महाराष्ट्र जलभू्शास्त्र

Archeans :

The Archeans are the oldest the rocks which are metamorphosed. They comprise rock formations called the older schists and the unclassified crystallines which are overlain by the metasediments of Dharwar system and the intrusives such as Granite, Diorites etc. The unclassified crystalline include various Gneisses which occur in Nagpur, Bhandara, Chandrapur, Gadchiroli and Sindhudurg districts. The Proterizoic metamsediemnts are divided in to three different series namely Sausar, Sakoli and Iron ore series.

Sausar Series:

The Proterozoic metasediments of this include a variety of rocks such as Calogranulites, Calciphyres, Quartzites, Geisses, Schists, Manganese bearing Gondites etc. Structurally these group of metasediments are intensely folded and faluted, these subjected to a number of tectonic events.

Sakoli Series :

The Sakoli group of rocks consists of Pelitic, Psamopelitic and Metabasic sediments. These include Quartzites Phhyllites, Amphibolites, Schists and associated volcanics.

Iron Ore Series :

It constitutes the important iron ore deposits of Gadchiroli and Sindhudurg districts. The rock are Quartzites, Banded Hematite Quartzites, Schists and Phyllites. The rock and associated iron ore deposits occur in Chnadrapur, Gadchiroli and parts of Nagpur and Bhandara districts.
These have been intruded on a very large by Granites and basic intrusive, and vast areas of Chandrapur and Bhandara districts have been occupied by Granites, Granitoid Gneisses etc. At the southern tip of Sindhudurg district, these comprise Schists, Phyllites, Agrillites, Banded Hematite Quartzites with basic intrusion and from separate patches striking NNW-SSE.

Archeans :

The Archeans are the oldest the rocks which are metamorphosed. They comprise rock formations called the older schists and the unclassified crystallines which are overlain by the metasediments of Dharwar system and the intrusives such as Granite, Diorites etc. The unclassified crystalline include various Gneisses which occur in Nagpur, Bhandara, Chandrapur, Gadchiroli and Sindhudurg districts. The Proterizoic metamsediemnts are divided in to three different series namely Sausar, Sakoli and Iron ore series.

Sausar Series:

The Proterozoic metasediments of this include a variety of rocks such as Calogranulites, Calciphyres, Quartzites, Geisses, Schists, Manganese bearing Gondites etc. Structurally these group of metasediments are intensely folded and faluted, these subjected to a number of tectonic events.

Sakoli Series :

The Sakoli group of rocks consists of Pelitic, Psamopelitic and Metabasic sediments. These include Quartzites Phyllites, Amphibolites, Schists and associated volcanics.

Iron Ore Series :

It constitutes the important iron ore deposits of Gadchiroli and Sindhudurg districts. The rock are Quartzites, Banded Hematite Quartzites, Schists and Phyllites. The rock and associated iron ore deposits occur in Chnadrapur, Gadchiroli and parts of Nagpur and Bhandara districts.
These have been intruded on a very large by Granites and basic intrusive, and vast areas of Chandrapur and Bhandara districts have been occupied by Granites, Granitoid Gneisses etc. At the southern tip of Sindhudurg district, these comprise Schists, Phyllites, Agrillites, Banded Hematite Quartzites with basic intrusion and from separate patches striking NNW-SSE.

Pre-Cambrian Puranas :

The Archaean rock are overlain by the pre-cambrain or the Purana formations which are divided into two major system namely the Cuddapah and the Vindhyan system.
The Cuddapah rocks, which are mainly Crystalline Limestone, occupy a small areas in the southern part of Gadchiroli district. The rock formations refrred toas kaladgis (equivalent of Cuddapah) rest directly on the Archean rocks in Sindhudurg district. Formerly these had apparently occupied a very large area which is now covered by the Deccan Lava flows. These rocks comprise mainly of Quatzitic Sandstones and Shales and have give rise to important deposits of Silica sands.
A vast areas, in the districts of Nanded, Yavatmal, Chandrapur and Gadchiroli, is occupied by the rocks of Vindhyansystem consisting of limestones, Dolomitic Limestones, Purple Shales and Feldspathic Sandstone.

Gondwana System :

The coal bearing Gondwana sediments were deposited in riffed basins formed by the rejuvenation of the south in central India. The sedimentary rocks belonging to the Gondwana system can be divided inti two groups namely the Lower and the Upper.
The Lower Gondwana sediments include the Talchir series, the oldest group of rocks belonging to this period, followed by Barakar series, kamthi series and Mangli beds.The Talchir series include seriated boulders and green shales, sandstone, clays and mudstones were deposited during the glacial period.The Barakar series consists of a thick succession of alternate layers of sandstones, shales with interbeded coal seams.The youngest group of rocks belonging to the lower Gondwana sequence is known as the Mangli beds and consists of conglomerates, grits and hard sandstones and are seen in warora taluka of Chandrapur district.The upper Gondwana sediments include Pachmari, Maleri, kotta and Chikils group are mainly seen in Sironcha taluks of Gadchiroli district. Around Bairamghat in Amravati district, the Pachmari group of sediments are exposed. It consists essentially of sandstone, shales and clays and includes number of plant fossils.

Lameta and Bagh Beds :

The rocks formations referred to the Bagh Beds are exposed along the southern bank of Narmada river in Akkalkuwa taluka of Nandurbar district and comprise of siliceous limestones and sandstones. The Lanetas are Infra-trappean beds which comprise calcareous sandstone, cherty limestones and calys. The are located at various places and along the fringes of the Deccan Trap as near Nagpur and in Amravati district.

Deccan Trap :

The basalt lava flow called as the ‘Deccan Trap: were formed as fissure eruptions with a time lag between two volcanic episodes, which wre marked by the deposition bybthe fresh water sediments known as intertrappean.
The Deccan Trap are the important geological formation in the Indian sub-continent. In Maharashtra State, it occupies an area of about 2,46,784 sq.kms, which is about 82% of the State. It is found in all the districts of the state excepted Bhandara. It occurs upto a height of about 1636 meters A.M.S.L. and to considerable depth below sea level. It is a vast pileup of volvanic products such as tuff, breccia and ash beds.
The Deccan Trap lava flow can be broadly divided into the following major physical units:
1. Massive and Compact,
2. Vesicular
3. Amygdular or Zeolitic
4. Jointed or fractured and brecciated.
The lava flow are often associated with beds of pyroclastic and sedimentary origin. The sediments associated with the lava flow are known as inter-trappean beds, which consists of sandstones, clays, limestones or charts. Another conspicuous layer associated with the lava flows is the clay like material known as sred-bole. These lava flows are sometimes intruded by the intrusive dykes which may cut across a number of flows and form an important physiographic feature.The Deccan Trap lava flows have been erupted from long narrow fissures and have great areal extent in comparison with the thickness.The individual lava flow varies greatly in thickness from a few metres to as much as 30-35 metres. The thickness of these lava flows is maximum in the western part of the state where it is reported to be of the order of 3000 metres. These flows have been completely thinned out to the east, near Nagpur.

ALLUVIUM –

The alluvial deposits generally occur along the lower reaches of major river valleys and along the coastal areas. However, such deposits are not well developed in the State. Two well known alluvial deposits namely, a Tapi Valley (districts of Dhule and Jalgaon) and the Purna Valley (districts of Buldhana, Akola and Amravati) are recognized. These alluvial deposits belong to slightly older period in geological history then most of the alluvial deposits in the coastal areas of the country. These are referred to as older alluvium. The alluvial deposits in the Tapi and Purna valleys occur in separate, rather, long narrow basins and occupy a total area of 10,500 Sq.Kms. of which Tapi covers an area of 4100 Sq.Kms. and Purna covers 6400 Sq. Kms.On the basis of exploratory drilling, it is known that, these alluvial deposits attain considerable thickness, maximum being about 425 metres and it is in the northern part where the basement has been faulted.The alluvial material in these two basins consists of boulders, cobbles, pebbles and gravels referred to as boulder alluvium.Minor alluvial deposits are also known to occur in other parts of the State such as along Bhima, Godavari, Wardha, Wainganga, Penganga rivers and also some along their tributaries.

14. Hydrogeology of Maharashtra –

Groundwater occurs in the pores and interstices amongst the grains in the Rock formation and in joints, fractures, fissures, cracks and other forms of openings in the geological formations. The size, number, nature, amount of interstitial space and relationship amongst them vary widely in different geological formations. Groundwater occurs and moves through the interstitial space in the various strata under two broad conditions, namely, water table condition and confined condition. Groundwater occurring under water table condition is met with at relatively shallow depth and is withdrawn by dug wells.Tube wells, borewells and dug-cum-borewells generally tap groundwater occurring under confined and semi-confined conditions in the water bearing strata.