Geophysical processes and biosphere: article

Аnnotation: 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 were 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 NER, the velocity section is represented by a reduced transitional crust, 13 km thick. 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 was built, which made it possible to identify the morphological features of its structure. A seismostratigraphic analysis of the structure of the sedimentary cover developed: a) on horst blocks grouped at the foot of the western slope of the NER, b) on the crest of the NER, c) in the adjacent part of the Central Basin. It was established that in the Late Cretaceous–Paleogene, the Bengal sector of the NER 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».