As someone who has worked on all continents, and extensively across South, Southeast and eastern Asia, I can attest to the singular importance of extensive and detailed books that summarize the geology of specific regions. A source book with information on all topics of geological importance for a region is vitally important to anyone who initiates geological study in a new area. One keeps returning to such books over the years to refresh one’s memory and find new nuggets of information. Tectonics of the Indian Subcontinent by Jain, Banerjee and Kale is just such a book. Remarkably wide-ranging, complete and up to date, this book is a must for any geologist working in the Indian Subcontinent.
The authors begin by defining the Indian Subcontinent to include parts or all of India, Pakistan, Bangladesh, Sri Lanka and Myanmar. The subcontinent is a region of remarkably complex geography and geology. The book starts with a description of the various geographical elements, including mountain belts, plains and drainage systems, as well as the underlying geology. The history of the subcontinent is written in rocks from the coastal plains, to the Cenozoic deposits of the Indus–Ganga–Brahmaputra Plain, to the high peaks of the Himalaya. The book provides material on a wide range of geological aspects of all the regions covered, including such topics as regional geology, tectonics, structure, volcanism, plutonism, sedimentation, metamorphism and geochronology. The authors demonstrate an excellent grasp of the literature and provide more than background information when they discuss various issues of contention regarding the interpretations of the geology presented.
After the introductory chapter, the geology of each of the largely Archaean cratonic masses of the core of the Indian Subcontinent is discussed, with emphasis on their geological framework and tectonic history (chapter 2). Chapter 3 presents similar information for Sri Lanka, an area that is much less generally known than India. Chapter 4 provides a wealth of information on each of the Proterozoic mobile belts that separate the older cratonic blocks.
Chapter 5 is devoted to many relatively undeformed Proterozoic sedimentary basins and sub-basins. These basins contain variably thick stratigraphic successions with a wide variety of lithofacies. Stratigraphic and geochronological data are used to evaluate a wide range of possible correlation schemes between these basins. The number of basins is impressive (n = 15), and many of them are likely unknown to geologists, including many who have worked extensively in India.
Chapter 6 discusses the tectonics of the various regions of the subcontinent, starting with the Himalaya and then the Indus–Ganga–Brahmaputra Plain, the latter generally known as the foreland basin region of the Himalayan Range. The strata in this region, which contain a record of the erosion of the fold-and-thrust belt of the Himalaya that resulted from the collision of India with Asia, are discussed in detail. This is followed by a discussion of the rocks of the Lesser Himalaya and then the Himalayan Metamorphic Belt, the latter including a variety of high-grade metamorphic rocks that make up klippen and extensive areas at the core of the Himalaya. In the same chapter, the authors tackle the Palaeozoic and Mesozoic sedimentary successions of the Tethyan Himalaya, with a long discussion of the large-scale basin configuration of the northern margin of the Indian plate. Of particular importance are the relationships between the three northern lithotectonic zones of the Himalaya, the Lesser, Greater and Tethyan Himalaya. The relationships are discussed with emphasis on the provenance of sediment and published detrital zircon U–Pb geochronological data. The authors then discuss the tectonic boundaries (mostly thrusts) between these zones, and associated folds. Chapter 6 also contains a full discussion of the history of magmatism, spanning the Palaeoproterozoic to the Cenozoic. The chapter ends with a discussion of the various models of large-scale tectonics of the Himalaya, including the timing of collision between India and Asia. If the authors had chosen to publish this 130-page chapter as a separate book, one would have been impressed with the results, as evidenced by its 23-page bibliography alone!
Chapters 7–10 cover disparate topics and are a wonderful ending to a wide-ranging book. Chapter 7 on the Trans-Himalayan and Karakoram Ranges addresses the northern region of the Himalaya, particularly the Indus–Tsangpo Suture Zone (ITSZ), Shyok and Karakoram Suture Zones, and associated high-grade metamorphic rocks, granitic intrusions and ophiolite nappes. The timing of the India–Asia collision is discussed at the end of the chapter. Chapter 8 on the Deccan Traps is a remarkably complete and extensive summary of what is known about this volcanic province, with ten pages of references. Chapter 9 on the Western Margin of India includes the Western Coastal Belt and an offshore transect from the shelf to the abyssal plain. Chapter 10 on the geology and tectonics of Bangladesh, including the Bengal Basin and the Ganga–Brahmaputra delta, among other topics, puts the icing on the cake.
With a book of this type, one could always pick a nit about whether one topic or the other was adequately discussed, or if some authors were favoured or given short shrift. That is certainly the case here, but that is unavoidable in a book of this type, which covers such a range of topics. That said, writing such a book requires a wealth of experience and a deep background in disparate fields. One must admire the authors for tackling an enormous task and having the perspicacity to complete it. Bravo to the authors for a job well done.
