Deccan traps
Deccan traps
Deccan Igneous province is one of LIPs (Large Igneous Provinces). It lies in Maharashtra and parts of Gujrat and Madhya Pradesh. Its thickness decreases towards east. They are believed to be a possible reason for the extinction of Dinosaurs.
Characteristics
- Lavaflows are of basaltic nature. Age is upper cretaceous to paleocene. K-Ar dating method was used to determine the age.
- Source was Reunion mantle plume which is now lies beneath Reunion island in Indian ocean. The hotspot is believed to have been active for over 65 million years.
- Lower parts have reversed polarity and upper parts exhibit normal polarity.
- Lavaflows are mostly horizontal in attitude. This is evidence of quiet volcanism.
- These lavas were erupted sub-aerially by fissures and veins.
- In Gujrat, they lies on the Jurassic rocks of Kutch area while in Narmada valley they occurs on the Bagh beds.
Bagh beds
These beds are of marine origin and represents trangression facies of cretaceous age in Narmada valley. They occurs as inliers surrounded by younger Deccan traps. These beds are rich in fossils of ammonites, gastropods and echinoids.
Petrology
The majority (about 95%) of deccan traps are of tholeiitic basalts. Mantle xenoliths and other rocks have been reported from Kutch area. Pyroxenes and plagioclase are common. Olivine is rare and restricted to phenocrysts. Petrochemical studies showed higher MgO content.
Stratigraphy
Deccan traps are divided into 3 subgroups.
Lower parts have intertrappean beds (Lameta formation). Middle traps lacks intertrappean beds while upper beds have both intertrappean and ash beds.
Beds between lavaflows
Lameta beds (Intertrappean beds)
Lameta beds are of fluvial origin and contains important fossils of Dinosaurs (Titanosaur, Lametasaurus, Rajasaurus). Lithology is claystone, sandstone and limestone.
Bole beds
The term 'bole' means fossil laterite as they are believed to be the product of weathering of basalt through origin is still controversial. These are red to brown coloured clay between lavaflows. The observations revealed that the post formational weathering processes have least affected the original palaeo weathering characters of the red bole horizon and hence the intro basaltic palaeosols (weathering horizons) can effectively be used to constrain the palaeo weathering and palaeoclimates during the continental flood basalt episodes in the geologic past.
Economic minerals
Bauxite deposits are of importance which were formed in deccan basalt.
Zeolites are also found in these traps.
Beds between lavaflows
Lameta beds (Intertrappean beds)
Lameta beds are of fluvial origin and contains important fossils of Dinosaurs (Titanosaur, Lametasaurus, Rajasaurus). Lithology is claystone, sandstone and limestone.
Bole beds
The term 'bole' means fossil laterite as they are believed to be the product of weathering of basalt through origin is still controversial. These are red to brown coloured clay between lavaflows. The observations revealed that the post formational weathering processes have least affected the original palaeo weathering characters of the red bole horizon and hence the intro basaltic palaeosols (weathering horizons) can effectively be used to constrain the palaeo weathering and palaeoclimates during the continental flood basalt episodes in the geologic past.
Economic minerals
Bauxite deposits are of importance which were formed in deccan basalt.
Zeolites are also found in these traps.
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