Lower Cretaceous biostratigraphy of Northern Siberia: palynological units and their correlation significance

palynological units and their correlation significance

E.B. Pestchevitskaya *

Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia

Received 10 August 2006

Abstract

The Berriasian-Barremian biostratigraphy based on spores and pollen of terrestrial plants found in sections from northern Siberia shows asuccession of eight units. The ages of the units are proved by calibration against the Boreal zonal standard and their stratigraphic position iscontrolled by faunal and dinocyst records. The sections of the study are depth-stacked over one another, with partial overlap, and includeseveral isochronous levels marked by the same palynological features. The levels are defined by changes in the taxonomic composition ofspore-pollen assemblages found in the sections and recognized using published evidence from northern Siberia. Most of the identified boundariesof the palynostratigraphic units provide a good potential for northern Siberian regional correlation.

Keywords: Spore-pollen biostratigraphy; correlation; Berriasian-Barremian; West Siberia; East Siberia

Introduction

Updating the northern Siberian regional stratigraphy forpetroleum prospecting and geological mapping requires revi-sion of spore-pollen data from Mesozoic sections. Palynologi-cal scales constitute an essential component of regionalstratigraphic charts and are used commonly as age constraintsfor buried strata in West Siberia (Beizel et al., 2002; Kuz’minaet al., 2003; Nikitenko et al., 2002). Of special importance inthis respect is reliable dating of palynostratigraphic units andtheir calibration against macro- and microfossil zones. Thesuggested succession of biostratigraphic units is based onspore-and-pollen analysis of Lower Cretaceous sections innorthern Siberia (Fig. 1) of which many have received detailedfaunal records. The sections from the Nordvik Peninsula andthe eastern side of Anabar Bay are included into the Borealzonal standard (Zakharov et al., 1997), and the stratigraphicposition of Berriasian, Valanginian, and Hauterivian palyno-stratigraphic units is constrained by ammonite, belemnite,bivalve, and foraminifera records (Bogomolov et al., 1983;Golbert, 1981; Nikitenko et al., 2006; Zakharov et al., 1983).The control comes from foraminifers and ammonites inSevero-Vologochanskaya BH-18 (Nikitenko et al., 2004) and

Lower Valanginian ammonites, foraminifers, and bivalves inboreholes in the Pur-Taz interfluve (Zakharov et al., 1999).The stratigraphy of the identified units has been additionallychecked against dinocyst data (Pestchevitskaya, 2005a,b;2006).

* Corresponding author.E-mail address: [email protected] (E.B. Pestchevitskaya) Fig. 1. Location map of sections of this study.

Russian Geology and Geophysics 48 (2007) 941–959

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Lower Cretaceous biostratigraphy of Northern Siberia:

© 2007, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

1068-7971/$ - see front matter D 2007, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

004doi:10.1016/j.rgg.2007. 10.4

The palynostratigraphic units are described below with aspecial focus on their boundaries and on the taxonomy ofspore-pollen assemblages which have important implicationsfor stratigraphy and correlation. Besides the newly investigatedsections, the distribution of diagnostic taxa was studied usingpublished data from northern areas of West and CentralSiberia.

Lower Cretaceous spore-pollen stratigraphy of Northern Siberia: a synopsis

The sections of this study are located in the Frolovo,Ob’-Nadym, and Ust’-Yenisei regions, in the Pur-Taz inter-fluve, and in the Khatanga basin. Lower Cretaceous spore-pol-len assemblages were largely studied over most of the territorybut their stratigraphic extent remains too wide (to stage orsubstage). Kara-Murza (1954, 1958), in cooperation withNaumova, Yaroshenko, Morozova, and Pokrovskaya, collectedmost exhaustive data on Lower Cretaceous spore-pollenassemblages from the Anabar-Khatanga interfluve. They docu-mented the palynology of Valanginian, Hauterivian-Barre-mian, and Aptian sections, provided their first age estimatesfrom spore-and-pollen analysis, and suggested a correlationchart for spore-pollen assemblages of northern Siberia. Pavlov(1970) described three spore-pollen assemblages which werefound in Upper Jurassic and Lower Cretaceous sections in theNordvik Peninsula and were assigned Upper Volgian, Berri-asian, and Lower Valanginian ages, respectively. Bondarenko(1961) performed palynological analysis of Valanginian andHauterivian (?) sediments from the eastern side of Anabar Baybut failed to report descriptions of the spore-pollen assem-blages; she only noted that Lower Hauterivian (?) assemblagescontained abundant gymnosperm pollen and rarer Lygodiumspecies, characteristic of the Valanginian. Detailed descrip-tions of spore-pollen assemblages, with percentages of indextaxa, are available for the Berriasian, Valanginian, Hau-terivian, and Barremian from the Frolovo (Shirokova, 1973;Sologub, 1994), Ob’-Nadym (Bochkareva, 1969; Bogomyak-ova et al., 1970; Korzh, 1978), and Ust’-Yenisei (Kara-Murza,1960; Saks et al., 1963; Sheiko, 1970) regions. Pestchevitskaya(Pestchevitskaya, 1999, 2000, 2002; Nikitenko et al., 2004)suggested a more detailed stratigraphic subdivision of theLower Cretaceous using spore-and-pollen analysis. Berriasian-Valanginian spore-pollen assemblages were first described byLebedeva and Pestchevitskaya (Lebedeva and Pestchevitskaya,1998; Zakharov et al., 1999). The cited data were comparedwith the published palynological evidence from northern Westand Central Siberia to estimate the stratigraphic significanceof selected spore and pollen taxa and their percentages and tooutline their palynostratigraphic implications (Pestchevitskaya,2005a).

According to published evidence, stratigraphic units havebeen rarely distinguished on the basis of spore-pollen data.Russian stratigraphers most often use spore-pollen data asadditional characteristics, especially in the case of marinesediments whose subdivision commonly lies upon rapidly

evolving faunas. Until recently, spore-pollen assemblages weredescribed as something just like a “fill” in lithostratigraphicunits (formations, members, beds, or their parts) or inbiostratigraphic units identified according to other groups offossils. This approach, however, overlooks the levels ofchanges in the taxonomic composition of spore-pollen assem-blages which not necessarily coincide with the boundaries ofstratigraphic units defined by lithology and fauna.

In the traditional approach, descriptions of spore-pollenassemblages for stratigraphic reconstructions focused mainlyon percentages of common taxa, as it was made for thepalynology-based Lower Cretaceous stratigraphy of Siberia(Saks et al., 1981; Belousov et al., 1991). Extensive pa-lynological evidence was used to distinguish characteristicLower Cretaceous assemblages for certain provinces withsimilar sets of dominant, subdominant, and subsidiary taxa;the stratigraphic position of spore-pollen assemblages wasdetermined from changes in relative percentages of dominantspecies and in systematic composition of subsidiary species.Yet, most taxa are found continuously throughout the LowerCretaceous, and more so, sometimes occur in Jurassic orUpper Cretaceous strata. Furthermore, the reported spore-pol-len assemblages were often of a large stratigraphic range upto stage or substage.

Synthesis of published evidence was used in this study tocompare and systematize percentage data for coeval spore-pol-len assemblages from geographically dispersed Lower Creta-ceous sections in northern Siberia (Pestchevitskaya, 2005a).Quantitative taxa proportion, however, turned out to be anambiguous criterion for stratigraphy and correlation becausepercentages of many taxa in coeval assemblages can vary evenin neighbor areas. Qualitative changes of taxonomic compo-sition appear to be a more reliable diagnostic tool for detailedstratigraphic division.

Comprising a lot of inherited Jurassic taxa, the spore-pollenassemblages bear characteristic Lower Cretaceous species thatgradually become ever more diverse up the section. They arenamely Gleicheniaceae and Schizaeaceae and some Hepa-tiaceae. Few finds of Gleicheniaceae and Schizaeaceae (Glei-cheniidites senonicus Ross emend. Skarby, Plicifera decora(Chlonova) Bolchovitina, Anemia sp., Lygodiumsporites spp.,L. subsimplex (Bolchovitina) Bondarenko) were reported fromUpper Jurassic sections in West and Central Siberia (Bolk-hovitina, 1961; Denisyukova, 1984; Ilyina, 1985; Kara-Murza,1954, 1958). Gleicheniaceae and Schizaeaceae had their acmein the Early Cretaceous. In the Berriasian, Gleicheniaceae(Gleicheniidites, Plicifera) and granular spores of Schi-zaeaceae (Impardecispora, Concavissimisporites, Trilobo-sporites, and some species of Lygodium) increased in diversityand Aequitriradites genus of Hepatiaceae made their firstappearance. The Valanginian was the time of beginning bloomof striate Schizaeaceae (Cicatricosisporites, Plicatella, Ane-mia, Mohria), and the Hauterivian was marked by theinception of their new forms (Appendicisporites) and of someHepatiaceae (Coptospora, Rouseisporites, Coocksonites). Spi-nous Schizaeaceae (Pilosisporites, some species of Lygodium)

942 E.B. Pestchevitskaya / Russian Geology and Geophysics 48 (2007) 941–959

reached a great diversity in West Siberia but were quite rarein northern Central Siberia.

These palynologic trends were discovered long ago andused for stratigraphic subdivision but the available palynologi-cal literature failed to provide details of the distribution ofdifferent species. In her book about Schizaeaceae, Bolk-hovitina (1961) reported the stratigraphic extent of mostspecies in the family but she used too broad stratigraphicintervals of two or three stages, or even a series to date theirinceptions. Recent published evidence of Lower Cretaceouspalynology of northern Siberia allowed more rigorous ageconstraints of some species of Gleicheniaceae, Schizaeaceae,and Hepatiaceae and was used to distinguish groups of speciesthat made their first appearance at certain stratigraphic levels(Fig. 2). The list of those taxa was largely extended due todata on the distribution of stratigraphically significant speciesfrom sections of northern Siberia obtained in the reportedstudy. The new data provided a basis for palynostratigraphicsubdivision of the Lower Cretaceous.

Palynostratigraphic subdivision and comparativeanalysis of Berriasian-Barremian spore-pollenassemblages in Northern Siberia

Eight stratigraphic layers with spores and pollen of gym-nosperms were identified from the distribution of terrestrialpalynomorphs. See Figs. 3 and 4 for their general stratigraphy,palynology, and sediment lithology. Determining the totallateral extent of the layers was hampered in some sections bycoring and sampling gaps. Individual sections most oftenexposed the palynostratigraphic layers only partly, leavingunknown their full stratigraphic range. The best documentedwere the Lower Valanginian layers reaching hundreds ofmeters in thickness in central West Siberia (Pur-Taz interfluve,see Fig. 4), though being thin along the margins of the paleo-basin (Ust’-Yenisei region, Severo-Vologochanskaya BH-18).The Berriasian and Lower Valanginian palynostratigraphicunits of the Khatanga basin and the Hauterivian ones of theLatitudinal Ob region are composed of sediments with highestclay contents.

The boundaries of layers with spores and pollen ofgymnosperms were defined from the taxa that were strati-graphically significant components of coeval spore-pollenassemblages in northern Siberia and the species whoseinceptions at certain stratigraphic levels can be recognized indifferent areas (Fig. 5). Thus, many boundaries of thedistinguished units have regional stratigraphic utility.

Layers with SPA1 were identified in the Upper Berriasianand Lower Valanginian in the Nordvik Peninsula and inSevero-Vologochanskaya BH-18 (Fig. 4). The assemblage hasa transitional systematic composition with abundant Jurassictaxa coexisting with characteristic Cretaceous forms which arediagnostic for the stratigraphy and lower boundary of thelayers (Fig. 4). The assemblages characteristically contain lowabundances (but more than few specimens) of Cicatricosis-porites spp., Gleicheniidites spp., Trilobosporites spp., Lygodi-

umsporites spp. Spore-pollen assemblages with similar sys-tematic compositions were reported from Berriasian sectionsof the Subarctic Urals, the Khatanga basin, and the Lena-An-abar region: the spore-pollen compositions change above thebase of the Hectoroceras kochi Zone to include many UpperBerriasian and Lower Valanginian taxa (Figs. 2 and 6).However, it was impossible to identify this level in the studiedsections because the SPA1 layers occur in stratigraphicallyhigher Berriasian strata: above the base of Surites analogus inthe Nordvik Peninsula and above the base of Bojarkiamesezhnikowi in Severo-Vologochanskaya BH-18.

Note that the percentages of taxa vary in quite a broadrange over the territory of Siberia. Striate and granular sporesof Schizaeaceae are most often few or rare (to 3%) (Fedorovaet al., 1993; Golbert, 1981; Korzh, 1978) and reach relativelyhigh percentages (5–9%) only along the Boyarka and Mai-mecha Rivers (Pavlov, 1969). Gleicheniaceae spores are ashigh as 16% and diverse in the Berriasian of western WestSiberia and Transuralia (Korzh, 1978) and in the lowerBerriasian of the Khatanga basin (Golbert, 1981).

The taxonomic composition of spore-pollen assemblageschanges considerably at base of layers with SPA2 (Fig. 4).According to published evidence (Bolkhovitina, 1961), Ly-godium splendidum Kara-Mursa and Cicatricosisporites minu-taestriatus (Bolchovitina) Pocock are also present intransitional Berriasian-Lower Valanginian assemblages(Fig. 6). The most ancient occurrences of C. pseudoauriferus(Bolchovitina) Voronova are found in Neocomian strata in theeastern Caucasia region. The level has been recognized mostlyin the sections of this study (Fig. 6) whereas the availablepublications (Fradkina 1967; Kara-Murza, 1958; Korotkevich,1962; Pavlov, 1970; Popovicheva, 1984; Strepetilova, 1984;Strepetilova et al., 1982) refer to a large time span from theBerriasian to the Lower Valanginian, inclusive. As it wasnoted by many palynologists, the diversity and abundance ofSchizaeaceae increase in the Lower Valanginian, with theirpercentages most often about 3–5% on average thoughoccasionally up to 10–12% in northern West Siberia and inthe Vilyui basin (Fradkina 1967; Strepetilova et al., 1982).The percentages of Gleicheniaceae are 3–5%, up to 12–16%near the Urals and in the Vilyui basin (Fradkina 1967;Markova, 1971), and can locally reach as high as 45–60% innorthern West Siberia (Strepetilova et al., 1982). Pollen ofTaxodiaceae were reported from the Ust’-Yenisei region (Sakset al., 1963). Note that the taxa that appear at base of layerswith SPA2 are rather rare. They become more common upthe section, and that may be the reason why they are describedamong characteristic components in spore-pollen assemblagesfrom the stratigraphically higher Valanginian strata (Fig. 6).

The following level was recognized at base of layers withSPA3 (Figs. 3, 4), mainly from the occurrence of characteristicValanginian striate spores of Schizaeaceae (Fig. 4). Thisboundary is commonly defined by the appearance of two tofour species from this group, and their compositions may differslightly in different sections. The inception of Valanginiantaxa continues upwards in the unit, which is its specificfeature. Although the group of striate spores of Schizaeaceae

E.B. Pestchevitskaya / Russian Geology and Geophysics 48 (2007) 941–959 943

Fig. 2. Occurrences of stratigraphically significant spore and pollen taxa of terrestrial plants in Lower Cretaceous strata, northern Siberia (compiled with reference topalynological data from Lower Cretaceous sections of Siberia cited in text).


Fig. 3. Succession of stratigraphic layers with spores and pollen of gymnosperms and correlation among sections of this study. Dashed lines show tentative boundariesof layers. Compiled with reference to (Basov et al., 1970; Zakharov et al., 1983) for Nordvik peninsula, (Bogomolov et al., 1983) for eastern side of Anabar Bay,(Nikitenko et al., 2004) for Severo-Vologochanskaya BH-18; (Zakharov et al., 1999) for Romanovskaya BH-140; (Dmitrievsky, 2000) for Gorshkovskaya BH-1017.1 — sand and sandstone; 2 — sandy siltstone; 3 — sandy silt; 4 — silt; 5 — silty clay; 6 — argillic siltstone; 7 — mudstone; 8 — clay; 9 — pebble; 10 — limyinterbeds and nodules; 11 — life traces of mud-eaters; 12 — sampling sites for palynologic analysis.


Stra

tigra

phic

lay

ers

with

spo

re a

nd p

olle

nM

ain

mar

kers

of

low

er b

ound

ary

Seco

ndar

y m

arke

rs o

f lo

wer

bou

ndar

yC

hara

cter

istic

spo

re-p

olle

n as

sem

blag

es

For

amin

ispo

ris

won

thag

gien

sis,

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lobo

spor

ites

vala

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s, C

icat

rico

sisp

orit

es l

udbr

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ae,

S. s

ubro

tund

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SPA

1: b

ase

of a

nalo

gus

— l

ower

Klim

ovsk

iens

is;

Paks

a Fm

, N

ordv

ik P

enin

sula

:ou

tcro

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, be

ds 3

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, m

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one-

like

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, T

K37

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Low

er K

heta

, Su

khod

udin

ka F

ms,

Sev

ero-

Vol

ogoc

hans

kaya

BH

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CI

988.

6–97

9.3;

sil

tw

ith c

lay

and

sand

int

erbe

ds,

TK

9.3

; So

rtym

Fm,

Rom

anov

skay

a B

H-1

40:

CI

3027

–302

0.5;

mud

ston

e, T

K 1

1

Ince

ptio

ns o

f F

oram

inis

pori

s w

onth

aggi

ensi

s(o

ccas

iona

lly

as c

omm

on c

ompo

nent

of

asse

mbl

age)

, A

equi

trir

adit

es s

pinu

losu

s, A

.ve

rruc

osus

, T

axod

iace

aepo

lleni

tes

spp.

; in

crea

sein

div

ersi

ty o

f gr

anul

ar a

nd s

moo

th s

pore

s of

Schi

zaec

eae

with

inc

eptio

n of

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odiu

msp

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esja

poni

cifo

rmis

, Ly

godi

um g

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obos

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s, T

. be

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ensi

s,T

. gr

osse

tube

rcul

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, C

onca

viss

imis

pori

tes

mul

titu

berc

ulat

us,

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cras

satu

s; i

ncre

ase

indi

vers

ity o

f st

riat

e sp

ores

of

Schi

zaec

eae

beco

min

g co

mm

on c

ompo

nent

of

asse

mbl

age;

ince

ptio

ns o

f C

icat

rico

sisp

orit

es l

udbr

ooki

ae,

C.

perf

orat

us,

C.

subr

otun

dus,

Pli

cate

lla

tric

osta

ta

Incr

ease

in

dive

rsity

of

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iche

niac

eae

with

ince

ptio

n of

Gle

iche

niid

ites

lae

tus,

, G

. ra

silis

Com

mon

pre

senc

e in

low

abu

ndan

ces

ofG

leic

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idit

es s

pp.,

smoo

th m

orph

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e (0

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, ra

rely

up

to 3

%),

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seno

nicu

s,C

icat

rico

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orit

es s

pp.,

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dium

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.,L.

sub

sim

plex

, Tr

ilob

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rite

s sp

p.;

rare

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ispo

ra g

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, I.

api

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ucat

a,Ly

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, C

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assa

tus,

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plan

otub

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latu

s, C

. m

ulti

tube

rcul

atus

, T

. as

per,

T.

vala

njin

ensi

s, T

. be

rnis

sart

ensi

s, T

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osse

tube

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atus

, C

icat

rico

sisp

orit

es t

ersu

s,C

. br

evil

aesu

ratu

s, C

. ha

llei

, C

. su

brot

undu

s,P

lica

tell

a ex

ilio

ides

, A

nem

ia r

emis

sa,

Aeq

uitr

irad

ites

spp

., A

. sp

inul

osus

, A

. ve

rruc

osus

,F

oram

inis

pori

s sp

p.,

F.

won

thag

gien

sis

(occ

asio

nall

y as

com

mon

com

pone

nt o

fas

sem

blag

e),

Taxo

diac

eaep

olle

nite

s sp

p.

Rou

seis

pori

tes

spp.

, P

ilos

ispo

rite

s sp

p.,

Orn

amen

-ti

fera

gra

nula

ta,

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2: l

ower

klim

ovsk

iens

is–u

p-pe

r qu

adri

fidu

s; P

aksa

Fm

, N

ordv

ik P

enin

sula

:m

udst

one-

like

clay

and

arg

illic

silt

; ou

tcro

p 33

,be

ds 5

3–64

, T

K 1

2.5;

out

crop

35,

bed

s 18

–22,

TK

51.

9; A

naba

r B

ay:

outc

rop

1 A

, be

ds 1

–8,

silty

cla

y, T

K 4

7; S

ukho

dudi

nka

Fm,

Seve

ro-

Vol

ogoc

hans

kaya

BH

-18:

CI

979.

3–92

1.7;

int

erca

-la

ted

clay

, si

lt,

and

sand

, T

K 5

7.6;

Sor

tym

Fm

,R

oman

ovsk

aya

BH

-140

: C

I 27

74–2

770;

arg

illic

silts

tone

, T

K 4

; V

yint

oisk

aya

BH

: C

I 30

34–2

800;

silts

tone

, w

ith s

ands

tone

and

mud

ston

e in

terb

eds,

TK

234

; N

yude

yakh

skay

a B

H:

CI

3055

–304

5;si

ltsto

ne,

TK

10;

Kho

lmog

orsk

aya

BH

: C

I 28

60–

2853

; si

ltsto

ne,

TK

7;

Seve

ro-S

ugul

tska

ya B

H:

CI

3024

–302

0.5;

silt

ston

e, T

K 3

.5

Ince

ptio

ns o

f R

ouse

ispo

rite

s sp

p.,

Pil

osis

pori

tes

spp.

, O

rnam

enti

fera

gra

nula

ta,

Cla

vife

ra s

p.;

Ince

ptio

ns o

f C

icat

rico

sisp

orit

es m

inut

aest

riat

us,

C.

pseu

doau

rife

rus,

C.

hall

ei,

C.

brev

ilae

sura

tus;

com

mon

pre

senc

e of

str

iate

and

gra

nula

r sp

ores

of S

chiz

aece

ae (

1–5%

)

Ince

ptio

ns o

f ra

re L

ygod

ium

spl

endi

dum

, L

.om

atum

, Tr

ilobo

spor

ites

gra

ndis

(A

naba

r,R

oman

ovsk

aya

BH

-140

); i

ncre

ase

in a

bund

ance

of F

oram

inis

pori

s w

onth

aggi

ensi

s an

dTa

xodi

acea

epol

leni

tes

spp.

(to

3%

,R

oman

ovsk

aya

BH

-140

)

Abu

ndan

t an

d co

mm

on G

leic

heni

acea

e (1

–5%

),C

icat

rico

sisp

orit

es l

udbr

ooki

ae,

For

amin

ispo

ris

spp.

, F

. w

onth

aggi

ensi

s, r

are

Cic

atri

cosi

spor

ites

min

utae

stri

atus

, A

nem

ia c

heta

ensi

s, a

nd s

peci

esof

str

iate

and

gra

nula

r sp

ores

of

Schi

zaec

eae

appe

arin

g in

str

atig

raph

ical

ly l

ower

lay

ers.

Fig.

4. F

eatu

res

of p

alyn

ostr

atig

raph

ic l

ayer

s, n

orth

ern

Sibe

ria.

CI

— c

ore

inte

rval

(de

pth,

m),

TK

— th

ickn

ess

(m);

bor

ehol

es N

yude

yakh

skay

a, K

holm

ogor

skay

a, S

ever

o-Su

gults

kaya

, Vyi

ntoi

skay

a, R

oman

ovsk

aya

(Zak

haro

v et

al.,

199

9); N

ordv

ik P

enin

sula

, Ana

bar

Bay

, bor

ehol

es S

ever

o-V

olog

ocha

nska

ya, G

orsh

kovs

kaya

. For

lege

nd s

ee F

ig. 3

.


Stra

tigra

phic

lay

ers

with

spo

re a

nd p

olle

nM

ain

mar

kers

of

low

er b

ound

ary

Seco

ndar

y m

arke

rs o

f lo

wer

bou

ndar

yC

hara

cter

istic

spo

re-p

olle

n as

sem

blag

es

Cic

atri

cosi

spor

ites

aus

tral

iens

is,

S. d

orog

ensi

s,F

oram

inis

pori

s da

ilyi

, SP

A3:

upp

er q

uadr

ifid

us–

low

er b

eani

; Pa

ksa

Fm,

Ana

bar

Bay

: ou

tcro

p 1A

,be

ds 9

–19,

silt

y cl

ay,

argi

llic

silt

, in

terc

alat

ed s

ilt

and

sand

ston

e in

upp

er s

ectio

n, T

K 7

2.5;

Nor

dvik

peni

nsul

a: o

utcr

op 3

5, b

eds

31–3

9, a

rgil

lic s

ilt,

TK

33.

6; S

ukho

dudi

nka

Fm,

Seve

ro-V

olog

ocha

n-sk

aya

BH

-18:

CI

921.

7–89

1.6;

sil

t w

ith c

lay

inte

r-be

ds,

TK

30.

1; S

orty

m F

m,

Rom

anov

skay

aB

H-1

40:

CI

2770

–274

7; a

rgil

lic s

iltst

one

with

sand

ston

e an

d m

udst

one

inte

rbed

s, T

K 2

3; K

hol-

mog

orsk

aya

BH

: C

I 28

52–2

625;

silt

ston

e w

ithsa

ndst

one

and

mud

ston

e in

terb

eds,

TK

227

;N

yude

yakh

skay

a B

H:

CI

3045

.6–2

650;

silt

ston

ew

ith s

ands

tone

and

mud

ston

e in

terb

eds,

TK

395.

6; S

ever

o-Su

gults

kaya

BH

: C

I 30

20.5

–302

0;si

ltsto

ne w

ith s

ands

tone

and

mud

ston

e in

terb

eds,

TK

0.5

Ince

ptio

ns o

f L

ower

Val

angi

nian

spe

cies

of

stri

ate

Schi

zaec

eae

(Cic

atri

cosi

spor

ites

doro

gens

is,

C.

aust

rali

ensi

s, C

. m

edio

stri

atus

,C

. ps

eudo

trip

arti

tus,

C.

moh

rioi

des,

C.

imbr

icat

us,

C.

stov

eri,

C.

subr

otun

dus,

C.

verb

itsk

aja)

, fi

rst

four

spe

cies

are

esp

ecia

llych

arac

teri

stic

and

rec

ogni

zed

in s

ever

al s

ectio

ns

Ince

ptio

ns o

f F

oram

inis

pori

s da

ilyi

(co

mm

on),

F.

asym

met

ricu

s (R

oman

ovsk

aya

BH

-140

);F

. A

sym

met

ricu

s pr

esen

t ab

ove

the

boun

dary

in

Ana

bar;

abu

ndan

t A

equi

trir

adit

es (

Nor

dvik

,A

naba

r, b

oreh

ole

Rom

anov

skay

a);

ince

ptio

ns o

fC

ooks

onite

s va

riab

ilis

, R

ouse

ispo

rite

s re

ticu

latu

s(b

oreh

ole

Seve

ro-V

olog

ocha

nska

ya 1

8);

incr

ease

in d

iver

sity

of

gran

ular

spo

res

of S

chiz

aece

aew

ith i

ncep

tion

of L

ygod

ium

pse

udog

ibbe

rulu

m,

L. c

onfo

rme,

L.

obso

letu

m,

Con

cavi

ssim

ispo

rite

sve

rruc

osus

(N

ordv

ik,

Ana

bar)

; in

crea

se i

nab

unda

nce

of T

axod

iace

aepo

lleni

tes

spp.

(to

6.5%

, bo

reho

le R

oman

ovsk

aya)

Com

mon

str

iate

spo

res

of S

chiz

aece

ae (

1–5%

),bu

t so

me

spec

ies

of r

are

occu

rren

ce;

abun

dant

and

com

mon

For

amin

ispo

ris

spp.

,F.

won

thag

gien

sis,

F.

dail

yi,

Cic

atri

cosi

spor

ites

aus

tral

iens

is,

C.

min

utae

stri

atus

, C

. lu

dbro

okia

e, s

moo

thm

orph

otyp

es o

f G

leic

heni

acea

e, T

axod

iace

ae;

rare

Cic

atri

cosi

spor

ites

dor

ogen

sis,

C.

pseu

dotr

ipar

titu

s, C

. m

ohri

oide

s, C

. st

over

i,C

. su

brot

undu

s, C

. ve

rbit

skaj

a, C

. im

bric

atus

,C

. m

edio

stri

atus

, A

ppen

dici

spor

ites

spp

.,A

. sy

msk

iens

is,

Ane

mia

bia

uric

ulat

a,A

. m

acro

rhyz

a, L

ygod

ium

pse

udog

ibbe

rulu

m,

L. o

bsol

etum

, L.

con

form

e, C

onca

viss

imis

pori

tes

verr

ucos

us,

Pil

osis

pori

tes

spp.

, A

equi

trir

adit

essp

p.,

Rou

seis

pori

tes

reti

cula

tus,

Coo

kson

ites

vari

abil

is,

For

amin

ispo

ris

asym

met

ricu

s,G

leic

heni

acea

e sp

ores

with

orn

amen

tatio

n

App

endi

cisp

orit

es s

pp.,

Tril

obos

pori

tes

purv

erul

en-

tus,

C.

ural

ensi

s, S

PA4:

low

er b

eani

–mid

dle

bidi

-ch

otom

us;

Paks

a Fm

, A

naba

r B

ay:

outc

rop

1A,

beds

20–

21,

inte

rcal

ated

silt

and

san

dsto

ne,

TK

6.2;

Suk

hodu

dink

a Fm

, Se

vero

-Vol

ogoc

hans

kaya

BH

-18:

CI

891.

6–86

5.3;

int

erca

late

d si

lt,

clay

,an

d sa

nd,

TK

26.

3

Ince

ptio

ns o

f Sc

hiza

ecea

e st

riat

e sp

ores

with

apic

al o

rnam

enta

tion

(App

endi

cisp

orit

es s

pp.,

A.

parv

iang

ulat

us,

A.

prob

lem

atic

us);

inc

eptio

ns o

fne

w s

peci

es o

f Sc

hiza

ecea

e gr

anul

ar s

pore

s(T

rilo

bosp

orit

es p

urve

rule

ntus

, C

. m

irab

ilis

,T.

ura

lens

is)

Som

e sp

ecie

s of

gra

nula

r sp

ores

of

Schi

zaec

eae

beco

min

g co

mm

on c

ompo

nent

of

asse

mbl

age

(Tri

lobo

spor

ites

bem

issa

rten

sis,

T.

vala

njin

ensi

s,Ly

godi

um s

plen

didu

m)

Abu

ndan

t an

d co

mm

on s

moo

th m

orph

otyp

es o

fG

leic

heni

acea

e, C

icat

rico

sisp

orit

es a

ustr

alie

nsis

,C

. lu

dbro

okia

e, C

. m

inut

aest

riat

us,

For

amin

ispo

ris

spp.

, Ly

godi

umsp

orit

es s

pp.,

Con

cavi

ssim

ispo

rite

s m

ulti

tube

rcul

atus

,C

. m

acro

tube

rcul

atus

, Tr

ilob

ospo

rite

sbe

rnis

sart

ensi

s, T

. as

per,

Lyg

odiu

m s

plen

didu

m,

L. g

ranu

latu

m,

Impa

rdec

ispo

ra s

pp.,

Aeq

uitr

irad

ites

spp

., A

. ve

rruc

osus

, A

. sp

inul

osus

,F

. w

onth

aggi

ensi

s, F

. da

ilyi

, R

ouse

ispo

rite

s,T

axod

iace

ae;

rare

Cop

tosp

ora

sp.,

Coo

kson

ites

spp.

, R

ouse

ispo

rite

s re

ticu

latu

s, R

. la

evig

atus

,F

oram

inis

pori

s as

ymm

etri

cus,

Gle

iche

niac

eae

spor

es w

ith o

rnam

enta

tion,

App

endi

cisp

orit

essp

p.,

A.

parv

iang

ulat

us,

A.

prob

lem

atic

us,

Cic

atri

cosi

spor

ites

cun

eifo

rmis

, C

. ex

ilis

,C

. m

yrte

llii,

Trilo

bosp

orit

es v

erru

cosu

s,T

. pe

rver

ruca

tus,

T.

mir

abil

is,

T. u

rale

nsis

,T.

mac

roth

elis

, Ly

godi

um e

norm

e, L

. ru

fesc

ens,

L.

cret

aceu

m,

L. c

risp

aefo

rmis

, L.

tri

angu

latu

m,

L. c

onco

rs,

Pol

ypod

iace

ae

Fig.

4 (

cont

inue

d)


Stra

tigra

phic

lay

ers

with

spo

re a

nd p

olle

nM

ain

mar

kers

of

low

er b

ound

ary

Seco

ndar

y m

arke

rs o

f lo

wer

bou

ndar

yC

hara

cter

istic

spo

re-p

olle

n as

sem

blag

es

Ruf

ford

iasp

ora

goep

pert

i, A

equi

trir

adit

es s

pp.,

Or-

nam

enti

fera

tub

ercu

lata

, O

. ec

hina

ta,

SPA

5: m

id-

dle

bidi

chot

omus

–upp

er L

ower

Hau

teri

vian

;Pa

ksa

Fm,

Nor

dvik

pen

insu

la:

outc

rop

36,

bed

11,

sand

, T

K 2

; Su

khod

udin

ka F

m,

Seve

ro-V

olo-

goch

ansk

aya

BH

-18:

CI

865.

3–84

2.3;

int

erca

late

dsi

lt a

nd s

ands

tone

, T

K 2

3; A

kha

Fm,

Gor

shko

vska

ya B

H-1

017:

CI

2763

–263

8; m

ud-

ston

e, T

K 1

25

Ince

ptio

ns o

f R

uffo

rdia

spor

a go

eppe

rti;

Aeq

uitr

irad

ites

spp

., A

. sp

inul

osus

, A

. ve

rruc

osus

beco

min

g co

mm

on c

ompo

nent

of

asse

mbl

age

Ince

ptio

ns o

f O

rnam

entif

era

tube

rcul

ata,

Z. e

chin

ata,

Z.

pere

grin

a, L

ygod

ium

orn

atum

;C

icat

rico

sisp

orit

es s

ubro

tund

us,

Orn

amen

tifer

abe

com

ing

com

mon

com

pone

nt o

f as

sem

blag

e(S

ever

o-V

olog

ocha

nska

ya B

H-1

8);

ince

ptio

n of

Impa

rdec

ispo

ra m

aryl

ande

nsis

, co

mm

onA

equi

trir

adit

es s

pp.,

A.

verr

ucos

us b

ut l

esse

rab

unda

nce

of s

tria

te s

pore

s of

Sch

izae

ceae

,ab

sent

Ruf

ford

iasp

ora

(Nor

dvik

pen

insu

la)

Abu

ndan

t an

d co

mm

on s

moo

th a

nd o

ram

ente

dG

leic

heni

acea

e, C

icat

rico

sisp

orit

es s

pp.,

C.

subr

otun

dus,

C.

ludb

rook

iae,

Aeq

uitr

irad

ites

spp.

, A

. ve

rruc

osus

, A

. sp

inul

osus

,F

. w

onth

aggi

ensi

s, T

axod

iace

ae;

rare

Orn

amen

tifer

a tu

berc

ulat

a, O

. ec

hina

ta,

O.

pere

grin

a, L

ygod

ium

orn

atum

, L.

cot

idia

num

,C

onca

viss

imis

pori

tes

clar

us,

Pil

osis

pori

tes

spp.

,P

. pa

rvis

pini

nosu

s, R

uffo

rdia

spor

a sp

p.,

R.

goep

pert

i, R

uffo

rdia

ara

lica

, H

epat

iace

ae,

stri

ate

and

gran

ular

spo

res

of S

chiz

aece

ae f

ound

in

unde

rlyi

ng l

ayer

s

Cic

atri

cosi

spor

ites

ter

sus,

For

amin

ispo

ris

spp.

,Ta

xodi

acea

epol

leni

tes

spp.

, SP

A6:

upp

er L

ower

Hau

teri

vian

–low

er U

pper

Hau

teri

vian

;C

herk

ashi

no F

m,

Gor

shko

vska

ya B

H-1

017:

CI

2638

–262

6.8;

mud

ston

e, T

K 1

1.2

Incr

ease

in

abun

danc

e of

Tax

odia

ceae

polle

nite

ssp

p. (

up t

o 17

%,

8% o

n av

erag

e)In

crea

se i

n di

vers

ity o

f C

icat

rico

sisp

orit

esC

omm

on r

elat

ivel

y hi

gh a

bund

ance

of

Tax

odia

ceac

eae

(4–1

7%,

8% o

n av

erag

e);

abun

dant

and

com

mon

Ebo

raci

aspo

rite

ssp

p.,G

leic

heni

idit

es s

enon

icus

; di

vers

eF

oram

inis

pori

s sp

p.;

rare

Cic

atri

cosi

spor

ites

spp

.,C

. do

roge

nsis

, C

. te

rsus

, C

. lu

dbro

okia

e,A

equi

trir

adit

es s

pp.,

Orn

amen

tifer

a sp

p.,

gran

ular

spor

es o

f Sc

hiza

ecea

e

Pil

osis

pori

tes

note

nsis

, P

. ec

hina

ceus

SPA

7:

low

-er

mos

t U

pper

Hau

teri

vian

; C

herk

ashi

no F

m,

Gor

shko

vska

ya B

H-1

017:

CI

2626

.8–2

615;

mud

-st

one,

TK

11.

8

Ince

ptio

ns o

f H

aute

rivi

an s

peci

es P

ilos

ispo

rite

s(P

. ec

hina

ceus

, P

. no

tens

is,

Gle

iche

niid

ites

tori

conc

avus

); C

icat

rico

sisp

orit

es d

orog

ensi

sbe

com

ing

com

mon

com

pone

nt o

f as

sem

blag

e

—

Com

mon

rel

ativ

ely

high

abu

ndan

ce o

fT

axod

iace

acea

e (4

–19%

, 10

% o

n av

erag

e);

abun

dant

and

com

mon

Cic

atri

cosi

spor

ites

spp

.,C

. do

roge

nsis

, C

. te

rsus

, C

. lu

dbro

okia

e,G

leic

heni

idit

es s

enon

icus

, A

equi

trir

adit

es s

pp.,

Gne

tace

aepo

llen

ites

spp

.; ra

re d

iver

seG

leic

heni

acea

e, s

tria

te,

gran

ular

, an

d sp

inou

ssp

ores

of

Schi

zaec

eae,

Hep

atia

ceae

Lygo

dium

lon

gipi

losu

m,

Pil

osis

pori

tes

hirs

utus

,R

ouse

ispo

rite

s la

evig

atus

, R

. ra

diat

us,

SPA

8:lo

wer

Low

er B

arre

mia

n; C

herk

ashi

no F

m,

Gor

shko

vska

ya B

H-1

017:

CI

2343

–233

0; m

ud-

ston

e an

d si

lty m

udst

one,

TK

13

Incr

ease

in

dive

rsity

of

spin

ous

spor

es o

fSc

hiza

ecea

e w

ith i

ncep

tion

of P

ilos

ispo

rite

shi

rsut

us,

Lygo

dium

lon

gipi

losu

m,

L. c

alvu

m;

Pil

osis

pori

tes

spp.

, R

ouse

ispo

rite

s sp

p. b

ecom

ing

com

mon

com

pone

nt o

f as

sem

blag

e

—

Abu

ndan

t T

axod

iace

aepo

lleni

tes

spp.

(6–

22%

);co

mm

on r

elat

ivel

y hi

gh a

bund

ance

s of

Gle

iche

-ni

idit

es s

pp.

(4.5

–7.5

%),

Cic

atri

cosi

spor

ites

spp

.(2

–6%

); c

omm

on l

ow p

erce

ntag

es o

fG

leic

heni

idit

es s

enon

icus

(2–

3%);

fre

quen

t an

dco

mm

on C

icat

rico

sisp

orit

es d

orog

ensi

s,C

. lu

dbro

okia

e, C

. te

rsus

, P

ilos

ispo

rite

s sp

p.,

Rou

seis

pori

tes

spp.

, A

equi

trir

adit

es s

pp.;

dive

rse

stri

ate,

gra

nula

r, a

nd s

pino

us s

pore

s of

Schi

zaec

eae

Fig.

4 (

cont

inue

d)


Fig.

5. P

alyn

olog

ical

bac

kgro

und

for

stra

tigra

phic

pos

ition

of

laye

rs w

ith s

pore

s an

d po

llen

and

dist

ribu

tion

of s

trat

igra

phic

ally

sig

nifi

cant

tax

a. F

requ

ency

: 1

— r

are;

2 —

com

mon

; 3

— 6

–10%

, 4 —

10–

20%

.


Fig.

5 (

cont

inue

d)


Fig.

5 (

cont

inue

d)


in general, as well as some Berriasian-Valanginian species,are common, the characteristic species are rare. Therefore,increasing diversity of Schizaeaceae striate spores with incep-tions of significant Valanginian species appears to be a morereliable marker than the occurrence of any single taxon. Somespecies of striate and granular Schizaeaceae diagnostic of

layers with SPA3 were also reported from the Lower Valang-inian in the literature, i.e., they are typical of the LowerValanginian substage (Fig. 6). The level is easily identifiedfrom additional markers which are also found in coevalspore-pollen assemblages of Siberia (Figs. 4, 6).

Quantitative taxa proportions show considerable variations

Stratigraphic levels defined by spores and pollen in sections of this study Occurrences elsewhere in Northern Siberia

Level Palynological marker

Lower boundary of Foraminisporiswonthaggiensis, Trilobosporitesvalanjinensis, Cicatricosisporitesludbrookiae, C. subrotundus, SPA1: base ofanalogus (base of kochi according topublished data)

Inceptions of Aequitriradites spinulosus,A. verrucosus

Finds start with Hectoroceras kochi Zone: Khatanga basin(Fedorova et al., 1993; Golbert, 1981)

Inceptions of Taxodiaceaepollenites spp. Finds start with Hectoroceras kochi Zone: Khatanga basin(Fedorova et al., 1993; Golbert, 1981; Pavlov, 1969, 1970),Lena-Olenek region (Korotkevich, 1962); few specimens inBerriasian assemblages in northern Lena-Anabar basin(Lyubomirova and Kislyakov, 1985)

Increase in diversity of granular andsmooth spores of Schizaeceae withinception of Lygodiumsporitesjaponiciformis, Lygodium granulatum,Trilobosporites valanjinensis,T. bernissartensis, T. grossetuberculatus,Concavissimisporites multituberculatus, C. crassatus

Finds start with Hectoroceras kochi Zone: Khatanga basin(Fedorova et al., 1993; Golbert, 1981; Pavlov, 1969, 1970),Lena-Olenek region (Korotkevich, 1962); Concavissimisporitesmultituberculatus finds start with Surites analogus, SubarcticUrals (Fedorova et al., 1993); also presentConcavissimisporites planotuberculatus, Impardecisporagibberula, Lygodium conspectus

Increase in diversity of Gleicheniaceaewith inception of Gleicheniidites laetus,G. rasilis

Finds start with Hectoroceras kochi Zone: Khatanga basin(Pavlov, 1969, 1970; Fedorova et al., 1993), Subarctic Urals(Markova, 1971; Golbert et al., 1972); also present Pliciferadelicata, Gleicheniidites umbonatus, G. circiniidites,Gleichenia angulata, G. stellata

Increase in diversity of striate spores ofSchizaeceae with inception of Cicatricosi-sporites perforatus, C. ludbrookiae,C. subrotundus, Plicatella tricostata

Finds start with Hectoroceras kochi Zone: Khatanga basin(Pavlov, 1969, 1970; Fedorova et al., 1993), Subarctic Urals(Markova, 1971; Golbert et al., 1972); also presentCicatrisporites tersus, Plicatella exilioides, Anemia remissa;present in Berriasian assemblages: Plicatella tricostata (northof Lena–Anabar region (Lyubomirova and Kislyakov, 1985)),Plicatella exilioides (Kharabyl River (Kara-Murza, 1960))

Inception of Foraminisporis wonthaggiensisabove base of Surites analogus,occasionally as common component ofassemblage

Present in Valanginian assemblages in Ob’ lower reaches(Mchedlishvili, 1971)

Lower boundary of Rouseisporites spp.,Cicatricosisporites minutaestriatus,Pilosisporites spp., Ornamentiferagranulata, SPA2: lower klimovskiensis zone

Inception of Cicatricosisporitesminutaestriatus

Found in transitional Berriasian-Valanginian assemblages,Tyumenskaya superdeep BH-6 (Kirichkova et al., 1999), andlower Lower Valanginian, Frolovo region (Shirokova, 1973),absent from Berriasian

Inceptions of Rouseisporites spp. Common since Hauterivian, Lena-Olenek region (Lyubomirovaand Kislyakov, 1985)

Inceptions of Pilosisporites spp. Present in Valanginian assemblages, Ob’ lower reaches(Mchedlishvili, 1971)

Inceptions of Gleicheniaceae spores withornamentation (Ornamentifera granulata,Clavifera sp.)

Found since Upper Valanginian, Khatanga basin (Golbert,1981)

Inception of new species of granularSchizaeceae: Lygodium splendidum, L.ornatum, Trilobosporites grandis

Lygodium splendidum: Upper Berriasian–Lower Valanginian,Khatanga basin (Kara-Murza, 1960), Ust’-Yenisei region (Sakset al., 1963); L. ornatum: Hauterivian, Gubka region (Rybak,1984); Trilobosporites grandis found since middle LowerValanginian, Malaya Kheta region (Popovicheva, 1984); alsoConcavissimisporites spasituberculatus reported from Ust’-Yenisei region and Lygodium triangulatum reported fromTyumen’ region.

Fig. 6. Correlation significance of stratigraphic marker levels defined by spores and pollen of gymnosperms. In bold are palynologic events recognizeable at samestratigraphic levels outside sections of this study, from published evidence.


with geography. Striate and granular spores of Schizaeaceaeare most often 2–3% increasing to 10 or even 20% (Khatangabasin) in northern areas (Bezrukova, 1994; Chirva et al., 1979;Korzh, 1978; Lyubomirova and Kislyakov, 1985; Pavlov,1969; Sologub, 1989). Percentages of Gleicheniaceae arecommonly 2–5% in the Subarctic Urals and 10–28% inwestern West Siberia (Fedorova et al., 1993; Golbert et al.,1972; Markova, 1971) but as high as 48% in the Frolovo andNadym regions, and even up to 68 % in Neocomian strata ofthe Vilyui basin (Fradkina, 1967; Shirokova, 1973; Sologub,1989). Taxodiaceae are commonly few but amount to 11% inthe Subarctic Urals (Markova, 1971). Note that Taxodiaceaereach 1–6.5% at base of layers with SPA3 in RomanovskayaBH-140.

Upper Lower and Upper Valanginian spore-pollen assem-blages (layers with SPA4 and SPA5) are characterized bycommon occurrences of Aequitriradites and diverse Schi-zaeaceae (Figs. 3, 4). The assemblage from the NordvikPeninsula bears rare striate Schizaeaceae and no Ruffordias-pora (Fig. 4). This possibly because the section is located farin the north while striate spores are considered to beheat-loving components of the assemblages.

The taxonomic diversity of Schizaeaceae was noted byother palynologists as well. Cicatricosisporites dorogensisPotonie et Gelletich, C. minutaestriatus, C. cuneiformis Po-cock, Trilobosporites verrucosus (Delcourt et Sprumont) Vo-ronova, T. purverulentus (Vervitskaya) Bondarenko, and otherspecies, of which many occur in the reported sections, were



Lower boundary of Cicatricosisporitesaustraliensis, C. dorogensis, Foraminisporisdailyi, SPA3: upper quadrifidus zone

Inceptions of Lower Valanginian speciesof striate Schizaeceae: Cicatricosisporitesdorogensis, C. australiensis,C. mediostriatus, C. pseudotripartitus,C. mohrioides, C. imbricatus, C. stoveri,C. subrotundus, C. verbitskaja

Cicatricosisporites dorogensis, C. australiensis, C.mediostriatus, C. pseudotripartitus found in Valanginianassemblages in Ob’-Nadym (Korzh, 1978), Frolovo (Sologub,1994), Gubka (Strepetilova and Rybak, 1989), Tambei(Strepetilova, 1989), and Malaya Kheta regions and in PurRiver catchment (Popovicheva, 1984); also presentCicatricosisporites cooksonii, C. minor, Plicatella sibirica,Anemia dorsostriata, A. phyllitidiformis

Inceptions of Foraminisporis asymmetricus,F. dailyi

Foraminisporis dailyi found since upper Lower Valanginian,Lena-Anabar basin (Lyubomirova, Kislyakov, 1985), and inLower Valanginian, Khatanga basin (Chirva et al., 1979)

More frequent occurrence of Aequitriradites Found in Valanginian assemblages in Subarctic Urals(Markova, 1971), Ob’ lower reaches (Mchedlishvili, 1971),and in Frolovo (Sologub, 1994), Surgut, Tyumen’(Bochkareva, 1970; Rybak et al., 1987), Gubka (Rybak, 1984),Nadym (Sologub, 1989), and Ust’-Yenisei (Sheiko, 1970)regions; abundant in Nyda region (Strepetilova andDenisyukova, 1987), sporadic in Lar’yak region (Bezrukova,1989)

Inceptions of Cooksonites variabilis,Rouseisporites reticulatus

Rare Cooksonites variabilis found in upper LowerValanginian; common Rouseisporites spp. found sinceHauterivian, Lena-Olenek region (Lyubomirova and Kislyakov,1985)

Increase in diversity of granular sporesof Schizaeceae with inception ofLygodium pseudogibberulum, L. conforme, L. obsoletum, Concavissimisporitesverrucosus

Lygodium pseudogibberulum, Ust’-Yenisei region (Sheiko,1970), Concavissimisporites verrucosus, Malaya Kheta region(Popovicheva, 1984), and Lygodium obsoletum, Lar’yak region(Bezrukova, 1989) found since middle Lower Valanginian;also present Lygodium smithianiformis, Malaya Kheta region(Popovicheva, 1984), and Lygodium concors, Ob’ lowerreaches (Mchedlishvili, 1971)

Lower boundary of Appendicisporites spp.,Trilobosporites purverulentus, T. uralensis,SPA4: lower beani zone

Inceptions of striate spores ofSchizaeceae with apical ornamentation(Appendicisporites spp., A. parviangulatus,A. problematicus)

Few specimens of Appendicisporites spp. found since middleLower Valanginian, Khatanga basin (Golbert, 1981)

Inceptions of new species of granularspores of Schizaeceae (Trilobosporitespurlerulentus, T. mirabilis, T. uralensis,Impardecispora. marylandensis)

Trilobosporites mirabilis found since upper LowerValanginian, Siberites ramulicosta, Khatanga basin (Golbert,1981) and Trilobosporites uralensis found since Hauterivian,Gubka region (Strepetilova and Rybak, 1989)

Some species of granular spores ofSchizaeceae becoming commoncomponent of assemblage (Trilobosporitesbernissartensis, Lygodium splendidum)

Common Trilobosporites valanjinensis found in middle andupper Valanginian-Lower Hauterivian assemblages, Khatangabasin (Kara-Murza, 1960)

Fig. 6 (continued)


found in sediments with fauna typical of the Siberitesramulicosta–Polyptychites beani Zones in the Lena-Anabarregion (Lyubomirova and Kislyakov, 1985). Foraminisporisdailyi are common there, Cooksonites variabilis Pocock andForaminisporis asymmetricus (Cookson et Dettmann) Dett-mann are sporadic. Deposits with Polyptychites spp. in theKhatanga basin comprise relatively abundant Schizaeaceae,

few specimens of Polypodiaceae (Pavlov, 1969), and commonTrilobosporites valanjinensis (Kara-Mursa) Doring. The latteris a diagnostic feature of palynostratigraphic layers with SPA4.The presence of Cicatricosisporites tersus (Bolchovitina)Pocock is often reported from Valanginian assemblages; itreaches 6% in the Lena-Olenek region (Vasilevskaya andPavlov, 1963). Aeqiutriradites species are common in Upper



Lower boundary of Ruffordiasporagoepperti, Aeqiutriradites spp.,Ornamentifera spp., O. echinata, SPA5:middle bidichotomus zone

Inception of Ruffordiaspora goepperti Common in Hauterivian assemblages from Nadym-Taz region(Strepetilova, 1984)

Aeqiutriradites spp., A. spinulosus, A.verrucosus becoming common componentof assemblage

Common Aeqiutriradites spp. found in Upper Valanginianassemblages of Subarctic Urals (Golbert et al., 1972), UpperValanginian–Hauterivian assemblages from Lena lower reaches(Kovalskaya, 1980), and in Middle Balyk and Tyumen’ fields(Bochkareva, 1970)

Inceptions of Ornamentifera tuberculata, O. echinata, O. peregrina, Lygodiumornatum

Ornamentifera tuberculata found since Hauterivian,O. echinata found since Barremian, Frolovo region (Sologub,1994), Lygodium ornatum found since Hauterivian, Gubkaregion (Strepetilova and Rybak, 1989)

Cicatricosisporites subrotundus andOrnamentifera becoming commoncomponent of assemblage

No data

Lower boundary of Cicatricosisporitestersus, Foraminisporis spp.,Taxodiaceaepollenites spp., SPA 6: upperLower Hauterivian

Apparently reflects local palynologicalevents

Increase in diversity of Cicatricosisporites(C. tersus, C. minutaestriatus, C.mediostriatus, C. dorogensis)

Found in West and Central Siberia in stratigraphically lowerstrata, in Valanginian

Increase in abundance ofTaxodiaceaepollenites spp. (4.6–17%, 8% on average)

Geographically variable percentages

Lower boundary of Pilosisporites notensis,P. echinaceus, SPA7: lowermost UpperHauterivian

Inceptions of Pilosisporites echinaceus,P. notensis, Gleicheniidites toriconcavus

Pilosisporites spinosus, P. horridus, P. echinaceus, P. hirsutus,Lygodium microaculeatus, L. ungulatum, L. setiferum,L. calvum, L. parvum, L. longipilosum found in Hauterivianassemblages in Ob’-Nadym (Bezrukova, 1994), Nyda(Strepetilova and Denisyukova, 1987), and Gyda (Strepetilova,1994) regions; Gleicheniidites toriconcavus found sinceHauterivian, Frolovo region (Shirokova, 1973)

Cicatricosisporites dorogensis becomingcommon component of assemblage

Found as common component of Hauterivian assemblagesfrom Lar’yak (Bezrukova, 1989) and Frolovo regions(Shirokova, 1973); also present common Cicatricosisporitesminutaestriatus

Lower boundary of Lygodium longipilosum,Pilosisporites hirsutus, Rouseisporiteslaevigatus, R. radiatus, SPA8: lowermostLower Barremian

Increase in diversity of spinous spores ofSchizaeceae with inceptions ofPilosisporites hirsutus, Lygodiumlongipilosum, L. calvum

Found in Hauterivian assemblages in Tobol-Nadym(Bezrukova, 1994), Nyda (Strepetilova, Denisyukova, 1987),and Gyda (Strepetilova, 1994) regions; Lygodium barremicumfound since Barremian, Lar’yak region (Bezrukova, 1989);often 1–4%, up to 15–18% in Yamal (Strepetilova, 1989) andGubka (Strepetilova and Rybak, 1989) regions

Pilosisporites spp., Rouseisporites spp.becoming common component ofassemblage

Rouseisporites spp. becoming common component ofHauterivian assemblages in Lena-Anabar basin (Lyubomirovaand Kislyakov, 1985); spinous spores of Schizaeceae found ascommon component of all Hauterivian assemblages(Bochkareva, 1969, 1970; Bondarenko, 1961; Kara-Murza,1960; Kovalskaya, 1983; Rybak et al., 1987; Saks et al., 1963;Shirokova, 1973; Sologub, 1989, 1994; Strepetilova, 1984,1989, 1994; Strepetilova and Denisyukova, 1987; Strepetilovaand Rybak, 1989; Strepetilova et al., 1982; etc). Most speciesof rare occurrence, but some relatively abundant: Pilosisporiteshorridus (1.3%), P. spinosus (1.3%), Lygodium calvum (1.6%)

Fig. 6 (continued)


Valanginian and Hauterivian assemblages in the SubarcticUrals, in the Latitudinal Ob’ region (to 5%), and in the lowerreaches of the Lena (Fig. 6). The lower Lena assemblages alsocomprise Cooksonites variabilis, diverse granular spores ofSchizaeaceae (Trilobosporites mirabilis (Bolchovitina) Bon-darenko, T. crassiangularis Doring, T. cavernosum (E. Iva-nova) Voronova, Lygodium pseudogibberulum Bolchovitina,etc.), and rare angiosperms (Kovalskaya, 1980). Upper Valan-ginian assemblages elsewhere in Siberia (Bondarenko, 1961;Korotkevich, 1962; Rybak et al., 1987) and Subarctic Urals(Golbert et al., 1972) bear the same species as in the LowerValanginian plus Anemia trichacantha Bolchovitina. The

percentages of Schizaeaceae vary with geography from 1 to18% being the lowest in the Subarctic Urals (1.7–4.2%).

The Hauterivian and Barremian palynostratigraphic unitswere studied only from Gorshkovskaya BH-1017 (Figs. 3, 4).The correlation significance of the stratigraphic boundaries canbe inferred from comparison with spore-pollen assemblagesfound in different areas of northern Siberia. The base of layerswith SPA6 hardly is a reliable marker as Cicatricosisporitesand Ornamentifera found in the assemblage can occur also inValanginian strata. This boundary is mainly defined bypercentage data which are geographically variable and appar-

Fig. 7. Stratigraphic layers with spores and pollen of this study correlated to palynostratigraphic units of previous studies and to Boreal zonal standard.


ently record local features of the spore-pollen flora. The baseof layers with SPA7 is more prominent (Fig. 4).

It is difficult to recognize these levels from publishedevidence where the reported spore-pollen assemblages aremost often of a broad stratigraphic range. Hauterivian assem-blages were documented throughout West and Central Siberia(Golbert et al., 1972; Korzh, 1978; Lyubomirova and Kis-lyakov, 1985; Saks et al., 1963; Sologub, 1994; Strepetilovaand Rybak, 1989). Upper Hauterivian assemblages weredescribed in the Frolovo (Shirokova, 1973) and Ust’-Yenisei(Saks et al., 1963) regions and in the Lena lower reaches(Kovalskaya, 1980). Hauterivian assemblages show a greaterdiversity of striate and granular spores of Schizaeaceae thanthose from stratigraphically lower strata. Valanginian species,of which some are common (1.5% Cicatricosisporites tersus,1.5–3% C. dorogensis, 1.5–3% C. minutaestriatus, 4.5–7%Impadecispora gibberula, 1–3.5% Lygodiumsporites subsim-plex (Bolchovitina) Bondarenko), co-occur in these assem-blages with Anemia phylliditiformis Chlonova, A. cooksonii(Balme) Bolchovitina, A. dorsostriata Bolchovitina, Lygodiumornatum E. Ivanova, and Trilobosporites uralensis (Bol-chovitina) Bondarenko. Abundances of striate Schizaeaceaeare most often low in northern areas (1–3 or occasionally upto 10%) but higher in central West and Central Siberia wherethey reach 9–10 or occasionally 20–30% in the Surgut andUrengoi regions (Popovicheva, 1984). The percentages ofgranular spores of Schizaeaceae vary geographically between2 and 15%, without any notable regularity.

Spore-pollen assemblages from West Siberia commonlycontain 1–5% spinous spores of Schizaeaceae: Pilosisporitesechinaceus (Vervitskaya) Bondarenko, P. hirsutus (E. Iva-nova) Bondarenko, P. horridus (Sachanova et E. Ivanova)Bondarenko, P. notensis Cookson et Dettmann, P. spinosus(E. Ivanova) Bondarenko, Lygodium setiferum Verbitskaya, L.microaculeatus Besrukova et Purtova, L. ungulatum E. Iva-nova, L. longipilosum E. Ivanova, L. calvum E. Ivanova, L.parvum E. Ivanova. These forms were never reported fromnorthern Central Siberia. The level of their first occurrencescannot be determined to sufficient accuracy. The diversity ofspinous Schizaeaceae may be typical of middle and upperHauterivian as no publications mention it for the lowerHauterivian (Bochkareva, 1970; Chirva et al., 1979; Koval-skaya, 1980; Markova, 1971). Lebedeva (Beizel et al., 1997)reported rare Pilosisporites spp. in the Subarctic Urals butgave no details of the taxonomic composition. Upper Hau-terivian assemblages are often characterized by the occurrenceof several species of spinous Schizaeaceae or by inception oftheir new species, as it was also found in GorshkovskayaBH-1017 (Fig. 4, 6).

Gleicheniaceae are most often from 1 to 20% but areabundant (15–50%) and diverse in western West Siberia. Theoccurrence of few specimens of Clavifera and Ornamentiferaand inception of Gleicheniidites toriconcavus Krutzsch werereported from the Khatanga basin (Golbert, 1981; Shirokova,1973). The presence of Hepatiaceae is typical, namely Aequi-triradites spp. is a common component of the assemblage andreach 6% in central West Siberia and in northern Yakutia

(Bezrukova, 1994; Bochkareva, 1970; Sologub, 1994; Stre-petilova, 1994; Strepetilova and Rybak, 1989). Cooksonitesvariabilis, Foraminisporis dailyi, F. asymmetricus, and Rou-seisporites were reported from the Khatanga basin and theLena-Anabar interfluve (Chirva et al., 1979; Lyubomirova andKislyakov, 1985). Taxodiaceae are 1–3 and amount to 20%in the lower reaches of the Ob’ (Mchedlishvili, 1971).Sporadic angiosperms were found in the Khatanga basin andin the Lena lower reaches (Chirva et al., 1979; Kovalskaya,1980).

Lower Barremian spore-pollen assemblages (SPA8) com-monly contain diverse Pilosisporites and Rouseisporites; spi-nous Schizaeaceae show inception of new species (Fig. 4).According to published evidence (Kara-Murza, 1960; Koval-skaya, 1983; Rybak et al., 1987; Sologub, 1989, 1994;Strepetilova, 1984, 1989, 1994), striate and granular Schi-zaeaceae become more abundant in the Barremian but theirnumbers strongly vary with geography (from 7 to 37 and from3 to 50 %, respectively). High abundances (50–60%) of theseforms are occasionally found in northern West Siberia (Stre-petilova et al., 1982). Anemia imperfectus (Maljavkina) Bol-chovitina, A. crimensis Bolchovitina make their firstappearance there; Cicatricosisporites tersus reaches relativelyhigh percentages (1–4%) in the Lena-Olenek region. Polypo-diaceae and Hepatiaceae are common, the latter includingRouseisporites spp., Aequitriradites spp. (up to 4% in theMiddle Balyk field), and Foraminisporis asymmetricus (Bo-chkareva, 1970). Kuylisporites lunaris Cookson et Dettmannand angiosperms occur sporadically (Sologub, 1994; Strepe-tilova and Rybak, 1989). Taxodiaceae are as high as 20% inthe Ob’ lower reaches but are most often about 1–3%(Mchedlishvili, 1971). Spinous Schizaeaceae are diversethroughout West Siberia, which is also typical of the assem-blage from Gorshkovskaya BH-1017 (Fig. 4, 6).

Conclusions

The spore-and-pollen analysis of Lower Cretaceous sec-tions in northern Siberia revealed a succession of eightbiostratigraphic layers with spores and pollen of gymnospermswhich was reliably calibrated against the Boreal zonal stand-ard. The stratigraphy of the layers was additionally controlledby dated fauna and dinocyst records (Fig. 7). Changes in thesystematic composition of spore-pollen assemblages and per-centage data (as a subsidiary diagnostic criterion) were usedto obtain a stratigraphic subdivision of the Lower Cretaceousof Siberia more detailed than it was suggested earlier (Fig. 7).The new data were included into the updated stratigraphicchart of West Siberia (Devyatov and Nikitenko, 2007).

The reported sections are depth-stacked over one another,with partial overlap, which allowed identifying several iso-chronous levels with the same palynological features. UpperHauterivian and Barremian palynostratigraphic layers (SPA6–SPA8) were recognized only using data from the LatitudinalOb’ region collected by Pestchevitskaya. The other layers areproven by the published evidence and can be traced over long


distances through northern Siberia. The isochronous levelsmay serve as stratigraphic markers and, possibly, as bounda-ries of future zones. Characteristic features of upper Berri-asian-lowermost Valanginian spore-pollen assemblages(SPA1) are identifiable in the Subarctic Urals, Pur-Tazinterfluve, Khatanga basin, and Lena-Olenek region. Striateand granular spores of Schizaeaceae, which are diagnostic ofthe lower and middle Lower Valanginian (SPA2, SPA3), occurin coeval assemblages in central and northern West Siberiaand in the Khatanga basin. The features of middle Valanginianspore-pollen assemblages (SPA4) show up in the Khatangabasin, Ust’-Yenisei and Lena-Anabar regions and those ofupper Valanginian assemblages (SPA5) are found in theSubarctic Urals, central West Siberia, Khatanga basin, andnorthern Yakutia. Thus, the boundaries of the layers withspores and pollen provide a good potential for Siberianregional stratigraphic correlation.

Note that the palynologic biostratigraphic units were dis-tinguished primarily proceeding from the inceptions of strati-graphically significant taxa while percentage data turned outto be more ambiguous because of rather high variability.Percentages of characteristic Cretaceous taxa gradually in-crease in individual sections but differ considerably whencompared among coeval assemblages. Therefore, the genericand specific composition of spore-pollen assemblages is amore reliable diagnostic tool than percentage data which canbe used rather as secondary stratigraphic markers.

I wish to thank N.K. Lebedeva, B.L. Nikitenko, A.F. Frad-kina, V.I. Ilyina, A.V. Kanygin, V.A. Zakharov, B.N. Shury-gin, S.V. Meledina, V.P. Devyatov, and A.L. Beizel for usefuldiscussions. Samples for spore-and-pollen analysis are cour-tesy of Yu.I. Bogomolov, V.A. Kazanenkov, V.A. Marinov,L.A. Glinskikh, and O.O. Savchenkova.

The study was supported by grants 06-05-64224 and06-05-64291 from the Russian Foundation for Basic Research.

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Lower Cretaceous biostratigraphy of Northern Siberia: palynological units and their correlation significance