Mongolian Summit Plateaus: Uplifted Mesozoic Erosion Surfaces or the Leveling of Topography by Quaternary Glacial and Periglacial Processes?
Abstract
High mountains with low relief summit surfaces or plateaus are common across western Mongolia and southern Siberia. These flat-topped mountains exist in the Gobi and Mongolian Altai, the Hangay Mountains, and the trans Hovsgol-Sayan Ranges. These surfaces have classically and recently been interpreted as fragments of one or more low-elevation erosion surfaces dating to the Mesozoic and early Cenozoic that have been elevated by late Cenozoic tectonic uplift, yet are still preserved. In this first hypothesis, the low-relief summit surfaces represent the slowest eroding part of the mountain landscape, where lower elevation summits lacking these surfaces must represent regions of faster erosion through the paleoerosion surface (s). We observe a positive correlation between the regional elevation of reconstructed glacial equilibrium line altitudes and mountains with low-gradient summit plateaus. Topographic metrics including hypsometry, relief, and altitudinal variations in surface roughness across these mountain ranges suggest to us that an alternative hypothesis may explain the origin of flat-topped mountains in Central Asia. Specifically, in mountainous regions experiencing slow to moderate rates of uplift, the intersection of topography with the mean elevation of glacial and/or periglacial processes may be limiting elevation and relief production. In this latter scenario, the high summit plateaus would have faster erosion rates than lower elevation mountains that have not yet been uplifted to the point where their summits intersect the glacial-periglacial "sanding block". If correct, the long road to flat mountain-top surfaces found across western Mongolia may be much younger than previously thought, owing their existence to the establishment of a cooler Quaternary climate resulting in more active glacial and periglacial erosional processes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMEP41D0641W
- Keywords:
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- 0710 CRYOSPHERE / Periglacial processes