Karbi-Meghalaya plateau is in fact an extension of the main Indian peninsular plateau and are originally two different plateaues - Karbi Anglong Plateau and Meghalaya plateau.
Details
It is believed that due to the force exerted by the north-eastwardly movement of the Indian plate at the time of the Himalayan origin, a huge fault was created between the Rajmahal hills and the Karbi-Meghalaya plateau. Later, this depression was filled up by the depositional activity of numerous rivers. Today the Maghalaya and Karbi Anglong plateau remains detached from the main Peninsular block. This area receives maximum rainfall from the South-West monsoon.It is located in the north eastern plateau of India.
References
Karbi-Meghalaya plateau Wikipedia(Text) CC BY-SA