Late Miocene Oroclinal Bending of the Mazatagh Thrust Belt in the Central Tarim Basin and Its Tectonic Implications

Abstract

The arcuate Mazatagh thrust belt (MTB) in the central Tarim Basin is one of the key regions for understanding the Cenozoic intracontinental deformation in response to the India–Eurasia collision. However, whether it was formed due to oroclinal bending and its kinematic processes remain unclear. Here, we present a detailed paleomagnetic rotation study at Hongbaishan in the middle MTB to shed new light on the deformation in this region. Positive fold and reversal tests of 50 site means suggest primary magnetizations. The paleomagnetic declinations indicate ∼14.6 ± 8.5° absolute clockwise rotation at Hongbaishan since the late Miocene (∼7.6 Ma). Together with the rotation results calculated from Hongbaishan-1 and Mazatagh magnetostratigraphic data sets in the southeastern MTB, these results reveal an increasing magnitude of clockwise rotation along the belt toward its southeastern tip. Positive oroclinal tests along the MTB suggest the occurrence of oroclinal bending that curved the originally straight MTB before and during the deposition of its lower part, and nearly half of the bending had occurred during the deposition of its upper part. This oroclinal bending is mostly attributed to the northward indentation of the West Kunlun Mountains along the décollement salt‒gypsum layers and further implies ∼7.9° absolute clockwise rotation of the Tarim Basin since the late Miocene. Integrating these findings with other lines of geological evidence around the Tarim Basin, we propose that episodic widespread tectonic deformation with basinward propagation occurred since the late Miocene due to the far-field effect of the continuous northward indentation of the Indian Plate into Eurasia.