9 Cenozoic Tectonics in Asia and North America: Linking Processes Across Scales (Posters)

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

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Paleomagnetic Age Model for Late Cenozoic Sediments at Khyargas Nuur and Zereg, Altai Mountains, Western Mongolia

Paper number: 9-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Altai Mountains of western Mongolia are a lofty intraplate orogen positioned astride the mid-latitude westerlies. As such, the timing of their growth may have influenced the drying of central Asia and subsequent Cenozoic aerosolic fertilization of the western Pacific Ocean. Our research seeks to construct an age model for the emergence of this range by leveraging well-exposed growth strata in the flanking piedmont basins, which is a direct consequence of the outward and upward transpressional propagation of mountainous topography. We measured and sampled several hundred meters of growth strata spanning the Uush, Khyargas Nuur, and Altanteel formations in three sections of the Khyargas Nuur and Zereg basins in the proximal and distal lee of the Altai, respectively. We collected 196 oriented specimens of fine sandstone and mudstone for paleomagnetic analysis. Specimens were thermally demagnetized through ascending heating stages up to 690 °C to remove post-depositional minerals susceptible to the Earth’s magnetic field. The resulting demagnetization vectors are plotted in geographic and sample coordinates on Zijderveld and Virtual Geomagnetic Pole diagrams in order to determine polarity during deposition. The resulting reversal stratigraphy, when combined with broad age estimates from biostratigraphic and sediment accumulation rate (SAR) cyclostratigraphic data, allow for a correlation to the Geomagnetic Polarity Timescale (GPTS) and generation of an age model. Our model indicates that the growth strata span ~6 Myrs and initiated with the Uush Formation in the Late Miocene ~9 Ma atop an angular unconformity that truncates older Oligocene to Cretaceous strata. These results indicate significant growth of Altai topography in the early and middle Miocene. Younger growth strata of the Khyargas Nuur and Altanteel formations best match the latest Miocene to Pliocene section of the GPTS and represent a ten-fold slowing of SAR from ~200 m/Myr to 20 m/Myr as the range continued to grow upwards and outwards destroying basin accommodation space. This age model coupled with the now full exposure of the growth strata indicate that the Mongolian Altai are a young mountain range that reached elevations and/or widths capable of casting a significant rain shadow only in the Pliocene and Pleistocene.  

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

doi: 10.1130/abs/2026RM-410525

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