Structural and tectonic evolution between Indo-Myanmar ranges and central Myanmar basin: Insights from the Kabaw Fault

Abstract

The Kabaw Fault is a north-south trending arcuate suture zone formed between the accretionary prism of the Indo-Myanmar Ranges (IMR), and the Central Myanmar Basin (CMB). The lineament of the Kabaw Fault is defined as a stratigraphic contact zone between flysch sediments of the IMR and molassic sediments of the CMB along the eastern base of the IMR. The accretionary prism of IMR was initially formed as a single wedge (pro-wedge) during Triassic, however, the forceful subduction of the Indian Plate resulted in the formation of an open wedge (double-sided wedge) during the Cretaceous. The double-sided wedge of the accretionary prism of IMR is revealed by the structural deformation pattern of the molassic sediments and the Triassic flysch exposures in the fore-arc basin of CMB, however, the eastern part of the wedge is buried under the fore-arc basin. At the eastern base of IMR, the ophiolite occurrences are close to the Kabaw Fault except in the Kabaw Valley where the ophiolites are associated with the Jurassic sedimentary rock units. The Kabaw Valley is generally occurred as a north-south elongated lowland basin, positioned along the western part of the Kabaw Fault. The east-dipping geometry of the Kabaw Fault is manifested by the evidence of east-verging synclinal folds of the fore-arc basin in the CMB, and the east-verging folding is due to slip up on the slope of the retro-wedge. The dextral strike-slip movement of the Kabaw Fault is displayed by the shifting of mud volcanoes in the Pyay to Kalaywa region and the two-phase folding and deformation within the Chindwin sub-basin and the Minbu-Salin sub-basin. The present study proves not only the Kabaw Fault as an east-dipping reverse fault with structural evidence, but also reveals the double-sided wedge system of the IMR accretionary prism.