International Journal of Marine Science, 2017, Vol.7, No.3, 19-30
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2.3 Historical geology of the Caspian Sea fluctuation
The Caspian Sea is remnant basin of large parathetis ocean. Paleontology records show that the Caspian Sea was
born as evaporate basin in late Miocene, Messinian stage (7 million years ago) (Mamedov, 1997). The
Mediterranean Sea was separated from Atlantic Ocean by tectonic movements at the same time. And submerged
beach had been dominated during this period. This process happened in the east of parathetis basin and Caspian,
Aral, Black and Azov Sea had no connection together. In fact, this natural events had caused uplifting, folding and
basin separation and huge evaporate sediment such as: gypsum and salts had been deposited on the floor
(Khoshravan, 2014). At the same time the vast parts of internal lakes of Iranian platform had been submerged and
red iron oxide sediments deposited. But in the early Pleistocene (5 million years ago) frequent raining had caused
harsh flooding and rock erosion promoting, then the fresh water lake appeared and productive conglomerate had
been deposited (Chelken formation). Then the depth of Caspian basin increased and marine environment had
reformed and several mollusks with carbonated sediment made Agchagilian formation in middle to late Pliocene.
In the early Pleistocene, Apsheron sandstone with brackish water mollusks fossil had been deposited in the
Caspian Sea basin (Khoshravan, 2014). Therefore, there was a full sedimentary cycle along the Pliocene and
Pleistocene with apparently thickness 15 Km. Caspian Sea southern basin had been subsided with velocity rate
about 44 mm/year along 5.5 million years’ period (Kakroodi et al., 2012). In the late Pleistocene the Caspian Sea
level was increased more than 50 meters and it have been continuing for 1000 years and the Caspian Sea has
connected to Black sea through Manych-Kretch waterway (Leroy et al., 2014). At that time mollusks of Caspian
entered to eastern part of Black sea. Then sea level of Caspian Sea with unprecedented speed decreased and iron
oxide and Gypsum had been deposited in Mangheshlagh regression (Leroy et al., 2014). In the early Holocene
(10000 years ago), Caspian Sea level had increased and it reached to -22 meter below ocean level (Kroonenberg et
al., 2000; Leroy et al., 2014). At that time the salinity of southern coast of the Caspian Sea is less than middle part
and it associated to eastern rivers input (Mayewski et al., 2004). Palynological records show that the sea level of
Caspian Sea had been standing at the high level and Uzboy river run off had contributed to Caspian transgression
(Leroy et al., 2014). In the beginning of early Holocene there were several huge ice sheet on Himalaya mountains
and the ice melting created the high volume run off toward the Caspian Sea (Leroy et al., 2013). This process had
been happened while the weather was warmer in northern part of Caspian Sea and the amount of northern run off
was little. And salinity inversion had occurred toward south basin of the Caspian Sea. Uzboy River received its
water from Sarykamish lake and Amoudarya lake and they were depended in Tin shine mountains ice melting
(Leroy et al., 2013). Antropogenic impact on Uzboy River during 13 centuries and the first of 20 century caused
Caspian Sea hydrological cycle balance disrupted. The derbent regression phase in 1500 years ago is so important.
At that time the Caspian Sea level reached to -32 meters (Leroy et al., 2013). Then the transgression phase of the
Caspian Sea had occurred in 700 years ago during little ice age and the level of Caspian Sea reached to -22 meters
(Leroy et al., 2014). Paleogeography and morphology records approved that the Caspian Sea has alternatively
fluctuation since early Holocene (Rychagov, 1997). On the basis of gaining results in the study of marine terraces
in Daghestan, five transgression phase has been distinguished which belong to 8000, 7000, 6000, 3000, and 200
years ago (Hoogendoorn et al., 2005). Three sedimentary terraces have been determined in Iranian beach zone
with age 2500, 900 and 500 years ago which those are located in -22, -24 and -25 meters below mean global sea
level (Kakroodi et al., 2012). So the highest level of Caspian Sea during the Holocene is -22 meters and lowest
level is -32 meters (Kroonenberg et al., 2000). There is precisely corresponding between Caspian Sea level
changing and Urmia Lake during Holocene epoch (Khoshravan, 2015). There were three regression phase in
Urmia lake like Caspian Sea in 12000, 4000 and 1200 years ago (Khoshravan, 2015). Geological clues show the
periodic phase of Caspian Sea fluctuation have been happening with duration 400 years (Mamedov, 1997) (Figure
7). On the basis of this theory, we are expected the recent regression phase of Caspian Sea that began from 1900
years will be continuing by 2100 years. But the last transgression phase of the Caspian Sea during 1977-1995
years, ratified all this forecasting.
The historical geology of the Caspian Sea indicates that tectonic movements has separated parathetis basins from
each other during late Miocene and climatologic impact during last glacial phases have caused periodic fluctuation
of the Caspian Sea. The limitation of Caspian Sea watershed area has caused this basin hydrologically depend on
