• he peninsular plateau was one of the parts of the gondwana landmass which drifted away.
  
• Hence, it is the oldest landmass of the indian subcontinent. 
  
• Gondwana consists of Antarctica, South America, Africa, Madagaskar, and the Australia, as well as the Arabian Peninsula and the Indian Subcontinent, which have now moved entirely into the Northern Hemispher.So,the oldest landmass of Indian Subcontinent is Peninsular Plateau.