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[?] Senior scientist, Faculty of Geography, M.V.Lomonosov Moscow State
University, Moscow, Russia; Leninskie gory, 1, 1199911, Tel. +7 490
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THE FULL TITLE OF THE ARTICLECASPIAN SEA, A NATURAL LABORATORY FOR SEA-
LEVEL CHANGE



Salomon B. Kroonenberg1, Nikolai S. Kasimov, Mikhail Yu. Lychagin2

1 Delft University of Technology, Dept of Geotechnology, P.O.Box 2058,
2600GA Delft, the Netherlands; e-mail s.b.kroonenberg@tudelft.nl; 2 Faculty
of Geography, Moscow State University, Leninskie gory, 119991, Moscow,
Russia. Tel. +7 495 9394407, fax +7 495 9328836, e-mail:
lychagin@geogr.msu.ru.


Abstract

Abstracts of 100-150 words are required for all papers submitted. Each
article should be summarized in an abstract of not more that 150 words.
Avoid abbreviations, diagrams, and reference to the text. ...
The Caspian Sea, the largest inland water body on earth, shows sea-
level fluctuations at much shorter time scales than the world's oceans. It
experienced a full sea-level cycle between 1929 and 1995, with amplitude of
3 meters. Rates of the sea-level change between the 1977 lowstand and the
1995 highstand average a hundred times that of the eustatic rise. An
environmental problem in itself, Caspian sea-level change also offers
numerous exciting opportunities to science. Caspian Sea level is controlled
in the first place by its water balance, dominated by the influx of the
Volga river (80%) and other rivers, and on the outflux by evaporation at
the sea surface. It is obvious that changes in precipitation over the
basin are closely linked to global atmospheric circulation, and therefore
it may provide a yardstick for global climate change. Another opportunity
is that Caspian coasts are a physical laboratory for what might happen
along oceanic coasts as a result of sea-level rise triggered by global
warming. In this paper we discuss the sea-level changes in five different
time scales, with a special attention to possible origins in each case.

Keywords: word; another word; 3 to 6 in total, lower case except names,
position aligned with abstract, same size as abstract

Caspian Sea level, barrier coasts, river delta, Volga, Kura

1. Introduction

Section headings should be concise and numbered sequentially, using a
decimal system for subsections. All ranged left Global warming causes
world-wide concern on the impact of sea-level rise on oceanic coasts.
Predicting this impact is hampered by the slow pace of sea-level rise in
the past (17 cm in the 20th century, 2.8 mm/year in the last 15 years;
IPCC, 2007), and the complexity of coastal processes. The Caspian Sea,
having experienced phases of sea-level rise of up to a hundred times the
eustatic rate, offers accelerated real-world models of how coasts behave
under such conditions. These data can be used to calibrate and validate
existing simulation models of coastal behavior (Ignatov et al., 1993,
Kaplin & Selivanov, 1995).

2. Headings
3. Bold number

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publication [(Ignatov et al., 1993;, Kaplin & Selivanov, 1995]). References
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It is important that all raster images should be not less 300 dpi in
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Acknowledgements


This research was funded by E-NATS projects 88-432 and 89-1234

References:
1. Journal style: Abdullaev, T., Patton, J.A, Wackers, F.J, A. Akhundov,
Sandler, M.P., Gottschalk, A, Hoffere, P.B. ,(1996) A reservoir model for
the field in the Caspian Sea, Azerbaijan. Micro-computer applications, , N
4, pp.25-32.
2. Journal style: Osipova G.B., Tsvetkov D.G. (2002) The study of dynamics
of compound glaciers by space images (In Russian with English summary). //
Izv. Ross. Akad.Nauk, Ser. Geogr., ? N 3,. pp.29-38 (In Russian with
English summary).

23. Book style: Draper, N. R., and Smity, H. (1981). Applied Regression
Analysis (2nd edition). New York: John Wiley, 221 p.
4. Internet document: Author, A., Title of document [online]. Source.
Available from: URL [Accessed date Month, Year].
For other examples of reference style see
http://www.tandf.co.uk/journals/authors/style/layout/tf_2.pdf


Authors
|[pic] |Name I. LastName was born in Moscow, Russia in |
| |19__. He studied __________ at the Moscow State|
| |University, graduated in 2000 and obtained the |
| |Master's degree (Diploma). Since January 20__ |
| |he is a research assistant (senior scientist, |
| |leading scientist, Professor, etc) of the |
| |Institute of Geography RAS. The focus of his |
| |research lies on area of interest (no more 5-7 |
| |words). Main publications (no more than 3). |
|Author2 I. Lastname, received the PhD and |[pic] |
|Dr Science from ___University, Country in | |
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|Main publications (no more than 3). | |
|[pic] |Author3 I. Lastname is currently an Associate |
| |professor at University________, He received his |
| |MS degree in Cartography and Geoinformatics in |
| |19___ and his PhD in Economics in the University |
| |of __________, Country in 19__. Since Month 20__ |
| |he is Professor and head of the Institute of |
| |______ . His/Her primary research interests lie in|
| |area of interest (no more 5-7 words). |
| |Main publications (no more than 3). |



The Caspian Sea can be subdivided into three parts on the basis of its
bathymetry (Fig. 1). The Northern Caspian is essentially a very shallow
continuation of the North Caspian plain, with water depths of only a few
meters. The Middle Caspian Sea reaches 788 m depth. The shelf break between
the Northern and Middle Caspian Sea is called Mangyshlak sill. The Southern
Caspian reaches 1025 m depth and is separated from the Middle Caspian Sea
by the Apsheron sill, which forms the submarine link between the Greater
Caucasus and the Kopet Dagh mountain ranges. The Apsheron sill is the site
of intensive hydrocarbon exploration and production. Although the Caspian
Sea is the largest inland water body on the earth, it lacks some of the
characteristics of the oceans. It has virtually no tides and its salinity
is only a third of that of sea water (up to 13 g/l). The sea surface is
situated about 27 m below oceanic level (all sea-level data refer to the
oceanic datum level, in Russia represented by the Kronstadt gauge in the
Bothnian Gulf near St. Petersburg).
Caspian Sea level change is in the first place a pressing
environmental and coastal management problem in itself, especially in view
of the recent upsurge in exploration and production by oil companies. The
giant Kashagan field recently discovered in the Kazakh part of the northern
Caspian is situated at only three meters water depth, and both sea-level
rise and sea-level fall can lead to considerable environmental damage and
operational difficulties. And yet this is precisely what has happened
during the twentieth century: a three-meter sea-level fall in the thirties
to seventies, and a three-meter sea-level rise in the eighties and
nineties. Both rise and fall caused enormous environmental problems, and
even though sea level now seems to have stabilized slightly below the 1995
highstand, predicting future trends in sea level remains of utmost
importance.


Fig 1. Caspian Sea and its drainage basin

Unfortunately the causes of Caspian Sea level change are still very
poorly understood. The hydrological balance of the Caspian Sea is
controlled mainly by influx of Volga river water and evaporation at the sea
surface (Fig. 2).

Fig 2. Hydrological balance of the Caspian Sea

Both in turn are controlled by global and regional atmospheric circulation
patterns, and therefore a correlation between global climate change and
Caspian Sea level is logical, but by no means firmly established until now.
However, sea-level cycles come in at least five different time scales, from
tidal, seasonal, decadal, centennial/millennial to glacial/interglacial,
and in amplitudes ranging from 3 cm to at least 150 m, and it is in most
cases unclear what processes are responsible for specific cycles.
The main problem in prediction is the lack of accurate sea-level data
from the past, reason why we started a UNESCO- IGCP project Dating Caspian
Sea Level Change (2003-2007; www.caspiansealevelchange.org), which
consisted in international meetings in almost all Caspian countries. In
several projects with partners from most Caspian countries, funded by NWO,
RFFI, EU and industry we have improved the data base of past sea-level
change in the Volga and Kura deltas, both onshore and offshore, and in
barrier-lagoon complexes along the whole western shore of the Caspian. We
have now reconstructed the first new Holocene Caspian sea-level curve since
30 years, based on shallow seismics, sedimentology, biostratigraphy and AMS
14C datings. The highstands demonstrated at 2600 BP and in the Little Ice
age corroborate that Caspian Sea level is at least in part controlled by
global processes, and not only regional ones.
In this paper we will discuss how sea-level changes in five different
time scales, and we will discuss possible origins in each case.


1. Seasonal changes
Caspian sea level is monitored continuously, that is, every ten days, by
the Topex-Poseidon radar satellite and its successor Jason, with an
accuracy of 4 cm (Cazenave et al., 1997). This allows to see the importance
of seasonal changes in the order of magnitude of 40 cm, related to spring
snow melt in the Volga drainage basin (Fig. 3). Because of dam construction
the peak discharge of the Volga and Kura rivers is slightly earlier than
under natural conditions (Moskalenko and Rusakov, 1979).


Figure 3. Satellite measurements of Caspian Sea level since 1993
(http://www.pecad.fas.usda.gov)

2. Decadal sea-level changes
Caspian sea-level fluctuations obtained world-wide attention when sea-
level fell by over 3 m between 1929 and 1977 and rose again by 3 m until
1995, when it started falling again (Cazenave et al., 1997) (Fig. 4). The
rate of sea-level rise averaged 150 mm/year during the 1977-1995
transgression, and had a maximum of 340 mm in 1991. In this way one year of
Caspian sea-level rise equaled a century of eustatic sea-level rise in the
oceans. This causes rapid facies shifts along the Caspian shores.
The cause of rapid Caspian sea-level changes is much debated, but
most probably related to the fact that the Volga River which supplies 80%
of the inflow of the Caspian Sea, has experienced strong variations in
annual discharge (Rodionov, 1994). The sea-level cycle in this century
probably reflects secular variations in precipitation in the Volga drainage
basin, which themselves are related to systematic deviations in the jet-
stream-related circulation patterns (Rodionov, 1994).
The strength of the depression activity in NW Europe has recently been
shown to be strongly dependent upon variations in the North Atlantic
Oscillation (NAO) (Hurrell, 1995). The curve depicting the variations in
strength of the NAO matches the historic Caspian Sea level change in this
century remarkably well, and Arpe et al. (2000) show that there is a fair
match between Caspian Sea level and the larger-scale oscillations in the El
NiЯo-Southern Oscillation phenomenon in the southern hemisphere (cf Arpe &
Leroy, 2007). Since it is essentially a precipitation signal, not a
temperature signal, it is unclear to what extent this is directly related
to global warming.


Fig 4. Caspian Sea level change in the 20th century (Kroonenberg et al.,
2000)

The way in which Caspian coasts react to sea-level rise is strongly
dependent upon initial submarine slope (Fig. 5; Ignatov et al., 1993;
Kaplin & Selivanov, 1995). Slopes with gentle gradients (<0.03() show
passive drowning, as waves are dissipated long before they reach the coast.
Slopes between 0.03( and 0.3( show formation of barriers and lagoons. Along
steeper profiles between 0.3( and 0.8( barriers are formed directly on
shore, and only coasts with still steeper gradients develop abrasion cliffs
which move shorewards upon further sea-level rise.

Fig 5. Impact of sea-level rise on coasts of varying gradient (Kaplin &
Selivanov, 1995).

2.1. Barrier lagoon coast
The Faculty of Geography of Moscow State University has monitored
these changes at the Turali coast in the Central Dagestan almost annually
since 1974 in the framework of students practicals (Kasimov et al., 2000;
Kroonenberg et al., 2000).


Fig 6. Impact of sea-level fall and sea-level rise on Turali barrier-
lagoon coast, Dagestan (after Kroonenberg et al., 2000, 2007)


Between 1880 and 1929 the level of the Caspian Sea was almost constant at
-25 m to -26 m (Fig. 4). When sea level started to drop sharply in the
thirties, the coastline moved seawards, resulting in abandonment of the
cliff and the formation of the present-day coastal strip, widening up to
750 m by 1977, averaging about 15 m/y coastal advance during sea-level
fall. Superimposed upon this general trend, small-scale single-storm bars
were formed during minor retreats of the coast occurred in 1929, 1941, 1956
and 1963. No lagoons were formed during sea-level fall according to
monitoring data and aerial photographs from that period. Seaward-dipping
clinoforms have been found in outcrops in the Turali area in Dagestan and
in Ground Penetrating Radar (GPR) profiles of a similar strandflat along
barrier-lagoon coasts in Azerbaijan (Storms and Kroonenberg, 2007).
As sharply as sea level dropped in the thirties, it rose after 1977.
The impact of sea-level rise has been documented in much more detail than
that of sea-level fall. As soon as sea level started to rise, a barrier of
about 0.6-1.0 m in height was formed, separated from the coast by a lagoon.
It shows prominent washover lobes over its entire length, which intrude
into the lagoon. During sea-level rise lagoonal deposits became overridden
by the retrograding barrier, and eroded remnants of lagoonal deposits have
been found in the upper shoreface. The measurements of the morphology of
the barrier indicate that during rising sea level the entire barrier-lagoon
system encroached landward at an average annual rate of 18 m/y.
After the 1995 highstand sea-level started to fall from July 1995 onward
at a rate of 24.8 (1.4 cm/y (Cazenave et al, 1997). The Turali barrier
broadened, and the lagoon became narrower and shallower. Along the southern
tip of Tyulen' island in the middle of the Caspian Sea a number of
strandlines with miniature bars (0.1-0.2 m high) with washover micro-lobes
have been found seaward of the 1995 highstand barrier (Kroonenberg et al.,
2000). These might be correlated with annual or biannual storms and
seasonal changes in Caspian Sea level during overall regression. A similar
development was seen in GPR profiles of the recent barrier along different
parts of the Azerbaijan coast (Storms and Kroonenberg, 2007).
The Caspian Sea level fluctuations essentially influence a diversity of
the coastal zone environment. Along accumulative shores the sea
transgression gives rise to geomorphological, liythological, soil, biotic,
as well as geochemical diversity of the coastal landscapes. This is caused
by inundation and water-logging processes, with a corresponding rise of the
groundwater table, and also simultaneous vigorous vegetation development of
vegetation in newly-formed hydromorphic and semi-hydromorphic areas (salt
marshes). On the contrary, the sea regression leads mainly to the passive
emergence drowning of the shore zone with a following decrease of the
coastal environment variability.
Geochemical conditions of the coastal landscapes are also undergone
changes due to the sea-level fluctuations. The rRegressive stage is
associateds with a low variability of geochemical environments in sediments
and soils. The latter are characterized mainly by alkaline oxic conditions,
and salinization as a leading geochemical process. Geochemical diversity
of the coastal zone during a transgressive stage is much higher. Conditions
vary from neutral to highly-alkaline, and from oxic to highly aunoxic.
Newly-formed geochemical processes are presented by sulfidization,
gleyzation, ferrugination, organic matter accumulation, and salinization.
They cause a formation of various contrasted geochemical barriers in soils
and sediments with a consequent redistribution of chemical elements.
Formation of barrier-lagoon systems due to the sea-level rise is quite
typical for accumulative shores in different areas of the world. Thus, the
evolution of the Caspian coasts under the sea-level changes serves as a
natural model that can be used for understanding the general features of
development of the world ocean coasts. Our local study of geochemical
changes of the Caspian salt marshes describes the regional environmental
changes of the coastal zone.

2.2. Volga delta
The Volga delta serves as an example to study the impact of sea-level
change on gently sloping coasts, where waves are dissipated before they can
reach the coast. The Volga delta is one of the largest deltas in the world,
and distinguishes itself from others by its extremely gentle gradient and
by the impact of much more rapid sea-level fluctuations than at those along
oceanic coasts (Kroonenberg et al., 1997).
Morphological changes in the lower delta plain in the past 150 years
have been monitored in detail in the Damchik part of the Astrakhan
Biosphere reserve in the western part of the lower delta plain (Fig. 7).
The nature reserve was established in 1919 and is largely untouched by man
since then. Detailed maps are available since 1853, and aerial photographs
since 1935. The older history has been carefully reconstructed in numerous
classic papers by E.F. Belevich (e.g. Belevich, 1956, see references in
Kroonenberg et al., 1997). Our team has studied in detail the changes that
occurred during the last 1929-1995 sea-level cycle using maps, aerial
photographs and satellite imagery (Baldina et al., 1995, 1999; Kasimov et
al., 1995; Labutina et al., 1995, Kroonenberg et al., 1997, Overeem et al.,
2003).
Older maps show that the whole area depicted on Figure 7 was still open
water in 1853, and that a large part of this channel network formed as a
result of a previous phase of delta progradation between 1909 and 1927,
during a shortlived regression of the Caspian Sea (Belevich, 1956). The
lake between the two main distributaries Koklyuy in the West and Bystraya
in the East, started to form as an interdistributary bay, but was already
almost isolated in 1935. The 1935 map shows a rapidly bifurcating and
anastomosing network of channels which flowed into the sea near the
Damchik research station. Sea-level had already started to fall in 1929,
but its main effects are only visible in the next stage. In 1951, the
delta had rapidly prograded across the shallow sea floor for over 15 km.
Large parts of the shallow sea bottom emerged passively. Sea-level dropped
further until 1977, at a lower pace than in the thirties, however. The
delta distributaries advanced another 500 m. Rapid sea-level fall leads to
rapid progradation with fine sandy mouthbars, turning into levees, leaving
behind marshy areas (kultuky). Due to the extremely gentle gradient
(5cm/km), delta distributaries bifurcate rapidly, leading to a very dense
network of small outlets near the delta front, and hence to a great number
of small-sized coarsening upwards cycles <1m in thickness with little
lateral continuity. Further upstream, channels either are silted up or
coalesce into larger ones. In a modern muddy channel fill in Kolbin Creek,
which originated during the progradational phase between 1909 and 1927 and
started to loose its function during progradation in the thirties,
sedimentation rates up to 2 cm/y (uncompacted) have been measured using
137Cs dating (Winkels et al., 1998).


Figure 7. Progradation during sea-level fall, aggradation during sea level
rise in the Volga delta (after Baldina et al., 1999, Overeem et al., 2003)

Since 1978 sea level started to rise, and in the 1981 images the delta
contours are largely consolidated. While sea level had risen for another
meter in 1989, the contours of the delta front surprisingly hardly changed.
This is because growth of reed in interdistributary bays and willows on
levees could keep pace with sea-level rise (Baldina et al., 1999, Overeem
et al., 2003). Sedimentation continued, but most of the sediment was caught
in the levees and basins behind the levees. No progradation occurred, but
also no retrogradation: vertical aggradation predominated during sea-level
rise.
Field observations in 2000 show that as a result of the sea-level
fall after 1995, progradation started again. New fine sandy levees are
again being formed at the outlets, 1-2 m wide, and not more than 1.50 m
thick.

Fig. 8. Volga delta subdivision (Kroonenberg et al., 1997)

Environmental geochemical study of the area revealed few poor changes in
aquatic systems of the Volga delta during the sea level rise. Essential
changes were found within the near-shore zone, so-called avandelta (Fig.
8). This vast shallow-water area is a specific feature of the Volga delta.
Fresh river waters in the avandelta continue on their way to long
distances, hence fresh/salt water mixing zone is displaced for dozens of
kilometers towards the sea. Sea level rise caused a shift of this zone for
20-30 km to the north. Due to it some islands of the southern part of the
avandelta (e.g. Chistaya Banka) underwent an influence of water of the
mixing zone with increased salinity and higher alkalinity.
Water depths in the avandelta reached 2 m, which is the limit for the reed
growth. Increasing influence of marine water coupled with a large amount of
drowned organic material caused a sulfidization process in sediments of
flooded islands. As a result, distinct accumulation of trace elements,
especially Mo and Cd, at the sulfide geochemical barrier was found there.
This fact is useful for the reconstruction of paleoenvironments. Layers
in deltaic Holocene sediments enriched with fine particles, organic matter
and heavy metals can indicate transgressive stages of the sea-level
fluctuations. Similar properties were found for lagoon sediments of barrier
coasts, which are also characteristic for periods of the sea-level rise.

3. Centennial to millennial sea-level change
Centennial and millennial sea-level changes are much more difficult to
reconstruct, as instrumental observations do not go further back than 1834.
There exists an enormous amount of historical data from old maps and travel
accounts, which unfortunately contradict each other often (Varushchenko et
al., 1987). Also the geological evidence is contradictory. Not all
depositional environments are equally suitable for determining past sea
levels. Cores from the bottom of the Caspian give a continuous record of
paleoecological conditions but only very crude data on paleobathymetry
(Boomer et al., 2005, Leroy et al., 2007). Marine terraces and paleo-
coastlines may give accurate positions of former sea levels provided
tectonics are taken into account (Rychagov, 1977, 1997), but often only
reflect highstands and provide very short and incomplete stratigraphical
records and age data (Kroonenberg et al., 2007). Lowstands are
still more difficult to date, and require extensive marine geophysical
survey and drilling (Hoogendoorn et al., 2005).
We have reconstructed a new Holocene sea-level curve with modern dating
methods, and using our understanding the dynamics of the coasts during the
last decadal sea-level cycle to establish the best sites for sampling
reconstructing Caspian sea-level history of the Holocene, including the
Dagestan barrier-lagoon coast, the Volga delta, and the Kura delta in
Azerbaijan.

3.1.Barrier-lagoon coast
Barrier-lagoon coasts are especially suitable to establish the age
of former highstands by dating the highest overridden lagoonal deposits
(Fig 6). Large parts of the Turali coastal plain in Dagestan are
situated between -20 m and -25 m and consist of a series of Novocaspian
(Holocene) gravel and sand barriers, totaling up to 3 km in width in the
north and tapering out southwards towards Cape Bakay-Kichklik. The barriers
are partly overlain by eolian sands. The barriers consist of sand and
gravel transported northwards along the coast from the Manas River mouth in
the south. At least five eastwards progradational phases have been
recognized in the aerial photographs and in the field, all with a SSE-NNW
orientation slightly oblique to the present coast, and with a spit turning
southwestwards at their northern extremity (Fig. 9). Their top is situated
at -21.5 m. A sixth phase, reaching to the -23.5 datum level, is strictly
parallel to the present coast, cuts off the southern ends of the previous
five phases and closed the bay off from the sea, thus creating the present-
day Lake Bol'shoy Turali. The modern coastal terrace started to form from
1929 onward at around -26 m. The pre-1929 coastline is generally taken as
the position of the scarp eroded into the Novocaspian barrier sequence.

Figure 9. Holocene barrier complex, Turali area

One of the first sea-level curves of the Caspian Sea was obtained
thirty years ago by Rychagov (1977, 1997) mainly from sections in this
barrier complex (Fig. 10). Rychagov's curve is based on numerous 14C
datings obtained on mollusks from barrier deposits and incised valleys in
the area. At that time this was the best curve based on geomorphological,
sedimentological and chronological data alone, without modeling.

Figure 10. Caspian Sea level curve after G.I.Rychagov (1977, 1997)

We returned to Turali barrier complex to obtain new data with adequate
sampling and dating techniques. In 2001, the outcrops along the Turali-
Sulfat canal were no
longer visible, and therefore, we made two ground penetrating radar (GPR)
profiles, 1465 m and 1080 m long across the complex, perpendicular to the
coastline, and we identified overridden lagoonal deposits in them under
highstand barriers characterized by the transition between landward-dipping
reflectors (washover lobes), and seaward-dipping reflectors (start of new
regression, Fig. 6). We obtained a very consistent set of AMS 14C data from
doublevalved mollusks (mainly Didacna spp. and Cerastoderma glaucum)
sampled in situ in vertical (living) position from clayey lagoonal
deposits. These data showed that the five first phases of barrier formation
took place between 2700 and 2300 BP. This is a very well known of globally
humid climate, the onset of the Subatlantic period, documented in Holocene
deposits throughout Europe (Van Geel & Renssen, 1998, and also in the Volga
drainage basin (GrachКva et al., 2002). The last, slightly crosscutting
barrier phase parallel to the present-day coast was deposited a few
centuries ago, coinciding probably with the Little Ice Age. The two
highstand phases are separated by a paleosol which probably reflects the
Derbent Regression in the Warm Mediaeval Period (Kroonenberg et al., 2007).


3.2. Kura delta
More data on the age of the intervening lowstand were obtained from an
extensive geophysical, drilling, paleoecological and dating study in the
onshore and offshore Kura delta (Hoogendoorn et al., 2005). In contrast to
the Volga delta, the Kura delta is a mixed fluvial-wave-dominated, steep-
gradient delta which projects into the deep South Caspian Basin. Sparker
profiles show an erosional unconformity at about 21 m below the present
water surface (-48 m below oceanic level), underlain by deltaic deposits
with shelly intervals at 16-17 m depth AMS 14C dated around 1400 BP (Fig.
11). At a sedimentation rate of 1.2 cm/year calculated from the core, the
erosional unconformity represents an age around 900 BP. Mollusk fauna
indicates depositional depths between 10 and 20 m below sea level (i.e. 34
and 44 m below oceanic level). Although a few of these mollusks might not
be in situ, the 14C data are consistent enough to position this lowstand
between the 2600 BP and the ~300 BP highstand, the more so as also from
historical data lowstands are reported both from the 6th and the 12th
century AD (Hoogendoorn et al., 2005).


Fig 11. Schematic alongstream cross-profile through Kura delta, Azerbaijan
(after Hoogendoorn et al., 2005).

3.3. Volga delta
The most suitable sedimentary environments that provide both information on
the position of past coastlines and sufficiently continuous and datable
stratigraphic sections are the river deltas.


Fig 12. Stratigraphic complexity of Holocene Volga delta deposits as
recorded and interpreted from Parametric Echosounder data (Hoogendoorn et
al., in prep).


We carried out a first drilling campaign in the Damchik area of the
Volga delta in 1995, with 80 augerings up to 10 m deep in the present-day
coastal zone; the results showed a very varied small-scale pattern of
sedimentation, which was difficult to correlate with each other, and
resembled the present-day small-scale sedimentation pattern of the Volga
delta (Overeem et al., 2003). Preliminary 14C data from scattered drill
holes allowed to estimate a sedimentation rate of 1.3 mm/year in the period
between 1000 and 6000 BP (Overeem et al., 2003).
In order to resolve the stratigraphic complexity of sedimentation, we
carried out a geophysical survey using the їInnomar Parametric Echosounder
along the main channels of the Damchik area (Fig. 12), which confirmed the
small-scale heterogeneity of the sedimentation pattern. This was combined
with 28 augerings until 10 m depth, which were studied in great detail for
granulometry, pollen, geochemistry, malacofauna, and dated using AMS 14C
techniques on mostly in-situ mollusks (Hoogendoorn et al., in prep.). Part
of these data are still being elaborated, but from the datings obtained so
far a very consistent pattern of sea-level change emerges, when combined
with the data from the Dagestan barrier coast and the Kura delta. Together
these data enabled us to establish a new Holocene sea-level curve of the
Caspian, based solely on modern AMS14C data from mostly in situ mollusks
(Fig. 13).

Fig 13. New Holocene Caspian Sea level curve based on new AMS 14C data from
the Volga and Kura deltas and the Turali, Dagestan barrier coast.

The oldest AMS 14C data from several drillings in the Volga delta suggest a
lowstand around 8000 BP, in harmony with data from Rychagov (1997) obtained
by conventional methods. No new age data are available from the period 8000-
5000 BP. Volga delta data suggest a continuously rising sea level between
5000 and 3000 BP until a highstand is reached at -25 m around 2600 BP, as
documented in the Dagestan barrier coast. The historically well-known
mediaeval Derbent regression (Rychagov, 1997) down to -34 m, and possibly
even -45 m, is recorded in the deeper parts of the offshore Kura delta in
Azerbaijan, and a second highstand around 300 BP is documented in the
outermost barrier in Dagestan. The two highstands appear to coincide with
two well-known periods of increased precipitation in Eurasia, the 2600 BP
event (Van Geel and Renssen, 1998) and the Little Ice Age, whereas the
Derbent regression seems coeval with the Warm Mediaeval Period. This
corroborates the hypothesis that Caspian Sea Level is ultimately regulated
by global climate change, possible as a result of variations in solar
activity (Kroonenberg et al., 2007).

4. Glacial-interglacial sea-level change
While the amplitude of Holocene sea-level oscillations was between -21 and
-48 at most, fluctuations of much higher amplitudes must have taken place
in the Pleistocene. During the Last Glacial, a highstand of at least +50 m
was reached, during which the whole Pricaspian Plain was flooded, the Volga
formed an estuary far upstream beyond Volgograd, and the Caspian overflowed
towards the Black Sea through the Kuma-Manysh sill. As the Black Sea and
the world oceans experienced a lowstand at that time, this must have been
an event of considerable impact. However, the age, causes and global
significance of these events, collectively called the Early Khvalyn
Transgression, are hotly debated until the present day.
It was followed by a deep regression, the Mangyshlak regression,
probably early Holocene, during which a lowstand of - 80 m or even - 113 m
was reached (Varushchenko et al., 1987), and during which a prominent field
of E-W oriented latitudinal dunes was formed at the spot of the present
Volga delta, the so called Baer Hills. The origin of these hills is equally
strongly disputed.
There are three different opinions on the age of the Early Khvalyn
Transgression, or better Early Khvalyn Highstand. Rychagov (1977, 1997)
considers the transgression of early Glacial age, around 70 000 BP, on the
basis of dated highstand terraces in Dagestan. There is some support for
this viewpoint from recent research by Mangerud et al (2001). These authors
reinvestigated an older theory by Grosswald (1980) that glacial highstands
in the Caspian are related to the overflow of proglacial lakes in the
Russian and Siberian Arctic, caused by the ponding of north-flowing rivers
by the Barentsz and Kara ice sheets. According to the Norwegian data,
especially OSL dated highstands from proglacial lakes, there was an Early
Glacial highstand around 90 000 BP, which caused Siberian rivers like Ob
and Yenissey to reverse their drainage towards the south, and passing
through the Turgay pass in Kazakhstan, the Aral Sea and the Caspian towards
the Black Sea (Mangerud et al., 2001). A minor Late Glacial highstand was
also caused by ponding of north-flowing rivers, but only in Russia, notably
the Dvina and the Vychegda-Pechora, which overflowed towards the Volga
river, not the abovementioned Siberian rivers (Magerud et al., 2001). The
Late Khvalyn Caspian highstand, which reached only the 0 m datum level, was
probably caused by this proglacial ponding event.
According to other authors, notably Chepalyga (2007) and Svitoch (2007)
the overflow towards the Black Sea occurred only in the Late Glacial around
15 000 BP, thus adding to the controversy of the sudden Early Holocene
flooding of the Black Sea. Panin et al (2007) argue, that no proglacial
lakes and ponding of north-flowing rivers are necessary to explain such
highstands, as the channel width and the size of meander loops of the main
rivers flowing in southern Russia indicate at least five times higher
discharges in the Late Glacial than at present.
At least two earlier major but poorly dated Pleistocene transgressions
have been distinguished on the basis of biostratigraphic data on uplifted
marine terraces along the western Caspian coast, and outcrops along the
Lower Volga: the Khazar Transgression around 200 000 BP, and the Baku
(>400 000 BP) transgressions, each subdivided into minor phases (Rychagov,
1977, 1997; Svitoch, 1991; Svitoch and Yanina, 1997; Kroonenberg et al.,
1997).
Lowstands are still more difficult to date. As soon as sea level falls
beyond the -34 m datum level, the northern Caspian emerges, and the Volga
and other rivers from northern provenance cut deep incised valleys into the
Pricaspian Plain, each time along different thalwegs. This must even have
happened during the Warm Mediaeval Period lowstand (Derbent Regression),
and the more so in earlier and deeper lowstands such as the Mangyshlak
Regression. The incised valleys usually were filled during the next
transgression. Most deposition by the Volga river during lowstands took
place beyond the Mangyshlak Sill shelf break in the northern part of the
Middle Caspian. Two major lowstand wedges up to 300 m thick showing
clinoforms have been observed along the northern shelf of the Middle
Caspian between the -50 and -200 m isobaths by seismic profiling (Fig. 14).
They have been attributed to deep regressions between the Khazar and
Khvalyn highstands and between the Lower and Upper Khvalyn highstands,
respectively (Lokhin and Maev, 1990, Levchenko et al, 2007). More data from
recent drilling are forthcoming.

Fig 14. Seismic profile of Volga lowstand delta in the Middle Caspian,
after Levchenko et al., 2007.

5. The Pliocene South Caspian Basin and the PaleoVolga delta

The Caspian Sea has been a closed basin since the connection with the
Black Sea was severed about 6 Ma ago as a result of the uplift of the
Caucasus. Shortly after, the Caspian Sea experienced the most dramatic
lowstand of its history. The South Caspian Basin subsided rapidly from
that time onwards, due both to thrusting of the Iranian Alborz Mountain
over the oceanic bottom of the South Caspian Basin, as well as incipient
subduction of the South Caspian Basin under the Apsheron sill, the
connection between the Caucasus and the Kopet Dag. In this way a basin
almost 10 km deep was formed, which caused the forming of a huge incised
valley of over 500 m deep and over 2000 km long, reaching possibly as far
north as Moscow. The Middle and Northern Caspian did not yet exist at that
time, and the Volga River reached the Caspian sea only near the present
site of Baku in Azerbaijan, 1200 km further south than at present. Between
5.5 and 3.4 Ma ago the Paleo-Volga deposited the so-called Productive
Series, a 6-8 km thick Pliocene succession of deltaic deposits of a Paleo-
Volga between 5.5 and 3.4 Ma, which is the major reservoir unit for oil and
gas in the South Caspian Basin, (Abdullaev et al., 1998, Hinds et al.,
2004, Kroonenberg et al., 2005). As these deposits lack evaporites and have
been deposited in shallow water, they are not the result of desiccation of
a body of oceanic water, as in the roughly coeval Messinian event, but
probably closely related to tectonic subsidence.

Conclusions
The five different time-scales of Caspian Sea level change each have
their own origin: the seasonal ones in the annual period of snow melting,
the decadal changes probably in some internal oscillation of the climate
system such as El NiЯo-Southern Oscillation or the North Atlantic
Oscillation. Larger-scale oscillations as seen during the Holocene seem to
follow global millennial periods of cooling and warming, notably the 2600
BP and Little Ice Age colder and wetter periods, which have been argued to
be related to periods of weaker solar activity. Glacial-Interglacial
oscillations may either be due to specific paleogeographic conditions such
as overflow from proglacial lakes, or to important precipitation and
discharge variations, or a combination of both. At last the dramatic
lowstand in the South Caspian in the Pliocene seems largely due to specific
tectonic conditions.
All this means that predicting Caspian Sea level requires understanding
of all those different processes, and cannot proceed from studying the
instrumental record only. In that sense the Caspian is indeed a laboratory
for sea-level rise, as predicted by Prof. P.A. Kaplin (Kaplin & Selivanov,
1995).
Acknowledgements

This research was funded by EU-INTAS projects 94-3382 and 99-139, NWO
projects 047.003.010.00.95", and 047.011.000.0 and 047.017.007, , RFBR 07-
05-00752, 06-05-08097, 05-05-66863, 05-05-89001, and BP.

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