Abstract
AbstractDeccan trap thickness is an important parameter in understanding the eruption process of flood basalts (65 My). A magnetotelluric study was carried out in Deccan Volcanic Province (DVP) of the Indian Peninsular shield during 1998–1999. Modeling results clearly revealed variations both in the thickness of the Deccan traps and in their resistivity from the west coast to the eastern boundary of DVP. The thickness of the traps in DVP decreases from about 1.8 km in the west to a few hundred meters (approx. 400 m) towards the east. The traps also exhibit considerable variation in resistivity, with higher resistivities (approx. 150–200 ohm-m) in the western half and lower resistivities (approx. 50–100 ohm-m) in the eastern half of DVP. Two significant fissure/fracture zones have been detected in DVP; these may have acted as conduits for the outpouring of Deccan lavas in addition to the primary structures along the west coast and the Narmada-Son lineament (NSL) zones.
Highlights
Deccan traps, which form a vast flood basalt province in the Indian peninsula, are generally believed to have erupted at the close of the Cretaceous, some 65 (±4) mya when the Indian continent—following its separation from Madagascar—moved over the Reunion hotspot during its northward journey (Morgan, 1981; Duncan and Pyle, 1988; Allegre et al, 1999)
The Deccan traps occupy an area of nearly 500,000 km2, which makes this formation the second most extensive geological formation in Peninsular India, only to the Archean igneous and metamorphic complex
There have been a few attempts to estimate the thickness of the traps using conventional geophysical methods, such as gravity, magnetics and seismics (Negi et al, 1983; Tiwari et al, 2001; Kaila et al, 1981a, b). While such studies have a number of limitations in terms of delineating the configuration of the trap thicknesses and the nature of the subtrappean lithology, magnetotellurics has been shown to be very effective in investigating trap-covered areas (Sarma et al, 1998; Gokarn et al, 1992; Patro et al, 2005a, b)
Summary
Deccan traps, which form a vast flood basalt province in the Indian peninsula, are generally believed to have erupted at the close of the Cretaceous, some 65 (±4) mya when the Indian continent—following its separation from Madagascar—moved over the Reunion hotspot during its northward journey (Morgan, 1981; Duncan and Pyle, 1988; Allegre et al, 1999). There have been a few attempts to estimate the thickness of the traps using conventional geophysical methods, such as gravity, magnetics and seismics (Negi et al, 1983; Tiwari et al, 2001; Kaila et al, 1981a, b) While such studies have a number of limitations in terms of delineating the configuration of the trap thicknesses and the nature of the subtrappean lithology, magnetotellurics has been shown to be very effective in investigating trap-covered areas (Sarma et al, 1998; Gokarn et al, 1992; Patro et al, 2005a, b). We interpret the results of an analysis of wide-band (0.001–1000 s) MT data obtained from a total of 139 MT sounding sites on the Deccan Plateau that were situated along five different traverses cutting across some of the major gravity ‘highs’ and ‘lows’ in order to examine the thickness configuration and subtrappean structure.
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