Geology of Udaipur

History Of Udaipur

Udaipur, the capital of a princely state of pre-independence time is perhaps the only place in India where artists, historians tourists, naturalists, geoscientists get a lot to fulfill their interests. Glorious history of Mewar echoing from all corners on one hand and the scenic beauty of the city and still waters of its fascinating lakes surrounded by Aravalli hills on the other stun a visitor. Rocks carving this blissful valley easily turn a geoscientist into a philosopher. Time has put its magnificent signatures on the rocks of this fascinating valley and its surrounding environs.Right. from the fragments of the early crust to the artifacts of the Ahar Civilization are all well 

 preserved in this valley of Udaipur popularly known as "Girwa", The oldest rocks, perhaps, the remnants of the primordial crust, the Mewar Gneiss popularly known as the Banded Gneissic Complex with pockets of paleosols (that altered to fine'-grained, talcose white mica) form a flat terrain at the eastern entrance of the city: Basement rocks also crop out between Neemach Mata and Bari Lake and around Titari and Udai Sagar areas. At the foot hill side of Neemach Mata, the basement granite shows metasomatized remobilization making its contact with the cover rocks quite interesting. In fact, all these granitoid bodies were considered by earlier workers to be intrusive into the Aravalli rocks. Surprisingly, the boundaries of the amphitheater encircling the historic town form the replica of the epicontinental sea in which the sediments of the Aravalli Supergroup, divisible into Lower, Middle and Upper Groups, were deposited about two and a half billion years ago. The tWo high ridges, Iniamagara-Sajjangarh in the west and Debari in the east, that include two linear "outliers of Delhi Formations" (now considered part of the Aravalli Supergroup) and define the limits of the Udaipur valley; have emerged at the same place where the two deep seated liastric faults, that had develop during the beginning of the Aravalli basin formation, out poured basic lava. All along these ridges basic volcanic with vesicles and pillow structures are spread in the form of green schist that is noticeable east of Debari Zinc Smelter, Bari Lake and at the northern termination of Iniamagara. Sedimentation of Aravalli rocks began with dumping of large assorted blocks in the basic lava along the margins of the graben so formed. Diamictites of the Lower Aravalli Group so formed are exposed along the hills to the east of Debari Zinc Smelter, to the south of Nandeshwer and in a river section at Koriyat. Tuffaceous material associated with the lava can easily be seen displaying paper-thin laminations and micro grading along the Koriyat-Nai section. Around Koriyat the basal volcanics have been observed to be interlayer with carbonates. The basal sequence of coarse and fine clastics, represented by conglomerate, quartzite; phyllite is exposed on the either sides of Udaipur valley: Most of the high ridges around Koriyat, Bari, Nai and Undri on western side and Udai Sagar, Debari, and Girwa on the eastern and northern sides represent these lithounits. These linear outcrops of conglomerate-arkose-quartzite sequence, exposed on either sides of the Udaipur valley, were thought to be the "outliners" of Delhi "System" (now Supergroup) by earlier workers(Heron, 1953) .This interesting coarse clastic sequence to the east of Udaipur City, popularly known as Debari Formation, has seen several ups and downs during the history of geological research in the area. Banerjee ( 1971) , dividing the Aravalli rocks in to Debari, Maton, and Udaipur Formations, assigned it the lower most position in the sequence. On the other hand Roy and Paliwal ( 1981) equated this sequence with the greywacke-phyllite sequence of Udaipur Valley Formation-C. This sequence suffered a lot of oscillation in its stratigraphic position in subsequent publications. Similar sequence, popularly known as lniamagra sequence is exposed around Koriat, Bujara, Undari etc. to the west of Udaipur city has retained its basal status. Good exposures of the basal sequence are seen in sections along the road connecting Udaipur City with the Maharana Pratap Airport particularly around Debari tunnel and Zinc Smelter. The diamictite with large rounded boulders exposures are seen at Nandeswar on way to jharol, in river sections at Bujara, Sajjangarh and Koriyat and at Bari Lake where basic volcanics, now altered to green schist, show well preserved vesicular and amygdular structures. In a ridge west of Sajjangarh an outcrop of banded hematite quartzite has been noticed. The Basal sequence of coarse clastics passes upward into a carbonate sequence comprising dolomites, ortho-quartzite, stromatolitic phospharite and carbonaceous phyllite. Perhaps it was the time when the source area reached peneplanation and the weathering and erosional agencies calmed down. Chemicals started precipitating and carbonates got deposited in the epicontinental sea. Of course in deeper trenches, with reducing environment owing to profuse development of micro-organisms, black shale was deposited to give rise the carbonaceous phyllite. Uraniferrous carbonaceous phyllite has been located around Umra, hardly a few km, east of Udaipur. In a road cutting near Berwas (Pratapnagar) carbonaceous phyllite can be seen on way to Debari Zinc Smelter (where Zinc from Zawar group of mines, located about 50 km southeast of Udaipur, is smelted). Carbonate with algal stromatolites, both phosphatic and non-phosphatic, forms a marker horizon in the Aravalli Supergroup of rocks exposed in its type locality around Udaipur. In fact, blue-green algae grows profusely up to a depth of 30 meters ( a depth to which sunlight can penetrate) effectively for the photosynthesis. The prolific growth of the algae together with other microbiota gave rise to a large variety of algal stromatolite in carbonate(s) deposits encircling Udaipur valley, particularly around Sisarama, Neemach Mata, Bargaon, Kanpur, Kharbaria-Ka-Gurha, Maton, ]hamarkotra, and Dakankotra. At Jhamarkotra and Maton, hardly a few km west of Udaipur, the rock phosphate is being exploited commercially for fertilizer industry. Other prospects, of low-grade ore, may prove to be of economic significance in future. While enjoying boating in the Pichola Lake, phosphorite bearing carbonate hills of Sisarama can be viewed forming silhouette, which gives the Lake Palace a look of an iceberg with a smoky cloud in its background. Some geoscientists believe that rocks of the Udaipur area show a constant westerly younging and therefore the carbonates with phosphorite on either sides of the city form two separate stratigraphic horizons. Prolific development of blue-green algae in the epicontinenteal sea contributed a lot of oxygen to the atmosphere through photosynthesis through out the world. It is believed that our atmosphere lacked oxygen prior to the development of the blue-green algae in the seawater. A variety of stromatolites, the structures produced by these algae, are seen at a number of places around Udaipur City: In addition to a well preserved stromatolite park at the H-block of Jhamarkotra, these deformed and undeformed stromatolites