GENERAL

GEOLOGY

[The section on Geology is contributed by Geological Survey of India.].

Description of Rock Units.

A general sequence of rock units in order of increasing antiquity is tabulated below:

Archaeans.

The rocks of Archaean age include granites, gneisses, quartzites, brecciated quartzites and banded magnetite rocks with intrusives. Granites are coarse-grained and light pinkish in colour, primarily composed of biotite, flesh coloured felspar and quartz. Most of the outcrops appear to be highly decomposed, which are intruded by numerous quartz veins and quartz-felspar pegmatite. The gneisses occupy a vast area. They show profound weathering resulting in their forming the plains covered by mantle of soils derived from them. Exposures of these gneissic rocks are sporadic due to their susceptibility to quick weathering. Megascopically, the gneisses are leucorcratic and fine to medium grained. They are generally massive and well foliated. Quartz, felspar, muscovite and biotite are easily recognisable. Some gneisses are intersected with thin veins of pink felspar. Amphibolites occur as conformable bands and layers in the gneisses. They are, however, intensely weathered and exposures of fresh rock are rare. Megascopically, the amphibolites are light to dark green in colour but generally altered and soft. Hornblende and felspars are the only recognisable minerals in hard specimens. Phyllites occur in the extreme north of the area. They are fine grained, compact and generally non-fissile. Two types of phyllites are observed. One variety is pink to greenish grey in colour, comparatively soft and shows faint schistose character. The other variety is dark grey in colour and being arenaceous is comparatively hard and compact. The quartzites and banded quartz-magnetites which appear to belong to one cycle of sedi-mentation are remnants of the older metasediments (Dharwars) occurring as isolated hills and knolls within the gneisses. The banded quartz-magnetite rocks are composed of alternating layers of ore minerals (both crystalline magnetite and hematite) and quartz. Brecciated quartzites stand out prominent at many points as isolated small hills and are intensely fractured, later filled up by the secondary silica. Granites, granite-pegmatites and basic rocks are intrusives in gneisses and amphibolites and generally occur as thin discordant and concordant bodies. The granites and granite-pegmatites are medium to coarse grained some times with large phenocrystas of felspars. The other recognisable minerals are quartz and little amount of ferro-magnesian minerals. The basic intrusives are melanocratic, medium grained, hard and compact, essentially composed of augites and plagioclase laths with minor amounts of secondary hornblende.

Late-Precambrian.

Cuddapah System.-The rocks of this system consist of shales, limestones and quartzites. The quartzites are medium to coarse grained and show wide ripple marks at several places. The quartzites are overlain by grey, silicious, massive, impure lime-stones. These limestones usually do not show any gradational relation with quartzites, but they probably lie on a disconformable surface above the quartzite. Most of the limestones are lateritic and some are silicious and dolomitic in character. The shales are generally grey to purple in colour.

Vindhyan System.-The Vindhyan rocks of this area comprise sandstones, shales, limestones and conglomerates. The most persistent and well defined rock type of the Vindhyan system seen in the area are the sandstones, which show a wide range in colour, compaction and grain size. On account of their relative resistance to weathering they stand out as conspicuous hills and ridges. The most common type of sandstone is light reddish in colour and medium grained. Reddish sandstones are generally coarse grained and open textured. Fine-grained, compact, light-coloured sandstones form conspicuous exposures. The shales are generally line grained, thinbedded, light grey to light reddish in colour with development of a set of close vertical joints which make them fragmental. The limestones are thinly bedded, although in some places they are massive. They have a pale, dark grey to buff or red colour. Some bands of limestone are rich in lime and some in magnesia. The dip of the rocks varies from 15° to almost vertical. The conglomerates have a limited lateral and vertical extent and are often partially removed by slumping of the jointed blocks. They may vary from coarse, loosely cemented to medium compact and indurated type. Their thickness varies at places. The pebbles are well rounded to sub-angular, ill-sorted and without any preferred orientation. They are mostly of sandstone, vein quartz, quartzite, quartz-magnetite rock and chert fragments. The pebbles of sandstone are mostly light reddish in colour, compact and fine grained.

Upper Carboniferous to Upper Trias.

Gondwana system.-The formations belonging to this division are referable to the following groups: -

Chikiala beds,

Kota Maleri,

 Kamthis,

Barakars.

Talchirs.

The Talchir series consist of a boulder bed at the bottom, followed by shales and sandstones successively. In Barakars, the predominant rocks are the white felspathic sandstone, shales and clays along with coal seams. The rocks in the Kamthi group are sandstones, shales, clays, and conglomerates of which the sand-stones and shales form the bulk of the series. The rocks of kota-maleri group comprise sandstones, clays, limestones in the order of abundance. The Chikiala beds represent the youngest member of the Gondwanas of the Pranhita-Godavari basin and comprise conglomerates, sandstones, shales and clays.

Cretaceous.

Lameta Beds.-The group is composed of clays and calcareous white sandstones. The clays are usually white with some reddish shales. The sandstones are loose and purplish-white in colour and are slightly calcareous. They present a sub-vitreous lustre on fractured surfaces.

Cretaceous-Eocene.

Deccan Traps and lntertrappeans.-A considerable part of the area is covered by Deccan Traps and intertrappean beds. The Deccan Traps consist of layers of basaltic lavas, varying from amygdaloidal basalt to fine grained dolerite, at places, the amygdules being filled with various minerals, like quartz amethyst, calcite, agate, chalcedony and jasper. The rocks are generally dark-grey to dark-greenish grey in colour. The non-vesicular types are hard, tough, compact and medium to fine grained, breaking with conchoidal fracture. The vesicular types are comparatively soft and break more easily.

Interbedded with the traps are found at several places thin beds of limestone, sandstones and shales, which in places have been converted to porcellanite and chert forming the intertrappean beds.

Pleistocene- Recent.

Laterite.-Laterite is found in the area at many places capping over the Deccan Traps and the gneisses at places. Laterite is a compact and vesicular rock essentially composed of hydrated oxides of aluminium and iron with small amounts of manganese oxides and titanium. Generally it is reddish brown in colour.

Recent.

Alluvium and Soil.-The bedrocks at several places, specially the river valley areas of the region are covered by recent alluvium deposited by the streams and different types of soils derived from breaking up of the underlying rocks.

The typical soil derived from the Deccan Trap is "Regur"' or black cotton soil. They contain high alumina and carbonate of calcium and magnesium with variable amount of potash, low nitrogen and phosphorus. They are generally porous and swell considerably on addition of water and dry up with cracks on losing the moisture. The black soil areas have a high degree of fertility and do not require manuring for long periods.

The gneisses and other rocks of the Archaean age on weathering give rise to "Red Soil" which is most common in the area where those rocks are present. The red soils are less fertile than the black soils.

Mineral Resources.

Coal.-In the Chandrapur-Wardha valley several coal mines are being worked. Following are the areas where the coal mines are found: -

(1) Chandrapur-Ballarshah area.-The Ballarpur Colliery is working 16 m thick seam in three sections. The seam trends North-North-East to South-South-West with a dip of 4 towards East to South-East. There is a major dip fault on the eastern side of the area against which the workings terminate. The fault has a northerly hade with a throw of 90 m. Hindusthan, Lalpeth, Shree Mahakali, and the Rayatwari collieries which are also located in this area are working different sections of the seam. The coal is non-coking and ungraded. The local reserves within the leased out areas of the four concerns have been estimated to be about 262 million tonnes.

(2) Warora-Manjri area.-Two seams are known to occur near Warora, the upper one being 4.60 m and the lower 3.00 m thick. In the Manjri area there is a 10.00 m thick seam, the bottom (3.70 m.) of which had good quality coal, whereas the upper portion is shaly. The total reserves in the area are estimated to be of the order of 32.5 million tonnes.

(3) Sasti-Rajura area.-The thick seam of Ballarpur area extends south of the Wardha river into this area where it is being worked into two sections by the Sasti colliery. The thickness of the seam in this area is about 10.70 m. About  154.6 million tonnes are estimated to be present in the leased areas.

(4) Rajura-Wun area.-All the workings in this area have been abandoned long ago and very little information is available. However, from the boring put down as far back as 1877, it is reported that 8.23 - 9.45 m. thick seam occurs at Pisgaon and 5.49 - 9.14 m thick seam at Rajura. The reserves in the area are estimated to be of the order of 330.22 million tonnes.

(5) Ghugus-Telwasa area.-The total thickness of the seam that is being worked at Robertson incline of the Ghugus colliery is 11.21 m. The coal seam trends north-north-east and south-south-east and dips 8° towards west-south-west. The reserves in colliery-lease area are estimated to be about 198 million tonnes.

Thus the total reserves in all the above areas are about. 985 m tonnes. A large terrain covered with Kanthi rocks to the cast of the existing lines of the collieries near Chandrapur and Ballarpur and the area west of Ghugus is considered potentially coal-bearing.

Besides this, records of earlier drill-holes indicate the existence of a 12.19 - 21.24 m thick seam between Manjri and Nawkawada. The coal from this area is non-coking and high in moisture. There are two collieries working, one at Ghugus belonging to Messrs. Ballarpur Collieries Ltd. and the other at Manjri belonging to Manakji Dadabhoy. During mapping of an area of 363 km² (in Sheets 551/16, 55 p/4 and 8,561 /B, 56 M/1, 5, 6, 9 and 10) on areal photos, besides other rocks the Barakar rocks were recorded having strike varying between North 15° West and North 25° West with easterly dips of 8° to 18°. On Kondayai-Ka-Pahar a 4.5 m section of a coal seam was found exposed. Here the beds strike North 70° West-South 70° East and dip at 18° towards south-west. Co-relation of the different working sections of the five collieries in the area indicates the existence of a 15.24 metre thick seam in the area between Durgapur and the Wardha river on the south.

The coal from this area has high moisture (10.3 to 11.3%) and is of grade II. The collieries are raising about 35,560 tonnes of coal per month.

Copper.-The occurrence of malechite has been recorded at Thanwasana in stray traces in quartz veins, traversing phyllitic quartzites and argillaceons sand stones. As the bulk of this vein-quartz is barren, the occurrence does not appear to be promising. The copper-ore near Govindpur village occurs in a small quartz reaf but is not of any economic value.

Lead-ore.-A few pieces of very small crystal of galena were found on the surface near Padmandadda nala.

Building and Construction materials.-Granite, Vindhyan sand-stone and quartzite, limestone, Gondwana sandstone and basalts of Trappean age can yield substantial supplies of material for being used in buildings and roads etc. Vindhyans are a good store-house for building stones in Pipalgaon area. The sandstones are suitable for all sorts of building purposes and are extensively used locally. Brecciated quartzites are good sources for road ballast. Massive lateritic is also used in the area as building stone.

The Kamthi sandstones quarried in the reserved forest area, about 4 km. to the south-west of Karanji are curved and trimmed into water tubes. Kamthi sandstones near Bhutara Hill and Isapur are used for building purposes. One of the finest display of the application of the Kamthi sandstone for building purposes is in the walls of the town of Chandrapur about 9 km in circuit. The sandstone of the lower portion of the Kamthis present special facility for dressing, being soft when first quarried and hardens on exposure. The compact pink-coloured argillaceous sandstone of Isapur, furnish splendid material for illustrating the fine tracery work that Indian skilled artists are capable of carrying. At Lalpeth near Chandrapur there are some massive monoliths of gods and demons; but the religious tendency of the past expressed itself more specially by hewing out temples in solid rocks. Many of these carved temples are at Bhandak, Winjhasar, Deolwara, Ghugus and Chikli.

Limestone.-Limestone occurs 0.4 km. north-north-east of Purkepar village, about 6 km east of Nawargaon. The occurrence is 16 km west of Alewahi railway station. The stone is fine grained and pink in colour. Limestone also occurs at Mardha and dolomite at Niljai. Limestone extending over several square kilometres in Chandrapur district, may yield many million tonnes, but the limestone does not appear to be of any commercial importance, because of its impure seliceous and lateritic character. However, some of the massive quartzites occurring between Somanpalli and Dongargaon may be analysed so as to assess their suitability for commercial purposes.

Clay.-Occurrences of several pits of white clay have been recorded in reserved forest area on both sides of the Chandrapur-Allapalli road, about 1.6 km. east of Kothari. The clay occurs in patches of varying sizes; some of them measure about 83,613, 33,445, 16,722.5 and 8,361 sq. metres in extent. Another fairly, big patch is seen along the Kuklai nala. The quality of the clay is variable from deposit to deposit. Colour varies from pure white to various tints of brown and red. The pure white variety gives a whitish to greyish colour after firing. The plasticity is variable and the clay stands up to 1300 c. Shrinkage varies from nil to 5 per cent. The reserves are estimated at 921,000 tonnes. Parts of the area having this clay have been leased out.

In the collieries worked near Chandrapur town from Durgapur to Lalpet, a fire clay bed occurs varying in thickness from 1.50- 3.70 m. The felspathic Kamthi sandstone near Bhandak has decomposed sufficiently, for the clay resulting from the alterna- tion of the constituent felspars to be concentrated by levigation and washing and is being used in local potteries for the preparation of earthenwares. Following occurrences of fire-clay in the Kamthi sandstone of the Wardha Valley coal field have also been noted: (1) near Isapur clay is found in an area measuring about 365 m in length and 68.6 m in width, (ii) about 1.6 km north of Ballarshah, there are several small pits where clay is being quarried, (iii) 4 km. west of Junana there is a patch of clay measuring about 91.0 m in length and 18.0 m in width in the forest, (iv) a small patch on the western outskirts of Kothari; (v) an outcrop of white clay near Katali on the bank of the Wardha river, and (vi) an exposure in a railway cutting near mile post 765 on the narrow gauge of the Bengal-Nagpur Railway.

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