Post‐50 Ma Evolution of India‐Asia Collision Zone From Paleomagnetic and GPS Data: Greater India Indentation to Eastward Tibet Flow
Alessandro Todrani, Fabio Speranza, N. D’Agostino, Bo Zhang
Abstract
Abstract We re‐evaluate 357 Jurassic‐Holocene paleomagnetic datasets from Tibet‐Indochina and compare them with present‐day Global Position System velocity field. SE Tibet NW of the East Himalaya Syntaxis (EHS) underwent 20°–30° counterclockwise rotations around 50 Ma, and mostly clockwise rotations after 40 Ma. NE of the EHS, post‐50 Ma clockwise rotation occurred, whereas highly scattered clockwise rotations took place on northern Indochina at 25–15 Ma, after a remagnetization episode. We suggest that the indentation of Greater India NE corner at ∼50 Ma resulted in a wide orogenic reentrant characterized by opposite rotations at orocline limbs. Rotations East of EHS after 40 Ma were likely due to local strike‐slip fault activity. After 30 Ma, the ongoing India collision fragmented Indochina into km‐scale blocks that experienced independent rotations. The present‐day clockwise rotation pattern around the EHS started at 15–10 Ma along with eastward Tibet crustal spreading, and has not produced yet a detectable paleomagnetic rotation.