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557
ISSN 0869-5938, Stratigraphy and Geological Correlation, 2017, Vol. 25, No. 5, pp. 557–580. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © E.A. Shcherbinina, A.I. Iakovleva, E.Yu. Zakrevskaya, 2017, published in Stratigrafiya, Geologicheskaya Korrelyatsiya, 2017, Vol. 25, No. 5, pp. 84–108.
Middle Eocene to Early Oligocene Nannofossils and Palynomorphs
from the Landzhar Section, Southern Armenia:
Zonal Stratigraphy and Paleoecology
E. A. Shcherbininaa, *, A. I. Iakovlevaa, and E. Yu. Zakrevskayab
a Geological Institute, Russian Academy of Sciences, Moscow, Russia
b Vernadsky State Geological Museum, Russian Academy of Sciences, Moscow, Russia
*e-mail: katuniash@gmail.com
Received December 24, 2015; in final form, June 8, 2016
Abstract⎯The results of the study of nannofossils and palynomorphs from the Landzhar section in southern
Armenia were used to correlate bioevents of two groups of microorganisms, recognize zonal subdivisions, and
identify variations in the assemblage compositions reflecting changes in the hydrology and sedimentation
regime in the basin during the middle Eocene to early Oligocene.
Keywords: nannofossils, palynomorphs, dinocysts, Bartonian, Priabonian, Paleogene, Armenia
DOI: 10.1134/S0869593817050069
INTRODUCTION
In the Paleogene, the territory of Armenia repre-
sented the transitional zone between the Tethyan and
Peri-Tethyan realms (Popov et al., 2009) and attracted
the attention of many researchers for a long time pro-
viding the interregional correlation of zonations based
on different groups of biota from these paleogeo-
graphic domains. Since the lower boundaries of the
Bartonian and Priabonian stages are still not ratified in
the Paleogene timescale, their study continues in
many sections of different regions. The upper Paleo-
gene of southern Armenia has a great potential for cor-
relation and subdivision of the Bartonian to Rupelian
interval because of the co-occurrence of Tethyan and
Peri-Tethyan biota elements, including abundant and
diverse nannofossil, planktonic and larger foramini-
fers and dinocyst assemblages.
The Paleogene sediments of Armenia have been
studied stratigraphically for 100 years (Gabrielyan,
1964; Grigoryan, 1979). Planktonic foraminifers,
nannofossils, and nummulites were intensively studied
in different areas of Armenia (Saakyan-Gezalyan,
1957; Veguni, 1978; Grigoryan, 1979, 1986; Krashen-
innikov et al., 1985; Krasheninnikov and Ptukhyan,
1986; Airapetyan and Zakrevskaya, 2013). Palynolog-
ical investigations of the Paleogene sections of Arme-
nia have been made during more than 60 years. Con-
tinental palynomorphs of the region were studied by
Ya.B. Leiye, L.A. Panova, and E.Yu. Maligonova
(Leiye and Leiye, 1960; Leiye, 1968; Panova et al.,
1984; Bugrova et al., 1988). The first evidence for
dinoflagellate cysts from the Paleogene deposits of
Armenia (Bitlizhdin and Shoragbyur sequences,
Eocene–Oligocene) was reported by Leiye (1968).
Later, a phytoplankton community from the Paleo-
gene sediments of Armenia was studied by A.S. Andre-
eva-Grigorovich and N.I. Zaporozhets. Dinoflagel-
late cyst from the Paleocene–Eocene sediments of the
Vedi, Shagap, Shoragbyur, and Landzhar sections
became the basis for the Paleogene zonal scheme of
the southern part of the former Soviet Union compiled
by Andreeva-Grigorovich (1991). She recognized two
dinocysts zones, the Carpatella cornuta Zone and the
Deflandrea speciosa Zone, in the Paleocene interval
of the Kotuts Formation. The succession of the
Eocene to Oligocene dinocyst zones Charlesdowniea
coleothrypta s.l. (Sevan Formation), Rhombodinium
draco/Wetzeliella articulata (Arpa Formation),
Charlesdowniea clathrata angulosa (“sandy–argilla-
ceous” formation), Phthanoperidinium amoe-
num/Wetzeliella symmetrica (lowermost Shoragbyur
Formation), and Wetzeliella gochtii (Shoragbyur For-
mation) was established in the Paleogene deposits of
Armenia; the Eocene–Oligocene boundary was
defined at the base of the P. amoenum Zone. At the
same time, palynological assemblages from the upper
Eocene to lower Oligocene interval were studied by
Zaporozhets (1989) in Landzhar Borehole 1 (southern
Armenia).
The Landzhar section (formerly known as the
Biralu section) in southern Armenia (Fig. 1), which
became the subject of this study, has long been consid-
ered as the type section for the base of the Oligocene
of the southern Soviet Union (Krasheninnikov and
558
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Akhmetiev, 1998). However, the changes in the Paleo-
gene stratigraphy that occurred during the last
20 years, including the changes in the definition of the
stage boundaries and the search for potential GSSPs
for the Lutetian–Bartonian and Bartonian–Pria-
bonian boundaries, the identification of the major cli-
mate events, and refinement of microfossil-based
zonations suggest further more detailed studies of
Paleogene deposits of southern Armenia and the
Landzhar section, in particular.
The goals of this paper are (1) detailed stratigraphic
and quantitative analysis of calcareous nannofossil
and dinocyst assemblages from the middle Eocene–
lower Oligocene part of the Landzhar section,
(2) combining study of nannofossils and dinocysts in
order to establish a succession of key biostratigraphic
events (or a calibration of bioevents), (3) comparison
of the successive bioevents revealed with those of other
World areas for interregional correlation and more
precise dating of the sediments, and (4) interpretation
of the quantitative micropaleontological data to
reconstruct middle Eocene–early Oligocene environ-
mental variations during the middle Eocene to early
Oligocene. The boundaries of the Paleogene subseries
in this paper were accepted sensu Luterbacher et al.,
2004.
Fig. 1. (a, b) Geographic location and (c) paleogeographic settings (modified after Popov et al., 2009) of the Landzhar section,
southern Armenia.
Turkey
Iran
Georgia
Yerevan
YerevanYerevanYerevan
Azerbaijan
Azerbaijan
Landzhar
Donetsk
uplift
Donetsk
uplift
Donetsk
uplift
Peri-TethysPeri-TethysPeri-Tethys
Greater Caucasus basinGreater Caucasus basin
Greater Caucasus basin
South
Caspian
depression
East Black Sea
depression
LesserLesser
Lesser
TethysTethysTethys
Landzhar
LandzharLandzhar
TbilisiTbi lisiT bilisi
Baku
BakuBaku
Shagap (5 km)
Mt. Puchursar
Landzhar
Mt. Aslansar
Lusashokh
Urstalandzh
Birali R.
Armash (18 km)
Mt. Biralo-Kuzei
Elpin (13 km)
CaucasusCaucasusCaucasus
36°42°48°
36°
40°
44°
(a) (b)
(c)
N10
2156.6
N
44°58′ E
39°50′ N
1426
1403
2149.1
M2 1960.8
1 km
2108.2
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 559
THE STUDY OF THE PALEOGENE
SEDIMENTS IN THE LANDZHAR SECTION
A brief summary on the section and the recorded
foraminiferal assemblages was presented by Saakyan-
Gezalyan (1957), Gabrielyan (1964), and Grigoryan
(1979) and a detailed study of this section began in the
70s and was associated with a global changing from
benthic molluscan and nummulitic faunas as key
stratigraphically used fossils to planktonic foramini-
fers and calcareous nannofossils. In the 80s, the
detailed study of nummulites, nannofossils, plank-
tonic foraminifer, and palynomorphs of the Landzhar
section were made (Krasheninnikov et al., 1985, 1998;
Zaporozhets, 1989; Andreeva-Grigorovich, 1991).
In the 80s, the study of calcareous nannofossils in
the Landzhar section was made for zonal subdivision
and correlation with planktonic foraminiferal and
nummulitid regional zonations and subsequent cor-
relation to the international standard zonations
(Krasheninnikov et al., 1985). In the considered part
of the section, N. Muzylöv identified the succession of
Reticulofenestra umbilica, Chiasmolithus oamaruen-
sis, Isthmolithus recurvus, and Helicosphaera reticu-
latа zones. At the same time, he referred the scarcity of
Discoaster barbadiensis and D. saipanensis and their
redeposition into the sediments considered as lower
Oligocene on the basis of planktonic foraminifera
studied.
Palynomorphs (spores and pollen of terrestrial
plants and organic-walled phytoplankton) from other
sections in the vicinity of the village of Landzhar were
studied by L.A. Panova, A.S. Andreeva-Grigorovich,
and N.I. Zaporozhets. The most detailed study of the
marine and continental palynomorphs from the upper
Eocene–Oligocene interval of the Landzhar Borehole
1 and outcrop was present by N.I. Zaporozhets
(Zaporozhets, 1989; Krasheninnikov et al., 1989,
1998). It was shown that the upper Eocene–lower Oli-
gocene part of the section contains five palynological
assemblages which were correlated with planktonic
foraminiferal zones: assemblage 1 corresponding to
subtropical environment was recognized in the Glo-
bigerapsis semiinvoluta Zone–lower part of the Tur-
borotalia cocoaensis Zone (late Eocene); assemblage
2, identified in the upper part of the T. cocoaensis
Zone–lower part of the Globigerina tapuriensis Zone,
indicates progressive cooling; assemblage 3 (upper-
most part of the Gl. tapuriensis Zone–lowermost part
of the Globigerina sellii Zone) contains higher pro-
portions of angiosperm pollen; assemblage 4 (Globi-
gerina sellii Zone) indicates relative warming during
the second half of the early Oligocene; assemblage 5
(uppermost Gl. sellii Zone) is dominated by angio-
sperms, especially by subtropical oak pollen.
On the basis of phytoplankton from the same sam-
ples, Zaporozhets (1989) established three local dino-
cyst zones. Within the local upper Eocene Areos-
phaeridium diktyoplokum–Areosphaeridium arcua-
tum Zone, she recognized the bed with Thalassiphora
delicata (Gl. semiinvoluta Zone–lower part of the
T. cocoaensis Zone, late Eocene) and the Bed with
Hystrichokolpoma salacium (upper part of the
Gl. cocoaensis Zone, Turboratalia centralis, Globi-
gerina gortanii Zone and the lower part of the
Gl. tapuriensis Zone, late Eocene–Oligocene). The
Phthanoperidinium amoenum Zone (lower part of the
Gl. tapuriensis Zone) was identified in the lower Oli-
gocene interval. The local Wetzeliella gochtii s.l. Zone
(upper part of the Gl. tapuriensis–Gl. sellii Zone),
identified in the upper part of the section, differs from
the same-name European zone by larger stratigraphic
range and incorporation of the Wetzeliella symmetrica
Zone.
Zaporozhets (1989) showed that the identified
assemblages are characterized by the presence of green
algae Tytt odiscu s and Crassosphaera, as well as Lan-
jaria. Neither description nor the picture of the latter
taxon (probably named after its type locality) is given
in this paper.
GEOLOGICAL STRUCTURE
OF THE LANDZHAR SECTION
Position in the Armenian Tectonic Structure
Armenia is located in the central part of the Tauro-
Caucasian segment of the Alpine orogenic belt and
includes the southern Lesser Caucasus and the north-
ern part of the Armenian Highland. The Paleogene
successions of the study area is characterized by great
facies variability (and include a high proportion of vol-
canics), which is related to a complex thrust-fold
structural pattern and tectonic activity of this region
during the Paleogene.
The difference in the structural position of the
northern and southern parts of Armenia (in the active
margin of Eurasia and passive margin of Gondwana,
respectively) caused different sedimentation regimes
in these regions (Agamalyan et al., 2012). The Paleo-
gene sediments of northern Armenia belonging to the
Bazum-Zangezur structural-facial zone are built up
mainly of volcanic-sedimentary and volcanic rocks,
whereas the Paleogene sediments of southern Armenia
(Araks structural-facial zone) consist of carbonate-
siliciclastic, carbonate, and tuffaceous sedimentary
rocks, containing a diverse fauna (Gabrielyan et al.,
1981). The Landzhar section is situated on the north-
ern slope of the Urts Range, built up by Paleozoic
rocks unconformably overlain by the Eocene sedi-
ments. Structurally, it is located on the southeastern
termination of the Shagap Syncline, which forms part
of the Yerevan-Vedi synclinorium (Gabrielyan, 1964;
Gabrielyan et al., 1981). The proximity of Paleozoic
rises and land during Paleogene time caused lower
thickness of the Eocene sediments and the absence of
the Paleocene sediments.
560
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Brief Description of the Section
The generally continuous section comprises sedi-
mentary sequence ranging from the middle Eocene to
Oligocene. However, some its poorly exposed parts
remains unstudied (Fig. 2). Zaporozhets (1989) and
Krasheninnikov et al. (1998) suggested the disturbed
bedding of the Priabonian–Rupelian strata in the
vicinity of the village of Landzhar. M.A. Akhmetiev
(personal communication) assumed that the section is
doubled in this interval. However, our own data show
the normal succession of nannofossil and dinocyst
zones in this interval, that does not allow any signifi-
cant disruption of the bedding.
The Eocene section extends from the right side of
the Vedi–Ekhegnadzor road and continues to its left
si de near the vil lag e of Land zha r. Th e upp er par t of the
middle Eocene, upper Eocene, and Oligocene rocks
are exposed in the slopes of an unnamed creek. The
village of Landzhar is situated on the right bank of this
creek (39°49′39′′ N and 44°58′39′′ E).
The middle Eocene deposits (total thickness ca.
200 m) are formally defined as the Arpa and Azatek
Formations composed of calcareous clays and marls
with rare intercalations of tuffaceous sandstones in the
lower part. The Landzhar section exposes the upper
part of the Azatek Fm. and the Chimandkend and
Shagap Fms. (Fig. 2).
The Azatek Fm. (exposed thickness 10–11 m) is
composed of light gray and yellowish silty marls with
abundant planktonic foraminifers.
The conformably overlying Chimandkend Fm.
(80 m thick) is built up of alternated marls and num-
mulitic limestones of the 6–7 m thick N. maximus
Horizon (formerly known as N. millecaput Horizon).
The main part of the formation is represented by gray
calcareous clays with carbonate content decreasing up
the section. The uppermost part of the clayey unit is
poorly exposed. Intercalations of Discocycline lime-
stones that are observed at the top of the Chimand-
kend Fm. in the Vedi and Arpa areas are missing in this
outcrop.
The base of the overlying Shagap Fm. is composed
of sandy clays with exposed thickness of ca. 1–2 m,
which are overlain with a sharp contact by sandy lime-
stones and calcareous sandstones containing remains
of macro- and microbenthic faunas and few plank-
tonic foraminifers. The abundant and low-diverse
nummulite assemblage of the sandy limestones sug-
gests N. fabianii retiatus Zone (Eocene/Oligocene
transition). This formation, up to 150 m thick, consists
of yellowish gray low-calcareous and non-calcareous
sandy-argillaceous sediments with few thin intercala-
tions of clays at the base and fine pebble conglomer-
ates at the top. The uppermost part of the formation,
up to 40 m thick, consists of globe-shaped sandstone
with a significant proportion of tuffaceous material.
The conglomerate beds of this interval includes com-
mon remnants of Oligocene mollusks and rare Oligo-
cene nummulites. The Oligocene tuffaceous-sandy
sequence is overlain by Neogene andesite–dacite.
MATERIALS AND METHODS
Paleogene sediments were sampled in several out-
crops exposed along the banks of the unnamed creek
on the northern outskirts of the village of Landzhar
(Fig. 1), from the Shagap–Landzhar road and
upstream. The outcrops represent a series of isolated
exposures of variable apparent thickness, which are
separated by grass-covered intervals.
Nannofossils were studied in 33 samples collected
by E.Yu. Zakrevskaya during several field trips. The
nannofossil study was made using an Olympus BX-41
light microscope equipped with an Infinity X digital
camera. The smear-slides were prepared by standard
technique (Bown and Young, 1998). The stratigraphic
subdivision of the section was performed using nanno-
fossil standard zonations of Martini (1971) codified as
NP, Okada and Bukry (1980) codified as CP, and
Agnini et al. (2014) codified as CNE. The zonal mark-
ers are shown in Fig. 3.
The palynological study was performed on 21 sam-
ples collected from the middle Eocene–lower Oligo-
cene part of the section. Palynological samples were
prepared using the standard technique of the Labora-
tory of Paleofloristics, Geological Institute, Russian
Academy of Sciences, which involved the following:
(1) treatment with 10% hydrochloric acid (HCl) to
remove the carbonate; (2) treatment with a dispersing
agent, e.g., hot sodium pyrophosphate solution
(Na4P2O7 × 10H2O) and subsequent washing every 2 h
to remove clay particles; (3) centrifuging in a heavy
liquid (K2CdI4) with a specific gravity of 2.25 to sepa-
rate organic matter from the heavier mineral fraction;
(4) treatment with 70% hydrofluoric acid (HF) to dis-
solve siliceous components in the sample material;
(5) treatment with 10% hydrochloric acid (HCl) to
remove fluorosilicate gels; (6) washing of samples with
distilled water and final mounting in glycerine gelly.
The taxonomy of the most dinocysts corresponds
to that cited by Fensome et al. (2008), except for the
family Wetzelielloideae, for which the systematics of
Williams et al. (2015) is used. Quantitative palynolog-
ical analysis was performed in two steps: (1) counting
of at least 200–250 marine and terrestrial palyno-
morphs present on each slide (dinoflagellate cysts,
acritarchs, algae Leiosphaeridia spp., aquatic palyno-
morphs 1 of unclear systematic position, prasino-
phytes, green algae, other aquatic palynomorphs of
unclear systematic position, angiosperm and conifer
pollen, terrestrial plant spores, remains of organic
walled foraminiferal chambers, fungi); (2) counting of
at least 200 dinocysts and subsequent scanning for rare
taxa. The paleoecological interpretation of quantita-
tive variations in palynomorph assemblages was based
on previous studies (Brinkhuis, 1994; Powell et al.,
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 561
Fig. 2. Lithostratigraphy, zonation, and bioevents of the Landzhar section. Numbers in the lithological column denote thickness
of unexposed intervals. The interval of uncertainty of the Bartonian/Priabonian boundary is shown in gray.
25–30
18
29
7
7
1427
1426
1424
1423
1423a
1314 4
1422
1421
1420
1419a
1419
1418
1417
1417a
1416
1414a
1414
1413
1412
1410
1409
1408
1407
1406
1405
140 4
1403
1411
1415
13325
13324
13323
13322
13321
13320
1331 9
13311
13312
13313
13315
1518
1516
1514
6
12–15
middle Eocene
D. saipanensis
Discoaster barbadiensis
Cribrocentrum reticulatum
Cribrocentrum isabellae
Chiasmolithus grandis
Chiasmolithus oamaruensis
Sphenolithus obtusus
Dictyococcites bisectus
Pontosphaera latelliptica
Helicosphaera lophota
Corannulus germanicus
Reticulofenestra umbilicus
Cribrocentrum reticulatum
Wetzeliella gochtii
Wetzeliella spinula
Lentinia serrate
Melitasphaeridium pseudorecurvatum
Enneadocysta harrisii, Reticulatosphaera actinocoronata
Cooksonidium capricornum, Enneadocysta deconinckii
Cooksonidium capricornum-group
Hemiplacophora semilunifera
Rhombodinium draco-porosum
Enneadocysta multicornuta, Rhombodinium rhomboideum,
Trigonopyxida fiscellata
Enneadocysta pectiniformis, Enneadocysta robusta,
Rhombodinium aidae, Thalassiphora fenestrata,
Glaphyrocysta intricate
Wetzeliella gochtiiRhombodinium porosum?
Rhombodinium
draco
?
upper Eocene Oligocene Series/Subseries
Azatek
NP17 NP18–20 NP21
CP14b CP15 CP16
CNE15 CNE16–18
10 m 10 m
CNE19 CNE20 CNE21
Chimandkend Shagap Formation
Stage
Nanno
plankton
zones
Bartonian Priabonian
Sample nos.
Bioevent
Nannoplankton Dinocysts
Dinocyst zones
Carbonate clay
and marl
Carbonate sandy clay
and siltstone
Clayey sandstone
Sandstone
Gritstone
and sandstone
Sandy limestone
Nummulitic limestone
Thickness, m
Martini, 1971
Lithology
Okada & Bukry, 1980
Agnini et al., 2014
23
5
15
6
9
7
7
3
10
11–13
3
7
562
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
1996; Sluijs et al., 2005; Crouch and Brinkhuis, 2005;
Pross and Brinkhuis, 2005; Toricelli et al., 2006).
For the interpretation of paleoenvironmental con-
ditions, the dinoflagellate cysts were subdivided into
23 groups of similar morphology: (1) Wetzelielloids,
(2) Deflandroids, (3) Phthanoperidinium, (4) other
peridinioids, (5) Homotryblium, (6) Thalassiphora,
(7) Areoligera, (8) Cleistosphaeridium diversispinosum,
(9) Enneadocysta, (10) Cribroperidinium, (11) Cordos-
phaeridium, (12) Operculodinium spp., (13) Achilleod-
inium biformoides, (14) Diphyes/Dapsilidinium,
(15) Hystrichokolpoma, (16) Spiniferites, (17) Batiacas-
phaera/Kallosphaeridium, (18) Cerebrocysta/Corru-
dinium, (19) Microdinium reticulatum, (20) Impagidin-
ium, (21) Nematosphaeropsis, (22) other gonyaula-
coids, (23) undetermined gonyaulacoids. The group of
Deflandroids includes specimens of the genera
Deflandrea, Lejeunecysta, Lentinia, and Senegalinium.
The group of Areoligera includes Areoligera, Glaphyro-
cysta, Membranophoridium, Hemiplacophora, and
Schematophora. The group of Enneadocysta consists of
Enneadocysta, Cooksonidium, and Areosphaeridium,
whereas the group of Cordosphaeridium includes Cor-
dosphaeridium, Fibrocysta, Araneosphaera, Lanternos-
phaeridium, and Tur bi osphaera. The group of Homo-
tryblium consists of Homotryblium, Heteraulacacysta,
Eocladopyxis, Lingulodinium, and Polysphaeridium.
The group of Spiniferites includes Spiniferites, Acho-
mosphaera, Hystrichosphaeropsis, and Rottnestia.
RESULTS
Nannofossils
Calcareous nannofossils are present throughout
the section (Table 1, Plate I) and show variations in
their total abundance and relative abundance of indi-
vidual species. At the base of the Oligocene part of the
section, nannofossils become less diverse and gradu-
ally disappear up the section. The nannofossil assem-
blages are characterized by high species diversity (over
50 species were identified throughout the section),
which does not vary in the Eocene part of the section.
The most distinctive features of this assemblage is the
very low abundance of warm-water discoasters, the
rarity of cool-water chiasmolith taxa and the domina-
tion of Dictyococcites spp. and various reticu-
lofenestrids, which are interpreted to be eurytopic cos-
mopolitan taxa.
The nannofossil assemblage dominated by Cycli-
cargolithus floridanus, Coccolithus pelagicus, and
C. formosus and the various large and small reticu-
lofenestrids (Table 1) was identified in the upper part
of the Azatek Formation forming the base of the stud-
Fig. 3. Correlation of the middle–upper Eocene nannofossil zonations and markers (primary markers are shown by large bold
letters and secondary markers are shown by smaller regular letters). The absolute age is from Vandenberghe et al. (2012). The
uncertainty interval at the Bartonian–Priabonian boundary is shown in gray.
Isthmolithus recurvus frequent Isthmolithus recurvus
rare Isthmolithus recurvus
Chiasmolithus grandis
Chiasmolithus oamaruensis
Chiasmolithus oamaruensis
Chiasmolithus solitus
Discoaster saipanensis
Cribrocentrum erbae
Cribrocentrum erbae
Sphenolithus obtusus
Sphenolithus spiniger
Discoaster saipanensis Discoaster saipanensis
Discoaster barbadiensis
Cribrocentrum reticulatum
Cribrocentrum isabellae
Chiasmolithus grandis
Sphenolithus obtusus
Dictyococcites bisectus
Sphenolithus furcatolithoides
middle Eocene upper Eocene
Bartonian Priabonian
Oligo-
cene Rupe-
lian
Subseries
Stage
Ma
Zonal
markers Primary and secondary zonal markers
Agnini et al.,
2014
Martini,
1971
Okada
& Bukry,
1980
CP16
CP15b
CP15a
CP14b
CP14a
NP21
NP19–20
NP18
NP17
NP16
CNE21
CNE20
CNE19
CNE18
CNE17
CNE16
CNE15
CNE14
C13r
C15n
C15r
C16n
C16r
C17n
C17r
C18n
C18r
34
35
36
37
38
39
40
41
Zonal markers
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 563
Table 1. Nannofossil range chart of the Landzhar section: f—few (several specimens per smear-slide), r—rare (several specimens per row of smear-slide), c—common
(1–5 specimens per field of view), a—abundant (>5 specimens per field of view).
Bartonian Priabonian Oligocen Stage/Series
Azatek Chimandkend Shagap Formation
NP17 NP18-20 NP21? Martini, 1971
Nannofossil
zonations
CP14 CP15 CP16? Okada and Bukry,
1980
CNE15 CNE16–18 CNE19 CP15 Agnini et al., 2014
140 3 140 4 310 1405 1406 1407 1408 317 140 9 1410 315 312 311 1411 1412 1413 319 3 20 32 1 322 3 23 32 4 1 414 1514 1515 1516 1517 1518 3 25 1415 1417 1418 1419 1419 a 1420 142 143 1423 1426 Sample no.
ff f ffff f ff Bicolumnus ovatus
ffff ff f f f f f f Chiasmolithuss grandis
rrrrrrrrrcrccccrcrccrrcrrrrrrrff f ff Coccolithus formosus
r ccccccr ccr r rcccc fccccccccccr r r rfr rr f C. pelagi cus
rcrrrrrrrrff frr f ff f f f ff f Cribrocentrum reticulatum
f cr ccr r f ccf f caacf ccccaaccccccarrr r ccr Cyclicargolithus floridanus
rrrracrfcacfrcrarrrrcrcrrrrrfr fff ff Dictyococc ites bisectus
ff fff r rff ffffrf f ff fff D. scrippsae
ffffffrfrfrrcffff f f D. stavensis
f frrrrrrrffcfrrf ff f rf fff rff f f Discoaster barbadiensis
ff ff D. binodosus
f r ff ff ff fffff fff f D. deflandrei
ff ff ff ffffrf f frff ff f D. nodifer
ffffrfrfffffffrfff f fff ffffffffff D. saipanensis
f ff ffff fff f f D. tani
fff ff f Helicosphaera lophota
rrrrrrcfr f frrrff fffr frfff ffrf frrrrf Lanternitus minutus
crfrrrcfrrfrcrrrff fffrrrrrrffr f f Reticulofenestra dictyoda
f fff f ffrrrcrrrrffffff f f R. hillae
rrrrrrrrrrfrrrcrcrrfrrrrrrrrfr f f fR. umbilicus
crcccrrrrrrrrcccrrrrrccrrrrrfrf f f r Sphenolithhus moriformis
fff fff f f S. radians
rfrrrfffffff frf f rrfffffr ffrr Zygrhablithus bijugatus
f ff rrrrrrfr frf ff f Clausico ccus subdistichu s
fr rffffffffff ff ff Cribrocentrum erbae
ffff f f ffffff ff ff fff Pontosphaera plana
fff f frcfr ff rffffffr f f Blackites spinosus
fff fff ffrffffffrffffffr f fff Helicosphaera compacta
fff ff f f Corannulus germanicus
ff ffff ff ff f f fff f f Reticulofenestra lockeri
fff f Chiasmolithus altus
ff f ffff Umbilicosphaera bramlettei
f f fffff f f Dicryococcites filewichii
f fff fff f f ffrfffff Helicosphaera bramlettei
ffffffffff rfff H. reticulata
fff Chiasmolithus oamaruensis
ff ff Pontosphaera latelliptica
ff Sphenolithus pseudoradians
fff Orthozygus brytica
fffffff Pontosphaera multipora
ffffffff f P. p ul ch er
fff f Sphenolithus predistentus
ff f f Cribrocentrum isabellae
fDictyoco ccites daviesii
fff ff Pyrocyclus or angensis
f f Pontosphaera panarium
564
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Plate I
5 μm
1234 5
109876
11 12 13 14 15
20
19
18
17
16
21 22 23 24 25
30
29
28
27
26
31 32 33 34 35
40
39
38
37
36
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 565
Plate I. Microphotographs of nannofossils from the middle Eocene–lower Oligocene interval of the Landzhar section.
(1) Bicolumnus ovatus, cross polarization (XPL), Sample 312; (2) Cribrocentrum reticulatum, XPL, Sample 1410; (3) C. erbae,
XPL, Sample 1409; (4) C. isabellae, XPL, Sample 321; (5) Cyclicargolithus floridanus, XPL, Sample 1415; (6) Reticulofenestra
umbilicus, XPL, Sample 325; (7) R. hillae, XPL, Sample 321; (8) R. oamaruensis, XPL, Sample 1413; (9) Dictyococcites stavensis,
XPL, Sample 311; (10) D. bisectus, XPL, Sample 1408; (11) D. f ilewichii, XPL, Sample 321; (12) D. daviesii, XPL, Sample 319;
(13) D. scrippsae, XPL, Sample 322; (14, 15) Clausicoccus subdistichus, Sample 322: (14) transmitted light (IIPL), (15) XPL;
(16) Pyrocyclus orangensis, XPL, Sample 324; (17, 18) Helicosphaera compacta, Sample 1413: (17) IIPL, (18) XPL; (19) H. reticu-
lata, XPL, Sample 412; (20) H. bramlettei, XPL, Sample 1415; (21, 2 2) Chiasmolithus altus, Sample 1410: (21) IIPL, (22) XPL;
(23) C. grandis, XPL, Sample 324; (24) Chiasmolithus oamaruensis, X PL, Sam ple 1412; ( 25) Discoaster barbadiensis, XPL, Sample
1415; (2 6) D. saipanensis, XPL, Sample 1415; (27) D. def landrei, XPL, Sample 321; (28) D. nodifer, X PL , S am pl e 1415;
(29) D. ornatus, XPL, Sample 1414; (30) D. tani, XPL, Sample 1414; (31) Sphenolithus radians, XPL, Sample 1406; (32) S. pseu-
doradians, XPL, Sample 322; (33, 34) S. predistentus, XPL, Sample 1415: (33) crossed nicols 0°, (34) crossed nicols 45°;
(35) S. moriformis, XPL, Sample 1404; (36) Corannulus germanicus, XPL, Sample 1408; (37) Pontosphaera latelliptica, XPL,
Sample 319; (38) Lanternites minutus, XPL, Sample 1408; (39) Umbilicosphaera protoannula, XPL, Sample 311; (40) Blackites
spinosus, XPL, Sample 313.
ied section (Fig. 2). The only sphenolith species,
Sphenolithus moriformis, is present in relatively high
abundance. The presence of abundant Dictyococcites
bisectus and the absence of Chiasmolithus solitus sug-
gest that this part of the section can be assigned to the
upper parts of NP17 and CNE15 Zones and СР14b
Subzone. The last occurrence (LO) of Sphenolithus
obtusus at the top of the Azatek Fm. (Sample 1406)
defines the base of CNE16 Zone (Fig. 2).
A few specimens of Chiasmolithus oamaruensis
appear in the lowermost part of the Chimandkend
Fm. directly above Nummulites maximus Horizon.
This bioevent corresponds to the base of NP18 Zone
and is considered as a level approaching the base of
CNE17 Zone defined as the interval of Cribrocentrum
erbae acme (Agnini et al., 2014). In the Landzhar sec-
tion, this species is very rare and sporadically distrib-
uted across the section, and hence it is impossible to
recognize the acme interval of this species. Therefore,
the interval of CNE16–NE18 Zone remains undi-
vided. In the Chimandkend Fm., the nannofossil
assemblages increase in abundance and diversity
mostly due to the diverse Helicosphaera (H. bramlettei,
H. compacta, H. reticulata) and Pontosphaera (P. m u l -
tipora, P. pu l c h e r, P. p l a n a, P. p a n ar i um ). The occur-
rence of rather common specimens of these taxa tend-
ing to to neritic environments likely indicates the grad-
ual shallowing of the basin. The LO of Chiasmolithus
grandis, which defines the base of СР15 Zone, was
established at the top of the Chimandkend Fm., i.e.,
much higher than the first occurrence (FO) of both
C. oamaruensis and C. isabellae. Diachroneity in the
extinction levels of this species was recently noted by
Toffanin et al. (2013): its LO was observed in С18n1n
Magnetochron (top of NP16 Zone) in the low-lati-
tudes and in C17n1n Magnetochron (NP18/19
boundary) in the high-latitudes deposits. In the
Landzhar section, this level was recognized in younger
deposits, within СNE19 Zone, which corresponds to
the С16n2n Magnetochron. The LO of C. grandis was
reported at nearly the same level within the Urstatzor
section in southern Armenia (Cotton et al., 2017).
However, significant reworking of the Paleocene and
Eocene species detected in this section evidently
caused much higher stratigraphic position of the LO of
this species. The lack of reworking in the Landzhar
section suggest in situ occurence of C. grandis in upper
part of its range. The LO of C. grandis above the FO of
C. isabellae was also found in the Kazantash section
near the town of Bakhchisaray, Crimea
(E.A. Shcherbinina, unpublished data).
Another stratigraphically important species, Isth-
molithus recurvus, is absent in the section; therefore,
the interval of NP18–NP20 Zones spanning the Chi-
mandkend Fm. and lowermost Shagap Fm. remains
undivided. The FO of C. isabellae in the middle part of
the Chimandkend Fm. (Sample 13321) corresponds to
the base of CNE19 Zone spanning the middle part of
the Priabonian (Agnini et al., 2014). This interval is
characterized by the highest nannofossil species diver-
sity, which decreases in the topmost part of the Chi-
mandkend Fm. The co-occurrence of C. grandis and
C. isabellae in two sections of Armenia is still poorly
understood. It is likely that not only the LO of the f irst
species occurs later (whatever the causes of such a high
LO can be), but, at the same time, the latter species
can have its FO slightly earlier than it was previously
thought.
The Shagap Fm. is characterized by lower nanno-
fossil abundance and reduced species diversity. The
LO of Cribrocentrum reticulatum corresponds to the
base of CNE20 Zone, Pontosphaera latelliptica, which
becomes the common component of Oligocene
deposits of the northern Peri-Tethyan basin (Melinte,
2005; Garecka, 2012; a.o.) has its FO just above this
level. The presence of this species and relatively abun-
dant Lanternites minutus likely evidence a connection
between the southern Armenian basin and northeast-
ern Peri-Tethys. The reduced thickness of this interval
can indicate erosion in the upper part of this zone.
The LOs of Discoaster barbadiensis and D. saipa-
nensis in Sample 1420 are the nannofossil events clos-
est to the Eocene/Oligocene boundary (as defined by
the extinction of Hantkenina foraminifers). Above this
level, the sediments grade into coarser, sandier, and
566
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
almost calcareous-free material. In this interval, nan-
nofossils are characterized by extremely low abun-
dance and species diversity and are represented by a
few specimens of coccoliths and reticulofenestrids,
which become extinct toward the top of the section.
Palynology
The most samples studied from the Landzhar sec-
tion are characterized by abundant palynomorph
assemblages, consisting of more than 150 dinocyst,
acritarch, and prasinophyte taxa. The proportions of
different palynomorph groups vary considerably
within the studied part of the section. For example,
palynological assemblages from the upper part of the
Azatek Fm. exhibit an alternating domination of dino-
cysts and prasinophyte abundance. The assemblages
from the Chimandkend Fm. are characterized by the
relatively constant abundance of dinocysts (40–55%)
and significant variation in the abundance of bisaccate
conifer pollen. At the same time, the proportion of dif-
ferent groups of prasinophytes is not higher than 25%.
The upper part of the formation is characterized by a
decrease in abundance of dinocysts (30%), the domi-
nance of conifer pollen (60%), and an increase in
abundance of angiosperm pollen and terrestrial plant
spores. In contrast to older deposits of the Chimand-
kend Fm., the palynological assemblage from the
Shagap Fm. is characterized by the decreased abun-
dance of dinocysts (from 20% to total absence), the
presence of a few specimens of prasinophytes, and the
wide dominance of terrestrial palynomorphs.
The dinocyst assemblages from the Landzhar sec-
tion contain species having a wide geographic distri-
bution, which allows the correlation of dinocysts
events with the successions from other regions. The
stratigraphic range of dinocysts is shown in Table 2;
the quantitative distribution of different palynomorph
groups is shown in Fig. 4; the distribution of ecological
groups of dinocysts is shown in Fig. 5. Illustrations of
characteristic dinocyst taxa are done in Plates II–V.
From the lowest sample 1403 and up the Landzhar
section, the dinocyst assemblage from the upper part
of the Azatek Fm. contains stratigraphically important
species: Enneadocysta pectiniformis, Enneadocysta
robusta, Rhombodinium? aidae, Thalassiphora fenes-
trata, and Glaphyrocysta intricata. The uppermost part
of the formation is characterized by the successive FOs
of several stratigraphically significant taxa. For exam-
ple, the successive FOs of Enneadocysta multicornuta,
Petalodinium rhomboideum, Trigonopyxidia fiscellata,
and Cooksonidium capricornum group was detected in
the upper part of CNE15 Zone. The FO of Rhombod-
inium spinula in the Landzhar section coincides with
the LO of Sphenolithus obtusus, whereas the successive
appearance of dinocysts species Rhombodinium draco-
porosum and Hemiplacophora semilunifera was found
at the base of the interval of CNE16–CNE18 Zones
(uppermost Azatek Fm.). The co-occurrence of these
dinocysts species likely suggests the recognition of the
interval of Rhombodinium draco dinocyst zone (Bar-
tonian). This zone is widely used in the dinocyst zona-
tions of Western Europe (Costa and Downie, 1976;
Châteauneuf and Gruas-Cavagnetto, 1978; Bujak,
1979; Powell, 1992), Peri-Tethys (Andreeva-Grigor-
ovich, 1991; Akhmetiev and Zaporozhets, 1992; Ore-
shkina et al., 2015), Turgai Trough (Vasil’eva, 2013,
2014), and Western Siberia (Iakovleva and Aleksan-
drova, 2013). The occurrence of the transitional form
Rhombodinium draco-porosum at the top of the Azatek
Formation (at the boundary of CNE15/CNE16
Zones) possibly indicate the level closest to the
boundary of the Rhombodinium draco/Rhombodin-
ium porosum dinocyst Zones (the latter zone is
defined by the FO of Rhombodinium porosum); how-
ever, no typical Rhombodinium porosum specimens
were recognized in the Landzhar section. Typical rep-
resentatives of species Cooksonidium capricornum and
Enneadocysta deconinckii were identified in the top-
most part of the Azatek Fm
The dinocyst assemblage from the uppermost part
of the Azatek Fm. is characterized by a wide domi-
nance (=acme, 53%) of Achilleodinium biformoides
(Sample 1403), which give way (Sample 1404) to the
dominance of Spiniferites (54%) and Enneadocysta
(81%) groups (Sample 1405). The dinocyst assem-
blage from the upper part of the formation is charac-
terized by the occurence of deflandroids (up to 20%)
and a dramatic decrease in abundance of the Enneado-
cysta and Spiniferites groups (~20% each). The assem-
blage from the Azatek Fm. is characterized by the con-
sistent occurence (up to 9%) of species belonging to
the genus Impagidinium, in particular, remarkably
large specimens of Impagidinium brevisulcatum.
The palynological assemblage from the upper part
of the Azatek Fm. is characterized by an alternating
dominance of dinocysts (from 25 to 60%) and prasin-
ophytes of unclear systematic affinity (35–60%). Such
variability in phytoplankton groups and dinocyst
ecogroups may be indicative for an unstable hydrolog-
ical regime and, probably, dramatic salinity variations.
The FOs of Enneadocysta harrisii and Reticulatos-
phaera actinocoronata (Sample 1412) and the LO of
Melitasphaeridium pseudorecurvatum (Sample 1413)
are found slightly above the base of NP18 Zone in the
Chimandkend Fm. The FO of Lentinia serrata was
identified within nannofossil CNE19 Zone. All
assemblages recovered from the major portion of the
Chimandkend Formation contain either stratigraphi-
cally important taxa persisted from the underlying
Azatek Fm. or species having a wide stratigraphic
range, thus preventing correlation of the assemblage
from Chimandkend to the assemblages of middle–late
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 567
Table 2. Stratigraphic range chart of dinocyst species in the Landzhar section. Numbers show the total number of counted specimens; 0—the presence of taxon iden-
tified after counting
Series/Subseries
Stage
Nannofossil
zones
Formation
Sample
Total n umber o f cy sts
Achilleodinium biformoides
Cleistosphaeridium diversispinosum
Enneadocysta pectiniformis
Enneadocysta robusta
Glaphyrocysta intricata
Homotryblium sp. A in Gedl 2005
Hystrychokolpoma pusiila
Impagidinium brevisulcatum
Impagidinium dispertitum-gibrensis
Impagidinium sphaericum
Impagidinium victorianum
Impagidinium sp. B in Gedl 2005
Melitasphaeridium recurvatum
Nematosphaeropsis sp.
Phthanoperidinium crenulatum
Rhombodinium? aidae
Rhombodinium sp.
Thalassiphora fenestrata
Trigonopyxidia ginella
Turbiosphaera symmetrica
Aiora sp. A in Gedl 2004
Amphorosphaeridium multifurcatum
Cerebrocysta bartonensis
Corrudinium incompositum
Enneadocysta multicomuta
Homotryblium tenuispinosum
Hystrichokolpoma bullatum
Hystrichokolpoma spinosum
Lophocysta sp.
Microdinium reticulatum
Petalodinium rhomboideum
Tridonopyxidia fiscellata
Areosphaeridium diktyoplokum
Enn. aff. pectiniformis–C. capricorr.
Martini, 1971
Okada and Bukry, 1980
Agninietal.,2014
Oligocene
Rupelian
|NP21
CP16
CNE21
Shagap
1426 19 3 1
1423 0
1422 29
1420 8 4 2
upper Eocene
Priabonian
NP18–20
CP15
CNE20
1419 221 5 3 1
3
12
1418 22 1 1
CNE19
1416 0
Chimandkend
1415 237 3 1 1 4
CP14b
1518 13 2 1 1 1 14
1414 218 22 2 1 1 1 11
CNE16–18
13323 203 22 1 412
1413 207
1412 210 01211 17 2 0 2 0 0 0
1411 213 23 1000 8 1 20
middle Eocene
Bartonian
NP17
Azatek
1410 209 122 1
4
0014 1
140 9 221 13 6
2
01 2 03
1408 207 14350110 112 01
1407 205 3430 0 103 100 11 1119
CNE20
140 6 208 025 2 1 8 1 1 1 2 3 0
1405 211 0111 401012 05132
140 4 208 32 4 202115 0111 1116111110102
1403 212 11
0
0 13023216122301020
568
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Series/Subseries
Stage
Nannofossil
zones
Formation
Sample
Total n umber of cy sts
Deflandrea phosphoritica
Enneadocysta arcuata
Enneadocysta aff. deconinckii
Enneadocysta sp. C in Stover
& Williams 1955
Heteraulacacysta campanula
Homotryblium plectilum
Phthanoperidinium comatum
Thalladinium? clathratum
С. capricornum-Emmetrocysta urn
Emmetrocysta sp. in Edwards et al. 1984
Homotryblium floripes
Hystrichokolpoma granulatum
Hystrichokolpoma salacium
Hystrichokolpoma unispinum
Impagidinium aculeatum
Impagidinium dispertitum
Impagidinium sp. A in Gedl 2005
Kallosphaeridium biornatum
Samlandia chlamydophora
Thalassiphora gracilis
Rhombodinium spinula
Areosphaehdium ebdonil
Batiacasphaera comptan
Charlesdowniea? rotundata
Glaphyrocysta semitecta
Glaphyrocysta texta
Impagidinium cassiculum
Pentadinium laticinctum
Systematophora urbinii
Rhombodinium draco-porosum
Thalassiphora delicata
Glaphyrocysta ordinata
Hemiplacophora semilunifera
Martini, 1971
Okada and Bukry, 1980
Agninietal., 2014
Hystrichostrogylon membraniph
Oligocene
Rupelian
|NP21
CP16
CNE21
Shagap
1426 19 3 1
1423 0
1422 29 26
1420 84 77
upper Eocene
Priabonian
NP18–20
CP15
CNE20
1419 221 26 0 8 1 3 10 6 1 2
1418 22 2 1 1
CNE19
1416 0
Chimandkend
1415 237 87 1 2 0 48
CP14b
1518 47 2 1 5 0
1414 218 35 1 0 2 1 4
CNE16–18
13323 203 87 0 1 1 1 1 1 13
1413 207 9 2 3 1 0
1412 210 1 1 0 1 1 2 3 0 1
1411 213 1 7 0 2 2 0 1 3 1
middle Eocene
Bartonian
NP17
Azatek
1410 209 25 1 0 1 2 2
1409221101 0 10224 2
140820731 01452 110
1407205471 1 0 04 0 0010411020001
CNE20
1406208322 1 0010101510440100
1405 211 2 1 9 0 0 1 0
140 4 208
1403 212
Table 2. (Contd.)
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 569
Series/Subseries
Stage
Nannofossil
zones
Formation
Sample
Total n umber o f cy sts
Impagidinium maculatum
Pyxidinopsis peniculata
Operculodinium nanaconulum
Cooksonidium capricornum
Enneadocysta deconinckii
Enneadocysta cf. deconinckii
Impagidinium paradoxum
Impagidinium patulum
Areosphaeridium michoudii
Cerebrocysta magna
Enneadocysta deconinckii–C. capricornum
Phthanoperidinium echinatum
Tectatodinium peltitum
Chalesdowniea? fasciata
Enneadocysta harrisii
Hystnchokolpoma cinctum
Impagidinium velorum
Reticulatosphaera actinocorona
Schematophora speciosa
Distatodinium ellipticum
Lentinia serrata
Membranophoridium aspinatum
Pentadinium polypodum
Deflandrea spinulosa
Lejeunecysta hyalina
Selenopemphix armata
Wet zeliella aff. symmetrica
Wet zeliella aff. gochtii
Wet zeliella sp.
Homotrybtium aculetatum
Dapsilidinium simplex
Heteraulacacysta porosa
Wetzeliella gochtii
Martini, 1971
Okada and Bukry, 1980
Agninietal.,2014
Oligocene
Rupelian
|NP21
CP16
CNE21
Shagap
1426 19 1
1423 0
1422 29 1
1420 8 4
upper Eocene
Priabonian
NP18–20
CP15
CNE20
1419 221 10 8 2 1
1418 22 1
CNE19
1416 0
Chimandkend
1415 237 4
CP14b
1518 1 001
1414 218 1 72 511
CNE16–18
13323 203 0 0 1 120
1413 207 124 2 1 4
1412 210 19 1
2010013
1411 213 1 0 6 38 cf. 0
middle Eocene
Bartonian
NP17
Azatek
1410209 216712
140 9 221 2 1
1408 207 0
1407 205 1
CNE20
140 6 208
1405 211
140 4 208
1403 212
Table 2. (Contd.)
570
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Fig. 4. Quantitative distribution of palynomorph groups in the Landzhar section. For explanations, see Fig. 2.
10 %30 50 10 30 50 30 50 30 5010 3 0 10 10 10 10 10 10
1426
1423
1422
1420
1419
1418
1416
1415
1414
1413
1412
1410
1409
1408
1407
1406
1405
140 4
1403
1411
13323
1518
18
29
NP21NP18–20NP17
CP16CP15CP14b
CNE21CNE20CNE19CNE16–18CNE15
10 m10 m
25–30
15
7
7
6
12–15
6
9
7
7
3
10
11– 13
3
7
23
5
middle Eocene upper Eocene Oligocene Series/Subseries
Azatek Chimandkend Shagap Formation
Stage
Nanno-
fossil
zones
Bartonian Priabonian
Sample nos.
Thickness, m
Martini, 1971
Lithology
Okada & Bukry, 1980
Agnini et al., 2014
Rupelian
Dinoflagellate cysts
Acritarchs
Leiosphaeridia spp.
Prasinophytes
Green algae
Unidentified
aquatic
palynomorphs
Angiosperm pollen Bisaccate conifer pollen Spores
Inner foraminiferal
chamber s
Fungi
Aquatic palynomorph 1
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 571
Fig. 5. Quantitative distribution of dinocyst ecological groups in the Landzhar section.
10 %30 50 1070 7050 30 50 30 5010 10 30
30
90 10 10 10 10 10 10 10 10
1426
1423
1422
1420
1421
1419
1418
1416
1415
1414
1413
1412
1410
1409
1408
1407
1406
1405
1404
1403
1411
13323
1518
18
29
NP21NP18–20NP17 CP16CP15CP14b
CNE21
CNE20
CNE19CNE16–18CNE15
10 m
10 m
25–30
15
7
7
6
12–15
6
9
7
7
3
10
11– 13
3
7
23
5
middle Eocene upper Eocene Oligocene Series/Subseries
Azatek Chimandkend Shagap Formation
Stage
Nanno-
plankton
zones
Bartonian Priabonian
Sample nos.
Thickness, m
Martini, 1971
Lithology
Okada & Bukry, 1980
Agnini et al., 2014
Rupelian
Wetzelielloids
Deflandroids
Phthanoperidinium spp.
Other peridinioids
Homotryblium-group
Thalassiphora spp.
Areoligera-
group
Cleistosphaeridium
diversispinosum
Cordosphaeridium-group
Enneadocysta-group
Cribroperidinium spp.
Operculodinium spp.
Achilleodinium
biformoides
Diphyes/Dapsilidinium
Microdinium reticulatum
Hystrichokolpoma spp.
Spiniferites-group
Batiacasphaera/
Kallosphaeridium
Cerebrocysta/Corrudinium
Impagidinium spp.
Nematosphaeropsis spp.
Other gonyaulacoids
Gonyaulacoids indet
572
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
50 μm
Plate II
12 3
45
6
78
11 12
13
9
10
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 573
Plate II. Microphotographs of organic walled phytoplankton from the middle Eocene–lower Oligocene interval of the Landzhar
section. (1, 2, 3) Glaphyrocysta semitecta, Sample 323; (4, 5) Glaphyrocysta intricata, Sample 1409; (6) Cleistosphaeridium diver-
sispinosum, Sample 1407; (7, 8) Glaphyrocysta semitecta, Sample 1407; (9, 10) Areosphaeridium ebdonii, Sampl e 140 7; (11, 12) Tur-
biosphaera symmetrica, Sample 1403; (13) Glaphyrocysta intricata, Sample 1407.
Eocene dinocyst zones of Western Europe and Peri-
Tethys.
It was recently shown that the species Reticulatos-
phaera actinocoronata first occurs in the Western
Europe (Danish Basin) at the base of nannofossil
NP19/20 Zone (the uppermost part of Enneadocysta
arcuata dinocyst zone; Heilmann-Clausen and Van
Simayes, 2005). However, the results from the
Landzhar section indicate an even earlier FO of this
species: at the end of nannofossil NP17 Zone, at the
CNE16/CNE17–19 Zone boundary, late Bartonian.
It should be emphasizedd that representatives of
the subfamily Wetzelielloideae were found in the
uppermost Priabonian part of the Chimandkend Fm.
(Sample 1518) and identifie d in this paper as Wetze-
liella aff. symmetrica and Wetzeliella aff. gochtii. The
stratigraphic range of Wetzeliella gochtii is discussed
below. Representatives of Wetzeliella symmetrica are
typical of early Oligocene species, although its earlier
FO in the Eocene (Priabonian) has recently been
reported from the Tethyan region (Alano di Piave sec-
tion, Italy; A. Iakovleva, unpublished data). It can be
assumed that specimens found in the uppermost part
of the Chimandkend Fm., being not typical represen-
tatives of the above mentioned two species, are ances-
tral forms which evolved during the early Oligocene.
The palynological assemblage from the lower part
of the Chimandkend Fm. (Bartonian) is characterized
by the common occurence or dominance of dinocysts
(25–55%), consistent occurrence of prasinophytes,
and rather abundant (up to 40%) conifer pollen. The
upper horizons of this formation (Priabonian) exhibit
a marked decrease in abundance of the dinocysts
(from 40 to 25%), sporadic and rare occurrence (up to
5%) of the acritarchs, disappearance of the prasino-
phytes, increase in abundance of the angiosperm pol-
len and terrestrial plant spores, and dominance (up to
70%) of the bisaccate conifer pollen. As regards the
composition of the dinocyst assemblages, the lower-
most part of the Chimandkend Fm. shows a decrease
in the relative abundance of the Spiniferites group (28–
38%), a prominent increase in the relative abundance
of the Areoligera group (~30%), and an increase in the
relative abundance of Impagidinium spp. (up to a few
percent), which may be indicative of a transgression
episode at the onset of deposition of the Chimandkend
Fm. The lower (Bartonian) part of the formation is
characterized by a pronounced dominance of the
Enneadocysta group (40–50%), low relative abun-
dance of peridinioids (deflandroids), consistent
occurrence (20–25%) of the Spiniferites group, and
rare but consistent occurrence of Impagidinium spp.
and Nematosphaeropsis sp. At the same time, the dino-
cyst assemblage from the Priabonian part of this for-
mation is characterized by an increase in the relative
abundance (or dominance, 20–40%) of deflandroids,
Cribroperidinium spp. (up to 18%), and the Areoligera
group (20%), by sporadic and rare occurrence of
Thalassiphora pelagica (10%), by abrupt disappear-
ance of the Enneadocysta group, and by gradual disap-
pearance of the Spiniferites group and rare Impagidin-
ium spp., as well as by absence of Nematosphaeropsis
sp. These changes in the composition of early Pria-
bonian dinocyst assemblages, along with a remarkable
increase in the relative abundance of conifer and
angiosperm pollen and terrestrial plant spores, reflect
possible environmental changes in this part of the
basin: enhanced nutrient supply and freshwater influx
from coastal domains during the sea-level highstands.
The only sample from the base of the Shagap Fm.
(1416) was barren. The palynological assemblage from
the Shagap Fm. (Priabonian–Oligocene) differs a lot
from assemblages detected in the Azatek and Chi-
mandkend Fms. It is characterized by the lowest abun-
dance of dinocysts (from 12% to single specimens),
the occurence of few prasinophytes, and the absence
of acritarchs. The assemblage is dominated by terres-
trial palynomorphs: bisaccate conifer pollen (30–
54%), angiosperm pollen (17–56%), and terrestrial
plant spores (~13–20%). This suggests the dramatic
change in the depositional environment.
Rather abundant dinocyst assemblages were identi-
fied only in Samples 1419 and 1420. They are charac-
terized by the absolute dominance of the peridinioid
species Def landrea phosphoritica (~91%) and the rare
occurrence of gonyaulacoid dinocysts. The domi-
nance of Deflandrea phosphoritica is rather typical for
the late Eocene–early Oligocene dinocyst assem-
blages from lagoonal low-salinity environments and
enhanced terrestrial nutrient supply.
The stratigraphically important species Wetzeliella
gochtii (typical forms) was identified in the Sample
1422, ~5 m above the CNE20/CNE21, CP15/CP16,
and NP19–20/NP21 nannofossil Zones boundaries
(Eocene/Oligocene transition). On the basis of the FO
of this index species in the Landzhar section, we iden-
tified the Wetzeliella gochtii dinocyst zone within the
Shagap Fm. This zone is widely used in many Western
European (Costa and Downie, 1976; Châteauneuf
and Gruas-Cavagnetto, 1978; Powell, 1992) and
Ukrainian and Russian (Andreeva-Grigorovich et al.,
2011) zonations. It should be noted that the FO of
574
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Plate III
50 μm
1
2
3
5
6
4
7
9
8
12 13 14 15
11
10
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 575
Plate III. Microphotographs of organic walled phytoplankton from the middle Eocene–lower Oligocene interval of the Landzhar
section. (1, 5) Rhombodinium draco, Sample 1407; (2) Petalodinium rhomboideum, Sample 1404; (3, 4) Cooksonidium capri cor-
num, Sample 1411-1; (6) Thalladinodinium? clathratum, Sample 323; (7, 10, 11) Cooksonidium capricornum, Sample 1411-E;
(8) Achilleodinium biformoides, Sample 1403; (9) Charlesdowniea? rotundata, Sample 1407; (12) Impagidinium brevisulcatum,
Sample 1403; (13, 14, 15) Cooksonidium capricornum, Sample 1411-1.
Wetzeliella gochtii is referred at the base of nannofossil
NP23 Zone (Andreeva-Grigorovich et al., 2011; Van-
denberghe et al., 2012). There are, however, alterna-
tive observations for the FO of Wetzeliella gochtii. For
example, the results of Brinkhuis (1994) show that the
species Wetzeliella gochtii first occurs within nanno-
fossil NP21 Zone (early Oligocene). According to
Gedl (2004, 2005), Wetzeliella gochtii first occurs in
the late Eocene in the sections of the Polish Carpath-
ians (terminal part of nannofossil Zone NP19/20).
Note that the latest occurrence of this index species
was reported in areas of northwestern Europe and the
North Atlantic, where dinocysts are often absent in the
Eocene/Oligocene transition interval (Châteauneuf
and Gruas-Cavagnetto, 1978; Costa and Downie,
1976; Manum et al., 1989).
DISCUSSION AND CONCLUSIONS
A detailed study of nannofossils and palynomorphs
from the middle Eocene–early Oligocene interval of
the Landzhar section allowed revelation and direct
correlation of the first and last occurence datums (bio-
events) of stratigraphically important species from
both groups. The studied part of the section contain-
ing nannofossils and dinocysts spans the interval from
the top of the middle Eocene (Bartonian) to the base
of the Oligocene. Our results show that the Azatek Fm.
corresponds to the Bartonian, which confirms the
previous conclusions based on nummulitids, as was
accepted in the regional stratigraphic scheme of
Armenia (Sarkisyan et al., 2006). The Nummulites
maximus Horizon at the base of the overlying Chi-
mandkend Fm. corresponds to the upper Bartonian
Subzone of the larger foraminiferal scheme and is
placed in the lower Priabonian of the recent geologic
timescale (Vandenberghe et al., 2012). However, the
placement of the Bartonian–Priabonian (mid-
dle/upper Eocene) boundary in the lower part of the
Chimandkend Fm. remains a matter of discussion. In
the Alano section (Italy), currently accepted as a can-
didate for the GSSP of the Bartonian/Priabonian
stage boundary, the transitional interval between these
two stages is defined by the first rare occurrence of
Chiasmolithus oamaruensis, the LO of C. grandis, and
the base of C. erbae acme (Agnini et al., 2011). In the
Landzhar section, the only indication of such a transi-
tion is the appearance of C. oamaruensis directly above
the N. maximus Horizon; C. grandis has later LO in
this section, whereas C. erbae has no common occur-
rence throughout the section. For this reason, the
boundary between the Bartonian and Priabonian
stages still remains an interval of uncertainty.
The results of the nannofossil and palynomorph
study indicate considerable variation in water depths
and hydrodynamic conditions in the basin. The Aza-
tek Fm. appears to represent the deepest and/or off-
shore environment, containing relatively abundant but
less diverse nannofossil assemblage and taxonomically
diverse dinocyst assemblage. These could accumulate
in the outer neritic zone. The upper part of the Azatek
Fm. is characterized by significant variations in the
relative abundance of dinocysts and prasinophytes and
different ecological groups of dinocysts (prominent
increases in abundance of Achilleodinium biformoides,
Enneadocysta, and Spiniferites). Its sediments were
more likely accumulated in the shelf zone under highly
variable hydrological conditions (salinity variations or
changes in other poorly understood parameters).
The Chimandkend Fm. was more likely accumu-
lated in a shallow-water neritic environment, as indi-
cated by the presence of various species of Pontos-
phaera in the nannofossil assemblages and the domi-
nance of dinocysts in palynomorph assemblages from
the lower part of the formation (the occurence of rare
Nematosphaeropsis sp.). A minor change in the sedi-
mentary setting is suggested in the upper half of the
Chimandkend Fm., as indicated by a decrease in
abundance of dinocysts (from 40% and below), an
abrupt increase in abundance of bisaccate conifer pol-
len, and the extinction of prasinophytes. This seems to
reflect the onset of a shallowing of the basin.
The formation of the lower part of the Shagap For-
mation was probably accompanied by a progressive
shallowing of the basin, accumulation of silty and
sandy material, a decrease in the nannofossil abun-
dance, and the absence of marine organic walled phy-
toplankton. The relative increase (20%) in dinocyst
abundance in the assemblage prior to the Eocene/Oli-
gocene transition may be indicative of a minor and
short-term transgression pulse, whereas the absolute
dominance of Deflandrea phosphoritica in the dinocyst
assemblage can associate with the low-salinity condi-
tions in this part of the basin (proximity to estuaries?).
The virtual absence of dinocysts in the Oligocene pal-
ynomorph assemblages indicates a significant change
in the sedimentary settings of southern Armenia, i.e.,
a transition from marine and lagoonal–estuarine to
continental environments.
The results of our study enabled the more accurate
definition of nannofossil zonal boundaries in terms of
576
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
Plate IV. Microphotographs of organic walled phytoplankton from the middle Eocene–lower Oligocene interval of the Landzhar sec-
tion. (1, 5, 12) Areosphaeridium diktyoplokum, Sample 1407; (2, 3) Hystrichokolpoma pusilla, Sample 1403; (4) Thalassiphora fenestrata,
Sample 1403; (6, 8, 10) Enneadocysta pectiniformis, Sample 1407; (7, 9) Wetzeliella aff. gochtii, Sample 1518; (11) Wetzeliella aff. gochtii,
Sample 1518; (13) Wetzeliella sp., Sample 1518; (14 ) Enneadocysta sp. C in Stover et Williams (2001), Sample 1405.
50 μm
Plate IV
1
2
3
7
9
6
8
5
10
11
14
13
12
4
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
MIDDLE EOCENE TO EARLY OLIGOCENE NANNOFOSSILS AND PALYNOMORPHS 577
Plate V. Microphotographs of organic walled phytoplankton from the middle Eocene–lower Oligocene interval of the Landzhar section.
(1, 2) Rhombodinium? aidae, Sample 1403; (3) Deflandrea phosphoritica, Sample 323; (4, 5) Thalassiphora gracilis, Sample 1407; (6) Heteraula-
cacysta leptalea, Sample 323; (7) Areosphaeridium diktyoplokum, Sample 323; (8) Wetzeliella gochtii, Sample 1422; (9) Aquatic palynomorph 2,
Sample 1407; (10) Aquatic palynomorph 2, Sample 1407; (11, 12) Hystrichokolpoma pusilla, Sample 1403; (13) Operculodinium eisenackii, Sample
323; (14) Wetz el iella aff. symmetrica, S ample 1518; (15) Aqu atic pal yno morph 1, Sample 14 04 ; (16 ) Impagidinium pallidum, Sample 1414.
Plate V
50 μm
12 3
45
6
9
11
10
14
13
12
15 16
78
578
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 25 No. 5 2017
SHCHERBININA et al.
the most recent knowledge about the nannofossil bio-
events and their direct correlation to dinocyst bioev-
ents in the southern Armenian basin. However, dia-
chroneity of the middle–late Eocene nannofossil and
dinocyst bioevents in different basins and uncertainty
in the Bartonian/Priabonian (middle/upper Eocene)
boundary do not let reliable definition of this bound-
ary in any individual section.
ACKNOWLEDGMENTS
We are grateful to M.A. Akhmetiev, A.Yu. Gladen-
kov, and Yu.B. Gladenkov for careful reading of the
paper and fruitful discussion; G.N. Aleksandrova
(Geological Institute, Russian Academy of Sciences)
for chemical preparation of samples for palynological
analysis; F.A. Airapetyan and A.G. Israelyan (Institute
of Geological Sciences, National Academy of Sci-
ences of the Republic of Armenia) for their assistance
with field work; and A.S. Karakhanyan, director of the
Institute of Geological Sciences, National Academy of
Sciences of the Republic of Armenia, and the insti-
tute’s staff for arrangement of field work. We also
thank S.M. Mironov, leader of the party A Just Russia,
for financial support of the 2014 field trip.
This study was supported by the Russian Founda-
tion for Basic Research (project nos. 15-55-05102 and
15-05-07556). The study of nannofossils and palyno-
morphs was performed as part of the government con-
tracts with the Geological Institute, Russian Academy
of Sciences (project nos. 0135-2014-0070,
01201459195, and 0135-2016-0001).
Reviewers M.A. Akhmetiev,
A.Yu. Gladenkov and Yu.B. Gladenkov
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Translated by N. Kravets
