29 Cenozoic Tectonics in Asia and North America: Linking Processes Across Scales

This session invites research integrating geologic, geomorphic, and paleoclimate data to advance understanding on orogenesis, seismic hazards, and global change.

Tuesday, 19 May 2026
1:30 PM - 4:30 PM
Alvarado A

Understanding the history of Altai Mountain uplift through an inversion of fluvial topography and implications for the Late Cenozoic aridification of continental interiors

Paper number: 29-0
Program: Technical Sessions
Time: 1:30 PM – 1:50 PM

Authors

Abstract

Reconstructing base level fall histories through the inversion of fluvial topography has emerged as a useful complement to geologic and geochemical proxies seeking to demonstrate coupling among Earth surface processes, atmospheric processes, and global change. Here we invert river channels draining the flanks of the Mongolian Altai and Khangai mountains of western Mongolia. Our goal is to determine the onset and growth of topography capable of intercepting moisture and contributing to the Late Cenozoic aridification of central Asia. The approach is predicated on the detachment-limited stream power law where a uniform rock erodibility is linearly proportional to catchment-wide normalized stream steepness and erosion rate observables. Under these simplifying assumptions we calculate the channel response time with respect to elevation to determine the rate of base level change. Additional mapping of channels onto geologic units accounts for an alternative non-uniform rock erodibility model. We focus on fifteen catchments ranging in size from ~10 - ~1000 km2 with known or pending alluvial terrestrial cosmogenic nuclide and/or low-temperature thermochronometry erosion rates ranging from ~10 – ~50 m/Myr. Piedmont locations ~1 km downstream of the sharp topographic break defined by range-bounding continental-scale strike-slip faults is chosen as a common starting point for the inversions. The uniform erodibility model for Altai catchments shows slow rates of base level fall of < 20 m/Myr prior to ~25 Ma that then increase to ~80 m/Myr by ~15 Ma. Base level fall slows to ~40 m/Myr from ~15 - ~5 Ma at which point there is second, sharp increase to ~60 - ~80 m/Myr before decreasing again to ~40 m/Myr from ~5 Ma to the present. The non-uniform erodibility model refines but does not change the overall base level fall reconstruction. These results are mirrored by catchments in the Khangai Mountains suggesting that base level fall is responding to temporally coincident tectonic and regional dynamic uplift processes. Remarkably, the middle Miocene and early Pliocene pulses in base level fall predicted by the fluvial inversions match the timing of unconformities revealed by a new paleo- and rock-magnetic age model for syn-orogenic growth strata exposed on the Altai piedmont. We conclude that Altai surface uplift commenced in the late Oligocene, grew significantly through the early Pliocene, and continues to uplift and widen through the present.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410616

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