Cenozoic Uplift of Tanggula Range and Tuouohe Basin, Northern Tibet: Insights of the Anisotropy of Magnetic Susceptibility

The timing and intensity of deformation of the Tanggula Range and Tuotuohe Basin are in debatable but strengthening the research on them is necessary for better understanding the geodynamic models of the Tibet and the tectonic-climate connections during the Cenozoic. Here we present the anisotropy of magnetic susceptibility (AMS) records from the foreland Tuotuohe Basin to understand the tectonic uplift history of the Tanggula Range for the interval of similar to 37-19.7 Ma. Rock magnetic analyses indicate that the main magnetic carrier is paramagnetic and the minor is hematite. Thus, the AMS in the Tuotuohe Section (TS) can be used to track the tectonic strain related to tectonic processes. The distribution direction of the maximum principle susceptibility (K-max) is approximately NW-SE, which intersects at about 10 degrees with the strike of the strata and is nearly parallel to the Tanggula thrust fault system, whereas the minimum principle susceptibility (K-min) is oriented in the NE-SW direction with a girdle distribution. This is consistent with the sedimentary fabric imprinted by the NE-SW shortening direction, representing the earliest deformation stage. AMS data in the TS can be divided into two phases at 30 Ma. From similar to 37 to 30 Ma, the AMS parameters indicate an active tectonic strain and the Tanggula Range uplift induced by the India-Asia convergence, whereas between 30 and 19.7 Ma, the strain is weak compared with the earlier phase. Finally, the weak strain environment between 30 and 19.7 Ma indicated by the AMS indexes of the TS and the paleoelevation evidence from the Tuotuohe Basin all together suggest that an additional 1000-2000 m of surface uplift of the basin may have begun after 19.7 Ma.