Palaeomagnetic results from the Tibetan Plateau

Abstract

Palaeomagnetic measurements were carried out on 1325 oriented samples collected from 246 sites on a traverse of the Tibetan Plateau from Lhasa to Golmud in 1985, crossing the Lhasa Terrane, Qiangtang Terrane, and Kunlun Terrane. High blocking temperature, high coercivity, statistically grouped magnetizations were isolated from the following units: Lhasa Terrane — Cretaceous Takena Formation, mid-Cretaceous Nagqu volcanics, mid-Cretaceous Qelico volcanics; Qiangtang Terrane - Norian Batang Group volcanics, Kimmeridgian Yanshiping Group, Paleocene to Eocene Fenghuoshan Group; Kunlun Terrane — Visean to Namurian Dagangou Formation, dykes of the Triassic igneous province. The Triassic data from the Kunlun Terrane, Triassic and Lower Tertiary data from the Qiangtang Terrane and the Cretaceous data from the Lhasa Terrane indicate palaeolatitudes ca . 20° S of their present position within the Eurasian frame of reference. A possible interpretation is that the terranes successively accreted to Eurasia and remained in the southern position until the convergence of India drove them northward via a process of tectonic shortening and/or displacement of continental crust. The Carboniferous data from the Kunlun Terrane are consistent with moderate Southern Hemisphere latitude, well separated from Eurasia which was in the Northern Hemisphere at this time, implying the existence of ocean crust between these blocks during the Carboniferous.