Interpretation of Glaciogenic Complexes From Satellite Images of the Mongun-Taiga Mountain Range

Аннотация

This investigation is concerned with the problem of recognition of glacial landforms in arid mountainous areas of Asia using satellite imagery. We examine the territory of the Mongun-Taiga mountain range located at the interface of the Russian Altai, Sayan and Mongolian Altai mountains which has been studied for many years by geographers of St. Petersburg State University. The mountain range is home to modern glaciers totaling about 20 km in area, and its climate aridity is favorable for the preservation of a large body of evidence of ancient glaciation. The theoretical basis for this effort was provided by the idea of GC, i. e. natural complexes, the morphology and structure of which is formed by modern and ancient glaciations. Using the morphological differences we identified three groups of glaciogenic complexes and assigned their formation time to MIS 4, MIS 2, and to the Late Holocene. Results from comparing data of glacio-geomorphological and paleogeographical studies on the territory of the Mongun-Taiga mountain range with corresponding satellite images were used to develop interpretation standards for different groups of GC, forming the basis for compiling the map of GC of the second and third order for the entire mountain range. Cartometric measurements were used in obtaining the main characteristics of the glaciers of the Mogun-Taiga for ten different time spans. It is found that during the MIS 4 maximum the glaciers advanced to the piedmonts, and their area exceeded the present-day area by more than a factor of 25, with the firn line depression of about 800 m. The largest areas were occupied by glaciers of southward aspects, which is accounted for by a predominance of north-westward moisture-bearing glacial streams at that time. The aspect asymmetry of glaciation persisted during the MIS 2 maximum but it had a valley character. It is established that in the Little Ice Age the area of the glaciers exceeded the present-day area by a factor of 2.4, with the firn line depression of 20 m.