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The area under study belongs to the Armenian part of the Armenian volcanic Highland. Previous investigations (Milanovsky, 1968; Trifonov et al., 2014, 2016; Trifonov, 2016) revealed that mountain systems of the Arabia-Caucasus region as well as other segments of the Alpine-Himalayan Belt rose significantly and rapidly during the Late Miocene and particularly the Pliocene and Quaternary. Intermountain and surrounding basins were partly involved into the uplift and partly subsided within a short period of time (Trifonov et al., 2012a; Trifonov, 2016). The origin of many of these basins was related to the Late Cenozoic fault motions and other manifestations of the collisional plate interaction (Trifonov et al., 2017). At the same time, some basins of the Armenian volcanic Highland do not demonstrate apparent relations to the collisional faulting. Milanovsky (1968) attributed their origin to transformations in deep layers of the lithosphere expressed in volcanism. The present paper is devoted to examination of this hypothesis through the example of the Shirak Basin in NW Armenia. New data on stratigraphy and age of the Shirak Basin Quaternary cover as well as its tectonic deformation and correlation with surrounding volcanism are represented. The origin of the basin is discussed with account of new data.
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Quaternary International
journal homepage: www.elsevier.com/locate/quaint
Quaternary geology and origin of the Shirak Basin, NW Armenia
E.A. Shalaeva
a,
, V.G. Trifonov
a
, V.A. Lebedev
b
, A.N. Simakova
a
, A.V. Avagyan
c
, L.H. Sahakyan
c
,
D.G. Arakelyan
c
, S.A. Sokolov
a
, D.M. Bachmanov
a
, A.A. Kolesnichenko
a
, A.V. Latyshev
d,i
,
E.V. Belyaeva
e
, V.P. Lyubin
e
, P.D. Frolov
a,h
, A.S. Tesakov
a
, E.K. Sychevskaya
f
, G.V. Kovalyova
g
,
M. Martirosyan
c
, A.I. Khisamutdinova
a
a
Geological Institute of the Russian Academy of Sciences (GIN RAS), 7 Pyzhevsky, Moscow, 119017, Russia
b
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences (IGEM RAS), 35 Staromonetny, Moscow, 119017,
Russia
c
Institute of Geological Sciences of the National Academy of Sciences of Republic of Armenia, 24a Marshal Baghramyan Ave., Yerevan 0019, Armenia
d
Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences (IPE RAS), 10-1 Bolshaya Gruzinskaya Str., Moscow, 123242, Russia
e
Institute of History of Material Culture of the Russian Academy of Sciences (IHMC RAS), 18 Dvortsovaya Naberezhnaya, St. Petersburg, 191186, Russia
f
Borissiak Palaeontological Institute of the Russian Academy of Sciences (PIN RAS), 123 Profsoyuznaya Str., Moscow, 117647, Russia
g
Institute of Arid Zones, Southern Scientific Centre of the Russian Academy of Sciences (IAZ SSC RAS), 41 Chekhov Str., Rostov-on-Don, 344006, Russia
h
Laboratory of Macroecology and Biogeography of Invertebrates, Saint-Petersburg State University, 7/9 Universitetskaya Emb., St. Petersburg, 199034, Russia
i
Laboratory of Applied Geodynamics, Geological Department, Lomonosov Moscow State University, 1, Leninskie Gory, Moscow, 11991, Russia
1. Introduction
The area under study belongs to the Armenian part of the Armenian
volcanic Highland. Previous investigations (Milanovsky, 1968;Trifonov
et al., 2014,2016;Trifonov, 2016) revealed that mountain systems of
the Arabia-Caucasus region as well as other segments of the Alpine-
Himalayan Belt rose significantly and rapidly during the Late Miocene
and particularly the Pliocene and Quaternary. Intermountain and sur-
rounding basins were partly involved into the uplift and partly subsided
within a short period of time (Trifonov et al., 2012a;Trifonov, 2016).
The origin of many of these basins was related to the Late Cenozoic
fault motions and other manifestations of the collisional plate interac-
tion (Trifonov et al., 2017). At the same time, some basins of the Ar-
menian volcanic Highland do not demonstrate apparent relations to the
collisional faulting. Milanovsky (1968) attributed their origin to
transformations in deep layers of the lithosphere expressed in vol-
canism. The present paper is devoted to examination of this hypothesis
through the example of the Shirak Basin in NW Armenia. New data on
stratigraphy and age of the Shirak Basin Quaternary cover as well as its
tectonic deformation and correlation with surrounding volcanism are
represented. The origin of the basin is discussed with account of new
data.
In the paper we use the stratigraphic division of the Neogene and
Quaternary confirmed at the 33rd IGC and the following abbreviations:
N
13
– Late Miocene, N
21
– Early Pliocene, N
22
– Late Pliocene, Q
11
Gelasian, Q
11−2
ol – Oldovai subchron, Q
12
– Calabrian, Q
21
– earliest
Middle Pleistocene (≥0.5 Ma), Q
4
– Holocene, a.s.l. – above sea level,
DEM – Digital Elevation Model, GPa – gigapascal, H – altitude a.s.l., km
– kilometre, IGRF - International Geomagnetic Reference Field, L –
layer, Ma – million years, m – metre, mT – millitesla, N – normal
magnetic polarity, PC – pollen complex, R – reverse magnetic polarity,
SRTM – the Shuttle Radar Topography Mission, s – site, t – temperature.
Names of geographic objects used in Armenia before the 1990s are
given in square brackets.
2. Regional setting
The Shirak Basin is situated at altitudes between 1500 and 1700 m
a.s.l. Most of the basin infill consists of Quaternary terrigenous sedi-
ments and volcanic rocks. From north to south the basin is drained by
the Akhuryan River which incises into the basin flat surface up to
several tens of meters. The average height of the adjacent ridges varies
within 2000–2500 m (Figs. 1 and 2). The northern part of the basin is
bounded by the western chain of the Bazum Ridge and its southern
branch, the Shirak Ridge. These ridges are composed of Paleogene,
Cretaceous and Jurassic rocks with fragments of the Meso-Tethys su-
ture, which is considered to be a western continuation of the Sevan-
Hakari ophiolite zone (Rolland et al., 2009;Sosson et al., 2010;Adamia
et al., 2011). The eastern part of the basin is bounded by the Pambak
Ridge, which separates it from the Sevan Basin. The eastern and central
parts of the ridge are composed mainly of the Eocene rocks with a large
portion of lavas and volcanoclastic sediments (Gabrielyan, 1964;
Djrbashyan, 1990). In the vicinity of the town of Spitak and near the
Shirak Basin, Cretaceous rocks in southern Tethys facies (Aslanyan,
1958) and Late Cenozoic andesites and basalts are exposed. The
southern side of the Shirak Basin does not have a prominent structural
https://doi.org/10.1016/j.quaint.2018.09.017
Received 7 May 2017; Received in revised form 6 June 2018; Accepted 12 September 2018
Corresponding author.
E-mail address: es-geo@mail.ru (E.A. Shalaeva).
Quaternary International 509 (2019) 41–61
Available online 18 September 2018
1040-6182/ © 2018 Elsevier Ltd and INQUA. All rights reserved.
T
boundary. However, it can be marked by the Aragats volcanic center
which was active nearly since 1.0 to 0.45 Ma (Chernyshev et al., 2002)
and by relics of the older rhyolite-dacite Arteni volcano (Lebedev et al.,
2011). The southernmost point of the basin is found near the village of
Haykadzor and the medieval city of Ani. Its south-western border is
formed by the Upper Miocene and Pliocene volcanic rocks of the Ani
area. In the west the basin is bounded by the volcanic Kars-Digor
Highland, consisting of the Late Miocene to Pleistocene lavas and tuffs
of different composition.
The region underwent intense folding and faulting during the
second part of the Eocene and Oligocene. The Lower and Middle
Miocene geological formations are almost not exposed in the area, al-
though the Lower Miocene alkaline basalts at the Jajur Pass and the
uppermost Oligocene basaltic andesites in the south of the basin are
found. We determined their age by KeAr dating (samples 2014–220,
2016–431/2, 2016–431/3, 2016–431/4 in tables B.1, B.2, and B.3 and s
220 and s 310 in Figs. 1 and 2). Volcanic rocks of the same age are also
found on the adjacent Kars-Digor Highland.
3. Methods
A suite of methods was used to study the geology of the Shirak
Basin. They are as follows: description of sedimentary sections, geo-
morphological study, analysis of remanent magnetic polarity, litholo-
gical and petrochemical correlation of rocks, KeAr dating of tuffs and
lavas and palaeontological studies.
Geomorphological study included recognition of different topo-
graphical levels and definition of their relationships with lithological
units, construction of altitudinal profiles across the basin and the ad-
jacent territory, calculation of the fluvial gradients of the Akhuryan
river channel. We consider all the altitudinal estimates to be better than
5 m. This accuracy was attained by using the GPS data, the 3 arc-sec-
onds DEM provided by SRTM as well as trig points.
Palaeomagnetic samples were taken as hand blocks and oriented
using a magnetic compass. The average interval between the samples
was 0.3–0.6 m. In total 197 samples from 11 locations were analyzed.
Laboratory studies were performed by A. Latyshev. The local magnetic
declination was calculated using the IGRF model. The palaeomagnetic
procedures were performed in the Palaeomagnetic laboratory of the IPE
RAS. All the samples were subjected to the stepwise alternating fields
(AF) demagnetization up to 130 mT with the AF-demagnetizer inbuilt
in the 2G Enterprises cryogenic magnetometer. The remanent magne-
tization of samples was measured using the 2G Enterprises cryogenic
magnetometer “Khramov”. The isolation of the natural remanent
magnetization (NRM) components was performed with Enkin's (Enkin,
1994) palaeomagnetic software package using principal component
analysis (Kirschvink, 1980). The quality of palaeomagnetic signal varies
from sample to sample. Nevertheless, about 80% of the studied samples
were suitable to isolate the palaeomagnetic directions. In other cases
the behavior of NRM vector during the demagnetization is irregular.
Fig. 1. Topography and drainage system in NW Armenia with sites of observation.
(AL) Arailer Volcano, (AM) Amasya Basin, (BP) Bartsrashen Plateau, (DA) depression of Mada Lake and Dalichay River, (Jp) Jajur Pass, (Kp) Karakhach Pass, (Le)
Lermontov Sowneck, (Mr) village of Marmashen, (Sr) village of Shirak, (UA) Upper Akhurian Basin, (UP) Upper Pambak Basin.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
42
However, in some samples the vectors of NRM are located in the same
hemisphere after all demagnetization steps, and we were able to de-
termine the magnetic polarity.
KeAr dating of 28 samples was performed by V.A. Lebedev in the
Isotopic geochemistry and geochronology Laboratory of the IGEM RAS.
All the measurements of radiogenic Ar were conducted on the base of
MI-1201 IG noble gas mass spectrometer.
Molluscs were found in four sections: Voghji (5 samples), Haykavan
(1 sample), Lusaghbyur (3 samples) and Haykadzor (3 samples). In total
several thousand shells were collected, most of which were found at
Voghji and Haykadzor sections. About 50 shells were collected from
both Haykavan and Lusaghbyur sections. In total about 100 kg of se-
diments were washed and sifted.
The collection of palaeontological material was carried out both by
direct selection from the section (large and/or brittle shells and bones
were immediately glued at the outcrop and packed to prevent damage
during transportation), and by dry sieving and washing through sieves
with cell size 0,7 and 0,5 mm. The washed samples were dried up. The
remaining concentrate was divided into fractions from which pa-
laeontologically significant material (mollusks, small vertebrate bones,
etc.) was selected. Small gastropods were collected by flotation method:
after washing the sieve was half-submerged in water, and small, light
and undamaged shells floated up. This technique was used to collect
material from the Voghji section.
Pollen spectrum was studied from the Voghji and Haykavan sec-
tions. In total 26 samples were examined. Samples taken in the Jradzor,
Meghrashat, Lusaghbyur and Gyumri Airport outcrops appeared to be
with negligible amount of grains or barren. Probe maceration was
performed by the method adopted in GIN RAS, which is a modification
of the Grischuk's separation method (Grichuk and Zaklinskaya, 1948),
namely, the samples were additionally treated by sodium pyropho-
sphate and hydrofluoric acid. Pollen diagrams were constructed in Tilia
1.5.12 program, which allows to calculate the general spectrum (ar-
borescent pollen + nonarborescent pollen + spores = 100%) and in-
dividual components as a portion of the total amount of grains.
Relationships between the basin structure and volcanic activity and
the Late Cenozoic fault system caused by the collisional interaction of
the lithospheric plates and blocks were studied as well.
Some archaeological finds also contributed to investigation, de-
fining the probable lower time limit on the age of the deposits.
4. Results of the studies
4.1. Geological results
Alluvial and lacustrine sediments as well as volcanic rocks of the
Upper Miocene, Pliocene, Gelasian, Calabrian and Middle Pleictocene
are recognized within the area under study. The description of the
Fig. 2. Geological map of NW Armenia with main sites of observation, after (Nalivkin, 1976;Trifonov et al., 2016) with additions. (1) Quaternary sedimentary
deposits; (2) rocks of the Aragats volcano (1.0–0.4 Ma); (3) rocks of the Mets-Sharailer Volcano (∼0.9 Ma), the Arailer and Arteni Volcanoes (∼1.35–1.0 Ma), and the
V unit of andesites and trachiandesites of the Javakheti Ridge (∼1.7 Ma); (4) the IV dacite unit of the Javakheti Highland (∼1.8–2.0 Ma); (5) the III unit of andesites
and trachiandesites of the Javakheti Highland (∼1.8–2.0 Ma); (6) basic lavas of the II unit (∼2.0–2.5 Ma); (7) the Pliocene I unit of the basic to acid volcanic rocks in
the south-western Javakheti Highland and the Messinian and Pliocene volcanic rocks in the Ani area; (8) Upper (probably) Miocene; (9) Paleogene (mainly Eocene);
(10) Cretaceous; (11) Jurassic; (12) Mesozoic ophiolits and ultramafic rocks; (13) Paleozoic and Precambrian; (14) faults and flexure-fault zones. (EA) the eastern
strand of the East-Anatolian fault zone; (JF) the Javakheti Fault; (PS) the Pambak-Sevan-Syunik fault zone. See other symbols in Fig. 1.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
43
studied sites is given below. KeAr ages and chemical composition of
volcanic rocks is given in Appendix B (Tables B.1, B.2, and B.3). The
altitude of the described sections (Н) is given for top surfaces.
4.1.1. Upper Miocene, pliocene, and gelasian
The Upper Miocene is represented by the volcanic Goderdzi
Formation (∼7.5 Ma; Lebedev et al., 2008,2012) in the western margin
of the Javakheti Highland. The Upper Miocene lavas were described
also to the east of the Shirak Basin (Karapetian et al., 2001). Several
tens of meters thick volcanic-terrigenous breccia is exposed near/on the
southern border of the Shirak Basin (s 310). The same rocks of several
hundred meters thick were drilled within the basin. The breccia is
considered to be an analog of the Voghchaberd Unit with a probable
Messinian age (Sayadyan, 2009). Our studies of the breccia in s 310
revealed that its matrix is tuffaceous and hydrothermally reworked.
Four KeAr dates were obtained for the breccia (see table B.1, №
2016–431/1, 431/2, 431/3, 431/4). On account of a large portion of
atmospheric
40
Ar in the sample 2016–431/1, the obtained age of
1.6 ± 0.7 Ma should be used with caution. The ages of the andesitic
fragments (24.4 ± 0.6 Ma – 24.8 ± 0.7 Ma) can be recognized as the
lower limit on the age of the breccia.
We subdivide the volcanic sequence near the medieval town of Ani
into three parts: the “upper basalt” (UB in Fig. 3), tuff unit, and the
“lower basalt” – several flows of weakly alkaline basaltic andesite (LB in
Fig. 3). The upper layer of the LB has the KeAr age of 5.8 ± 0.2 Ma
(2016–429/1 in table B.1). Southward of the village of Haykadzor the
same basaltic andesites compose a small cone of the Qurtblur [Kurt-
tepe] volcano with KeAr ages of 5.60 ± 0.15 Ma in the cone and at the
base (2016–420/1 and 2016–421 in table B.1). In the southern part of
the Haykadzor village (s 417) the upper layer of the LB has the age of
4.26 ± 0.12 Ma. Thus, according to KeAr dating the age of LB varies
within 5.8 ± 0.2 Ma – 4.26 ± 0.12 Ma, however, the lower portion of
the lavas may be older. According to Chernyshev et al. (2002) the KeAr
age of the UB in the Ani section is 2.5 ± 0.2 Ma. Averaging a series of a
repeated KeAr measurements of the same sample 1/A, V.A. Lebedev
obtained more precise age of 2.64 ± 0.10 Ma. The tuff unit between
the UB and LB is composed of rhyolitic lithic tuffs and pumice and
spreads within the territory of the medieval Ani, Anipemza village, and
Ani station (for KeAr ages and chemical composition see tables B.1,
B.2, and B.3).
Sayadyan (2009) represented the drilling data on the fine-grained
lacustrine Akchagyl deposits (Upper Pliocene and Gelasian) up to 550 m
thick in the northern part of the Shirak Basin and grounded this age on
the finds of the Lower Akchagyl fresh water molluscs in the lower part
of the unit. This unit is considered to be the earliest evidence of the
basin subsidence.
The oldest exposed formation of the northern part of the basin
consists of basaltic trachiandesite in the Akhuryan River valley. The
lava flows spread to the northern part of the Shirak Basin from the
southern slopes of the Javakheti Highland or the Upper Akhuryan
Basin.
40
Ar/
39
Ar date from the Amasia Basin (2.09 ± 0.05 Ma; Ritz
et al., 2016) and our KeAr dates from s 208 and s 340 (2.3–2.0 Ma,
table B.1) confirm the Gelasian age of lavas. Their thickness reaches
90 m in the Gyumri [Leninakan] borehole (Sayadyan, 2009).
4.1.2. Calabrian and Middle Pleistocene sedimentary sections
The stratigraphically higher part of the Shirak Basin section is
composed of terrigenous and tuffaceous deposits. Sayadyan (1972,
2009) described a coarse-grained formation along the northern border
of the basin and supposed that it could belong to the Calabrian. Within
Fig. 3. Akhuryan River valley near the medieval town of Ani. Thickness of the acid tuff layer between the Upper basaltic trachandesite (UB) and the Lower basic lavas
(LB) increases to the east in the Armenian territory. Photo by V.A. Lebedev.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
44
the lacustrine formation he distinguished the lower and the upper units
and named them Ani and Arapi, respectively. Basing on palaeontolo-
gical finds, Sayadyan dated the Ani unit as of the lower Middle Pleis-
tocene and the Arapi unit as of the middle Middle Pleistocene. He
correlated the Leninakan assemblage of large mammals found in the
Arapi unit with the Singil fauna of the Lower Volga River region. We
subdivide the Calabrian and Middle Pleistocene deposits of the Shirak
Basin into the Karakhach, Ani and Arapi units. All the outcrops are
described from top downwards (for a better comparison with drill core
descriptions). Altitudes are given for the section top surfaces. GPS co-
ordinates for the sites are given in Appendix B (Table B.4).
4.1.2.1. Karakhach unit. The Karakhach unit is exposed only within the
northern rim of the basin. The most complete outcrop was found to the
south of the village of Jradzor (Fig. 1, s 226, 227; Fig. 4, s 226). Another
outcrop was studied to the north-east of the village of Meghrashat
Fig. 4. Stratigraphic sections of the Karakhach unit. Position of the sections is shown in Fig. 1 and 2. (L) number of layer, (M) magnetic polarity.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
45
(Fig. 4, s 306).
In s 226 (H = 1770 m), 1-m trachyte welded tuff (ignimbrite), the
so-called Leninakan tuff, with N polarity covers fluvial conglomerates
of 11–12 m thick with lenses of sand and silt with R polarity. Most of
the underlying silts (L 2–4) also demonstrated R polarity, whereas se-
diments at the base of the outcrop showed N polarity (in total 14
samples were taken).
Sediments in s 226 and s 227 dip with a few degrees to the west.
Gelasian basaltic trachiandesites are exposed 10–15 m below the
Karakhach unit in s 226.
The s 306 section (H = 1750 m) is represented by the alluvial
coarse-grained sediments in the upper part. Small pebbles consist pri-
marily of basalts and andesites as well as rhyolites, jasper, and radi-
olarites in minor amounts. Underlying lacustrine sediments (L 2–4)
with horizontal bedding are constituted by silt and fine-grained sand in
the upper part, and clay and loam in the lower part. Except the low-
ermost portion with N polarity practically all the sediments have R
polarity (in total 11 samples were taken).
The thickness of the Karakhach unit is estimated up to 20 m.
4.1.2.2. Ani unit. The stratotype of the Ani unit was described in the
borehole 6 near the village of Marmashen (Zaikina et al., 1969a)
(Fig. 5). The top of the borehole was at 1630–1640 m a.s.l., the bottom
– at 1480–1490 m a.s.l. For the purpose of our study the most essential
is that the alluvial layer 8 can possibly belong to the Karakhach unit. At
s 340 (Fig. 1; H = 1514 m), sediments similar to borehole layers 4 and 7
are exposed. They rest above basaltic trachyandesite in the Akhuryan
River channel with KeAr age of 2.25 ± 0.10 Ma (table B.1, 2015–340).
Alluvial layer 8 of the borehole 6 is hypsometrically lower than basaltic
trachiandesites of s 340, at 1480–1490 m a.s.l. against 1515 m a.s.l.
Thus, the alluvium possibly belongs to the buried valley incised into the
lava surface.
We have described several new outcrops with layers correlatable
with those of the borehole 6 and thus traced them over the area under
study (Fig. 5).
The s 209 section (H = ∼1700 m) near the village of Kaps is the
smallest outcrop described for the Ani unit. The Leninakan tuff (4 m)
covers the 5.4–5.6 m thick alluvial sediments which become finer
downwards. The lowermost 0.5 m of the deposits have R polarity and
the major part of sediments have N polarity (in total 10 samples were
taken). The deposits are underlain by basaltic trachiandesites with
KeAr date 2.1 ± 0.2 Ma (2014–208 in table B.1). Basaltic trachyan-
desites cover the Eocene porphyrites and deformed fine-grained sand-
stones.
The thickness of the Ani unit increases to the south within a short
distance and reaches 15–20 m near the Leninakan hydro-electric power
plant (HPP, s 208; H = 1665 m).
Rocks and sediments of s 339 (H = 1634 m) constitute a scarp near
the Marmashen monastery. They differ from borehole 6 by the in-
creased thickness of the Leninakan tuff (20–25 m) and the presence of
redeposited pumice (25–30 m) of sand and gravel size under it (the
same pumice forms a landslide on the opposite bank of the Akhurian
River). Olive-coloured clays are similar to borehole layers 4, 5, 7 but
their thickness is nearly twice lower than in the borehole, 65 m against
114 m. The lowest part of the scarp is covered with talus and monastery
cultural sediments and thus has no access. The Gelasian basaltic tra-
chyandesites up to 2 m thick are exposed in the Akhuryan River channel
directly below the monastery.
Like previous sites, the s 326 section (H = 1610 m) near the Voghji
[Okhchogli] village starts from the dark-grey Leninakan tuff (L 1).
Below the tuff, alluvial coarse-to fine-grained sediments are exposed
with intrastratal deformations, possibly seismites, at the middle part of
the layer. Sands are enriched with shell fragments (L 2). The rest 47 m
are represented by massive clays brown-grey or olive-green with a 4 m
interbed of diatomite (L 6) or thinner interbeds of diatomic clays (L 3, 5,
8, 9) and rare interbeds of fine-grained tuffaceous sandstone. Some
interbeds are enriched with freshwater shell fragments (L 3, 4, 5, 8) or
well-preserved mollusc shells (L 6). Diatomite of L 6 has intense in-
trastratal deformations (seismites) (Fig. 6). Regarding the results of
palaeomagnetic sampling of clays 4 alternating intervals of N and R
polarity are clearly distinguished (in total 52 samples were taken).
The s 336 section (H = ∼1600 m) near the Haykavan village has
the following structure. The dark-grey Leninakan tuff covers a sequence
of alluvial sediments with lacustrine sediments at the base of the out-
crop. Alluvial sediments in L 2–5 are represented by alternating layers
of loam, sandy loam or silts (probably flood plain deposits) and pebble
or gravel beds. The upper parts of the fine-grained sediments are altered
by the processes of pedogenesis. Shell fragments are found in sand
lenses of L 5. L 6 and L 7 are represented by clays brown or olive-green
and are subdivided on the basis of different polarity – primarily R po-
larity for L 6, N polarity for L 7. An interbed of volcanic ash (5–7 cm) is
found in L 7. L 8–10 are represented by pebble, gravel, and sands (the
material becomes finer downwards) with horizontal or cross bedding.
At the very bottom lacustrine clays of light-brown, bluish-grey, olive-
green, brownish-grey colours with a thin interbed of volcanic ash are
found. Shell fragments are concentrated in lenses and interbeds up to
5 cm thick. Rare and very-well preserved bone fragments of large
mammals are found. In total 38 samples for palaeomagnetic studies
were taken in the fine-grained sediments.
Like the Karakhach unit sites, all the Ani unit sites demonstrate the
presence of the alluvial sediments in the upper parts and lacustrine
sediments below the alluvium. The key issue is that these sites differ in
proportions between alluvial and lacustrine sediments and, thus, may
represent different parts of the same lake, which once existed in the
area.
4.1.2.3. Arapi unit. The type section of the Arapi unit is exposed near
the village of Arapi above the Akhuryan River (40º46.443′N,
43º48.369′E). The unit composes a terrace with top surface at 1550 m
a.s.l. The water edge below the village is 1475 m a.s.l. Thus, the total
apparent thickness of the unit is not more than 75 m. Agadjanyan and
Melik-Adamyan (1985) described the unit as shown on Fig. 7, s 337. We
described several new sections of the unit (Fig. 7).
The s 336a section near the village of Haykavan is represented
primarily by sediments of lacustrine origin, namely, alternating
brownish-grey silts and fine-grained well-sorted sands with seismits in L
3, and silt and brown loam with a volcanic ash interbed (L 4) at the base
of the outcrop. Most of the palaeomganetic samples showed N polarity
(in total 15 samples were taken).
The s 341 section (H = 1516 m) described in a quarry near the
Gyumri Airport is composed of alluvial sediments solely and is covered
with the Leninakan tuff and some loam and recent soil at the top. It is
represented by an alternation of layers of coarse-grained cross-bedded
and fine-grained sediments with nearly equal thicknesses. The upper
parts of fine-grained sediments are altered by the processes of pedo-
genesis. Seismites in the upper part of L 6 are clearly distinguished
(Fig. 6). The origin of the greenish-grey clays at the base is not clear as
only a top part of the layer is exposed. It could be either lacustrine or
alluvial (flood plain). Most of the palaeomagnetic samples showed N
polarity (in total 7 samples were taken).
Another quarry was studied by Melik-Adamyan (1994) near the
Gyumri Airport, 2.5 km to the south-east of the city center
(H = 1520 m). Its lithology is similar to s 341 as well as similar rodent
fauna was found in sands 1–1.5 m above and beneath the tuff. Identical
rodent fauna was found in the southern part of Gyumri (Kazachiy Post
section) at the depth of 8 m below the surface (Agadjanyan and Melik-
Adamyan, 1985). The fauna was buried within a 4.5 m thick clay layer
covered with gravels and sands (4–5 m) and the Leninakan tuff.
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Fig. 5. Stratigraphic sections of the Ani unit. See Fig. 4 for symbols. Position of sections is shown in Fig. 1 and 2.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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The s 219 section (H = 1706 m), the second terrace of the Jajur
River near the eponymous village is composed of 2.5 m thick gravels
and sands with a carbonated paleosol horizon in the upper part and
more than 8 m of loam and silts with horizontal bedding and N mag-
netic polarity in the lower part.
The s 438 section (H = 2042 m) in front of the northern slope of the
Aragats volcano near the village of Hnaberd is composed primarily of
alternating horizontally bedded sands, gravel and poorly to well-
rounded pebbles with thin interbeds of ash and caliche beneath recent
soil. Pebbles consist mostly of andesite and dacite.
The s 317 (H = 1513 m) Lusaghbyur section exhibits lacustrine se-
diments covered with the Leninakan tuff with the KeAr age of
0.70 ± 0.03 Ma (2015–317/u in table B.1). Light-brown-grey clay,
light-brown diatomite and greenish-grey clayish diatomite with ad-
mixture of volcanic glass (ash) and an interbed of volcanic ash alternate
successively from top down. 16 samples for palaeomagnetic study were
taken.
The s 314 section (H = 1495 m) on the terrace of the Magaridzor
stream, 2 m thick boulder and pebble layer covers a 4 m light-brownish-
grey lacustrine fine-grained sand and clayish silt layer. They are car-
bonated in the upper part and form sandy travertine. The section covers
probably the carbonated weathered surface of the Voghchaberd unit
exposed further east (s 310).
The s 318 (H = 1489 m) Haykadzor outcrop on the left bank of the
Akhuryan River is composed of lacustrine sediments and is likely to be
the richest in shell fragments and remains of small mammals among all
other sites of the unit. Lithologically from top down it is composed of
travertine, fine-grained well-sorted sands, silts and clayish diatomites.
The section bottom is nearly 5 m higher than the Lower Pliocene ba-
saltic trachiandesite surface. 20 samples for palaeomganetic study were
taken.
Palaeomagnetic samples of all the sites showed the predominance of
N polarity (see Fig. 7).
The above set of observations let us to deduce that the thicker lower
part of the Arapi sections has lacustrine origin and the upper part is
alluvial in the northern part of the Shirak Basin. The Lusaghbyur and
Haykadzor sections in the southern part of the basin are composed only
of lacustrine sediments. The alluvial deposits constituting the upper
part of the s 314 section represent the south-eastern margin of the se-
dimentary basin.
4.1.3. Geomorphological features and tectonic deformation
The area of distribution of the Quaternary units described above
corresponds to different topographical levels, which form terraces of
the Akhuryan River and its tributaries (Fig. 8). These levels decrease in
their altitude from north to south. The highest and the northernmost
one corresponds to the Karakhach unit surface (s 226, s 227 and s 306)
and shows the altitudes of 1770–1750 m. The intermediate level cor-
responds to the Arapi unit. Its altitude is about 1700 m near the Kaps
village (s 209) and drops sharply to 1665 m near the Leninakan hy-
dropower plant (HPP, s 208). The thickness of the unit changes from
5–6 m to 15–20 m respectively. Like topography the altitude of the
Akhuryan River channel decreases by 100 m within the Jradzor - HPP
segment. The greatest thickness of the unit according to the borehole
drilling achieves 137–138 m (Marmashen brh. 6). The lower part of the
unit is composed of lacustrine sediments and may probably cover
coarse Karakach alluvium at the very bottom. If this is the case, the total
vertical offset of the Karakhach unit between the villages of Jradzor and
Marmashen reaches 260 m. The lowest and the southernmost level
corresponds to the Ani unit surface. It is situated at altitudes of about
1550 m near the villages of Haykavan and Arapi, 1520–1500 m in the
area of the Gumri city (s 308, s 309 and s 341), 1510–1500 m near the
village of Lusaghbyur (s 316, s 317), and 1490 m in Haykadzor (s 318).
The longitudinal profile along the Akhuryan River channel indicates
that sediment accumulation and deformation of the Shirak Basin were
simultaneous processes.
The fluvial gradient of the Akhuryan River channel within the
Jradzor (s 227) - Marmashen Monastery (s 340) segment reaches
Fig. 6. Intrastratal deformation probably of seismic origin (seismites): (a) site 326, layer 6 (upper); (b) site 326, layer 6 (lower); (c) site 336; (d) site 341. Position of
sites is given in Fig. 1 and 2. Photos by E.A. Shalaeva and V.G. Trifonov.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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20.3 m/km. The gradient is particularly high near the Leninakan HPP as
the area rests on an intersection of the Akhuryan River channel and the
WE trending Late Cenozoic Kaps flexure that stretches along the
southern slope of the Shirak Ridge. The flexure probably corresponds to
the fault in the underlying rocks and is believed to have been devel-
oping at least since the Ani accumulation started. The gradient within a
10 km Marmashen (s 340) - Arapi (s 338) segment equals to 3.9 m/km.
It decreases southwards to 3.7 m/km within a 3 km segment and to
1.8 m/km within the next 45 km in the central part of the basin. Within
a 9 km segment to the south of the western termination of the
Bartsrashen Upland composed of the Voghchaberd unit the gradient
increases to 5.3 m/km and then again decreases to 3.9 m/km.
Fig. 8 demonstrates that the surface of the Pliocene – Early Qua-
ternary basaltic trachyandesites also decreases in the north-to-south
direction from 1735 to 1740 m within the Jradsor section (north to s
226) and ∼1690 m within the Kaps section (s 209) to 1620 m near the
Leninakan HPP and 1515 m near the Marmashen Monastery (s 340).
Further south the volcanics are not exposed and the Arapi unit con-
stitutes the Akhuryan River banks. To the east of the village of Lu-
saghbyur, the Arapi unit covers the Voghchaberd unit at the altitude of
∼1500 m. The Messinian and Pliocene basaltic trachyandesites spread
over the Akhuryan river banks within a 4 km distance to the north of
the village of Haykadzor and their surface is situated at ∼1470 m in s
318. To the south, near the medieval Ani town, the exposed thickness of
lavas reaches several tens of meters. One of the source-volcanoes for the
lavas is a Qurtblur volcano (s 421). A layer of the Upper Pliocene
rhyolitic tuffs is situated between the uppermost Pliocene and Messi-
nian – Lower Pliocene lavas. The thickness of the tuff increases to the
Fig. 7. Stratigraphic sections of the Arapi unit. See Fig. 4 for the symbols. Position of the sections is shown in Fig. 1 and 2.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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east and south-east of the medieval Ani town and one of the centers of
the tuff eruption is identified to the east of s 428.
The Arapi unit is ruptured in the Lusaghbyur (s 317) outcrop by a
thrust tilted ∼50° to the north. A clay micro-diapir intrudes along the
fault zone and exposes molluscs of the Ani unit composing the buried
part of the section.
The altitudinal profile along the southern slope of the Shirak Ridge
from the Akhuryan valley in the west to the Upper Pambak Basin in the
east demonstrates large zone of deformation (Fig. 9; BeB in Fig. 2). As
it is written above the top surface of the Karakhach unit is situated at
altitudes between 1750 and 1770 m a.s.l. (s 306, s 226 and 227) and the
top surface of the Gelasian lavas is at altitudes between 1735 and
1740 m a.s.l. (s 226). This geomorphological level maintains approxi-
mately the same elevation along the southern slope of the Shirak Ridge
and sharply increases at the Jajur Pass, where the top surface of the
well-rounded pebbles has the altitude of 1955 m. The level sharply
decreases to the east, to the Pambak riverhead (UP in Fig. 2), where the
surface of the alluvium is not higher than 1730 m and it keeps de-
creasing further along the Pambak River. The base of the pebble allu-
vium is not exposed.
Slightly eastwards, pebbles cover Cretaceous deposits and lean
against the Early Miocene alkaline basalt, which composes the pass (Jp
in Figs. 1, 2 and 220 in tables B.1, B.2, and B.3). Milanovsky (1962)
interpreted the presence of the pebbles as deposits of a paleo-valley,
which connected the northern part of the Shirak Basin and the Pambak
paleo-valley. We consider the pebbles belong to the Karakhach unit.
This alluvium proves the uplift of the Jajur Pass by ∼200 m relative to
the northern border of the Shirak Basin that happened after accumu-
lation of the Karakhach unit.
The similar uplift of the Karakhach Pass (Kp in Figs. 1 and 2) be-
tween the Lori Basin in the east and the Upper Akhuryan Basin in the
west (A–A in Fig. 2) is recognized (Trifonov et al., 2016). The zone of
deformation between the Jajur and Karakhach passes is expressed in
sharp lowering of the Bazum Ridge from the west to the east. The chain
of the Early Pleistocene volcanoes stretches along the uplifted Javakheti
Ridge. Milanovsky (1968) named this NS trending zone of deformation
and volcanism as the Trans-Caucasus transverse uplift. Mets-Sharailer
and Aragats volcanоs belong to its southern continuation. The Aragats
volcano is considered to be active since ∼1 Ma to ∼0.45 Ma
(Chernyshev et al., 2002;Meliksetian, 2012). Basaltic andesite lavas are
spread to the west, their western front is exposed 10 km to the south of
the Gyumri city. KeAr ages of tephra from the cone, basaltic andesites
from the northeastern part of the caldera and lava flow (s 439, 440, and
432 in Figs. 1 and 2 and tables B.1, B.2, and B.3) are about 0.9 Ma. The
basement of this volcanic formation is represented by an andesite with
the KeAr age of 5.2 ± 0.2 Ma.
4.2. Palaeontological results
Detailed data on mollusc, fish, and rodent fauna from the Ani and
Arapi units of the Shirak Basin will be published in a separate paper by
A. Tesakov, P. Frolov et al. In this paper, we sum up the main
Fig. 8. Longitudinal geological-geomorphological profile along the Akhurian River (the lower section continues the upper to the south).
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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conclusions related to the age and environment of accumulation of
these units.
4.2.1. Malacofauna, ichthyofauna, small mammal fauna
The freshwater gastropods and bivalve molluscs were found in the Ani
and Arapi units. The Ani unit is characterized by numerous molluscs
from different layers of the sections 326 (Voghji) and 336 (Haykavan).
Records of the Ani assemblage in the clay diapir of s 317 (Lusaghbyur)
prove the presence of the Ani deposits below the Arapi sediments in the
section of Lusaghbyur. The Arapi unit is characterized by numerous
molluscs from different layers of the section 318 (Haykadzor) and few
finds in layer 3 of s 317. The malacofauna from the Arapi unit is re-
presented only by recent lacustrine species and can hardly be older than
the Middle Pleistocene. The association of malacofauna from the Voghji
section, which has similar features with molluscs of the other sections
of the Ani unit, is represented mainly by extinct freshwater species.
Only Valvata cf. piscinalis (Müller, 1774) and some species of bivalve
molluscs of the Euglesidae family are still present. This points to an
older age of the Voghji fauna which perhaps ranges from the Calabrian
through the lowest Middle Pleistocene.
Fish remains were found in s 317 (Lusaghbyur, layers 2 and 3) and s
318 (Haykadzor, layer 4) sections. This assemblage contains lacustrine-
fluvial association of Cypriniformes with dominant remains of Capoeta
and representatives of the subfamily Leuciscinae (Leuciscus,Alburnus).
Numerous small mammal remains (mostly teeth of arvicoline ro-
dents) were found in layer 4 of s 318 (Haykadzor). This fauna is dated
to the time interval between 0.78 and 0.6 Ma based on stage of evo-
lution of the water vole Mimomys intermedius (Newton, 1889) and the
presence of primitive Microtus (Terricola) sp. The fauna cannot be
younger than 0.6 Ma, the time, when M. intermedius is replaced in
Europe and western Asia by its evolutionary successor, the water vole
Arvicola.
Melik-Adamyan (1994,2004;Agadjanyan and Melik-Adamyan,
1985) gave a similar age estimation based on small mammal fauna of
Arapi 1 and 2, Kazachii post in the Gyumri city, Gyumri airport, and
Bayandur (11 km to the south of Gyumri.) He correlated the found
rodent fauna with the Tiraspol faunal complex of the East European
biochronological system and dated the studied assemblages to the early
Middle Pleistocene. Melik-Adamyan (2004) revised the older identifi-
cations based on the large mammal fauna from the upper Arapi unit in
the Gyumri city (Avakyan, 1959;Avakyan and Alekseeva, 1966;
Alekseeva, 1977;Vangengeim, 1980) and concluded that they did not
contradict to the Arapi unit age estimates based on small mammals.
This conclusion conforms to the observations in the Arapi unit
section (s 430) southward of the village of Lusaghbyur, where loess-like
loam and fine-grained sands (3 m), and thin-bedded silts and fine-
grained sands with lenses of coarse sand, gravel and well-rounded
pebbles (4 m) below are exposed. The lower layer contains obsidian
pebbles. In talus just near the lower layer, a lower tooth of Equus sp.
was found. According to the opinion of I.V. Foronova from the Institute
of Geology and Mineralogy of the Siberian Branch of the Russian
Academy of Sciences in Novosibirsk (personal communication), the
morphology of the tooth shows that the horse belongs to the late forms
of the stenonid lineage and its age can correspond to the late Calabrian
through early Middle Pleistocene.
4.2.2. Palynological data
In total 26 samples from the Voghji (s 326) and Haykavan (s 336)
sections of the Ani unit were examined by A.N. Simakova. Pollen dia-
grams are given in Appendix A (Fig. A.1 and A.2). The spectra of Voghji
(s 326) and Haykavan (s 336) sections of the Ani unit falls into several
pollen complexes.
Four PC were identified in the Voghji section (Fig. A.1). PC-1 from
layer 9 and PC-2 from layer 8 characterize the lower clay part of the
section. The spectra contain up to 70% of herb pollen. Trees are re-
presented in PC-1 by the pollen of Pinus, Picea, Tsuga canadensis, and
single grains of Pterocarya and Betula. The pollen of Chenopodiaceae,
Poaceae, and Asteraceae dominate in the herb group. Such spectra in-
dicate the predominance of forest-steppe coenoses and relatively cool
and dry climate.
Pollen of Chenopodiaceae, Asteraceae, and Ephedra is present in
greater amount in PC-2 spectra. There is pollen of different conifers:
Taxodium, Podocarpus, Tsuga canadensis, T. sieboldii, T. aculeata, Т. di-
versifolia, Abies, Picea, Pinus, and broad-leaved trees: Acer, Castenea,
Carya, Juglandaceae, Moraceae, Carpinus, Fagaceae, Tilia, Ulmus,
Liquidambar, Myrica, and Quercus. Grasses are represented mostly by
the pollen of Chenopodiaceae, Asteraceae, and Ephedra. This indicates
the predominance of forest-steppe vegetation and relatively warm
temperate climate. Probably, vertical zonation already existed at that
time. Sciadopites, Podocarpus, Cedrus, Tsuga, Picea and Abies occupied
Fig. 9. WE trending geomorphological profile along the southern slope of the Shirak Ridge from the Akhuryan River valley up to the Upper Pambak Basin (line B–B in
Fig. 2).
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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highlands. Mixed forests with Pinus, Acer, Juglandaceae, Castanea,
Liquidambar,Quercus, Carpinus, and Ulmus dominated lower altitudinal
belts. Lowlands were covered by meadow-steppe vegetation.
PC-3 and PC-4 belong to layer 3. The pollen of Pinus is more nu-
merous and the pollen of Carya, Pterocarya, and Liquidambar are absent
in PC-3. The trees are represented by the pollen of Castanea, Betula,
Ulmus, and Quercus. The quantity of the pollen of Chenopodiaceae and
Ephedra decreases. It was a time of widening of areas of conifer (Pinus
and Picea-Tsuga) forests and more humid and cool climate than at PC-2
time. PC-4 spectrum is characterized by the increase of content of the
herb pollen of Chenopodiaceae and Asteraceae that proves the ar-
idization of climate.
Two PC were distinguished by analyzing samples from the layer 11
of the Haykavan (s 336) section (Fig. A2). PC-1A characterizes the
lower olive-green clays and the lower part of middle bluish-grey clays.
PC-2A characterizes the upper part of the middle clays and the upper
light-brown clays. The upper part of the Haykavan section contains only
single grains of herb plants.
The spectra of PC-1A contain 20–50% of the pollen of trees: Tsuga
canadensis, T. sieboldii, Т. diversifolia, T. minima, Pinus, Picea, and single
grains of Abies, Cedrus, Carya, Liquidambar, Carpinus, Tilia, and Betula.
The pollen of Chenopodiaceae, Poaceae, and Asteraceae dominate in
the herb group. Spores represent Sphagnum, Polypodiaceae and Riccia.
The spectra evidence the predominance of forest-steppe coenoses under
temperate climate. The PC-1A is similar with the PC-1 of the Voghji
section.
The amount of herb and small-shrub pollen of Chenopodiaceae,
Asteraceae and Ephedra increases in PC-2A. The amount of Picea and
Pinus as well as species of Tsuga decreases. Cedrus, Abies, Podocarpus
and Carya disappeared. The trees are represented by grains of Ilex,Acer,
Moraceae, Fagaceae, Lonicera, Salix, and Quercus. The spores of fresh-
water algae Cosmarium and Sphagnum indicate the presence of marshy
areas, which could be formed because of the shallowing of the Shirak
lake as a result of aridization or tectonics. The steppe vegetation ex-
panded. The PC-2A spectra are similar to the spectra of PC-2 and PC-4
of the Voghji section and the spectra of Ani unit in the Marmashen
borehole at the depths of 30–50 m (Zaikina et al., 1969a,b).
4.2.3. Diatoms
The samples for studies of diatoms were collected from layers 6 and
7 of the Haykadzor section of the Arapi unit (samples 318/1–4) and
from diatomaceous clay interbeds of the lower part of the Haykavan
section of the Ani unit (samples 336/5 and 336/6). The diatoms were
identified by G.V. Kovaleva.
Epithemia sp., Cocconeis sp., Navicula sp., Rhopalodia sp., and
Cymbella sp. are present in all samples from the Haykadzor (s 318)
section. Cymatopleura solea,C. elliptica, and Gomphonema sp. were found
in samples from the lower and middle parts of the section, where
Cyclostephanos sp. and rarely Cocconeis placentula,Melosira sp.,
Pinnularia sp., and Hantzschia sp. are present. Nitzscha sp., Opephora sp.,
Diploneis sp., Amphora sp., and Cyclotella sp. were found in the samples
from the middle and upper parts. The brackish water forms Thalassiosira
sp. as well as Gyrosigma sp. and Campylodiscus sp. were determined in
the upper sample as well. The diatoms from the upper parts are less well
preserved. Taking into account that the majority of diatoms are fresh
water, and that brackish water forms were found together with fresh
water forms and only in the upper samples, we can deduce that in
general the forms characterize freshwater conditions. Diatoms occurred
in near coastal shallow areas overgrown with macrophytes. Both
benthic and epiphytic forms are present. They indicate conditions of
temporary lake with a variable position of a coastline.
The lower sample 336/5 from the Haykavan (s 336) section contains
large diatoms in abundance. Epithemia sp., Cyclotella sp. aff., Amphora
sp., Cocconeis sp., Surirella sp. are found. Cyclotella scrobiculus Alesch. et
Pirum, which were described earlier in the Pleistocene deposits of
Armenia, are rare in occurrence. Cyclostephanos aff. dubius dominates
and Diploneis sp. and Amphora sp. are less frequent in the upper sample
336/2. The finds indicate a nearshore part of the basin, which was
deeper and less overgrown with macrophytes than the Haykadzor lake.
4.3. Archaeological results
Early Palaeolithic artifacts were found in the lower and middle parts
of the Jradzor section in L 1 and 3 (Fig. 4, s 226; Fig. 1, s 277). E.V.
Belyaeva collected seven pieces, among which are a scraper, chopper,
large flake, three picks, and a primitive handaxe (Fig. 10) made mostly
of the Eocene dacites. Tool types and their technological and morpho-
logical features are analogous to those in the Early Acheulian industry
found earlier by Lyubin and Belyaeva (2011) in the Lori Basin, in the
lower part of the Karakhach quarry section (41°04.427′N,
44°07.2375′E; H = 1800 m), after which the Karakhach unit was
named. Several similar lithics were collected by D.V. Ozherelyev in the
Fig. 10. Lithics from the Karakhach unit (s 226 and s 227) in the Shirak Basin,
NW Armenia: (1) pick, (2) primitive handaxe, and (3) chopper. Photos and
pictures by E.V. Belyaeva.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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Agvorik [Yeni-yol] section of the unit (s 103; 41°04.540′N, 43°46.312′E;
H = 2033 m) in the Upper Akhurian Basin (Trifonov et al., 2016).
5. Discussion
5.1. Dating of sedimentary units
The successive overlapping of the three units within the Shirak
Basin proves that the Karakhach unit is older than the Ani unit, and the
Ani unit is older than the Arapi unit. All three units cover the Gelasian
basaltic trachyandesites in the northern part of the Shirak Basin with
the age of 2.3–2.0 Ma (2014–208 and 2015–340 in table B.1) and un-
derlie the Leninakan trachytic tuff with an average KeAr age of
∼0.68 ± 0.05 Ma (2014–254/2, 2014–254/3, and 2015–317/u in
table B.1). Our age estimates of the tuff are similar to
39
Ar-
40
Ar date of
0.65 ± 0.04 Ma obtained by C. Connor et al. during the studies for
volcanic hazard assessment of the Armenian Nuclear Power Plant
(Meliksetian, 2012).
Stone implements found in the lower and middle parts of the
Jradzor sections of the Karakhach unit (s 226 and s 227) are dated to
the Early Palaeolithic on the basis of their micromorphology. Similar
implements were found in the Karakhach quarry (the type section of the
Karakhach unit). The sediments of the quarry were dated by SIMS
238
Ue
206
Pb and KeAr techniques and have the age of 1.9–1.75 Ma
(Presnyakov et al., 2012;Trifonov et al., 2016). They are characterized
by N polarity in the lower part and R polarity in the upper part. Like
Karakhach sections, the Jradzor (s 226) and Meghrashat (s 306) sec-
tions have N polarity at the bottom and R polarity in the most part of
the overlying sequence. The Karakhach unit is older than the Ani and
Arapi units, thus, N polarity at its bottom can belong neither to Cobb
Mt. nor to Jaramillo. At the same time, it cannot belong to Gauss Chron
or Reunion subchron as the presence of archaeological artifacts in the
sediments of such an age is problematic. Thus, it is very likely that the
Karakhach unit of the Shirak Basin corresponds to the Olduvai subchron
and the lower Calabrian. Its base is dated to 1.9–1.77 Ma and its top is
younger than 1.77 Ma.
The malaсofauna of the Voghji section (s 326) of the Ani unit is
represented mainly by extinct forms and can be dated to the late
Calabrian and the earliest Middle Pleistocene.
The presence of many exotic forms (Tsuga, Podocarpus, Cedrus, Abies
alba, Taxus, Liquidambar, Altingia, Castenea, and Carya) indicates a re-
latively old age of the lacustrine deposits of the Voghji and Haykavan
sections. The obtained spectra are similar to spectra from the
Apsheronian (Calabrian) deposits in the Caspian region (Filippova,
1997) and Gurian – Early Chauda (upper Calabrian – lowermost Middle
Pleistocene) layers in Georgia (Shatilova, 1974;Shatilova et al., 2011).
Thus, the spectra of the Voghji and Haykavan sections fit to the geo-
logical age assessed for these deposits. The forest-steppe and steppe
landscapes dominated at that time in the Shirak Basin. The climate
experienced some fluctuations at that time. Palynological data on the
Voghji section demonstrate changes from cool and dry (PC-1) to warm
and dry (PC-2), cool and humid (PC-3), and cool and dry (PC-4) cli-
mate. PC-2 vegetation may correspond to the warm epoch of the late
Apsheronian – Gurian, i.e., to the final Calabrian.
Thick clayish part of the Voghji and Haykavan sections is char-
acterized by R magnetic polarity with two intervals of N polarity. These
intervals may probably correspond to the Jaramillo and Cobb Mountain
(1.24–1.22 Ma) subchrons. The base of the unit is probably older. The
upper part of the Voghji section has N polarity and belongs to the
Brunhes Chron, i.e., the Middle Pleistocene. Thus, the Ani unit is dated
to the time interval of ∼1.3–0.75 Ma.
All the examined sections of the Arapi unit have N magnetic po-
larity, i.e., belong to the Brunhes Chron. The analysis of small mammal
fauna shows that the unit is dated to the earliest Middle Pleistocene and
is not younger than 0.6 Ma. The data on the malaсofauna confirm this
conclusion. The leninakan tuff covers most of the Arapi sections. Only
in the section near the Gyunri Airport, Melik-Adamyan (1994) reported
similar rodent fauna below and above the tuff. Thus, the Arapi unit is
dated to the range of 0.78–0.6 Ma.
5.2. History of the Shirak Basin formation
The Shirak Basin was formed on the heterogeneous basement,
which is mainly composed of the deformed volcanic-sedimentary
Eocene and probably Mesozoic rocks with a few Paleozoic blocks. The
latest Early Cenozoic volcaniс events occurred along the southern and
north-eastern borders of the basin at the end of the Oligocene
(24–25 Ma) and Early Miocene (22–23 Ma). It is not evident whether
the basin already existed as a depression during accumulation of the
Voghchaberd unit. According to a borehole drilled 8 km to the south-
west of Gyumri (Sayadyan, 2009), the thickness of the Voghchaberd
unit within the basin reaches 840–920 m. A thick section of the unit is
exposed also within the southern border of the basin (s 310). Taking
into account the results of KeAr dating the interpretation of the
Voghchaberd unit age may be twofold. On the one hand, the age of the
unit may correspond to the age of the included volcanic blocks, i.e.,
24–25 Ma. On the other hand, the age of the tuffaceous matrix of
1.6 ± 07 Ma may approximately correspond to the age of the Vogh-
chaberd breccia. However, the latter figure should be used with cau-
tion. Such a young age may be the result of its hydrothermal reworking.
Anyway, the breccia was formed before the accumulation of the Ani
unit due to explosions that manifested the beginning of volcanic ac-
tivity in the Arteni-Aragats area.
The Messinian and Early Pliocene (5.8 ± 0.2 Ma to
4.26 ± 0.12 Ma) eruptions of basic lavas in the Ani area dammed the
Akhurian River. This damming and subsidence of the Shirak Basin led
to the formation of a lake, which was filled with the Upper Pliocene and
lower Gelasian fine-grained lacustrine deposits (Sayadyan, 2009). In
the Late Pliocene the subaerial rhyolitic tuff explosions occurred in the
Ani area. If the northern part of the Shirak Basin remained as a de-
pression later, it could be filled with the Gelasian basaltic trachiande-
sites (2.3–2.0 Ma).
At the “Karakhach” time (about 1.9–1.7 Ma), the alluvial sedi-
mentation took place within the northern border of the Shirak Basin (s
226, s 227, s 306, and probably Marmashen borehole 6). Fine-grained
deposits of the lower part of the unit were accumulated by stagnant
waters, partly (s 306) in lacustrine conditions. The analogous sediments
are absent near the Marmashen Monastery (s 339 and s 340) and in the
more southern sections of the basin (s 314 and s 318), where the age of
the Quaternary deposits covering the Miocene or Pliocene formations is
younger. The “Karakhach” time drainage system of the northern part of
the Shirak Basin accumulated local terrigenous material and trans-
ported it to the Pambak River paleo-valley. This system was isolated
from the Akhuryan riverhead because of the uplift of the western ter-
mination of the Bazum Ridge, which took place about 2 Ma ago (Ritz
et al., 2016). The Akhuryan riverhead of the “Karakhach” time found its
way via the Karakhach Pass to the Dzoraghet-Debed valley (Trifonov
et al., 2016).
In the Calabrian, the Shirak Basin subsided along the Kaps flexure-
fault zone and the paleo-valley of the “Karakhach” time remained in its
relatively uplifted side. At the same time, the uplift of the Trans-
Caucasus transverse zone isolated the Shirak part of the paleo-valley
from the Pambak River basin. The lacustrine sedimentation represented
by the Ani and Arapi units began in the Shirak Basin not later than
1.25 Ma ago. Each of these units corresponds to a separate cycle of
sedimentation, which started with lacustrine accumulation and ended
with alluvium accumulation. Lacustrine deposits sometimes have in-
terbeds of permanent and temporary stream sediments like, for ex-
ample, at the Haykavan section (s 336).
The alluvium of the upper Ani unit (the end of the “Ani” cycle)
indicates the probable intensification of water erosion that resulted in
the level drop of the “Ani” lake in the Akhuryan valley in the south of
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
53
the basin during the earliest Middle Pleistocene. This could be due to
the relative uplift of the northern part of the Shirak Basin. The younger
sediments of the “Arapi” lake basin (the early Middle Pleistocene) were
incised into the Ani deposits by 50–100 m. Within the southern part of
the Shirak Basin, the Arapi lacustrine deposits covered the Ani unit (s
317) and spread further to the south and to the east (s 314 and s 318),
i.e., outside the area of the Ani sedimentation. Thus, the successive
migration of the area of sedimentation to the southern part of the
Shirak Basin occurred due to the uplift of its northern part.
Lacustrine sedimentation gave place to accumulation of alluvium in
the central part of the Shirak Basin at the end of the “Arapi” cycle
(0.7–0.6 Ma). The intensification of water erosion and/or volcanic ac-
tivity of the Araghats volcano (eruption of the Leninakan tuff) resulted
in the level drop of the residual “Arapi” lake in the south of the basin.
After 0.6 Ma, the basin was drawn into the tectonic uplift of the Lesser
Caucasus. Nowadays the Akhuryan River incises intensively and con-
trols water transit from the Upper Akhuryan and Shirak Basins to the
south.
Seismites within the Ani and Arapi units may serve as an evidence
for strong palaeoearthquakes (Fig. 6). A micro-graben in the Arapi unit
in s 316 (Lusaghbyur) and the landslide in s 327 (Voghji), which is
deformed by ruptures without any regularity in their orientation, could
be caused by palaeoseismic events as well.
5.3. Origin of the Shirak Basin
The configuration and observed Quaternary structure of the Shirak
Basin do not demonstrate significant influence of the major Late
Cenozoic faults caused by collision in the Arabia-Caucasus segment of
the Alpine-Himalayan Belt (Trifonov et al., 1994,2017). At the same
time, subsidence of the basin was accompanied by volcanism in the
surrounding area during the whole period of the basin development.
Those were eruptions in the Late Oligocene along the southern side of
the basin that resulted in formation of the Voghchaberd unit, in the
Early Miocene in the north-eastern border (Jajur Pass), and in the Late
Miocene in the eastern surroundings of the basin (Tsaghkunyats and
Teghekunyats Ridges). In the Messinian and Early Pliocene, they gave
place to eruptions of the basaltic andesites within the southern sur-
rounding of the Shirak Basin (the Ani area) that were continued by
explosions of the rhyolithic tuffs in the Late Pliocene. Andesites erupted
in the Messinian – Early Pliocene in the eastern boundary of the basin,
which is a part of the Trans-Caucasus transverse zone (s 432). Ac-
cording to the V.A. Lebedev's data, eruptions lasted during the whole
Pliocene on the Kars-Digor Highland.
Basic lavas were erupted in the southern part of the Javakheti
Highland and Upper Akhuryan Basin in the Gelasian (Trifonov et al.,
2016). As a result, lavas filled the Akhurian paleo-valley and spread to
the northern part of the Shirak Basin (Lebedev et al., 2008,2015). In
the Calabrian and Middle Pleistocene, the volcanic activity renewed in
the southern surrounding of the Shirak Basin, that is, the basalts near
the Digor town in Turkey have the age of ∼1.6–1.3 Ma (Innocenti et al.,
1982). The Arteni and Arailer volcanoes as well as the Aragats volcanic
center began to act successively. The Arailer volcano lavas are dated to
1.37 ± 0.04 Ma to 1.28 ± 0.04 Ma and the Arteni volcano acid pro-
ducts are dated to 1.26 ± 0.05 Ma (Lebedev et al., 2011). According to
KeAr dating the Aragats volcano was active within the period of
0.97 ± 0.09 Ma to 0.45 ± 0.07 Ma (Chernyshev et al., 2002). Its lavas
filled the south-eastern part of the Shirak basin (s 434). The Mets-
Sharailer volcano was active nearly 0.9 ± 0.1Ma (s 439 and s 440)
and its andesite lavas cover the eastern part of Shirak Basin (s 432). On
the basis of KeAr dating and chemical composition the Leninakan tuff
is attributed to the late stage of the III phase of the Araghats volcano
activity, the age of which was determined by Chernyshev et al. (2002)
as 0.72 ± 0.07 Ma and 0.68 ± 0.07 Ma. The Araghats trachyte-dacite
cone was formed in that phase and was partly destroyed after an ex-
plosive event that produced the Leninakan tuff.
Thermodynamic calculations and their correlations with the results
of geochemical and petrological studies showed that the Late Cenozoic
magmas were generated in the northern part of the Armenian Highland
(including the region under study) under P = 0.95–1.05 GPa and
T = 850–1100 °C, characteristic for the depths of 35–40 km, i.e., the
lowest Earth's crust (Koronovsky and Demina, 1999,2007). According
to the quoted authors' opinion, the magmatic sources near the crust-
mantle boundary was formed by the heat-mass transfer from the deeper
horizons of the mantle. Synchronism of the Shirak basin subsidence and
volcanism in its surrounding area supports the idea of the interrelation
of the subsidence and the sub-lithosphere movements and transforma-
tions of matter manifested in volcanism. Sokolov and Trifonov (2012)
analyzed possible mechanisms of such links. This conclusion is sup-
ported by the successive migration of the area of subsidence and sedi-
ment accumulation in the Shirak Basin to the south simultaneously with
the increasing volcanic activity within the southern border of the basin.
Similar interrelations could influence the formation of the Van Lake
depression as well as the Ararat and Major Sevan Basins, although the
origin of the two latter basins is also controlled by major fault zone,
forming the Late Cenozoic structural pattern of the Armenian Highland.
6. Conclusions
1. Numerical ages for of the Quaternary units were determined:
1.9– < 1.7 Ma – the Karakhach unit, 1.3–0.75 Ma – the Ani unit,
0.75–0.6 Ma the Arapi unit.
2. During the “Karakhach” time the river flow from the northern part
of the Shirak Basin was directed mainly towards the Pambak River
paleo-valley, i.e. it was roughly EW trending. Later the flow ac-
quired NS direction. It happened for two reasons: the uplift of a
segment of the Trans-Caucasus transverse flexure-fault zone along
the eastern side of the basin and the development of the Kaps
flexure-fault zone along the northern side of the basin.
3. During the “Ani” and “Arapi” time the Shirak Basin became the area
of predominantly lacustrine sedimentation. It is quite possible that
the lake, which corresponds to the “Ani” clays (“Leninakan” lake”)
appeared due to lava damming on the southern rim of the basin.
Lacustrine sedimentation migrated from the north to the south of
the basin due to the tectonic uplift of its northern part.
4. It is not likely that the flexure-fault zones along the Shirak Basin
boundaries have any relation to the major faults caused by the
collisional shortening. Besides, during the whole epoch of the basin
subsidence, the latter was accompanied by volcanism in the sur-
rounding areas. These two facts allow to suppose the dependence of
the basin subsidence on movements and transformations of mantle
matter.
Funding sources
The authors carried out field studies of the region in the years
2015–2016 with financial support of the Russian Foundation for Basic
Research (RFBR) and the State Committee of Science (SCS) of Republic
of Armenia in the frames of the joint research projects RFBR 15-55-
05009 and SCS 15RF-031, accordingly. Laboratory palaeomagnetic
studies were performed with financial support of the Ministry of
Education and Science RF (project No. 14.Z50.31.0017). Processing,
analyzing, and interpretation of the data were carried out in the year
2017 and financed by the Russian Science Foundation, Project No. 17-
17-01073.
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
54
Appendices
Appendix A
Fig. A.1. Pollen diagram from the Voghji section (s 326).
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
55
Fig. A.2. Pollen diagram from the Haykavan section (s 336).2
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
56
Appendix B
Table B.1
Ages of the volcanic rocks determined by K-Ar method, NW Armenia (performed by V.A. Lebedev).
No Year-sample
No
Location Coordinates Rock Material K, % ± σ
40
Ar
rad
(ng/g) ± σ
40
Ar
atm
,%
(in sample)
Age, Ma ± 2σ
Lower Miocene volcanic rocks
1 2014-220 Jajur Pass, s 220, H = 1958 m 40°51.884´N
44°00.016´E
Alkaline basalt Ground-mass 1.50 ± 0.02 2.336 ± 0.013 22.9 22.5 ±0.6
Voghchaberd unit
2 2016-431/1 Southern Shirak Basin. Magaridzor canyon,
s 431 = s 310, H = 1583 m
40°37.261´N
43°46.658´E
Andesitic breccia, matrix
hydrothermally reworked
Ground-mass 1.69 ± 0.02 0.19 ± 0.05 96.0 1.6 ±0.7*
3 2016-431/2 Southern Shirak Basin. Magaridzor canyon,
s 431 = s 310, H = 1583 m
40°37.261´N
43°46.658´E
Andesite of big lava block
within breccia
2.41 ± 0.03 4.117 ± 0.015 20.7 24.5 ±0.6
4 2016-431/3 Southern Shirak Basin. Magaridzor canyon,
s 431 = s 310, H = 1583 m
40°37.261´N
43°46.658´E
Andesitic fragment within
breccia
2.39 ± 0.03 4.066 ± 0.016 20.1 24.4 ±0.6
5 2016-431/4 Southern Shirak Basin. Magaridzor canyon,
s 431 = s 310, H=1583 m
40°37.261´N
43°46.658´E
Andesitic fragment within
breccia
2.09 ± 0.03 3.625 ± 0.019 59.7 24.8 ± 0.7
Ani, lower lavas, Messinian to Lower Pliocene
6 2016-429/1 Southern surrounding of Shirak Basin, Ani,
s 429, H = 1428 m
40°30.202´N
43°34.910´E
Lower basaltic andesite Ground-mass 1.42 ± 0.02 0.57 ± 0.006 79.4 5.8 ±0.2
7 2016-420/1 Southern Shirak Basin, v. Haykadzor, s 420,
H = 1549 m
40°30.707´N
43°39.317´E
Andesite. Southern foot of
Qurtblur cone
1.72 ± 0.02 0.671 ± 0.004 59.4 5.60 ±0.15
8 2016-421 Southern Shirak Basin, v. Haykadzor, s 421,
H = 1613 m
40°30.698´N
43°39.543´E
Andesite. Southern slope of
Qurtblur cone
1.68 ± 0.02 0.649 ± 0.009 84.5 5.6 ±0.2
9 2016-417 Southern Shirak Basin, v. Haykadzor, s 417,
H = 1449 m
40°31.841´N
43°39.305´E
Upper basaltic andesite,
N
21
1.69 ± 0.02 0.500 ± 0.003 69.8 4.26 ±0.12
Basaltic andesite lavas between the Sharailer and Aragats volcanoes
10 2016-436 Eastern Shirak Basin, v. Geghadyr, s 436, H
= 2067 m
40°39.227´N
44°06.967´E
Basaltic andesite southern
foot of Sharailer
Ground-mass 1.60 ± 0.02 0.578 ± 0.006 78.8 5.2 ±0.2
Ani, Anipemza, and Ani station, rhyolitic tuffs and ignimbrites, Upper Pliocene
11 2016-429/2 Southern surrounding of Shirak Basin, Ani,
s 429, H = 1428
40°30.202´N
43°34.910´E
Rhyolitic ignimbrite Matrix of tuff 3.52 ± 0.04 0.81 ± 0.06 96.0 3.3 ±0.5
12 2015-322/2 Southern surrounding of Shirak Basin, Ani
station, quarry, s 322, H = 1497 m
40°29.385´N
43°37.609´E
Rhyolitic pumice Glass 3.36 ± 0.04 0.732 ± 0.008 79.3 3.14 ±0.10
13 2016-418 Ani station, quarry, s 418 = s 322, H =
1497 m
40°29.385´N
43°37.609´E
Upper rhyolitic ignimbrite Matrix of tuff 3.39 ± 0.04 0.71 ± 0.06 96.5 3.0 ±0.5
14 2015-320 Southern surrounding of Shirak Basin,
Anipemza quarry, s 320, H = 1438 m
40°26.856´N
43°35.892´E
Rhyolitic tuff Glass 3.65 ± 0.04 0.76 ± 0.03 94.4 3.0 ±0.3
15 2016-419 Southern surrounding of Shirak Basin,
Anipemza, s 419, H = 1449 m
40°26.968´N
43°36.447´E
Upper rhyolitic ignimbrite 3.48 ± 0.04 0.715 ± 0.022 92.4 3.0 ±0.2
16 2016-428 Southern surrounding of Shirak Basin, Ani,
s 428, H = 1499 m
40°29.962´N
43°34.582´E
Rhyolitic ignimbrite 3.90 ± 0.04 0.759 ± 0.011 85.1 2.80 ±0.15
Unit II of the southern Javakheti Highland, northern Shirak basin, Gelasian
17 2015-340 Shirak Basin, Marmashen Monastery, s 340,
H = 1514 m
40°50.443´N
43°45.500´E
Basaltic trachyandesite Ground-mass 1.06 ± 0.02 0.1662 ± 0.0014 72.6 2.25 ±0.10
(continued on next page)
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
57
Table B.1 (continued)
No Year-sample
No
Location Coordinates Rock Material K, % ± σ
40
Ar
rad
(ng/g) ± σ
40
Ar
atm
,%
(in sample)
Age, Ma ± 2σ
18 2014-208 NW Shirak Basin, s 208, H = 1620 m 40°51.610´N
43°44.954´E
Basaltic trachyandesite 1.15 ± 0.02 0.171 ± 0.010 65.5 2.1 ±0.2
Lavas of Sharailer volcano, uppermost Calabrian
19 2016-439 Eastern Shirak Basin, Mets-Sharailer cone, s
439, H = 2304 m
40°41.371´N
44°06.836´E
Basaltic trachyandesite,
tephra
Matrix of tephra 2.28 ± 0.03 0.181 ± 0.010 95.6 1.1 ±0.2
20 2016-432 Shirak Basin, SSE of Gyumri, s 432, H =
1505 m
40°43.403´N
43°50.114´E
Basaltic andesite Ground-mass 2.06 ± 0.03 0.131 ± 0.003 65.3 0.92 ±0.04
21 2016-440 Eastern Shirak Basin, wall of Mets-Sharailer
caldera, s 440, H = 2294 m
40°41.601´N
44°07.194´E
Basaltic andesite 1.52 ± 0.02 0.093 ± 0.006 86.1 0.89 ±0.11
Lavas of the northern slope of Aragats, uppermost Calabrian
22 2016-434 Shirak Basin, northern slope of Araghats,
Orom village, s 434, H = 1608 m
40°39.572´N
43°54.092´E
Trachyandesite Ground-mass 3.24 ± 0.04 0.206 ± 0.02 39.3 0.92 ±0.03
Leninakan tuffs and ignimbrites
23 2015-227 Shirak Ridge, s 227,H = 1760 m 40°54.494´N
43°46.310´E
Trachitic ignimbrite Glass 3.88 ± 0.04 0.226 ± 0.008 93.0 0.84 ±0.07
24 2015-317/l Southern Shirak Basin, s 217, H = 1513 m,
below thrust
40°38.637´N
43°44.507´E
Trachitic ignimbrite 3.96 ± 0.04 0.225 ± 0.005 90.3 0.82 ±0.05
25 2016-435 Shirak Basin, Artik, s 435, H = 1864 m 40°37.277´N
43°59.079´E
Trachitic ignimbrite Matrix of tuff 3.75 ± 0.04 0.191 ± 0.002 95.4 0.74 ±0.05
26 2015-317/u Southern Shirak Basin, s 317, H = 1513 m,
above thrust
40°38.637´N
43°44.507´E
Trachitic ignimbrite Glass 3.96 ± 0.04 0.193 ± 0.003 87.1 0.70 ±0.03
27 2014-254/2 Pambak River, Saraghart s 254, H = 1649
m, lower part of the layer
40°51.702´N
44°13.188´E
Upper trachitic ignimbrite 3.98 ± 0.04 0.187 ± 0.016 85.1 0.68 ±0.10
28 2014-254/3 Pambak River, Saraghart s 254, H = 1649
m, upper part of the layer
40°51.702´N
44°13.188´E
Upper trachitic ignimbrite 3.79 ± 0.04 0.171 ± 0.008 82.9 0.65 ±0.06
Lavas of the Aragats volcano, correlated to the Leninakan tuff
29 Ch-2002-
7A**
Summit of Aragats Trachyte Ground-mass 3.47 ± 0.04 0.164 ± 0.012 71.5 0.68 ±0.07
30 Ch-2002-11A Summit of Aragats Trachyte 2.64 ± 0.03 0.131 ± 0.011 50.4 0.72 ±0.07
* Because of high portion of atmospheric Ar the figure seems to be doubtful
** Ch-2002 – (Chernyshev et al., 2002)
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
58
Table B.2
Chemical composition of volcanic rocks dated by the K-Ar method, NW Armenia. Major oxides.
No. Year-sample SiO
2
TiO
2
Al
2
O
3
Fe
2
O
3
MnO MgO CaO K
2
O Na
2
O P
2
O
5
LOI Sum
Lower Miocene volcanic rocks
1 2014-220 44.10 1.87 18.14 9.80 0.14 5.61 11.49 1.75 3.44 0.68 2.34 99.37
Voghchaberd unit
2 2016-431/1 57.64 1.10 16.88 6.11 0.04 1.73 5.56 2.22 2.45 0.32 5.94 100.01
3 2016-431/2 53.41 0.88 15.87 10.24 0.09 2.18 8.42 2.52 3.56 0.38 2.45 100.00
4 2016-431/3 57.32 0.93 16.70 7.74 0.09 2.23 6.53 2.65 3.27 0.28 2.26 100.00
5 2016-431/4 55.28 1.08 16.67 8.43 0.05 2.11 7.53 2.40 4.00 0.54 1.91 99.99
Ani, lower basaltic andesite – andesite lavas, Messinian to Lower Pliocene
6 2016-429/1 54.56 1.00 16.69 10.46 0.15 3.11 8.01 1.73 3.95 0.24 0.10 100.00
7 2016-420/1 56.42 0.76 15.73 8.65 0.12 2.82 8.10 2.03 3.74 0.20 1.45 100.01
8 2016-421 58.79 0.78 16.44 7.20 0.11 2.89 6.91 2.08 4.03 0.21 0.56 100.00
9 2016-417 57.73 0.76 15.80 10.23 0.11 2.50 6.61 1.99 3.91 0.26 0.10 100.00
Basaltic andesite lavas between the Sharailer and Aragats volcanoes
10 2016-436 53.61 1.05 16.92 9.00 0.14 4.36 8.25 1.94 4.12 0.49 0.12 99.99
Ani, Anipemza, and Ani station, rhyolitic tuffs and ignimbrites, Upper Pliocene
11 2016-429/2 69.84 0.36 13.76 2.35 0.07 0.51 1.49 4.48 3.35 0.06 3.74 100.00
12 2015-320 69.49 0.39 14.71 2.42 0.06 0.74 1.49 3.70 3.83 0.07 3.05 99.96
13 2016-419 69.32 0.37 13.93 2.41 0.07 0.70 1.60 4.20 3.59 0.05 3.76 100.00
14 2015-322/2 68.56 0.34 14.77 2.25 0.06 0.51 1.42 3.51 3.76 0.05 4.68 99.90
15 2016-418 67.80 0.51 14.36 3.20 0.08 0.77 2.18 4.00 4.00 0.09 3.02 100.01
Unit II of the southern Javakheti Highland, basaltic trachyandesites, northern Shirak Basin, Gelasian
16 2015-340 52.67 1.76 17.79 9.11 0.13 2.74 8.35 1.48 4.57 0.40 0.55 99.57
17 2014-208 50.68 1.53 19.88 8.35 0.14 2.31 8.90 1.49 5.75 0.50 0.18 99.70
Basaltic andesite lavas of Sharailer volcano, uppermost Calabrian
18 2016-432 53.75 1.38 16.90 9.35 0.15 3.27 7.45 2.39 4.75 0.52 0.10 100.00
19 2016-440 53.22 0.98 16.35 10.47 0.14 5.07 7.79 1.72 3.86 0.31 0.10 100.00
20 2016-439 51.03 1.16 14.38 8.15 0.13 4.89 7.79 2.41 1.97 0.47 7.63 100.01
Trachyandesite lavas of the northern slope of Aragats, uppermost Calabrian
21 2016-434 59.98 0.99 14.68 5.27 0.09 1.24 3.47 3.19 4.78 0.29 6.01 99.99
Leninakan trachytic tuffs and ignimbrites, Shirak Basin and the Pambak River upper reaches
22 2014-254/2 63.71 0.96 16.01 3.11 0.077 0.54 2.74 4.01 5.40 0.22 2.52 99.28
23 2014-254/3 64.90 0.93 15.91 2.88 0.073 0.51 2.22 3.91 5.53 0.20 2.44 99.50
24 2015-227 64.08 0.86 16.59 3.38 0.08 1.46 2.16 3.93 3.93 0.16 3.30 99.92
25 2015-317/u 64.91 0.83 15.81 3.38 0.08 1.18 2.27 4.05 4.53 0.17 2.62 99.98
26 2015-317/l 64.26 0.87 16.05 3.76 0.08 1.07 2.55 4.22 4.47 0.18 2.39 99.91
27 2016-435 66.89 0.86 15.23 3.71 0.08 0.78 2.13 4.68 5.07 0.18 0.4 100.01
28 2016-422? 63.82 1.02 15.15 4.61 0.09 1.18 2.67 4.31 4.45 0.21 2.48 100.00
Trachytic lavas of the Aragats volcano, correlated to the Leninakan tuff
29 2002-7А 65.15 0.84 15.84 4.87 0.09 1.04 2.98 3.83 5.06 0.21 0.10 100.01
30 2002-11А 64.00 0.79 15.81 5.44 0.10 1.55 4.53 3.08 4.39 0.21 0.10 100.00
Samples 2002-7A and 2002-11A are represented by I.V. Chernyshev and V.A. Lebedev
Table B.3
Chemical composition of volcanic rocks dated by the K-Ar method, NW Armenia. Microelements and some rare earth elements (ppm).
Sc V Cr Co Ni Cu Zn Ga As Rb Sr Y Zr Nb Mo Ba Pb Th U
Lower Miocene volcanic rocks
1 28 170 190 41 12 67 97 17 18 43 2300 21 180 33 ˂1 720 9.2 4 ˂2
Voghchaberd unit, Miocene
2 21 167 74 25 64 56 57 19 3.5 51 905 18 163 14 ˂2.0 670 7.0 11 ˂2.0
3 25 207 112 27 145 66 71 16 5.0 52 992 20 135 12 ˂2.0 869 7.7 12 ˂2.0
4 ˂5.0 169 77 18 41 56 63 16 3.7 61 894 15 142 12 ˂2.0 79 8.7 9.2 3.3
5 21 260 192 24 83 57 60 18 6.8 48 1288 15 151 13 3.5 907 10 12 3.2
Ani, lower basaltic andesite – andesite lavas, Messinian to Lower Pliocene
6 18 139 210 27 91 66 112 16 2.1 31 484 21 150 12 ˂2.0 488 9.0 7.4 ˂2.0
7 22 126 114 22 51 41 89 15 ˂2.0 41 460 19 165 13 2.6 542 10 8.0 3.5
8 20 107 92 21 44 35 79 17 ˂2.0 40 451 21 187 15 3.2 528 12 10 ˂2.0
9 17 126 134 18 55 47 74 16 ˂2.0 41 482 20 161 13 2.9 588 10 9.2 2.4
(continued on next page)
E.A. Shalaeva et al. Quaternary International 509 (2019) 41–61
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Table B.3 (continued)
Sc V Cr Co Ni Cu Zn Ga As Rb Sr Y Zr Nb Mo Ba Pb Th U
Basaltic andesite lavas between the Mets-Sharailer and Aragats volcanoes
10 22 168 197 30 129 57 99 15 ˂2.0 28 924 18 151 14 ˂2.0 674 9.2 5.3 ˂2.0
Ani, Anipemza, and Ani station, rhyolitic tuffs and ignimbrites, Upper Pliocene
11 ˂5.0 20 19 ˂5.0 11 13 41 15 6.5 110 162 21 265 25 3.4 782 17 24 5.7
12 ˂5.0 18 8.5 5.8 13 12 45 13 7.1 107 187 19 257 21 4.9 726 20 15 4.2
13 ˂5.0 19 24 ˂5.0 16 18 40 14 6.4 110 167 20 269 25 5.7 791 17 22 6.1
14 ˂5.0 11 7.5 ˂5.0 10 14 41 13 7.6 106 200 18 250 19 6.4 729 19 18 3.5
15 5.6 31 13 ˂5.0 11 16 52 16 2.2 98 218 23 256 23 4.2 786 16 18 4.8
Unit II of the southern Javakheti Highland, basaltic trachyandesites, northern Shirak Basin, Gelasian
16 20 173 105 30 48 42 77 18 ˂5.0 21 535 31 201 14 ˂3.0 343 6.1 ˂2.0 ˂2.0
17 23 130 62 32 57 56 84 18 4 22 670 28 200 23 ˂1.0 480 11 4 ˂2.0
Basaltic andesite of the Mets-Sharailer volcano, uppermost Calabrian
18 17 173 114 26 73 40 88 15 ˂2.0 40 854 28 230 20 2.7 746 11 7.3 2.5
19 24 152 263 31 180 66 86 15 ˂2.0 26 715 20 143 12 ˂2.0 593 8.0 4.7 ˂2.0
20 24 121 149 22 118 65 85 16 ˂2.0 32 882 19 168 17 ˂2.0 589 7.5 5.0 ˂2.0
Trachyandesite of the northern slope of Aragats, uppermost Calabrian
21 6.5 101 34 5.8 14 25 57 16 2.9 71 402 35 351 25 ˂2.0 778 13 14 3.8
Leninakan trachytic tuffs and ignimbrites, Shirak Basin and the Pambak River upper reaches
22 15 31 13 13 ˂10 13 64 18 7 110 430 39 480 45 4 880 19 19 8
23 12 34 16 15 ˂10 21 61 17 ˂3.0 100 410 38 430 42 4 880 24 24 11
24 7.2 47 15 5.5 17 58 61 16 ˂5.0 97 313 35 469 31 4.2 881 18 14 3.2
25 10 55 19 7.2 14 18 53 16 ˂5.0 100 303 33 456 30 5.3 819 19 14 2.7
26 8.1 56 16 7.3 14 24 61 17 5.3 91 375 31 416 28 4.3 811 18 13 2.8
27 ˂5.0 55 21 ˂5.0 10 18 62 17 4.1 104 244 37 463 36 3.9 927 14 18 5.2
28 8.3 69 35 ˂5.0 17 20 61 16 5.7 97 303 36 433 35 5.5 912 16 16 5.0
Trachytic lavas of the Aragats volcano, correlated to the Leninakan tuff
29 7.0 81 35 5.7 14 24 55 17 3.6 81 400 36 342 26 4.7 906 13 16 4.1
30 12 91 47 11 30 28 63 17 ˂2.0 64 453 25 256 20 4.1 754 12 9.8 ˂2.0
Table B.4
List of GPS coordinates for the main sites of the described units.
Age Unit Site № GPS coordinates Nearest village
Q
21
Arapi unit s 219 40°51.831′N 43°57.468′E Jajur
s 314 40°37.814′N 43°45.336′E Lusaghbyur (Magaridzor gulley)
s 317 40°38.637′N 43°44.507′E Lusaghbyur
s 318 40°32.267′N 43°39.335′E Haykadzor
s 336a 40°48.604′N 43°45.145′E Haykavan
s 341 40°44.939′N 43°50.282′E Gyumri
s 438 40°38.833′N 44°07.490′E Hnaberd
Q
12
– Q
21
Ani unit s 208 40°51.610′N 43°44.954′E Vaghramberd (Leninakan HPP)
s 209 40°52.372′N 43°45.036′E Kaps
s 326 40°49.604′N 43°44.736′E Voghji
s 336 40°48.845′N 43°44.808′E Haykavan
s 339 40°50.726′N 43°45.790′E Marmashen
s 340 40°50.443′N 43°45.500′E Marmashen
Q
11
ol
- Q
12
Karakhach unit s 226 40°54.313′N 43°46.081′E Jradzor
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.quaint.2018.09.017.
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... The largest volcanic structure in this structural zone is Aragats Volcano with a base diameter of 42 km and a height of 4090 m. The presence of parasitic cones on its slope and peripheral volcanic plateaus made it possible to identify the Aragats volcanic region (Shirinyan, 1975), which merges in the west with the Digor volcanic region in the northeastern Turkey (Shalaeva et al., 2019). ...
... and three dates turned out to be satisfactory in this respect. These dates are 3.14 ± 0.10 Ma (sample 2015-322/2 west of Ani station), 3.0 ± 0.2 Ma (sample 2016-419 in a quarry near the village of Anipemza), and 2.8 ± 0.15 Ma (sample 2016-428 opposite the city of Ani) Shalaeva et al., 2019). ...
... Chernyshev et al. [2002] dated the flow as 2.5 ± 0.2 Ma. V.A. Lebedev carried out a more detailed study to give 2.64 ± 0.10 Ma [Shalaeva et al., 2019]. ...
... The successive Ani and Arapi formations are traditionally recognised in the Shirak basin (Sayadyan, 1972). According to the paleontological and paleomagnetic data, the two formations correspond to late Early Pleistocene (the Ani Formation, Fm) and earliest Middle Pleistocene (Arapi Fm) (Sayadyan, 2009;Shalaeva et al., 2019). ...
... Recent study of stratigraphy and neotectonics of NW Armeina based on several reference sections (Shalaeva et al., 2019) brought new diverse paleontological materials. In this contribution we specifically focus on the biotic record of the Ani and Arapi deposits. ...
... Data on Pleistocene diatom assemblages of the Shirak Depression was obtained from the lacustrine diatomaceous deposits of the Ani unit in the sections of Arapi and the Marmashen borehole 6 (Zaikina et al., 1969a, b). Additional diatom materials were recently studied in the Ani sections of Haykavan (lower part) and Arapi deposits of the Haykadzor section (beds 6-7) (Shalaeva et al., 2019). The general revealed trend is from assemblages with higher representation of planktonic forms in lower parts of the Ani Fm towards associations with growing role of bottom and littoral forms higher in the Ani sequences and in the Arapi Fm. ...
... The successive Ani and Arapi formations are traditionally recognised in the Shirak basin (Sayadyan, 1972). According to the paleontological and paleomagnetic data, the two formations correspond to late Early Pleistocene (the Ani Formation, Fm) and earliest Middle Pleistocene (Arapi Fm) (Sayadyan, 2009;Shalaeva et al., 2019). ...
... Recent study of stratigraphy and neotectonics of NW Armeina based on several reference sections (Shalaeva et al., 2019) brought new diverse paleontological materials. In this contribution we specifically focus on the biotic record of the Ani and Arapi deposits. ...
... Data on Pleistocene diatom assemblages of the Shirak Depression was obtained from the lacustrine diatomaceous deposits of the Ani unit in the sections of Arapi and the Marmashen borehole 6 (Zaikina et al., 1969a, b). Additional diatom materials were recently studied in the Ani sections of Haykavan (lower part) and Arapi deposits of the Haykadzor section (beds 6-7) (Shalaeva et al., 2019). The general revealed trend is from assemblages with higher representation of planktonic forms in lower parts of the Ani Fm towards associations with growing role of bottom and littoral forms higher in the Ani sequences and in the Arapi Fm. ...
... The current positions of these lavas were determined largely by the incline and geometry of the ancient relief on which they were originally deposited. Volcanic activity decreased considerably in the Holocene (Chernishev et al., 2006;Golovanova and Doronichev, 2020;Karapetyan et al., 2001;Lebedev et al., 2011Lebedev et al., , 2013Shalaeva et al., 2019;Sherriff et al., 2019;Sosson et al., 2010;Trifonov et al., 2016). ...
Chapter
The Armenian Highlands and Caucasus comprise a pivotal region within the known Neanderthal biogeographic range. This topographically and eco-geologically diverse area is very rich in Middle Palaeolithic (MP) archaeology; however, it is still understudied. This chapter summarises results of recent fieldwork and current data on patterns and variability in MP site contexts, chronology, stone tool manufacture, technological organisation, land use, subsistence practices, and potential symbolic behaviour. MP hunter–gatherers were well adapted to Late Pleistocene mosaic landscapes and environmental-elevation gradients in the area. The spatial and temporal dynamics of the regional Middle to Upper Palaeolithic (UP) ‘transition’ are not fully resolved. Further research is likely to reveal complexity in the timing and nature of the disappearance of the MP and appearance of the UP, with implications for the replacement of Neanderthals by Homo sapiens in the region.
... 1.5-0.75 Ma) and Arapi (0.70 ± 0.05 Ma) units (Sayadyan, 2009;Shalaeva et al., 2018;Trifonov et al., 2017). Each unit is composed of lacustrine-type fine-grained deposits with coarser alluvium at the top. ...
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THE NEW VERSION OF 2021 WILL BE AVAILABLE SOON. The version of 2016 of "Geological (volcanological) map of Javakheti volcanic area (Lesser Caucasus)" is presented. Two-layer geological map of the Javakheti neovolcanic area, Lesser Caucasus (Southern Georgia, Northern Armenia, North-Eastern Turkey), the region with a large manifestation of Neogene-Quaternary volcanism. Scale 1/200000. Compiled by V.A. Lebedev (IGEM RAS) ©. File is in PSD (Photoshop) format. Layers: topography, geology. Version of 2016, #2 (01/09/2016). The map will be updated constantly after publishing of new data. Reference should be given as: Lebedev V.A. Geological map of Javakheti volcanic area (Lesser Caucasus), 1/200000, ed.2016-2. Moscow, IGEM RAS. // V.A. Lebedev, S. N. Bubnov, O. Z. Dudauri, G. T. Vashakidze. Geochronology of Pliocene volcanism in the Dzhavakheti highland (the Lesser Caucasus). Part 2. Eastern part of the Dzhavakheti highland. Regional geological correlation // Stratigraphy and Geological Correlation. 2008. V.16(5). P.553-574.