Stratigraphy and Seismostratigraphy of the Permian Evaporite Formation in the Salt-Producing Province of the Caspian Region: Problems and Solutions

Full text

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ISSN 0869-5938, Stratigraphy and Geological Correlation, 2023, Vol. 31, No. 1, pp. 33–48. © Pleiades Publishing, Ltd., 2023.
Russian Text © The Author(s), 2023, published in Stratigrafiya, Geologicheskaya Korrelyatsiya, 2023, Vol. 31, No. 2, pp. 40–58.
Stratigraphy and Seismostratigraphy of the Permian Evaporite
Formation in the Salt-Producing Province of the Caspian Region:
Problems and Solutions
M. P. Antipova, V. A. Bykadorova, Y. A. Volozha, S. V. Naugolnykha, I. S. Patinaa,
Y. A . P isarenkob, and I. S. Postnikovaa, *
a Geological Institute, Russian Academy of Sciences, Moscow, Russia
b Nizhnevolzhsky Geology and Geophysics Research Institute, Saratov, Russia
*e-mail: postnikova_irina1994@mail.ru
Received January 14, 2022; revised September 6, 2022; accepted September 12, 2022
Abstract—The composition and stratigraphy of the evaporite formation in the salt-producing province of the
Caspian region are discussed. A seismostratigraphic approach is used for correlation of geological sections in
the lateral areas of the salt-producing province with the halokinetically deformed sections in the central areas
of the Preсaspian depression. As a result of this research, a new local stratigraphic scheme of the Permian
evaporite formation of the Central Subprovince is proposed and the principles of its construction using the
results of the seismostratigraphic analysis of the Asselian-Tatarian seismogeological substage and the
accepted serial legends of three groups of sheets of geological maps (scale 1 : 1000000; Scyphian (South-
European), Central-European, and Uralian) are outlined. The results obtained significantly precise the exist-
ing schemes of the oil and geological zoning of the Pricaspian oil and gas province and contribute to the
development of the resources of the deep (subsalt) horizons of its sedimentary cover.
Keywords: Pricaspian Depression, correlation, Permian system, Kungurian stage, Filippovian horizon, Ire-
nian horizon
DOI: 10.1134/S0869593823020016
PROBLEMS OF STRATIGRAPHY
AND MAPPING OF EVAPORITE FORMATION
The Permian evaporite formation of the salt-pro-
ducing province of the Caspian region is overlain by a
thick cover of post-salt deposits and is a very difficult
object for stratigraphy of its section, including the
making of local stratigraphic schemes. The outcrops of
the formation are few and are confined to the arches of
individual salt anticlines complicating the western
slope of the Ural orogen and the northeastern slope of
the Donbass-Tuarkyr folded system, as well as to the
arches of several salt domes of the Pricaspian Depres-
sion. In the Early Permian, the Pricaspian basin was
located in the arid climate zone of Pangea (Fig. 1).
The evaporite formation along the periphery of the
salt-producing province overlies over the eroded sur-
face of various Carboniferous and Lower Permian
horizons represented by marine terrigenous and car-
bonate rocks. In the deep parts of the Pricaspian
Basin, there is no gap in sedimentation before the for-
mation of a salt-bearing formation, according to our
ideas, as well as the data of a few wells in the central
part of the basin. The Permian evaporite formation is
distinguished by its internal structure being sharply
disharmonious in relation to the structure of the
underlying (pre-salt) and overlying (post-salt) depos-
its. Therefore, the formation is reliably recognized in
deep and time seismic sections obtained using the
common depth point (CDP) method, which makes it
possible to reliably document the boundaries of its dis-
tribution below the cover of thick post-salt strata.
The identification of geological formations is an
important element in compiling tectonic maps and
clarifying the tectonic development of a region
(Kirikov et al., 2017). Moreover, formational analysis
should be widely used as a method of stratigraphy
allowing the reconstruction of paleogeographic and
tectonic settings, development stages, and types of
structures corresponding to the identified formations
(Leonov, 1974). We consider the evaporite formation
of the Caspian region according to N.S. Shatsky, who
referred to geological formations as “such natural
assemblages, communities or associations of rocks,
the individual parts of which (rocks, beds, suites) are
closely paragenetically related to each other both in
age (succession, interbedding) and in spatial terms
(facies changes)” (Shatsky, 1965). Shatsky considered
the formational analysis and the study for the forma-

34
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
tions as regional stratigraphic units using geological
methods to be very important.
To make the paper better-adapted for researchers
from Russia and abroad, we are explaining some of the
terms used below. In English and Russian literature,
there are basic differences in the interpretation of the
terms “salt tectonics” and “halokinesis” (Kosygin,
1950; Volozh et al., 2003; Antipov and Volozh, 2012;
Belenitskaya, 2020; Pisarenko and et al., 2021a,
2021b). In English-language publications, these are
synonyms describing the processes of formation of
disharmonious structures, due to the salt rising into
their domes. However, the reasons causing salt move-
ments are not usually considered. Disharmonious
structures can be produced by any forces, regardless of
their nature. These can be both external forces of com-
pression or tension applied to the entire section of the
sedimentary cover, and forces arising within the salt
strata in the process of their subsidence into the zone
of high temperatures and lithostatic pressure. In Rus-
sian-language publications, these two terms denote
fundamentally different concepts. The concept of salt
tectonics is broader than halokinesis. Halokinesis is
understood as a special form of salt tectonics, which
manifests itself, “when the flow of salt is caused
solely by gravity, i.e., a decrease in potential gravita-
tional energy in the absence of significant lateral tec-
tonic forces” (Kosygin, 1950). Unlike the salt tecton-
ics, which manifests itself in all salt-bearing basins,
halokinesis is only noted in those where the deposi-
tional thickness of the halogen sequence exceeds
1.5 km. It has been established that in most salt basins
the accumulation time of the halogen formation is
quite short (Pisarenko et al., 2011). Since salt strata
accumulated in shallow water bodies, the processes of
halokinesis can only occur in pools that sink at a rate
of at least 10 cm per 1000 years. Similar conditions are
observed in f lat-bottomed shallow basins of passive
continental margins and intracontinental rifts, as well
as in the graben-type epicontinental basins. The last
type includes the Kungurian Pricaspian basin.
It is noteworthy that the disharmonious structures
developed within the salt basins, where the salt move-
ment is caused exclusively by salt tectonics, differ from
the structures formed in the salt basins affected by the
processes of halokinesis. For the former, the rule
applies that any structural complication at the top of
the salt-bearing strata is accompanied by a complica-
tion in its base. In addition, only disjunctive extension
dislocations (faults) are recognized in the post-salt
complex of halokinetic structures (Antipov and
Volozh, 2012). The type of salt tectonics, in which
deformations are caused by tectonic forces, here will
be called tectonohalokinesis. Halokinesis manifested
Fig. 1. Paleotectonic map of the Permian stage of development of Pangea (Torsvik and Cocks, 2017), combined with the litho-
logical-climatic map (Boucot et al., 2013) (modified after Trapeznikov, 2019).
AmuriaAmuriaAmuria
Arid
Arid
Baltic
BalticBaltic
NeotethysNeotethysNeotethys
PaleothetysPaleothetysPaleothetys
PangeaPangeaPangea
Panthalassa Panthalassa Panthalassa
Panthalassa
Panthalassa Panthalassa
Caspian
Depression
Caspian
Depression
Caspian
Depression
Temperate
Temperate
Siberia
SiberiaSiberia
Warm
Warm
Tropical
Cold
Tillites
Dropstone
Glendonite
Coal
Boxite
Kaolinite
Laterite
Evaporites
Сalcicrete

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 35
itself exclusively in the territory of the Pricaspian
depression, and tectonohalokinesis is observed within
the adjacent tectonically active structures at that time.
Currently, several variants of stratigraphic scales
are used in geological mapping for the Permian stra-
tigraphy of the salt-producing province in the Caspian
region: (1) the International scale of 2004 and its ver-
sion of 2019; (2) General stratigraphic scale of Russia
and regional scale of the southern and southeastern
regions of the East European Platform, approved by
the Interdepartmental Stratigraphic Committee
(ISC) of the Russian Federation (ISC RF) in 2019;
(3) local stratigraphic scales compiled for the legends
of three groups of sheets of geological maps at a scale
of 1 : 1 000000: the Scythian (South European), Cen-
tral European and Ural structural-formation zones (as
accepted by ISC of Russia in geological mapping)
(Gogin et al., 2015), which includes various regions of
the Permian salt province.
During the last two decades, the divisions and sub-
divisions of the Permian system of the general and
regional stratigraphic schemes of Russia have under-
gone significant changes. The ISC of Russia, follow-
ing the decisions of the International Commission on
Stratigraphy, adopted a tripartite division of the Perm-
ian system. The Ufimian Stage was assigned to the
lower (Cisuralian) series of the Permian, the Tatarian
Stage became a series, and the Kazanian and Urzhu-
mian stages were combined into the middle (Biarm-
ian) series. However, such a decision is sharply contra-
dicted by the existing principles of priority and reli-
ability (Lozovsky et al., 2009). The Tatarian Series
contains four stratigraphic “horizons” (regional sub-
stages), united in pairs into the Severodvinian and
Vyatkian stages. Corresponding changes, along with
numerous corrections in the stratigraphy of sections of
individual facies zones, were also introduced into the
legends of serial groups of sheets of geological maps.
At the same time, as the authors of these legends
themselves note, it was not possible to reach a consen-
sus on the division of sections of facies zones contain-
ing deposits of the Permian evaporite formation of the
salt-producing province of the Caspian region, due to
objective reasons (geological features of the region and
methods of subdivision and correlation of sections)
(Gogin et al., 2015). Firstly, within the boundaries of
the salt-producing province, the deposits of the evap-
orite formation are available for study by direct geo-
logical methods exclusively using deep drilling, since
in most of the territory of the province the base of the
formation lies at depths of more than 7 km. Secondly,
there are problems and difficulties associated with the
discovery of fossils in saliferous strata. Only palyno-
logical assemblages and remains of ostracods have
been locally identified in the borehole core, which
make it possible to identify the Kungurian and Kaza-
nian beds, but it is not possible to determine the
sequence of bedding of rhythmic units within the
Upper Artinskian–Kungurian sedimentary succes-
sion, and often even to reliably substantiate their rec-
ognition (Derevyagin et al., 1981). Thirdly, when con-
structing local stratigraphic schemes, the subdivision
of individual sections of the evaporite formation and
their correlation are carried out using rhythmostrati-
graphic methods, with the identification of cyclic layer
associations of three ranks: rhythm packs, rhythmic for-
mations (series), and rhythmic groups. However, the
analysis of the available schemes shows that even in the
peripheral regions of the salt-producing province, well-
studied by drilling, and where the primary bedding
sequence is not affected or only slightly disrupted by the
processes of salt tectonics, the method of rhythmostra-
tigraphy is only effective when identifying large subdivi-
sions rank of groups and formations (Fig. 2).
A fragment of the time seismic section (Fig. 2) shows
the structure and seismostratigraphic units of the sedi-
mentary cover of the Central Pricaspian Subprovince,
which include dislocation and geodynamic seismic
assemblages, seismogeological storeys, and seismic
assemblages. It is impossible to distinguish and cor-
relate small lithostratigraphic units inside the salt (evap-
orite) dislocation seismic complex. The section of the
evaporite formation is considered as a whole without
subdivisions. Using seismic methods, the sedimentary
cover is subdivided into seismic complexes and seismo-
geological storeys corresponding to different stages of
development of the sedimentary cover.
The rhythm packs identified from drilling data are
hardly recognizable being correlated in seismic sec-
tions in the shelf part of the Pricaspian salt-bearing
basin, where the sequence is not disturbed by haloki-
nesis processes. Drilling data indicate the presence of
erosional and depositional hiatus in the section of this
sequence. This is clearly observed on fragments of
time seismic profiles in the Western and Northwestern
sub-provinces using high-resolution seismic surveys
(Pisarenko et al., 2021a, 2021b). The nature of the
wave pattern in the seismic sections indicates numer-
ous gaps and erosion episodes in the process of accu-
mulation of the evaporite strata in the shelf environ-
ments (Figs. 2, 3), which are difficult to trace laterally.
Deep seismic stratigraphic sections (Fig. 4) clearly
show the parallel-layered shelf Kungurian series pass-
ing into deformed rocks in the central part of the
basin, losing their bedded structure and having been
affected by halokinesis processes, and forming domes
2–4 km wide, the internal structure of which cannot
be reconstructed using seismic and geological data.
Even though the sequence of rhythmic units and even
their number are interpreted differently by different
researchers, it is possible to compare the alternating
carbonate and sulfate packages of the Kungurian Stage
(especially the packages at the top of the Irenian Hori-
zon in the Kungurian Stage stratotype) with the rhyth-
mic packages of the peripheral parts of the Pricaspian
Depression, the general structure which are shown in
Fig. 5 (for details see: Stepanov, 1951; Tikhvinskaya
et al., 1967; Chuvashov and Dyupina, 1973; Sofro-

36
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
nitsky et al., 1974; Sofronitsky and Zolotova, 1988;
Chuvashov et al., 1990, 2002; Sofronitsky and Ozh-
gibesov, 1991; Chuvashov, 1997; Naugolnykh, 2007,
2017, 2018, 2020). This comparison is confirmed by the
general sequence of paleogeographic events that took
place within the entire western side of the Urals during
the Permian period. Even if we assume the existence of
isolated depressions within these salt basins, starting
from the second half of the Kungurian (Early Permian),
their depositional features reflected the same geological
(mainly paleoclimatic) events in the same succession
(the principle of stratigraphic homotaxiality or the
Smith–Huxley principle (Meyen, 1989)).
This explains the correspondence between the
number and sequence of members of the Kungurian
Upper Irenian Horizon in its stratotype and the num-
Fig. 2. A fragment of the seismostratigraphic section in the central part of the Pricaspian Depression showing the subdivision of the
sedimentary cover with recognized seismic complexes (SC), seismogeological storeys (SGS), dislocation (DsSC) and geodynamic
(GdSC) seismic complexes. Indices in circles designate reference reflecting seismic horizons as boundaries between seismic strati-
graphic complexes. The letters in the rectangles indicate the stratigraphic age of the seismostratigraphic complexes. Seismogeologi-
cal storeys and substoreys are highlighted in color in the section. The position of the section is shown in Fig. 4.
SC SGS DsSC
GdSC
Seismostratigraphic units
Jurassic–
Paleogen e
Post-saltSubsalt
Upper
Permian–Triassic
Salt
Kungurian–
Kazanian
Middle
Carboniferous–
Lower Permian
Devonian–
Lower
Carboniferous
Lower
Paleozoic
Pre-Plate Plate
Refraction horizon
Top of consolidated crust
V = 6.2–6.4 km/s
1
2
3
4
Т, s
VI
VI
VI
VI
VI
VI VI
II II II
II
a
II
a
II
a
III
a
III
a
III
a
III III III
P1k
V1V1V1V1
VI
P2
P2P2
Kn
KnKn
K
n
K
1
K1–2
P1k2
P
1
k
2
1-K2
P1k2
P1k1
P
1
k
1
P1k1
C
3
-P
1
C3-P1
П1
П2
П
2
П
3
П
Ф
П
1
П
2
с
П
2
с
П
2
-П
3
d
D-C
1D-C1
PZ1
C
2–3
J2–3
J
3
C
2–3
T
TTT
D
DDD
Fig. 3. A fragment of a time seismic section within the Northwestern Subprovince of the Pricaspian oil and gas province. The cha-
otic wave pattern of the seismic record inside the evaporite formation (the seismic complex between the crimson and orange hori-
zons) indicates numerous gaps in the process of accumulation of salt-bearing rocks, where, according to drilling data, several
rhythmic units of the salt-bearing strata are identified. The yellow arrows inside the saline formation indicate the transgressive
boundary with the underlying sediments, the blue arrows indicate truncation of the saline bed at the base. The indices in the rect-
angles are the stratigraphic age of the seismic complexes. Indices in circles are designations of reference reflecting horizons. The
position of the profile is shown in the inset in Fig. 4.
500
600
700
800
900
1000
Т, ms
500
600
700
800
900
1000
Т, ms
W E
2 km
VI
V2
VI
P1
P2-T1
P1k
C3
V2
V1
J1
П1
П1
'
П1
T2–3

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 37
ber and sequence of rhythmic units in the upper part of
the Kungurian Stage in the peripheral sections of the
Caspian Sea. Great difficulties arise in the correlation
of local stratigraphic units of the Permian section of
peripheral territories with units of the central regions
of the salt-producing province, where the sedimentary
structure of the evaporite formation has been
reworked by halokinetic processes. Therefore, the data
on the rhythmicity of the halogen sequence, which
forms the core of the salt structures, are of little use for
stratigraphy. Here, it is often not possible to reliably
substantiate even the identification of series and for-
mations within the Upper Artinskian–Kungurian
lithostratigraphic complex (Derevyagin et al., 1981;
Pisarenko et al., 2000, 2011, 2017; Svidzinsky and
Baranovskaya, 2015) (Fig. 5). Correlation of the strati-
graphic sections of the Lower Permian evaporite for-
mation during the geological mapping of the Pricas-
pian depression shows that because of the processes of
halokinesis it is impossible to develop a unified
scheme of stratigraphy and correlation for formations
and groups using geological methods. It is also diffi-
cult to use undeformed evaporite formations for cor-
relation, as can be seen from Fig. 5b, where different
authors identify rhythms and formations of different
names and stratigraphic ranges. Formations and
rhythms are recognized by the nature of the alterna-
tion of different compositions of salt minerals in the
section, as well as by the data of well logs obtained
during geophysical studies of boreholes.
In the central part of the Pricaspian depression,
during geological mapping within the stratigraphic
horizons of the Kungurian, the formations are often
identified under different names (Fig. 5a). In the
periphery of the depression in the section of the Ire-
nian Horizon, rhythms are recognized in the rank of
formations, the names of which depend on the specific
area of study. Recognition of rhythms or formations in
the central regions of the basin, where salt structures
are common, and their correlation with the marginal
parts is impossible, since the section is dislocated, and
all primary relationships are violated (Fig. 4).
FORMULATION OF THE SCIENTIFIC
PROBLEM AND METHODS
FOR ITS SOLUTION
Currently, there is no satisfactory regional strati-
graphic scheme for the section of the salt-producing
province of the Caspian region. The main reasons for
this are: (1) the ambiguity and difficulty of the strati-
graphic subdivision of the evaporite formation, (2) the
existence of local stratigraphic schemes only for areas
with a weak manifestation of salt tectonics processes.
Data on the structural features of the lower boundary
of the evaporite formation and on the nature of the
complexes above and below this boundary are of key
importance in solving this problem. It is important to
know: (a) whether there is evidence of a stratigraphic
hiatus, and if so, how long it lasted; (b) presence and
Fig. 4. The structure of the Kungurian evaporite formation in the western side of the Pricaspian Depression. Symbols for the
map: 1—the border of the Astrakhan Dome; 2—shelf break of the Early Permian carbonate shelf and intra-basin platforms;
3—shelf breaks of the Visean-Bashkirian carbonate shelf and intra-basin platforms; 4—faults; 5—position of seismostrati-
graphic sections given in the text; 6—the state border of Russia and Kazakhstan.
–1
0
–2
–3
–4
–5
km
Pricaspian Syneclise
Pricaspian
Syneclise
NW SE
Sarpinsky Trough
Karpinsky Ridge
CASPIAN SEA
Volga R.
45q E
Karakul-Smushkov Zone
Astrakhan
Arch
Sarpinsky Trough
Karasal monocline
Karasal
monocline
Fig. 4
Volgogard
Astrakhan’
Fig. 3 Fig. 2
Fig. 2
48q N46q
48q
1
2
3
4
5
6
0 50 100 150 200 km 0 5 km
K-N K-N
JJ
P2-T
P2-T
P1k
P1k
P1k
P1a

38
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
type of unconformity (structural, erosional, strati-
graphic). The significance of this information increases
in the zones of transition from the peripheral to the cen-
tral regions of the province, where the base and top of
the evaporite formation lie at depths of 4 to 7 km, and
the necessary data can only be obtained using seismic
stratigraphy methods. The presence in the section of the
Middle Carboniferous-Permian seismogeological sto-
rey of the sedimentary cover of the Caspian region of a
disharmoniously constructed evaporite formation and
the type of its deformations (tectonic folded or stamp
and halokinetic) are unambiguously diagnosed on the
time and depth dynamic seismic sections of the CDP
during a visual analysis of the relationships between
seismostratigraphic units. Therefore, the boundaries of
the Permian salt-producing province and its sub-prov-
inces are established with a high degree of reliability and
are easily mapped. Analysis of time and depth seismic
sections within the Pricaspian Depression shows a wide
range of types of structures common in the Lower
Permian evaporite formation and described in numer-
ous publications (Volozh et al., 1997). It should be
noted that such criteria as the type and nature of defor-
mations, as well as the time of their manifestation, allow
not only to determine the position of the boundaries of
subprovinces and perform their typification taking into
account these two parameters, but also to draw prelim-
inary conclusions about the lithofacies type of the sec-
tion (sulfate, chloride) of a disharmonious evaporite
formation.
Thus, when developing regional and local strati-
graphic schemes for a salt-producing province, a seis-
mostratigraphic approach should be used for stratigra-
phy of the evaporite formation and seismogeological
zoning of the province. We implemented this approach
for compiling a 4D seismostratigraphic model of the
Earth’s crust of the Caspian region in order to identify
the Permian disharmonious evaporite formation in the
section of its sedimentary cover and study its structure
(Antipov et al., 2004; Osadochnye…, 2004).
STRUCTURE OF THE PERMIAN EVAPORITE
FORMATION ACCORDING TO THE RESULTS
OF SEISMOSTRATIGRAPHIC STUDY
In recent years, as a result of the joint interpretation
of CDP seismic and gravity geophysical survey data,
the boundaries of the distribution of the Permian
evaporite formation of the salt-producing province of
the Caspian region have been significantly revised,
and its stratigraphic range has also been expanded.
Fig. 5. Examples of stratigraphic subdivision of sections of the evaporite formation of the Pricaspian depression in its various
parts; (a) stratigraphy of the Kungurian section of the central part of the basin according to different authors; (b) comparison of
the rhythmostratigraphic units of the rank of formations and units identified by different authors for the northern and western
marginal zones of the Pricaspian depression.
Horizon Horizon
(a) (b)
Pisarenko et al.,
2000
Gogin et al.,
2015
Zhitkur
Formation
Zhitkur
Formation
Ulagan
Formation
Irenian
Irenian
Ulagan
Formation
Volgograd
Formation
Volgograd
Formation
Filippovian Kotelnikov
Formation
Saraninian Section
not studied
in boreholes
Gorodovikovsk
Formation
Sarginian Kanukovo
Formation
Pisarenko et al.,
2000, 2011
Formation (rhythmic set)
Ozersk
Eruslan
Dolinnaya l
Pigarevskaya
n
Antipovskaya i
Pogozhskaya h
Timoninskaya
(Lugovskaya)
Balykley
(Krasavskaya)
Volgograd
g
m
k
f
2–3
f
1–2
Svidzinskaya
and Baranovskaya,
2015
Rhythmic set
Eruslan X
Dolinnaya IX
Pigarevskaya
VIII
Antipovskaya VII
Pogozhskaya VI
Lugovskaya
Privolzhskaya
Karpenskaya
Balykley
V
IV
III
II
Volgograd I

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 39
According to the nature of dislocations, the Kun-
gurian–Cenozoic section of the Pricaspian salt basin
is subdivided into three dislocation storeys. A number
of quasi-synchronous seismostratigraphic complexes
are distinguished in them: a salt-bearing one that fills
the cores of domes; prekinematic; early synkinematic,
synchronous to a stage of growth of salt domes and
performing primary compensatory synclines; late syn-
kinematic, synchronous stages of growth of salt diapirs
filling secondary compensatory synclines; and post-
kinematic.
The lower storey covers mainly the halogen com-
plex of the Kungurian, or rather, that part of it that
forms the core of the salt structures. The internal
structure of this storey is determined by the flow folds
of a very complex configuration. The upper boundary
of the storey on seismic sections is distinguished by a
change in the nature of the reflection pattern. Seismic
horizon VI, associated with this boundary, is traced, as
a rule, only at the tops of salt cores (Fig. 2).
The middle level consists of rocks of separate iso-
lated synclines and depressions between the cores of
salt domes.
These deposits accumulated in the course of
halokinetic movements of the salt-bearing series.
Their internal structure is quite complex. Here, the
prekinematic and synkinematic beds of several gener-
ations (compensation synclines of the first and second
generations) are distinguished, differing in the pattern
of internal bedding, which is clearly seen in the time
seismic sections (Fig. 2).
Prekinematic beds were formed before the start of
halokinetic movements. In the process of halokinesis,
their shape underwent significant changes, but the
thickness of the beds remained unchanged or changed
insignificantly. The synkinematic beds accumulated
simultaneously with the movement of the salt. They
are characterized by a local increase in the thickness of
individual beds in the zones of salt outf low and the
appearance of leaning beds or their truncation. The
moment of the appearance of synkinematic beds in the
section marks the time of the beginning of the growth
of the salt core.
The upper storey is formed by a cover of weakly
deformed deposits (post-kinematic beds).
Structurally, vast inter-dome zones dominate here,
which frame isolated domes. This background is com-
plicated by separate local, disjunctive troughs, leaning
or superimposed on salt cores. A distinctive feature of
the post-kinematic beds is the consistent thickness of
the constituent layers (except for disjunctive troughs).
Post-kinematic beds accumulated when the salt domes
stopped growing. The growth stages of salt domes are
displayed and recorded in stratigraphic sections of
intersalt synclines (Volozh et al., 1997).
The boundaries between the upper and middle dis-
location storeys are clearly traced on time seismic sec-
tions as surfaces of stratigraphic and angular uncon-
formity (Fig. 2). Analysis of seismic data shows that
the stratigraphic position of this boundary within the
Pricaspian depression is variable. Thus, within the
eastern and southern marginal zones, it passes at the
level of the base of the Triassic deposits. In the south-
eastern marginal zone, it moves to the base of the
Jurassic deposits. The change in the position of this
boundary is fixed in a very narrow zone, which is dis-
played in the section as a flexural bend of the base of
the Triassic and is accompanied by a considerable
increase in the thickness of the Triassic deposits.
Towards the center of the Pricaspian depression, the
Jurassic-Triassic boundary gradually becomes less dis-
tinct structurally. Here, the structural-erosive uncon-
formity at the base of the Pliocene-Quaternary com-
plex, becomes most distinct. The position of this
boundary indicates that its stratigraphic position in
the section is determined by the patterns of halokine-
sis, rather than by deep geodynamic processes.
In seismogeological zoning, the stages of halokine-
sis (the time of the beginning and completion of the
first and second storeys) and the morphogenetic types
of salt structures are taken as a criterion. The category
of salt structures in our understanding includes all dis-
harmonious structures, the cores of which are com-
posed of salt. At the same time, salt pillows, salt domes
and salt stocks are assigned to the class of halokinetic
structures, and salt anticlines and stamp (embryonic)
salt structures are assigned to the class of deformation
structures. Below are the results of our seismostrati-
graphic analysis of the available geological and geo-
physical data for the territory of the region (time and
deep dynamic sections of the CDP in conjunction
with seismogeological sections obtained using correla-
tion method of refracted waves (CMRW) and gravim-
etry data).
The study resulted in a seismostratigraphic frame-
work of a 4D model of the Permian evaporite forma-
tion of the salt-producing province of the Caspian
region, accompanied by a scheme of seismic geologi-
cal zoning of the province (Fig. 6). A sedimentation
model of the evaporite formation along the profile
through the northern edge of the Pricaspian Devo-
nian–Early Permian deep-water basin was also cre-
ated. It was compiled taking into account the accumu-
lation of the Frasnian-Lower Bashkirian and Bash-
kirian-Lower Permian seismogeological storey of the
platform geodynamic seismic complex.
The results obtained made it possible: (a) to estab-
lish the boundaries of the salt-producing province;
(b) to reveal the degree and nature of deformations of
the Permian evaporite formation, as well as the nature
of its relationship with the overlying and underlying
complexes; (c) to reconstruct the topography and
depths of the salt basin at the beginning of the Early
Permian and in the Middle Permian, based on the
structural features of the lower and upper boundaries
of the formation and data on its composition;

40
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
Fig. 6. Seismostratigraphic framework of the 4D model of the Permian (Upper Asselian–Lower Tatarian) disharmonious evap-
orite formation of the Pricaspian salt-producing province. Legend for the main figure: 1—undivided subsalt seismic complexes:
a—shallow-water (coastal-sea and inner shelf), b—deep-water (outer shelf and basin); 2—post-salt seismic complexes without
division by ranks; 3—deposits of the Permian disharmonious evaporite formation, tectonically deformed, with the formation of
structural forms: a—folded type (salt diapirs), b—stamp type; 4—sediments of the Permian disharmonious evaporite formation,
halokinetically deformed, with the formation of cores of salt domes and diapirs, composed of Kungurian halite (a), Kungurian
halite and Middle Permian recycling terrigenous-salt-bearing strata (b); 5–8—composition of subdivisions of local stratigraphic
scales of the evaporite formation identified during the seismostratigraphic analysis of its section and the section of the age seis-
mostratigraphic subdivision containing the formation: 5, 6—local lithostratigraphic subdivisions of large ranks: 5—sulfate type:
a—sulfate-terrigenous composition, b—sulfate-carbonate composition; 6—halogen type of different composition: a—halogen,
b—sulfate-halogen, c—carbonate-halogen; 7—sequences of predominantly carbonate (a) or terrigenous (b) composition with
evaporite interbeds; 8—recycling complex; 9–11—composition of subsalt seismic complexes: 9—terrigenous-carbonate, 10—
carbonate, 11—terrigenous; 12, 13—boundaries of the evaporite formation (12)—lithostratigraphic subdivisions such as series
and formations (13) recognized seismostratigraphically and lithologically (a), only lithologically (b); 14—absence of deposits
associated with regional uplift and erosion of sediments (a) and with slope erosion (b); 15—gap in sedimentation (no-sedi-
ment); 16—surface of slope erosion. Symbols for the zoning scheme (inset): 17—sub-provinces: A—Northwestern, B—Central
(salt dome), C—Eastern, D—Southeastern, E—Southwestern; 18—regions: I—Volga–Kama, II—Buzuluk–Orenburg, III—
Karasal–Sol-Iletsk, IV—Aralsor–Khobda, V—Sarpinsky–Aktyubinsk, VI—Astrakhan–Temir, VII—Ural, VIII—Aral–Cas-
pian, IX—Kurmangazy–Karakul; 19—border of the Caspian salt-producing province; 20—modern boundaries of the distri-
bution of the evaporite formation; 21—borders of sub-provinces; 22—borders of regions. The question mark denotes a pro-
posed (virtual) boundary between lithostratigraphic units.
International
Stratigraphic
Scale
(ICS)
Regional scales
of the
East European
Platform
General
Stratigraphic
Scale
(GSC)
Age, Ma
Age, Ma
System
Series
Series
Stage
Substage
Stage
Stage
Horizon
Northwest ern
Subprovince
Lopingian
Wuchiapingian
Changhsingian
Tatarian
Lower Upper
Vyatkian
Vyatkian
Nefedovian
Bykovian
Volga-
Kama
Region
Buzuluk-
Orenburg
Region
Permian
Guadalupian
Roadian Wordian Capitanian
Biarmian
Kazanian
Kazanian
Urzhumian
Urzhumian
Severo-
dvinian
Severo-
dvinian
Low. Low.Upp. Upp.
Kungurian
Kungu-
rian
Kungu-
rian
Cisuralian
Cisuralian
Asselian
Asselian
Asselian
Sakmarian
Sakmarian
Sakmarian
Artinskian
Artinskian
Artinskian
Ufi-
mian
Ufi-
mian
Kholodno-
lozhian
Shikanian
Tastubian
Sterlitamakian
Burtsevian
Irginian
Sarginian
Saraninian
Filippovian
Irenian
Solikamskian
Sheshmian
Nemdian
Povolzhian
Urzhumian
Sukhonian
Putyatian
Salt-bearing province of the Caspian Region
Central Subprovince
(Salt Dome)
Eastern
Subprovince
South-
eastern
Subprovince
South-
western
Subprovince
Karasal-
Sol-Iletsk
Region
Aralsor
Khobda
Region
Sarpinsky-
Aktybinsk
Region
Astrakhan-
Temir
Region
Cisuralian
Region
Aral-
Caspian
Region
Kurmangazy-
Karakul
Region
А
А
А
B
B
С
С
D
D
E
E
rc
rc
rc
rc
rc
аааааа
аа
bbb
bb b
bb
с
251.9
254.14
259.1
265.1
268.8
272.95
283.5
290.1
293.52
298.9 298.9
251.9
265.1
270.6
283.5
290.1
293.52
I
I
I
II
II
III
III
IV
IV
V
V
VI
VI
VII
VII
VIII
VIII
IX
IX
?
?
Sk
Sk
StStSt
St
St
St
St
St
St
Sk
Sk
Sk
Sk
St
GsGsGs
Gs
G
G
GG
G
Gk
Gk
12345 678 9 1011
12 13 14 15 16 17 18 19 20 21 22
100 50 0 100 km
CASPIAN SEA
50q
50q
N
E
48q
48q
48q
46q
46q
46q
52q
50q
48q
46q
52q
52q60q
58q
58q
56q
56q
54q
54q
44q
44q42q

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 41
(d) reconstruct the primary sedimentary structure and
thickness of the formation; (e) significantly refine the
paleogeographic setting within the salt-producing
province and sedimentation conditions both within
the actual Pricaspian Devonian–Early Permian deep-
water basin and along its periphery (Atlas…, 2002;
Orenburgskii…, 2013; Antipov et al., 2015).
According to the results of seismostratigraphic
analysis, paragenetic relationships were also revealed
between the nature of the subsalt substrate (deposits of
a shallow, deep shelf and deep-water basin), the litho-
facies composition of the evaporite formation (mainly
sulfate or halogen) and the type of leading process
(tectonohalokinesis or halokinesis) responsible for the
disruption of the primary depositional sequence of
salt-bearing strata. The established patterns made it
possible to determine the parameters that were used in
the zoning of the salt-producing province of the Cas-
pian region according to the types of sections and
structures of the evaporite formation, with the recog-
nition of sub-provinces and areas within them. The
sections of the subprovinces differ in such parameters
as (a) the nature of the subsalt substrate, (b) the age
range of the formation, (c) the type of salt structures
(stamp dome-shaped salt uplifts, salt anticlines, salt
domes, and diapirs).
The main distinguishing parameter of the sections
of the regions is the lithofacies composition of the
largest subdivisions of local stratigraphic schemes
(lithostratigraphic complexes), as well as their total
number in the section of the formation. According to
the values of these parameters, the territory of the salt-
producing province of the Caspian region is divided
into five sub-provinces, four of which (South-West-
ern, South-Eastern, Eastern and North-Western) are
located along the periphery of the Pricaspian Devo-
nian-Early Permian deep-water basin and one, Cen-
tral, confined to a deep-water basin (Fig. 6, inset).
Within the Southwestern Subprovince, the evaporite
formation is part of a folded geodynamic seismic com-
plex that fills the marginal trough of the Late Paleo-
zoic Donbass–Tuarkyr folded structure, which was
subsequently deformed in the Pre-Jurassic time. This
complex crowns the section of the upper seismogeo-
logical substage of the Middle Carboniferous-Perm-
ian seismogeological storey. The age of the formation
itself has not been reliably established. However,
according to the results of seismostratigraphic analysis
in this region, it is shown that the seismic complex,
which includes evaporites, is underlain by the Upper
Carboniferous, and overlain by Triassic deposits.
Directly on the Kurmangazy Field (Fig. 7), the dis-
harmoniously built seismogeological substorey is
delineated from below by the seismic horizon “П11”,
which is correlated in the west, on the northern slope
of the Karpinsky Ridge, with the “C3” horizon (top of
terrigenous deposits of the Upper Carboniferous), and
in the east, in the northern side of the South Buzach-
inskii trough, with the VI1 horizon (the base of the
Permian). The evaporite formation is overlain by
Upper Permian, Mesozoic, and Cenozoic deposits.
Thus, we estimate the probable age of the seismic
complex across the region as Permian. At the same
time, we assume that individual local stratigraphic
units, composed of evaporites, can be separated, gen-
erating in the section of the formation separate lentic-
ular bodies of differing age. According to the available
geological data, in the extreme west of the subprovince
(Pre-Donets trough), its stratigraphic range is limited
by the upper part of the Asselian Stage to Artinskian
Stage (Movshovich, 1977; Stratigraficheskie…, 1993),
and to the east, within the western limits, the Karpin-
sky Ridge was wedged, the Artinskian–Kungurian
stages (Gosudarstvennaya…, 2009). Further east,
already within the neighboring subprovinces, Permian
evaporites are known at a higher stratigraphic level, in
the Middle Permian (Pisarenko et al., 2021a, 2021b).
On this basis, and also taking into account that the
evaporite formation of the Southwestern Subprovince
is underlain by shallow shelf deposits and overlapped
by continental ones, it is logical to consider its strati-
graphic range from the upper part of the Asselian
Stage to the Kazanian Stage inclusive. In addition, the
results of seismostratigraphic analysis indicate the
presence of the Permian evaporite formation in the
section of the sedimentary cover of not only the West
Turan, but also the Scythian seismogeological prov-
ince, at least within the northern part of its Donbass-
Tuarkyr seismogeological region (Volozh et al., 2015).
In the Southeastern Subprovince, the evaporite forma-
tion is located within the preplate geodynamic seismic
complex of the West Turan Platform. A disharmoni-
ously built seismic complex (presumably evaporitic,
since, according to gravimetric data, it has lower densi-
ties than the overlying strata) with a thickness of a few
hundred meters, bounded from below by horizons “b”
or “a”, and from above by horizons VI or (TVn), stands
out within the pre-platform geodynamic seismic com-
plex of the sedimentary cover in the region of Northern
Ustyurt within the Mesozoic-Cenozoic Samsky, Kula-
jat and Kultuk troughs and in the Qulba trough.
Its characteristic feature is the presence of local
“swells” of thickness with the formation of small
domes complicated by small faults (Begsh, Amanzhol,
Tyshkanda, Harai structures). There are no clear neg-
ative gravimetric abnormalities over such swells,
therefore, clay-saliferous or clay-anhydrite composi-
tion of its components can be assumed. Biostrati-
graphic data on the age of breeds of a disharmonically
constructed seismic complex is absent. However, in
the Sudochiy Trough the Borehole 1 Eastern Alam-
bek, at a depth of 4200 m, shows the deeper-water
facial and supposed synchronous equivalents of this
seismic complex, represented by black horizontally
bedded argillite with interbeds of marl. Here A.M. Pav-
lov and A.A. Savelyev identified the ammonoid

42
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
Popanocras hanieli Smith (Kalugin et al., 1981; Volozh
et al., 2015), which, in their opinion, is Kungurian-
Ufimian is age (for more details, see: Kalugin et al.,
1981, p. 74; the ammonoid name in Kalugin et al., was
published with typos). Considering that in a section
exposed by the borehole the seismic complex is incon-
sistently overlain by the red-colored Upper Permian–
Triassic deposits, it should be dated as Kungurian–
Kazanian rather than Kazanian.
It should be noted that the presence of Permian salt
deposits in the section of the sedimentary cover on the
territory of the West Turan Platform is currently proved
by drilling. Thus, in the South Ustyurt in Daryalyk–
Daudan Trough in the structure of the Erburun on the
Shordzhinsky Uplift, saline strata up to 450 m thick
(Antipov et al., 2015). Thus, the stratigraphic range of
the formation in the Southeastern Subprovince,
according to seismostratigraphic analysis, is limited
from below by the base of Kungurian Stage, and on top
by the upper Permian (Tatarian Stage). Within the
Eastern Subprovince, the evaporite formation is
placed within the folded geodynamic seismic complex
of the regional deflection of the Ural-Tien Shan folded
structure where the deformations occurred in the pre-
Triassic time.
The stratigraphic position of the evaporite formation
here is determined by the seismostratigraphic method
within the Kungurian Stage and the lower part of the
Ufimian Stage. It overlies with a gap progradational ter-
rigenous sequence of the shallow accumulative shelf.
Fig. 7. A fragment of the time seismic section demonstrating the presence of Lower Permian disharmonious formations of the
evaporite formation within the Northern Caspian in the Kurmangazy Structure. Indices in rectangles are the age of seismostrati-
graphic complexes, indices in circles are reference seismic horizons. The position of the profile is shown in the inset in Fig. 4.
1
0
NE SW
2
3
Т, s
1
0
2
3
Т, s
10 km
V
VI
J
K
-N
1
N2-Q
P2
P1
С3
T1–2
VI'
П'
1

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 43
Within the Northwestern Subprovince, the evapo-
rite formation is placed within the mid-Carboniferous
(Moscovian)–Permian seismic storey of the plate geo-
dynamic seismic complex of the ancient East Euro-
pean Platform. The evaporite formation is represented
here by a sulfate-carbonate complex of shallow shelf
deposits. It is reliably dated as Late Artinskian–Kaza-
nian. Two areas are recognized within the Northwestern
Subprovince: Buzuluk-Orenburg and Volga-Kama
regions. In the Buzuluk-Orenburg region, the evaporite
formation is represented by two lithostratigraphic com-
plexes: (a) upper sulfate-carbonate of Ufimian-Kaza-
nian age and (b) lower halogen-carbonate late-Art-
inskian-Kungurian age. In the Volga-Kama region, the
formation is more homogeneous and represented by
one sulfate-halogen-carbonate lithostratigraphic com-
plex of Kungurian-Solikamskian age. In the Central
(salt-dome) Subprovince, the evaporite formation is
considered within the Moscovian-Permian seismo-
geological storey of the geodynamic seismic complex
of the Russian and Pricaspian plates (basins). Here it
is limited by regionally consistent reference seismic
horizons “П1” and “VI” and is recognized as a sepa-
rate seismostratigraphic unit of the seismogeological
storey of the rank of seismic complex. In the Central
Subprovince, four areas are recognized: Karasal-Sol-
Iletsk, Aralsor-Khobda, Sarpinsky-Aktyubinsk and
Astrakhan-Temir regions. The evaporite formation is
here represented by halogen strata, underlain up by
deep-sea terrigenous deposits and is overlain by mid-
dle and upper Permian continental beds. The forma-
tion in the Central Subprovince, except for the Aral-
sor-Khobda region, consists of three lithostratigraphic
complexes: (a) the lower-“pre-evaporite”, terrige-
nous; (b) the middle-halite; (c) upper-halogen-sul-
fate, of chloride-potassium specialization.
In the Aralsor–Khobda region, the section of the
formation is overlain by “recycling” saline deposits
formed by the redeposition of salt in conditions similar
to the modern conditions for its accumulation in the
lakes of Elton and Baskunchak (Beenitskaya, 2020) is
extended.
A noteworthy feature of the “recycled” lithostrati-
graphic complex (studied in boreholes in the Cher-
naya Padina, Solnechnaya, Timofeevskaya, Araltyu-
besor, Mukhor, Koksozdy fields, etc.) is the interbed-
ding of salt beds with Middle and Upper-Permian red-
bedded terrigenous deposits (Pisarenko et al., 2011,
2017, 2021a, 2021b; Antipov and Volozh, 2012). In
addition to the Kungur sediments, the evaporite for-
mation includes both the Middle and Upper and
Permian series of the “recycled” salts accumulated at
the synkinematic stage due to the erosion of the Kun-
gurian deposits during the growth of the dome and
their exposure on the land surface or the bottom of the
sea (Pisarenko et al., 2021a, 2021b).
It should be emphasized that the age boundaries of
these lithofacial complexes were determined through
implementing a sedimentary model for the accumula-
tion evaporite formation based on the existing geolog-
ical and seismic information. These boundaries are to
a certain extent virtual. They display the depositional
structure of the formation at the time when it has not
yet been distorted by tectonohalokinesis (Fig. 8). This
explains the low-resolution stratigraphy (Fig. 6) of the
section of the evapoite formation of the Pricaspian
Devonian-Early Permian deep-sea basin (Central
Subprovince), at the level of the largest units of local
scales of the rank of lithostratigraphy complexes. Their
finer stratigraphy units such as suits, and even more so
of rhythmic units, cannot be achieved at the present
stage of the knowledge of the region. As indicated
above, this procedure can be performed for local
stratigraphic schemes in the best studied Northwest-
ern Subprovince and individual adjacent regions of the
Central and Eastern subprovinces (Movshovich, 1977;
Lapkin and Movshovich, 1994; Pisarenko et al., 2000;
Gogin et al., 2015).
Thus, it was stated that the borders of the salt prov-
ince of the Caspian region, especially the southern
ones, are much wider than the borders of the Pricas-
pian Devonian-Early Permian deep-sea basin and its
progradational-accumulative terrigenous shelf.
These boundaries were determined here by the
position of an dam separating the Caspian deep-sea
marginal marine basin from the Paleotethyan basins.
This dam appeared by the end of Bashkirian during
the accretion of the continental masses on the north-
ern active margin of the Paleotethys. Therefore, the
end of the Bashkirian to the beginning of the Mosco-
vian should be considered as the time of the origin of
the salt province, although the accumulation of the
evaporite formation in it began much later, and in the
same time: first of all in the southwest and last in the
southeast.
RESULTS AND DISCUSSION
The Permian evaporite formation of the salt pro-
vince of the Caspian region is a very complex object for
the stratigraphy of its section. The results of these
studies allowed us to propose technologies for the
preparation of local seismostratigraphic schemes of
saline strata exposed to tectonohalokinesis, which led
to a disruption of their primary bedding and thickness
of individual beds of the formation. According to the
Stratigraphic Code (Stratigraficheskii..., 2019), the
main valid unit of the local lithostratigraphy scale is a
formation, or, in the absence of paleontological data
supporting its age, a series. The spatial relationship of
the formations (series) and their age serve as the basis
when constructing the stratigraphic framework, deter-
mining the age range and the boundaries of the distri-
bution of lithostratigraphic units of larger ranks: series
(a set of formations) and complexes (a set of groups).
The Stratigraphic Code also states that the spatial
boundaries of high-rank units, both vertical and, no

44
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
less important, lateral, are established not directly by
their geological and geophysical mapping, but in the
course of clarifying the spatial lithostratigraphic units,
i.e., formations (series) (Stratigraphicheskii…, 2019).
The Code defines the main criteria that must be
observed in combining formations into groups, and
groups into complexes. At the same time, it should be
noted that when the lithostratigraphic complexes in
the sections of the sedimentary cover are recognized,
the requirements of the Code are not always strictly
observed. Thus, according to the Code, the reliability
of the stratigraphic framework of the local scale is
determined primarily by the validity of its main litho-
stratigraphy unit, formations (series). Only these units
are required to be valid, which presumes clarity of
manifestation of their boundary surfaces in the sec-
Fig. 8. (a) Sedimentation model (scheme) of the evaporite formation across the northern margin of the Pricaspian Devonian-
Early Permian deep-water basin (reconstruction at the end of the Kazanian time) along a profile fragment through the Pricas-
pian salt-producing province; (b) geological profile across the Pricaspian salt province. Legend: 1—halites; 2—salt-bearing
series with potassium salts; 3—saline-terrigenous deposits; 4—anhydrites; 5—sulfate-carbonate sequence, possibly with reefs;
6—limestones; 7—deposits of underwater fans; 8—deep water terrigenous-carbonate deposits; 9—clastic carbonate deposits,
products of reef destruction (deposits at the foot of reefs); 10—terrigenous marine gray deposits; 11—red salt-bearing deposits;
12—post-salt deposits; 13—boundaries: a—evaporite formation; b—seismostratigraphic subdivisions of the rank of seismogeo-
logical stages, c—lithostratigraphic subdivisions of the rank of rhythm series, d—lithostratigraphic subdivisions of the rank of
rhythmoformations, e—lithostratigraphic subdivisions of the rank of rhythmic units, f—slope erosion surface; 14—location of
the sedimentation model on the profile; 15—lithostratigraphic subdivisions of the rank of groups sorted by stages of formation
(numbers in circles): 1—pre-evaporitic; 2a—depression, accumulated before the onset of halokinesis; 2b—shelf, accumulated
before the onset of halokinesis; 2c—formed simultaneously with the process of halokinesis; 3—recycling.
0
–1.5
–3.0
а
(a)
–4.5
–6.0
0
–1.5
–3.0
–4.5
–6.0
H, kmH, km
0
–1
–2
–3
–4
–5
–6
–7
0
–1
–2
–3
–4
–5
–6
–7
km km
S N
Central Subprovince NE Subprovince
Karasal–Sol-Iletsk
Region
Aralsor–Khobda Region Buzuluk–Orenburg Region
Deep-water basin
Deep-water basin
Deep shelf
(slope terrace)
Deep shelf
(slope terrace)
Shallow-shelf
Shallow-shelf
SE NW
2c
2c
2b
2b
2b
3
3
3
2а + b
2b + а
1
1
1
1
1
P
1
u
2
-P
2
kz
1
P
1
u
P
1
k(ir
2
-u
1
)
P
1
k(f
2
-ir)
1
P
1
k(sn)
P
1
k(sn-f
1
)
C
2
b
2
-P
1
P
1
ar
2
(sg)
P
1
ar
2
(sg)
P
2
kz
1
P
2
kz
2
P
1
k(sn + f)
D
3
f
2
-C
2
b
1
C
2
m-P
1
a
1
kor
n
m
k
I
l
h
g
b
(b)
12345 6789
10 11 12 13 14 15
c
d
e
f

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 45
tion, and they must be available for mapping using
existing geological and geophysical methods. How-
ever, when compiling local stratigraphic schemes of
individual regions of the Central Subprovince (Pricas-
pian Devonian–Early Permian deep-sea basin), this
technology is not applicable. Firstly, in all modern
schemes, the disharmonic evaporite formation is con-
sidered at the rank of a lithostratigraphic complex,
although the structural features of its section partially
(a single tectonic-sedimentary cycle) correspond to
the criteria of a series, and partially (thickness, degree
and nature of its dislocation) correspond to the criteria
of a complex.
Secondly, as shown above, it is the boundaries of
large units of the scale that are directly mapped using
geological and geophysical methods, including litho-
stratigraphic complexes and their constituent elements
at the rank of series. Units at the rank of formations
can be recognized only in that part of the section of the
evaporite formation, in which its primary sedimenta-
tion bedding is preserved. Usually, this is its lower
part, composed of terrigenous or carbonate rocks with
relatively thin beds of evaporites. In Figs. 8 and 9, this
is the Upper Artinskian (Sarginian) terrigenous series,
which we recognize as the Kushumian pre-halogen
(pre-halogen stage is the time of development of an
evaporite formation, directly preceding the accumula-
tion of salt sediments) series of the evaporite forma-
tion. However, in this part of the evaporite formation,
the spatial relationships of the recognized units are not
fully established. In the overlying parts of the section
of the formation, mostly composed of halite, inside
which the originally parallel beds were later distorted
into the folds of the “laminar” flow, all the allocated
stratigraphic units of the rank of the formations
(series) are smaller, since their boundaries, both verti-
cal and, no less important, lateral, cannot be recog-
nized in the sections either by geological or geophysi-
cal methods. The above technology for constructing
Fig. 9. Seismostratigraphic subdivision of the evaporite formation of the Caspian region and correlation with regional strati-
graphic units. Legend: 1—boundaries of the evaporite formation; 2—absence of deposits associated with regional rise and erosion
of sediments; 3—absence of deposits associated with slope erosion. Letters indicate the composition of the rocks: c—carbonate,
t—terrigenous, h—halogen. The red color in the table indicates the names of the series and complexes proposed by the Geological
Institute of the Russian Academy of Sciences based on seismostratigraphic data. Numbers with letters designate lithostratigraphic
subdivisions of series rank sorted by formation stages (see Fig. 8).
International
Stratigraphic
Scale
(ICS)
The East
European
Platform
Regional Scale
General
Stratigraphic
Scale
(GSC)
System
Series
Series
Stage
Assemblage
Horizon Series Formation
Assemblage
Series Formation
Assemblage
Series Formation
Assemblage
Series Formation
Tata ri an
Permian
Guadalupian
Biarmian
Kazanian Urzhumian Severo-
dvinian
Kungurian
Cisuralian
Cisuralian
Upper
Artinskian
Ufi-
mian
Sarginian
Saraninian Filipp ovian
Irenian
Solikamskian
Sheshmian
Nemdian
Povolzhian
Urzhumian
Sukhonian
Putyatian
Karasal-Sol-Iletsk Region Aralsor–Khobda Region Sarpinsky-Aktybinsk Region Astrakhan-Temir Region
259.1
265.1 265.1
270.6
272.95
283.5 283.5
123
Reinforced
Reinforced
Reinforced Reinforced
2c (c–h) 2c (t–h)
2а + b
3
(t-h)
2c (t-ht-h) 2c (t-c)
Nevolin
Nevolin
Nevolin
2b (h)
?
?
2b (h)
(h)
2b (h)
Alatatinskaya
Kushumian
Karasal?
Kotelnikov
1(c)
1(c)
1(t-c)
1(t)
Karasal–Sol-Iletsk (P1a2-P1u1)
Sarpinsky-Aktybinsk (P1k-P1u1)
Astrakhan-Temir (P1k1-P1u1)
Aralsor Khobda (P1a2-P3t1)
Tasymian
Primugodjar
Araltyubesor
(Redbeds)
not allocated
not allocated
not allocated
North Celtmen
Irenian
Aksaray
Gorodovikovsk
Kanukovo
Volgograd
Ulagan
not
allocated
Zhitkur
Ma Ma

46
STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
ANTIPOV et al.
local stratigraphic schemes, on the basis of modeling
of the sedimentation process using the results of seis-
mic stratigraphic structure analysis, opens up the way
to solving the existing problems, due to the possibility
of directly mapping the borders of the units in these
schemes. However, in this case, it becomes necessary
to determine the criteria to define the rank of local
lithostratigraphic units, seismostrata, which were rec-
ognized during seismostratigraphic study of sections
of the evaporite formation. The analysis of strati-
graphic work shows that the standard approach to the
analysis of the evaporite formation, prescribed by the
Stratigraphic Code of Russia (Stratigraficheskii...,
2019), is applicable only in the peripheral regions of
the Caspian, where the upper part of its section is not
distorted by the processes of salt tectonics. In the cen-
tral regions of the Caspian Basin, the use of traditional
stratigraphic approaches for the stratigraphy of the
Upper Artinskian-Kungurian deposits is impossible.
To subdivide the evaporite formation of this type, a
specific approach is required with the recognition of
valid (directly mapped by seismic-structure tech-
niques) complexes and series, as well as using the ded-
icated rhythmostratigrapic units at the rank of forma-
tions and rhythmic members in the Karasal-Sol-Iletsk
region. In this work, the authors have made an attempt
to subdivide the salt-producing formation based on the
construction of a 4D model for the late Asselian-Kaza-
nian sedimentary basin of the Pricaspian region as a
whole and for the Central Subprovince (Pricaspian oil
and gas province) in particular. When constructing it,
the determining criterion for considering the selected
unit at the rank of complex is its age range, and the rank
of group is decided according to the stage of the sedi-
mentation process of the evaporite formation, during
which the section of the series was formed in each of the
selected areas (Fig. 8b). In the salt provinces similar to
the Pricaspian, which we have studied, the beginning of
the salt accumulation is preceded by the development of
a deep-sea (minus 1.5–2.0 km) of the basin, and by the
end the depression is replaced by a foothill accumula-
tive plateau (plus 0.2–0.5 km). The accumulation of
the evaporite formation underwent several stages with
the formation of sedimentary series of various compo-
sitions and age: (a) pre-evaporite stage; (b) the pre-
halokinetic stage of the accumulation of evaporites
before the start of halokinesis with two varieties of sed-
imentation, basinal and shelf; (c) halokinetic stage of
the formation of evaporites simultaneously with the
process of halokinesis; (d) recycling stage and repre-
cipitation due to the erosion of previously formed
salts simultaneous with the ongoing process of
halokinesis.
The boundaries of these stages can only be recog-
nized using seismic-stratigraphic data. The series and
complexes of the evaporite formation proposed by us,
recognized on the basis of seismic- stratigraphic infor-
mation, and their relationship with multi-rank litho-
stratigraphic units of local stratigraphic schemes, are
shown in Fig. 9.
CONCLUSIONS
(1) The local and regional stratigraphic schemes of
the Permian evaporite formation of the Caspian region
are analyzed. It is shown that the inconsistencies in the
determination of the boundaries of local lithostrati-
graphic units at the rank of member, formations and
even groups in the schemes proposed for the territory
of the Pricaspian Basin, traditionally recognized
within the boundaries of the Pricaspian Salt Dome
region, are due to objective reasons. The main reason
is the inconsistency of the observed spatio-temporal
relationships of bed associations of halogen series with
their primary sedimentation sequence.
(2) It was shown that for the Pricaspian Depres-
sion, the stratigraphic subdivision of the salt-bearing
interval of the section using methods of rhythmic
stratigraphy is impossible. The results of the usage of
seismic stratigraphic 4D models of the Caspian
region (scale 1 : 2500000) were demonstrated for
mapping the boundaries of specific units of local and
regional stratigraphic schemes of the salt-producing
provinces at the rank of complexes and groups. For
such divisions, the term “Litho-seismostratigraphic”
is proposed.
(3) A methodology for the compilation of the inter-
regional stratigraphic scheme of the salt-producing
province of the Caspian region, as well as the regional
scheme of the Central Subprovince and local schemes
for its regions, has been proposed. The proposed tech-
nique uses: (a) seismostratigraphic analysis of the inter-
nal structure of age seismostratigraphic units (seismic
strata of the tecto-sedimentation type) of the sedimen-
tary cover, which contains the Permian evaporite for-
mation; (b) reconstruction of sedimentation processes
within the salt-producing province during the forma-
tion of the Middle Carboniferous-Permian seismogeo-
logical storey, containing the evaporite formation
(4) Seismostratigraphic criteria for recognizing the
boundaries of the litho-seismostratigraphic complexes
and series of the evaporite formation and the criteria
for the zoning of the Permian salt-producing province
of the Caspian region and the recognition of subprov-
inces, and constituent regions within the latter. To rec-
ognize the boundaries of the complexes, the main cri-
terion is the disharmonious nature of the internal pat-
tern of the reflections of the seismostratigraphic
subdivision of the sedimentary cover, which contains
the Permian evaporite formation, and for recognizing
of the series, the use of the stages of the salt accumu-
lation process. The determining criterion for the zon-
ing of the salt-producing province is the morphology
of structural forms of the sedimentary cover (core of a
salt dome, salt anticline or stamp uplifts of a platform
type).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 31 No. 1 2023
STRATIGRAPHY AND SEISMOSTRATIGRAPHY 47
(5) A scheme for zoning the evaporite formation of
the salt-producing province of the Caspian region
with the recognition of the Central Subprovince and
four subprovinces on its periphery is proposed. The
Central Subprovince is recognized as a region where
deformations resulted from halokinesis, whereas the
peripheral subprovinces are characterized by manifes-
tations of tectonohalokinesis. The Northwestern and
Southeastern subprovinces are regions of manifesta-
tion of stamp extension deformations, and the Eastern
and Southwestern subprovinces are regions of folded
compression deformations.
(6) A regional scheme for subdividing the evaporite
formation of the Central Subprovince and local
schemes for four of its regions are proposed, demon-
strating the correlation of lithological-seismostrati-
graphic series with regional stratigraphic units, which
are used in the preparation of geological maps.
FUNDING
The topic of the study corresponds to the State Assign-
ment of the Geological Institute of the Russian Academy of
Sciences, the selection of materials for regional seismostrati-
graphic analysis was carried out within the framework of the
Russian Science Foundation project no. 22-27-00827.
CONFLICT OF INTEREST
The authors declare that they have no conflict of interest.
Reviewers K.B. Abilkhasimov,
I.V. Kunitsyna, and M.G. Leonov
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Translated by S. Nikolaeva