The Nature and Evolution of the Ninetyeast Ridge: A Key Tectonic and Magmatic Feature of the East Indian Ocean

New Insights into the Seamount Structure of the Northern Part of the Ninetyeast Ridge (Indian Ocean) through the Integrated Analysis of Geophysical Data

“…The most well-defined are the trends of the SW-NE strike, which are evident in the topography of the seamount and the adjacent section of the NER. These are consistent with the strike-slip structures (Figure 1a) that define the specific echeloned morphology of the northern segment of the ridge [13,23]. The nature and timing of the formation of these SW-NE strike-slip faults in the NER, which possibly continue into the adjacent troughs, are still debatable and are not discussed in this paper.…”

“…The same SSW-NNE strike-slip faults are also observed deeper in the form of spurs in the lower parts of the slopes. It should be noted that SW-NE and SE-NW strike-slip faults in the northern segment of the NER were previously identified on the detailed survey polygons of the R/V Marine Geophysicist and Pegasus (1982,1983) and Roger Revelle (2007) [13,20,21]. Both trends are clearly evident in the northern segment of the NER on the General Bathymetric Chart of the Oceans (GEBCO) map [26].…”

“…In the Indian Ocean, there are many seamounts of different ages, the formation of which cannot be explained by a single mechanism [2][3][4][5][6][7]. The central structure of the Eastern Indian Ocean is the Ninetyeast Ridge (NER), formed according to the "hot spot trace" hypothesis as a result of the Indian Plate drift over the Kerguelen mantle plume [8][9][10][11][12][13]. This is evidenced by the results of seven DSDP and ODP deep-water drilling sites due to a regular increase in the age of the basalts along the ridge from south to north from approximately 40 to 80 million years [14,15].…”

“…This is evidenced by the results of seven DSDP and ODP deep-water drilling sites due to a regular increase in the age of the basalts along the ridge from south to north from approximately 40 to 80 million years [14,15]. In the existing evolutionary models regarding the nature of the NER, there is generally some disagreement, with the exception of its ancient northern segment, the formation of which is unanimously attributed to intraplate volcanism in the Indian Plate away from the spreading ridge [8,9,13,16,17].…”

“…Ideas about the structure and nature of the NER are largely based on the results obtained in regular cruises of the Shirshov Institute of Oceanology (IO RAS) in the 70-80 years of the last century [13,23,24]. In winter 2017, after a long break, cruise #42 of the R/V Akademik Boris Petrov resumed geological and geophysical work in the Indian Ocean [25].…”