Constraining the extent of Greater India: New late Paleocene paleomagnetic data from the Tethyan Himalaya, Tibetan Plateau

Abstract

The collision of India and Asia formed the Himalayas and caused the uplift of the Tibetan Plateau. Greater India comprises the part of the Indian plate that was subducted beneath Asia and the Tethyan Himalaya. Quantitative constraints on the extent of Greater India are needed to study the process of the India-Asia collision. However, such constraints are lacking and the topic remains debated. We present paleomagnetic data from late Paleocene (∼58 Ma) mafic rocks from the western Tethyan Himalaya. The mean paleomagnetic direction is Ds/Is = 348.5°/+6.5° with k = 38.7 and a₉₅ = 5.2°, which passed the fold, reversals, and paleosecular variation tests. The results define the paleolatitude of the Tethyan Himalaya as 3.3 ± 4.5°N at ∼ 58 Ma for the reference site of 29.9°N/83.3°E. A comparison of the Paleogene paleolatitudes of the Tethyan Himalaya shows that the terrane moved northward by 1540 ± 290 km between ∼ 60 Ma and ∼ 50 Ma, with a rate of movement of 15.4 ± 2 cm/yr. The new paleomagnetic result confirms that the extent of Greater India was 1130 ± 400 km and was essentially uniform from east to west. This finding implies that the collision between India and Asia was nearly be quasi-synchronous from the middle-eastern to western segments along the Indus-Tsangpo suture zone.