The West Burma Terrane, a review of recent paleo-latitude data, its geological implications and constraints

Abstract

Recent, high quality palaeomagnetic data from the West Burma Terrane (WBT) indicates rapid northwards translation (>2000 km) of the terrane, at about the velocity of the Indian Plate, from a near equatorial position in the Late Eocene until the present. This interpretation has important implications for: 1) the controversy over the configuration of Greater India prior to collision with Eurasia, 2) Cretaceous-Cenozoic plate restorations for the eastern Tethys and India Ocean, 3) when the terrane was rift from northern Gondwana, 4) the configuration of SE Asia at the end of the Indosinian orogeny, 5) understanding the general tectonic development and processes of oblique collision zones on the margins of unequal-size colliding continents. The palaeomagnetic data suggest coupling of the WBT with NE India and subsequent encounter of the WBT with SE Asia along a transform margin during the latest Eocene or Oligocene. Due to the significant implications of the palaeomagnetic model, it is important to test the implied development of the WBT against what is known of the regional geology. This study reviews the possible tectonic reconstructions for the Andaman Sea and proposes a configuration that minimises the problems with the testable geological observations. However, it remains difficult to justify the reconstruction with respect to the following aspects: 1) transform fault zone location in the Andaman Sea, 2) Andaman-Sumatra subduction zone evolution, 3) location of the Cretaceous-Eocene eastern boundary of the WBT, and 4) weak evidence for the loss of oceanic crust between the Burma Terrane and Sibumasu during Palaeocene-Eocene convergence. Consequently, there are considerable incompatibilities between geological data and the palaeomagnetic model. Substantial work is required to determine whether these incompatibilities reflect unidentified issues with the palaeomagnetic data, or deficiencies in our geological understanding.