Tectonics of the Ninety-East Ridge

O. V. Levchenko, I. M. Sborshchikov, and Yu. G. Marinova

Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS), pr. Nakhimovski 36, Moscow, 117997 Russia

e-mail: olevses@gmail.com, isborsh@yandex.ru, marinova.ocean@gmail.com

Received July 9, 2012

Abstract—New multibeam bathymetry data and multichannel seismic profiles over 7 detailed survey sites col-
lected during cruise no. KNOXRR06 of the R/V Rodger Revelle in 2007 fundamentally expanded the concepts
about the structure of the sedimentary cover of the Ninety-East Ridge, which were based on the results of pre-
vious studies. They allow making a step forward in interpreting the nature of the unconformities and deforma-
tions. The deformation pattern of the sedimentary cover suggests three stages of tectonic activity over the ridge
during the Paleocene, Eocene, and Late Miocene. As suggested by the high present-day seismicity, the last stage
might continue to the present time. In addition, indirect criteria indicate young intraplate volcanism at the last
stage. New data is reviewed in the context of two models of the ridge formation. The first model follows a well-
known concept of the ridge representing a trace of the Kerguelen hotspot. The second one relates large outflows
of basalts to the development of a giant fracture under conditions of global extension, which continued later
during the sedimentary cover formation. Additional integrated geological and geophysical studies are required
for understanding the nature of this unique feature.

10.1134/S0001437014020143

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