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Poster Session
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Correlation between spectral signature of basalts & sandstones of Central India as obtained by Radiometric & Spectrophotometric
Techniques
Radiometric Studies:
Exotech Model 100A. Ground truth radiometer and SAC (ISRO) developed ground truth radiometer were used for obtaining field spectral data.
The above radiometers were taken in the field and was standardized by the lid cover for complete darkness or black of the gry scale and by using BaSO4 layer on a thin aluminium plate for standard white. The time of observation was in between 10 AM to 2 PM on a cloud free dry thereby minimizing the shadow effects.
Observations were taken for Vindhyan sandstone and plateau basalts. One to three sets of observations were taken for individual outrops. The location of the rock out crops where these observation were taken are shown in Map1.
Petrographical and Petrological Studies of the Rocks:
As mentioned above, uring the field work samples from different Geological formations were collected. Major rocks were Deccan trap Basalts, and Vindhyan sandstones. These rock samples were studied megascopically and microscopically. The results of these studies are presented as.
Vindhyan Sandstones:
The Vindhyan sandstones exposed around Bhopal are light brown to dark brown in colour. The change in colour is due to the presence and/or absence of iron content. The textures of the roch changes from outcrop to outcrop. Most of the Vindhyan sandstones are fine grained, Coryer and hard in nature. Quartz and feldspars are essential minerals. Mica mostly muscovite is present as acessory minerals.
Angularity of the grains is distinctly seen. Feldspars mostly orthoclase shows carls bad twiest and cleavage plains are distinetly seen. Cementing material is Silica. Presence of Iron orides made on the basis of opaque nature . Quartz shows various shades of colour with wavy exinc Vindhyan sandstones exposed around Hoshangabad shows colour of different shades or pink and gryy. These rocks are hard, compact and quartzitic in nature. Silica is the cemanting material. Due to high silicious binding nature of the quartz and feldspar grains are giving rise to the compact and hard nature of the Quartzitic sandstone formations Texture is uniformly coarse and subhedral to Anhedral grains of Feldspars are little elongted as compared to Quartz and this is the typical property bsides Carlsbad twinning which was the basis of identification of orthoclase feldspars. Overall study of Vindhyan Sandstones concluded that they are of Arkosic nature.
Plateau Basalts:
Plateau basalts of the Deccan trap were seen around Bhopal. These basalts are dark black in colour. Samples of weathered basalts shows dark drownish tint alongwith the original colour Basalts are mostly fine to medium grain in size showing aphenetic texture in hard speciments. Microscopic study revealed that these basalts shows poikitic to ophitic texture. The plagioclase mostly laboradorite occurs as lath shaped subhedral crystals and in highly weathered conditions it shows anhedral nature oriented at random to yield and interrupted meah work. Mostly aaround plagioclese laths the pyroxenes are sutrrounded. The pyroxenes are filled up with the rest of the rocks. Aegirine and Iron oxides are also seen as accessory mineral. The Table No. 1 shows the megascopic study of rocks.
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