C - Lublin

SOIL SALINITY AND CLIMATE CHANGES IN THE PAST
Eltsov M.V., Borisov A.V., Demkin V.A.
During the 2001-2002 years the research workers of the Institute of
Physicochemical and Biological Problems in Soil Science RAS have carried out
the field investigations of burial places disposed in the Volgograd region. The basic
method of research was the method of archaeological pedology. This method
consists in joining investigation of modern soils and paleosols of archaeological
monuments constructed at different periods of history.
Paleosoils of different ages (the beginning of the 3-d Millennium BC, the first
part of the III Millennium BC, the turn of the III-II Millennium BC, first century
AD, the II-III centuries AD, the first part of the XIII century AD) buried under
burial mounds as well as modern surface soils have been investigated. These soils
are chestnut and chestnut-like calcareous saline soils.
All studied soils have great carbonate content, with the carbonate
neoformations in the form of nodules and impregnation prevailing. In the layer of
0-200 cm the carbonate content was not changed. The depth of HCl-reaction varied
from 21 to 33 cm. The carbonate content in the soil layer of 0-50 cm was highest in
the soils of the turn of the III-II Millennium BC; the lowest one was in the
medieval paleosols.
It was established, that during the last 4500 years the salt content in the soils
under investigation varied significantly. For the second part of the III Millennium
the soil salinity increased more then by 50%, with the upper boundary of the salt
accumulation zone replacing from the depth of 130 cm to 55 cm. The lowest
salinity (0.54%) observed in the paleosols buried at I century AD. But already by
the III-IV centuries AD the soil salinity increased in about three times (the salt
content was 1.3%). The medieval paleosols were leached from the easily soluble
salts and gypsum due to the strong increasing precipitation occurred at the XIII-
XIV centuries AD.
It is typical of the paleosols of all historical periods the presence of gypsum
accumulative horizon. The gypsum content did not vary significantly and only
paleosols of the turn of the III-II Millennium AD had more than 1% of gypsum.
During the next epochs the leaching gypsum from the soil and accumulation of it in
the soil-forming rocks occurred.
The temporary changes of the soil salinity described above were mainly caused
by climate condition changes in the past.
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