The book contains fourteen chapters and covers the investigations carried out by the scientists of both the sides. The Indian institutions involved are: Indian Institute of Astrophysics, Bangalore; C-MMACS (CSIR), Bangalore; National Institute of Oceanography (NIO), Goa; National Geophysical Research Institute (NGRI), Hyderabad and Regional Centre (NIO), 176, Lawson’s Bay, Vishakhapatnam.

The Russian institutions involved are: Moscow State University, Moscow; Institute of Oceanology, Russian Academy of Sciences (RAS), Moscow; South Branch of Institute of Oceanology, RAS, Golendjik; Institute of Geophysics, Ukranian; Academy of Sciences (UAS), Kiev; and Atlantic Branch of Institute of Oceanology, RAS, Kaliningrad. This project was obviously funded by the Department of Science and Technology (DST), Government of India and Academy of Sciences of Russia. The funds for publishing the monograph was made available by DST, NIO and NGRI.

Chapter 1 covers mainly the previous results and the researches carried out on Indian Ocean Lithosphere and a review of geophysical and geological results. Notable amongst them are the data generated by International Indian Ocean Expedition, Lamont–Doherty Geological Observatory, USA; and Scripps Institution of Oceanography, USA.

In Chapter 2, the cruises of Research Vessels (R/V) Prof. Dmitry Mendeleev, Prof. Shtokman and Academic Mstistav Keldysh have been covered. The outcome is classic discoveries in the Central part of Indian oceans: 1. Afanasy–
Nikitin Seamount formed during late Cretaceous along the passive margin. 2. Oceanic Island Basalts (OIB) of the seamounts belong to hot-spot type intraplate alkaline magnetism. Seamounts forming volcanic islands were eroded during Paleocene. 3. Wave erosion and subsidence together with lithospheric plate volcano was transferred to guyot-type seamounts during Eocene. 4. Intraplate deformation is explained by the neotectonic deformation and extensional features along the spreading zone.

In Chapter 3, new bathymetric study has provided hummocky Seafloor with E–W trending elongated hills of seamounts (20 m ht – 45 km width) and deep out valleys with turbidite channels. According to Chapter 4, an estimated 4.4 cm/year rate of seafloor spreading during early Cenozoic is responsible for northward drift of Indian plate.

Chapter 5 describes that the gravity anomaly associated with topographic high could be explained with models of thinned crust of uplifted blocks. Thus the upliftment of basement wharping or sites of deformed basement are result of intraplate deformation. Convention in upper mantle causes mobility of the Indian plate. A large dimensional deformation and its correlation with global gravity minimum appears to be the near surface manifestation of deep processes in the mantle.

The average heatflow (Chapter 6) observed in the Indian ocean area is higher by 12 m W m^–2 than the standard value for 70 Ma age oceanic crust. This would be attributed to the result of dissipation of mechanical energy considering the two level plate tectonic model (Lobkovsky, 1988) with exothermal reaction of semiductile serpentinite creeps of subcrust lithosphere mantle into the lower crust.

The oceanic crust and sedimentary cover near the Afanasy Nikitin Seamount seem to have been affected by the continuous deformation during Miocene time, while the central Indian intraplate deformation took place only in short time since late Miocene (~ 7.5 Ma). This could be explained by pronounced lithostratigraphic heterogeneity caused by Afanasy Nikitin Seamount. Pulse of tectonic activity is also marked at Miocene–Pliocene boundary unconformity at 3.5 Ma by a mud turbidite flow. Thus two prominent unconformities are defined: Late Miocene (7 Ma), and upper erosion unconformity glacial and non-glacial sea level variation during upper Pliestocene 800 Ma (Chapter 7).

The seismic parameters revealed a three-layered crustal structure. Average sediment thickness is estimated to be 0.5 km. There is further scope to conduct seismic tomographic and detail results (Chapter 8).

In the Bay of Bengal almost all the intraplate earthquakes with known focal mechanism are characterized by strike-
slip mechanism combined with thrust faulting. Ocean bottom seismological observations can enhance the detail and accuracy of regional seismicity. The ocean bottom seismometers seismic refraction hints at variation in thickness of crust and blocky mosaic structure bottom seismological observations in northern C/B area revealed unusual high microseismicity more than 100 weak earthquakes in ten days with epicentres located predominantly inside to E–W trending blocky mosaic structure. This may be due to episodic intraplate deformation (Chapter 9).

The accumulated basin sediments are characterized by denudation of Sri Lanka, Indian Peninsula and the Himalaya. Sediments consist of noncarbonate siliceous oozes: radiolarian-diatom, nannoplanktons, etc. Cu and Ni-rich manganese nodules are very common along with smectite and barite. Authigenic minerals are quartz, illite, feldspars, kaolinite, palygorskite. The sediments are accumulated below Carbonate Compensation Depth (CCD) and the sedimentation rate is about
3–5 m/my and the mass accumulation rate is 0.5–1.0 g/cm²/ky. Early to late Oligocene turbidities mark the beginning of fast sedimentation derived from Himalaya. Polycyclic Aromatic Hydrocarbons (PAH) of the organic matter structure of the sediments are 26 to 180 µg/g (of dry sediments). They are widespread and typical of hydrothermal solutions and volcanic emanations. PAH can be used as important indicator of hydrothermal sources. These organic matters could be the source of rich gas hydrate for future energy resources. Seamounts revealed the migration from high latitude subtropical and to present position. Seamount-morphology and structure were constantly modified by neotectonic activity, volcanism and hydrothermal activity due to intraplate deformation (Chapter 10).

Oceanic Island Basalts (OIB) collected by submersible located near the transform-faults or at their intersection with ridge-axis basement within the intraplate deformation are composed of magnetite of upper Cretaceous age (Chapter 11).

Lobkovksy’s (1988) concept of two-level plate tectonics explaining the tectonic intraplate deformation in Central Indian Ocean Basin is connected to lithospheric deformation below the
Himalayan-Subduction zone. The viscous lower crust material, viz. serpentinites gets injected into the vicinity of Suture-zone of Himalaya, causing thickening of the lower crust. However, this model requires further refinement with the new geophysical data obtained by INDEPTH and other scientific agencies working in Himalayan-Tibetan region (Chapter 12).

The new tectonic model has only basement deformation whereas the overlying sedimentary cover remains unaffected (Chapter 13). The continuity of seamount with OIB type magnetism and its alignment with Ninety-east Ridge and its continuity to Rajmahal traps in Indian peninsula should open a

new concept of hot-spot migration along the N–S alignment with the flight of Indian plate resulting into collision with Asian plate and the growth of Himalayan mountain.

The book is highly recommended for researchers and students with its treasure of acquired data by the joint Indian and Russian collaborative Programme. It can be easily purchased by a large number of scientists as well as librarians. There was enough scope to improve the quality of diagrams and figures, particularly of geophysical seismic

profiles in original. The team should have taken pains to develop computer simulation model and to produce them as coloured diagrams. Overall, however, the entire Indian and Russian team has to be congratulated.