Active deformation of the Central Myanmar Forearc Basin: Insight from post-Pleistocene inversion of the Pyay Fault

• Main Authors: Lin Thu Aung, Kyaw Zin Oo, Kyaw Myo Win, Gregory F. Moore, Soe Thura Tun, Win Naing
• Format: Article
• Language: English
• Published: Elsevier 2020-12-01
• Series: Journal of Asian Earth Sciences: X
• Subjects: Central Myanmar Forearc Basin; Pyay Fault; High-angle thrust fault; Growth strata; Terrace deposits; post-Pleistocene inversion
• Online Access: http://www.sciencedirect.com/science/article/pii/S259005602030013X

Pyay sub-basin is located in the southern part of the Central Myanmar Forearc Basin, an elongate belt of en-echelon folds and thrust faults formed as a result of the hyper-oblique convergence of the India and Asia plates. Limited neotectonic studies suggest that the Pyay Fault is a major Pliocene inverted structure that trapped the hydrocarbons in Pyay sub-basin, where only sparse field-based observations are available to address the nature of very recent neotectonic processes. This study focuses on structural deformation related to active inversion of the Pyay Fault using field-based geological observations and interpretations of industrial seismic data. We map the ∼105 km long Pyay Fault, an east- dipping high-angle reverse fault with a significant dextral strike-slip component. The fault underlies the western limb of the major NNW-SSE- striking anticlinal ridge that forms the western margin of Pyay sub- basin. Growth strata within the Pliocene-Pleistocene Irrawaddy Formation, imaged in the shallow part (<1 km) of 2D seismic profiles, reflects the deposition of Pliocene-Pleistocene sediments synchronously with the inversion of the underlying Pyay Fault. In addition, uplifted fluvial terraces of the Ayeyarwady River on the hanging wall of Pyay Fault reflect the post-Pleistocene inversion of the Pyay sub-basin. This study suggests that the Pyay Fault is a prime example of active deformation of the Central Myanmar Forearc Basin which plays an important role in the basin evolution and an earthquake source potential of the Myanmar territory.