ИСТИНА

THE PHASES OF EXTREME AND OPTIMAL DEVELOPMENT OF THE LANDSCAPE AND PALEOSOLS OF CENTRAL MEXICO OVER THE PAST 40,000 YEARS. Svetlana Sycheva, Sergey Sedov, Elisabeth Solleiro-Rebolledo Multiple alternations of the periods of optimal landscape development when predominantly soil formation took place and the episodes of instability comprise a prominent feature of the natural history of Central Mexico in the late Pleistocene and the Holocene. The rates of geomorphic and sedimentary processes during these episodes were extremely high: in some sites deposits accumulated, in the other – erosion of soils and sediments as well as gully incision took place. A complex mosaic of trends and rhythms (cycles) of landscape evolution was recorded in the structure of the soil-sedimentary sequences. The results of investigations of the Pleistocene and the Holocene strata are presented in this the article. Two paleosols corresponding to the warming in the middle of the Late Pleistocene 38-26 ka BP, two paleosols belonging to the last Glacial maximum 24-19 ka BP and two/three Late Glacial paleosols were identified. In the second half of the Late Pleistocene Luvisols developed under coniferous forests, that reflects cool humid paleoclimatic conditions. Acceleration of geomorphic processes took place within the intervals 18-14 and 12-9 ka BP. In the Holocene the evidences of the 2000 yr rhythm of soil and relief development were detected. Most humus rich and fertile soils were developed during the Holocene optimum (8-5 ka BP). They reflect warm and moist climatic conditions optimal for pedogenesis. The period 4,3-2,3 ka ВР was quite dynamic concerning development of landscapes and their components: less stable conditions prevailed with cooler periodically dry climate. The episode of strong drought is identified 4,2 ka ВР. After 2300 yr. BP human impact became the leading factor in the landscape development.