya 2 dinocysts aff.

Cerodinium ?Upper aff.

medcalfi Maastrichtian

Achomosph Borehole Leningradskaya 1 ramulifera- Palaecyst. Achom. ramulifera medcalfi Stage Substage Beds and zones with inocerams Beds with dinocysts Thickness, m Stratigraphic column Locality Cerodinium diebelii- Cerodinium Cerod. golsowenze

aff. ?Lower Ch. ditissima- Cerodinium

Ch. t. medc. Cerodinium O. cen.- diebellii-

diebellii 27.9 Fromea Maastr. chytra Seida River Chatangiella niiga inocerams absence of Ch.

niiga Chatan- . 34.1 giella Campanian

Campanian Isabelid. spp.- Ch. v niiga

Ch. verrucosa Tanama River S. pat. Alterbid spp.- . spp.- U S. echinoid S S.p. Chatangiella Isabelidi-

L 27.6 chetiensis nium spp.- Ch. chetien Santonian Chatang. verrucosa C. m. 29.1 Canningia Upper Alterbidin. macroreticulata Upper Inoceramus (H.) S. cardi- Vorontsovo spp.- Spinidnium

echinoideum Santonian 25.0 Coniacian Borehole Yuzhno- Lower Chatan- Lower Russkaya 113 I. (I.) schulginae giella I. (I.) jangodaensis chetiensis Lower Spinidnium . spp. S sverdrupianum 65.0 Yangoda River spp.-

pe pe oe Upper Lower Upper Canningia Upper Chatangiella macro- bondarenkoi- Borehole Berezovskaya 2 reticulata Coniacian Pierceites Ch. spectab.-H. difficile pentagonum Chatangiella H. difficile Ch. serratula spp. 52.0

Upper Chatangiella

spectabilis- spp.- nual H. d. Sub. Ch. s. Oligosphaer . pulcher- - rimum ? Spinidnium sverdrupia- Spinidnium Laciniadinium victo-

ngiela num riensis Chata- 36.0 Chaika River R. veligera- C. nyei O. poculum Ch. trip O. pocul. R. velig.- Middle cysta Turonian sp. A. Doro- Chatangiella bondarekoi- P. pentagorum Ch. spectabilis- ? Hetersophaer.

agapica difficile Turonian Chlamydo- Chlonoviella prorella nyei- 61.7

I. (M.) I. (I.) I. (I.) V. inaequi- Volviceramus Chatangiella Middle labiatus cuvieri lamarcki valvis subinvolutus russiensis ssoides Lower victoriensis Eurydinium E.. s. saxoniense 50 R. veligera- O. poculum Gelselodin.

I. (I.) pictus cenomanucum Chlamydo-

Upper phorella nyei- 43.0 Nizhnyaya Agapa River Cenomanian Chlonoviella 10 agapica Cenomanian Eurydinium saxoniese Geiselodin. cenomanucum

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Deposits of the SantonianÐCampanian boundary Stratigraphic position. The lower part of the Inoc- outcrop along the Tanama River (Ust’-Yenisei Region) eramus pictus Zone, Upper Cenomanian. and the Kheta River (Khatanga Region). The Santo- nianÐCampanian boundary in the Tanama section is very distinct both lithologically and paleontologically Beds with Eurydinium saxoniense (Stratigraphy of Upper Cretaceous Deposits…, 1986; Ilyina et al., 1994). This implies the presence of a strati- Characteristic assemblage. Ginginodinium evittii, graphic gap, the scope of which was estimated only by Odontochitina operculata, Xenascus blastema, and detailed paleontological studies of the Kheta River sec- ?Amphidiadema sp. A. dominate. Eurydinium saxo- tion (Khomentovskii et al., 1999). Similar changes in niense, Canningia rotundata, and Isabelidinium mag- the composition of dinocyst assemblages of these sec- num occur constantly. Microdinium distinctum appears tions and the Polar Fore-Urals made it possible to in the upper part. accomplish a correlation between these distant sections Boundaries. The lower boundary is determined by (Lebedeva, 2005). the appearance of Eurydinium saxoniense, ?Amphidia- Beds with Chatangiella ditissimaÐCerodinium dema sp. A, Microdinium ornatum, and Alterbidinium diebelii of the Tanama River are most similar to beds minus. with Operculodinium centrocarpumÐChatangiella tri- Typical section is situated on the Nizhnyaya Agapa partita (borehole Bovanenkovskaya 2). Beds with Cerodinium diebeliiÐAchomosphaera ramulifera, which River, Members 7Ð9; thickness, 14.5 m. continue the Maastrichtian succession of dinocyst bio- Occurrence. Ust’-Yenisei Region and the Kara Sea stratigraphic units, are recorded in borehole Bovanenk- shelf. ovskaya 2; and beds with Cerodinium aff. medcalﬁi are present in boreholes Bovanenkovskaya 2 and Lenin- Stratigraphical position. The upper part of the gradskaya 1. Inoceramus pictus Zone, Upper Cenomanian. Thus, the correlation of the sections studied recon- structed the most complete succession of biostrati- Beds with Chlamydophorella nyeiÐ graphic units (beds with particular dinocysts), which is Chlonoviella agapica possible to consider as a standard Upper Cretaceous zonation of northern Siberia until more data become Characteristic assemblage. Dominants are Chlamy- available (Fig. 5). dophorella nyei, Chlonoviella agapica, and Glyphano- dinium facetum. Alterbidinium “daveyi,” Isabelidin- ium magnum, Microdinium glabrum, Cauveridinium STANDARD DINOCYST ZONATION membraniphorum, Rhiptocorys veligera, Eurydinium OF THE UPPER CRETACEOUS saxoniense, and Kallosphaeridium ?circulare are con- OF NORTHERN SIBERIA stantly present. Beds with Geiselodinium cenomanicum Boundaries. The lower boundary is determined by the appearance of Dorocysta sp. A, Microdinium gla- Characteristic assemblage. Geiselodinium cen- brum, and Cauveridinium membraniphorum and the dis- omanicum and Pervosphaeridium truncatum are domi- appearance of Litosphaeridium siphoniphorum, Geiselo- nants. Trithyrodinium rhomboideum, Trichodinium dinium cenomanicum, and ?Amphidiadema sp. A. castanea, Ovoidinium scabrosum, Litosphaeridium siphoniphorum, Ginginodinium sp., and Pterodinium Typical section is situated on the Nizhnyaya Agapa cingulatum occur constantly. Xenascus blastema, Pier- River, Members 10Ð15; thickness, 47 m. ceites pentagonus, Microdinium ?crinitum, and Cyclo- Occurrence. Ust’-Yenisei Region. nephelium vannophorum appear in the upper part. Stratigraphic position. The upper part of the Inoc- Typical section is situated on the Nizhnyaya Agapa eramus pictus Zone, Upper Cenomanian, Inoceramus River, Members 2Ð4; thickness, 13 m. (Mytiloides) labiatus Zone, Lower Turonian, Inocera- Occurrence. Ust’-Yenisei Region. mus (Inoceramus) cf. cuvieri, Upper Turonian.

Fig. 5. Correlation of the main sections and the standard succession of beds with dinocysts for the Upper Cretaceous of northern Siberia. Designations: (Maastr.) Maastrichtian; (U) Upper; (L) Lower; (Ch.) Chatangiella; (Isabelid.) Isabelidinium; (Alterbid.) Alter- bidinium; (S. echinoid.) Spinidinium echinoideum; (S. cardissoides) Sphenoceramus cardissoides; (I.) Inoceramus; (V.) Volvicera- mus; (M.) Mytiloceramus; (H.) Haenleinia; (Oligosphaer., O.) Oligosphaeridium; (Geiselodin.) Geiselodinium; (R. veligera, R. velig.) Rhiptocorys veligera; (O. pocul.) Oligosphaeridium poculum; (Sub. hyal.) Subtilisphaera hyalina; (Ch. s., Ch. spectab.) Cha- tangiella spectabilis, (H. d., H. difficile) Heterosphaeridium difficile, (S. spp.) Spinidinium spp.; (E.s.) Eurydinium saxoniense; (C. m.) Canningia macroreticulata; (Ch. chetien.) Chatangiella chetiensis; (Ch. v.) Chatangiella victoriensis; (Ch. t.) Chatangiella tripartita; (Cerod. aff. medcalfii) Cerodinium aff. medcalfii; (O. cen.) Operculodinium centrocarpum, and (Achom. Ramulifera) Acho- mosphaera ramulifera; for other designations, see Figs. 2, 3, and 4.

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Beds with Rhiptocorys veligeraÐOligosphaeridium Beds with Chatangiella bondarenkoiÐPierceites poculum pentagonus Characteristic assemblage. Chlonoviella agapica, Characteristic assemblage: includes Chatangiella Rhiptocorys veligera, Microdinium spp., Chlamy- bondarenkoi, C. serratula, C. granulifera, C. madura, dophorella discreta, and C. nyei dominate. Eurydinium C. spectabilis, Heterosphaeridium difﬁcile, Dorocysta saxoniense, Alterbidinium “daveyi,” and Trithyrodin- sp. A, Pierceites pentagonus, Subtilisphaera pirnaen- ium suspectum are common. Pterodinium cingulatum, sis, and Cyclonephelium vannophorum. Cyclonephelium vannophorum, Circulodinium densebarbatum, Oligosphaeridium albertense, O. poculum, Boundaries. The lower boundary is marked by the and Chatangiella tripartita are accompanying elements. appearance of Chatangiella bondarenkoi, C. serratula, and C. chetiensis. Boundaries. The lower boundary is determined by the ﬁrst appearance of Chatangiella tripartita and by Typical section is situated on the Yangoda River, the last appearance of Oligosphaeridium albertense Members 3Ð8 (partly); thickness, 37 m. and O. poculum. Occurrence. Ust’-Yenisei Region, borehole Yuzhno- Typical section is situated in the borehole Bere- Russkaya 113. zovskaya 23k, 220Ð197 m of depth. Stratigraphic position. A part of the Volviceramus Stratigraphic position. Presumably Middle Turonian. inaequivalvis Zone, Upper Turonian.

Beds with Chatangiella victoriensis Beds with Spinidinium sverdrupianum Characteristic assemblage includes Chatangiella Characteristic assemlblage includes Spinidinium victoriensis, Cauveridinium membraniphorum, Cyclo- sverdrupianum, S. ornatum, Magallanesium balmei, nephelium vannophorum, Kallosphaeridium ?ringnesi- Oligosphaeridium complex, Chatangiella serratula, orum, Subtilisphaera pirnaensis, Laciniadinium sp., C. vnigrii, C. chetiensis, C. granulifera, Pierceites pen- Eurydinium sp., and Chichaouadinium cf. vestitum. tagonus, Eisenackia sp., and Exochosphaeridium biﬁdum. Boundaries. The lower boundary is indicated by the appearance of Chatangiella victoriensis, and Chicha- Boundaries. The lower boundary is marked by the ouadinium cf. vestitum and the disappearance of Isabe- appearance of Spinidinium sverdrupianum, S. ornatum, lidinium magnum and Eurydinium saxoniense. Magallanesium balmei, and Chatangiella cassidea. Typical section is situated along the Chaika River, Typical section is situated on the Yangoda River, Members 1Ð2; thickness, 20 m. upper part of Members 8Ð19; thickness, 61 m. Occurrence. Ust’-Yenisei Region, borehole Bere- Occurrence. Ust’-Yenisei Region, western Siberia, zovskaya 23k. Kara Sea shelf. Stratigraphic position. The lower part of the Inoc- Stratigraphic position. The middle part of the eramus (Inoceramus) lamarki Zone, Upper Turonian. Volviceramus inaequivalvis Zone, Upper Turonian, Volviceramus subinvolutus Zone, and the beds with Inoc- Beds with Chatangiella spectabilisÐ eramus schulginaeÐI. jangodaensis, Lower Coniacian. Heterosphaeridium difﬁcile Characteristic assemblage includes Dorocysta sp. A, Beds with Canningia macroreticulata Cribroperidinium exilicristatum, Surculosphaeridium longifurcatum, Apteodinium maculatum, Cyclonephelium Characteristic assemblage includes Canningia vannophorum, Ginginodinium evittii, Chatangiella macroreticulata, Alterbidinium minus, Senoniasphaera spectabilis, C. biapertura, and Microdinium distinc- protrusa, Subtilisphaera pirnaensis, and Odontochitina tum. In the upper portion of this local zone, Oli- operculata. gosphaeridium pulcherrimum appears. Boundaries. The lower boundary is indicated by the Boundaries. The lower boundary is determined by appearance of Canningia macroreticulata and Senon- the appearance of Chatangiella spectabilis, C. tripar- iasphaera protrusa and by the disappearance of Pier- tita, C. vnigrii, C. granulifera, C. tanamaensis, and ceites pentagonus and Dorocysta sp. A. C. biapertura and the disappearance of Trithyrodinium Typical section is situated on the Yangoda River, rhomboideum and Cauveridinium membraniphorum. Members 21Ð25; thickness, 20.1 m, village of Voronts- Typical section is situated on the Chaika River, ovo, Members 1Ð8; thickness, 29.1 m. Members 3Ð7, Yangoda River, Members 1Ð2; thickness, 17 m. Occurrence. Ust’-Yenisei Region, Circumpolar Stratigraphic position. The upper part of the Inoc- Urals, Polar Fore-Urals. eramus (Inoceramus) lamarki Zone and the lower part of Stratigraphic position. Inoceramus russiensis the Volviceramus inaequivalvis Zone, Upper Turonian. Zone, Upper Coniacian.

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Beds with Chatangiella chetiensis Occurrence. Ust’-Yenisei and Khatanga regions, Characteristic assemblage. Dominants are Cha- the Polar Fore-Urals. tangiella chetiensis, C. tanamaensis, C. cassidea, C. sp. A; Stratigraphic position. The upper part of the Sphe- and Trithyrodinium suspectum. Spinidinium uncina- noceramus patootensiformis Zone, ?Campanian. tum, S. echinoideum, Chatangiella bondarenkoi, C. granulifera, C. verrucosa, C. madura Isabeli- , and Beds with Chatangiella niiga dinium rectangulatum are present. Boundaries. The lower boundary is determined by Characteristic assemblage. Laciniadinium arcti- the appearance of Chatangiella verrucosa, C. ditis- cum, L. rhombiforme, Chatangiella niiga, C. manumii, sima, and Isabelidinium rectangulatum and by the dis- and C. spinata are dominants. Dinogymnium spp., appearance of Canningia macroreticulata and others. Laciniadinium williamsii, Fibrocysta sp., Tanyosphaerid- ium sp., Prolixosphaeridium sp., Operculodinium cen- Typical section is situated on the Tanama River, trocarpum, Chatangiella madura, and Isabelidinium Members 1Ð2; thickness, 11.7 m. spp. are present. Occurrence. Ust’-Yenisei and Khatanga regions Boundaries. and the Polar Fore-Urals. The lower boundary is marked by the appearance of Chatangiella spinata, a sharply Stratigraphic position. Sphenoceramus cardis- increased number of spinate members of Chatangiela, soides Zone, Lower Santonian, lower part of the Sphe- and by the disappearance of Chatangiella verrucosa, noceramus patootensis Zone, Upper Santonian. C. vnigrii, C. spectabilis, C. granulifera, C. tripartita, Chlonoviella agapica, and Alterbidinium “daveyi.” Beds with Alterbidinium spp.ÐSpinidinium Typical section is situated on the Tanama River, echinoideum Members 6 and 7; thickness, 21.6 m; Kheta River, Characteristic assemblage. Alterbidinium spp., Members 6Ð9; thickness, 22 m. Spinidinium echinoideum, Trithyrodinium suspectum, Occurrence. Ust’-Yenisei and Khatanga regions and Fibrocysta sp. dominate. Alterbidinium “daveyi,” and the Polar Fore-Urals. A. acutulum, Chatangiella chetiensis, C. tanamaensis, Stratigraphic position. Campanian. C. madura, C. ditissima, Microdinium ornatum, M. kustanaicum, and Laciniadinium rhombiforme occur. Beds with Nerodinium diebeliiÐFromea chytra Boundaries. The lower boundary is marked by the appearance of Laciniadinium rhombiforme, disappear- Characteristic assemblage includes Cerodinium ance of Chatangiella cassidea and N. victoriensis, and diebelii, Fibrocysta axialis, Operculodinium centro- the decreasing number of Chatangiella. carpum, Chatangiella ditissima, Membranosphaera Typical section is situated on the Tanama River, maastrichtica, Laciniadinium arcticum, Alterbidinium Member 3; thickness, 15.7 m, Kheta River, upper part minus, A. acutulum, and Chlonoviella agapica. Mem- of Members 1Ð3; thickness, 11.3 m. bers of the genus Fromea (Fromea chytra, F. laevigata, and F. fragilis) are most numerous and most diverse. Occurrence. Ust’-Yenisei and Khatanga regions. Boundaries. The lower boundary is marked by the Stratigraphic position. The upper part of the Sphe- appearance of Nerodinium diebelii and Fibrocysta axi- noceramus patootensis Zone, a part of the Sphenocera- alis and decreasing diversity of Chatangiella. mus patootensiformis Zone, Upper Santonian. Typical section is situated on the Tanama River, Members 8Ð12; thickness, 22.7 m. Beds with Isabelidinium spp.ÐChatangiella Occurrence. Ust’-Yenisei Region, borehole Bov- verrucosa anenkovskaya 2. Characteristic assemblage. Trithyrodinium suspec- Stratigraphic position. Maastrichtian. tum, Chatangiella vnigrii, Isabelidinium amphiatum, I. belfastense, I. bakeri, I. nooksoniae, I. microarmum, and Laciniadinium rhombiforme dominate. Chatang- Beds with Achomosphaera ramuliferaÐ iella verrucosa, C. ditissima, C. niiga, C. micracantha, Palaeocystodinium golzowense C. manumii, and Laciniadinium arcticum are present. Characteristic assemblage includes Cerodinium Boundaries. The lower boundary is deﬁned by the diebelii and Achomosphaera ramulifera with scarce appearance of Chatangiella niiga, C. micracantha, Chatangiella granulifera, Isabelidinium sp., Glyphan- C. manumii, and Isabelidinium belfastense and the dis- odinium facetum, Rhyptocorys veligera, Palaeoperi- appearance of Rhyptocorys veligera and Chatangiella dinium pyrophorum, Spinidinium sp., Palaeocystodin- sp. A. ium golzowense, Deﬂandrea sp., and Areoligera sp. Typical section is situated on the Tanama River, Boundaries. The lower boundary is marked by the Members 4 and 5; thickness, 12.5 m; and the Kheta disappearance of Chatangiella tripartita and Chlo- River, Members 4 and 5; thickness, 23.1 m. noviella.

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Locality. Borehole Bovanenkovskaya 2, sample the presence of Placenticeras meeki (Boehm.). The nos. 74Ð87; thickness, 48 m. assemblage is dominated by Chatangiella manumii, Occurrence. Borehole Bovanenkovskaya 2. Spinidinium uncinatum, S. echinoideum, Alterbidinium “daveyi,” A. minus, and A. acutulum. Stratigraphic position. Maastrichtian. Thus, the Upper Cretaceous deposits are subdivided on the basis of dinocyst data in the reference sections of Beds with Cerodinium aff. medcalfii the Ust’-Yenisei and Khatanga regions and the Polar Characteristic assemblage includes Cerodinium Fore-Urals and in core samples from western Siberia aff. medcalfii, numerous Laciniadinium firmum, Glyph- and the Kara Sea shelf. For the first time, the correlation anodinium facetum, Fromea chytra, and Spiniferites of the sections studied provides a reconstruction of ramosus ssp. ramosus, and rare Laciniadinium william- complete succession of dinocyst assemblages and a sii, Palaeotetradinium silicorum, Palaeocystodinium standard dinocyst zonation for the Upper Cretaceous of golzowense, Wallodinium luna, and Gillinia hymeno- northern Siberia, with 15 biostratigraphic units (beds phora. with characteristic assemblages) from the Upper Cen- omanian to Maastrichtian, which is correlated to the Boundaries. The lower boundary is determined by inoceram zonation. the appearance of the index species and disappearance of Chatangiella. Locality. Borehole Bovanenkovskaya 2, sample LIST OF DINOCYST SPECIES AND GENERA nos. 88Ð95; visible thickness, 32 m. The nomenclature follows The Lentin and Williams Stratigraphic position. The middle Upper Maas- Index of Fossil Dinoflagellages (Fensome and Will- trichtian. iams, 2004). Asterisks mark the taxa the names of which are retained in the former variants, since their systematic position is questionable, and treated differ- CONCLUSIONS ently by different authors. The successful correlation of distant Upper Creta- Achomosphaera crassipellis (Deflandre et Cook- ceous deposits on the basis of dinocysts is complicated son) Stover et Evitt, 1978 by their extraordinary diversity, asynchronous appear- Achomosphaera ramulifera (Deflandre) Evitt, 1963 ance and disappearance of particular taxa in different Alterbidinium acutulum (Wilson) Lentin et Will- regions, and provincialism. The panboreal correlation iams, 1985 of dinocyst assemblages of northern Siberia, north- *Alterbidinium “daveyi” (Stover et Evitt) Lentin et western Europe, Arctic and East Canada, and Atlantic Williams, 1985 coast of the United States was accomplished (Ilyina et al., 1994; Zakharov et al., 2002; Lebedeva, 2005). Alterbidinium minus (Alberti) Lentin et Williams, Two correlative levels were revealed. The first is in the 1985 Cenomanian, distinguished by the occurrence of Lito- Apteodinium maculatum Eisenack et Cookson, 1960 sphaeridium siphoniphorum, while the second is in the Canningia macroreticulata Lebedeva in Ilyina et al., Middle Santonian, marked by the appearance of the 1994 characteristic species Spinidinium echinoideum. The Cauveridinium membraniphorum (Cookson et Late TuronianÐEarly Coniacian dinocyst assemblages Eisenack) Masure in Fauconnier and Masure, 2004 of the Ust’-Yenisei Region and eastern Canada are sim- Cerodinium diebelii (Alberti) Lentin et Williams, 1987 ilar in the presence of some species of Chatangiella and Florentinia ferox, Oligosphaeridium pulcherrimum, Cerodinium aff. medcalfii (Stover) Lentin et Will- Magallanesium balmei, Senoniasphaera protrusa, Sub- iams, 1987 tilisphaera pirnaensis, and others. The SantonianÐ Chatangiella biapertura (McIntyre) Lentin et Will- Maastrichtian assemblages of northern Siberia and iams, 1976 Arctic Canada are very comparable. On the basis of Chatangiella bondarenkoi (Vozzhennikova) Lentin dinocysts, three correlative levels of Upper Cretaceous et Williams, 1976 deposits have been recognized in the sections of north- Chatangiella cassidea Lebedeva, 1988 ern Siberia and New Jersey (Atlantic coast of the Chatangiella chetiensis (Vozzhennikova) Lentin et United States). The first level is in the Cenomanian, Williams, 1976 marked by the appearance of Trithyrodinium suspec- Chatangiella ditissima (McIntyre) Lentin et Will- tum; the second is in the Santonian, indicated by the iams, 1976 increased number of Chatangiella. The appearance of Chatangiella manumii and C. vnigrii is very character- Chatangiella granulifera (Manum) Lentin et Will- istic in the Campanian of the regions compared. iams, 1976 Vasil’eva (2005) revealed in the Kushmurun section Chatangiella madura Lentin et Williams, 1976 (northern Kazakhstan) the beds with Chatangiella Chatangiella manumii (Vozzhennikova) Lentin et manumii, which was dated Late Campanian based on Williams, 1976

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Chatangiella micracantha (Cookson et Eisenack) *Fromea laevigata (Drugg) Stover et Evitt, 1978 Lentin et Williams, 1976 Geiselodinium cenomanicum Lebedeva in Ilyina Chatangiella niiga Vozzhennikova, 1967 et al., 1994 Chatangiella serratula (Cookson et Eisenack) Len- Gillinia hymenophora Cookson et Eisenack, 1960 tin et Williams, 1976 Ginginodinium evittii Singh, 1983 Chatangiella spectabilis (Alberti) Lentin et Will- Glyphanodinium facetum Drugg, 1964 iams, 1976 Heterosphaeridium difficile (Manum et Cookson) Chatangiella spinata Lebedeva, 2000 Ioannides, 1986 Chatangiella tanamaensis Lebedeva, 1988 Hystrichosphaeridium salpingophorum Deflandre, Chatangiella tripartita (Cookson et Eisenack) Len- 1935 tin et Williams, 1976 Hystrichosphaeridium tubiferum (Ehrenberg) Chatangiella verrucosa (Manum) Lentin et Will- Deflandre, 1937 iams, 1976 Isabelidinium ?amphiatum (McIntyre) Lentin et Chatangiella victoriensis (Cookson et Manum) Williams, 1977 Lentin et Williams, 1976 Isabelidinium bakeri (Deflandre et Cookson) Lentin Chatangiella vnigrii (Vozzhennikova) Lentin et et Williams, 1977 Williams, 1976 Isabelidinium belfastense (Cookson et Eisenack) Chichaouadinium cf. vestitum (Brideaux) Bujak et Lentin et Williams, 1977 Davies, 1983 Isabelidinium cooksoniae (Alberti) Lentin and Wil- Chlamydophorella discreta Clarke et Verdier, 1967 liams, 1977 Chlamydophorella nyei Cookson et Eisenack, 1958 Isabelidinium magnum (Davey) Stover et Evitt, Chlonoviella agapica Lebedeva in Ilyina et al., 1994 1978 Circulodinium densebarbatum (Cookson et Eisenack) Isabelidinium microarmum (McIntyre) Lentin et Fauconnier in Fauconnier and Masure, 2004 Williams, 1977 Circulodinium distinctum (Deflandre et Cookson) Isabelidinium rectangulatum Lebedeva 2006 Jansonius, 1986 Kallosphaeridium ?circulare (Cookson et Eisenack) Cometodinium obscurum Deflandre et Courteville, Helby, 1987 1939 Kallosphaeridium ?ringnesiorum (Manum et Cook- Coronifera striolata (Deflandre) Stover et Evitt, 1978 son) Helby, 1987 Cribroperidinium exilicristatum (Davey) Stover et Evitt, 1978 Laciniadinium arcticum (Manum et Cookson) Len- tin et Williams, 1980 Cyclonephelium vannophorum Davey, 1969 Laciniadinium firmum (Harland) Morgan, 1977 Dapsilidinium laminaspinosum (Davey et Williams) Lentin et Williams, 1981 Laciniadinium rhombiforme (Vozzhennikova) Len- tin et Williams, 1990 Dinogymnium sibiricum (Vozzhennikova) Lentin et Williams, 1973 Laciniadinium williamsii Ioannides, 1986 Dorocysta litotes Davey, 1970 Litosphaeridium siphoniphorum (Cookson et Eisen- Ellipsoidinium rugulosum Clarke et Verdier, 1967 ack) Davey et Williams, 1966 Elytrocysta circulata (Clarke et Verdier) Stover et Magallanesium balmei (Cookson et Eisenack) Halby, 1987 Quattrocchio and Sarjeant, 2003 Eurydinium saxoniense Marshall et Batten, 1988 Membranosphaera maastrichtica Samoilovitch in Samoilovitch and Mtchedlishvili, 1961 Exochosphaeridium bifidum (Clarke et Verdier) Clarke et al., 1968 Microdinium ?crinitum Davey, 1969 Exochosphaeridium phragmites Davey et al., 1966 Microdinium distinctum Davey, 1969 Fibrocysta axialis (Eisenack) Stover et Evitt, 1978 Microdinium glabrum Cookson et Eisenack, 1974 Florentinia buspina (Davey et Verdier) Duxbury, 1980 Microdinium kustanaicum Vozzhennikova, 1967 Florentinia ferox (Deflandre) Duxbury, 1980 Microdinium ornatum Cookson et Eisenack, 1960 Florentinia laciniata Davey et Verdier, 1973 Microdinium setosum Sarjeant, 1966 Florentinia mantelii (Davey et Williams) Davey et Odontochitina costata Alberti, 1961 Verdier, 1973 Odontochitina operculata (Wetzel) Deflandre et *Fromea chytra (Drugg) Stover et Evitt, 1978 Cookson, 1955 *Fromea fragilis (Cookson et Eisenack) Stover et Oligosphaeridium albertense (Pocock) Davey et Davey, 1978 Williams, 1969

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Oligosphaeridium complex (White) Davey et Will- ACKNOWLEDGMENTS iams, 1969 I am grateful to G.N. Kartseva and A.B. Beizel’ for Oligosphaeridium poculum Jain, 1977 providing samples and material from boreholes Lenin- Oligosphaeridium pulcherrimum (Deflandre et gradskaya 1, Yuzhno-Russkaya 113, Berezovskaya 23k, Cookson) Davey et Williams, 1969 and Bovanenkovskaya 2. Operculodinium centrocarpum (Deflandre et Cook- The study was supported by the Russian Foundation son) Wall, 1967 for Basic Research, project nos. 06-05-64224 and Ovoidinium scabrosum (Cookson et Hughes) 06-05-64291. Davey, 1970 Palaeocystodinium golzowense Alberti, 1961 REFERENCES Palaeohystrichophora infusorioide Deflandre, 1935 1. A. L. Beizel’, N. K. Lebedeva, V. A. Marinov, et al., Palaeoperidinium cretaceum (Pocock) Lentin et “Parallel Development of Inocerams, Foraminifers, Williams, 1976 Dinocysts, and Palynomorphs in the Late Cretaceous of Subpolar Trans-Ural Region,” in Geodynamics and Evo- Palaeoperidinium pyrophorum (Ehrenberg) Sar- lution of Earth: Materials of Scientific Conference of the jeant, 1967 Russian Foundation for Basic Research (Sib. Otd. Ross. Palaeotetradinium silicorum Deflandre, 1936 Akad. Nauk, Novosibirsk, 1996), p. 196 [in Russian]. Pervosphaeridium truncatum (Davey) Below, 1982 2. A. F. Chlonova, “Upper Cretaceous Dinoflagellates: Zonation and Provincializm,” in Abstracts of 9th IPC Pierceites pentagonus (May) Habib et Drugg, 1987 (AASP, Houston, 1996), p. 23. Pterodininium cingulatum (Wetzel) Below, 1981 3. L. I. Costa and R. J. Davey, “Dinoflagellate Cysts of the Rhiptocorys veligera (Deflandre) Lejeune-Carpen- Cretaceous System,” in A Stratigraphic Index of tier et Sarjeant, 1983 Dinoflagellate Cysts, Ed. by A. J. McIntyrepowel (Chap- man and Hall, London, 1992), pp. 99Ð131. Senoniasphaera protrusa Clarke et Verdier, 1967 4. R. N. Denisyukova, “Assemblages of Microfossils from Senoniasphaera rotundata Clarke et Verdier, 1967 the Upper Cretaceous Deposits of the Northern Trans- Spinidinium echinoideum (Cookson et Eisenack) Ural Region,” in Palynological Criteria in Biostratigra- phy of Western Siberia (ZapSibNIGNI, Tyumen, 1994), Lentin and Williams, 1976 pp. 100Ð106. Spinidinium ornatum (May) Lentin et Williams, 5. R. A. Fensome and G. L. Williams, “The Lentin and Wil- 1981 liams Index of Fossil Dinoflagellages,” Contr. Ser., Spinidinium sverdrupianum (Manum) Lentin et No. 42, 1Ð909 (2004). Williams, 1973 6. V. I. Ilyina, I. A. Kul’kova, and N. K. Lebedeva, Micro- Spinidinium uncinatum May, 1980 phytofossils and Detailed Stratigraphy of the Marine Mesozoic and Cenozoic of Siberia (OIb’ed. Inst. Geol. *Spiniferites multibrevis (Davey et Williams) Geofiz. Mineral. Sib. Otd. Ross. Akad. Nauk, Novosi- Below, 1982 birsk, 1994) [in Russian]. Spiniferites ramosus (Ehrenberg) Mantell, 1854 7. O. V. Khomentovskii, V. A. Zakharov, N. K. Lebedeva, Spiniferites ramosus ssp. granosus (Davey et Will- and O. I. Vorobyeva, “The Santonian–Campanian iams) Lentin et Williams, 1977 Boundary in Northern Siberia,” Geol. Geofiz. 40 (4), 512Ð529 (1999). Spiniferites ramosus ssp. ramosus Ehrenberg, 1838 8. N. K. Lebedeva, “Biostratigraphy of tUpper Cretaceous Subtilisphaera hyalina Singh, 1983 Deposits in the Usa River Basin (Polar Fore-Urals) Subtilisphaera ?pirnaensis (Alberti) Jain et Mill- Based on Dinocysts,” Stratigr. Geol. Korrelyatsia. 13 (3), epied, 1973 114Ð131 (2005). 9. N. K. Lebedeva, “Palynological Characteristics of the Surculosphaeridium longifurcatum (Firtion) Davey Maastrichtian Deposits Based on Borehole Bovanenk- et al., 1966 ovskaya 2,” in Problems of Stratigraphy and Paleogeog- Thalassiphora pelagica (Eisenack) Eisenack et raphy of the Boreal Mesozoic: Materials of Scientific Gocht, 1960 Session Devoted to 95th Birthday of V.N. Saks (Sib. Otd. Poss. Akad. Nauk Branch Geo, Novosibirsk, 2006), Trichodinium castanea (Deflandre) Clarke et Ver- pp. 53Ð58 [in Russian]. dier, 1967 10. N. K. Lebedeva, S. E. Agalakov, and A. L. Beizel’, Trithyrodinium rhomboideum Singh, 1983 “Palynostratigraphy and Structure of the Upper Creta- Trithyrodinium suspectum (Manum et Cookson) ceous Section Based on Borehole Yuzhno-Russkaya 113 Davey, 1969 (Pur-Taz Interfluve, Western Siberia),” Geol. Geofiz. 45 (6Ð7: News of Paleontology and Stratigraphy), 191Ð207 Wallodinium luna (Cookson et Eisenack) Lentin et (2004). Williams, 1973 11. V. A. Marinov, V. A. Zakharov, D. P. Naidin, and Xenascus blastema (Davey) Stover et Halby, 1987 O. V. Yazikova, “Stratigraphy of the Upper Cretaceous

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of the Usa River Basin (Polar Fore-Urals),” Byull. Mosk. ence on the Topical Questions of Geology and Geogra- OÐva Ispyt. Prir., Otd. Geol. 77 (3), 26Ð40 (2002). phy of Siberia (Tomsk. Gos. Uni., Tomsk, 1998), 12. Stratigraphy of Upper Cretaceous of Deposits of North- pp. 210Ð215 [in Russian]. ern Siberia (Ust’-Yenisei Depression), Ed. by V. A. Za- 18. V. A. Zakharov, A. L. Beizel’, and V. P. Pokhialainen, kharov, Yu. N. Zanin, K. V. Zverev, et al. (Inst. Geol. “Discovery of the Marine Cenomanian in Northern Sibe- Geofiz. Sib. Otd. Akad. Nauk SSSR, Novosibirsk, 1986) ria,” Geol. Geofiz., No. 6, 10–13 (1989). [in Russian]. 19. V. A. Zakharov, Yu. I. Bogomolov, V. I. Ilyina, et al., 13. Stratigraphy of Upper Cretaceous of Deposits of North- “Boreal Zonal Stratotype and Biostratigraphy of the ern Siberia (Section on the Yangoda River), Ed. by Mesozoic of Siberia,” Geol. Geofiz. 38 (5), 99Ð1287 V. A. Zakharov, A. L. Beizel’, K. V. Zverev, et al. (Inst. (1997). Geol. Geofiz. Sib. Otd. Akad. Nauk SSSR, Novosibirsk, 1989) [in Russian]. 20. V. A. Zakharov and O. V. Khomentovskii, “New Data on 14. O. N. Vasil’eva, “Dinocysts of the Late Cretaceous in the Stratigraphy of the Marine Upper Cretaceous of the Kushmurum Section (Northern Kazakhstan),” in Palynol- Ust’-Yenisei Depression,” in Stage and Zonal Scales of ogy: Theory and Practice, Materials of the 9th All-Rus- the Boreal Mesozoic of the USSR (Nauka, Moscow, sia Palynological Conference (Paleontil. Inst. Ross. 1989), pp. 176Ð184 [in Russian]. Akad. Nauk, Moscow, 2005), pp. 40Ð41 [in Russian]. 21. V. A. Zakharov, N. K. Lebedeva, and O. V. Khomen- 15. G. L. Williams, L. E. Stover, and E. J. Kidson, “Mor- tovsky, “Upper Cretaceous Inoceramid and Dinoflagel- phology and Stratigraphic Ranges of Select Mesozoic- late Cysts Biostratigraphy of the Northern Siberia,” in Cenozoic Dinoflagelate Taxa in the Northern Hemi- Tethyan/Boreal Cretaceous Correlation: Mediterranean sphere,” Geol. Surv. Canada, Pap. 92-10, 1Ð137 (1993). and Boreal Cretaceous Paleobiogeographic Areas in 16. V. A. Zakharov, A. L. Beizel’, N. K. Lebedeva, and Central and Eastern Europe, Ed. by M. Jozef (VEDA O. V. Khomentovskii, “Evidence of Eustatic Variations Publ. House Slovak Acad. Sci., Bratislava, 2002), of the World Ocean in the Upper Cretaceous of Northern pp. 137Ð172. Siberia,” Geol. Geofiz. 8, 9Ð14 (1991). 22. V. A. Zakharov, N. K. Lebedeva, and V. A. Marinov, 17. V. A. Zakharov, A. L. Beizel’, N. K. Lebedeva, and “Biotic and Abiotic Events in the Late Cretaceous of the O. V. Khomentovskii, “New Data on the Stratigraphy of Arctic Biogeographical Region,” Geol. Geofiz. 44 (11), the Upper Cretaceous of Northern Siberia,” in Confer- 1093Ð1103 (2003).

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