The Aravalli Memoirs is the result of compilation and synthesis of the Precambrian lithostratigraphy, deformational events and structural data, magmatic cycles, mineral resources and geomorphology of the Aravalli region, in southern Rajasthan and north-eastern Gujarat–based on the acquisition of voluminous data collected till 1979 by the geoscientists of the Geological Survey of India. It covers an area of about 100,000 km2 and geological time span from 3.2. Ga to 0.7 Ga. Physiographically, the area can be grouped in three domains namely (i) the Western Sandy Plains (ii) the Aravalli Hill Ranges and (iii) the Eastern Plains. These divisions are based on the existing relief-features and provide a basis for the study of geomorphic evolution of the terrain, which has been sculptured through number of erosional cycles represented by various surfaces. Geomorphologically, the region is characterised by mature topography with more or less flat-topped mountain ridges, inselberg surfaces, intramontane valleys and vast stretches of plains. The Aravalli region forming the northwestern part of the Bundelkhand Craton represents a classic record of the Precambrian supracrustals. These supracrustals based on their tectonic setting, lithostratigraphy, deformational history, magmatic events, metamorphism and radiometric dating have been assigned to three geological cycles viz., the Bhilwara (> 2500 Ma), the Aravalli (2,500-2,000 Ma) and the Delhi (2000-700 Ma). The metasediments along with concordant and discordant intrusive and extrusive phases corresponding to these geological cycles, have been designated as the Bhilwara, the Aravalli and the Delhi Supergroups. These are further sub-divided into groups and formations as per the Code of stratigraphic nomenclature of India and have been named after the prominent villages/towns or cultural features to facilitate their description.
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