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SM ISO690:2012 АЛЕКСЕЕВ, Василий. Гипергенез, возраст черноземов, кор выветривания и покровных отложений водоразделов Молдовы
. In: Buletinul Institutului de Geologie şi Seismologie al AŞM, 2011, nr. 1, pp. 124-142. ISSN 1857-0046. |
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Buletinul Institutului de Geologie şi Seismologie al AŞM | |||||
Numărul 1 / 2011 / ISSN 1857-0046 | |||||
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Pag. 124-142 | |||||
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For the first time there were studied hypergenic processes in cover deposits of watersheds
of Moldova. Reliability of the existing processes has been proved by comparative investigations of
hypergenic transformations of mineralogy in two parallel subtype series (western and eastern) of
chernozems, which demonstrated coincidence of their common direction. The changes go by
eluvial type.
Processes of weathering and soil formation on the territory of modern Moldova has been
continuously going for the last 6-9 million years. It was shown, that mineral material of the cover
deposits was inherited from rocks of planation surfaces of the late Miocene and Pliocene, which
mainly in Pleistocene experienced loessification, which also affected indigenous rocks of the tops
of watersheds. Aeolian process took no considerable part in formation of cover deposits. It was
established that active age of mineralogical profiles of modern chernozems of Moldova’s
watersheds and genetically linked with them weathering crust is measured by 20-40 thousand
years in its southern part and 40-70 thousand years in the northern one. This proves that the tops
of watersheds had not preserved the original state of rocks belonging to the ancient planation
surfaces. Despite classic views it was found that nucleation and formation of the mineralogical
profiles of chernozems and weathering crusts on surface rocks occurred not in Holocene, but in
the upper Pleistocene, that at the same time indicates to polygeneticity of the chernozems
themselves. Huge break between duration of the hypergenic processes on the given territory and
the age of real mineralogical profiles of automorphic chernozems and weathering crusts is
explained by geological denudation of cover deposits on watersheds.
Formation of modern mineralogical profiles of these deposits is integral result of climate
action, time and mechanical geological denudation. Proportion in action of these factors in the
upper Pleistocene and Holocene combined in such a way that climatic factor or chemical
weathering outstripped the mechanical denudation of flat interfluves of watersheds, while time
played role of a factor of going processes. Immature weathering crusts are formed on slopes of
watersheds due to increased denudation.
It was established that chernozem as a type and its subtypes are genetically linked with
silicate weathering crust of the corresponding to each subtype degree of maturity, and these
changes are irreversible. To each automorphic soil corresponds its silicate weathering crust. The
age of the weathering crust is equal to the age of mineralogical soil profile. The observed in
nature absence of ideal soil zonation on relatively flat territories in climatic zone with similar
rocks can be explained by action of block neotectonics, and also by different age of watershed
surfaces.
In formation on the north of Moldova of more mature weathering crusts significant
antidenudation role could be played by vegetation at all times of different epochs of soil formation,
more expressed in the north than in the south. In Moldova’s conditions the age of watershed
weathering crust can’t be used for determination of the age of surface deposits and cannot be
opposed to the dating of geologists by rock stratification due to its rejuvenation as a result of
continuous geological denudation. Polynov’s view of possibility of formation of allitic weathering crust in any climate, for a sufficiently long period of time, in some additional conditions do not
contradict to our obtained data on hypergenic changes of deposits on watersheds of Moldova.
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