Session 1C: Inaugural Lectures by Fellows/Associates

Swagata Dasgupta

The mighty mylonites of the Bundelkhand craton: Clues to the basement rock selection of medieval forts in the Bundelkhand region, India

Globally, igneous provinces always provided stable basements for the construction of a diversity of palaces, castles, monuments, mausoleums, religious places, epitaphs, etc. The Heritage Stone Subcommission, under the aegis of the International Union of Geological Sciences (IUGS), identifies heritage stone resources from various continents to designate a stone as a Global Heritage Stone Resource (GHSR) based on certain parameters such as texture, mineralogical composition, colour and strength of the rocks. The Bundelkhand region is home to ~40 medieval forts built by different dynasties of north central India, as identified by the Archaeological Survey of India. The aesthetics, availability and cultural and religious sentiments related to these rocks probably made the choice for these rocks for construction of these ancient structures. While most of these forts built during the medieval period were constructed using various rocks/stones, the basements of these forts are often recognized as deformed mylonitized granitoids, which differentiate them from the surrounding undeformed to mildly deformed granitoids and/or quartz reefs in the craton. A few such examples include the Garh Kundar Fort (~925 AD) and Karera Fort (~1300 AD) built along the Raksa shear zone, a crustal-scale shear zone in the Bundelkhand craton. Notably, our ancestors might not have had formal training for the determination of the strength of the rocks over which they built forts or raised high structures until the 17th century, but they surely possessed scientific aptitude.