East Rajasthan-Mahabharat Plateau of Peninsular Uplands

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East Rajasthan-Mahabharat Plateau (72°7′ – 79° 5’E and 23° 20′- 28° 20′ N) occupies an area of about 1,67,872 sq km. in eastern Rajasthan, north­western part of Madhya Pradesh and a small part of Gujarat (parts of Banaskantha and Sabarkantha dis­tricts). Geologically the region forms part of the Archaean shield of the Peninsula which consists of the well-foliated, highly contorted and faulted gneissic basement complex.

The main rock formations in­clude the Dharwarians (Aravallis) and the Vindhyans separated by the 800 km long Great Boundary Fault (roughly parallel to the course of the Chambal). The Aravallis represent a synclinorium containing argillaceous deposits, metamorphosed from shales through slates and phyllites to mica schists.

The region appears to have undergone peneplanation in the later Mesozoic and subsquently it experienced warping. A second stage of peneplanation occurred during the Tertiary and Pleistocene whereby the regional relief was greatly subdued.

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The region has a varied topography, showing traces of peneplanation, warping, intrusion and de­formation. Physiographically the region may be divided into two units: (i) the Aravalli range, and (ii) the Eastern Plains.

The Aravali which runs from north-east to south-west, for about 800 km between Delhi and

Palanpur (Gujarat) represents a relic of one of the world’s oldest fold mountain systems. The main hills lie in Rajasthan having an imposing relief south-west of Ajmer. However, they fan out in parallel series of low ridges, north-west of Jaipur towards Haryana. The range is mainly composed of quartzites, gneisses and schists of the Precambrian times. In the north it is less than 400 m in height and is crossed by many rivers.

The range becomes more continuous and rising to above 900m inthe south. Its highest peak lies in Abu Hills (Gurushikhar Peak 1722 m). The Aravallis are highly eroded and dis­sected. However, the crystalline limestones and quartz­ites rise sharply above, forming hogback ridges.

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The Aravallis formed a great mountain chain in the Precambrian period extending from the Himalayas in the north to Lakshadweep in the South. But due to long period of erosion these have been reduced to low hills (304-914 m). North-west of Udaipur these are called Jarga hills (1431 m), between Kumbha and Gogunda as Bhorat Plateau (1225 m) near Tod as Merwara Hills, the detached Abu Plateau (1 km, height 1200 m) and the Delhi ridge in extreme north.

The Eastern Plains include the lowland the Chambal basin, the Banas Plain and the mid| Mahi orChappan Plain. Here Banas Plain, thougl alluvial tract, is rather a peneplained. The middle Plain is a tangled wilderness of valleys knowi I Chappan.

The Plains of the Chambal-Sindh Bai present rather a homogeneous topography chan I I tensed by Hood plains, river bluffs, interfluves ravines which are well developed in this area.ThiH ravines occupy about 4500 sq km of area in Km Bundi, Tonk, Sawai Madhopur, Bharatpur I ^^H Rajasthan), Morena, Bhind and Gwalior (Madh It Pradesh) districts. Severe gullying, possibly in ated by rejuvenation but aggravated by misuse of land, make this perhaps the worst area of erosionB India, particularly towards the edge of the forelan (Spate and Learmonth, 1967, p. 622). Most of the erosion and ravine formation has occurred durin the last 400 years due to reckless deforesation aw I faulty land use practices.

The Banas Plain is demarcated by 50 en is hoyed in the west and the Vindhyan scarp in the cast. Drained by the Banas and its tributaries the plain may be called Mewar plain in the south and Malpura-Karauli pi ain in the north.

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The Mewarl plain is a dissected plain of Archaean gneiss. The I Middle Mahi plain has comparatively steeper gradi-1 (8-12 cm/km) with an average elevation of 200- f 400 m. It is deeply dissected and is locally known as Bagar.

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