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

Cyclostratigraphic-based sediment accumulation rates of late Cenozoic sediments in the Khyargas Nuur and Zereg basins, Mongolian Altai, western Mongolia

Paper number: 29-2
Program: Technical Sessions
Time: 2:10 PM – 2:30 PM

Authors

Abstract

We employ rock magnetic cyclostratigraphy as a complement to traditional paleomagentic age models of synorogenic growth strata to reconstruct the growth of orogenic topography in the Mongolian Altai. This approach improves temporal resolution and independently establishes unsteadiness in sedimentation and crustal deformation rates. These enhancements are critical for constraining when the Altai reached a threshold elevation and width capable of influencing Northern Hemisphere atmospheric circulation, a poorly constrained process spanning ~20 Ma from the Miocene through the Pleistocene.

We targeted three sections of synorogenic Neogene sedimentary rocks of the Uush, Altanteel, and Khyargas Nuur formations in the Zereg and Khyargas Nuur basins of the Great Lakes Depression, western Mongolia. These strata, now inverted following Altai orogenesis, represent fluvial, eolian, paludal, and minor lacustrine facies. Magnetic susceptibility (MS) measurements were collected at 25–50 cm intervals independent of facies or sedimentary texture along two ~200 m sections at Zereg and a ~150 m section at Khyargas Nuur using a handheld KT-10 MS meter. 

MS time series were processed following a standard workflow including linear detrending and spectral analysis using the Matlab-based Acycle software. Spectral power plots in the spatial domain are tested against an AR1 robust red-noise model. Frequency spacing of statistically significant spectral peaks was compared to established Milankovitch periodicities to insert temporal constraints within the stratigraphic sections.

MS variability in the analyzed terrestrial facies is dominantly magnetite with secondary hematite, goethite, and paramagnetic clays. Spectral power peaks mostly match long (405 ka) and short (125-95 ka) eccentricity, with occasional obliquity (41 ka) and/or precession (26 ka). Sediment accumulation rates (SAR) are generally higher at Zereg, located in the lee of the Altai (50-200m/Ma) compared to Khyargas Nuur which lies nearer the Altai core (~30m/Ma). In both cases, the SAR decreases upsection, likely reflecting tectonic slowing of basin subsidence as the Altai core widened and fragmented its foreland. Variable encoding of different Milankovitch periodicities reflects evolving depositional compensation time, the high northern latitude of the site, and/or the young age of the sediments overlapping with Northern Hemisphere ice cap growth. Complementary magnetostratigraphy and existing biostratigraphy anchor the cyclostratigraphic model to the Geomagnetic Polarity Time Scale, indicating late Miocene-Pliocene deposition followed by Pleistocene inversion. 

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

doi: 10.1130/abs/2026RM-410531

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