Delineating the boundary between the Mongolian Altay and Gobi-Altay Mountain Ranges: A Geomorphic and Geographical Approach

Монгол Алтай, Говь-Алтайн нурууны хил заагийг тогтоох асуудалд: Газарзүй болон геоморфологийн хандлага

Abstract

This study addresses the long-standing academic issue of delineating the boundary between the Mongolian Altay and Gobi-Altay mountain ranges in southwestern Mongolia. A combination of comparative geomorphological analysis and morphometric methods was employed. The results reveal that the Mongolian Altay is characterized by relatively high elevations, glaciated peaks, a more humid climate, widespread permafrost, well-developed altitudinal zonation, and distinctly differentiated landscapes. Geologically, it is dominated by Paleozoic metamorphic and intrusive rocks. Geomorphologically, erosional landforms prevail. In contrast, the Gobi-Altai range exhibits lower elevations, arid climate, limited permafrost distribution, weak altitudinal zonation, and less pronounced landscape differentiation. Its geological structure is characterized mainly by relatively young sedimentary and intrusive rocks, while geomorphologically, both depositional and erosional landforms are common. A key outcome of the present study is the identification of the Huvch - Alag Lake fault zone - extending approximately 100 km - as a morphostructural boundary between the two mountain systems. Morphometric indicators such as hypsometric integral (HI > 0.71), mountain front sinuosity (MFs ≈ 1.1), and steep fault-related slope angles (RSl > 65-71°) provide strong evidence of tectonic and morphostructural contrasts along this fault zone. Furthermore, differences in landscape structure, climate, vegetation, and permafrost distribution reinforce the validity of this boundary. These findings contribute to a more precise classification of Mongolia’s mountain systems and offer significant insights into the ongoing geodynamic processes driven by the India–Eurasia continental collision. Additionally, the study provides a scientific basis for regional ecological, tectonic, landscape, and geomorphological regionalization, as well as for the assessment and sustainable use of natural conditions and resources.