Language: English
The first edition of this book was sold out within about a decade of its publication in the year 2001. A recently revised edition of the book is now available. Geological investigations in northeastern India had a brilliant start when the pioneers from the Geological Survey of India and petroleum exploration agencies braved the adverse field conditions and laid the foundation for further geological studies. The author, working on those foundations has collected basic field data from several sectors, analysed those for stratigraphic and tectonic classifications and integrated them with the contributions from others to build a database which he incorporated in this book.
Northeastern India presents a collage of six dissimilar tectonic provinces, some of which extend into the adjoining territories of Myanmar, or Tibet or Bangladesh, or continue beyond the shorelines into the Bay of Bengal region. Their geological evolution has followed divergent trends, covering variable time spans. The first five chapters of the book elaborately deal with their diversity and complexity. The provinces are – the eastern Himalayan collision belt, the Mishmi block, the Indo-Myanmar mobile belt, the Meghalaya plateau, the Bengal basin, and the Brahmaputra valley. The introductory chapter briefly discusses the scheme of classification and geographical distribution of the provinces. Moreover, the distribution is shown on a map placed in a pouch at the inner back cover of the book.
The active plate margin, the Precambrian shield element exposed in the Meghalaya plateau, the enigmatic Garo-Rajmahal gap, the peri-cratonic Bengal basin, the wide zones of foreland molasse, the ophiolite melange – all contribute to the diversity, which is discussed in the first five chapters of the book. The northeast is arguably the most dynamic sector of the present day crust. The ongoing tectonic movements here frequently trigger seismic events of high magnitude. The last three chapters of the book are focused on defining the source and manifestations of the tectonic forces that are presently active in this part of the crust. Chapter 8 of the book combines the results of seismotectonic analysis with paleoseismic studies and microearthquake surveys. A large number of fault plane solution data taken from various sources have been analysed to arrive at meaningful conclusions on local orientation of the stress axes. The last three chapters together present a novel approach which opens up possibilities of further studies on this line.