Coupled tectonic-volcanic controls on lava-dammed lake formation: evidence from the Shireet Naiman Lake System (SNL), central Mongolia

초록

Lava-dammed lakes preserve valuable geomorphic records of interactions among volcanism, tectonics, and surface hydrology, providing important insights into volcanic landscape evolution. Advances in remote sensing, digital elevation models (DEMs), and quantitative geomorphometry now enable integrated analysis of volcanic landforms and lava-flow pathways in remote continental settings. The Shireet Naiman Lake (SNL) system in the Orkhon Volcanic Belt (OVB), central Mongolia, comprises a well-preserved group of lava-dammed lakes developed within fault-controlled valleys of the Khangay Mountains. This study integrates DEM-derived morphometric indices, satellite remote sensing, field observations, bathymetric data, and previously published geochronological constraints to evaluate the geomorphic relationships among valley morphology, lava emplacement, and lake formation. Morphometric indices (Vf < 1, Smf = 1.1-1.4, HI generally > 0.5, and mean RS = 37.8 degrees) indicate steep, structurally confined valleys consistent with tectonic influence on landscape morphology. Valley-filling lava flows covering approximately 72.6 km(2), with an estimated mean thickness of 48.6 m and a reconstructed volume of approximately 3.5 km(3), were emplaced during the Late Pleistocene, blocking pre-existing drainage pathways and forming a group of nine lava-dammed lakes. The observed spatial relationships among fault-controlled valleys, lava-flow distribution, and lake basins suggest that inherited structural topography likely guided lava emplacement and subsequently influenced lake development. These findings demonstrate the value of integrating remote sensing, quantitative geomorphometry, and field observations for reconstructing the evolution of lava-dammed lake systems, while indicating that the SNL represents a well-preserved example of tectonically influenced volcanic landscape evolution rather than direct evidence of synchronous tectonic and volcanic processes.

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