Applicatopn dossier for nomination as a European Geopark ...

they are expressed by clay - siltstone thickness, on the
separate areas with prolayers of marl.
Turonian and conjac stages. Adjournments of these
stages have universal development. They are
deposited with washout on spreading cenomanian
formations and lithologically they are expressed by
white, strong pelitomorphic and organogenic -
pyroclastic limestones.
Santonian stage. Santonian adjournments have a wide
circulation. The bottom sublevel is combined by
limestones of light grey colour, sometimes with a
greenish shade, fractured. In the west of the examined
area prolayers of marls and clays are traced. In the
basis of the cut the conglomerate submitted by a
pebble of phosphorites, consolidated with caebonate
cement is deposited.
Early santonian sublevel is submitted by silica clays of
grey and dark grey colours, layered, with interlensing of
siltstone. In the roof of the cut following limestones are
deposited: dark grey, carbonate, with prolayers of
aleurolites.
Campania stage. Campanian formations have universal
distribution and deposited with washout on spreading
adjournment. The bottom sublevel is expressed by
limestones of grey, greenish-grey, clay, pelitomorphic,
with prolayers one-colour marls.
Early Campanian sublevel is submitted by clays of dark
grey colour, calcareous, aleurite, with prolayers of
marls and limestones.
Cainozoic erathem
Quaternary system
Quaternary adjournments are submitted by alternation
of layers of sand and clays with prevalence in the cut of
the last ones and subdivided into Khvalynian and
modern adjournments.
The list of rocks
1. Anhydrite
2. Argillite
3. Table salt
4. Aleurolite
5. Clay
6. Limestone
7. Sandstone quartz
8. Marl
9. Gypsum
B. 4 Geomorphological features
The area of Bogdo and Baskunchack occupies the
special position in geological structure. It is located in
the northeast part of the Northwest PriCaspian in
vicinities of the lake Baskunchack and mountain
Bolshoye Bogdo. The special feature of a geological
structure is the presence near to a day time surface of
gypsums of Kungurian stage that is caused by the
display of hydrochloric tectogenesis. It has defined here
the wide development of leaching processes and, as a
result, specific forms of relief (craters, hollows, caves
and others). Authors paid special attention to studying
of these relief forms.
In the tectonic relation the territory represents
Баскунчакский hydrochloric massive experiencing a
11
modern rising, and mould, filled with the lake
Baskunchack. In one of exposures of Ubo hill
(vicinities of the settlement Nizchny Baskunchack a
layer of early Khvalynian clay with deformation up to
1-1,5m ) is traced. For the last 15-20 thousand years
the section has been uplifted with a speed of up to
0,04-0,06mm per year that testifies the high tectonic
activity in platform conditions.
Structural features, history of geological development
and climate have defined geomorphological structure
of researched area. There is a unique presence in
the Northwest PriCaspian of denudation plains with
the absolute mark of 149,6m. The denudation plain
refers to a hydrochloric massive and smoothly
passes to accumulative plain, which outlines the lake
Baskunchack. The mould is occupied with the lake
and earlier it was considered as compensatory one.
But during the last decade in connection with the
active extraction of salt, the mould bowing is not
compensated by salt accumulating. Therefore a
surface of salt in the center of lake caves in about a
minus of 21,2 m. in 90th of XX century up to a minus
of 22 m in 2004.
The peneplain occupies a significant part of territory
the around the lake. Absolute marks of it go down
from periphery in the direction of lake from 149,6m.
Prevailing modern relief forming processes are
fluvial, karstic and processes of physical aeration.
As a result of linear erosion hollows of a drain are
formed. In total more than 70 hollows run into the
lake.
Other remarkable form of a relief is gullies with the
extent from several up to ten and more meters.
Especially quickly they develop in ruts of roads after
showers.
On flat slopes of low raisings sections of a plane
drain with the area from several square meters up to
several tens square meters are formed. On hollows
of a drain and gullies drift of rocks from the peneplain
to accumulative one and directly to the lake
Baskunchack occur. As a result Khvalynian
adjournments are drifted and more ancient rocks
frequently submitted by gypsums come onto the
surface.
Special interest is represented by karstic forms of a
relief. The karst area of Baskunchack, according to
A.G.Chikisheva and N.A.Gvozdetskogo's
classification concerns to PriBaskunchack karstic
district of Western - PriCaspian karstic province of
PriCaspian karstic area of the East Europe karstic
country.
The karst area of the lake Baskunchack is caused by
the exit onto a day time surface of sedimentary rocks
of late Paleozoic age, submitted by late Perm
gypsums of Kungurian stage. Gypsums are lifted
onto a day time surface owing to hydrochloric
tectonics and make the top part of the salt dome
massive in which modern karstic processes
intensively progress and which is the most accessible
to researches. Karstic gypsums border the bowl of
Baskunchack non-uniformly.
Karstic gypsums are strongly dim from a surface and
are blocked by a thin cover of adjournment.