PHYSICAL FEATURES AND NATURAL RESOURCES

[The section on Geology is prepared by Shri Y. S. Sahasrabudhe of the Geological Survey of India.]

GEOLOGY

TWO DISTINCT TRENDS IN THE HILL RANGES are seen in the district. One runs roughly north-south, along the main range of the Western Ghats presenting wild and picturesque hill slopes and valleys. The other one comprises the narrow broken-crested ridges and flat topped masses stretching eastwards and merging gradually into the plains in the east. The rivers Hiranyakeshi, Vedganga, Dudhganga, Bhogvati and Panchganga drain the area towards east.

The geological formations met with, in the descending order of their antiquity, are as follows: -

The Dharwar phyllites and amphibolities intruded by granite-gneiss are the oldest rocks found as small inlairs in this district. Phyllites and amphibolities are noticed near Ajra. The phyllites are completely weathered and have formed variegated clays. The amphibolities are dark, markedly schistose and break into thin slabs. Granite-gneiss crops out as four small inlairs along the junction of the Kaladgis and the Deccan trap near Hadalge, Nesri, Tarewadi and Chandewadi. It shows diversity of texture from a fine grained to a rather course porphyritic type. A number of basic inclusions are noticed in the granite-gneiss.

The earliest reference to the geology of this district is by R. Bruce Foote, entitled " The Geological Features of the South Mahratta Country and adjacent districts," published in Mem. Oeol. Surv. Ind., Vol. XII. Pt. 1, 1876. C. S. Fox has given an account of the bauxite deposits of the district under the heading, "The Bauxite and Aluminous Laterite Occurrences of India," in Mem. Geol. Surv. Ind., Vol. XLIX, Pt. 1, 1923. A more comprehensive idea of the geology of the district is furnished by H. C. Jones under the caption of " Mineral Resources of Kolhapur State," published in Rec. Oeol. Surv. Ind., Vol. LTV., Pt. 4, 1923. Recently K. C. Channabasappa re-examined the bauxite deposits of the district and his observations are recorded in an unpublished report (1949). A reference to the utilisation of the deposits is contained in B.C. Roy's paper entitled " A note on the utilisation of Belgaum and Kolhapur bauxites, " in Indian Minerals, Vol. IV, No. 2, April, 1950.

The Lower Kaladgi series, next in the chronological order, rest unconformably over the Dharwars and the granite-gneiss. It consists of conglomerates, compact to gritty quartzites with minor ferruginous bands and stains, variegated and sandy-shales and re-crystallised sandstones. The strata are almost horizontally disposed, but gentle dips of 8 to 10 degrees towards N. to N.N.W. are also noticed. The Kaladgi rocks are well bedded, the thickness of the individual beds varying from a few inches to 20 feet or more. They show frequent changes of the grade of the material throughout the formation. Conglomerates occur at various levels. Fine to coarse grained quartzites frequently alternate. Pebbles are scattered both in the sandstones and quartzites. The outcrops are seen along the V-shaped western margin of the main Kaladgi basin near Hadalge, Nesri and Watangi in the Ghatprabha river valley. They form small inlairs in the valleys of Vedganga, Dudhganga and Hiranyakeshi rivers.

An oval-shaped inlair of the Lower Kaladgis is noticed in the Hiranyakeshi river valley. It extends from north of Ajra in the west to Mahagaon in the east and covers an extensive area. The rocks are represented by quartzites and shales, mostly dipping north-west, at low angles. They are best exposed in the row of hills which runs east-south-east near Sulgaon on the bank of the Hiranyakeshi river. The quartzites and shales form a series of beds several hundred feet thick, although both top and bottom of the Kaladgis are hidden under the trap. The prolonged denudation of the trap has also given rise to a small inlair near Madilge 4 miles north of Ajra. Five inlairs are noticed in the Vedganga valley. Two of them are near Shengaon and Sheloli and cover an area of about two and five square miles respectively. The inlair near the Shengaon is an elongated hill rising about 400 feet above the plains. The Sheloli inlair comprises two hills about 450 feet in height and is separated by the Vedganga river. The rocks are re-crystallised sandstones and quartzites with ferruginous stains with a dip towards east and south and south-east at 8-10 degrees. The other three inlairs, near Sonarwadi, Salpewadi and Hanabarwadi represent intermittent exposures along the eastern flanks of the great ridge of the Deccan trap, south-east of Gargotti. Another small inlair of the same rocks occurs in an adjacent valley three miles west of Shengaon near Phaya. The rocks attain a thickness of about 400-500 feet. The two inlairs near Waki and Aini along the Dudhganga valley cover an area of about ten and three square miles, respectively. The eastern boundary of the Waki inlair runs about six miles along the western flanks of the great ridge from Ghothana in the south to Sutarwadi in the north and forms a low-lying plateau north of Waki. The quartzites and sandstones are whitish, drab or pinkish in colour and fine grained in texture. They dip at 8-10 degrees in different directions but south-easterly dip being the most common. The continuation of the same rocks further north of Waki inlair forms the Ani inlair. The beds here dip at comparatively low angles, varying from 7-10 degrees, and attain a thickness of about 300 feet from the level of the river. The eastern boundary runs along the western flanks of the ridge near Ani and Alegaon, while the western boundary is along the eastern slopes of the ridge near Lingewadi and Panori.

The Deccan trap formation overlies the Kaladgi beds and is seen spread over almost the entire district. It occurs in the form of bedded flows, several thousand feet in total thickness. The greatest thickness of the trap within the south Kolhapur area may roughly be estimated at 2,000 to 2,500 feet. The individual flows vary in thickness from a few feet up to 100 feet or more, the average thickness being about 40 to 50 feet. They are seen to dip at a very low angle generally to the north-east while it changes to low westerly dip in the Konkan. A great part of the lava-beds must have been subjected to large scale erosion along the river valleys, exposing the underlying Kaladgi and Dharwar group of rocks. Because of their tendency to form flat-topped plateaus and terraced features, they are described as "traps". They are dominantly basaltic in composition and are equivalent to the " plateau basalts". The rock is dark grey to greenish-grey in colour, although brownish to purplish tints are also met with. The specific gravity is 2.9 on an average.

The Deccan trap exhibits characteristic spheroidal weathering and forms rounded boulders. These boulders are generally seen scattered along the foot-hills of the hilly terrain throughout the whole district. Prismatic or columner jointing is also a common feature. Generally two types, viz., vesicular and non-vesicular traps are noticed. The vesicular or amygdular types are comparatively soft. The non-vesicular types are hard and compact. Generally in the trappean country, fluviatile and lacustrine deposits are formed during the interval between the successive lava flows. These deposits are known as the inter-trappean beds and consist of sandstones, shales, clays and pyroclastic materials.

Petrologically, the Deccan trap consists of plagioclase (labradorite), enstatite-augite, and small amounts of titaniferous iron-ore and glass. Olivine is also found at times. In the amygdular variety, the vesicles are partly or completely filled with secondly minerals like zeolite, calcite and crystalline and amorphous quartz (rock crystal, chalcedony, agate, jasper, etc.).

The lava beds at the plateau tops are capped by laterite, a product of weathering. Laterite is usually noticed at altitudes of 3,000 feet or more throughout district. The thickness of the laterite, forming vertical cliffs or scarps, usually varies between 20 and 100 feet. It is a kind of scoriaceous and variegated clayey rock, with characteristic red and brown colour, and is composed essentially of hydrated oxides of alumina and iron. Rich aluminous varieties of laterite known as bauxite occur as; irregular pockets or layers.

Two types of soils are noticed. Alteration of the trap gives rise to a deep brown, red or black-soil, covering a large area of the district. The Kaladgi sandstones and quartzites on the other hand yield a reddish sandy soil particularly noticed in the southern portion of the district.

Bauxite.

This is the chief mineral of economic value in the district. It occurs in large quantities as laterite cappings in the hills along the western margin of the district. Some of the occurrences are described below.

Radhanagari deposits.-The largest deposits are seen about 4 miles north of Radhanagari, on Kolhapur-Phonda-Ghat road, and are accessible by a foot-path from Radhanagari dam site. The plateau tops here show a capping of 60-80 feet of laterite. The spur of the hill culminating in peak Δ 3244, north-west of Radhanagari, is capped by aluminous laterite. The southern slopes are covered by laterite debries with some bauxite, as seen in the nala sections near Mosalavadi. The high ground in the middle of the triangular plateau Δ 3244 is capped with 1-2 feet of ferruginous laterite underlain by massive bauxite varying in thickness from 5-13 feet. It is estimated that about 10,80,000 tons of bauxite may be available in addition to a few thousand tons of float ore. The chemical analyses of a number of samples gave the following range in composition: -

SiO₂-Silicon di Oxide.

Al₂O³-Aluminium Oxide.

Fe₂O³-Ferrous Oxide.

MgO-Magnessium Oxide.

CaO-Calcium Oxide.

TiO²-Titanium di Oxide.

The plateau attaining a maximum height of Δ 3252 west of hill Δ 3244, is also capped by laterite and contains grey bauxite about 3½ feet in thickness. The two isolated hillocks and the plateau (Δ 3218) north of hill Δ 3244 show the patchy development of bauxite. About 96,300 tons of bauxite may be expected from these plateaus. The samples show the following range in composition: -

Panhala Fort deposits.-These are found about 12 miles north-west of Kolhapur. Capping the plateau there is a 30-40 feet thick laterite. It is only in the shallow valley below Bagh Darwaja, north of Shivaji's tower, kaolin and pisolitic bauxite are noticed. The quality seems to be good but the quantity is poor.

Bhudargarh deposits.-There is a series of laterite capped hillocks, 4 miles south of Gargotti, on the Kadgaon-Nipani road. The laterite is highly ferruginous, approaching a low grade iron-ore. The hillocks are generally capped by a 30-40 feet thick ferruginous laterite containing a few bouldery pockets of grey and buff coloured bauxite.

Amboli-Ghat deposits.-Two parallel ridges, situated at the tri-junction of Kolhapur-Belgaum and Sawantwadi, contain laterite 50-100 feet thick, with a thin capping of bauxite at the top. The slopes of the ridge are sometimes strewn with float ore. Two important float ore deposits are confined to the north and north-west of the western ridge, the average thickness being 2 feet. The western ridge is capped by a more massive bauxite, having its thicker side facing the Hiranyakeshi valley. The eastern ridge, consisting of less massive ore, has its thicker side facing the Ghatprabha valley. The laterite on both the ridges in general, is aluminous, with lens-shaped patches of grey bauxite of good quality. The massive cliff of the western ridge shows several such patches, along the length of the ridge. It is estimated that about 44,21,340 tons of bauxite will be available in the western ridge and about 9,80,100 tons on the eastern ridge. The float ore may be of the order of 2,05,000 tons. The analyses of samples gave the following range in composition: -

Plateau West of Dhangarvadi.-The extensive plateau culminating in peak Δ 3335, approximately striking N.W.-S.E. overlooks the main road from Kolhapur to Ratnagiri via. Amba Pass. The rim of this plateau is bounded by lofty scarps on all sides. Boulders of good quality bauxite are seen in abundance on the northern slope, while they are comparatively rare on the southern and western slopes. The scarp sections south and west of Dhangarwadi show 12-15 feet of massive bauxite, whereas in the northern cliff it has a thickness of 36 feet. The quantity of bauxite on the south-eastern portion of the plateau (Δ 3335) is of the order of 59,40,000 tons. In addition about 5,00,000 tons of float ore are available on the northern slopes of the hill Δ 3335. Samples analysed yielded the following range in composition: -

Rangevadi deposit.-A group of discontinuous plateaus south of Rangevadi are bounded by scarps, attaining a maximum height of 40 feet at the north-eastern corner. The boulders of aluminous laterite seen at the top gradually improves in quality from west to east. The scarp sections at the southwestern corner show 12 to 15 feet of massive bauxite passing down to vermicular laterite, while the scarp sections due south of Kadakawadi, where the plateau narrows down to a width of 50 yards expose 2 to 3 feet of limontic material underlain by 23 feet of massive bauxite. It is estimated that about 32,40,000 tons of bauxite would be available. The samples analysed gave the following range in composition: -

Ridge West of Nesari.-This ridge which runs along the, Belgaum-Kolhapur boundary, 6 miles west of Nesari, has a capping of 40-60 feet of laterite. The examination of scarp sections and the slopes indicates only sporadic patches of massive bauxite.

Gargotti deposits.-The two small hillocks near hill Δ 3239, west of Gargotti are capped with aluminous laterite approaching bauxite in composition. Boulders of good grey bauxite are strewn near the village Dhangarvadi. The thickness of the bauxite varies from 8 to 10 feet and the quantity available is approximately 5,40,000 tons. The samples analysed yielded the following range in compositions: -

Waki deposits.-The peak Δ 3372, four miles south-west of Waki, is capped with aluminous laterite, about 60-80 feet in thickness. The slopes and sides of this hill are strewn with bounders and nodules of ferruginous laterite and on the western margin from south to north, grey bauxite of good quality is seen on the top. The scarp sections at the western side show 4-8 feet of massive bauxite passing downwards into laterite. The quantity of ore is estimated at 13,50,000 tons. A sample collected at the eastern margin analysed as follows: -

Udgeri deposits.-One of the best deposits occurs on the plateau Δ 3396, about half a mile north-west of Udgeri. The main plateau consists of a bedded basalt with a capping of 60-80 feet of laterite. The southern slopes, especially above Udgeri, are largely covered with bounders of bauxite, while they are rare on the northern slopes. Practically the whole of the north-western part of the plateau consists of good quality bauxite and in contrast the south-eastern portion does not appear to be so rich. Proceeding along the foot-path from Udgeri towards north, the scarp section sat the southern side show 15 feet of massive bauxite. The cliffs near Δ 3396 show 22 feet of grey coloured bauxite. The scarp sections north of the tank at the north-western corner of the plateau show 2 feet of laterite capping a 32-foot of massive grey bauxite. The estimated reserves in the above locality are about 35,64,000 tons of bauxite. Samples analysed gave the following range in composition: -

Total Reserves.-Summing up the probable reserves of the more aluminuous laterite from all the above deposits are of the order of 2,10,00,000 tons, out of which about 10 per cent, can be considered to be good quality ore.

The deposits are located on the plateau tops and offer some difficulty in transporting the ore. it can be brought to the foot-hills by gravity or alternatively by a system of aerial ropeways for haulage could be arranged to reach the ore to the main high-way of the district such as Phonda Ghat road, Gargotti road and Ajra-Amboli Ghat road, all of which are within 5 miles from the deposits. Although there appears to be no serious difficulty for transporting the ore, the charges may be rather high. But with improved transport facilities and cheap power being made available the commercial exploitation of the bauxite deposits in Kolhapur should become possible.

Building Materials.

The district is well endowed with building stones. Hard, compact, fine to medium grained Kaladgi sandstones and quartzites are quarried for construction materials near Nesri, Harur, Gajargaon, Ajra and Gargoti. They are also worked for road metal near Harali Budrukh and Harali Khurd. Some of the harder varieties of Deccan trap are extremely good for building purposes and are worked in the Jotiba hill quarries. The rock is fine grained, hard, compact, bluish-grey and can be traced up to the Panhala fort and along the range for many miles. It is also quarried near Ajra, Gandhinglaj, Gargotti, Kagal etc.

Laterite.-Laterite is abundant and has been largely used for walls and buildings in many of the old forts and is still used in many of the villages in the district. Irregular nodules of kankar occur in the soil, especially in the eastern part of the district, and is locally used for lime-burning.

Copper.-Traces of thin films of metallic copper are reported in some excavations in the trap near Kolhapur and also in a railway cutting 11½ miles from Kolhapur. These are of academic importance only.

Gypsum.-Some irregular nodules of fibrous gypsum found in red clay are reported near Tambiyadi. This has no economic value.

Iron.-Fair quality iron-ore occurs in small quantities in the laterite throughout the district but is useless at present as source of raw material for smelting.

Kaolin.-Small quantities of inferior type of kaolin are noticed near Panhalla fort, Gudalkop, Gadhinglaj and Budargarh fort, but these occurrences are not important economically.

WATER SUPPLY.

The district may be divided into three belts as regards its water supply, viz.. the hilly and rugged country forming the Western Ghats towards west, the narrow broken-crested ridges stretching eastwards in the central portion, and the plains towards east. The hilly country in the west receives the maximum rain-fall of the district and the ground water is mostly tapped from percolation wells and mountain springs. In the Central portion the water supply is partly from springs and wells, the main source being the five perennial rivers. The plains have copious surface and underground water supply and may be said to be one of the best irrigated lands of the State.

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