Which types of rocks are found in Rajasthan?
Answers
Answer:
lumion rocks are found in Rajastan
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Answer:
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Explanation:
Jodhpur Group-Malani Igneous Suite Contact of Aravalli range is a geological feature representing the last phase of igneous activity of Precambrian age in the Indian Subcontinent at the foot of the picturesque Mehrangarh Fort in Jodhpur city, the second-largest city in Rajasthan after Jaipur.[1]
The uniqueness of the geological feature at Jodhpur prompted the Geological Survey of India (GSI) to declare the site as a National Geological Monument.[2]
Malani Igneous Suite, an integral component of the Thar Desert in Rajasthan, extends at the periphery of the desert, to an area of 44,500 square kilometres (17,182 sq mi) covering parts of Pali, Sirohi, Jodhpur, Barmer, Jaisalmer, Jalore and Siwana districts of western Rajasthan.[3] In particular, a rhyolite rock exposure in a hillock of 120 metres (394 ft) height, originally called the "Mountain of Birds", forms the foundation for the imposing Mehrangarh Fort in Jodhpur.[5] The climate here is of the extreme desert condition of scorching summer with hot dry winds and arid conditions. The winters are quite chilly. The rainfall is scanty and occurs from late June to September. The average rainfall is reported to be 360 millimetres (36 cm); extremely variable with a minimum record of 24 millimetres (2 cm) during the famine year of 1899 and a maximum of 1,178 millimetres (118 cm) during the floods of 1917. [6]
Geology
The lithological formations of the region classified as upper and lower Vindhyans in the east and Marwar in the west have been recorded as consisting of a thick series of sedimentary rocks comprising sandstone, limestone and shales. Igneous activity preceded the deposition of these rocks in western Rajasthan in the form of a thick pile of lava, mostly of an acidic nature. This lava and its plutonic equivalent have been noted in the form of granite bosses and sills in Jalor, Siwana, Mokalsar and Jodhpur areas and designated as Erinpura granite and Malani Igneous Suite (pictured).[7]
Mehrangarh Fort section in Jodhpur exposes the best Jodhpur Malani Suite contact. This erosional contact is between the underlying youngest Igneous suite of rocks of Precambrian age and overlying oldest sedimentary sequence of late Proterozoic to Eocene age.[2] Its geological significance led to it being declared a National Geological Monument.[1][2]
The igneous cycle has three phases namely, the volcanic, plutonic and hypabyssal. The eruption is reported to be of fissure type. The pyroclastic exposed in a thickness of 40 metres (131 ft) to 50 metres (164 ft) is followed by rhyolite flows of 50 metres (164 ft) to 60 metres (197 ft) thickness.[2]
Sandstones of Jodhpur Group form the basal part of the Marwar Supergroup and the upper boundary of these volcanic is considerably eroded. The two formations called the Sonia Formation (sandstones) and the Girbhakar Formation (sandstones) occur unconformably over the eroded surface of Malani Volcanic rocks at the top, which comprises the Pokhran Boulder Bed (developed locally around Pokhran) with the Jodhpur Group as the basal part. The sandstones are creamy (reddish maroon upwards), and widely used as building stones.[2] Further classification of the Malani Igneous Suite has been done by Bhushan (1991) as Granite Plutons (at least 15 varieties including the Jodhpur Rhyolites), the Siwana Granites (several plutons covering an area of 1,100 square kilometres (425 sq mi) within the Malani Igneous Suite) and the Jalore Granite (covers an area of 7,600 square kilometres (2,934 sq mi) including 3,700 square kilometres (1,429 sq mi) of Sankara pluton).[3]
Geological age
The geological age of the Malani Igneous Suite assessed by several geologists vary. Crawford and Compston (1970) assessed the age by Rb-Sr classification as 745 ± 10 Ma. They also reported, in 1975, that the Isochron age was 735 Ma which was less than the age of 840 Ma for Sandra Granite, 830 Ma for Erinpara Granites and 820 Ma for the Pali Granites.[3] But the Geological Survey of India in its publication National Geological Monuments (2001) has given the age as 600±70 Ma.[2] IF HELPFUL PLEASE MARK AS BRAINLIEST IT'S A VERY HUMBLE REQUEST ( only if you liked my answers or it's fine no problem)