Early Cretaceous paleomagnetic and geochronologic results from the Tethyan Himalaya: Insights into the Neotethyan paleogeography and the India-Asia collision.

Yiming Ma,Huaichun Wu,Jingjie Jin,Weiwei Bian,Shihong Zhang,Haiyan Li,Tianshui Yang

doi:10.1038/srep21605

Abstract

To better understand the Neotethyan paleogeography, a paleomagnetic and geochronological study has been performed on the Early Cretaceous Sangxiu Formation lava flows, which were dated from ~135.1 Ma to ~124.4 Ma, in the Tethyan Himalaya. The tilt-corrected site-mean characteristic remanent magnetization (ChRM) direction for 26 sites is Ds = 296.1°, Is = −65.7°, ks = 51.7, α95 = 4.0°, corresponding to a paleopole at 5.9°S, 308.0°E with A95 = 6.1°. Positive fold and reversal tests prove that the ChRM directions are prefolding primary magnetizations. These results, together with reliable Cretaceous-Paleocene paleomagnetic data observed from the Tethyan Himalaya and the Lhasa terrane, as well as the paleolatitude evolution indicated by the apparent polar wander paths (APWPs) of India, reveal that the Tethyan Himalaya was a part of Greater India during the Early Cretaceous (135.1–124.4 Ma) when the Neotethyan Ocean was up to ~6900 km, it rifted from India sometime after ~130 Ma, and that the India-Asia collision should be a dual-collision process including the first Tethyan Himalaya-Lhasa terrane collision at ~54.9 Ma and the final India-Tethyan Himalaya collision at ~36.7 Ma.

Highlights

Which includes a first collision of the Tethyan Himalaya with Asia at ~50–55 Ma and a final continent-continent collision of the Indian craton with the Tethyan Himalaya at ~20–25 Ma14 or ~40 Ma12,20
Considering that the sedimentary rocks often suffer from compaction-induced inclination shallowing[20,30,31,32], whereas the volcanic rocks are immune from its effect, we carried out a combined geochronologic and paleomagnetic study on the Early Cretaceous Sangxiu Formation (Fm) lava flows in the Tethyan Himalaya
Samples ZL1 and ZL23 yield weighted mean 206Pb/238U ages of 135.1 ± 0.7 Ma and 124.4 ± 0.7 Ma, respectively. These new ages are well consistent with the age of ~133 ± 3 Ma reported by Zhu et al.[33], indicating that the Sangxiu volcanics erupted during the Early Cretaceous

Summary

Introduction

Which includes a first collision of the Tethyan Himalaya with Asia at ~50–55 Ma and a final continent-continent collision of the Indian craton with the Tethyan Himalaya at ~20–25 Ma14 or ~40 Ma12,20. Considering that the sedimentary rocks often suffer from compaction-induced inclination shallowing[20,30,31,32], whereas the volcanic rocks are immune from its effect, we carried out a combined geochronologic and paleomagnetic study on the Early Cretaceous Sangxiu Formation (Fm) lava flows in the Tethyan Himalaya. These new high-quality and well-dated paleomagnetic data can significantly attribute to the two issues mentioned above. The volcanic strata consist of pillowed and massive, sparsely amygdaloidal basalts and minor dacites

Methods

Results

Conclusion