Nature of the Crust in the Southern Part of the Bay of Bengal and the Adjacent Part of the Central Basin (Indian Ocean)

• Published in: Izvestiya. Atmospheric and oceanic physics 2022-12, Vol.58 (10), p.1289-1311
• Main Authors: Illarionov, V. K., Ganzha, O. Yu, Ilyinsky, D. A., Burmin, V. Yu, Boyko, A. N., Roginskiy, K. A., Borisova, A. Yu
• Format: Article
• Language: English
• Subjects: Acoustic mapping; Alliances; Climatology; Cretaceous; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Miocene; Oceans; Paleogene; Pliocene; Seismic studies; Seismology; Tectonics; Thickness; Tracers; Velocity; Velocity sections
• ISSN: 0001-4338; 1555-628X
• DOI: 10.1134/S0001433822100048

Based on the data of deep seismic sounding, which were obtained in 2003 on the R/V Mezen in the Bay of Bengal, two velocity sections have been constructed that characterize the structure of the crust in its southern part. Seismic studies have shown that, in the Bengal sector of the East Indian Ridge (EIR), a subcontinental type of crust is developed, the thickness of which reaches 19.5 km. At the western foot of the EIR, the velocity section is represented by a reduced transitional crust 13 km in thickness. Using the NGDS digitized database of the thickness of the sedimentary cover in the Indian Ocean, which is freely available on the Internet, a map of the depths of the acoustic basement is built which makes it possible to identify the morphological features of its structure. A seismostratigraphic analysis is carried out of the structure of the sedimentary cover that has developed (a) on horst blocks grouped at the foot of the western slope of the EIR, (b) on the crest of the EIR, and (c) in the adjacent part of the Central Basin. It is established that, in the Late Cretaceous–Paleogene, the Bengal sector of the EIR and horst blocks represented a single platform structure. In the latest phase of tectonic activation, which manifested itself in the late Miocene–Pliocene, the platform was divided into horst blocks, which experienced differentiated subsidence. It has been established that horst blocks play the main role in the structure of Ridge 85°. This ridge is not structurally unrelated to the Afanasy Nikitin Rise and, by its nature, is not a “tracer ridge.”