Rajasthan desert or Thar desert is the expanse of which of the following?

The Thar desert sits on a thick cover of Pleistocene and Recent (Holocene) deposits. These are mainly alluvium laid down by the Ghaggar-Hakra and other rivers, plus wind-blown aeolian sand that forms the dunes. The surface sediments are young and unconsolidated, which is why the landscape is sandy plains and dune fields spread across Rajasthan, parts of Gujarat, Punjab and Haryana.

• A) Pliocene: Pliocene rocks belong to the Neogene period (about 5.3 to 2.6 million years ago). They are older than the desert's surface cover and are not what the Thar is described as lying on.
• B) Paleocene: Paleocene is an early Palaeogene epoch (about 66 to 56 million years ago). It is far too old to form the desert's surface expanse.
• D) Oligocene: Oligocene is also Palaeogene (about 34 to 23 million years ago) and is not the surface deposit of the Thar.

Core concept: the Thar is a Quaternary landform shaped by fluvial and aeolian processes, and the same theme links to the geomorphology of the Indo-Gangetic plain and climate-change studies of the Ghaggar-Hakra palaeochannels for Mains.

Trap: aspirants see Tertiary formations in the Barmer and Jaisalmer basins and pick Pliocene or Oligocene. Those older rocks lie beneath the desert, while the expanse itself is Pleistocene and Recent.