Detection of Slump Structures in the Intraplate Deformation Area (Central Basin, Indian Ocean)

摘要

The well-known region of intraplate activity in the northeastern Indian Ocean (IO) [1, 2] partly includes the Bengal Fan (BF) in the Central Basin. The neotec-tonic activity is distinctly manifested in Neogene-Qua-ternary fold-fault structures in the basement and sedimentary cover of the basin. These remarkable shear structures are attributed to the collision of Hindustan and Eurasia and the subsequent uplift of the Himalayas. The inclination of reflectors in the primarily horizontal-bedded BF sediments is considered a secondary process related to intraplate deformations. In [8], the stratified BF sequence is separated by three unconformities-A (7-8 Ma, late Miocene), AA (3-4 Ma, early Pliocene), and B (0.8 Ma, late Pleistocene)-that correspond to three intraplate deformation phases (Fig. 1). However, the seismic profiles presented in [8] do not provide sufficient grounds for correlating them. Interpretations of them (except for unconformity A) and spatiotemporal distribution of tectonic activity in the Central Basin are ambiguous. It has been repeatedly noted that correlating reflectors in neighboring blocks of the BF sequence that are separated by faults is difficult and ambiguous, particularly in intensely deformed areas.