High-resolution intrabasinal to inter-regional geodynamic chronicle during the span of the intra-permian–intra-paleogene mega-sequence in and around India on the GTM

Abstract

This chapter chronicles the geodynamic evolution of India and associated dismemberment history of the Gondwanaland (Figs. 7.43 and 7.44). The narration is through the succession of geological events and their interdisciplinary manifestations that are uniquely punctuated with the first- and second-order physically feelable and visually observable sequence surfaces. These surfaces are considered products of the causative tectonic/igneous events. In the process, the entire ~540 my long Phanerozoic history in general and the intra-Permian–intra-Paleogene Indian/GTM mega-sequence geological record in particular inclusive of the surface and offshore wells is, intrabasinally to interregionally, correlated, integrated and interwoven at a distinctly improved average resolution of ~3.5 my involving a succession of ~40 odd second-order sequence surfaces. Within the Kachchh basin, the precision tell-tale has been realized at yet finer resolution of ~400 ky or multiples with the help of a series of graphics. The mega-sequence began with Panjal and coeval igneous events that are particularly manifested in the north sector. Its differentiation into three first-order sequences (Spitiian, Kachchhian and Dravidian) is punctuated by major igneous events in the west near the ~183 ma Pliensbachian/Toarcian boundary in the Kachchh and Saurashtra wells (coeval to Karoo volcanism), and later in the east near ~the 126 ma Barremian/Aptian boundary first-order SB Rajmahal and coeval igneous events. Major volcanic events are evidenced in the east near the ~243 ma first-order Middle Triassic MFS in Papua New Guinea, and again at the first-order intra-Jurassic ~159 ma MFS with spreading away of the Argo block from Greater India at the Indo-Australian divergent margin. Madagascar separated from India during the ~94 to ~84 ma span. Both the start and end of the span mark significant sequence surfaces. The initial impingement of the drifting India with the Kohistan–Ladakh oceanic island arc is interpreted around the ~51–50 ma late Early Eocene Late Cuisian planktonic foram P8 Zone sequence surface, well after the intra-Paleocene basal/intra P3 Zone SB ~60–59 ma closure of the mega-sequence. The stratigraphic gaps in the Indian record inclusive of the break-up unconformities are better resolved and differentiated as subaerial and submarine, and also are precisely ranged through the succession of sequence surfaces. The succession of the ~40 highly time-precised sequence surfaces, in a process-response relationship, has, precisely, dated as many rift, igneous, eustatic, anoxic, T/R events and the multifaceted collage of other geological phenomena and expressions. The Mesozoic litho- and biostratigraphic units in outcrops and wells, marine and non-marine, guide fossil bearing or devoid, carbonates or clastics, shallow or deep of the Indian basins across the length and breadth of India have been precisely age-constrained and mutually correlated through the succession of sequence surfaces. Major evolutionary landmarks of organic evolution are also speculatively age-constrained, since conceptually influenced by tectonic and magmatic events with or without igneous expressions. The principal energy resources of India, hydrocarbon, coal, and atomic minerals, are temporally and spatially better constrained, and understood through the succession of the second-order sequence surfaces. © Springer Science+Business Media Singapore 2017.