Геологическая история и фауногенез Казахстана и сопредельных территорий в эпохи развития млекопитающих и антофильных насекомых

TETHYS Entomological Research
№ 1, 1999

promoted penetration of xerophilous elements of Gondvana fauna onto the territory of Central Asia. The 
grassy communities began to occupy huge areas. In miocene angiospermous plants have grasped
prevailing positions in flora. The landscape zones began to get shape close to modern one. Mesophilous
turgay species retreated to Tien-Shan and other mountain systems in connection with aridisation of the
climate. The changes in fauna had similar character. 
In pliocene an outline and the surfaces of continents were already almost identical to modern one.
On the territory of Kazakhstan and Central Asia the early- and middle pliocene was characterized by the 
maximal development of dry land, but in late pliocene twice powerful transgression of the sea took
place. At the end of the period first glaciers have appeared at the tops of the mountains. The climate as a 
whole became more cold. Generated in the first half of neogene landscape-geographical zones have
moved to the south, though in comparison with their modern localisation they were situated a little to
the north. The world of animals and plants was richer, than now, though many tropical and subtropical
forms have died out or have occupied narrower areals. In pliocene there were all basic types of modern
deserts with complexes of the specialized plants and animals already. In pliocene there was a sharp
division of biota on the mountain type and the plain one. Central Asia became the powerful centre of
formation of new taxa, that is connected with orogenetic processes and formation of deserts. 
In pleistocene general outlines of continents remained the same, as in pliocene as a whole, though
the details of a coastal line varied depending on fluctuations of a level of global ocean. In Kazakhstan
and Central Asia the formation of all modern mountain systems proceeded. The raising of mountains
has caused their strong erosive partition and formation of the foothill alluvial loop. The plains began to
get shape close to modern. Alluvial deposits owing to winnowing formed large sandy deserts and loess
cover at foothills of the mountains. The climate and the nature as a whole were various and frequently
varied, and a variety of the nature amplified with current of time. In Kazakhstan and Central Asia there
were fluctuations of a climate sometimes in a form of glacial periods (in mountains) and sometimes in 
mitigation and partial humidifying of a climate. General drop in temperature led to disappearance of
many tertiary species of animals and plants or moving of borders of the areals in a direction from the
northeast to the southwest, and the alternation of the dry and damp, cold and warm periods promoted
penetration of boreal elements in southern areas and vice versa. In holocene the processes,
characteristic for pleystocene proceeded. There was also an alternation of damp and dry, cold and warm
climatic phases. Essential role in formation of fauna and flora after deviation of glaciers was played by
xerotermic phase which had caused strong development of desert, semidesert and steppe forms. In last
milleniums of holocene the influence of the man on nature took place, especially in a foothill strip, which 
has been transformed gradually by man into a continuous area of oases. 
Thus, the basis of the fauna of Kazakhstan and Central Asia has already developed to the end of
mesozoic - beginning of cenozoic. The basic directions of changes of natural conditions for cenozoic
were drop in temperature, which came from the north, continentalisation and drying of the internal
parts of Eurasia. These basic directions of changes of abiotic conditions were the most important factors 
of formation and evolution of biota. They also defined basic directions of migrations (from the north to
the south and from the centre to the west and to the east) and territories of the greatest transformations 
of biota (northern and internal parts of continent). The directed reduction of the Tethys and raising of a
number of mountain systems, and in quaternary period - influence of the glacial periods have also played 
a huge role in formation of fauna and flora and their migrations. The certain importance had migrational
processes connected with an establishment or break of connections with other continents. The most
important factor in formation of the fauna of Central Asia and Kazakhstan was, apparently, gradual
aridisation of the climate which has begun in the end of the cretaceous period, which has resulted at
first in formation of vast areas of savannas, then steppes and at last semideserts and deserts. The
successive existence of arid conditions, since the end of cretaceous-beginning paleogene, during all
cenozoic promoted to local processes of fauna formation. Alpine orogenesis is the other important
factor, that has caused intensive development of new types of fauna and appearance of great amount of
endemic species and rich genera. 
Thus, the origin of fauna of Central Asia and Kazakhstan is mixed: transformational-migrational.
Quaternary transformation of abiotical conditions has played a very important role in the change of
fauna and its enrichment with migrants of a different origin, but tertiary nucleus was kept till now and
still has a very appreciable place in the structure of fauna. 
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В.Л. Казенас, Б.У. Байшашов 
Геологическая история и фауногенез Казахстана...