The Palinostratigraphy of Sarmatian Deposits of Eastern Georgia.pdf
The Sarmatian deposits of Eastern Georgia were learned using the palynological method. About 200 samples were analyzied from Lower, Middle and Upper Sarmatian layers distributed on territory of Kartli (sections of Aragvi-Bebristsikhe and Nadarbasevi) and Kakheti (sections of David-Gareji and Gombori). Most of the samples contained sufficient numbers of palynomorphs enabling calculation of the percentage of separate plants in the composition of pollen assemblages.
A total of about 199 forms were identified that belong to 129 genera and 88 families. The data significantly enriched the knowledge about Sarmatian flora of Eastern Georgia, which had been previously studied only from macrofossils, in whose composition ferns, grasses and conifers were presented very poorly. Besides, microfossils on territory of Eastern Georgia are only associated with the deposits of Lower and Middle Sarmatian. As for pollen and spores, these are present in all substages of the Sarmatian, which allows tracing the dynamics of the vegetation cover and distinguishing the development stages. These data can be used as a basis for subdividing the Sarmatian deposits into small stratigraphic units – palynozones. Two types of diagrams were generated for the Sarmatian deposits of Eastern Georgia: a traditional palynological diagram reflecting the percentage of separate plants, and a diagram presenting groups of plants grouped by their climatic and ecological requirements. Overall analysis of the diagrams enables tracing of both the evolution of flora and vegetation. The process primarily included decrease of the composition of hygrophilous forests, overall forests shrinking, and expansion of wordless areas. The changes occurred under the influence of climatic fluctuations, mainly associated with reduced humidity. Our materials suggest that the xerophytisation of climate in Eastern Georgia began in early stretches of the Sarmatian but became more intense in the Late Sarmatian, as reflected in all sections we studied. The process of xerophytisation went differently in different regions of Eastern Georgia, being very intense in Kartli and weaker in Kakheti.
Five stages (palynozones) of vegetation evolution in Eastern Georgia were identified on basis of changes in the composition of pollen assemblages during the Sarmatian period. All the five stages are present in the Aragvi-Bebristsikhe section. Only palynozone III is missing in the Nadarbasevi section, which may be associated with Buleishvili’s supposition that the continental regime in this region came later (end of Middle Sarmatian) than in other regions of Eastern Georgia. At the same time the Nadarbasevi section has a comprehensive representation of the palynozones (I, II, IV, V).
In Kakheti, an area similar to Aragvi-Bebristsikhe is the David-Gareji section, even though palynozone I (Lower Sarmatian) is missing there. Yet the other palynozones (II-V) are well correlated with those of the Sarmatian deposits in Kartli.
The Gombori section is somewhat problematic as it may be divided into 2 parts according to the fauna data and information from the pollen analysis. The lower part earlier dated as Lower-Middle Sarmatian by the fauna data was referred to palynozones I-II, and the upper part – to palynozone V.
All sections the pollen assemblages of palynozone V show similar changes in the character of vegetation and in climatic conditions, mainly towards reduction of humidity.
The identified palynozones we compared to zones identified by data on foraminifers. By paleoecological conditions, the palynozone I and the upper part of faunistical zone II are well correlated. The palynozone II which reflects the conditions of climatic optimum can be compared to faunistical zones III-IV, corresponding to the period of strongest foraminifers development. Both the palynozone III and faunistical zone V reflect deterioration of living conditions for fauna and for flora.
The established palynozones can be used for subdividing the Sarmatian deposits of Eastern Georgia into small geochronological units – palynozones.
