Research Paper on Rocks found in India!
1. Archaean Groups of Rocks:
The Archaean groups of rocks comprises of the Archaean System of rocks and the Dharwar System of rocks.
(i) Archaean System of Rocks:
The Archaean Systems of rocks lies below the oldest unconformity, (unconformities are surfaces of removal or deposition that separate the younger strata of rocks from the older strata of rocks), known as the Eparchaean Unconformity.
As they are the oldest systems of rocks they occupy the cores of mountains like the Himalayas or are exposed in the most ancient segment of the earth’s crust such as the Indian Peninsula.
Some of the them might have been formed from the cooling and subsequent solidification of the molten material of the earth. Others may have been formed from the cementation of the sediments that were deposited in the primitive oceans of high chemical potency.
Some of them might have been formed from the metamorphosis of varieties of intruded magma and extruded masses of lava. The Archaean Systems of rocks are called the basement complex because of their complex nature.
The Archaean system of rocks are widely distributed in the Indian Peninsula including Karnataka, Andhra Pradesh, Tamil Nadu, Eastern Ghats Mountains, Orissa, Madhya Pradesh, West Bengal, Assam, Bihar and Rajasthan and the Central Himalayan ranges, Assam and Meghalaya.
The complex Archaean system of rocks of different origin are crystalline in nature, some parts of which were twisted and foliated as they were extremely metamorphosed. Different kinds of gneisses and schistâ€™s are the most common types of rocks recognized in the Archaean System of rocks.
The gneiss consists of different amounts of white or pink orthoclase, a little plagioclase, small grains of bluish quartz, muscovite, biotite, hornblende and the accessory minerals like tourmaline, epidote, chlorite, garnet, magnetite etc. The gneiss is extremely foliated and coarsely banded in texture. At many places they are so coarsely banded that the rock resembles a granite or some other plutonic rocks.
The relatively finer textured schist is very foliated. It composition is similar to gneiss, except that it contains a little less orthoclase. Pliyllite, granulites marbles, dolomites, slates with graphite talc-schists, and quartziteâ€™s have been found inter-bedded in the gneiss and the schists.
The Archean Systems include the following kinds of rocks:
(i) The Peninsular Gneiss was also called the Bengal gneiss because it was first studied in the Midnapur district of West Bengal. These finely foliated rocks vary in composition from granite to granodiorite or even amphiboliteâ€™s. They also contain plenty of accessory minerals like epidote, apatite, tourmaline, garnet, magnetite etc. They are also called dome gneiss because they have weathered to form the dome shaped mass.
(ii) Charnockites are bluish gray to dark coloured red rock of a medium to coarse grained texture. They consist of hypersthene, enstatite, blue coloured quartz, microcline, plagioclase, hornblende, augite and biotite. They also contain accessory minerals like zircon, magnetite, ilemenite, graphite and garnet.
(iii) Bundelkhand gneisses are so coarse grained that they look like granite. The typical Bundelkhand Gneiss is a pink to reddish brown, medium grained non-foliated and non-porphyritic granite that consists of quartz, orthoclase, microcline and little ferromagnesian minerals.
The ferromagnesian minerals, biotite and green hornblende have been more or less altered to epidote and calcite. Accessory minerals are usually rare. The Archaean system of rocks does not contain any fossil. They were formed during the azoic era when no life existed on the earth.
Some geologist thinks that some life existed during the azoic era because some calcareous rocks occur in the Archaean System of rocks. No fossils have been found in the Archaean Systems of rock because they were destroyed by intense metamorphism.
(ii) Dharwar System of Rocks:
The Archaean system of rocks, gneisses and schists were disintegrated and decomposed. The products of disintegration and decomposition were deposited in layers over the Archaean gneisses and schists.
These layers were later on cemented to form sedimentary rocks that were profusely injected with molten magma from below when they were metamorphosed to form the Dharwar System of rocks in South India, the Champaner System of rocks in Gujarat and the Aravalli System of rocks in Rajasthan.
Hence the Dharwar system of rocks mainly comprises of metamorphic rocks and a small proportion of sedimentary rocks. The Dharwar systems of rocks are mainly schists, phyllite and slate. The schists include hornblende schist chlorite-schists etc., which are inter-bedded quartziteâ€™s, and marbles. The Dharwar System of rocks is intruded by plutonic rocks like nepheline syenites, tourmaline granites, dunites etc.
The Dharwar system of rocks does not contain fossils since they were formed in the azoic era. This system of rocks, first studied in Dharwar in Karnataka, occur in Dharwar in Karnataka, Chotanagpur in Bihar, Assam and Rajasthan.
2. Purana Groups of Rocks:
The Cuddapah and the Vindhyan systems of rocks were grouped together under the Purana groups of rocks by Sir T.H. Holland in 1904. The Purana groups of rocks which are formed during the Proterozoic era do not contain fossils.
(i) Cuddapah System of Rocks
The name ‘Cuddapah’ originated from the Cuddapah districts of Andhra Pradesh where the Cuddapah systems of rocks were first studied. Intense earth movement occurred at the end of the azoic era when the primitive seas gradually receded and low-laying areas were elevated to form mountain ranges.
Materials were removed from the elevated areas and deposited in the valleys in layers which were cemented to form sedimentary rocks. Again the earth’s surface was crumpled to form elevated areas and basins which were gradually filled up with sediments derived from the elevated areas.
The layers of sediment were cemented to form the sedimentary rocks. These sedimentary rocks were folded and metamorphosed to different degrees to form the Cuddapah system of rocks. They mainly occur in the Cuddapah district of Andhra Pradesh, the Chhattisgarh district of Madhya Pradesh, and Sundargarh district of Orissa.
The Cuddapah System of rocks is more folded in Rajasthan where it is known as Delhi system, than elsewhere. The Cuddapah system of rocks comprises of quartzite, indurated sandstone, slates, shales and limestone.
(ii) Vindhyan System of Rocks:
The earth’s crust was subjected to broad uplifting and down warping after the Cuddapah period. Sediments were derived from the elevated areas and deposited in the valleys. These layers of sediments were cemented and metamorphosed to form the Vindhyan system of rocks which are almost horizontal and consists of sandstones, limestone’s and shales.
Vindhyan system of rocks had not been metamorphosed in any part. Shales have retained their laminated character and not been converted to slates. Similarly limestone had not been converted to marble. Lower Vindhyan rocks are mostly calcareous and argillaceous of marine origin. Their junction with older Aravalli rocks is faulty.
The Vindhyan System of rocks has been widely distributed. They cover a large area that extends from Dehri-on-Sone in Bihar to Gwalior and Hoshangabad and from Chittorgarh to Agra. Lower Vindhyan rocks occur in the valley of the Sone, Bhima and Godavari which the upper Vindhyan rocks occur at the north of the Narmada valley.
3. Gondwana Groups of Rocks:
The name GONDWANA was derived from the kingdom of the Gonads, a great ancient tribe who still inhabit Madhya Pradesh, where these rocks were first studied by H.B. Medlicott in 1872.
The Gondwana groups of rocks occur in the Narmada valley in Madhya Pradesh, Sone valley and Rajmahal Hills in Bihar, Da modar valley in Bihar and West Bengal, Mahanadi valley in Orissa, Godavari valley in Andhra Pradesh, Himalayan Foot Hills of Nepal, Bhutan, Assam, Kashmir, east coast of India between Cuttack and Cape Commorin, Saurashtra and Kutch.
Large numbers of trough faults were formed in the Damodar valley in Bihar and West Bengal, Narmada valley in Madhya Pradesh, Mahanadi valley in Orissa and Godavari valley in Andhra, towards the end of the middle carboniferous period.
Sediments were deposited in these basins till the end of the Jurassic period. There basins were tilted to one side or the other. Plants grew on these sediments, died and were buried under fresh deposits of sediments. The plants were converted to coal seams. The entire thickness of the continental deposits subsided and cemented to form the Gondwana groups of rocks. Gondwana coal fields contain dolerite and basalts.
The lower Gondwana system of rocks contain Glossopteris flora and include Talchir, Damuda (from Damodar) and Panchet series of rocks. The upper Gondwana system of rocks which contain ptilophyllom flora, include the Mahadeva, Jabalpur, Rajmahal and Umia series of rocks.
The Talchir series of rocks consist of greenish or brownish sandstone that lies over aeranaceous (sandy), micaceous or calcareous shales, conglomerates, grits and coal seams. The panchet series consists of greenish, buff and brownish sandstones and shales in the lower part and greenish micaceous and felsphatic sandstones and shales in the upper part.
The Mahadeva series of rocks consist of sandstones and reddish shales. Rajmahal series comprises of white and light coloured clays and massive soft sandstones. Umia series of rocks consist of sandstones that contain plant fossils.
4. Deccan Trap Rocks:
Volcanoes erupted intermittently towards the end of the cretaceous period to eject huge masses of molten materials called lava from the interior of the earth.
The lava covered about two lakhs square miles of area in the present Maharashtra, Madhya Pradesh, Andhra Pradesh and Kutch where it cooled down and formed step like rocks called the Deccan Trap rocks, which, however are not composed of volcanic materials from top to bottom since they had been intercalated by sedimentary rocks called the inter-trapping beds. Almond shaped cavities occur in the Deccan Trap rocks.
These cavities had been wholly or partially filled up with secondary materials like calcite, zeolite, chalcedony etc. The Deccan Trap rocks had been horizontally laid over the entire area in western and south-western India.
The Deccan Trap rock is a dark basic volcanic rock of mainly basaltic composition on the surface. It is thus called plateau basalt. Its dark colour is due to the dark colour of basalt and magnetite. The lava solidified below the surface of the earth to dolerite, of a coarse texture.
The Deccan Trap rocks are of porphyritic texture. The large crystals called the phenocysts are made up of plagioclase and the ground mass consists of Augite, plagioclase, olivine and magnetite. The inter-trappean beds are mostly composed of dark coloured cherty or siliceous rocks that usually contain fossils.
5. Mesozoic Group of Rocks:
The Mesozoic group of rocks comprises of Triassic, Jurassic and Cretaceous system of rocks. The Triassic system of rocks occurs in Spite and Kumaon in Himachal Pradesh, Kashmir and Sikkim, and mainly comprise of limestone’s and shales that contain fossils.
The Jurassic system of rocks consists of shale, limestone and quartzite that cover large areas in Kutch and Rajasthan. Black lustrous micacious shales containing abundant amounts of calcareous concretion occur at Spiti in Himachal Pradesh. The Spiti shales were intercalated with sandstones.
The Cretaceous system of rocks mainly comprises of varieties of sedimentary rocks that contain fossils especially those of foraminifera (a species of marine protozoa that had been enclosed within a perforated calcareous shale).
For example, most sandstones, shale and quartzite’s occurring in Spiti and Kumaon in Uttar Pradesh and Kashmir contain fossils. In Maharashtra, Ahmednagar, sandstones consists of thick horizontally bedded pink, red and brown coloured sandstone, shale and conglomerate that contain plant fossils.
Sandstone occurs in the lower and organic limestone occurs in the upper layer in Gwalior and Kathiawar. In Tiruchirapalli districts, the Cretaceous system of rocks consists of fine silts and calcareous shales and sandy clays containing ferruginous phosphatic and calcareous nodules. They contain coral and other fossils.
6. Tertiary Groups of Rocks:
The Tertiary groups of rocks are abundant in the Extra Peninsular regions from Kashmir along the Himalayan Foot Hills to Assam. They also occur from the Gulf of Cambay to Kutch in Gujarat, Rajasthan and the Coastal areas of Orissa, Tamil Nadu and Kerala. They mainly consist of various kinds of sedimentary rocks that include varieties of shale, limestone, sandstone, conglomerate etc. most of which contain different kinds of fossils including those of foraminifera.
Pleistocene and Recent Geological Formation:
During the Pleistocene and recent periods, mainly unconsolidated sediments of clay, silt and sand have been deposited. The closure of the Pleistocene period was marked by laterisation.
The agriculturally important geological formations during the recent period are as follows:
1. Indo-Gangetic alluvium:
Alluvium is the product of weathering of rocks constituting the mountains that have been brought by the great river systems the Indus, the Ganges, the Brahmaputra, the Narmada, the Godavari and the Mahanadi, in various degrees of fineness and deposited them as they traverse the plains. The Indo-Gangetic Alluvium has filled up a depression between the Himalayan mountain ranges and the peninsular shield.
Large areas in Haryana, Punjab and Kashmir have been covered by windblown dust called Loess which is fine grained buff or grey coloured fine sandy to clayey in nature.
3. Desert Sands:
The Thar Desert in western and south-western Rajasthan is covered by several metres of sand which is constantly being shifted by winds blowing from the south-west direction. The sub-soil water varies in quality from place to place. It can be used for irrigation in eastern sides. It is saline is semi-desert areas. Rainfall is very low because the Aravalli Mountains run parallel to the direction of the south-west monsoon wind.
Laterite is extensively distributed in the Peninsular India i.e. Kerala, Madhya Pradesh, Maharashtra, Karnataka, Tamil Nadu and Orissa. Laterite is a porous, pitted clay like rock with red yellow, brown grey and mottled colours. It consists mainly of oxides of iron and aluminum. It is very soft when freshly dug up, but becomes hard like bricks, when it comes in contact with moist air.
Rocks of Karnataka:
Almost the whole of Karnataka is made up of the Archaean groups of rocks, although Vindhyan system and Deccan trap rocks occur in small areas. The Archaean groups of rocks comprises of Archaean system and Dharwar system of rocks.
The Peninsular gneiss, and the Charnokite, the champion gneiss and the Closepet granite belong to the Archaean system of rocks. A heterogeneous mixture of different kinds of granitic rocks profusely penetrated the schistose rocks after the latter were folded, crumpled and metamorphosed to from the Peninsular gneiss which therefore included varieties of rocks like granite, granodiorite, gneissic granite and banded or composite gneisses, the granite constituent of which show distinct sign of intrusion.
The banded gneisses are made up of white bands of quartz feldspar alternating with dark bands of hornblende, biotite and accessory minerals. Charnokite is a bluish-grey to dark coloured medium to coarse grained rocks, composed of hypersthene, enstatite, blue coloured quartz micro line, plagioclase, hornblende, Augite and biotite. It also contains accessory minerals like zircon, magnetite, ilemenite, garnet and graphite.
Champion gneiss has been considered to be the oldest gneiss in Karnataka. It has been named after the Champion reef in the Kolar gold-field; the rocks are dull grey to pink in colour, and greasy looking comprising of quartz, oligoclase, andesine and muscovite with apatite and magnetite as accessory minerals.
Clasepet granites which are extensively exposed near Clasepet and Channapetna, are grey or pink coloured intrusive biotite-granite of a coarse texture. The Dharwar system of rocks of Karnataka has been divided into five geographical groups from west to east. Hornblende schist and thin bands of hematite quartzite occur in the west.
Banded ferruginous rocks and magniferous rocks occur in the west-central area i.e. Shimoga and Babubudan belt. Lots of igneous and banded ferrugineous rocks and limestone occur in the Chitaldrug-Chiknaya Kanhalli and Naga Mangala belts of the central area.
Varieties of rocks like Quartz-magnetite-granulities, silliminite-quartzite, cordierite-hypersthene-gneisses, cordierite-mica-gneisses, cummington-schists, and pyroxene-geneisses are included in the east central group. A belt of schist rocks occurs in the east.
The Vindhyan system of rocks which occurs in the Gulbarga and Bijapur districts comprises of lower, middle and upper divisions. The lower division consists of sandstone or green and purple shales. The middle division consists of creamy grey, bluish and buff coloured limestone.
The upper division consists of black, blue, buff and purple shales, Sandstone and limestone occur at the bottom and top respectively of the upper Vindhyan system. Deccan Traps that comprise of basalts and dolerites occur in small areas in Hassan, Kadur and Mysore districts. Cappingâ€™s of laterites having been found over the Deccan Trap rocks.
Rocks of Kerala:
Different kinds of gneiss belonging to the Archaean system of rocks have been found in south Malabar. Charnokite containing orthopyroxene occurs in Travancore; Magnesia rich Pyroxenite has been found at Neyyoor in South Travancore. The Miocene system of rocks that comprises of fossiliferous limestone sand and clay, occur at Padappakara near Quilon.
Warkalli (Varkala) sandstone that occurs along the coast of Kerala also belongs to the Miocene system of rocks. They are ferruginous sandstones that have been penetrated by clays. They gradually change from grey to dark grey clay and carbonaceous sandstone. They occur just over the Quilon limestone which is a very compact and hard fossiliferous limestone.
It contains high amounts of calcium and low amounts of magnesium and 6 to 15 per cent silica Varkala sandstones have been laterised to depth of 10 to 13 metres. Felspathic gneisses which occur below the Vaskala sandstone at some places have been converted to Kaoline to a depth of about ten metres or more. Kaoline occurs at Kundara near Quilon and several other places in Malabar.
The laterite that occurs in Malabar is red, yellow, grey and mottled porous clay-like material that mainly consists of oxides of iron and aluminum. It is very soft when freshly dug and becomes very hard on exposure to the atmosphere.
Rocks of Tamil Nadu:
Mesozoic (Cretaceous system) and Tertiary groups of rocks occur in the coastal regions of Tamil Nadu.
The major areas of this state have been covered by Archaean groups of rocks, as follows:
Several bands of schistone rocks are widely distributed in Salem and Coimbatore districts where geologists have found a few bands of magnetite quartzite, formed from banded haematite-quartzite. Older grey gneisses and younger pink gneisses occur in Arcot, Tiruchirampalli and Madurai. Crystalline limestone occurs within the gneisses at many places.
Several places in Salem district have been covered by Olivine rocks containing magnetite. Magnesia rich Pyroxenite occurs at the Tamil Nadu-Kerala border. Ultra basic igneous rocks have been found near Ten Mundiyanur about 20 km south-west of Tiruvannamalai.
These ultra-basic igneous rocks which are serpentinised dunite and Peridotite with veins of magnetite are flanked by Pyroxenite on one side by corundum-feldspar rocks associated with granite and pegmatite on the other meta-Anorthosite gneisses and metagabbro have been found near Pattalur in the Salem district.
The Anorthosite of Tiruchirapalli district comprises of quartzite, amphibolite and crystalline limestone. Alkali rocks which include nepheline-syenite and its varieties containing hornblende and biotite, aegirine-augite, feldspar and feldspar corundum rock have been found at and around Sivamalai.
The Gondwana groups of rocks occurring near Madras comprise of two stages. The lower stage is called Sriperumbudur and consists of white to pink clay, shales and felspathic sandstone and fossils. The upper stage is called the Satyavedu stage and consists of purple mottled ferruginous sandstone which contains fragmentary plant fossils.
The Gondwana groups of rocks which cover a small area near Uttatur village in Tiruchirapalli district are micaceous shales, grey sandstone and grits containing calcareous concretion. They contain fossils.
The Gondwana groups of rocks have been found near Sivaganga in the Ramnad district, where they are made up of boulders and conglomerates at the lower part and micaceous sandstone and alternating grits and shales in the upper part. They contain plant fossils.
The Cretaceous system of rocks that occur in Tiruchirappalli district comprises of Uttatur, Trichinoploy, Ariyalur and Niniyur stages. The Uttatur stage consists of fine silt, calcareous shales and sandy clays containing ferruginous, phospha tic and calcareous nodules. Dark grey to yellow somewhat sandy limestone occurs at the base of the Uttafur beds.
It contains coral and other fossils the Tiruchirappalli stage comprises of sandstone, grits, calcareous grits, shales and bands of shell limestone. The Ariyalur stage is made up of grey to light brown arigillaceous (clayey) and white sandstones. Fossils occur at the lower part of the Ariyalur stage. The Niniyur stage consists of grey brown ochreous sandstones and shales which contain fragments of flint and chert that contains fossils.
The Tertiary groups of rocks cover the coastal strip of South Arcot, Tanjore and Ramanathapuram districts. They are sandstone and shales that contain fossils. A wide stretch of somewhat ferruginous and laterised sandstone called Cuddalore sandstone occurs intermittently from Rameshwaram through Padu Kottah, Tanjore, Cuddalore, Pondicherry and Madras.
Rocks of Andhra Pradesh:
The important rocks of Andhra Pradesh include the Archaean groups of rocks, Cuddapah system of rocks, Gondwana groups of rocks, Deccan Traps and rocks formed during the Pleistocene period. The Dharwar system of rocks, found in Karimnagar and Warangal district, includes hornblende-talc, chlorite and mica schists and quartzite’s. Other important Archaean groups of rocks of these districts include grey gneisses and pink gneisses.
The gray gneiss which corresponds to peninsular gneiss consists of light bands of quartz and feldspar, and dark bands of mica and hornblende. Pink gneiss comprises of quartz, microcline and orthoclase, acid plagioclase.
Four kinds of gneisses have been identified in the Nellore and Guntur districts, of which two are schistose and two massive. The schistose gneisses comprises of quartz, mica, hornblende and talc schists and quartz magnetite rocks. This massive gneisses comprises of grey, sometimes prophyrite gneiss a red granitoid gneiss.
The banded grey gneiss varies in composition and contains streaks and bands of micaceous gneiss and Charnokite. This belongs to the groups of peninsular gneisses. Pegmatiteâ€™s and quartz veins have intruded into the schists and young granitic red gneisses.
The sedimentary rocks of the Cuddapah system occur on the gneissic and schistose rocks belonging to the Archaean group. The Cuddapah system of rocks consists of the Papaghmi, Cheyair, Nallamalai and Kistna series. The Pagni series occurs on the gneisses and schists of the Archaean groups of rocks with a profound unconformity called eparchean unconformity, and consist of the lower Gulcheru stage and the upper Vempalle stage.
The Gulcheru stage consists of conglomerates, grits and sandstone; the Vempalle stage consists of grey to buff coloured limestone that contains chart, chalcedony and shales. The Cheyair series includes lower Pulivendla stage and upper Tadpatri stage. The Pulivendla stage consists of quartzite, conglomerates, and sandstones.
The Tadpatri stage consists of slaty shale that contains thin beds of siliceous limestone, chert jasper and intrusive basic silts. The Nallamalai series consists of lower Bairenkonda quartzite and upper Cumbum shales that include shales and slates. The Kistna series consist of quartzite.
The Gondwana groups of rocks occurring between Rajahmundry and Vijaywada consists of Golapilli sandstone below, Raghavapuram shales in the middle and the Tirupati sandstone above. All these stage contain fossils.
The Gondwana groups of rocks occurring near Budavada in the Ongole district comprises of three beds. Buff coloured Budavada sandstone occurs at the lowest bed. The middle bed consists of purplish variegated shales.
The topmost bed consists of brown and red un-fossiliferous sandstone. Deccan Traps which mainly comprise of basalt and dolerite, occur in Rajahmundry. The Godavari alluvium is mainly composed of brown clay and sandy silts, with nodules of Kankar and beds of gravel.
Rocks of Maharashtra:
Major areas of Maharashtra have been covered by the Deccan Trap rocks, formed by the solidification of molten lava. This lava formed step-like terraces. Deccan trap rocks have been called plateau basalt by H.S. Washington because they consist mainly of basalts on the surface and dolerities and gabbros below the surface of the earth.
They are generally a dark grey to dark greenish colour. Brown hind purple tints have also been seen. Buff to cream coloured, more acidic (Trachytic) types have been seen near Bombay. The non-vesicular basaltic types are hard compact and medium to fine grained, and break with a fracture. The vesicular types are comparatively soft and break more easily.
The Archaean groups occur in Nagpur and Bhandara district. They include the Sakoi series in the north and the Sauser series in the south. The Sakoi series consist of chlorite and sericite schists and hematinic iron ore. The Sauser series comprises of calogranulites, marbles, garniteferous schists and manganese silicates and gondites.
The cretaceous system of rocks include Ahmednagar sandstone which comprise of thick horizontally bedded sandstone shales and conglomerates of pink, red and brown colour. It contains plant fossils. The Godavari alluvium of Maharashtra consists mainly of brown clay and sandy silts and nodules of kankar and beds of gravel.
Rocks of Madhya Pradesh:
The Archaean group of rocks occurs in the districts of Raipur, Durg, Bilaspur, and Balaghat, Chhindwara and Jabalpur. The Archaean groups of rocks of Raipur district comprise of quartzite, phyllites, micas schist and banded haematite-quartzite. Volcanic agglomerates and epidorite covered the schistose rocks of Durg district.
Schistose rocks also occur in Bastar, Bilaspur and Balaghat district. Highly metamorphosed schistose rocks which occur in the Chhindwara district comprises of varieties of metamorphic rocks like different kinds of marble, schists, quartzite’s etc.
The Archaean groups of rocks of Jabalpur district include conglomerates, phyllites, mica schists, calcitic and dolomitic marbles and banded ferruginous rocks.
The Vindhyan system of rocks have been found in the districts of Rewa, Gwalior, Bastar, Raipur, Durg and Bilaspur, sandstone and shale occur at Rewa and Gwalior. Shale, quartzite, conglomerate and limestone have been found in Bastar district. Shaly limestone, calcareous shale and felspathic sandstone occurs at Raipur, Durg and Bilaspur districts.
The Gondwana groups of rocks have been found at Rewa, Panchmarhi and Jabalpur. The Parsora stage of the Panchet series which occur at south Rewa, consist of medium grained sandstone with micaceous and ferruginous bands.
The Mahadeva series which occurs at Panchmarhi includes Panchmarhi, Denwa and Bagra stages. The Panchmarhi stage comprises of red and buff coloured sandstones with some red clays at the top and the bottom.
The Denwa stage which occurs just above the Panchmarhi stage comprises of pale brownish or greenish yellow, bright mottled red clays. It contains bands of white and yellow sandstone which are often calcareous.
The Bagra stage consists of pebble-beds and conglomerates with red jasper in a matrix of red sandy clay. Jabalpur series consists of white and light coloured clays and massive soft sandstones. Some of the shales are carbonaceous.
The cretaceous system of rocks which have been found in Gwalior, are made up two portions. The lower portion is called Nimar sandstone, comprising of basal conglomerate and layers of sandstone and shale above. Organic limestone occurs at the upper portion. These rock systems contain fossils.
Rocks of Rajasthan:
The Archaean groups of rocks of Rajasthan comprises of Bundelkhand gneiss, banded gneissic complex and the Aravalli system of rocks, Erinpura granite and Malani igneous suite.
The Bundelkhand gneiss which occur in the Berach valley between Chittor and Bhilwara is a pink to reddish coloured, medium grained non-foliated and non-porphyuritic granite that consists of quartz, orthoclase and minor amounts of micro-clinic, buotite and green hornblende. Bundelkhand gneiss has become foliated near the junction of Berach and Began rivers.
The banded gneissic complex of Rajasthan usually consists of alternating bands of biotite gneiss and granite. Several varieties of banded gneissic complexes have been found in Rajasthan. These banded gneissic complexes consist of biotite and chlorite schists in south Mewar.
They grade into granite- gneiss or even into un-foliated granite at many places. They also contain some hornblende-schist and epidorite. The banded gneissic complex of central and north Mewar and Ajmer consists of dark schists and granite ferrous granulites which are profusely penetrated by bio-tie-granite. Other varieties include a grained and somewhat foliated porphyritic granite and grey, fine, slightly foliated granite gneiss.
The Aravalli system of rocks are dominantly argillaceous (clayey) in composition and are metamorphosed and folded in an increasing degree from east to west. They consist of basal and upper beds.
The basal bed of arkose and grity quartzites lies over the Bundelkhand gneiss or the banded gneissic complex; shales and phyllites occur over the arkose and gritty quartzite. Some altered basic volcanoes are associated with the shales and phyllite at some places. Limestone and quartzite occur at certain places.
The Aravalli system of rocks of eastern Mewar includes Binota shales which are brown and dive shales that contain ferruginous and clay concretions. The Aravalli system of rocks, found near Ranthambhor and Sawai Madhopur, include reddish sandstones and quartzite. The quartzites have been inter-bedded with shales and dolerite at Ranthambhor.
The Raialo series of rocks, found in Alwar, Jaipur around Railo, Ajmer and Mewar Makrana, Ras and Godwar, North of Udaipur city, and through athdwara, Rajsamand and Kankroli into Par-Benara and Jahazpur hills, it mainly consist of limestone (about 600 metre thick) that lies over thin basal beds of sandstone and conglomerates.
The Erinpura granite which has been found in eastern Mewar, Palanpur, Idar, Sirohi, Beawar, Jaipur and Alwar and Mt. Abu generally consists of biotite and granite though its pegamtite contains muscovite and tourmaline. Reddish malani rhyolite containing pink orthoclase oligoclase and corroded quartz crystals covers a larger area in Jodhpur.
The Delhi System of rocks includes ‘Calc-gneisses’, ‘Calc-schists’, phyllite and biotite-schists of Mewar and Ajmer, Alwar and Ajabagrah Series of Alwar and Jaipur, Hornstone breccia and Kushalgarh limestone of Alwar and Jiran sandstone and shales and grits of Chittor and Nimbahera.
The calc-schists were originally thin bedded biotite limestone’s, part of which had metamorphosed to form the schistose rocks when Tremolite disposed, biotite and feldspar were developed. They show dark and white bands, Calcgneisses are mainly dark banded, siliceous limestone Alwar series consisting of compact quartzite, conglomerate and grits.
The Ajabgrah series is dominantly argillaceous in nature and contain minor amounts of siliceous limestone, calcareous silt and ferruginous quartzite’s. Hornstone breccia consists of angular particles of quartz in a fine grained dark matrix of ferruginous and siliceous matter.
Kushalgarh, limestones are dominantly limestones with dust-like inclusions forming a banded structure. Jiran sandstones are compact, hard, pale grey quatzite which are sometime ferruginous and mottled with purple stains.
The Vindhyan system of rocks occurring in Bundi, Kota, Dholwar Bharatpur, Jaipur and Bikaner, consists of fine grained, soft red sandstone with white specks. The Vindhyan system of rocks have also been found in Karauli and Chittor-Jhalrapatan area.
Breccia have been found over limestone, which occurs above sandstone and conglomerate that lies over phyllities at Karauli. Grits and conglomerate occur above shale at the Chittor-Jhalrapatan area.
The Jurassic system of rocks which have been found in Jaisalmer comprises of different kinds of sedimentary rocks. The earliest formation is Lathi beds of sandstone and fossils in the lower part and limestone in upper part.
The next formation was Jaisalmer limestone that consists of organic limestone and calcareous sandstone, followed by a Baisakhi bed of sandstone and gypseous shales. This was followed by Bedser beds of ferruginous sandstone and grits.
The succeeding beds are Parihar sandstone of unfossiliferrous and felspathic sandstone and quartzite. Abur bed of limestone, grit and shales containing fossils and the topmost Bandah and Khuila bed of dense siliceous limestones containing fossils. A large area in western and south-western Rajasthan is covered by several meters of sand.
Rocks of Gujarat:
The Champaner series of rocks belong to the Archaean Groups of rocks, and includes quartzite, conglomerates, slates and limestone.
The Gondwana system of rocks, which has been found in Kutch, consists of sandstone and shales containing fossils.
A large area in Kutch has been covered by the Jurassic system of rocks, which mainly comprises of four series. The patcham series consists of clastic sandstone and yellow limestones that contains fossils. The Chari series consists of organic a limestone that contains fossils. The Katrol series consist, of different types of sandstone and shales that contain fossils. The Umia series including and stone, conglomerates, shales and fossils.
The Deccan Trap rocks, extensively found in Kathiawar and Kutch, originated from basaltic lava flows. They mainly consist of dolerite and basalt but other rocks like olivine-gabbro, andesite, rhyolite, felsite etc. have also been found inter-bedded with them.
The Eocene system of rocks of Kutch, lying over the Deccan Trap rocks, comprises of the lowermost Madh series, the middle Kakdi series and the upper Berwali series. The Kakdi series includes a lower layer of carboniferous shales with lignite and ferruginous and gypsiferous clays and upper layers containing fossils.
The upper Berwali series consists of limestone that lies over clay containing fossils. The Eocene system of rocks occurring between Surat and Broach comprises of basal bed of impure limestone containing fossils, and an upper bed of sandstone, shales, conglomerates etc. in which fossils are present at some places.
The Oligocene and Miocene system of rocks have also been found in Kutch. The Oligocene system of rocks comprises of organic limestone containing fossils. The lower part of the Miocene system comprises of organic limestone and the upper part comprises of clays and siltstone containing fossils.
Rocks of Uttar Pradesh:
Most of the plain areas of Uttar Pradesh are made up of Indo-Gangetic alluvium, brought down from the Himalayas by the Ganges river system and deposited in the plain areas. The older alluvium called Bhangar is darker clay, rich in calcereous kankar.
It was formed during the middle to upper pleistocene period. The newer alluvium called khadar is a light coloured, sandy and gravely material, almost free from lime kankar. It was formed during the upper Pleistocene to recent period.
The Siwalik system of rocks occurs at the Himalayan foot hills in Hardwar and Dehra Dun. They are composed of sandstone, grits, conglomerates, pseudo-conglomerates, clay and silts that contain fossils. They are often folded and faulted and lie at steep angles against other formation.
A large out-crop of gneissic granite occurs in Bundelkhand. It is mainly metasomatic granite which had assimilated older rocks like quartzite, mica-schist, talc-schists amphibolites etc. Schistose rocks have been found in the Mirzapur district.
Rocks of Bihar:
Iron-ore series rocks include basic lava, shales, banded haematite-quartzite and purple and grey limestone and occur at the north of a thrust zone in the Singhbhum district. They are called iron-ore series because they contain iron- ore. They lie over hornblende-schist, quartzite, micacious and chlorite schist.
Metamorphosed shales and sandy shales occur within the thrust zone. Highly metamorphosed mica-schist, hornblende-schist and chlorite schist occur at the north of the thrust zone in the Singhbhum district belongs to the Dharwar system of rocks.
The Archaean system of rocks includes Chota Nagpur granite-gneiss and Singhbhum granite. Chota Nagpur granitegnesis is generally coarse, porphyritic and contains quartz, microcline, orthoclase, oligoclase, biotite and little appetite.
It occurs in Santhal Paraganas, Hazaribagh, Ranchi and Palamau districts. This Chota Nagpur granite gneiss weathers in Dhanbad, Ranchi and Hazaribagh districts to form dome-gneiss or Bengal gneiss.
Various types of schistose rocks occur in the Gaya and Hazaribagh districts. The Gondwana system of rocks occurs in the Damodar valley in south Bihar. This mainly comprises of sandstone and coal seams. Conglomerate, sandstone and limestone occur at Chaibasa in Singhbhum district.
The Gondwana systems of rocks have been found in the coal fields of Bihar. Pebbly grits and sandstone with intercalated coal seams occur in the Giridih. Daltonganj, Umaria, Mahapani and Shahpur field, while fawn coloured sandstone and grits and beds of shale occur in the Jharia coal field.
The sandstone contains more or less decomposed feldspar. Coal seams are often present in the Gondwana system of rocks, which occurs in south Bihar at the Bengal border and comprises of basaltic lava flow which had been intercalated with carbonaceous shale that contains plant fossils.
Sedimentary rocks belonging to the Kolhan series of the Cuddapah system have been found over the iron ore series in the south Singhbhum district. They comprise of un-metamorphosed conglomerate, purple sandstone, shale and limestone.
Sedimentary rocks belonging to the Semri series of the lower Vindhyan system of rocks have been found west of Sasaram. They comprise of several beds. The lowermost bed comprises of basal conglomerate and limestone overlaid by shales, sandstone and tuffs that in turn are overlaid by olive shales, fawn limestone and gluconitic sandstone. Indo-Gangetic alluvium occurs in north Bihar and at the north of the Chota Nagpur plateau. It comprises of Pleistocene and Recent deposit of clay and sand.
Rocks of Orissa:
Gondite rocks that belong to the Archaean group have found at the central part of an anticline in the Sundargrah district. They consist of quartzspessarite, rhodonite, winchite and manganese ore. These oldest rocks are overlaid by carbonaceous quartzites, phyllites, dolimitic and calcific marbles, and carbonaceous shales which had been intercalated with phyllites and mica schist.
The carbonaceous phyllites are slaty at certain places. The marble contains a large reserve of good limestone and dolomite. A shear zone occurs above them. Raghunathapalli conglomerate occurs above this shear zone.
The Cuddapah system (Kolhan series) occurs only in the Keonjhar district. It consists of basal conglomerate, purple sandstone, shale and limestone. The Gondwana groups of rocks occur in the Mahanadi valley.
The Telcher series of this group comprises of several beds rocks. The lowermost bed is of boulders overlaid greenish arenaceous (sandy), micaceous or calcareous prismatic fragments of shales and greenish brown sandstone.
Yellowish brown limestone containing abundant oyster shells have been found at Molia near Baripeda in the Mayurbhanj district. They belong to the Miocene system of the Tertiary groups of rocks.
Rocks of West Bengal:
The Bengal gneiss of the Archaean groups of rocks occurs in the Midnapore district. It consists, mainly of gneiss and schist. Anorthite belonging to the Archaean group occurs at the south of the Raniganj coal field.
Its composition varies from almost pure plagioclase rocks to Anorthosite gabbro and diorite. Its northern boundary is faulted against the Gondwana groups of rocks.
The Gondwana Groups of rocks occur at Raniganj and comprise of sand stone, shales and coal seams. They belong to the Raniganj series of the Damuda system.
Shales, limestone, sand and calcareous sandstone of the Cretaceous system occurs at Ghatal in Midnapore district. The Cretaceous system of rocks mainly trap wash and some white sandstone have also been found at Bolpur in the Birbhum district. Bengal formed the shelf areas of a marine basin where sediments were deposited during the Tertiary era.
The Eocene system or rocks, found at Jalangi in the Murshidabad district, consist of esturine carbonaceous shale containing pyrite, lignite and resins. The Oligocene system of rocks comprises of sandstone and lignitic shales at Burdwan, calcareous shales, shaly limestone and glauconitic sandstone containing fossils of foraminifera at Mesmari and sand, silt and shale at Pandua.
The sediments deposited during the Plio-pleistocene period in the Ganges delta are represented by the Debagram and Ranaghat formation.
The Debagram formation comprises of clay, calcareous shales and silts which are deltaic. The alternating marine deltaic Matla formation comprises of clay and silt. Clay and silt of Plio-pleistocene period have been found at Ranaghat.
Strips of laterised sandstone, felspathic grits and bluish grey mottled clay, known as the Durgapur beds, occur along the western border of the Raniganj coal field. These are covered by alluvium at some distance east of Durgapur. These sandstones also occur at Suri in the Birbhum district.
Rocks of Assam:
Gneisses, schists and granites belonging to the Archaean system of rocks, occur in the Mikir hills. The Shillong series belonging to the Dharwar system also occur in at the same area. It comprises of quartzite, conglomerates, phyllites, chlorite-schists mica-schist and hornblende-schists. Limestone containing plant fossils that belong to the lower Gondwana system of rocks have been found in the Aka hills north of Tejpur and the Bharati valley.
A Tertiary group of rocks have been found in eastern and south eastern Assam. The Dissang series of rocks were developed in the Brahmaputra valley during the upper cretaceous to the upper Eocene period.
It consists of splintery dark grey shales intercalated with fine grained sandstone. The Oligocene and Miocene system of rocks of Assam include the Barail and the Surma series. The Barail series of the upper Assam include Tilak Parbat stage of 450 metres of carbonaceous shales and coal seams, the Baragoloi stage 3000 metres of sandstone, carbonaceous shales and coal seams and the Naogaon stage of 2400 metres of sandstone.
The Barail series of the Surma valley and north Cachar includes the Renji stage of 900 metres of hard massive sandstone and very subordinate shales, the Jenam stage of 900 to 1200 metres of sandstones, alternating with shales and the Laisong stage of 2400 metres of hard, thin bedded sandstone and subordinate shales.
The Surma series of the Surma valley include 900 to 1500 metres of the Boka Bil stage and 1200 to 2400 metres of the Bhuban stage. The Boka Bil stage consists of sandy shales, silts, sandstone. The Bhuban stage consists of shales, sandy shales, sandstones and conglomerates.
The Siwalik system of rocks of Assam which developed during the middle Miocene to the lower Pleistocene period comprises of the Tipam series, the Dupi Tila series and the Dihing series.
The Tipam series has been found from the Surma valley to upper Assam, in upper Assam, it includes 760 metres thickness of Namsang beds of sandstone, grit and conglomerate, 909 to 1018 metres.
Thickness of Girujan clay, composed of mottled clay and sandy clay subordinate sandstone, and a 909 to 2424 metres thickness of Tipam sandstone, composed of gritty ferruginous sandstone and some conglomerate shale parting. The Dupi Tila series consists of about a 3000 metre thickness of clay-and sandstone. The Dihing series consists of a great thickness of pebble beds with subordinate sandstone and clay bands.
Rocks of Meghalaya:
Meghalaya is a detached blocks of the Peninsular plateau. So it is mainly made up of the Archaean groups of rocks though some Tertiary groups of rocks have also been found.
The Archaean groups of rocks of the Khasi and Jaintia hills consist of banded, composite, and biotite-granite-gneisses. The granatic constituent consists of quartz, microperthite, some microcline, oligoclase and biotite and accessory minerals like garnet, apatite, zircon etc. The Gneisses are associated with garnet-quartzites.
The Shillong series which belongs to the Dharwar system of rocks occurs above the gneissic complex. The Shillong series consists of quartzite, conglomerate, phyllite, chlorite-schist, mica-schist and hornblende-schist. Occasionally carbonaceous slates and ferruginous rocks also occur. The Shillong series had been intruded upon by Khasi green stone that consist of epidorite, amphibolites and amphibole-schits.
Mylliem granite is younger than Khasi greenstone. It is a homogeneous, fairly coarse biotitegranite containing prophyritic pink micro clinic orthoclase some acid plagioclase, biotite and hornblende and accessory minerals like appatite, magnetite and zircon. The granite and gneisses are traversed by dykes of dolerite.
The marine cretaceous system of rocks occurs in the Garo, Khasi and Jaintia hills. They are dominantly sandy in nature although shales and carbonaceous materials are so occasionally present. They are composed of sandstone and some coaly layer in the Garo hills.
The Mahadek and Langpur stages occur over the basal bed of conglomerate in the Khasi and the Jaintia hills. The Mahadek stage consists of a 230 metre thickness of hard, gritty, coarse glauconitic sandstone with a fossil ferous horizon near the top. This is overlaid by the Langper stage of impure limestone, calcareous shales and sandstone.
The Tertiary groups of rocks of Meghalaya include the Jaintia series and the Kopili series. The Jaintia series consists of shales, sandstone and limestone, the Kopili series of alternate layers of shale and sandstone and fossiliferous limestone.
Rocks of Nagaland:
Nagaland is made up the Paleozoic, Mesozoic (Cretaceous system only) and Tertiary groups of rocks. Alluvium of the Pleistocene and the recent period occurs along the courses of rivers.
The Paleozoic groups of rock includes only the Nimi formation, composed of limestone, quartzite, phyllite, carbonaceous phyllite, schistose granite and
Quartz-serictie-schist. The Zepuhu formation belongs to the Cretaceous system of rocks. It is composed of amphibolite, serpentinite, peridotie, dunite, pyroxenite gabbrodiorite, basalt, and esite, glaucophane schist, basic schist etc.
Which are intermingled with oceanic sediments like chert, grey wacke, limestone, cherty quartzite and phyllite. The Tertiary groups of rocks comprises of the Disang series of the Eocene system, the Barail Series of the Oligocene system the Surma and Tipam series of the Miocene system and the Dihang series of the Pliocene system.
Each of these series of rocks is separated from the others by an unconformity. The Barail and the Surma series of rocks are dominantly by Mollusca sediments. The former is composed of well bedded felspathic sandstone, carbonaceous shale and coal, while the latter is composed of felspathic sandstone, shale and clay.
The succeeding Tipam series comprises of two layers, a lower one contain felspathic and ferruginous sandstone, and upper one contain shale, mottled clay, sandy clay and ferruginous clay (Girujam clay).
The Disang series consists of pebble beds, gravels, thin clay and sandy. The alluvium is composed of un-assorted clay, coarse sand, and gravel and boulder bed.