Patterns of active faulting and paleomagnetic data suggest recent (last 5 m.y.) onset of deformation in the eastern Mongolian Altay
Abstract
The Altay Mountains in western Mongolia are actively deforming as a far-field result of the collision between India and Asia. Convergence across the Altay is oblique, with at least six major fault zones being present. Each of these fault zones preserves evidence for right-lateral strike-slip activity in the Quaternary, coupled with evidence for reverse-oblique slip motion. The NNW-SSE orientation of the major fault zones, and their dextral sense of slip, combined with earthquake source parameters, and GPS velocities indicate that shortening in a NNE direction is accommodated by anti-clockwise vertical axis rotations. Palaeomagnetic rotations of up to 39° anticlockwise have previously been reported from Oligocene-Pleistocene sediments of the Chuya Basin in the Siberian Altay, but little work has been carried out elsewhere in the Altay. We present new palaeomagnetic results from 16 sites in Miocene in Jurassic to Cretaceous, Oligocene, and Plio-Pleistocene aged sediments from the Dzereg basin in the eastern Altay. Detailed thermal demagnetization has uncovered a multiple-component remanence structure in the majority of the samples. The highest stability component passes fold and reversal tests suggesting a primary or near-primary origin of magnetisation. In common with many other studies of sediments in Asia, our recorded inclinations are slightly shallower than those predicted from the appropriate reference poles for Eurasia, suggestive of a primary detrital remanent magnetisation. Although the declinations overall look scattered, when corrected for the age-appropriate reference pole, all localities match the data, indicating that no significant rotations have affected this part of the Altay. This lack of accumulated rotations in the eastern Altay, together with geomorphic observations of the faults, and measurements of Quaternary slip-rates suggests that much of the deformation in the eastern Mongolian Altay has occurred within the last 5 million years.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2013
- Bibcode:
- 2013AGUSMGP42A..07M
- Keywords:
-
- 8108 TECTONOPHYSICS / Continental tectonics: compressional;
- 8111 TECTONOPHYSICS / Continental tectonics: strike-slip and transform;
- 1525 GEOMAGNETISM AND PALEOMAGNETISM / Paleomagnetism applied to tectonics: regional;
- global