Deccan Continental Basalt

The ~65-million-year-old Deccan Continental Basalt of India covers an area of 5 x 105 km2. The basalt flows are generally 10�50 m thick and tabular in form, dipping at <0�5� in various directions. The thickness of the lava pile is >2000 m in the Western Ghats area between Nasik and the southern edge of the Deccan Traps, and exceeds 1000 m in parts of the eastern Deccan along the Tapti and Narmada grabens.The large Deccan lava flows were fed by regional dykes. In some southeastern and far-northern regions distant from both the Western Ghats and the eastern Deccan areas, the thickness of the lava pile is <100 m. The main eruption of the Deccan basalts took place in a geologically short period of time (probably <1 m.y.) at 66 Ma indicating high eruption rates of 1 km3 per annum. Plate tectonic reconstructions show that the Deccan eruptions took place when the Indian continent passed over a plume situated beneath the present site of R�union. The Deccan basalts are largely microporphyritic with phenocrysts of plagioclase, subordinate augite and rare olivine. Phenocrysts are set in a groundmass consisting of plagioclase, augite, rare Fe�Ti oxide minerals and glass. Some basalts contain glomero-porphyritic aggregates of augite and plagioclase crystals, occasionally in association with olivine.

New chemostratigraphical data permit mapping of the SE Deccan. These data strengthen the likelihood that the Rajahmundry Traps of eastern India were originally fed by long-distance flows, and are an extension of the Main Deccan Volcanic Province.