Deccan Trap

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Join this channel to get access to perks: • / @quartz-academy • QUARTZ - Academy • Exclusive coaching Institute for Earth Sciences • Mr. Nikhil V. Sherekar Sir (Founder of Quartz - Academy) • M.Sc Geology (University of Pune) • NET-CSIR (AIR-99) • UGC-JRF (AIR-28) • SET • PET • COC • contact no - 8390377801 • https://chat.whatsapp.com/D1ojc8BncJF... • https://t.me/quartzecies • / nikhil.shere. . • / mikiback4u • email - [email protected] • The term trap has been used in geology since 1785–95 for rock formations. It is derived from the Swedish word for stairs (trapp , trappa) and refers to the step-like hills forming the landscape of the region. • The plateau: also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A plateau is an elevated land. It is a flat-topped table standing above the surrounding area. A plateau may have one or more sides with steep slopes. • LIP – Large Igneous provinces. (Province = Area / Region) • DVP - The Deccan Volcanic Province is one of the Earth’s giant continental flood basalts and has a total exposed area of about half a million square kilometers in Maharashtra, Madhya Pradesh, Gujrat and some part of Andhra Pradesh. Deccan trap has maximum thickness 3400m in western ghat and its thickness goes decrease toward east side. At Amrakantat on east its thickness is just 160m. Geographical distribution is between latitudes 16° - 24° N and longitudes 70° - 77° E • Age – 65 Ma late cretaceous, it begins to form at this age and it take almost 1Ma to complete the episode of fissure type volcanic eruption. The release of volcanic gases, particularly sulphur dioxide, during the formation of the traps contributed to climate change. Data points to an average drop in temperature of 2°C in this period. • Source – from lower mantle - outer core boundary, Association – Reunion mantle plume. Less viscous lava with massive, compact and vesicular basalt. 95% - Tholeiitic basalt, 5 % - Alkali basalt, Nephelinite, Carbonatite and lamprophyre. • Deccan basalts are nearly horizontal over vast areas, except where they are tectonically disturbed as in the West Coast, Western Ghats, Khambhat graben and SonNarmada (SONATA) rift. The lavas are thinnest in the east But at some places it gently dip by 10°. Total 48 flows are recorded in deccan trap in which 11 flows can identified in SW of DVP on the basis of major elements and Trace elements like – Sr, Nd, Pb isotopes • Intertrappean beds – • The Intertrappean Beds are a Late Cretaceous geologic formation in India. Indeterminate theropod and pterosaur remains have been recovered from the formation, as well as dinosaur eggs. Before the advent of radiometric dating, the age of the Deccan Trap was invariably fixed based on the age of the youngest underlying fossiliferous formations, mostly of Cretaceous age, designated as Infra-trappean beds, and ages obtained for the youngest Intertrappean beds. It was soon noted that there are such fossiliferous horizons in different places at different levels in different sections of the Deccan Traps and they may be infra-, inter- or supra-trappean beds. The same horizon may be infra-trappean in one place and intertrappean in another. At short intervals traps are separated by sedimentary beds of small vertical as well as horizontal extent of lacustrine or fluviatile deposition on the irregular surface During eruptive intervals, Which are formed under water. These sedimentary beds are called as Infratrappeans or Intertrappean beds. • Stratigraphy - • ▪ Wai - Simple lava flow with small phenocryst of plagioclase + pyroxene + olivine • ▪ Lonavala – Bushe compound lava flow • Khandala Simple lava flow • ▪ Kalsubai - Amygdaloidal compound flow with high MgO content, Picritic basalt and picrite with • phenocryst of Olivine + CPx • ▪ The lower trap is exposed in Madhya Pradesh and toward the east of deccan trap with 160m thickness and they contain no of intertrappean beds. In the lower trap the ash beds are rare. • ▪ The middle trap occurs in central India and malwa region with 1300m thick lavaflows and some ash beds. In this part, the intertrappean beds are almost absent. • ▪ The upper trap is exposed in west part of the peninsula, particularly in Mumbai and Kathiawar with • 500m thickness and are associated with intertrappean and ash beds. • What is Flood basalts ? • Flood basalts, also known as large igneous provinces (LIP), are the product of massive outpourings of low viscosity basaltic lava that envelop hundreds of thousands of square kilometres. Flood basalts form above mantle hotspots in the marine setting as oceanic flood plateaus or on land as continental flood plateaus. Oceanic flood basalts include the Ontong Plateau deposits in the western Pacific Ocean basin and the Kerguelen Plateau in the Indian Ocean. Spectacular examples of continental flood basalts include India’s Deccan Traps, the Siberian flood basalts,

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