Phanerozoic Palaeomagnetism of the Indian Plate and the India-Asia Collision
- M.W. McEIhinny and
- D.A. Valencio
Published Online: 15 MAR 2013
Copyright 1981 American Geophysical Union
Paleoreconstruction of the Continents
How to Cite
Klootwijk, C. T. and Radhakrishnamurty, C. (1981) Phanerozoic Palaeomagnetism of the Indian Plate and the India-Asia Collision, in Paleoreconstruction of the Continents (eds M.W. McEIhinny and D.A. Valencio), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD002p0093
- Published Online: 15 MAR 2013
- Published Print: 1 JAN 1981
Print ISBN: 9780875905112
Online ISBN: 9781118670217
- India-Asia collision;
- Indian plate;
- Phanerozoic palaeomagnetism;
- Pole positions;
The Phanerozoic apparent polar wander path (APWP) for Indo-Pakistan is updated on the basis of data obtained during the last decade from Peninsular and Extrapeninsular Indo-Pakistan and Tertiary DSDP core data from the Indian plate. The Palaeozoic part of this APWP is as yet largely undefined. Characteristic features of the APWP are: a) minor polar motion at the Precambrian-Cambrian time boundary and fast polar motion during the Permo-Carboniferous, b) a Triassic-Jurassic loop in the APWP, probably reflecting processes associated with formation of the Neotethys, and c) a Late Cretaceous-early Tertiary kink which separates the Cretaceous trajectory of moderate polar motion from the Tertiary trajectory of major polar motion.
Considerable advances have been made during the last decade with the study of rocks from Extrapeninsular Indo-Pakistan. These results do not have much bearing as yet on the former northern extent of Gondwanic India (pre-Neotethys formation), apart from a preliminary interpretation that the eastern Hindu Kush may have formed part of Asia and not of Gondwanic India since at least the Late Devonian. These Extrapeninsular data, however, contribute importantly to the understanding of the development of the India-Asia collision and the subsequent deformation of Extrapeninsular Indo-Pakistan and south central Asia.
In the Ladakh region (NW Himalaya), initial collision between continental Indo-Pakistan and an island arc off south central Asia occurred during Late Palaeocene-Early Eocene. Continental collision with Eurasia occurred probably during Late Eocene-Early Oligocene as can be concluded from a concomitant decrease in the rate of northward movement of the Indian plate.
Collision tectonics in Extrapeninsular Indo-Pakistan are characterized by a general inward movement of thrust sheets. Rotational movement of several thrust sheets have been determined palaeomagnetically, though concluded magnitudes of rotation may have to be updated upon further refinement of the Tertiary trajectory of the Indo-Pakistan APWP: - The Loralai Range (northeastern Baluchistan) has rotated clockwise over about 50 degrees since the Middle Eocene. Both limbs of the Western Himalayan Syntaxis show contrasting rotations of thrust sheets, a clockwise rotation over about 45 degrees of the Panjal Nappe of Kashmir and a possibly more than 20 degrees counterclockwise rotation of the Salt Range-Potwar Plateau unit. A middle Tertiary clockwise rotation over about 45 degrees is found in the Krol Thrust Sheet.
A comparison of palaeomagnetic data from Extrapeninsular Indo-Pakistan with Eurasian data shows that continuing post-collisional northward movement of Indo-Pakistan resulted in indentation of south central Asia over more than 2500 km. This indentation can be interpreted in part in support of Molnar and Tapponnierf's continental collision model. The Hindu Kush-Pamir-Karakorum syntaxial bend is a secondary feature associated with this indentation.
In this paper we summarize Phanerozoic palaeomagnetic data from Peninsular and Extrapeninsular Indo-Pakistan obtained during the last decade. The data are interpreted in terms of Indo-Pakistan's drift with reference in particular to post-collisional deformation of Extrapeninsular Indo Pakistan and south central Asia. Precambrian palaeomagnetic data will not be discussed. Compilation of a Precambrian APWP seems ambiguous because of poor age control and insufficient evidence for a primary or a secondary origin of the palaeomagnetic data.