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ISSN 08695938, Stratigraphy and Geological Correlation, 2010, Vol. 18, No. 1, pp. 83–104. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © O.N. Vasil’eva, V.A. Musatov, 2010, published in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2010, Vol. 18, No. 1, pp. 88–109.
83
INTRODUCTION
The biostratigraphy of Paleogene deposits in the
Volga–Caspian region has been under elaboration for
over a century and remain an object of interest to date.
The acknowledged lithostratigraphic units of the
“stage” and formation ranks, distinguished in the
region as a result of geological research in the past cen
tury (Pavlov, 1896; Arkhangelsky, 1928; Leonov,
1961), are the Syzranian “Stage” (Syzran Fm) with
the Belogrodhya (Grodnya) Beds, the Saratovian
“Stage” (Saratov Fm), and the Kamyshin Fm. The
age of the units was determined based first on mol
lusks, the most frequently occurring fossils, and then
on foraminiferal assemblages and palynological spec
tra (Morozova, 1960; Zubkovich, 1960; Leonov, 1961;
Ermokhina, 1990). Typically, now, the ordinary struc
ture of the Paleogene succession is observable in quar
ies and natural exposures on the right side of the
Volga’s middle reaches. The current substantiation of
lithostratigraphic units distinguishable in the region is
based predominantly on the distribution of foramini
fers, diatoms, radiolarians, and dinoflagellates studied
in particular sections (Grachev et al., 1971; Kurlaev
and Akhlestina, 1988; Aleksandrova, 2001; Musatov
and Khristenko, 2004; Musatov and Zaporozhets,
2000; Aleksandrova and Radionova, 2006; Oreshkina
Paleogene Biostratigraphy of the North CircumCaspian Region
(Implication of the Dinocysts and Nannoplankton
from the Novouzensk Reference Borehole),
Part 1: Age Substantiation and Correlation of Deposits
O. N. Vasil’eva
a
and V. A. Musatov
b
a
Institute of Geology and Geochemistry, Urals Branch, Russian Academy of Sciences, Russia
email: vasilyeva@igg.uran.ru
b
Lower Volga Research Institute of Geology and Geophysics, Russia
email: vamusatov@nvniigg.san.ru
Received December 18, 2008; in final form, July 20, 2009
Abstract
—Eight zonal dinocyst assemblages and three biostratigraphic units ranked as “beds with flora” are
first distinguished in the Danian–lower Lutetian interval of the Paleogene succession, penetrated by the ref
erence borehole Novousensk no. 1, where eight standard and one local nannoplankton zones are simulta
neously recognized. The direct correlation of nannoplankton and dinocyst zones is used to refine the paleon
tological substantiation and stratigraphic position of regional lithostratigraphic units, ranges of hiatuses, and
the correlation with the general stratigraphic scale. The nannoplankton of the Danian NP2
Cruciplacolithus
tenuis
and NP3
Chiasmolithus danicus
zones is characteristic of the Algai Formation (Fm). The nannoplank
ton of the NP4
Coccolithus robustus
Zone and dinocysts of the D3a
Alterbidinium circulum
Zone from the
Tsyganovo Fm characterizes the Danian top. The Lower Syzran Subformation (Subfm) corresponds to the
upper part of the NP4
Coccolithus robustus
Zone (
Neochiastizygus junctus
local zone) and to the D3b (part)
Cerodinium depressum
Zone of the Selandian dinocysts. The latter spans part of the Upper Syzran Subforma
tion, whose characteristic nannofossils are the nannoplankton of the NP5
Fasciculithus tympaniformis
Zone
and the dinocysts of the D3b (part)
Isabelidinium? viborgense
Zone of the Selandian. The Novouzensk Fm is
represented by a succession of the dinocyst
Cerodinium markovae
Beds and the standard D4c
Apectodinium
hyperacanthum
Zone of the upper Thanetian. The coccolitophorids of the lower Thanetian NP6
Heliolithus
kleinpelli
Zone occur at the formation base. The Bostandyk Fm includes successive biostratigraphic units of
the Ypresian. In the dinocyst scale, these are the D5a
Apectodinium augustum
Zone, the
Pterospermella
Beds
(DE1a Zone of the North Sea scale), and zones DE1bc
Deflandrea oebisfeldensis
, D7c
Dracodinium varielon
gitudum
, and D8
Dracodinium politum–Charlesdowniea coleothrypta
, while units of the nannoplankton scale
correspond to the NP12
Martasterites tribrachiatus
and NP13
Discoaster lodoensis
zones. The Kopterek Fm
yields Lutetian nannofossils: the nannoplankton of the NP14
Discoaster sublodoensis
Zone and the dinocysts
of the
Wetzeliella coronata–Areosphaeridium diktyoplokum
Beds. Three meaningful hiatuses are established
at the Danian base, Selandian top, and in the lower Ypresian.
Key words
: Paleocene, Eocene, North circumCaspian region, dinocysts, nannoplankton.
DOI:
10.1134/S0869593810010065
84
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
and Aleksandrova, 2007). Data on the distribution of
nannofossils in Paleogene sections of the Circum
Caspian region (Novouzensk, Elton, and other refer
ence boreholes), which are most complete, in terms of
stratigraphy, in contrast to the reduced sections on the
right side of the Volga River, have allowed the ages of
the distinguished formations and their positions in the
general stratigraphic scale to be considerably refined
(Musatov, 1993; Musatov et al., 2004). On the other
hand, the designated sections include alternating
intervals of carbonate and siliciclastic deposits, inade
quately studied in terms of multidisciplinary paleonto
logical research, which is an obstacle for the strati
graphic subdivision and correlation of different sedi
mentary facies, and for the precise determination of
boundaries and ranges of lithostratigraphic units.
The recent stratigraphic chart suggested for the
marine Paleogene on the south of European Russia
(Akhmetiev and Beniamovski, 2003) includes the
complex paleontological substantiation for most for
mations distinguished in the Volga region. Neverthe
less, many stratigraphic problems remain unsolved, as
they are connected with the inadequacy of paleonto
logical investigations and peculiar siliceousterrige
nous sedimentation on the northern margins of the
PeriTethys, the fragmentary state of outcrops, and
low abundance of micropaleontological remains in the
rightbank sections of the Volga River. This work,
aimed at the multidisciplinary study of organicwalled
microphytofossils in one of the most complete sec
tions of the Paleogene in the northern marginal zone
of the CircumCaspian region, offers the opportunity
to solve a series of biostratigraphic and paleogeo
graphic problems. The study is focused on the follow
ing: (1) on tracing the complete succession of the bio
stratigraphic zones, bearing index taxa of microphyto
fossils, and for correlating them with the respective
standard zonations; (2) providing the possibility to
correlate directly in one section the nannoplankton
(an orthostratigraphic group of Paleogene nannofos
sils) and dinocyst zonations in order to determine pre
cisely the age of the deposits in the region; (3) compar
ing dinocyst zones in the CircumCaspian region and
sections of the Volga River right bank, which allows
one to specify the stratigraphic positions of siliceous
terrigenous deposits, whose thickness is considerably
reduced in the rightbank sections; to obtain an insight
into the coordination between the nannoplankton,
dinocyst, and diatom zonations in the same basin of
sedimentation; and to create a solid basis for placing
age constraints on the other fossil groups, including
the molluscan assemblages. In addition, the study of
organicwalled phytoplankton from the Novouzensk
section is prosspective in terms of paleogeographic
interpretations and may elucidate the time spans of the
links of the seas between the northern and eastern cir
cumCaspian basins, the Turgai straight, and the West
Siberian seabasin.
MATERIAL AND METHODS
Dinocysts and nannoplankton have been studied in
84 samples from core section of the reference borehole
Novouzensk No.1, drilled in 1949–1951 on the right
bank of the Bolshoi Uzen River in the vicinity of
Novouzensk town, in the Saratov oblast (Fig. 1). The
drill hole (mouth altitude 30.4 m) is situated in a zone
of Permian salt domes, approximately 100 km away
from the northern edge of the CircumCaspian
depression flank, where the borehole penetrated
through a succession of Paleogene carbonateterrige
nous sediments 526 m thick, deposited in an inter
dome syneclise. In 1995–1996, Musatov (1996) car
ried out an initial study of the nannoplankton. During
the recurrent sampling of 2006, we collected rock
samples for the investigation of dinocysts and nanno
plankton from all lithostratigraphic subdivisions (dur
ing drilling, core recovery corresponded to 10–12 m per
each free fall). At the time of the last sampling, the
retained amount of core samples represented, on aver
age, 40 to 60% of the initially recovered materials, except
for the Lutetian part of the section (the Algai Fm),
where only 1 to 5% of the samples were preserved. We
used the convential procedure of palynologic macera
tion to extract dinocysts from rock samples.
Dinocysts and other organicwalled microfossils
occur practically throughout the section, although
their abundance varies. They characterize all the
Volga R.
SARATOV
Engels
Eruslan R.
Malyi Uzen R.
Bolshoi Irgiz R.
Novouzensk
0306090 km
12
46
°
E
50
°
N
52
°
N
48
°
E
Bolshoi Uzen R.
Novouzensk
reference
section
Fig. 1.
Geographic locality of the Novouzensk reference
section no. 1: (1) section locality, (2) margin of the Cir
cumCaspian syneclise.
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 85
lithostratigraphic units sampled, except for the Algai
Fm, from which the core material was insignificant.
Based on the analyzed composition of the phy
toplankton, we distinguished eight dinocyst zones and
three biostratigraphic units, ranked as “beds with
flora” in the Novouzensk borehole section. The zonal
dinocyst assemblages are designated by the first occur
rence of index species, whereas the “beds” are named
for their dominant taxa. The phytoplankton assem
blages are correlated with the concurrent assemblages
and zones of Paleogene successions in Northwest
Europe, the North Sea, and the European Paleogene
zonation (Heilmann–Clausen, 1985; Heilmann–
Clausen and Costa, 1989; Powell, 1992; Mudge and
Bujak, 2001; Luterbacher et al., 2004).
Calcareous nannoplankton was identified in most
of the samples studied and is characteristic of all for
mations and beds of the section, which are composed
of marl and calcareous rocks; excluding the noncar
bonated samples from the Thanetian Novouzensk Fm
and the basal interval of the Ypresian Bostandyk Fm.
We studied nannoplankton in preparations, made of
rock powder suspended in alcohol, without prelimi
nary enrichment. Eight standard zones (Martini,
1971) and one biostratigraphic unit, ranked as a local
zone, have been distinguished. All zonal subdivisions
have been established in standard definition, in accor
dance with the first and last appearance of index spe
cies. In studying zonal assemblages, we paid attention,
in addition to the appearance or disappearance of
index species, also to the sequence of assemblages and
general changes in their composition.
STRUCTURE OF THE SECTION
Distinguishing formations in the section, we took
into account its original description by Morozova
(1960), investigations by Leonov (1961), Grachev et
al. (1971), and our own observations. Within the depth
interval of 926.0–400.0 m of the Novouzensk borehole
section, the following stratigraphic subdivisions over
lie the white chalk in the upward succession (Fig. 2).
The Paleocene, Danian, and Algai Formation
926.0–917.0 m: marl, greenish gray, compact,
slightly micaceous, with pyrite inclusions; NP2
Cruci
placolithus tenuis
Zone of nannoplankton scale.
917.0–892.0 m: greenish gray, compact, sandy
marl in the lower part of the interval; greenish to light
gray, compact, plastic, calcareous clay (marl?) with
impressions of macrofauna in the upper part.
The Tsyganovo Formation
892.0–856.0 m: basal, black, calcareous, locally
somewhat sandy clay, with impressions of macrofaune
grades upward into sandy clay, highly calcareous,
enclosing abundant glauconite grains, which impart a
dark green tint to the rock.
The Selandian, Syzran Formation
Lower Syzran Subformation.
856.0–789.0 m:
basal, black, opokalike, slightly calcareous clay with
impressions of macrofauna; higher in the interval, the
clay is black, compact, somewhat calcareous, mica
ceous, with fine inercalations of sand, impressions of
macrofauna, and rare laminae of dark gray fine
grained micaceous sandstone.
The Upper Syzran Subformation.
789.0–721.0 m:
basal sandstone, dark gray, calcareous, clayey, fine
grained; higher in the interval, there are dark gray
clays, compact, opokalike, micaceous, sandy, non
calcareous, intercalated with sandstones. The upper
part is composed of intercalated black clays, compact,
plastic, slightly calcareous, micaceous, with local sand
and sandstone laminae and impressions of plant
remains. The interval of 772.0–747.0 m lacks core
samples.
The Paleocene, Thanetian, and Novouzensk Formation
721.0–568.0 m: basal clay, dark gray to black, com
pact, slightly calcareous, plastic, sandy (lenticules and
laminae), with impressions of plant remains, overlain
by quartzglauconite finegrained sand. Higher in the
section, clays are dark gray to black, sandy, micaceous,
noncalcareous, and intercalated with finegrained
sandstone interbeds (up to 3.0m thick), containing
gray to greenish gray glauconite and impressions of
mollusks. Intervals of 635.0–621.0 and 672.0–664.0 m
lack core samples.
The Eocene, Ypresian, and Bostandyk Formation
568.0–405.0 m: in the lower part, interlayering
beds of gray, finegrained, clayey, locally silicified,
quartzglauconite sandstone are intercalated with
dark gray, compact, sandy, micaceous clay containing
impressions of mollusks. The rocks are free of carbon
ate material. Higher in the section, there are gray to
dark green clays, variably calcareous, sandy, thinbed
ded, intercalated with finegrained, micaceous glauc
onite sandstone. The rocks contain impressions of
mollusks, fish scale, and sponge spicules. The dark
green clay occurring higher in the section is more
sandy and calcareous, grading upward into thin marl
laminae.
The Lutetian and Kopterek Formation
405.0–400.0 m: basal finegrained calcareous
sandstone grading upward into greenish compact
sandy marl.
86
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
Series
Stage
Eocene
YpresianThanetian
Paleocene
Danian
Selandian
Lu
Nannoplankton
(Martini, 1971)
Dinocyst zones
North Sea
(Mudge, Bujak,
1994, 2001)
West Europe
(Luterbacher
NP14
NP13
NP12
zones
NP11
NP10
NP9
NP8
NP7
NP6
NP5
NP4
NP3
NP2
NP1
DE3
DE2
DE1
DP6b
DP6a
DP5a
DP4a
DP3a
DP2a
DP5b
DP4b
DP3b
DP1
D9
D8
D7
D6
D5
D4
D3
D2
D1
a
b
c
a
a
a
a
a
a
a
a
b
b
b
b
b
b
b
b
b
c
c
c
Novouzensk reference section
Biostratigraphic subdivision
nannoplankton
Zone NP14 Discoaster
sublodoensis
no specimens
Zone
NP13
Discoaster lodoensis
Zone
NP12
Marthasterites
tribrachiatus
Zone
NP6
Heliolithus
kleinpelli
Zone
NP5
Fasciculithus
tympaniformis
Zone
Neochiasto
zygus
junctus
Zone
NP4
Coccolithus
robustus
Zone
NP3
Chiasmolithus
danicus
Zone
NP2 Cruciplaco
lithus tenuis s. s.
dinocysts
Beds
Areosphaeridium
diktyoplokum
Zone
D8
Dracodinium politum
Charlesdowniea
coleothrypta
Zone
D7c
Dracodinium
varielogitudum
Zone DE1bc Deflandrea
oebisfeldensis
DE1a Beds
Pterospermella spp.
Zone
D5a (DP6b)
Apectodinium augustum
Zone
D4c
Apectodinium
hyperacanthum
Beds
Cerodinium
markovae
Zone
D3b (DP3b)
Isabelidinium?
viborgense
Zone
D3b
Cerodinium
depressum
Zone
D3a
Alterbidinium circulum
unstudied
Wetzeliella coronata
no specimens
et al. 2004)
Formation
,
subformation
Depth, m
Lithology
Samples
Kop
BostandykNovouzensk
Upper Syzran
Lower SyzranTsyganovo
Algai
K
2
m
400
405
414
420
460
475
486
500
523
568
621
635
664
672
721
747
772
789
856
869
892
917
926
1a
1
1b
1c
1d
2
2a
3
4
4a
5
6
7
8
8a
9
10
10a
11
12
13
14
17
19
22
23
25
27
29
31
32
34
35
36
37
38
39
40
41
42
43
44
45
46
47
49
51
52
53
54
55
56
57
58
59
61
63
65
66a
66
67
68
69
70
71
72
73
74
75
76
77
78
terek
tet
123456
789101112
* *
* *
* *
* *
* *
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 87
RESULTS
Dinocysts
Deposits of the Tsyganovo Fm (interval 869.0–
856.0 m) yielded dinocyst assemblage of the
Alter
bidinium circulum
Zone (Heilmann–Clausen, 1985).
The assemblage of 66 taxa includes zonal index species
Spinidinium densispinatum
Stanl.,
Palaeocystodinium
benjamini
Drugg,
P. australinum
(Cooks.),
P. bullifor
mum
Ioann.,
Senegalinium iterlaaense
NohrHans. et
Heil.Claus.,
C. kangiliense
NohrHans. et Heil.
Claus., and
C. diebelii
(Alb.). Dinocysts are dominant
in the assemblage (about 80%). The first Appearance
Datum (FAD) of
Alterbidinium circulum
is achnowl
edged as the Selandian base (Luterbacher et al., 2004).
According to the occurrence of index species and
Spinidinium densispinatum
, the assemblage can be cor
related with the Viborg 1 Zone in Denmark (Heil
mann–Clausen, 1985), the D3a
Alterbidinium circulum
Zone in the standard dinocyst zonation (Luterbacher
et al., 2004), and the
Spinidinium densispinatum
Zone
of the North Sea scale (Powell, 1992). The Selandian
age of the zone is substantiated in the latter two works,
and its stratigraphic position is discussed below.
Rocks from the Lower Syzran Subfm (interval
856.0–772.0 m) and lower part of the Upper Syzran
Subfm (sandstone from interval 789.0–772.0 m) bear
the
Cerodinium depressum
zonal assemblage (Heil
mann–Clausen, 1985). FAD of index species,
Cerod
inium speciosum
(Alb.), and
Impagidinium
sp. 1 Heil.
Claus. are recorded at the base of the interval. Palyno
morphs dominating the assemblage are pollen, spores,
green algae, and acritarchs, whereas dinoflagellate
cysts represent not more than 10%. The assemblage
corresponding to zones Viborg 2 of Denmark (Heil
mann–Clausen, 1985) and D3b
Cerodinium depres
sum
(Luterbacher et al., 2004) is of the Selandian age.
Sediments of the Upper Syzran Subfm (interval
772.0–733.0 m) contain the
Isabelidinium? viborgense
dinocyst assemblage. Characteristic of the interval are
FAD and Last Appearance Datum (LAD) of index
species, LAD
Palaeoperidinium pyrophorum
(Ehren.),
LAD
Palaeocystodinium australinum
(Cooks.), and
FAD
Cerodinium markovae
(Vozzh.). Organicwalled
microphytoplankton represents less than 17% of the
palynological assemblage, dominated by terrestrial
palynomorphs. The assemblage is concurrent to the
following units: Zone D3b, Zone NP5 (part) of the
standard nannoplankton zonation (Luterbacher et al.,
2004), the Selandian zones Viborg 2 and Viborg 3
(part) of Denmark (Heilmann–Clausen, 1985, 1994),
and Zone DP3b of the North Sea scale (Mudge and
Bujak, 2001).
Sediments from the lower third of the Novouzensk
Fm (interval 721.0–635.0 m) yield an impoverished
assemblage of microphytoplankton represented by
A. margarita
(Harl.),
P. minusculum
(Alb.),
C. marko
vae
(Vozzh.),
C. sibiricum
(Vozzh.), and
C. leptoder
mum
(Vozzh.). The transitional interval of 733.0–
721.0 m (top of the Upper Syzran Subfm and
Novouzensk Fm base) is extremely depleted in the
palynomorphs. The interval of 721.0–635.0 m is
termed the
Cerodinium markovae
Beds. Spores and
pollen dominate the informative spectra of the beds.
Abundant but poorly preserved phytoplankton from
Sample 42 is represented by
Cerodinium leptodermum
(Vozzh.),
C. markovae
(Vozzh.), and solitary speci
mens of
A. gippingensis
Jolley. The occurrence of the
last species is characteristic of Zone DP5ab in the
North Sea (Mudge and Bujak, 2001). The appearance
of
Alisocysta margarita
is confined to the Thanetian
base or to the topmost level of the Selandian (Hel
mannClausen, 1985, 1994; Powell et al., 1996). How
ever, we suggest the early Thanetian age of the beds
according to the dominance of endemic
Cerodinium
forms and the low diversity of the assemblage in the
upper part of the interval.
Based on the index species FAD, the
Apectodinium
hyperacanthum
dinocyst zone is established higher in
the sediments of the Novouzensk Fm (interval 621.0–
568.0 m). It is correlative with Zone D4c of the stan
dard zonation (Luterbacher et al., 2004) and Zone
DP6a of the North Sea (Mudge and Bujak, 2001),
being therefore late Thanetian in age.
The Bostandyk Fm spans several dinocyst zones of
the Ypresian. The interval of sandstones (568.0–523.0 m)
Fig. 2.
Lithostratigraphy, nannoplankton and dinocyst zonation of the Novouzensk reference section: (1) chalk, (2) marl, (3) clay,
(4) opokalike clay, (5) sandstone, (6) lentils and interlayers of sand and aleurite, (7) glauconite, (8) calcareous impurity,
(9) impressions of macrofauna and plant remains, (10) hiatus, (11) section interval lacking core samples, (12) intervals of stan
dard zonation missing from the section.
Zones (species LAD) of the North Sea zonation (Mudge and Bujak, 1994, 2001): DP1,
Senoniasphaera inornata
; DP2a,
Aliso
cysta reticulata
; DP2b,
Spiniferites “magnificus”
; DP3a,
Thalassiphora
cf.
delicata
; DP3b,
Isabelidinium? viborgense
; DP4a,
Palaeoperidinium
pyrophorum (abundance)
; DP4b,
Palaeocystodinium
cf.
australinum
; DP5a,
Areoligera gippingensis
(abun
dance); DP5b,
Alisocysta margarita, Areoligera gippingensis
; DP6a,
Apectodinium
spp. (abundance); DP6b,
Apectodinium augus
tum
(FAD and LAD); DE1a,
Cerodinium wardenense, Leiosphaeridia
spp.; DE1bc,
Hystrichosphaeridium tubiferum, Deflandrea
oebisfeldensis
(abundance)
; DE2a,
Dracodinium solidum
; DE2b,
Dracodinium condylos
; DE2c,
Dracodinium varielongitudum
; D3,
Eatonicysta ursulae.
Units (species FAD) of the standard zonation (Luterbacher et al., 2004): D3a,
Alterbidinium circulum
; D3b,
Cerodinium depres
sum
; D4a,
Alisocysta margarita
; D4b,
Areoligera gippingensis
; D4c,
Apectodinium homomorphum
; D5a,
Apectodinium augustum
;
D5b, LAD
Phelodinium magnificum
; D6a,
Wetzeliella astra
; D6b,
Wetzeliella meckelfeldensis
; D7a,
Dracodinium simile
; D7b,
Dracodinium solidum
; D7c,
Dracodinium varielongitudum
; D8a,
Charlesdowniea coleothrypta
; D8b,
Ochetodinium romanum
; D8c,
Charlesdowniea
aff.
clathrata
; D9a,
Areosphaeridium diktyoplokum
; D9b,
Dracodinium pachydermum.
88
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
with dinocyst assembalge and FAD
Apectodinium
augustum
is correlative with zones D5a (Luterbacher
et al., 2004) and DP6b (Mudge and Bujak, 1996,
2001); the FAD of the designated species is concurrent
with the Paleocene–Eocene Temperature Maximum
(PETM) and the Paleocene–Eocene boundary (Bujak
and Brinkhuis, 1998).
The
Deflandrea oebisfeldensis
assemblage, charac
terizing noncalcareous clay of the Bostandyk Fm
(interval 500.0–486.0 m), is typical of Zone D5b in
the standard zonation (Luterbacher et al., 2004) and
Zone DE1bc in the North Sea sediments (Mudge and
Bujak, 2001). The assemblage of the early Ypresian
age, exemplifying the high productivity of the
dinoflagellate cysts, is dominated by index species
associated with single specimens of
Cerodinium specio
sum
subsp.
glabrum
(Gocht),
Spiniferites
spp., and
Cordosphaeridium
sp. The
Dracodinium varielongitu
dum
dinocyst assemblage, identified in the interval
486.0–460.0 m, includes
W. meckelfeldensis
Gocht,
Dracodinium simile
(Eis.),
D. solidum
Gocht, and
D. condylos
(Will. et Down.). The index species FAD
motivated the recognition of the standard dinocyst
Zone D7c in the Paleogene scale (Luterbacher et al.,
2004), which is correlative with Zone DE2c in the sed
iments of the North Sea (Mudge and Bujak, 1994) and
corresponds in age to the middle Ypresian s.s.
The interval 460.0–414.0 m is concurrent with the
standard dinoflagellate Zone D8 (Heilmann–
Clausen, Costa, 1989; Luterbacher et al., 2004), since
it yields microphytoplankton assemblage characteriz
ing FAD
Dracodinium politum
Bujak et al., FAD
Pen
tadinium laticinctum
Gerl., and FAD
W. samlandica
(Eis.) at the interval base. Associated species are
Char
lesdowniea coleothrypta
(Will. et Down.),
Heslertonia
heslertonense
(Neale et Sarj.),
Samlandia chlamy
dophora
Eis., and
Heteraulacacysta leptalea
Eaton.
The whole association of the species is termed the
Dracodinium politum–Charlesdowniea coleothrypta
assemblage. Zone D8, correlated with Zone DE2 of
the North Sea (Bujak and Mudge, 1994), is concur
rent with the nannoplankton zones NP12 (part)–
NP13 (part). The dinocyst assemblage of the zone is of
the middle Ypressian age.
In the upper interval of the section (414.0–400.0 m),
we distinguished the
Wetzeliella coronata–
Areosphaeridium diktyoplokum
Beds of dinocysts.
Characteristic of the beds are the FAD
A. diktyoplo
kum
; this taxon is found in association with
Wetzeliella
ovalis,
W.
aff.
articulata
sensu De Con., and two
endemic taxa:
Wetzeliella coronata
(Vozzh.) and
D. apiculiformis
Andr.Grig. et Savitz. Species of the
assemblage are known from zones D9 (Luterbacher
et al., 2004) and DE3 (Bujak, Mudge, 1994), which
are correlative with nannoplankton zones NP13
(part)–NP14 (part). The stratigraphic range of the
assemblage corresponds to the upper Ypresian–lower
Lutetian. The distribution of the principal taxa con
sidered above is illustrated in Fig. 3.
Nannoplankton
In the lower part of the Algai Fm (926.0–917.0 m),
we identified the
Cruciplacolithus tenuis
s.s. assem
blage of the lower Danian Zone NP2 (CP1b). Species
of the assemblage are
C. tenuis
Hay et Mohler,
C. pri
mus
P. N ie l se n,
Zygodiscus sigmoides
Br. et Sull.,
Eric
sonia subpertusa
Hay et Mohler,
Marcalius inversus
Br.
et Mart., and
Biantolithus sparsus
Br. et Mart.; the lat
ter occurring as single specimens. Marls from the Algai
Fm upper part, where FAD
Chiasmolithus danicus
Hay
et Mohler is recorded at the base, yield nannoplank
ton, characterizing Zone NP3
Chiasmolithus danicus.
The composition of other species is practically identi
cal to that in Zone NP2. Zone NP3 corresponds in age
to the middle Danian (Martini, 1971).
In the rocks of the Tsyganovo Fm (892.0–856.0
m), we identified the nannoplankton assemblage,
characterizing the lower part of Zone NP4 (CP3)
Coc
colithus robustus
(equivalent of Zone NP4
Ellipsolithus
macellus
) of the standard nannoplankton zonation
(Martini, 1971; Okada and Bukry, 1980). The distinc
tive features of the assemblage are as follows: the
appearance of abundant
Coccolithus robustus
Bukry,
C.
eopelagicus
Br. et Sull.,
C. cavus
Hay et Mohler, and
Neochiastozygus perfectus
P.N.; greater abundance
and larger sizes of
Chiasmolithus danicus
Hay et
Mohler,
Cruciplacolithus tenuis
Hay et Mohler, and
Ericsonia subpertusa
Hay et Mohler; and a higher per
centage of
Micrantholithus
sp. The comparable assem
blages have been macerated from the lower Paleocene
deposits of the Northern Caucasus (Muzylev, 1980).
The black opokalike clay of the Lower Syzran
Subfm (856.0–789.0 m) bears nannoplankton attrib
uted to the
Neochiastozygus junctus
local zone (upper
part of Zone NP4
Coccolithus robustus
). Species
C. tenuis
Hay et Mohler,
Coccolithus robustus
Bukry,
C. cavus
Hay et Mohler, and
N. perfectus
P.N. are
considerably less abundant in this zone, where abun
dant forms of
Neochiastozygus junctus
P.N. represent
newcomers. The first rare specimens of
Chiasmolithus
consuetus
Hay et Mohler are identified in the upper
part of the zone.
The index species
Ellipsolithus macellus
Sull., char
acteristic of the respective interval in the Paleogene
sections in Western Europe and oceanic sediments, is
rare in the studied rocks. Single
Ellipsolithus distichus
Sull., sporadic
Toveius
sp. and
Marcalius inversus
Br. et
Mart., and rare
Biantolithus sparsus
Br. et Mart.,
Tho
racosphaera
sp.,
Braarudosphaera bigelowii
(Gran et
Braar.), and
Goniolithus fluckigeri
Defl. occur near the
top of the
Neochiastozygus junctus
local zone, where
the composition of the nannoplankton assemblage is
less diverse in general. The assemblage under consid
eration can be attributed without doubt to the upper
part of Zone NP4
Coccolithus robustus
s.l. According
to acknowledged stratigraphic charts and nanno
plankton zonations (Martini, 1971; Luterbacher et al.,
2004; etc.), this zone in its broad interpretation spans
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 89
Series
Stage
Zone, beds
Formation
Samples
Thanetian
Cerodinium markovae
Novouzensk
I.?viborgense
Upper Syzran
Paleocene
Selandian
Cerodinium depressum
Lower Syzran
Danian
Tsyganovo
Alterbidinium circulum
Microphytoplankton species
Spinidinium densispinatum
Spinidinium
spp.
Alterbidinium circulum
Laciniadinium
sp.1
Senegalinium obscurum
Senegalinium
spp.
Palaeocystodinium benjamini
Cladopyxidium saeptum
Cerodinium diebelii
Cerodinium kangiliense
Cerodinium striatum
Senegalinium iterlaaense
Tanyosphaeridium xanthiopyxides
Alisocysta
sp. 1 Heil.Clausen
Impagidinium
sp. 1
Cerodinium markovae
Alisocysta margarita
Cerodinium sibiricum
Cerodinium leptodermum
Areoligera gippingensis
Alterbidinium
spp.
Senegalinium
dilwynense
Senegalinium
microspinosum
Palaeocystodinium
australinum
Palaeocystodinium
bulliformum
Fibradinium
annetorpense
Fromea
laevigata
Hafniasphaera
septata
Palaeotetradinium minusculum
Trigonopyxidia
ginella
Palaeoperidinium
pyrophorum
Rottnestia
borusicca
Cerodinium
speciosum
Cerodinium
depressum
Paucilobimorpha
apiculata
Palaeocystodinium
golzowense
/
P. lidiae
Isabelidinium? viborgense
38
39
40
41
42
43
44
45
46
47
49
50
51
52
53
54
55
56
57
58
59
61
63
65
66а
66
67
68
69
71
72
73
Fig. 3.
Distribution ranges of principal microphytoplankton taxa (dinocysts, green algae, acritarchs) in the Novouzensk section.
Heil.Claus.
90
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
Thanetian
Novouzensk
Paleocene
Microphytoplankton species
Eocene LutetianYpresian
Wetzeliella
coronata
Areosph
.
dikyoplokum
Kopterek
D. politum
Ch. coleothrypta
D. varielongitud.
D
.
oebisfeldensisPterospermella
sp.
Apectodinium
augustumA
.
hyperacanthum
Bostandyk
Cerodinium speciosum subsp. glabrum
Deflandrea oebisfeldensis
Apectodinium homomorphum
Apectodinium hyperacanthum
Apectodinium augustum
Apectodinium parvum
Apectodinium quinquelatum
Wilsonidium pechoricum
Deflandrea cornummamillata
Fibrocysta lappacea
Heteraulacacysta pustulata
Cerodinium wardenense
Pterospermella
spp.
Wetzeliella meckelfeldensis
Dracodinium simile
D
racodinium solidum
Dracodinium varielongitudum
Deflandrea phosphoritica
Dracodinium condylos
Charlesdowniea crassiramosa
Kallosphaeridium brevibarbatum
Heslertonia heslertonensis
Cordosphaeridium gracile
Pentadinium laticinctum
Dracodinium politum
Wetzeliella samlandica
Areoligera medusettiformis
Samlandia chlamydophora
Areosphaeridium michoudii
Ochetodinium romanum
Charlesdowniea coleothrypta
Dracodinium pachydermum
Dracodinium rhomboideum
Cerebrocysta bartonensis
Heteraulacacysta leptalea
Charlesdowniea
aff
. clathrata
R. glabrum
subsp
. crassithecum
Areosphaeridium diktyoplokum
Wetzeliella coronata
Wilsonidium echinosuturatum
Deflandrea apiculiformis
Wetzeliella ovalis
Wetzeliella
aff.
articulata
Content of taxa:
1
specimen
< 10%
> 10%
> 20%
no core
samples
1
1b
1c
1d
2
2a
3
4
4a
4b
5
6
6a
6b
7
8
8a
9
10
10a
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
27a
28
29
30
30a
31
32
34
35
36
37
Series
Stage
Zone, beds
Formation
Samples
Fig. 3.
Contd.
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 91
the upper part of the Danian and lower part of the
Selandian. At the same time, the considered section
interval can be attributed to the Selandian, as it cer
tainly belongs to the upper part of Zone NP4, because
of the considerable changes in the species composition
of the nannoplankton.
The Upper Syzran Subfm (789.0–721.0 m) bears
nannoplankton assemblage comparable with that of
Zone NP5 (CP4)
Fasciculithus tympaniformis
of the
standard zonation. The comparatively abundant spe
cies of the assemblage are
Fasciculithus tympaniformis
Hay et Mohler,
F. magnus
Bukry et Perc.,
F. involutus
Br. et Sull.,
Coccolithus robustus
Bukry,
C. eopelagicus
Br. et Sull.,
C. cavus
Hay et Mohler,
Neochiastozygus
junctus
P.N.,
N. concinnus
P.N.,
Cruciplacolithus
tenuis
Hay et Mohler,
C. primus
P.N.,
Chiasmolithus
danicus
Hay et Mohler,
Zygodiscus sigmoides
Br. et
Sull., and
Micrantolithus
sp. Abundant
Ch. bidens
Hay
et Mohler appear in the upper part of the zone. The
assemblage of these taxa can be attributed for sure to
Zone NP5
Fasciculithus tympaniformis
of the upper
Selandian.
The assemblage typical of Zone NP6 (CP5)
Heli
olithus kleinpelli
is identified in the lower part of the
Novouzensk Fm (interval 721–686 m). Characteristic
of the assemblage are FAD
Heliolithus kleinpelli
Sull.
and insignificant abundance rates of
F. tympaniformis
Hay et Mohler,
C. eopelagicus
Br. et Sull.,
C. cavus
Hay
et Mohler,
Cruciplacolithus tenuis
Hay et Mohler,
Ch. bidens
Hay et Mohler, and
Neochiastozygus con
cinnus
P.N. In the higher section interval about
200m thick, calcareous nannoplankton has not been
discovered.
The nannoplankton assemblage of standard Zone
NP12 (CP10)
Marthasterites tribrachiatus
is identified
in the middle part of the Bostandyk Fm (interval
475.0–420.0 m). Species occurring in the assemblage
are
M. tribrachiatus
Defl. (
Tribrachiatus orthostylus
),
Discoaster lodoensis
Br. et Riedel,
D. binodosus
Mar
tini,
D. kuepperi
Str.,
Imperiaster obscurus
Martini,
Neococcolithus dubius
Black, and
Neochiastozygus dis
tentus
P.Nielsen. Species
Zygrhablithus bijugatus
(Defl. et Fert),
Ch. grandis
(Bram. et Riedel), and
Dis
coaster barbadiensis
Tan Sin Hok appear in the upper
part of the interval. The distribution of the principal
taxa is illustrated in Fig. 4.
The nannoplankton assemblage of Zone NP13
(CP11)
Discoaster lodoensis
, the terminal one in the
Ypresian of the general stratigraphic scale, is macer
ated from the upper part of the Bostandyk Fm (interval
420.0–414.0 m). Representing the assemblage are
abundant larger and smaller forms
D. lodoensis
Br. et
Riedel and
B. bigelowii
(Gran et Braar.), along with
very large species
I. obscurus
Martini,
D. kuepperi
Stradner, and
Ch. armatus
P.Nielsen. New species
appearing in abundance are
Toweius gammation
(Br. et
Sull.),
T. crassus
(Br. et Sull.),
Lithostromation opero
sum
(Defl.),
Cruciplacolithus delus
(Br. et Sull.),
Heli
cosphaera lophota
Br. Et Sull.,
Pontosphaera multipora
(Kamptner),
Discoaster binodosus hirundinus
Martini,
D. nonaradiatus
Klumpp, and
D. gemmifer
Str.
The assemblage of Zone NP14 (CP12)
Discoaster
sublodoensis
characterizes the Kopterek Fm (interval
405.0–400.0 m). It includes most taxa of the previous
zone, along with the first appearance of species
D. sub
lodoensis
Br. et Sull.,
D. wemmelensis
Ach. et Strad.,
Chiasmolithus expansus
(Br. et Sull.), and
Rhab
dosphaera procera
Mart. Index species
Rh. inflata
Br. et Sull., occurring in the assemblage, suggests that
the respective interval of the section is correlative with
the
Rhabdosphaera inflata
Subzone and corresponds
to the upper part of the
Discoaster sublodoensis
Zone.
In species composition (nearly 70 taxa), the assem
blages of zones NP12–NP14 insignificantly differ
from the concurrent assemblages of southern regions,
except for species diversity of genera
Rhabdosphaera,
Pontosphaera
, and
Micrantolithus.
Stratigraphic
ranges of nannoplankton and dinocyst biostrati
graphic units are shown in Fig. 2.
AGE SUBSTANTIATION
AND CORRELATION OF DEPOSITS
In the Novouzensk section, the paleontological
characterization of the
Algai Fm
(926.0–892.0 m) is
known based on nannoplankton only. Assemblages of
zones NP2 and NP3 from the marly sediments of the
formation differ insignificantly from comparable
assemblages known in other regions of the world. The
only distinction is the rare occurrence of
Biantolithus
sparsus
Br. et Mart. Comparatively abundant
Braaru
dosphaera bigelowii
(Gran et Braar.) occur in the upper
part of Zone NP3. Data on nannoplankton imply the
early–middle Danian age of the formation. As Zone
NP1
Marcalius inversus
(CP1a
Cruciplacolithus pri
mus
) is missing at the base of the formation section, we
consider this fact as indicative of a break in sedimenta
tion, which is of regional rank according to some indi
cations.
The
Tsygano vo Fm
(892.0–856.0 m) yields nanno
plankton, characterizing the lower part of Zone NP4
Coccolithus robustus
(NP4
Ellipsolithus macellus
). At
the same level, FAD
Neochiastozygus perfectus
P.Nielsen is recorded. The increased abundance of all
species occurring in the underlying deposits and the
appearance of
C. robustus
Bukry and
N. perfectus
P.Nielsen, along with larger
C. eopelagicus
Br. et Sull.
are the main distinctive features of the assemblage. An
assemblage of nannoplankton comparable with that of
the Tsyganovo Fm was found on the right bank of the
Volga River close to the Belogrodnya village (Musatov
and Khristenko, 2004).
The
Alterbidinium circulum
zonal assemblage of
dinocysts, characterizing sediments in the upper part
of the Tsyganovo Fm was first described by Heil
mann—Clausen, who discovered it at the top of the
Danian limestones (Zone Viborg 1) in borehole sec
92
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
400
405
414
420
460
475
486
500
523
568
621
635
664
672
721
747
772
789
856
869
892
917
926
1a
1
1b
1c
1d
2
2a
3
4
4a
5
6
7
8
8a
9
10
10a
11
12
13
14
17
19
22
23
25
27
29
31
32
34
35
36
37
38
39
40
41
42
43
44
45
46
47
49
51
52
53
54
55
56
57
58
59
61
63
65
66a
66
67
68
69
71
72
73
74
75
76
77
78
4b
6a
6b
50
48
31a
30
30a
28
27a
26
24
20
21
15
16
18
D.sublo
Disco
Martasterites
tribrachiatus
Heliolithus
kleinpelli
Fasciciculithus
tympaniformis
Coccolithus robustus
Neochiastozygus
Chiasm.
danicus
Cruc.
tenuis
Cruciplacolithus primus
Cruciplacolithus tenuis
Marcalius inversus
Zygodiscus sigmoides
Ericsonia cava
Ericsonia subpertusa
Chiasmolithus danicus
Braarudosphaera bigelowii
Biantolithus sparsus
Coccolithus robustus
Coccolithus eopelagicus
Neochiastozygus perfectus
Neochiastozygus junctus
Ellipsolithus macellus
Ellipsolithus distichus
Fasciculithus tympaniformis
Fasciculithus billii
Chiasmolithus bidens
Heliolithus kleinpelli
Cruciplacolithus frequens
Coccolithus eopelagicus
Chiasmolithus bidens
Marthasterites tribrachiatus
Imperiaster obscurus
Discoaser lodoensis
Neococcolithus dubius
Sphenolithus radians
Chiasmolithus solitus
Discoaster kuepperi
Helicosphaera seminulum
Plagozygus sigmoidalis
Chiasmolithus grandis
Discoaster barbadiensis
Lithostromation operosum
Toweius gammation
Cruciplacolithus delus
Pontosphaera punctosa
Helicosphaera lophota
Rh. perlonga, Rh. vitrea
Pontosphaeara multipora
Rhabdosphaera creber
Toweius crassus
Discoaster binodosus
Lithostromation reniformis
Discoaster sublodoensis
Discoaster wemmelensis
Chiasmolithus expansus
Rhabdosphaeara inflata
Rhabdosphaeara morionum
Nannotetrina cristata
lodoensis
doensis
aster
junctus
Thanetian
Paleocene
Danian Selandian
Upper Syzran Novouzensk
Lower Syzran
Algai novo
Tsyga
No nannoplankton
Series
Eocene
Ypresian
Lute
Formation
Depth, m
Lithology
Bostandyk
Stage
Zone
Nannoplankton species
No nannoplankton
No nannoplankton
Kopterek
Fig. 4.
Distribution ranges of principal nannoplankton taxa in the Novouzensk reference section (symbols for lithology as in Fig. 2).
tian
Samples
No zones
* *
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 93
tion Viborg 1, which is the Danian–Selandian strato
type in Denmark, correlated indirectly with the nan
noplankton zones NP4–NP5 (Heilmann–Clausen,
1985). In this section, Danian limestones are enriched
in small peridinoid cysts, abundant among which are
Spinidinium
forms (
S. densispinatum
inclusive) and
Alterbidinium circulum
(Heilmann–Clausen, 1985).
Both taxa do not occur in Zone Viborg 2 of the Kerte
minde Fm (Heilmann–Clausen, 1985). In the North
Sea zonation, Powell (1992) designated Zone Viborg 1
as the
Spinidinium densispinatum
Zone at the Thane
tian (now Selandian) base and correlated it with the
nannoplankton Zone NP5.
In a polemic, Heilmann–Clausen remarked that
the
Spinidinium densispinatum
species has not been
found in the standard Zone NP5, being characteristic
of local nannoplankton zones S1 + S2, whose correla
tion with the zonation by Martini (1971) is problem
atic, because index species of zones NP4 and NP5 do
not occur in Denmark (Heilmann–Clausen, 1994). In
his opinion, the assemblage of Zone Viborg 1 is of the
Danian age (Heilmann–Clausen, 1994), whereas the
Selandian interval begins with Zone Viborg 2 (
Cerod
inium speciosum
Zone in the zonation by Powell) rec
ognized in the Kerteminde Fm. In the borehole sec
tion Viborg 1, this formation overlies the Danian lime
stones, with a basal break in sedimentation. The
implication is that the stratigraphic position assem
blage, including two species of the late Danian, the
presumable markers of the Selandian base (Powell,
1992; Luterbacher et al., 2004), is problematic. In the
section of the Novouzensk borehole, the
Alterbidinium
circulum
zonal assemblage of dinocysts is associated,
as we established, with the nannoplankton character
izing the lower part of Zone NP4
Coccolithus robustus
(Fig. 2). Consequently, the
Alterbidinium circulum
dinocyst zone is most likely at the stratigraphic level of
the upper Danian.
The Zumaia section, a new candidate for the stra
totype of the Selandian and Danian–Selandian
boundary, is in the Biscay Bay of Spain. It is composed
of bathyal sediments containing different groups of
calcareous plankton, and the boundary in question is
defined at the base of the red marl interlayer (Itzurun
Fm) in the upper part of nannoplankton Zone NP4.
The Danian–Zelandian boundary in the Zumaia sec
tion crowns the Danian cycle of sedimentation (lime
stones) and marks a clear change in the lithologic
composition of the rocks (
Proposal
…, 2007). Taking
into consideration the composition and distribution of
nannoplankton and dinocyst assemblages, in addition
to the sharp replacement of carbonate sediments
(Tsyganovo Fm) by cherty rocks of the Syzran Fm, we
can conclude that events characterizing the Danian–
Selandian boundary are recorded in the Novouzensk
section across the boundary between the Tsyganovo
and Syzran formations. Thus, the Tsyganovo Fm that
yields the nannoplankton of Zone NP4
Coccolithus
robustus
and dinocysts of the
Alterbidinium circulum
should be dated as the late Danian in age.
The stratigraphic interval of the formation is cor
relative with the Upper Talitsa Subfm, whose sedi
ments are widespread near the Urals in West Siberia
and bear dinocysts of the
Alterbidinium circulum
assemblage (Vasil’eva et al., 2001). Part of the Thyra
Fm in North Greenland and the Equalulik Fm in West
Greenland are very likely of the same stratigraphic
interval (Lyck and Stemmerik, 2000; NøhrHansen
and Heilmann–Clausen, 2001). However, both for
mations of Greenland contain a high percentage of
redeposited palynological material.
The
Lower Syzran Subfm
bears nannoplankton of
the
N. junctus
local zone (upper part of Zone NP4).
An insignificant admixture of the redeposited Creta
ceous species gives evidence of the proximity of the
provenance for carbonate material derived from Cre
taceous deposits. The
Neochiastozygus junctus
local
zone, distinguished in the section, clarifies the interre
gional correlations. In particular, Sidor (1992) identi
fied the
Neochiastozygus junctus
local zone inside the
Coccolithus robustus
Zone of the Kuzbak Fm in the
East CircumCaspian region. Muzylev (1980) pointed
out the considerable variations in composition of nan
noplankton assemblages within Zone NP4 of the
Northern Caucasus.
Dinocysts of the
Cerodinium depressum
Zone iden
tified in sediments of the Lower Syzran Subfm and at
the base of the Upper Syzran Subfm (interval 856.0–
781.0 m) are of comparatively low diversity, and terres
trial palynomorphs dominate in the respective zonal
assemblage, which lacks signs of cardinal composi
tional changes, as compared to previous ones. The
lower boundary of the zone is defined at the appear
ance datum of zonal species
Cerodinium depressum
(depth 830.0 m) and FAD
Cerodinium speciosum
,
which occur as single specimens. The content of
Spinidinium densispinatum
is comparatively high in the
basal part of the interval and sharply lower between
812.0 and 803.0 m. In sediments of the Novouzensk
Fm, this taxon is rare. Species
Senegalinium iter
laaense
steadily occurs at the stratigraphic level under
consideration, and the upper boundary of its strati
graphic range corresponds in West Greenland to the
top of Zone NP4 (NøhrHansen and Heilmann–
Clausen, 2001). In the section of the Novouzensk
borehole, the
C. depressum
assemblage spans the inter
val of nannoplankton zones NP4 (part)–NP5 (part).
The above dinocyst assemblage is comparable in
general with the assemblage from Zone Viborg 2 of
section Viborg 1 in Denmark, although
Spinidinium
forms practically do not occur here (Heilmann–
Clausen, 1985). According to the cited work, Zone
Viborg 2 corresponds to the upper intervals of the Ker
teminde Fm. Species
Spinidinium densispinatum
are
known from the Svewjstrup section of the Selandian in
Denmark and from the basal Selandian of southern
Sweden, i.e., from sediments of the earliest Selandian
94
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
(Heilmann–Clausen, 1985). In addition to this fact,
we observed dinocysts in samples from the Lellinge
Greensand, Vestre
Cosv
æ
sk in
Copenhagen, which
were kindly donated for examination by D.P. Naidin.
Spinidinium densispinatum, S. echinoideum
, and
S. uncinatum
represent up to 50% of the dinocyst
assemblage from the samples (Vasil’eva et al., 2001).
The assemblage also includes
Cerodinium speciosum,
C. depressum, C. kangiliense
, and
Paleocystodinium
austalinum
, but lacks
A. circulum.
The
Cerodinium
depressum
assemplage of the CircumCaspian region
is in age an analog of the assemblage from Zone D3b
in the standard dinocyst zonation (Luterbacher et al.,
2004) and from Zone P3a in the sediments of the
North Sea (Mudge and Bujak, 1996). The
Cerodinium
depressum
Zone corresponds in age to the Selandian,
including the earliest epoch of the stage. Hence, we
argue for the early Selandian age of the Lower Syzran
Subfm, which bears the nannoplankton characteristic
of the upper part of Zone NP4
Coccolithus robustus
(
Neochiastizygus junctus
local zone) and the dinocysts
of the
Cerodinium depressum
Zone.
Deposits of the
Upper Syzran Subfm
contain the
nannoplankton of Zone NP5 (CP4)
Fasciculithus tym
paniformis
, whose characteristic features are the
appearance of the index species and a sharply
decreased abundance of most species occurring in pre
vious zones. The zonal assemblage is of low diversity,
represented predominantly by cosmopolitan species
C. robustus
Bukry,
C. eopelagicus
Br. et Sull., and
C. cavus
Hay et Mohler, which occur in association
with subordinate
N. concinnus
P.N. and
Zygodiscus
sigmoides
Br. et Sull. Index species
F. tympaniformis
Hay et Mohler and associated
F. magnus
Bukry et
Perc. and
F. involutus
Br. et Sull. are the usual compo
nents of the assemblage, which can be confidently
attributed to Zone NP5. In the lower part of the zone,
taxa of the Late Cretaceous are recorded. The cocco
lithophorids are most abundant near the top of the
Upper Syzran Subfm.
Chiasmolithus bidens
Hay et
Mohler appears at the same level. Despite the low
diversity of the species, the assemblage is strongly cor
related with the coeval zonal assemblages from many
regions of the world.
The
Isabelidinium? viborgense
zonal assemblage of
dinocysts from sediments of the Upper Syzran Subfm
(interval 772.0–721.0 m) is very close to the previous
one, although it is more diverse in taxonomic compo
sition and characterizes the last appearance in the sec
tion of typical Selandian taxa: LAD
C. striatum, C. spe
ciosum, P. pyrophorum, P. australinum, I.? viborgense,
F. annetorpense
, and FAD
Cerodinium markovae.
The
assemblage is comparable with that from the upper
part of Zone Viborg 2 in section Viborg 1 of Denmark
(Heilmann–Clausen, 1985, 1994). According to the
standard dinocyst zonation, the top interval of Zone
D3b (Luterbacher et al., 2004) spans part of the nan
noplankton Zone NP5
Fasciculithus tympaniformis
,
which is well consistent with the results obtained for
the Novouzensk section. In the North Sea zonation,
Zone DP3b with LAD
Isabelidinium? viborgense
also
corresponds to part of the nannoplankton Zone NP5
(Mudge and Bujak, 1996). Hence, the Upper Syzran
Subfm corresponds in range to the nannoplankton
Zone NP5
Fasciculithus tympaniformis
and the
Cerod
inium depressum
(lower part of subfmation) and
Isabe
lidinium? viborgense
zones of the dinocyst scale.
According to our assessment, deposits of the subfor
mation are middle Selandian in age.
Integrated zones
Alterbidinium circulum, Cerodin
ium depressum
, and
Isabelidinium? viborgense
of the
Novouzensk section span part of the
Cerodinium spe
ciosum
in the zonation suggested by Andreeva–Grig
orovich (1991) for the CIS southern regions. In that
zonation, the
Cerodinium speciosum
Zone corresponds
to the diapason of the nannoplankton zones NP4–
NP7 (part). Based on the dinocyst zones, the Upper
Syzran Subfm can be correlated with part of the Talitsa
Fm in the North Turgai and the Kurgan regions of the
TransUrals, where the
Isabelidinium? viborgense
Zone was also established (Vasil’eva et al., 2001). The
correlation between this stratigraphic interval and
deposits on the right bank of the Volga River is prob
lematic.
The nannoplankton assemblage of the
Novouzensk
Fm
is represented by several species occurring in Zone
NP6, including its index species. The
Cruciplacolithus
frequens
(P.N.) Romein appears inside the zone.
Upward in the section, the diversity of the assemblage
gradually decreases, and then the nannoplankton dis
appears completely in the interval of 696.0–698.0 m.
The presence of index species in the assemblage and
characteristic changes in its taxonomic composition
doubtless suggest a correlation of the respective sec
tion interval with Zone NP6, i.e., with the earliest
Thanetian.
Deposits of the Novouzensk Fm yield dinocysts of
the
Cerodinium markovae
Beds. Specimens of acri
tarchs and green algae are common representatives of
palynomorphs from the beds. As the dinocyst assem
blage is lacking
P. pyrophorum
and
C. striatum
, but the
C. medcalfii
and
A. margarita
, are present, it can be
correlated with Zone Viborg 4 of the Holmehus Fm in
Denmark. Heilmann–Clausen (1985) noted that
samples from this zone either contain sparse
dinoflagellate cysts, or are completely noninformative.
Nevertheless, the occurrence of
C. medcalfii
and
A. margarita
suggest the zone’s correlation with the
lower Landenian in the Gelinden Marl (Heersian
Stage) of Belgium (SchumacherLambry, 1978) and
with the lower Thanetian of the Pegwell Bay section in
South England (Powell et al., 1996). Zone Viborg 4,
distinguished by Heilmann—Clausen, is correlated
with the
Alisocysta margarita
Biochron in the biozona
tion suggested by Powell (1992) for sediments of the
North Sea and can be concurrent with nannoplankton
zones NP6–NP8 (Heilmann–Clausen, 1994), i.e.,
with the Sealandian top and the conjoined part of the
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 95
Thanetian. In the Novouzensk borehole section, the
lower distribution limit of the
Cerodinium markovae
Beds (FAD
Alisocysta margarita
) is established at the
level of occurrence of nannoplankton, characteristic
of Zone NP6
Heliolithus kleinpelli
, and this is confir
mation of the above correlation. In the Lower Volga
region, presumable analogs of the beds are sediments
of the Kamyshin Fm, recovered by Borehole 28
(Dubovka site) and containing the
Alisocysta margarita
assemblage (Aleksandrova, 2001). In the North Turgai
region, the dinocyst assemblage with
Alisocysta marga
rita
and
Areoligera gippingensis
is known from the
Sokolovo Sequence (Vasil’eva, 2000; Iakovleva and
Kulkova, 2003).
We note that dinocysts of the
Cerodinium markovae
Beds occur in the Novouzensk section at the higher
stratigraphic level as compared to the
Isabelidinium?
viborgense
dinocyst assemblage of the middle Selan
dian. This succession of biostratigraphic markers sug
gests a considerable stratigraphic hiatus spanning the
upper Selandian, because the zone with LAD
Palaeo
peridinium pyrophorum
(abundance), an age analog of
the upper part in Zone Viborg 3 (Heilmann–Clausen,
1994) and of the North Sea Zone DP4b (Mudge and
Bujak, 2001), is missing from the section. The hiatus
in the Novouzensk section spans most likely the upper
Selandian and corresponds in range to the upper half
of Zone NP5
Fasciculithus tympaniformis
and the basal
(Selandian) interval of Zone NP6
Heliolithus riedelli.
From the viewpoint of lithology, clay in the respective
interval near the top of the Upper Syzran Subfm is
considerably enriched in clastic material. Accordingly,
the Novouzensk Fm of the early Thanetian rests most
likely with a hiatus on the eroded top of the Upper
Syzran deposits (Fig. 2).
The
Apectodinium hyperacanthum
zonal assem
blage macerated from the upper half of the
Novouzensk Fm includes, in addition to index spe
cies,
Apectodinium
homomorphum, Deflandrea oebi
sfeldensis
, and
Cerodinium speciosum
subsp.
glabrum.
Age analogs of the respective section interval are Zone
Viborg 5 in section Viborg 1 of Denmark (Heilmann–
Clausen, 1985, 1994), Zone
Apectodinium hyperacan
thum
in the zonation suggested by Powell (1992), Zone
D4c in the standard Paleogene zonation (Luterbacher
et al., 2004), and Zone DP6a in the North Sea sedi
ments (Mudge and Bujak, 1996, 2001). The last zone
is correlated with nannoplankton Zone NP9 (Luter
bacher et al., 2004). Thus, the
Apectodinium hypera
canthum
zonal assemblage is of the late Thanetian age.
In the Volga region, dinocysts of the
Apectodinium
hyperacanthum
Zone are known from the Kamyshin
Fm of the Balka Dyupa section (Aleksandrova and
Radionova, 2006). In West Siberia and Turgai, the
concurrent
Apectodinium homomorhum
Zone is estab
lished in the Serov Fm (Vasil’eva, 2000; Iakovleva and
Kulkova, 2003). Hence, the Novouzensk Fm with the
nannoplankton of Zone NP6
Heliolithus kleinpelli
at
the base includes the stratigraphic succession of the
Cerodinium markovae
Beds and the
Apectodinium
hyperacanthum
Zone. Consequently, the age diapason
of the Novouzensk Fm corresponds to the Thanetian.
The
Apectodinium augustum
Zone of the Bostandyk
Fm is enriched to some extent in the
Apectodinium
species (up to 10%), including
A. augustum
, but can
not be defined in the rank of the acme zone. The
respective dinocyst assemblage does not show clear
indications of the basin freshening, although the taxo
nomic diversity of the dinocysts is somewhat con
strained. In addition to
Apectodinium
forms, the
assemblage includes abundant
Deflandrea
species and
numerous
Wilsonidium pechoricum
specimens. The
last taxon has a narrow stratigraphic range in sections
of Austria, Middle Asia, West Siberia, and the Pechora
River basin (Iakovleva and Heilmann–Clausen,
2007). In the Novouzensk section, dinocysts of the
zone can be divided in two subassemblages. The
Apec
todinium
forms, abundant in the lower subassemblage,
are scarce (except for
A. parvum
) in the upper one,
where the dominant taxon is
D. oebisfeldensis
(up to
90% of the subassemblage).
The close trend in the distribution of the
Apectod
inium
and
Deflandrea
forms is established in Zone
NZE1 of New Zealand (Crouch and Brinkhuis, 2005).
Analogous abundance peaks of
Deflandrea oebi
sfeldensis
within the
Apectodinium augustum
Zone are
recorded in deposits of the Kamyshin Fm (Atkarsk site
of the Volga region) and in the Balka Dyupa section
(Aleksandrova and Radionova, 2006). The
Deflandrea
oebisfeldensis
abundance peak is also defined in the
Apectodinium augustum
Zone of the Serov Fm, the
Pershinskii section of central TransUrals (Vasil’eva
and Malyshkina, 2008). This regularity in distribution
trends means that the IETM’s influence on biota of
epicontinental basins resulted in the mass develop
ment of
Deflandrea oebisfeldensis
but not of
Apectodin
ium augustum.
The
Deflandrea
abundance in the
Eocene sections of the PeriTethys (AndrevaGrogor
ovich, 1991) and Turgai region is evidence of the
strong adaptation of this taxon to conditions of unsta
ble salinity in epicontinental basins. The
Apectodinium
augustum
Zone is also recorded in the middle part of
the Nalchik Fm, the Kheu River basin (central Cis
Caucasus), where the respective section interval yields
nannoplankton of Zone CP8b (Radionova et al.,
2008).
Higher in the Bostandyk Fm section, which
includes a member of noncalcareous sandstone (inter
val 523.0–500.0 m), an impoverished phytoplankton
assemblage consists of single
Deflandrea oebisfeldensis,
Apectodinium
sp.,
Cerodinium dartmoorium, C. war
denense
, and
Pyxidinopsis densepunctata.
The com
mon taxon of the assemblage is
Pterospermella
sp. of
Prasinophyceae. Scant macerates contain rare pollen
and spore grains, abundant coalified detritus, and
amorphic organic matter. The assemblage completely
lost the characteristics of the previous assemblage and
includes single taxa of stratigraphic value. Samples
96
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
from the upper part of the interval are barren of
palynomorphs. The stratigraphic interval of the sec
tion depleted in palynomorphs and termed the
Pterospermella
spp. Beds corresponds most likely to
Zone DE1a, containing
Leiosphaeridia, Pterosper
mella, Caryapollenites
, and
Cerodinium wardenense
(Dornoch, Flett Fm) in the North Sea section (Mudge
and Bujak, 2001). Zone DE1a stratigraphically overly
ing Zone DP6
Apectodinium augustum
(Forties Fm) is
of the early Ypresian age (NP10).
The
Deflandrea oebifeldensis
Zone recognized in
the middle part of the Bostandyk Fm (interval 500.0–
486.0 m) is in age an analog of the
Glaphyrocysta ordi
nata
Zone in the zonation suggested by Powell (1992)
for the North Sea and of Zone Viborg 7 in Denmark
(Heilmann–Clausen, 1985, 1994). The latter is distin
guished by the sharply reduced content of
Apectodin
ium
forms and the maximal abundance of
Glaphyro
cysta ordinata
in the respective stratigraphic interval of
the Ø
lst
Fm (Heilmann–Clausen, 1985, 1994). In the
Fur Fm and upper part of the Ø
lst
Fm of Denmark,
zonal assemblages with abundant
Deflandrea oebi
sfeldensis
are also distinguished (Hansen, 1979; Heil
mann–Clausen, 1985). Comparable zonal assem
blages are known as well from the ash series of the Mo
Clay, Fur Fm of the North Sea (Knox and Harland,
1979), from the London Clay enclosing ash interlayers
in the Harwich section of Southeast England (Knox
and Harland, 1979), and from Germany (Heilmann–
Clausen and Costa, 1989). The assemblage of Circum
Caspian region is correlated with that from Zone
DE1bc (top acme
Deflandrea oebisfeldensis
, Balder
Fm) in the North Sea zonation (Bujak and Mudge,
1994; Mudge and Bujak, 2001). In West Greenland,
rocks with variable content of
Deflandrea oebisfelden
sis
and
Glapyrocysta ordinata
are distinguished as the
Deflandrea oebisfeldensis
interval, which is correlated
with Zone D5b in the scale by Powell (Powell, 1992;
NøhrHansen, 2003). Thus, dominant species of the
assemblage (
D. oebisfeldensis, G. ordinata
, and
H. tubiferum
in some sections) can be regarded as
“facies substitutes” in corresponding marine environ
ments. The
Deflandrea oebisfeldensis
acme zone is of
the early Ypresian age and concurrent with the nanno
plankton Zone NP10 (Mudge and Bujak, 2001).
We should mention that in the Novouzensk sec
tion, there are two comparatively narrow stratigraphic
intervals of acme
Deflandrea oebisfeldensis
, which are
separated by a sandstone member with
Pterospermella
spp. De Coninck (1994) also reported about two levels
of acme
Deflandrea oebisfeldensis
in sections of the
North Sea. In the Novouzensk section, these biostrati
graphic units contain associated taxa: species of the
Apectodinium augustum
Zone are confined to the lower
unit, whereas the upper one yields morphotypes close
to
Deflandrea
, i.e.,
Cerodinium
, chorate
Cor
dosphaeridium, Hystrichosphaeridium
, and
Glaphyro
cysta.
The lower interval of the Novouzensk section,
where acme
Deflandrea oebisfeldensis
is recorded,
belongs to Zone D5a (DP6b)
Apectodinium augustum
(NP9); the upper interval belongs to Subzone DE1b
Deflandrea oebisfeldensis
acme (NP10). In more con
denced sections, we would expect to observe one of the
intervals with acme
Deflandrea oebisfeldensis
(lower,
upper, or conjoined), as they should be hardly distin
guishable in sediments deposited in basins with weakly
developed
Apectodinium
flora. Zone DE1 with acme
Deflandrea oebisfeldensis
established in several sections
of the TransUrals (Vasil’eva, 2000; Oreshkina et al.,
2004) is correlative by implication with the nanno
plankton Zone NP10
Discoaster diastypus.
Andreeva–
Grigorovich (1991) described the
Deflandrea oebi
sfeldensis
Beds in the Manysai Fm (Borehole SP1) of
the East CircumCaspian region and the nannoplank
ton of Zone NP9
Discoaster multiradiatus
from depos
its, underlying the beds. She synchronized these bios
tratigraphic units but did not mention any
Apectodinium
form from the
Deflandrea oebisfeldensis
Beds. Conse
quently, it is difficult to stratify properly the sediments
of the IETM epoch based on dinocysts.
Higher in the Bostandyk Fm section, the
Dracod
inium varielongitudum
Zone is distinguished (interval
486.0–460.0 m) with very diverse species of dinocysts,
including taxa of the earlier Ypresian zones. Chrono
logically, the youngest species is the marker of the
zone. Peridinoid cysts are more diverse in zonal
assemblage than the other morphotypes. The
Dracod
inium varielongitudum
Zone concurrent with Zone
D7c of the standard zonation (Luterbacher et al.,
2004) and Zone DE2c in the North Sea scale (Mudge
and Bujak, 1994) is of the middle Ypresian age. The
Dracodinium varielongitudum
Zone is correlated with
the top of nannoplankton Zone NP11 and part of
Zone NP12 in the standard zonation (Luterbacher
et al., 2004; Mudge and Bujak, 1994).
Remote subdivisions that can be correlated with
the stratigraphic level under consideration are the
London Clay of Southeast England (Costa and
Downie, 1976), the Cuisian deposits of the Paris basin
(Chateauneuf and Gruas–Cavagnetto, 1978), the
Ypresian argillites of Belgium (De Coninck, 1988),
and the
R
ø
sn
æ
s
Clay of Denmark (Heilmann–
Clausen, 1985, 1994). Around the study region, these
are the lower part of the Tsaritsyno Fm (Zone Dn9) of
the Volga region (Akhmetiev and Beniamovski, 2003),
part of the Cherkessk Fm in the Caucasus (Radionova
et al., 2003), the top interval of the Irbit Fm in the
TransUrals, the Kachar deposits of northern Turgai
(Vasil’eva, 2000), the Upper Lyulinvor Subfm in cen
tral areas of West Siberia (Iakovleva and Kulkova,
2003), and the Balisai Fm of the East CircumCaspian
region (Andreeva–Grigorovich, 1991). In the biozo
nation suggested for the CIS’ southern regions, the
Dracodinium verielongitudum
Zone corresponds in
range to the upper part of Zone NP11
Discoaster bino
dosus
(Andreeva–Grigorovich, 1991). Within the
Dra
codinium varielongitudum
Zone of the Novouzensk
section, a transition to the carbonate type of sedimen
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 97
tation is recorded (at the depth 475.0 m), and its upper
part is concurrent with the nannoplankton Zone
NP12
Marthasterites tribrachiatus.
Species of genera
Pemma, Pontosphaera
, and
Heli
cosphaera
play a significant role in the zonal assem
blage of Zone NP12
Marthasterites tribrachiatus
(=
Tribrachiatus orthostylus
), which is distinguished in
the interval 475.0–420.0 m. The species
M. tribrachi
atus
Defl., whose smaller forms with thin processes
occur in lower part of the zone, whereas very large
forms with massive processes are characteristic of the
middle and upper parts, is abundant in this zone. Spe
cies of the genus
Discoaster
are comparatively numer
ous. The highest taxonomic diversity and largest forms
are confined to the upper part of the zone. The joint
occurrence of characteristic Eocene species (nearly
40 taxa) and FAD
M. tribrachiatus
define the middle
Ypresian age of the host deposits.
The
D. varielongitudum
dinocyst assemblage over
lies in the section the
Deflandrea oebisfeldensis
Zone.
Several dinocyst zones (D6a
Wetzeliella astra
, D6b
Wetzeliella meckelfeldensis
, D7a
Dracodinium simile
,
D7b
Dracodinium solidum
) are missing, which is evi
dence of the considerable hiatus below the clay beds
overlying the sandstone member. The hiatus seems to
be of the regional rank (Andreeva–Grigorovich, 1991;
Radionova et al., 2003) and spans the interval of the
early Ypresian s.s. zones NP 10 (part)–NP11 (part).
Thus, the middle part of the Bostandyk Fm bears the
nannoplankton and dinocysts of the middle Ypresian
zones NP12
Martasterites tribrachiatus
and D7c
Dra
codinium varielongitudum
, respectively.
The
Dracodinium politum–Charlesdowniea coleo
thrypta
zonal assemblage from the upper part of the
Bostandyk Fm (interval 460.0–414.0 m) exemplifies
the high productivity and taxonomic diversity of the
dinoflagellate cysts. The respective dinocyst zone is
defined by the first occurrence of
D. politum
, wheras
rare specimens of
Ch. coleothrypta
appear inside the
zone interval. Both species are characteristic of Zone
D8 in the standard Paleogene zonation (Luterbacher
et al., 2004). The associated taxa are
Diphyes col
ligerum, Charlesdowniea crassiramosa, Areoligera medu
settiformis, Dracodinium condylos
appearing in the
upper part of the zone, subordinate
D. pachydermum,
Rh. glabrum
subsp.
crassithecum
, and
Cerebrocysta bar
tonense
(Fig. 3). The peak abundance of
Dracodinium
politum, Deflandrea phosphoritica
, and
Cordosphaerid
ium gralile
is recorded in the interval 426.0420.0 m.
Deflandrea phosphoritica
is the dominant species near
the zone top, where it occurs in association with sub
species of this taxon,
Wetzeliella articulata
Eis., and
Wetzeliella
aff.
articulata
sensu Chat. et GruasCavag.
Andreeva–Grigorovich (1991) was the first to estab
lish in the CircumCaspian region the
Deflandrea
phosphoritica
acme inside Zone NP12.
Some peculiarities in the succession of the first
appearance dates (FAD) of stratigraphically important
species characterize Zone D8, comprehensively
described in Germany (Heilmann–Clausen and
Costa, 1989), where its distinctive feature is the first
appearance of
Dracodinium politum.
According to the
cited work, specimens of
Charlesdowniea coleothrypta
are rare in that zone except for its top interval. Inside
the zone, FAD
Ch.
aff.
clathrata
,
C. bartonensis,
P. laticinctum, W.
samlandica
and LAD
H. heslertonen
sis, W. meckelfeldensis
, and
D. varielongitudum
are
recorded (Heilmann–Clausen and Costa, 1989). We
established all these distinctive characters in the study
region. The outburst of an abundance of
C. gracile
,
recorded at the top of the zone in Germany (Heil
mann–Clausen and Costa, 1989) is recognized as well
in the Novouzensk section. In the Paleogene zonation,
the distribution range of
Charlesdowniea coleothrypta
and
Dracodinium politum
corresponds to Subzone
D8a, which is correlated with the upper part of nanno
plankton Zone NP12 (Luterbacher et al., 2004). In the
Novouzensk section, the interval of the occurrence of
the
D. politum
attains the higher stratigraphic level up
to the top of Zone D8, and the maximum develop
ment of this taxon is recorded at the level of the upper
boundary of Zone NP12. In this section, the distribu
tion range of the
Dracodinium politum–Charlesdown
iea coleothrypta
zonal assemblage is concurrent with
the conjoined interval of nannoplankton zones NP12
Marthasterites tribrachiatus
(part)–NP13
Discoaster
lodoensis.
In the zonation suggested by Andreeva–Grigorov
ich (1991) for the CIS’ southern regions, the base of
Zone NP12
Marthasterites tribrachiatus
is defined at
the basal level of the
Charlesdowniea coleothrypta
Zone. In the Sholaksai Fm of the East CircumCas
pian region (Borehole SP1), the upper part of the
Charlesdowniea coleothrypta rotundata
dinocyst zone
is distinguished, which is correlated with nannoplank
ton Zone NP13
Discoaster lodoensis
(Andreeva–Grig
orovich, 1991). In the Tasaran Fm of the North Aral
region (Borehole 52), Vasil’eva (1994) discovered the
dinocyst assemblage of Zone D8
Charlesdowniea cole
othrypta–Dracodinium politum
, which is enriched in
proximochorate cysts and practically identical to the
concurrent assemblage of the CircumCaspian region.
The
Charlesdowniea coleothrypta
is known also in the
Upper Lyulinvor Subfm, the Nyurol’skii Fm of West
Siberia (Iakovleva and Kulkova, 2003).
The assemblage of Zone NP13 differs from that of
the previous zone by its much greater taxonomic
diversity (about 60 species). Its distinctive features are
the nearly complete extinction of
M. tribrachiatus
and
the appearance of many new species, including
Toweius gammation
(Br. et Sull.) and
T. crassus
(Br. et
Sull.), along with abundant representatives of genera
Pemma, Pontosphaera, Helicosphaera
, and
Micran
tolithus.
In fact, we can speak of an outbreak in the
development of the genus
Rhabdosphaera
, represented
by six species, whereas none of them is known from
Zone NP12. Mass abundance is also characteristic of
Br. bigelowii
(Gran et Braar.) and
C. eopelagicus
Br. et
98
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
Sull. In contrast to sections of the East CircumCas
pian region (Sidor, 1992), the Northern Caucasus
(Muzylev, 1980), and the Crimea (Zernetskii and
Lul’eva, 1990), abundant
Toveius gammation, T. cras
sus
, and
T. magnicrassus
appear in Zone NP13 with a
great delay. Numerous
Imperiaster obscurus
are also
typical of this zone, whereas in sections of the North
ern Caucasus, this taxon disappears at its base. The
nannoplankton assemblage of Zone NP13 is most
similar to the concurrent assemblages of the East Cir
cumCaspian region. The abundance and diversity of
Discoaster
forms is a distinctive feature of the Crimean
sections. In general, assemblages of this zone from the
Crimea–Caucasus, and East and North CircumCas
pian regions are strongly correlated with each other.
The principal distinctions of the studied section are
the low diversity of the
Discoaster
species and the sig
nificant content of the forms representing the
Pemma,
Pontosphaera, Helicosphaera
, and
Rhabdosphaera
genera.
Thus, the upper part of the Bostandyk Fm, which
yields the nannoplankton of Zone NP13
Discoaster
lodoensis
and dinocysts of Zone D8
Dracodinium poli
tum–Charlesdowniea coleothrypta
corresponds in age
to the late Ypresian. We define the upper limit of the
last zone at the top level of Zone NP13
Discoaster
lodoensis
, whereas the comparable Zone
Charlesdown
iea coleothrypta
s.l. used to be considered in strati
graphic charts suggested for the southern areas of
European Russia in a greater range (Andreeva–Grig
orovich, 1991; Akhmetiev and Beniamovski, 2003).
According to the results obtained for the Novouzensk
section, the range of dinocyst Zone D8
Dracodinium
politum–Charlesdowniea coleothrypta
in the North
CircumCaspian region should be spanning part of
Zone NP12
Marthasterites tribrachiatus
and Zone
NP13
Discoaster lodoensis.
Since the dinocyst zones
and their ranges are controversially understood, it is
difficult to correlate in detail the upper section inter
vals with the zonal scale accepted for southern areas of
European Russia. The obvious reasons for this are the
rearrangement and isolation of the basins and the dif
ferentiation of algaflora in the terminal Ypresian and
Lutetian.
The dinocyst assemblage from the
Wetzeliella coro
nata–Areosphaeridium dikyoplokum
Beds spanning
the top of the Bostandyk Fm and the base of the Kop
terek Fm (interval 414.0–400.0 m) is of close taxo
nomic composition, but suggests a lower productivity
of phytoplankton as compared to the previous assem
blage. In the respective zone, FAD
A. diktyoplokum,
W. echinosuturatum, W. ovalis, D. apiculiformis
Andr.
Grig. et Savits., and
W. coronata
(Vozzh) are recorded.
According to the appearance of
A. diktyoplokum
and
the absence of
D. varielongitudum
, this zone seems
correlated with Zone D9 of standard dinocyst zona
tion (Luterbacher et al., 2004). In zonal schemes,
FAD
A. diktyoplokum
is defined at the top of the Ypre
sian, starting at nannoplankton Zone NP13. Single
specimens of
W. echinosuturatum
are known from
Zone D9 (Heilmann–Clausen and Costa, 1989). In
standard zonation, Zone D9 spans the late Ypresian
and greater part of the Lutetian (zones NP13–NP15),
and its base is inside nannoplankton Zone NP13
(Luterbacher et al., 2004).
Based on dinocysts, it is possible to recognize the
Lutetian deposits at the top of the Tasaran Fm and in
sandstones of the Saksaul’skii Fm in the North Aral
and Ustyurt regions (boreholes 50 and 52, Chelkar
site; Borehole 313, northern scarp of Ustyurt, Ash
cheairyk Gorge). From these deposits, Vasil’eva
(1994) described the dinocyst assemblage of Zone
D9b
Systematophora placacantha–Wetzeliella ovalis
,
which includes
A. diktyoplokum
and
D. pachydermum.
The top part of the Upper Lyulinvor Subfm in West
Siberia is correlated with the top of the Bostandyk Fm,
based on FAD
A. diktyoplokum
(Iakovleva, 2008).
Hence, the upper noncalcareous clay facies of the
Bostandyk Fm (interval 414.0–405.0 m of the
Novouzensk section) bear only dinocysts and corre
spond in age to the terminal Ypresian. The character
istic dinocyst species are illustrated in Plates I and II.
The nannoplankton assemblage from Zone NP14
of the Kopterek Fm includes nearly 60 coccolitho
phorid species, mostly inherited from Zone NP13.
Plate I.
Dinocysts from the Tsyganovo, Syzran, and Novouzensk formations of the Novouzensk borehole section:
(1)
Palaeocystodinium bulliforme
Ioann., Upper Syzran Subfm, Sample 55, Specimen 5749; (2)
Palaeocystodinium benjaminii
Drugg, Tsyganovo Fm, Sample 71: Specimen 5902; (3, 4)
Palaeocystodinium australinum
(Cooks.) Lent. et Will, Tsyganovo Fm,
Sample 71: (3) Specimen 5935, (4) Specimen 5918; (5)
Alterbidinium circulum
(Heilm.Claus.) Lent. et Will., Tsyganovo Fm,
Sample 72, Specimen 5892; (6)
Laciniadinium
sp., Lower Syzran Subfm, Sample 59, Specimen 5645; (7, 8)
Cerodinium depres
sum
(Morg.) Lent. et Will., Lower Syzran Subfm, Sample 66: (7) Specimen 5627, (8) Specimen 5615; (9)
Spinidinium densispina
tum
Stanley, Lower Syzran Subfm, Sample 66, Specimen 5579; (10)
Isabelidinium? viborgense
Heilm.Claus., Upper Syzran
Subfm, Sample 53, Specimen 5806; (11)
Senegalinium iterlaaense
NøhrHans. et Heilm.Claus., Upper Syzran Subfm, Sample
57, Specimen 5680; (12)
Cerodinium leptodermum
(Vozzh.) Lent. et Will., Novouzensk Fm, Sample 42, Specimen 6036; (13,18)
Cerodinium striatum
(Drugg) Lent. et Will, Upper Syzran Subfm: (13) Sample 53, Specimen 5796a, 18) Sample 57, Specimen
5691; (14)
Cerodinium speciosum
(Alb.) Lent. et Will, Lower Syzran Subfm, Sample 57, Specimen 5567; (15)
Cerodinium kang
iliense
NøhrHans. et Heilm.Claus., Tsyganovo Fm, Sample 71, Specimen 6955; (16a16c)
Alisocysta
sp.
1
Heilm.Claus.,
Lower Syzran Subfm, Sample 63, Specimen 5468; (17)
Cerodinium markovae
(Vozzh.) Lent. et Will., Novouzensk Fm, Sample
47, Specimen 6030; (19)
Senegalinium ?dilwynense
(Cooks, et Eis.) Stov. et Evitt, Lower Syzran Subfm, Sample 62, Specimen
5914; (20)
Hystrichokolpoma bulbosum
(Ehren.) Morg,, Lower Syzran Subfm, Sample 66, Specimen 5605; (21)
Alisocysta mar
garita
(Harl.) Harl, Novouzensk Fm, Sample 49, Specimen 5997.
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 99
30
µ
m
12
34
5
789 10 11
12 13 14 15
17 18 19 20 21
6
16а
16b
16c
Plate I
100
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
30
µ
m
Plate II
12
3
456789
10 11 12 13
14 15 16 17
18 19 20 21
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
PALEOGENE BIOSTRATIGRAPHY OF THE NORTH CIRCUMCASPIAN REGION 101
The assemblage is lacking
Discoaster lodoensis
Br. et
Ried.,
D. kuepperi
Str., and
Toweius crassus
(Br. et
Sull.) P.N., and includes a lower number of species
representing genera
Pemma, Pontosphaera, Heli
cosphaera
, and
Micrantolithus.
Species
Rhabdosphaera
inflata
Br. et Sull.,
Discoaster sublodoensis
Br. et Sull.,
D. wemmelensis
Ach. et Str.,
Chiasmolithus expansus
(Br. et Sull.) Gart. and some others, e.g., single
Nan
notetrina cristata
(Mart.) P.N., which appear at this
level, are characteristic of Zone NP14. Comparable
assemblages from Zone
Discoaster sublodoensis
(NP14) occur in the Lillebalt Fm of Denmark, the
lower and middle Lutetian of the Paris basin, and the
Bruxellian Stage of Begium (Aubri, 1983, 1986;
PerchNielsen, 1985). The lower part of the zone
(Subzone
Discoaster kuepperi
) is probably missing
from the studied section, because the assemblage
includes the
Rhabdosphaera inflata
Br. et Sull., the
index species of a synonymous subzone, and single
Nannotetrina cristata
(Mart.) P.N. Thus, the part of
the section under consideration can be attributed to
the upper part of Zone NP14
Discoaster sublodoensis
or to Subzone CP12b
Rhabdosphaera inflata.
The
upper marl member of the Kopterek Fm crowning the
Novouzensk section contains dinocysts of the
Wetze
liella
coronata–Areosphaeridium diktyoplokum
Beds
and the nannoplankton of Zone NP14
Discoaster sub
lodoensis.
It is of the Lutetian age.
CONCLUSIONS
(1) Dinocysts and nannoplankton jointly studied
for the first time in the Paleogene reference section
recovered by borehole Novouzensk No. 1 in the north
ern marginal zone of the CircumCaspian depression
demonstrate the extreme efficiency and biostrati
graphic validity of the zonal correlation between two
groups of fossils. Biostratigraphic zones and their
boundaries that are distinguished, based on the distri
bution of dinocysts and nannoplankton, are strongly
correlated with the standard zonation (Luterbacher
et al., 2004). Both groups clarify paleontological char
acterization and substantiate detailed subdivision and
the dating of sediments from the Paleogene reference
section of the region. Eight standard and one local
nannoplankton zones are distinguished in the section,
which is simultaneously corresponded to eight
dinocyst zones and three biostratigraphic units,
ranked as “beds with flora.”
(2) The dinocyst Zone D3a
Alterbidinium circulum
,
first recognized along with nannoplankton Zone NP4
Coccolithus robustus
in the Tsyganovo Fm of the North
CircumCaspian region, most likely marks the top of
the Danian Stage. Zone D3b
Cerodinium depressum
also established for the first time in the Lower and
Upper (part) of the Syzran subformations suggests the
early Selandian age of the respective sediments. Zone
D3b (DP3b)
Isabelidinium? viborgense
and nanno
plankton Zone NP5 characterizing the upper part of
the Upper Syzran Subfm are of the middle Selandian
age. The
Cerodinium markovae
Beds identified in the
Novouzensk Fm and containing
Alisocysta
margarita,
Areoligera gippingensis
, and the nannoplankton of
Zone NP6
Heliolithus riedelli
at the formation base are
of the early Thanetian age (interval of nannoplankton
zones NP6–NP8). Thus, the established
Alterbidin
ium circulum, Cerodinium depressum, Isabelidinium?
viborgense
zones and the
Cerodinium markovae
Beds
impart details to the dinocyst biozonation (Andreeva–
Grigorovich, 1991), which is being used at present in
the southern regions of Russia and implies that the
stratigraphic interval of these subdivisions corresponds
to part of the
Cerodinium speciosum
Zone.
Zone D4c (DP6a)
Apectodinium hyperacanthum
,
established in the upper part of the Novouzensk Fm is
indirectly correlated with nannoplankton Zone NP9
Discoaster diastypus
(part) and defines the late Thane
tian age of the respective section interval. Zone D5a
(DP6b)
Apectodinium augustum
corresponds to the
interval of the Initial Eocene Thermal Maximum
(IETM) and, being correlated with the upper half of
Zone NP9
Discoaster diastypus
, defines the early Ypre
sian age for the basal interval of the Bastandyk Fm.
The
Deflandrea oebisfeldensis
acme identified in the
upper half of the zone most likely corresponds to the
IETM level. The
Pterospermella
spp. Beds and Zone
Deflandrea oebisfeldensis
(acme) located stratigraphi
cally higher in the Bostandyk Fm are correlated with
the lower Eocene Zone DE1ac (D5b)
Deflandrea
Plate II.
Microphytoplankton from the Upper Syzran Subfm, Novouzensk Fm. and undivided Eocene sequence of the
Novouzensk borehole section (1–5, 8, Novouzensk Fm; 7, Upper Syzran Subfm; 6, 9–20, Bostandyk Fm):
(1)
Apectodinium homomorphum
(Defl. et Cooks.) Lent. et Will., Sample 36, Specimen 6068; (2)
Apectodinium hyperacanthum
(Cooks. et Eis.) Lent. et Will., Sample 31, Specimen 6133; (3)
Apectodinium augustum
(Harland) Lent. et Will., Sample 31, Spec
imen 6132; (4)
Apectodinium parvum
(Alb.) Lent. et Will., Sample 31, Specimen 6122; (5)
Apectodinium summissum
(Harl.) Lent.
et Will., Sample 29, Specimen 6145a; (6)
Deflandrea apiculiformis
Andr.Grig. et Savitz., Sample 1, Specimen 6575; (7)
Bothry
occocus
sp., Sample 54, Specimen 5780; (8) scolecodonts, Sample 27, Specimen 6449; (9)
Ochetodinium romanum
Dam., Sample
4, Specimen 6477; (10)
Dracodinium varielongitudum
(Will. et Down.) Costa et Down., Sample 11, Specimen 6232; (11)
Draco
dinium solidum
Gocht, Sample 11, Specimen 6318; (12)
Dracodinium simile
(Eis.) Costa et Down., Sample 8, Specimen 6294;
(13)
Dracodinium condylos
(Wi ll. et D own .) C ost a et Dow n., S amp le 5 , Sp eci men 636 8; ( 14)
Charlesdowniea columna
(Michoux),
Sample 1c, Specimen 7366; (15)
Cordosphaeridium gracile
(Eis.) Davey et Will., Sample 4, Specimen 6426; (16)
Dracodinium pol
itum
Bujak, Sample 4, Specimen 6452; (17)
Deflandrea
sp., Sample 1c, Specimen 7363; (18)
Dracodinium pachydermum
(Caro)
Costa et Down., Sample 8, Specimen 6480; (19)
Wetzeliella samlandica
Eis., Sample 4, Specimen 6411; (20)
Wetzeliella coronata
(Vozzh.) Lent. et Will., Sample 1c, Specimen 7377; (21)
Deflandrea elegantica
Andr.Grig., Sample 2, Specimen 6546.
102
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 1 2010
VASIL’EVA, MUSATOV
oebisfeldensis
in sediments of the North Sea (Mudge
and Bujak, 2001) and correspond to the level of nan
noplankton Zone NP10.
Dinocysts characteristic of Zone D7c (DE2b)
Dra
codinium varielongitudum
and occurring in the upper
interval of their distribution range in the Novouzensk
section, along with the nannoplankton of Zone NP12
Marthasterites tribrachiatus
are of the middle Ypresian
age. Zone D8
Dracodinium politum–Charelsdowniea
coleothrypta
and the nannoplankton of zones NP12
Marthasterites tribrachiatus
and NP13
Discoaster
lodoensis
, which characterize the middle part of the
Bostandyk Fm, are attributed to the middle and upper
Ypresian. The biostratigraphic diapason of the compa
rable Zone
Charlesdowniea coleothrypta
s.s. in the
zonation by Andreeva–Grigorovich (1991) may be
refined at its lower and upper boundaries.
The
Wetzeliella coronata–Areosphaeridium diky
oplokum
Beds with dinocysts at the section top are
concurrent with nannoplankton Zone NP13 in their
lower interval and with Zone NP14
Discoaster sublo
doensis
in the upper part. This subdivision spans there
fore the upper Ypresian and part of the Lutetian.
(3) Based on the integrated biostratigraphic study of
the Novouzensk reference section, we estimated the fol
lowing age ranges of the regional lithostratigraphic subdi
visions. According to the results of nannoplankton inves
tigation (zones NP2
Cruciplacolithus tenuis
and NP3
Chi
asmolithus danicus
), deposits of the Algai Fm are
attributed to the earlymiddle Danian. The Tsyganovo
Fm containing nannoplankton of Zone NP4 and
dinocysts of Zone D3a
Alterbidinium circulum
is of the
late Danian age. The early–middle Selandian age is
established for sediments of the Lower and Upper Syzran
subformations. The Novouzensk Fm is of the Thanetian
age. The Bostandyk Fm spans interval of the Ypresian
Stage. The Lutetian age is defined for the lower part of the
Kopterek Fm. Direct correlations between nannoplank
ton and dinocyst zones and their comparison with stan
dard zones of Paleogene scale are used to substantiate the
presence of stratigraphic hiatuses at the Algai Fm base
(basal Danian), at the top of the Upper Syzran Subfm
(upper Selandian), and in middle part of the Bostandyk
Fm (lower Ypresian).
ACKNOWLEDGMENTS
We are grateful to the managers of OAO “Sara
tovneftegaz”, who gave us the opportunity to study
and collect core samples from the reference section
Novouzensk no. 1. The constructive comments and
advice of M.A. Akhmetiev and V.N. Beniamovski from
the Geological Institute of the Russian Academy of
Science were used to improve the manuscript. We also
thank L.G. Nosyreva from the West Siberian Research
Institute of Oil and Gas Problems (Tyumen), who
macerated palynomorphs from the studied rock sam
ples.
The work was supported by the Russian Founda
tion for Basic Research, project no. 060564780.
Reviewers M.A. Akhmetiev
and V.N. Beniamovski
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