Post‐50 Ma Evolution of India‐Asia Collision Zone From Paleomagnetic and GPS Data: Greater India Indentation to Eastward Tibet Flow. Issue 1 (29th December 2021)

• Record Type: Journal Article
• Authors: Todrani, A.; Speranza, F.; D'Agostino, N.; Zhang, B.
• Is Part Of: Geophysical research letters. Volume 49:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-29
• Subjects: paleomagnetism -- GPS -- Tibet -- Indochina -- rotation -- indentation; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL096623
• Languages: English
• ISSNs: 0094-8276

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. Plain Language Summary: The geodynamic evolution of the Tibetan Plateau and India‐Eurasia collision zone is a matter of vivid debate since the 1970s. In order to assess the deformation of Tibet and north Indochina during the last 50 Ma, we compared 357 paleomagnetic data sets with the present‐day GPS velocity field. Paleomagnetic data suggest that the NE corner of the India plate collided with southern Eurasia at ∼50 Ma, inducing the formation of a continental reentrant with opposite paleomagnetic rotations on curved orogen limbs. Conversely, the post‐30 Ma scattered paleomagnetic rotation pattern of SE Tibet and N Indochina documents a highly fragmented upper crust since middle Cenozoic times. Finally, the Global Position System velocity field shows that at present SE Tibet is characterized by an E‐SE‐ward crust flow and a wide‐scale geodetic clockwise rotation around East Himalayan Syntaxis at a 1–2°/Ma rate. Geologic data indicate that the present‐day kinematics started around 15–10 Ma, and has not yet produced significant paleomagnetic rotations. Key Points: The reliability of 357 Jurassic‐Holocene paleomagnetic datasets from Tibet‐Indochina is addressed The Cenozoic paleomagnetic rotation pattern is compared with the geodetic rotation rate from Global Position System velocity field Collision with NE corner of Greater India at 50 Ma yielded a wide orogenic reentrant and counterclockwise rotations in SE Tibet