He was appointed as Assistant Superintendent (Geologist) in the superior service in the Geological Survey of India and joined the department in December 1924 [2] where Dr. Krishnan worked alongside Lewis Fermor, C. S. Fox, J.

After four years he was transferred to New Delhi as Mineral Adviser and Ex-Officio Joint Secretary to the Government of India (Ministry of Scientific Research) in August, 1955.

[2] He worked on stratigraphic mapping in Gangpur, Bonai, Bamra and Keonjar (parts of present Orissa State) and identified the 'Gangpur Series' published in GSI Memoir 71 (1937).

He also worked on minerals of economic importance including iron, manganese ores, gypsum, mica, limestone and published his studies in the GSI Memoir 80 (1952).

He also worked on the rocks of Girnar and the Osham hills of Saurashtra (now in Gujarat), lateritization of the peculiar metasedimentary rocks called khondalite, the mineral resources of former Central Provinces and Berar (now forming parts of Madhya Pradesh), the geology of the Vindhyan formations of northern India, the Deccan traps, the Tertiaries of Tanjore (Tamil Nadu), and made observations on mythical rivers such as the Indobrahm and Saraswathi.