The Andaman Backarc Basin is believed to have been formed by the present episode of seafloor spreading in the Andaman Sea, separating the Alcock Rise in the north (Burmese Plate) and the Sewell Rise in the south (Sunda Plate). The geophysical investigations carried out so far in this basin provided detailed information on the morphotectonic signatures of its central sector, however, such understanding of the eastern sector is still awaited. Those studies also inferred continual seafloor spreading in the Andaman Backarc Basin starting from 4.0 Ma, however, some of the subsequent studies, based on deep water sedimentation, postulated an episodic seafloor spreading responsible for the formation of the Andaman Backarc Basin. To address these problems, we revisited the morphotectonic signatures and evolution of the Andaman Backarc Basin using a new set of multibeam bathymetry and magnetic data from the central and eastern sectors of the Andaman Backarc Basin, complemented by the existing geophysical data from the central sector. Our updated bathymetry map of the newly surveyed northernmost segment (referred as Segment D), is characterized by the presence of a well-defined rift valley, with an along-axis gentle dip from the east to the west. The segment D is also characterized by the absence of significant magnetic anomalies, as in the case of segment C, corroborating the concept of replacement of layer 2A by a sill-sediment-metasedimentary layer, in a sedimented spreading centre. Further, our revisit to the magnetic anomaly identifications suggests that the magnetic anomalies over the segment B of the Andaman Backarc Basin can reasonably be explained in terms of continual seafloor spreading from chron C3An.1ny (5.894 Ma) till the present (0.0 Ma). Based on these identifications of magnetic anomalies and the plate tectonic reconstructions, we revise the age of opening of the Andaman Backarc Basin from 4.0 Ma to ~5.9 Ma.

安达曼弧后盆地被认为是由目前安达曼海海底扩张形成的，将北部的阿尔科克海隆（缅甸板块）和南部的休厄尔海隆（巽他板块）分开。迄今为止，在该盆地进行的地球物理调查提供了有关其中部地区形态构造特征的详细信息，然而，对东部地区的这种认识仍有待于了解。这些研究还推断，从 4.0 Ma 开始，安达曼弧后盆地中的海底持续扩张，然而，一些基于深水沉积的后续研究假设，是导致安达曼弧后盆地形成的偶发性海底扩张。为了解决这些问题，我们使用来自安达曼后弧盆地中部和东部地区的一组新的多波束测深和磁数据重新审视了安达曼后弧盆地的形态构造特征和演化，并辅以来自中部地区的现有地球物理数据。我们最新勘测的最北段（称为段 D）的更新测深图的特点是存在一个明确的裂谷，从东到西沿轴线呈平缓倾角。段 D 的特征还在于没有明显的磁异常，如在段 C 的情况下，证实了在沉积扩张中心用基岩-沉积-变质沉积层替代 2A 层的概念。更远，我们对磁异常识别的重新审视表明，安达曼弧后盆地 B 段的磁异常可以从 chron C3An.1ny (5.894 Ma) 到现在 (0.0 Ma) 的连续海底扩张方面合理地解释。基于这些磁异常识别和板块构造重建，我们将安达曼弧后盆地的开放年龄从4.0 Ma修正为~5.9 Ma。